Lasers emit light that is highly directional, monochromatic, and coherent. Common laser components include an active medium, excitation mechanism, and high and partially reflective mirrors. Lasing occurs when atoms in the active medium are excited and stimulated emission produces photons. Laser output is measured in watts, joules, irradiance, and pulsed vs. continuous wave. Laser hazards include eye, skin, chemical, electrical, and fire risks. Lasers are classified based on wavelength, average power, energy per pulse, and beam exposure to determine appropriate safety controls.
(A) By active media
Solid state laser - crystal, or glass, doped with impurities, e.g. ruby laser, Ti:sapphire laser, semiconductor laser.
Gas laser - e.g. He-Ne laser, Ar+ laser, CO2 laser, N2 laser, HCN laser.
Dye laser - active medium: dye molecules in liquid solvent (sometimes in solids also).
(B) By mode of operation
CW
Pulsed
(C) By pumping and laser levels
3-level laser
4-level laser
Basics refresher on Laser Technology and it's applications. Presentation prepared by (and for) student(s). Level- Karnataka State Pre-university PUC1(India)
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation
(A) By active media
Solid state laser - crystal, or glass, doped with impurities, e.g. ruby laser, Ti:sapphire laser, semiconductor laser.
Gas laser - e.g. He-Ne laser, Ar+ laser, CO2 laser, N2 laser, HCN laser.
Dye laser - active medium: dye molecules in liquid solvent (sometimes in solids also).
(B) By mode of operation
CW
Pulsed
(C) By pumping and laser levels
3-level laser
4-level laser
Basics refresher on Laser Technology and it's applications. Presentation prepared by (and for) student(s). Level- Karnataka State Pre-university PUC1(India)
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation
Low Level Laser Therapy is a non-chemical, side-effect free option for those with hair loss and hair thinning. Does Laser Therapy actually work? What are the mechanisms of low level laser therapy on the scalp and hair follicle. Are there any adverse effects?
Low Level Laser Therapy (LLLT) has been used for wound healing, pain control, lipolysis, anti-inflammatory properties and more. The mitochondrial-based cytochrome-c-oxidase molecule in the electron transport chain accepts the photon which then causes a cascade of events leading to increased ATP production and more.
Over time, when hair follicles that are producing weak, thin, wispy hair are exposed to significant doses of LLLT at regular intervals improvement in hair quality can be seen and measured.
As the delivery of LLLT has become easier for patients (portable) and more powerful over time due to the decreasing cost of laser-diodes, results have improved.
Old-style hand-held devices are relatively weak and many head-worn units contain weak non-laser, non-coherent LED's.
Newer devices like the cordless, rechargeable, 100% hands-free, discreet LaserCap and the hand-held Nutreve personal laser are making it easier for patients to achieve the results they seek.
LaserCap contains 224 diodes at 5mw in a paper-thin circuit board that is sized to fit underneath a standard baseball hat, bandana or scarf. It's rechargeable battery pack makes it the most powerful, portable device available for hair loss patients. 30 min every other day.
Nutreve's Personal Laser, hand-held rechargeable 35 diode unit contains the most diodes of any hand-held on the market today. 20 minutes over one area every other day.
Patients can see thicker, fuller and healthier hair within a few months of use but it does not reverse severe baldness where depletion of hair follicle density has already occurred.
Dr. Alan J. Bauman, M.D.
doctorb@baumanmedical.com
ABHRS Certified
Lecture 2 Basic Concepts in Machine Learning for Language TechnologyMarina Santini
Definition of Machine Learning
Type of Machine Learning:
Classification
Regression
Supervised Learning
Unsupervised Learning
Reinforcement Learning
Supervised Learning:
Supervised Classification
Training set
Hypothesis class
Empirical error
Margin
Noise
Inductive bias
Generalization
Model assessment
Cross-Validation
Classification in NLP
Types of Classification
We have made an experimental set-up to measure thermal conductivity of oil. Experimental setup is designed in such a way that the accuracy it obtain is kept at the same level, while the cost of the experimentation is reduced to 1/10th of other equivalent model available in market. Modifications done are in positioning of the thermocouple, mass flow rate of the water through the water jacket and its arrangement, the design and placement of heater, the positioning oil pocket for oil, use of less costly and widely available material, etc.
PRESENTATION 4- Basics of Laser in Dermatolgy
It includes -
Laser spectrum
Definition Laser
Classification of Lasers
Laser Theories
Laser terminology
Laser Hazards
A laser is a device that generates light by a process called STIMULATED EMISSION.
The acronym LASER stands for Light Amplification by Stimulated Emission of Radiation
Semiconducting lasers are multilayer semiconductor devices that generates a coherent beam of monochromatic light by laser action. A coherent beam resulted which all of the photons are in phase.
Contents
Definition of a laser
Emission and absorption of radiation
Population Inversion
Optical Feedback
Fundamentals of laser operation
Laser Hazards
In the world ,we see that 2 type of laser are present ,we can point with the help of laser and we can cut the metal ,but we cannot "push" ,we can develop great thing with this concept
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for "light amplification by stimulated emission of radiation". The first laser was built in 1960 by Theodore H. Maiman at Hughes Research Laboratories, based on theoretical work by Charles Hard Townes and Arthur Leonard Schawlow. A laser differs from other sources of light in that it emits light coherently. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers. Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum, i.e., they can emit a single color of light. Temporal coherence can be used to produce pulses of light as short as a femtosecond.
Among their many applications, lasers are used in optical disk drives, laser printers, and barcode scanners; DNA sequencing instruments, fiber-optic and free-space optical communication; laser surgery and skin treatments; cutting and welding materials; military and law enforcement devices for marking targets and measuring range and speed; and laser lighting displays in entertainment.
Modern telescopes use laser technologies to compensate for the blurring effect of the Earth’s atmosphere.
Lasers are distinguished from other light sources by their coherence. Spatial coherence is typically expressed through the output being a narrow beam, which is diffraction-limited. Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can have very low divergence in order to concentrate their power at a great distance.
Temporal (or longitudinal) coherence implies a polarized wave at a single frequency whose phase is correlated over a relatively great distance (the coherence length) along the beam. A beam produced by a thermal or other incoherent light source has an instantaneous amplitude and phase that vary randomly with respect to time and position, thus having a short coherence length.
Lasers are characterized according to their wavelength in a vacuum. Most "single wavelength" lasers actually produce radiation in several modes having slightly differing frequencies (wavelengths), often not in a single polarization. Although temporal coherence implies monochromaticity, there are lasers that emit a broad spectrum of light or emit different wavelengths of light simultaneously. There are some lasers that are not single spatial mode and consequently have light beams that diverge more than is required by the diffraction limit. However, all such devices are classified as "lasers" based on their method of producing light, i.e., stimulated emission. Lasers are employed in applications where light of the required spatial or temporal coherence could not b
It's a Basic concept of Laser on the basis of bandgap. I tried to explain on the easiest way the semiconductor and then i gave the view on Islamic perspective about Laser concept.
INTRODUCTION
HISTORY
PRINCIPLES OF WORKING OF A LASER
FUNDAMENTALS OF LASER
CHARACTERISTICS OF LASER
CLASSIFICATION OF LASER
EFFECTS OF LASER ON SOFT AND HARD TISSUES
VARIOUS LASERS AVAILABLE FOR PERIDONTAL USE
APPLICATION OF LASER TREATMENT IN PERIODONTAL THERAPY
ADVANTAGES & DISADVANTAGES OF LASER IN PERIODONTAL THERAPY
LASER PRECAUTIONS
LASER HAZARDS
RECENT ADVANCES
CONCLUSION
6. Laser Components Gas lasers consist of a gas filled tube placed in the laser cavity. A voltage (the external pump source) is applied to the tube to excite the atoms in the gas to a population inversion. The light emitted from this type of laser is normally continuous wave (CW).
7.
8. Lasing Action Diagram Energy Introduction Ground State Excited State Metastable State Spontaneous Energy Emission Stimulated Emission of Radiation
9. Laser Output watt (W) - Unit of power or radiant flux (1 watt = 1 joule per second). Joule (J) - A unit of energy Energy (Q) The capacity for doing work. Energy content is commonly used to characterize the output from pulsed lasers and is generally expressed in Joules (J). Irradiance (E) - Power per unit area, expressed in watts per square centimeter. Time Continuous Output (CW) Pulsed Output (P) Energy (Watts) Time Energy (Joules)
17. CONCLUSION: Laser communication in space has long been a goal for NASA because it would enable data transmission rates that are 10 to 1,000 times higher than traditional radio waves. While lasers and radio transmissions both travel at light-speed, lasers can pack more data. It's similar to moving from a dial-up Internet connection to broadband. Astronomers could use lasers like very accurate rulers to measure the movement of planets with unprecedented precision. With microwaves, we're limited to numbers like a meter or two in distance, whereas [lasers have] a potential for getting down into well beyond the centimeter range.