International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology.
Lasers and its application in periodonticsShilpa Shiv
The document discusses different types of lasers used in periodontology, including their properties, mechanisms of interaction with tissue, safety classifications, and clinical applications. It provides details on lasers such as the argon, diode, Nd:YAG, Er:YAG, and CO2 lasers, covering their wavelengths, active mediums, delivery systems, absorption characteristics, and periodontal uses. The document also examines laser tissue interactions, safety considerations, and the theoretical zones of tissue change caused by laser exposure.
Most excimer lasers used in ophthalmology emit ultraviolet light pulses between 4-25 nanoseconds at a wavelength of 193nm. The fluence ranges from 50-500 mJ/cm2, with 120-180 mJ/cm2 used for corneal ablation. Excimer lasers can deliver energy via broad beams, small flying spots, or variable spot sizes. Modern lasers often incorporate eye tracking to perform customized ablation patterns for refractive treatments like wavefront-guided procedures. Surgeons must understand their laser's capabilities and limitations to best utilize the technology for patient care.
This document discusses the various medical applications of lasers. It begins by explaining the key factors that determine how lasers interact with human tissue, including radiation, wavelength, and energy. It then outlines several specific uses of lasers in ophthalmology, neurosurgery, gastroenterology, dermatology, gynecology, ENT, and laser surgery more broadly. Lasers are used to treat retinal issues, seal blood vessels, weld tissues, remove fat, treat skin imperfections and cancers. The document also discusses the advantages of laser surgery like being painless and promoting fast healing, and the disadvantage of high cost. It concludes by providing details on optical fibers and how they transmit laser light through total internal reflection.
This document discusses the use of lasers in various medical fields such as dermatology, ophthalmology, dentistry, and gastroenterology. It explains that lasers can be used through four types of tissue interactions: photochemical, photothermal, photoablative, and photomechanical. Specific laser types and their applications in procedures like photocoagulation, photodisruption, and photorefractive keratectomy are outlined. The laser delivery systems of articulated arms, fiber optics, and waveguides are also summarized.
The document discusses the use of lasers in ophthalmology and refractive surgery. It describes different types of lasers including argon, diode, Nd:YAG, and excimer lasers. It explains how each laser is used for applications like retinal photocoagulation, iridotomy, trabeculoplasty, and refractive surgery procedures like PRK and LASIK. Key factors that determine laser tissue effects and goals of different laser treatments are also summarized.
Lasers have been used in ophthalmology since the 1960s, with early uses including retinal photocoagulation. The document discusses the history and types of lasers used, including solid state, gas, and semiconductor lasers. It also summarizes key diagnostic and therapeutic uses such as scanning laser ophthalmoscopy, optical coherence tomography, refractive surgery, glaucoma treatment, and capsulotomy. Lasers provide precise tissue effects through photocoagulation, photodisruption, photoablation, and photodynamic therapy, making them a valuable tool for modern eye care.
Lasers and its application in periodonticsShilpa Shiv
The document discusses different types of lasers used in periodontology, including their properties, mechanisms of interaction with tissue, safety classifications, and clinical applications. It provides details on lasers such as the argon, diode, Nd:YAG, Er:YAG, and CO2 lasers, covering their wavelengths, active mediums, delivery systems, absorption characteristics, and periodontal uses. The document also examines laser tissue interactions, safety considerations, and the theoretical zones of tissue change caused by laser exposure.
Most excimer lasers used in ophthalmology emit ultraviolet light pulses between 4-25 nanoseconds at a wavelength of 193nm. The fluence ranges from 50-500 mJ/cm2, with 120-180 mJ/cm2 used for corneal ablation. Excimer lasers can deliver energy via broad beams, small flying spots, or variable spot sizes. Modern lasers often incorporate eye tracking to perform customized ablation patterns for refractive treatments like wavefront-guided procedures. Surgeons must understand their laser's capabilities and limitations to best utilize the technology for patient care.
This document discusses the various medical applications of lasers. It begins by explaining the key factors that determine how lasers interact with human tissue, including radiation, wavelength, and energy. It then outlines several specific uses of lasers in ophthalmology, neurosurgery, gastroenterology, dermatology, gynecology, ENT, and laser surgery more broadly. Lasers are used to treat retinal issues, seal blood vessels, weld tissues, remove fat, treat skin imperfections and cancers. The document also discusses the advantages of laser surgery like being painless and promoting fast healing, and the disadvantage of high cost. It concludes by providing details on optical fibers and how they transmit laser light through total internal reflection.
This document discusses the use of lasers in various medical fields such as dermatology, ophthalmology, dentistry, and gastroenterology. It explains that lasers can be used through four types of tissue interactions: photochemical, photothermal, photoablative, and photomechanical. Specific laser types and their applications in procedures like photocoagulation, photodisruption, and photorefractive keratectomy are outlined. The laser delivery systems of articulated arms, fiber optics, and waveguides are also summarized.
The document discusses the use of lasers in ophthalmology and refractive surgery. It describes different types of lasers including argon, diode, Nd:YAG, and excimer lasers. It explains how each laser is used for applications like retinal photocoagulation, iridotomy, trabeculoplasty, and refractive surgery procedures like PRK and LASIK. Key factors that determine laser tissue effects and goals of different laser treatments are also summarized.
Lasers have been used in ophthalmology since the 1960s, with early uses including retinal photocoagulation. The document discusses the history and types of lasers used, including solid state, gas, and semiconductor lasers. It also summarizes key diagnostic and therapeutic uses such as scanning laser ophthalmoscopy, optical coherence tomography, refractive surgery, glaucoma treatment, and capsulotomy. Lasers provide precise tissue effects through photocoagulation, photodisruption, photoablation, and photodynamic therapy, making them a valuable tool for modern eye care.
Laser technology provides several benefits for prosthodontic and implant dentistry procedures. Lasers allow for precise soft and hard tissue incisions, coagulation to control bleeding, and reduction of postoperative pain and swelling. The erbium family of lasers can be used for soft tissue procedures as well as bone removal or contouring. This makes lasers useful for denture support surgery like vestibuloplasty and tuberosity reduction. Lasers also aid in second stage implant surgery by providing a dry, clean surgical site for immediate impressions. While many lasers can be used, erbium and carbon dioxide lasers interact minimally with dental implants.
Angstrom Advanced is the leading supplier for ellipsometers. We offer full range of ellipsometers for thin film thickness measurement and optical characterization for refractive index and extinction coefficient (n & k). The Angstrom Advanced ellipsometer family includes discrete wavelength ellipsometers (single wavelength ellipsometers and multi-wavelength ellipsometers), deep UV, UV, VIS, NIR and IR spectroscopic ellipsometers. Our ellipsometers have been delivered to many renowned universities, research institutes and companies worldwide. Angstrom Advanced's goal is to supply the most accurate and repeatable ellipsometers with the highest standard of customer satisfaction. Many upgrade accessories are available for different applications.
The document describes the design and development of a solar pumped Nd:YAG laser. It discusses using a Fresnel lens to focus sunlight onto a laser rod containing neodymium-doped yttrium aluminum garnet to optically pump the laser. The laser cavity and output coupler are also mentioned. Work done so far includes fabricating light guides, measuring focal length and spot size, and developing a cooling system. Simulations have been run to optimize positioning of the light guide and characterize loss mechanisms. The next steps are to place the laser rod in the cavity, align it, and attempt to achieve lasing output. Further optimization and characterization will follow if lasing is achieved.
This document discusses the definition, types, classes, and applications of lasers. It begins by defining lasers as light amplification by stimulated emission of radiation. It describes the three main types of lasers based on coherence and directionality: many wavelengths that are multidirectional and incoherent; monochromatic, directional, and coherent; and single wavelength, directional beams. It then covers the fundamentals of laser operation, types based on material used, classes based on biological damage caused, and typical emission wavelengths. Applications discussed include medicine, welding, cutting, surveying, communication, garment industry, data storage, holography, spectroscopy, heat treatment, barcoding, printing, cooling, and military uses.
Review of Lasers in Dentistry and Safety MeasuresIRJET Journal
This document reviews the use of lasers in dentistry and safety measures. It summarizes the main types of lasers used including CO2, Nd:YAG, diode, and discusses their applications such as caries removal, gum treatment, and teeth whitening. Lasers have advantages over traditional methods like less bleeding and minimal swelling. However, safety is an important concern as different lasers have varying tissue penetration and thermal effects. Proper training, safety equipment, and adherence to exposure limits are needed to ensure safe use of lasers in clinical procedures.
Lasers in dentistry/ orthodontic course by indian dental academyIndian dental academy
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
The document discusses Lumenis' LumeProbe product line of ophthalmic laser probes. It summarizes that the LumeProbes are designed to deliver laser energy safely and efficiently for retinal treatments, offering consistent laser spots and optimized energy transmission without the need for adapters. They provide reliability, a wide selection of probe types, and benefits for smaller gauge sizes.
This document provides information about laser safety for clinical staff. It defines what a laser is, discusses laser classifications from class 1 to 4 based on their hazard level, and describes the types of laser hazards including those for eyes, skin, and from electrical or fire sources. It provides details on laser signage, protective eyewear, key controls, and proper procedural practices like using laser checklists and smoke evacuators. The document also lists some common urological laser procedures and the laser devices and fibers used at the center.
The document provides an overview of lasers, including:
1. It defines what a laser is, describing the acronym LASER and how lasers emit a useful form of light energy.
2. It discusses the history and development of lasers, including milestones such as the first laser built in 1960 and early medical uses starting in 1963.
3. It describes the key principles and components of how lasers work, including stimulated emission, the pumping system, and optical cavity that contains the lasing medium.
This document discusses various applications of lasers including manufacturing, medical, metrology, defense, communication, and scientific uses. Lasers are widely used in manufacturing for cutting, drilling, welding, and lithography due to their ability to focus light into an intense beam. In medicine, lasers are used for eye surgery, dermatology, and minimally invasive surgery. Defense applications include laser range finders, underwater lasers, and laser-guided missiles. Lasers also have important applications in spectroscopy, laser cooling, optical tweezers, and as guide stars for telescopes. Future potential uses may include laser-based electricity generation and transmission as well as nuclear fusion.
Laser technology has many applications in ophthalmology. The first laser used was a ruby laser in 1960. Common lasers used include argon, Nd:YAG, and diode lasers which are selected based on their wavelength absorption properties. Lasers are used for procedures like posterior capsulotomy, retinal photocoagulation, glaucoma treatments like ALT and SLT, and laser peripheral iridotomies. The interaction of laser light with tissue can cause effects like photocoagulation, photodisruption, photoablation and photoactivation which underlie different clinical applications. Precise parameters are needed to achieve the desired effect safely and effectively for each procedure and laser type.
The document discusses lasers used in ophthalmology. It begins by defining what a laser is in terms of its acronym parts. It then covers laser physics including absorption, spontaneous emission, and stimulated emission. It describes different types of lasers used in ophthalmology like Nd:YAG, excimer, and diode lasers. Applications covered include treatments for glaucoma, cataracts, retinal diseases, and refractive errors. Mechanisms of laser tissue interaction like photocoagulation and photodisruption are also summarized.
This document discusses lasers used in dentistry. It begins with an introduction to lasers, then discusses the history of lasers in dentistry. It describes the main types of lasers used, including soft tissue lasers and hard tissue lasers. The document outlines the various uses of lasers in dentistry for procedures like hard tissue cutting, bone surgery, soft tissue surgery, root canals, and periodontics. It also discusses laser hazards, control measures, and the importance of infection control and personal protective equipment when using lasers.
Laser therapy uses focused beams of light to precisely cut, burn, or destroy tissue for medical purposes. Common applications include removing tumors, sealing blood vessels to prevent bleeding, and performing eye surgeries like cataract removal and refractive procedures to correct vision. The document discusses the history and types of lasers and laser eye surgeries, including LASIK, PRK, and LASEK procedures used to treat conditions like nearsightedness, farsightedness, and astigmatism.
Laser Processing of Different materials and its application.aman1312
Presentation of laser application in different types of industry for material processing. Laser materials processing is done on various materials such as metals, non metals, ceramics, polymer materials.
The document discusses the history and applications of lasers. It begins with a brief history of lasers, noting they were developed in the 1960s and have since revolutionized optics. It defines lasers as devices that generate light via stimulated emission. One example application is using lasers as the light source for fiber optic communication, allowing information to be transmitted quickly through glass fibers. The document outlines several other applications of lasers, including uses in the military, medicine, communication, and materials processing.
The document discusses the history and uses of lasers in orthodontics. It begins by contrasting how lasers were once seen as weapons of destruction in science fiction but are now used for many purposes including medical and dental applications. It provides details on the types of lasers, how they work, their interactions with tissues, and effects. The document discusses factors to consider when selecting the appropriate laser for different orthodontic procedures.
The document summarizes different types of lasers used in oral and maxillofacial surgery (OMFS). It discusses the historical background and components of lasers. The most commonly used lasers in dentistry are carbon dioxide lasers, erbium lasers, argon lasers, Nd:YAG lasers, KTP lasers, and diode lasers. Each laser type is characterized by its active medium and wavelength, which determine its absorption in different tissues and clinical applications.
1. This document discusses laser illumination events and the risks lasers pose to aircraft and pilots. It provides statistics on laser incidents aimed at aircraft from 2012.
2. The document outlines the risks of lasers to vision, including potential eye damage depending on the laser's wavelength and power. Studies with pilots in flight simulators showed lasers can be distracting, cause glare, and flash blindness.
3. The document recommends safety measures like designating laser-free zones around airports, following aviation laser safety standards, requiring laser incident reporting, and providing protective eyewear in aircraft.
This document summarizes laser safety hazards and standards. It describes the potential eye, skin, electrical, and other hazards from laser radiation and systems. It also outlines the ANSI laser hazard classification system which categorizes lasers into four classes based on their potential to cause injury, with Class 1 being safest and Class 4 being most hazardous. Control measures are specified for each class to ensure safe use.
Laser technology provides several benefits for prosthodontic and implant dentistry procedures. Lasers allow for precise soft and hard tissue incisions, coagulation to control bleeding, and reduction of postoperative pain and swelling. The erbium family of lasers can be used for soft tissue procedures as well as bone removal or contouring. This makes lasers useful for denture support surgery like vestibuloplasty and tuberosity reduction. Lasers also aid in second stage implant surgery by providing a dry, clean surgical site for immediate impressions. While many lasers can be used, erbium and carbon dioxide lasers interact minimally with dental implants.
Angstrom Advanced is the leading supplier for ellipsometers. We offer full range of ellipsometers for thin film thickness measurement and optical characterization for refractive index and extinction coefficient (n & k). The Angstrom Advanced ellipsometer family includes discrete wavelength ellipsometers (single wavelength ellipsometers and multi-wavelength ellipsometers), deep UV, UV, VIS, NIR and IR spectroscopic ellipsometers. Our ellipsometers have been delivered to many renowned universities, research institutes and companies worldwide. Angstrom Advanced's goal is to supply the most accurate and repeatable ellipsometers with the highest standard of customer satisfaction. Many upgrade accessories are available for different applications.
The document describes the design and development of a solar pumped Nd:YAG laser. It discusses using a Fresnel lens to focus sunlight onto a laser rod containing neodymium-doped yttrium aluminum garnet to optically pump the laser. The laser cavity and output coupler are also mentioned. Work done so far includes fabricating light guides, measuring focal length and spot size, and developing a cooling system. Simulations have been run to optimize positioning of the light guide and characterize loss mechanisms. The next steps are to place the laser rod in the cavity, align it, and attempt to achieve lasing output. Further optimization and characterization will follow if lasing is achieved.
This document discusses the definition, types, classes, and applications of lasers. It begins by defining lasers as light amplification by stimulated emission of radiation. It describes the three main types of lasers based on coherence and directionality: many wavelengths that are multidirectional and incoherent; monochromatic, directional, and coherent; and single wavelength, directional beams. It then covers the fundamentals of laser operation, types based on material used, classes based on biological damage caused, and typical emission wavelengths. Applications discussed include medicine, welding, cutting, surveying, communication, garment industry, data storage, holography, spectroscopy, heat treatment, barcoding, printing, cooling, and military uses.
Review of Lasers in Dentistry and Safety MeasuresIRJET Journal
This document reviews the use of lasers in dentistry and safety measures. It summarizes the main types of lasers used including CO2, Nd:YAG, diode, and discusses their applications such as caries removal, gum treatment, and teeth whitening. Lasers have advantages over traditional methods like less bleeding and minimal swelling. However, safety is an important concern as different lasers have varying tissue penetration and thermal effects. Proper training, safety equipment, and adherence to exposure limits are needed to ensure safe use of lasers in clinical procedures.
Lasers in dentistry/ orthodontic course by indian dental academyIndian dental academy
Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.
The document discusses Lumenis' LumeProbe product line of ophthalmic laser probes. It summarizes that the LumeProbes are designed to deliver laser energy safely and efficiently for retinal treatments, offering consistent laser spots and optimized energy transmission without the need for adapters. They provide reliability, a wide selection of probe types, and benefits for smaller gauge sizes.
This document provides information about laser safety for clinical staff. It defines what a laser is, discusses laser classifications from class 1 to 4 based on their hazard level, and describes the types of laser hazards including those for eyes, skin, and from electrical or fire sources. It provides details on laser signage, protective eyewear, key controls, and proper procedural practices like using laser checklists and smoke evacuators. The document also lists some common urological laser procedures and the laser devices and fibers used at the center.
The document provides an overview of lasers, including:
1. It defines what a laser is, describing the acronym LASER and how lasers emit a useful form of light energy.
2. It discusses the history and development of lasers, including milestones such as the first laser built in 1960 and early medical uses starting in 1963.
3. It describes the key principles and components of how lasers work, including stimulated emission, the pumping system, and optical cavity that contains the lasing medium.
This document discusses various applications of lasers including manufacturing, medical, metrology, defense, communication, and scientific uses. Lasers are widely used in manufacturing for cutting, drilling, welding, and lithography due to their ability to focus light into an intense beam. In medicine, lasers are used for eye surgery, dermatology, and minimally invasive surgery. Defense applications include laser range finders, underwater lasers, and laser-guided missiles. Lasers also have important applications in spectroscopy, laser cooling, optical tweezers, and as guide stars for telescopes. Future potential uses may include laser-based electricity generation and transmission as well as nuclear fusion.
Laser technology has many applications in ophthalmology. The first laser used was a ruby laser in 1960. Common lasers used include argon, Nd:YAG, and diode lasers which are selected based on their wavelength absorption properties. Lasers are used for procedures like posterior capsulotomy, retinal photocoagulation, glaucoma treatments like ALT and SLT, and laser peripheral iridotomies. The interaction of laser light with tissue can cause effects like photocoagulation, photodisruption, photoablation and photoactivation which underlie different clinical applications. Precise parameters are needed to achieve the desired effect safely and effectively for each procedure and laser type.
The document discusses lasers used in ophthalmology. It begins by defining what a laser is in terms of its acronym parts. It then covers laser physics including absorption, spontaneous emission, and stimulated emission. It describes different types of lasers used in ophthalmology like Nd:YAG, excimer, and diode lasers. Applications covered include treatments for glaucoma, cataracts, retinal diseases, and refractive errors. Mechanisms of laser tissue interaction like photocoagulation and photodisruption are also summarized.
This document discusses lasers used in dentistry. It begins with an introduction to lasers, then discusses the history of lasers in dentistry. It describes the main types of lasers used, including soft tissue lasers and hard tissue lasers. The document outlines the various uses of lasers in dentistry for procedures like hard tissue cutting, bone surgery, soft tissue surgery, root canals, and periodontics. It also discusses laser hazards, control measures, and the importance of infection control and personal protective equipment when using lasers.
Laser therapy uses focused beams of light to precisely cut, burn, or destroy tissue for medical purposes. Common applications include removing tumors, sealing blood vessels to prevent bleeding, and performing eye surgeries like cataract removal and refractive procedures to correct vision. The document discusses the history and types of lasers and laser eye surgeries, including LASIK, PRK, and LASEK procedures used to treat conditions like nearsightedness, farsightedness, and astigmatism.
Laser Processing of Different materials and its application.aman1312
Presentation of laser application in different types of industry for material processing. Laser materials processing is done on various materials such as metals, non metals, ceramics, polymer materials.
The document discusses the history and applications of lasers. It begins with a brief history of lasers, noting they were developed in the 1960s and have since revolutionized optics. It defines lasers as devices that generate light via stimulated emission. One example application is using lasers as the light source for fiber optic communication, allowing information to be transmitted quickly through glass fibers. The document outlines several other applications of lasers, including uses in the military, medicine, communication, and materials processing.
The document discusses the history and uses of lasers in orthodontics. It begins by contrasting how lasers were once seen as weapons of destruction in science fiction but are now used for many purposes including medical and dental applications. It provides details on the types of lasers, how they work, their interactions with tissues, and effects. The document discusses factors to consider when selecting the appropriate laser for different orthodontic procedures.
The document summarizes different types of lasers used in oral and maxillofacial surgery (OMFS). It discusses the historical background and components of lasers. The most commonly used lasers in dentistry are carbon dioxide lasers, erbium lasers, argon lasers, Nd:YAG lasers, KTP lasers, and diode lasers. Each laser type is characterized by its active medium and wavelength, which determine its absorption in different tissues and clinical applications.
1. This document discusses laser illumination events and the risks lasers pose to aircraft and pilots. It provides statistics on laser incidents aimed at aircraft from 2012.
2. The document outlines the risks of lasers to vision, including potential eye damage depending on the laser's wavelength and power. Studies with pilots in flight simulators showed lasers can be distracting, cause glare, and flash blindness.
3. The document recommends safety measures like designating laser-free zones around airports, following aviation laser safety standards, requiring laser incident reporting, and providing protective eyewear in aircraft.
This document summarizes laser safety hazards and standards. It describes the potential eye, skin, electrical, and other hazards from laser radiation and systems. It also outlines the ANSI laser hazard classification system which categorizes lasers into four classes based on their potential to cause injury, with Class 1 being safest and Class 4 being most hazardous. Control measures are specified for each class to ensure safe use.
The document provides an overview of laser safety fundamentals including:
- The properties that make laser light hazardous including being monochromatic, coherent, and highly directional.
- Common laser types categorized by wavelength output.
- Laser output characteristics such as continuous wave vs pulsed output.
- Types of laser hazards including those to the eye, skin, and from electrical and chemical sources.
- Symptoms of laser eye injuries and classifications of lasers based on their hazard potential outlined in safety standards.
- Control measures like engineering controls, administrative procedures, and personal protective equipment including laser safety eyewear.
Radiation safety and protection for dental radiographyNitin Sharma
1) Licensed dentists must maintain radiation exposures as low as reasonably achievable and understand the health risks of radiation.
2) Dental radiographic equipment must be registered and follow safety protocols to protect patients and staff, such as using protective gear and collimation.
3) Dentists are responsible for quality assurance programs to ensure proper functioning and calibration of dental X-ray machines and processing of films. Guidelines help prescribe radiographs appropriately.
femtosecond laser in ophthalmology by Dr. Hind Safwat (Al Azhr university) Hind Safwat
Here are the key points about FSL in penetrating keratoplasty:
- FSL allows for precise, consistent cuts that minimize damage to surrounding tissue.
- It can create wound configurations that provide more surface area for healing, improve tissue alignment, require less suture tension, and have superior biomechanical strength.
- Advantages include rapid visual recovery, less astigmatism, and benefits specific to the type of cut (lamellar vs penetrating).
- Contraindications include conditions preventing proper docking of the laser such as severe ocular surface irregularities or recent perforations.
Principle of Radiation Protection- Avinesh ShresthaAvinesh Shrestha
Radiation protection is the science whose aim is to minimize the risks generated by the use of ionizing radiation. Briefly discusses The ICRP System of Radiological Protection, STRUCTURAL SHIELDING OF
IMAGING FACILITIES, APPLICATION OF INDIVIDUAL DOSE LIMTS, RADIATION EXPOSURE IN PREGNANCY, Diagnostic reference level, Personnel Protection in
Medical X-ray Imaging, Dose Optimization in CT, Radiation Protection in Nuclear Medicine.
Radiation protection involves protecting people from harmful effects of ionizing radiation. There are three types of radiation: primary radiation which is most intense; scattered radiation resulting from the Compton effect; and leakage radiation emitted from x-ray equipment. The three cardinal principles of radiation protection are time, distance, and shielding. The system of radiation protection justifies practices where benefits outweigh risks, uses ALARA to keep doses as low as reasonably achievable, and limits doses to individuals. Radiation can cause stochastic or non-stochastic effects depending on dose thresholds. Exposure includes medical exposure to patients, occupational exposure to workers, and public exposure. Radiation is monitored through personnel and workplace monitoring devices. Radiation facilities use controlled and
Lasers in oral and maxillofacial surgery .pptxwanidayim1
This document provides an overview of lasers, including their components, mechanism of action, classification, safety, advantages, complications, and clinical applications in dentistry. Lasers work by generating a population inversion in which excited atoms or molecules emit photons that are amplified within the laser's optical cavity to produce a coherent beam of light. The main types used in dentistry are CO2, Nd:YAG, and diode lasers, which can be used for procedures like gingivectomies, frenectomies, and removing vascular or benign/malignant lesions. Lasers offer advantages like increased coagulation and less pain/swelling compared to conventional techniques. Risks include potential eye/tooth injuries if safety
An Update on Safety Measures in Laser Dentistryiosrjce
IOSR Journal of Dental and Medical Sciences is one of the speciality Journal in Dental Science and Medical Science published by International Organization of Scientific Research (IOSR). The Journal publishes papers of the highest scientific merit and widest possible scope work in all areas related to medical and dental science. The Journal welcome review articles, leading medical and clinical research articles, technical notes, case reports and others.
7-RADIATION PROTECTION IN DENTISTRY===7=2023.pdfNASERALHAQ
This document discusses principles of radiation protection in dentistry. It provides guidelines for optimal settings and equipment for various dental radiographic techniques to minimize radiation exposure, including recommending a kilovoltage of 60-70 kV for intraoral radiography. Digital image receptors require half the exposure time of film but can have more retakes. Reduction of field of view size is the most important strategy for optimizing cone-beam CT scans to reduce effective radiation dose.
Lasers have many applications in operative dentistry including caries detection, cavity preparation, prevention of dental caries, bleaching, and photopolymerization of composite resin. Different types of lasers like Er:YAG, CO2, and diode lasers can be used safely for hard and soft tissue procedures with benefits like minimal damage, hemostasis, reduced post-operative pain and inflammation, and sterilization of wounds. While lasers provide advantages, training is required for their safe use and they can be costly to obtain.
This document provides an overview of laser safety fundamentals. It discusses the properties that make laser light hazardous, including being monochromatic, directional, and coherent. It also covers common laser components, lasing action, laser output types, hazards like those to the eyes and skin, and classifications. Control measures like engineering controls, PPE, and laser protective eyewear are explained. Key terms like MPE and NHZ are defined.
Detection of Brain Tumor below 3mm Using NIR Sensor IRJET Journal
This document describes a proposed method to detect brain tumors below 3mm in size using near-infrared imaging techniques. The current methods like MRI, CT, and microwave imaging cannot detect tumors that small. The proposed method uses near-infrared light with a wavelength of 780nm transmitted into the brain via an LED and detected with a photodetector. Signal processing techniques like short-time Fourier transform and Lagrangian support vector machines would be used to analyze the signals and detect any tumors present. An experiment using this method on a brain phantom successfully detected an artificial tumor, demonstrating the potential of this near-infrared imaging approach.
Lasers and its role in endodontics/certified fixed orthodontic courses by Ind...Indian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.
Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078
Radiation protection and personnel monitoring devicesRubiSapkota
This document discusses radiation protection and personnel monitoring devices. It begins with an introduction to radiation and the electromagnetic spectrum. It then covers the effects of radiation, principles of radiation protection including justification of practice, optimization of protection, and dose limits. The document discusses various personnel monitoring devices including film badges, thermoluminescence dosimeters (TLD), and optically stimulated luminescence dosimeters. It provides details on how each device works and their advantages and disadvantages.
In the modern age, High-resolution radar images can be achieved by employing SAR technique. It is well
known that SAR can provide several times better image resolution than conventional radars. The exploration for efficient
image denoising methods still remains a valid challenge for researchers. Despite the difficulty of the recently proposed
methods, mostly of the algorithms have not yet attained a pleasing level of applicability; each algorithm has its
assumptions, advantages, and limitations. This paper presents a review of synthetic aperture radar. Behind a brief
introduction in our work we are especially targeting the noise called backscattered noise in SAR terminology which
causes the appearance of speckle Potential future work in the area of air flight navigation, mapping Weather Monitoring
& during natural disaster like earth quake. The SAR having the capability, to make human visibility beyond optical
vision, is also discussed.
Low level laser therapy uses low-powered lasers to stimulate healing. It can be used to treat wounds, pain, and other conditions.
There are two main types - high-powered "hot" lasers that use thermal effects, and low-powered lasers that produce no heat. Low-powered lasers are classified by safety class and can be He-Ne or Ga-As lasers.
Laser therapy stimulates healing through biostimulation effects. It may increase cell proliferation, collagen production, and phagocytosis. Studies show it can help reduce pain, promote fracture healing, and improve wound healing outcomes. Parameters like dosage, wavelength, and application technique are important to achieve therapeutic effects.
This presentation covers basic laser safety. It discusses laser bioeffects such as damage to the eyes and skin. It describes laser hazards including reflective objects and accidental beam exposure. Laser classes are defined from Class 1 being safe to Class 4 being high power and a severe eye and skin hazard. Facility requirements include exposure limits, hazard zone markings, interlocks and protective equipment. A laser safety program requires engineering and administrative controls, training, permits and oversight by a Laser Safety Officer.
A laser works by stimulating the emission of photons from excited atoms or molecules in a lasing medium placed within an optical cavity formed by mirrors. When photons strike excited atoms, they cause the atoms to release more photons of the same frequency, phase, and direction, producing a coherent beam of light through stimulated emission. Population inversion is needed, where more atoms are in an excited state than a ground state. Lasers have applications in medicine, communications, manufacturing, and research due to their coherence, directionality, monochromaticity, and high intensity.
Similar to International Journal of Computational Engineering Research(IJCER) (20)
Skybuffer SAM4U tool for SAP license adoptionTatiana Kojar
Manage and optimize your license adoption and consumption with SAM4U, an SAP free customer software asset management tool.
SAM4U, an SAP complimentary software asset management tool for customers, delivers a detailed and well-structured overview of license inventory and usage with a user-friendly interface. We offer a hosted, cost-effective, and performance-optimized SAM4U setup in the Skybuffer Cloud environment. You retain ownership of the system and data, while we manage the ABAP 7.58 infrastructure, ensuring fixed Total Cost of Ownership (TCO) and exceptional services through the SAP Fiori interface.
Driving Business Innovation: Latest Generative AI Advancements & Success StorySafe Software
Are you ready to revolutionize how you handle data? Join us for a webinar where we’ll bring you up to speed with the latest advancements in Generative AI technology and discover how leveraging FME with tools from giants like Google Gemini, Amazon, and Microsoft OpenAI can supercharge your workflow efficiency.
During the hour, we’ll take you through:
Guest Speaker Segment with Hannah Barrington: Dive into the world of dynamic real estate marketing with Hannah, the Marketing Manager at Workspace Group. Hear firsthand how their team generates engaging descriptions for thousands of office units by integrating diverse data sources—from PDF floorplans to web pages—using FME transformers, like OpenAIVisionConnector and AnthropicVisionConnector. This use case will show you how GenAI can streamline content creation for marketing across the board.
Ollama Use Case: Learn how Scenario Specialist Dmitri Bagh has utilized Ollama within FME to input data, create custom models, and enhance security protocols. This segment will include demos to illustrate the full capabilities of FME in AI-driven processes.
Custom AI Models: Discover how to leverage FME to build personalized AI models using your data. Whether it’s populating a model with local data for added security or integrating public AI tools, find out how FME facilitates a versatile and secure approach to AI.
We’ll wrap up with a live Q&A session where you can engage with our experts on your specific use cases, and learn more about optimizing your data workflows with AI.
This webinar is ideal for professionals seeking to harness the power of AI within their data management systems while ensuring high levels of customization and security. Whether you're a novice or an expert, gain actionable insights and strategies to elevate your data processes. Join us to see how FME and AI can revolutionize how you work with data!
Discover top-tier mobile app development services, offering innovative solutions for iOS and Android. Enhance your business with custom, user-friendly mobile applications.
Main news related to the CCS TSI 2023 (2023/1695)Jakub Marek
An English 🇬🇧 translation of a presentation to the speech I gave about the main changes brought by CCS TSI 2023 at the biggest Czech conference on Communications and signalling systems on Railways, which was held in Clarion Hotel Olomouc from 7th to 9th November 2023 (konferenceszt.cz). Attended by around 500 participants and 200 on-line followers.
The original Czech 🇨🇿 version of the presentation can be found here: https://www.slideshare.net/slideshow/hlavni-novinky-souvisejici-s-ccs-tsi-2023-2023-1695/269688092 .
The videorecording (in Czech) from the presentation is available here: https://youtu.be/WzjJWm4IyPk?si=SImb06tuXGb30BEH .
5th LF Energy Power Grid Model Meet-up SlidesDanBrown980551
5th Power Grid Model Meet-up
It is with great pleasure that we extend to you an invitation to the 5th Power Grid Model Meet-up, scheduled for 6th June 2024. This event will adopt a hybrid format, allowing participants to join us either through an online Mircosoft Teams session or in person at TU/e located at Den Dolech 2, Eindhoven, Netherlands. The meet-up will be hosted by Eindhoven University of Technology (TU/e), a research university specializing in engineering science & technology.
Power Grid Model
The global energy transition is placing new and unprecedented demands on Distribution System Operators (DSOs). Alongside upgrades to grid capacity, processes such as digitization, capacity optimization, and congestion management are becoming vital for delivering reliable services.
Power Grid Model is an open source project from Linux Foundation Energy and provides a calculation engine that is increasingly essential for DSOs. It offers a standards-based foundation enabling real-time power systems analysis, simulations of electrical power grids, and sophisticated what-if analysis. In addition, it enables in-depth studies and analysis of the electrical power grid’s behavior and performance. This comprehensive model incorporates essential factors such as power generation capacity, electrical losses, voltage levels, power flows, and system stability.
Power Grid Model is currently being applied in a wide variety of use cases, including grid planning, expansion, reliability, and congestion studies. It can also help in analyzing the impact of renewable energy integration, assessing the effects of disturbances or faults, and developing strategies for grid control and optimization.
What to expect
For the upcoming meetup we are organizing, we have an exciting lineup of activities planned:
-Insightful presentations covering two practical applications of the Power Grid Model.
-An update on the latest advancements in Power Grid -Model technology during the first and second quarters of 2024.
-An interactive brainstorming session to discuss and propose new feature requests.
-An opportunity to connect with fellow Power Grid Model enthusiasts and users.
Northern Engraving | Nameplate Manufacturing Process - 2024Northern Engraving
Manufacturing custom quality metal nameplates and badges involves several standard operations. Processes include sheet prep, lithography, screening, coating, punch press and inspection. All decoration is completed in the flat sheet with adhesive and tooling operations following. The possibilities for creating unique durable nameplates are endless. How will you create your brand identity? We can help!
How information systems are built or acquired puts information, which is what they should be about, in a secondary place. Our language adapted accordingly, and we no longer talk about information systems but applications. Applications evolved in a way to break data into diverse fragments, tightly coupled with applications and expensive to integrate. The result is technical debt, which is re-paid by taking even bigger "loans", resulting in an ever-increasing technical debt. Software engineering and procurement practices work in sync with market forces to maintain this trend. This talk demonstrates how natural this situation is. The question is: can something be done to reverse the trend?
Fueling AI with Great Data with Airbyte WebinarZilliz
This talk will focus on how to collect data from a variety of sources, leveraging this data for RAG and other GenAI use cases, and finally charting your course to productionalization.
Programming Foundation Models with DSPy - Meetup SlidesZilliz
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Digital Banking in the Cloud: How Citizens Bank Unlocked Their MainframePrecisely
Inconsistent user experience and siloed data, high costs, and changing customer expectations – Citizens Bank was experiencing these challenges while it was attempting to deliver a superior digital banking experience for its clients. Its core banking applications run on the mainframe and Citizens was using legacy utilities to get the critical mainframe data to feed customer-facing channels, like call centers, web, and mobile. Ultimately, this led to higher operating costs (MIPS), delayed response times, and longer time to market.
Ever-changing customer expectations demand more modern digital experiences, and the bank needed to find a solution that could provide real-time data to its customer channels with low latency and operating costs. Join this session to learn how Citizens is leveraging Precisely to replicate mainframe data to its customer channels and deliver on their “modern digital bank” experiences.
Dandelion Hashtable: beyond billion requests per second on a commodity serverAntonios Katsarakis
This slide deck presents DLHT, a concurrent in-memory hashtable. Despite efforts to optimize hashtables, that go as far as sacrificing core functionality, state-of-the-art designs still incur multiple memory accesses per request and block request processing in three cases. First, most hashtables block while waiting for data to be retrieved from memory. Second, open-addressing designs, which represent the current state-of-the-art, either cannot free index slots on deletes or must block all requests to do so. Third, index resizes block every request until all objects are copied to the new index. Defying folklore wisdom, DLHT forgoes open-addressing and adopts a fully-featured and memory-aware closed-addressing design based on bounded cache-line-chaining. This design offers lock-free index operations and deletes that free slots instantly, (2) completes most requests with a single memory access, (3) utilizes software prefetching to hide memory latencies, and (4) employs a novel non-blocking and parallel resizing. In a commodity server and a memory-resident workload, DLHT surpasses 1.6B requests per second and provides 3.5x (12x) the throughput of the state-of-the-art closed-addressing (open-addressing) resizable hashtable on Gets (Deletes).
Dandelion Hashtable: beyond billion requests per second on a commodity server
International Journal of Computational Engineering Research(IJCER)
1. International Journal of Computational Engineering Research||Vol, 03||Issue, 6||
www.ijceronline.com ||June ||2013|| Page 86
Eye Safe Laser Using Optical Parametric Oscillation
1,
Kireet Semwal , 2,
S. C. Bhatt
1,
Applied Science Department, GB Pant Engineering College, Pauri (Garhwal)-246194, Uttarakhand, India
2,
Department of Physics, HNB Garhwal Central University Srinagar (Garhwal)-246174, Uttarakhand, India
I. INTRODUCTION:
Laser application have proliferate in recent years and, as to be expected, their presence is no longer
confined to the laboratory or places where access to their radiation can be controlled. Military operations are
obvious applications where various devices such as laser range finders, target designators, and secure
communications equipment elevate the risk of exposure, specifically eye exposure, to unacceptable levels. It is
found that laser with operating wavelengths in the region of approximately 0.4 µm to 1.4 µm (i.e. visible and
near infrared) is the eye hazardous portion of optical spectrum, because in this region it is transmitted by the
cornea and the lens serves to focus the laser beam on the retina. Thus, the actual laser power density entering the
eye can be increased by some 105
by the time the light gets to the retina, and burn it without any time lag. This
hazardous wavelength region often called ocular focus region [1]. Whereas wavelengths beyond this region
are absorbed in the cornea, lens, and vitreous humor of eye, and therefore laser cannot make direct impact on the
retina. In this region our eye is relatively safe, and there is only thermal injury to eye. Therefore retinal damage
is often more severe than corneal damage. The hazards from the laser vary with the wavelength, intensity, and
duration of the output or length of exposure and it is difficult to generalize. However, operating procedures and
precautions can be specified over the various ranges of outputs of available lasers. Lasers present potential
safety hazards but can usually be guarded against with a few simple precautions [2].The effect of exposure to
high power or prolonged exposure at low power over the region 0.4 µm to 1.4 µm where the front part of the eye
is transparent, may be to damage the retina tissue and in particular the pigment epithelium, causing lesions and
leading to permanent blindness. Additional damage may also occur due to absorption in the cornea and
surrounding areas [3].
FIGURE 1. a) Construction of eye and eye injury by laser b) Eye transmission and absorption
ABSTRACT
It is found that laser with operating wavelengths in the region of approximately 0.4 µm to 1.4
µm (i.e. visible and near infrared) is the eye hazardous portion of optical spectrum, because in this
region it is transmitted by the cornea and the lens serves to focus the laser beam on the retina. Thus,
the actual laser power density entering the eye can be increased by some 105
by the time the light gets
to the retina, and burn it without any time lag. This hazardous wavelength region often called ocular
focus region. Whereas wavelengths beyond this region are absorbed in the cornea, lens, and vitreous
humor of eye, and therefore laser cannot make direct impact on the retina. In this region our eye is
relatively safe, and there is only thermal injury to eye. Therefore retinal damage is often more severe
than corneal damage. Eye damage may not only result from laser light coming directly from the laser,
but may also by light coming from secondary light path i.e. reflection, refraction, scattering etc. For
extremely high-power laser, even diffuse reflections may be capable of causing eye damage.
KEYWORDS: Eye safe laser, MPE for Eye, Optical Parametric Oscillator, KTP crystal.
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Maximum Permissible values of Exposure
The effect of pulsed lasers is dependent on the intensity and duration of the pulse. For the same energy
output the hazards due to Q-switched or mode-locked lasers are generally greater than pulsed outputs at the
same energy output. Maximum permissible values of exposure (MPE) based on damage to the retina derived
from measurements of damage over the visible region, are given in table-1 for cw laser and in table-2 for pulsed
laser [4][5][6]. The corresponding maximum permissible exposure levels at the cornea in table-2 are derived
from table-1 by multiplying the values by 5×105
based on the relaxed eye over the visible range. Where a series
of repetitive pulses are used the peak pulse energy and the continuous energy levels should not be exceeded.
TABLE 1. Ocular MPE Values for cw Laser
Laser Type Wavelength
(µm)
MPE
(watt/cm2
)
Exposure
duration (sec)
He:Cd 0.4416 2.5 × 10-3
0.25
Argon 0.4880, 0.5145 10-6
> 104
HeNe 0.632 2.5 × 10-3
0.25
HeNe 0.632 1 × 10-3
10
HeNe 0.632 17 × 10-6
> 104
Krypton 0.647 2.5 × 10-3
0.25
Krypton 0.647 1 × 10-3
10
Krypton 0.647 28 × 10-6
> 104
InGaAlP 0.670 2.5 × 10-3
0.25
GaAs 0.905 0.8 × 10-3
> 1000
Nd:YAG 1.064 1.6 × 10-3
> 1000
InGaAsP 1.310 12.8 × 10-3
> 1000
InGaAsP 1.55 0.1 > 10
CO2 10.6 0.1 > 10
TABLE 2. Ocular MPE Values for Pulsed Laser
Laser Type Wavelength (µm) Pulse length (sec) MPE (J/cm2
)
ArF 0.193 2 × 10-8
3 × 10-3
KrF 0.248 2 × 10-8
3 × 10-3
XeCl 0.308 2 × 10-8
6.7 × 10-3
XeF 0.351 2 × 10-8
6.7 × 10-3
Ruby (free-running) 0.6943 1 × 10-3
1 × 10-5
Ruby (Q-switched) 0.6943 5-100 × 10-9
5 × 10-7
Rhodamine 6G 0.500-0.700 5-18 × 10-6
5 × 10-7
Nd:YAG (free-running) 1.064 1 × 10-3
5 × 10-5
Nd:YAG (Q-switched) 1.064 5-100 × 10-9
5 × 10-6
CO2 10.6 1 × 10-3
100 × 10-7
Below about 0.4m and above about 1.4m damage to the cornea is the principal hazard. Since focusing
at the retina does not take place the threshold levels can be considerably relaxed; however, little available data
exists on threshold values outside the visible region. Outside the visible light region below a wavelength of
about 0.4m the safe exposure level recommended by BS4803 (British Standard) should not exceed 130 J/m2
per day, or 2.16 W/m2
for 1 minute, or a corresponding higher density over a shorter period. At infrared
wavelengths above about 1.4 m the maximum density from a single pulse should be limited to 1kJ/m2
and for
continuous exposure the average level should be limited to 500 W/m2
[5].
II. LASER EYE SAFETY:
The recommended eye protection for all people who work with lasers is a pair of goggles that are highly
absorbing in the spectral region of the laser. Now this is rather simple for any UV to IR laser, as humans cannot
see in these spectral ranges. However, it becomes much more difficult for visible lasers because the glasses that
protect the user may also reduce the user’s ability to see in the visible spectrum. According to Kuhn [1], the
laser safety goggles are characterized by a minimum safe optical density D defined as
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Where Hp is the power density (or energy density) of the incident laser beam and MPE is the maximum
permissible eye exposure (same unit as Hp)[3][6].
FIGURE 2. Laser Safety Eyewear and Warning Signs
It is essential that everybody concerned with the operation or use of lasers should have knowledge of
their potential hazards and the safety procedures involved. A safety officer should be appointed, who should be
responsible for records and safety procedures, and for liaising with the medical authorities undertaking
surveillance. The safety officer should ideally be one of the operating personnel because of the highly specialist
nature of the hazards involved, and work in collaboration with other safety officers. Where operation of an
unenclosed or partly closed system (e.g. during maintenance) takes place, the region in which the laser is being
operated should be clearly indicated. This should be as small as consistent with safety and contain only
personnel working directly on lasers. In the case of industrial laser installation this is best achieved by initially
installing the laser in a separate room. At all entrances to this region a cautionary sign should be displayed.
Examples of signs recommended by The American National Standards Institute (ANSI) Standard Z136 [5] are
illustrated in Figure-2.
During the last many years much effort have been made to develop eye safe lasers (i.e. using materials
such as Er:YAG, Er:glass etc.), basically for rangefinders using single pulse of very high intensity, but at a eye-
safe wavelength [7]. With lasers of this eye safe kind, range measurement capabilities of 10 km or more have
been obtained. The main disadvantage of these rangefinders is their complexity, power efficiency and reliability
[8]. Nd:YAG laser removes most of these discrepancies and therefore used as a superior rangefinder. The only
problem in using Nd:YAG laser is, its emission in ocular region (i.e., 1.064 m). Which is particularly in the
near infrared region, where the laser often significantly powerful. Thus it is possible to acquire severe retinal
damage from a laser beam that we cannot see. Optical parametric devices generate broadly tunable coherent
optical radiation by the phase-matched nonlinear interaction of an intense laser beam in a suitable nonlinear
crystal. In this process the high energy pump photon is converted into a pair of lower frequency signal and idler
photons while conserving the total energy and momentum. Tunability of the signal-idler pair is usually achieved
either by changing the crystal birefringence through its temperature dependence or by the angular dependence of
the extraordinary index of the crystal. The practical optical parametric oscillator (OPO) device consists of a
nonlinear crystal enclosed in an optical cavity resonant at either or both the signal and idler wavelengths and
pumped by Nd:YAG laser [9][10].
III. SECOND ORDER NONLINEAR PROCESSES:
In the regime of conventional optics, the electric polarization vector P is simply assumed to be linearly
proportional to the electric field strength E of an applied optical wave, i.e.
E
0
P (1)
where 0 is the free-space permittivity, is the susceptibility of a given medium and a plot of P versus E is a
straight line. The relation (1) is valid for the field strengths of conventional sources. The quantity is a
constant only in the sense of being independent of E; its magnitude is a function of the frequency. With
sufficiently intense laser radiation this relation does not hold good and has to be generalized to equation (2),
which can be written in the vector form, as by a power series
P = 0[(1)
E+ (2)
EE + (3)
EEE + --------] (2)
]..........)
0
()()(),,(
)(
3
)()(),(
)(
)2(
)()(
)1(
[
0
)(
lnkmjonm
jkl mno
ijkl
nkmjnm
jk mn
ijkmjm
ijj
ji
EEE
EEEP
(3)
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where
)1(
ij
is a second – rank (linear) tensor (9 components xx, xy, xz, yx,……..), where
)2(
ijk
is a third -rank
(nonlinear) tensor (27 components, xxx, xxy, xxz, xyx,…….), and
)3(
ijkl
is a forth-rank (nonlinear) tensor (81
components, xxxx,xxxy, xxxz, xxyx,……). The values of the tensor coefficients are functions of frequency and
temperature. The subscripts m, n, and o etc. denotes different frequency components, and i, j, k and l are
Cartesian indices that run from 1 to 3 [1][20]. For small field strength the polarization is proportional to the
electric field E and is accounted for by the polarizatbility tensor
)1(
ij
. All of the optics discussed so far has been
linear optics encompassed in the term )()(
)1(
0 mjmij E . This term represents optical phenomenon that are
proportional to the electric field and are at the frequency of incoming wave.
The term )()(),(
)2(
nkmjnmijk
EE is responsible for all of the two-wave effects. This includes
second harmonic generation (two fields at to make one at 2) and parametric oscillation (one field at 1 and
other field at 2 to create fields at 1 - 2 and 1 + 2). This also includes optical mixing, and the Pocals effect
(change of index of refraction with applied electric field). The nonlinear polarization tensor
)2(
vanishes in
the crystals that have a center of symmetry (i.e. crystal symmetry). In these crystals second harmonic generation
is not possible. As a result of, many of the components of
)2(
will be zero or equal to other components of the
tensor. Thus the second-order polarization and the corresponding monochromatic components of the optical
field:
)
2
()
1
()
2
,
1
(
)2(
0
)
21
(
)2(
EEP (4)
where
)2(
denotes the second-order susceptibility that is a third-order tensor.
Desmond [19] simplified
)2(
ijk
, and replaced by a nonlinear optical coefficient dil (Coulomb/Volt2
), according to
the following relationship:
xyzxyzzzyyxxjk
l
ijkil
d
,,,,,
6,5,4,3,2,1)2(
0
(5)
i.e., the nonlinear optical coefficient dijk is symmetric in j and k and according to Khun [1]
)2(
2
1
ijkij
d , here,
0, is the permittivity of free space, some authors excludes 0 from the d coefficient, in this case d [As/V2
] =
8.855 10-12
d [m/v]. The conversion from the cgs system to MKS units becomes d [As/V2
] = 3.68 10-15
d
[esu]. In most practical situations the tensor equations containing dijk can be simplified to non-tensor form in
which dijk is replaced by deff, is the effective nonlinear coefficient for the interaction dependent on crystal
symmetry and propagation direction in the medium.
3.1 Second Harmonic Generation:
The simplest second-order process is that of second-harmonic generation (SHG). In this process, an
intense laser beam of angular frequency 1 (= ) is passed through a crystal having nonzero value of
)2(
, such
that the beam emerging from the crystal contains the angular frequencies 1 of the input beam and also 2 =
21, twice the frequency of the input beam. This can be shown to occur by considering the second nonlinear
polarization term
)2(
P .
3.2 Optical Sum and Difference Frequency Generation:
In the second-harmonic generation, considered the combination (addition) of two photons of the same
frequency to produce a single photon of twice the frequency. It can now to generalize this process to allow for
the case in which the two photons have different frequencies 1 and 2. These include second harmonic terms
(involving 21 and 22), and two new terms involving 1 + 2 and 1 - 2. The new term involving 1 + 2
generates a new frequency that is the sum of the two original frequencies and is thus known as sum frequency
generation. The term involving the difference between the two frequencies, 1 - 2 , is referred to as difference
frequency generation. In the process of difference frequency mixing, the frequency 2 is amplified while the
frequency 3 is being generated. In the process of optical parametric oscillation (OPO) the intense input laser
beam at frequency p is known as the pump frequency, when passes through a nonlinear material, generates the
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desired frequencies s (signal frequency) and the frequency i (idler frequency) [20].The amplification can be
enhanced by placing the optical harmonic (nonlinear) crystal within an optical cavity in which the mirrors are
specifically made reflective at either one of these two frequencies, or for both. Thus the intensity at those
frequencies will build up within the cavity, by Fabry-Perot interferometer. Such an amplification process is
known as an optical parametric oscillator (OPO). Of course, either s or i can be tunable laser to generate
amplified tunable output. This process is used most often in the infrared frequency range, where tunable lasers
are not as readily available as in the visible portion of the frequency spectrum [13]. The output of an optical
parametric oscillator (OPO) is similar to that of a laser. The energy conservation requires that
isp (6)
Here p, s, and i are the frequencies of the pump, signal and idler wave. For a given p, there can be a
continuous range of choices of s and i. This, in fact, is the origin of the tunability of the optical parametric
oscillator. The specific pair of frequencies that will be emitted is dictated by the momentum conservation
condition, or phase matching condition: kp = ks + ki, that must also be satisfied in order to ensure that the signal
waves generated in different parts of the nonlinear crystal are in phase and add coherently [12]. For collinearly
propagating waves this may be written
i
n
isnspnp
i
i
n
s
sn
p
pn
(7)
Here np, ns and ni are the refractive indices of the pump, signal and idler wave and p, s and i there
corresponding wavelengths respectively. The pump signal is usually provided by a laser and, therefore p is
fixed. However, if the refractive indices are varied, the signal and idler frequencies will tune. Under an
appropriate arrangement for the angle (or temperature) of a given nonlinear crystal, the above two requirements
(Eq. (6) & (7)) can be satisfied and oscillations at two different frequencies s, and i can be achieved. Based
on this working condition, if we slightly change the angle or temperature of the crystal, the refractive index
relation between these three waves will be changed; therefore the oscillating frequencies will be smoothly tuned
to different values [10][14].
The requirements of nonlinear crystals for optical parametric oscillation are essentially the same as that
for SHG. In other words, the nonlinear materials must be non-centrosymmetrical crystals, highly transparent for
pump, signal, and idler beams, able to fulfill the phase matching by using angle-tuning or temperature-tuning. In
principle, all commonly used SHG crystals used for OPO purpose. A possible simple implementation of the
optical parametric oscillator is shown schematically in Figure-3.
FIGURE 3. Singly-Resonant Optical Parametric Oscillator
It is consist of a suitably oriented nonlinear optical crystal in a Fabry-Perot cavity. The cavity mirrors are coated
to transmit the pump wave and reflect either the signal wave only or both the signal and idler waves.
In the former case, the oscillator is known as the singly resonant oscillator, and, in the latter case, it is
known as the doubly resonant oscillator. After passing through the output-coupling mirror the transmitted pump
beam is blocked by a filter. The further separation between the signal beam and idler beam can be done by using
appropriate spectral filters or optical dispersive elements. Various optical cavity designs, including stable,
unstable, or metastable cavity configurations, can be employed for OPO purpose. The criteria of selection of
cavity designs are same as that for laser cavity devices [20].
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3.3 Nonlinear Optical Materials
For generating new frequencies from existing lasers via harmonic generation and difference generation,
they must (1) be resistant to optical damage, (2) have high mechanical hardness, (3) exhibit good thermal and
chemical stability, (4) be capable of being grown in useful sizes, and (5) have the appropriate phase-matching
properties. The second harmonic crystals must have no inversion symmetry (i.e. non-centrosymmetric). Bulk
second-order nonlinear materials are generally inorganic crystals. A number
Table-3. Properties of some important nonlinear crystals6
of semiconductors are useful for second harmonic generation when used in waveguides. The nonlinear crystals
can be classified into two groups according to their physical properties. Crystals grown from water solutions
are fragile, hygroscopic, and sensitive to thermal shock. The crystals of this group, to which KDP and its
isomorphs belong, are somewhat difficult to handle because the crystals are soft, and the polished faces may be
fogged if they are held with bare hands or exposed to humid atmosphere. On the other hand, the crystals are
easy to grow, they are available in large sizes, and they are of excellent optical quality. Crystals grown from
the melt are relatively hard, nonhygroscopic and less sensitive to thermal shock. Important members of this
group crystals are LiNbO3 (LBO) , Ba2NaNb5O15 (BBO) and KTiOPO4 (KTP). KTP possesses good optical
properties, a large acceptance angle, large temperature acceptance, a large nonlinear coefficient, and high
optical damage thresholds [9] [10].
IV. CONCLUSION
In summary laser safety research must involve investigation of the effects of laser exposure in the visible
and near-infrared. Many civilian and military laser devices involve both visible and near infrared laser sources.
Accidental exposure under these conditions may involve a wide range of exposure from acute retinal exposure
well above the Maximum Permissible Exposure (MPE), therefore it is required to use precautions. Thus Optical
parametric devices generate broadly tunable coherent optical radiation by the phase-matched nonlinear
interaction of an intense laser beam in a suitable nonlinear crystals such as KTP etc. In this process the high
energy pump photon is converted into a pair of lower frequency signal and idler photons while conserving the
total energy and momentum. Tunability of the signal-idler pair is usually achieved either by changing the crystal
birefringence through its temperature dependence or by the angular dependence of the extraordinary index of the
crystal. The practical optical parametric oscillator (OPO) device consists of a nonlinear crystal enclosed in an
optical cavity resonant at either or both the signal and idler wavelengths and pumped by Nd:YAG laser.
REFERENCES
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[3] John E. Harry; “Industrial Lasers and their applications”. McGraw Hill, New York.
[4] D. C. Winburn; “Practical Laser Safety”, 2d ed. (New York: Marcel Dekker, Inc. 1990.
[5] Americal National Standard for the safe use of Laser, ANSI Z136, 1-1973, Americal National Standards, Inc., New
York, USA.
[6] Safety with Lasers, Brit. Med. J., 3(5765), 3-4, 1971.
[7] L. R. Marshall, A. D. Hays, H. J. Kasinski, and R. Burnham; SPIE, 1419, 141-152 (1991).
[8] R. D. Stultz, D. E. Nieuwsma, E. Gregor; SPIE, 1419, 64-74 (1991).
[9] Walter Koechner, Solid State Laser Engineering, 5rh ed., (Springer Berlin 1999).
[10] Willium T. Silfvast, Laser Fundamentals, (Cambridge university Press 1991).
[11] H. K. V. Lotsch; Japan J. Appl. Phys, 4, 435 (1965).
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[13] S. Wang, V. Pasiskevicius, J. Hellstrom, F. Laurell, and H. Karlsson, “First-order type-II quasi-phase-matched UV
generation in periodically poled KTP”, Opt. Lett. 24, 978-980 (1999).
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[15] K. Kato; Appl. Phys. Letters, 25, 342 (1974).
Property KTP BBO LBO CLBO
Nonlinear coefficient (pm/V) 3.1 1.94 1.16 1.11
Transmission range (m) 0.35 - 5.5 0.19 - 3.5 0.16 – 2.6 0.16 – 2.6
Damage threshold (GW/cm2
) > 0.5 1.5 2.5 > 2.5
Angular acceptance (mrad-cm) 20 < 1 2 1.4
Spectral acceptance (mm-cm) 0.5 0.5 0.8 1
Walk-off angle (degree) 1.3 5.5 <1 1.8
Damage resistance to moisture High Low Low Medium
7. Eye Safe Laser Using Optical Parametric…
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[16] K. Kato; IEEE J. Ouant. Electr. QE-10, 622 (1974).
[17] G. Nath, S. Haussuhal; Appl. Phys. Lett., 14, 154 (1969).
[18] J. E. Bjorkholm; IEEE J. Ouant. Electr. QE-4, 970 (1968).
[19] S. Desmond Smith; Optoelectronic Devices, (Prentice Hall Pub., 1995).
[20] W. Boyd, Non-Linear Optics (Boston, MA; Academic Press, (1992).