1. LASER stands for 'Light Amplification by Stimulated Emission of Radiation'. It produces a very intense, concentrated, highly parallel and monochromatic beam of light.
2. Coherence is an important property of laser light. Ordinary light sources produce incoherent light with a wide range of frequencies, while laser produces coherent light that is uniform in frequency, amplitude, continuity and constant initial phase difference.
3. Population inversion is achieved by pumping atoms to a higher energy metastable state such that more atoms are in the excited state than the lower energy state. This allows for stimulated emission to overtake absorption, leading to amplification of light in the laser medium.
This document discusses the basics of lasers, including their main components and properties. It explains that lasers work by inducing population inversion through pumping, allowing for stimulated emission to produce coherent, monochromatic beams of light. The key parts of a laser are its active medium, pumping source, and optical resonator. Examples of different laser types include solid state, gas, liquid/dye, and semiconductor lasers. Lasers have many applications in areas like communication, medicine, manufacturing, and research.
Lasers produce a very narrow, intense beam of coherent light through the process of stimulated emission of radiation. Key characteristics of laser light include high monochromaticity, directionality, intensity, and coherence. Einstein's theory of stimulated emission explains how excited atoms or molecules can emit photons when stimulated by an incoming photon, leading to amplification of the light beam. Population inversion, where more atoms are in an excited state than a lower state, must be achieved for lasing to occur. Common laser types include solid-state, gas, liquid/dye, and semiconductor lasers, which use different active media and pumping mechanisms to produce stimulated emission. A notable example is the Nd:YAG laser, which uses a neody
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 document provides information on the basics of lasers and laser light. It defines LASER as an acronym for Light Amplification by Stimulated Emission of Radiation. It describes the key properties of laser beams including high coherence, intensity, directionality, and monochromaticity. It also discusses atomic transitions, population inversion, components of lasers including the active medium and optical resonator, and provides examples of specific lasers such as Nd:YAG lasers.
The document discusses lasers, providing details on:
1. How lasers work through the process of stimulated emission of radiation, using a pumping mechanism to create population inversion in the active medium.
2. The key characteristics of laser light being monochromatic, coherent, and highly directional.
3. Examples of common laser types like Ruby and Nd:YAG lasers, describing their construction and working.
4. Applications of lasers in various fields like industry, medicine, communication, and more.
1. A laser works by stimulating the emission of coherent light through a process called stimulated emission.
2. Atoms in a lasing medium are excited to a higher energy level through an external energy source, creating a population inversion where there are more excited atoms than unexcited atoms.
3. When an excited atom spontaneously decays and emits a photon, that photon can stimulate the emission of another photon of the same wavelength, phase, and direction, producing an amplified, coherent beam of light.
Lasers have a wide variety of applications including manufacturing, medicine, metrology, data storage, communications, displays, spectroscopy, microscopy, and more. They are used for cutting, welding, drilling, marking, engraving, and other industrial processes. In medicine they are used for eye surgery, dentistry, cancer treatment, and other procedures. Lasers are also widely used in optical metrology, data storage such as CDs and DVDs, fiber optic communications, laser displays, spectroscopy, microscopy, and scientific applications like laser cooling and optical tweezers.
This document provides an overview of lasers and their applications. It begins with a brief history of lasers, describing their development from Einstein's work on stimulated emission in 1917 to the creation of the first working laser by Maiman in 1960. It then outlines the basic theory of how lasers work, including population inversion and stimulated emission. Finally, it mentions that the document will cover the characteristics of laser beams, types of laser sources, and applications of lasers.
This document discusses the basics of lasers, including their main components and properties. It explains that lasers work by inducing population inversion through pumping, allowing for stimulated emission to produce coherent, monochromatic beams of light. The key parts of a laser are its active medium, pumping source, and optical resonator. Examples of different laser types include solid state, gas, liquid/dye, and semiconductor lasers. Lasers have many applications in areas like communication, medicine, manufacturing, and research.
Lasers produce a very narrow, intense beam of coherent light through the process of stimulated emission of radiation. Key characteristics of laser light include high monochromaticity, directionality, intensity, and coherence. Einstein's theory of stimulated emission explains how excited atoms or molecules can emit photons when stimulated by an incoming photon, leading to amplification of the light beam. Population inversion, where more atoms are in an excited state than a lower state, must be achieved for lasing to occur. Common laser types include solid-state, gas, liquid/dye, and semiconductor lasers, which use different active media and pumping mechanisms to produce stimulated emission. A notable example is the Nd:YAG laser, which uses a neody
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 document provides information on the basics of lasers and laser light. It defines LASER as an acronym for Light Amplification by Stimulated Emission of Radiation. It describes the key properties of laser beams including high coherence, intensity, directionality, and monochromaticity. It also discusses atomic transitions, population inversion, components of lasers including the active medium and optical resonator, and provides examples of specific lasers such as Nd:YAG lasers.
The document discusses lasers, providing details on:
1. How lasers work through the process of stimulated emission of radiation, using a pumping mechanism to create population inversion in the active medium.
2. The key characteristics of laser light being monochromatic, coherent, and highly directional.
3. Examples of common laser types like Ruby and Nd:YAG lasers, describing their construction and working.
4. Applications of lasers in various fields like industry, medicine, communication, and more.
1. A laser works by stimulating the emission of coherent light through a process called stimulated emission.
2. Atoms in a lasing medium are excited to a higher energy level through an external energy source, creating a population inversion where there are more excited atoms than unexcited atoms.
3. When an excited atom spontaneously decays and emits a photon, that photon can stimulate the emission of another photon of the same wavelength, phase, and direction, producing an amplified, coherent beam of light.
Lasers have a wide variety of applications including manufacturing, medicine, metrology, data storage, communications, displays, spectroscopy, microscopy, and more. They are used for cutting, welding, drilling, marking, engraving, and other industrial processes. In medicine they are used for eye surgery, dentistry, cancer treatment, and other procedures. Lasers are also widely used in optical metrology, data storage such as CDs and DVDs, fiber optic communications, laser displays, spectroscopy, microscopy, and scientific applications like laser cooling and optical tweezers.
This document provides an overview of lasers and their applications. It begins with a brief history of lasers, describing their development from Einstein's work on stimulated emission in 1917 to the creation of the first working laser by Maiman in 1960. It then outlines the basic theory of how lasers work, including population inversion and stimulated emission. Finally, it mentions that the document will cover the characteristics of laser beams, types of laser sources, and applications of lasers.
The document discusses lasers, including:
- LASER is an acronym for Light Amplification by Stimulated Emission of Radiation.
- Lasers were invented in 1958 and are based on Einstein's idea of particle-wave duality of light.
- The key principles of lasers are stimulated emission within an amplifying medium and population inversion within an optical resonator.
- Common laser types discussed include ruby, He-Ne, argon ion, CO2, excimer, and solid-state lasers like Nd:YAG.
The document provides an overview of lasers, including their introduction, characteristics, population inversion, types of coherence, and applications. It discusses key laser concepts such as spontaneous emission, stimulated emission, optical pumping, threshold inversion density, and optical feedback. Examples of specific laser types are given, including ruby lasers, HeNe lasers, and semiconductor lasers. The document concludes with applications of lasers in areas like welding, medicine, data storage, printing, and military weapons.
1. The document discusses the working principles of lasers, including the key components of a laser system and the processes of stimulated emission and population inversion that enable laser action.
2. It specifically describes different laser types such as ruby lasers, He-Ne lasers, semiconductor diode lasers, and their applications. Ruby was the first laser invented and produces red light, while He-Ne lasers emit visible light in the red and infrared spectrum.
3. The document provides detailed explanations of laser concepts like optical pumping, energy level diagrams, cavity mirrors, and continuous wave versus pulsed operation.
Optical detectors, as the name implied, can detect the amount of light received. It is a device that converts light signals into electrical signals, which can then be amplified and processed.
The document summarizes the photoelectric effect, which is the ejection of electrons from a metal surface when light of a suitable frequency strikes it. It explains that the photoelectric effect supports the particle theory of light. It provides the typical experimental setup, relationships between the energy of photons and kinetic energy of emitted electrons, and current and applied potential difference. It also outlines the laws of the photoelectric effect and Einstein's equation relating the maximum kinetic energy of electrons to the photon energy and metal's work function.
Laser Action
The combination of spontaneous emission first, and then stimulated emission, causes the laser to "lase," which means it generates a coherent beam of light at a single frequency.
(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
The document discusses lasers, including their history, characteristics, components, classifications, and uses. It provides details on:
- The invention of the laser by Maiman in 1960 and its influence as a technological achievement.
- The key characteristics of laser light that make it coherent, directional, and monochromatic.
- The basic components and functioning of a laser, including the active medium, excitation mechanism, and optical resonator.
- The various classes of lasers according to output levels and safety standards.
- Applications of lasers in medicine, industry, everyday life, research, and holography.
This document discusses the cyclotron, a type of particle accelerator. It begins with an introduction and overview of key topics like principles, construction, diagrams, workings, calculations, applications, and limitations. Some key points made are:
- A cyclotron accelerates charged particles like protons and deuterons using electric and magnetic fields, generating energies from 1 MeV to over 100 MeV.
- It works on the principle that a charged particle moving perpendicular to a magnetic field experiences a force causing it to travel in a circular path, with increasing radius and velocity over time due to an oscillating electric field.
- Important applications of cyclotrons include production of beams for nuclear physics experiments and cancer particle therapy.
There are three main types of laser gain media: gases, liquids, and solids. Gases like CO2 have narrow wavelength gain, while liquids like dyes have broad gain. Solid state lasers like Nd:YAG can have either narrow or broad gain depending on the material. All gain media require pumping to receive energy, which can be optical pumping using lamps or flashlights, or electrical pumping using gas discharges. Q-switching is a technique to produce high power pulses using a Pockels cell to prevent lasing until a population inversion is fully inverted.
Dye lasers use an organic dye dissolved in a liquid as the active lasing medium and can produce a wide range of wavelengths. They work on the principle of population inversion using a pumping source like a flash lamp or other laser to excite the dye molecules. The major components are the active dye medium, pumping source, and resonator mirrors, with one mirror sometimes replaced by a diffraction grating to allow tuning of the output wavelength. Dye lasers offer tunability but have limitations in lifetime and output power.
This document summarizes key concepts about laser beams and optical resonators:
1) Laser beam propagation can be described by the Helmholtz equation, with one solution being a Gaussian beam profile. The beam waist radius varies along the beam axis according to the Rayleigh range.
2) Optical resonators provide feedback to turn an amplifier into an oscillator. They contain mirrors between which light bounces and is amplified on each pass through the gain medium.
3) Resonator stability depends on the curvature and separation of the mirrors. Different resonator types support distinct transverse mode patterns within the beam.
The document discusses the interaction of radiation with matter. It explains that radiation can be electromagnetic or particulate. When electromagnetic radiation like x-rays or gamma rays pass through matter, they can undergo attenuation, absorption, scattering, or transmission. The major interactions that cause attenuation are coherent scattering, the photoelectric effect, the Compton effect, pair production, and photonuclear interactions. It describes each of these interactions in detail and how they transfer energy from the radiation to the absorbing material.
The laser was invented in 1960 by Theodore Maiman. It works by stimulating the emission of light through a process called optical amplification. The key components of a laser are an active medium to generate the light, an excitation mechanism like electricity to energize the medium, and an optical resonator with mirrors to reflect the light waves and produce coherent, monochromatic light. Lasers have many applications, including use in medicine for procedures like removing gallstones, in manufacturing for precision tasks like drilling, and in everyday devices like barcode scanners, CD players, and communication networks.
The document discusses solid-state lasers, which use a crystalline solid as the amplifying medium doped with ions that emit light through stimulated emission. Common solid materials used include ruby, titanium sapphire, and neodymium-doped crystals. The doped ions are chosen from rare-earth, transition metal, and actinide elements for their radiative properties. Solid-state lasers provide higher gain density and good thermal and optical qualities compared to other laser types.
This document provides an introduction to lasers, including:
1. Lasers emit coherent light through stimulated emission of radiation and population inversion.
2. The key properties of lasers are that the light is monochromatic, coherent, and directional.
3. The basic components of a laser are an active medium, pumping source, and optical resonator cavity.
4. Common laser types are He-Ne lasers, which use a gas mixture of helium and neon, and semiconductor diode lasers.
B.tech sem i engineering physics u ii chapter 2-laserRai University
The document provides information about LASER (Light Amplification by Stimulated Emission of Radiation). It discusses the principle of LASER including absorption, spontaneous emission, stimulated emission and population inversion. It describes the key characteristics of laser light such as coherence, high intensity, high directionality and monochromaticity. It also discusses different types of lasers including solid (ruby), liquid and gas (He-Ne, CO2) lasers. Specific details provided include the construction and working of ruby and He-Ne lasers.
The document discusses lasers, including their characteristics and operation. It describes how lasers work via stimulated emission and population inversion. Nd:YAG lasers are discussed as a common solid-state laser type. Applications of lasers mentioned include medicine, manufacturing, communications, and more.
The document discusses the basics of lasers. It explains that lasers work via the process of stimulated emission, where photons stimulate excited electrons to emit additional photons of the same frequency and direction. This leads to coherent, highly directional light that is monochromatic and has high intensity and brightness. The key aspects that enable lasers are population inversion, where more atoms are in excited states than ground states, and stimulated emission, where incident photons cause excited electrons to emit additional photons coherently.
The document discusses laser and holography. It defines laser as "Light Amplification by Stimulated Emission of Radiation" and describes the key properties of lasers including being monochromatic, coherent, and directional. It explains the basic concepts of absorption, spontaneous emission, stimulated emission, and population inversion which are necessary for laser operation. The document also provides details about different types of lasers and their applications. It concludes with an overview of holography including the basic principles and techniques for constructing and reconstructing holograms.
Einstein's coefficients describe the interaction between matter and radiation. Absorption occurs when an atom absorbs energy and electrons move to a higher energy level. Spontaneous emission is the random emission of a photon when an atom decays from a higher to lower energy level. Stimulated emission occurs when an incoming photon of a specific wavelength triggers an atom in an excited state to decay and emit an identical photon. Population inversion is required to achieve lasing, which is when there are more atoms in higher energy levels than lower levels. The Einstein A coefficient describes spontaneous emission rate, the B coefficients describe absorption and stimulated emission rates, and they are related through Einstein's relations. Lasers produce highly coherent, monochromatic light through dominant stimulated
The document discusses lasers, including:
- LASER is an acronym for Light Amplification by Stimulated Emission of Radiation.
- Lasers were invented in 1958 and are based on Einstein's idea of particle-wave duality of light.
- The key principles of lasers are stimulated emission within an amplifying medium and population inversion within an optical resonator.
- Common laser types discussed include ruby, He-Ne, argon ion, CO2, excimer, and solid-state lasers like Nd:YAG.
The document provides an overview of lasers, including their introduction, characteristics, population inversion, types of coherence, and applications. It discusses key laser concepts such as spontaneous emission, stimulated emission, optical pumping, threshold inversion density, and optical feedback. Examples of specific laser types are given, including ruby lasers, HeNe lasers, and semiconductor lasers. The document concludes with applications of lasers in areas like welding, medicine, data storage, printing, and military weapons.
1. The document discusses the working principles of lasers, including the key components of a laser system and the processes of stimulated emission and population inversion that enable laser action.
2. It specifically describes different laser types such as ruby lasers, He-Ne lasers, semiconductor diode lasers, and their applications. Ruby was the first laser invented and produces red light, while He-Ne lasers emit visible light in the red and infrared spectrum.
3. The document provides detailed explanations of laser concepts like optical pumping, energy level diagrams, cavity mirrors, and continuous wave versus pulsed operation.
Optical detectors, as the name implied, can detect the amount of light received. It is a device that converts light signals into electrical signals, which can then be amplified and processed.
The document summarizes the photoelectric effect, which is the ejection of electrons from a metal surface when light of a suitable frequency strikes it. It explains that the photoelectric effect supports the particle theory of light. It provides the typical experimental setup, relationships between the energy of photons and kinetic energy of emitted electrons, and current and applied potential difference. It also outlines the laws of the photoelectric effect and Einstein's equation relating the maximum kinetic energy of electrons to the photon energy and metal's work function.
Laser Action
The combination of spontaneous emission first, and then stimulated emission, causes the laser to "lase," which means it generates a coherent beam of light at a single frequency.
(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
The document discusses lasers, including their history, characteristics, components, classifications, and uses. It provides details on:
- The invention of the laser by Maiman in 1960 and its influence as a technological achievement.
- The key characteristics of laser light that make it coherent, directional, and monochromatic.
- The basic components and functioning of a laser, including the active medium, excitation mechanism, and optical resonator.
- The various classes of lasers according to output levels and safety standards.
- Applications of lasers in medicine, industry, everyday life, research, and holography.
This document discusses the cyclotron, a type of particle accelerator. It begins with an introduction and overview of key topics like principles, construction, diagrams, workings, calculations, applications, and limitations. Some key points made are:
- A cyclotron accelerates charged particles like protons and deuterons using electric and magnetic fields, generating energies from 1 MeV to over 100 MeV.
- It works on the principle that a charged particle moving perpendicular to a magnetic field experiences a force causing it to travel in a circular path, with increasing radius and velocity over time due to an oscillating electric field.
- Important applications of cyclotrons include production of beams for nuclear physics experiments and cancer particle therapy.
There are three main types of laser gain media: gases, liquids, and solids. Gases like CO2 have narrow wavelength gain, while liquids like dyes have broad gain. Solid state lasers like Nd:YAG can have either narrow or broad gain depending on the material. All gain media require pumping to receive energy, which can be optical pumping using lamps or flashlights, or electrical pumping using gas discharges. Q-switching is a technique to produce high power pulses using a Pockels cell to prevent lasing until a population inversion is fully inverted.
Dye lasers use an organic dye dissolved in a liquid as the active lasing medium and can produce a wide range of wavelengths. They work on the principle of population inversion using a pumping source like a flash lamp or other laser to excite the dye molecules. The major components are the active dye medium, pumping source, and resonator mirrors, with one mirror sometimes replaced by a diffraction grating to allow tuning of the output wavelength. Dye lasers offer tunability but have limitations in lifetime and output power.
This document summarizes key concepts about laser beams and optical resonators:
1) Laser beam propagation can be described by the Helmholtz equation, with one solution being a Gaussian beam profile. The beam waist radius varies along the beam axis according to the Rayleigh range.
2) Optical resonators provide feedback to turn an amplifier into an oscillator. They contain mirrors between which light bounces and is amplified on each pass through the gain medium.
3) Resonator stability depends on the curvature and separation of the mirrors. Different resonator types support distinct transverse mode patterns within the beam.
The document discusses the interaction of radiation with matter. It explains that radiation can be electromagnetic or particulate. When electromagnetic radiation like x-rays or gamma rays pass through matter, they can undergo attenuation, absorption, scattering, or transmission. The major interactions that cause attenuation are coherent scattering, the photoelectric effect, the Compton effect, pair production, and photonuclear interactions. It describes each of these interactions in detail and how they transfer energy from the radiation to the absorbing material.
The laser was invented in 1960 by Theodore Maiman. It works by stimulating the emission of light through a process called optical amplification. The key components of a laser are an active medium to generate the light, an excitation mechanism like electricity to energize the medium, and an optical resonator with mirrors to reflect the light waves and produce coherent, monochromatic light. Lasers have many applications, including use in medicine for procedures like removing gallstones, in manufacturing for precision tasks like drilling, and in everyday devices like barcode scanners, CD players, and communication networks.
The document discusses solid-state lasers, which use a crystalline solid as the amplifying medium doped with ions that emit light through stimulated emission. Common solid materials used include ruby, titanium sapphire, and neodymium-doped crystals. The doped ions are chosen from rare-earth, transition metal, and actinide elements for their radiative properties. Solid-state lasers provide higher gain density and good thermal and optical qualities compared to other laser types.
This document provides an introduction to lasers, including:
1. Lasers emit coherent light through stimulated emission of radiation and population inversion.
2. The key properties of lasers are that the light is monochromatic, coherent, and directional.
3. The basic components of a laser are an active medium, pumping source, and optical resonator cavity.
4. Common laser types are He-Ne lasers, which use a gas mixture of helium and neon, and semiconductor diode lasers.
B.tech sem i engineering physics u ii chapter 2-laserRai University
The document provides information about LASER (Light Amplification by Stimulated Emission of Radiation). It discusses the principle of LASER including absorption, spontaneous emission, stimulated emission and population inversion. It describes the key characteristics of laser light such as coherence, high intensity, high directionality and monochromaticity. It also discusses different types of lasers including solid (ruby), liquid and gas (He-Ne, CO2) lasers. Specific details provided include the construction and working of ruby and He-Ne lasers.
The document discusses lasers, including their characteristics and operation. It describes how lasers work via stimulated emission and population inversion. Nd:YAG lasers are discussed as a common solid-state laser type. Applications of lasers mentioned include medicine, manufacturing, communications, and more.
The document discusses the basics of lasers. It explains that lasers work via the process of stimulated emission, where photons stimulate excited electrons to emit additional photons of the same frequency and direction. This leads to coherent, highly directional light that is monochromatic and has high intensity and brightness. The key aspects that enable lasers are population inversion, where more atoms are in excited states than ground states, and stimulated emission, where incident photons cause excited electrons to emit additional photons coherently.
The document discusses laser and holography. It defines laser as "Light Amplification by Stimulated Emission of Radiation" and describes the key properties of lasers including being monochromatic, coherent, and directional. It explains the basic concepts of absorption, spontaneous emission, stimulated emission, and population inversion which are necessary for laser operation. The document also provides details about different types of lasers and their applications. It concludes with an overview of holography including the basic principles and techniques for constructing and reconstructing holograms.
Einstein's coefficients describe the interaction between matter and radiation. Absorption occurs when an atom absorbs energy and electrons move to a higher energy level. Spontaneous emission is the random emission of a photon when an atom decays from a higher to lower energy level. Stimulated emission occurs when an incoming photon of a specific wavelength triggers an atom in an excited state to decay and emit an identical photon. Population inversion is required to achieve lasing, which is when there are more atoms in higher energy levels than lower levels. The Einstein A coefficient describes spontaneous emission rate, the B coefficients describe absorption and stimulated emission rates, and they are related through Einstein's relations. Lasers produce highly coherent, monochromatic light through dominant stimulated
This document discusses the principles of lasing and population inversion. It explains that atoms have discrete energy levels and are typically in the lowest energy or ground state. For lasing, a population inversion is needed where more atoms are in an excited state than the ground state. This can be achieved by optical or electrical pumping methods. Optical pumping uses light to selectively excite atoms to higher energy levels, while electrical pumping passes current through gas lasers. Stimulated emission of photons can then occur, leading to amplification of light and lasing.
This document provides an overview of laser theory and applications across 4 chapters. Chapter 1 discusses the theory of lasing, including Einstein's theory of stimulated emission and how a population inversion enables light amplification in a laser medium. Chapter 2 will cover characteristics of laser beams. Chapter 3 will describe different types of laser sources. And Chapter 4 will discuss applications of laser technology.
This document discusses the theory of lasers and their applications. It begins with a brief history of lasers, noting their development in the 1960s. It then covers Einstein's theory of stimulated emission, the first laser devices created, and the characteristics of laser beams. The document discusses population inversion and amplification in laser media. It also covers types of laser sources and applications of lasers. The document contains four chapters: theory of lasing, characteristics of laser beams, types of laser sources, and laser applications.
1) Laser light is produced through stimulated emission of radiation using a process called optical amplification. This involves exciting atoms in an active medium to a higher energy state and using stimulated emission to generate coherent light.
2) The key requirements for laser action are population inversion, where more atoms are in an excited state than a lower energy state, stimulated emission of radiation, and optical feedback from an optical cavity formed by mirrors.
3) Lasers produce highly directional, coherent light that is monochromatic, while ordinary light is polychromatic, spreads in many directions, and is incoherent. The essential elements of a laser are an active medium, a power supply to excite the atoms, and an optical resonator
Chapter 1: THE ATOM MODEL :
Text book...An introduction to Atomic, Molecular Physics and LASER by Education Publishers, Aurangabad is useful for Physics students.
Lecture34e - EM Wave Propopagation.pptssuser88da4c
1) Maxwell's equations describe light waves and are used to derive the wave equation. Light waves are transverse electromagnetic waves with perpendicular electric and magnetic fields.
2) Light waves can constructively or destructively interfere depending on their relative phase and polarization. Waves of different frequencies do not interfere.
3) At low light levels, light behaves as particles called photons with energy proportional to frequency. Photon counting reveals the particle nature of light.
The document discusses the history and theory of lasers. It begins by explaining that a laser is an optical amplifier based on stimulated emission of radiation, as proposed by Einstein in 1917. The first laser was built in 1960 by Maiman using a ruby crystal. Key aspects discussed include:
- Laser operation requires a population inversion between energy levels.
- Common laser types include ruby, He-Ne, and semiconductor lasers.
- Semiconductor lasers use the stimulated emission from a p-n junction.
- Holograms were first made possible by the invention of the laser as a coherent light source. Applications of holography include credit cards, medical imaging, and art.
This document discusses the basic principles and characteristics of lasers. It defines lasers as devices that produce coherent beams of light through stimulated emission of radiation. The key concepts covered include absorption, spontaneous emission, stimulated emission, population inversion, and Einstein's coefficients. Lasers achieve population inversion through pumping mechanisms like optical pumping or electric discharge. Their beams exhibit high directionality, intensity, monochromacity, coherence, and a narrow divergence angle.
Atomic Physics and photoelectric effectGreg Scrivin
1. Electric charge can be positive or negative, and like charges repel while opposite charges attract. The strength of this electrostatic force depends on the magnitude of the charges and the distance between them, similar to the formula for gravitational force.
2. At the nuclear scale, the strong nuclear force is required to overcome the repulsion between positively charged protons and hold the nucleus together. This force only operates at very short ranges of 10-15 meters or less.
3. The photoelectric effect provided evidence that light behaves as particles called photons, with a frequency-dependent energy described by Planck's constant. Each material has a minimum photon energy threshold required to eject electrons from its surface.
1. The document discusses laser physics basics including spontaneous and stimulated emission processes described by Einstein A and B coefficients. It also covers rate equation analysis and the concept of gain saturation.
2. A four-level laser system is described where pumping promotes atoms to an excited state, stimulated emission occurs along the lasing transition, and spontaneous decay returns atoms to the ground state. Population inversion is required for lasing.
3. Gain saturation occurs when the stimulated emission rate exceeds the spontaneous decay rate, reducing the population inversion. This limits the maximum intensity a laser can produce.
This document provides an overview of the principles of laser operation. It discusses:
- Laser cavities consisting of an amplifying medium between two mirrors that provide feedback.
- Fabry-Perot resonators and the standing wave patterns that form from interference between waves moving in opposite directions within the cavity.
- Population inversion being necessary for stimulated emission to exceed absorption, allowing amplification of light passing through the active medium.
- Optical pumping being used to invert the population by exciting atoms to a long-lived excited state, building up a population there.
- Stimulated emission causing photons to be emitted in phase with the stimulating photon, allowing amplification through an avalanche effect within the inverted medium.
Lasers have several key characteristics including monochromaticity, directionality, intensity, and coherence. They work by inducing stimulated emission of photons from atoms in an excited meta-stable state, achieving population inversion. This process is triggered by stimulated emission and results in an intense, highly directional beam of coherent, monochromatic light. Common lasers include ruby, helium-neon, and semiconductor diode lasers. Lasers have numerous applications due to their unique light properties.
1. Dielectrics are materials that have permanent electric dipole moments due to their molecular structure.
2. When an electric field is applied, the dipoles in dielectrics can undergo various polarization processes including electronic, ionic, and orientational polarization which increase the electric flux density.
3. The internal or Lorentz field within a dielectric material is the local electric field experienced by molecules and consists of contributions from surface bound charges and dipoles induced in the material.
Dielectrics are materials that have permanent electric dipole moments. They contain atoms or molecules with separated positive and negative charges even in the absence of an electric field. When a dielectric is placed in an electric field, the electric dipoles within align with the field, causing polarization. There are several types of polarization that can occur in dielectrics, including electronic, ionic, and orientational polarization, each occurring at different frequencies. The dielectric constant of a material is a measure of how much it increases the electric flux density compared to empty space.
Energy bands and electrical properties of metals newPraveen Vaidya
The chapter gives brief knowledge about formation of bands in solids. What are free electrons how they contribute for conductivity in conductors, but can be extended to semiconductors also.
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.
Monitoring and Managing Anomaly Detection on OpenShift.pdfTosin Akinosho
Monitoring and Managing Anomaly Detection on OpenShift
Overview
Dive into the world of anomaly detection on edge devices with our comprehensive hands-on tutorial. This SlideShare presentation will guide you through the entire process, from data collection and model training to edge deployment and real-time monitoring. Perfect for those looking to implement robust anomaly detection systems on resource-constrained IoT/edge devices.
Key Topics Covered
1. Introduction to Anomaly Detection
- Understand the fundamentals of anomaly detection and its importance in identifying unusual behavior or failures in systems.
2. Understanding Edge (IoT)
- Learn about edge computing and IoT, and how they enable real-time data processing and decision-making at the source.
3. What is ArgoCD?
- Discover ArgoCD, a declarative, GitOps continuous delivery tool for Kubernetes, and its role in deploying applications on edge devices.
4. Deployment Using ArgoCD for Edge Devices
- Step-by-step guide on deploying anomaly detection models on edge devices using ArgoCD.
5. Introduction to Apache Kafka and S3
- Explore Apache Kafka for real-time data streaming and Amazon S3 for scalable storage solutions.
6. Viewing Kafka Messages in the Data Lake
- Learn how to view and analyze Kafka messages stored in a data lake for better insights.
7. What is Prometheus?
- Get to know Prometheus, an open-source monitoring and alerting toolkit, and its application in monitoring edge devices.
8. Monitoring Application Metrics with Prometheus
- Detailed instructions on setting up Prometheus to monitor the performance and health of your anomaly detection system.
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Choosing The Best AWS Service For Your Website + API.pptx
6933.laser p pts
1. LASER
LASER stands for ‘Light Amplification by Stimulated Emission of Radiation’
Laser is a very intense, concentrated, highly parallel and monochromatic
beam of light.
Coherence is very important property of Laser.
Incoherent Light:
The light emitted from the Sun or other ordinary light sources such as
tungsten filament and fluorescent tube lights is spread over a wide range of
frequencies.
For eg. Sunlight is spread over Infra Red, Visible light and Ultra Violet
spectrum. So, the amount of energy available at a particular frequency is
very less and hence less intense.
Such light is irregular and mixed of different frequencies, directions and
durations, and is incoherent.
Incoherent light is due to spontaneous and random emission of photons by
the atoms in excited state. These photons will not be in phase with each
other.
Incoherent Light
2. Coherent Light:
Coherent light is uniform in frequency, amplitude, continuity and constant
initial phase difference.
Coherent beam of light is obtained due to stimulated emission of photons
from the atoms jumping from meta-stable state to lower energy state.
Coherent Light
Various Atomic Interactions related to LASER:
a) Induced Absorption:
Photons of suitable size (energy) are supplied to the atoms in the ground
state. These atoms absorb the supplied energy and go to the excited or
higher energy state. IF Ei and Ej are energies of ground state (lower
energy) and excited state (higher energy), then the frequency of required
photon for absorption is
Ej - Ei where ‘h’ is Planck’s constant
ν=
h Atom
E1 E1
E0 E0
Atom hν
Before absorption After absorption
3. b) Spontaneous Emission:
An excited atom can stay in the higher energy state only for the time of 10-8 s.
After this time, it returns back to the lower energy state by emitting a photon
of energy hν = E1 – E0. This emission is called ‘spontaneous emission’.
During spontaneous emission, photons are emitted randomly and hence they
will not be in phase with each other. Therefore, the beam of light emitted is
incoherent.
Atom
E1
E0
Before emission
E1
hν
E0
Atom
After emission
4. c) Stimulated Emission:
When photon of suitable size (energy) is showered (made to fall) on an
excited atom in the higher energy state, the atom falls back to the ground
state by emitting a photon of energy hν = E1 – E0 which is in phase with the
stimulating (incident) photon.
Thus, it results in the appearance of one additional photon. This process is
called ‘stimulated or induced emission’.
Atom
E1
hν
E0
Before emission
E1
hν hν
hν
Atom E0
After emission
5. Absorption
E
2 E =E +hν
2 1
E - E = ΔE = h ν
2 1
E
1
The probability of occurrence of this absorption from state 1 to
state 2 is proportional to the energy density u(ν) of the radiation
P12 = B12 u(ν)
Where Proportionality constant B12 is known as Einstein coefficient
of absorption of radiation
6. Spontaneous Emission
The probability of occurrence of spontaneous emission transition
from state 2 to state 1 depends only on the properties of states
2 and 1 and is given by
P΄21 = A21
Where proportionality constant A21 is known as Einstein coefficient
of spontaneous emission of radiation.
7. Stimulated Emission
E - E = ΔE = h ν
2 1
The probability of occurrence of stimulated emission transition
from the upper level 2 to the lower level 1 is proportional to the
energy density u(ν) of the radiation and is expressed as
P΄΄21 = B21 u(ν)
Where proportionality constant B21 is known as Einstein coefficient
7
of stimulated emission of radiation.
8. Total Probability of emission of transition from
upper level 2 to the lower level 1 is given by
P21 = P΄21 + P΄΄21
Or
P21 = A21 + B21 u(ν)
9. Relation between Einstein’s Coefficients
Let N1 and N2 be the number of atoms at any instant at any
instant in the state 1 and 2, respectively. The probability of
absorption for number of atoms from state 1 to 2 per unit
time is given by
N1P12= N1B12 u(ν)
The total probability of transition for number of atoms
from state 2 to 1, either by spontaneous or by stimulated
emission per unit time is given by
N2P21=N2[A21+B21 u(ν)]
10. In thermal equilibrium at temperature T, the absorption
and emission probabilities are equal
N1P12= N2P21
N 2 A21
u( )
N1 B12 N 2 B21
A21
u( )
N1
B21 1
N2
But according to Einstein
B12 = B21 u( )
A21 1
B21 N1
1
N2
11. According to Boltzmann’s law, the distribution of atoms
among the energy states E1 and E2 at the thermal
equilibrium at temperature T is given by
E1
kT E 2 E1
N1 e kT
E2
e
N2 kT
e
h
N1 kT
e
N2
where k is Boltzmann constant
A21 1
u( ) h
B21 kT
e 1
12. Plank’s radiation formula yields energy density of radiation
3
8 h 1
u( )
c3 h
kT
e 1
Relation Between Einstein Coefficients A and B
3
A21 8 h That is B21/A21 is inversely
3 proportional to frequency of the
B21 c resonant radiation. Therefore,
higher the frequency smaller is
3 the value of B21.That is, it is
B21 c 1 comparatively difficult to obtain
3 the stimulated emission of higher
A21 8 h frequencies.
13. Background Physics
• In 1917 Einstein predicted that:
under certain circumstances a photon
incident upon a material can generate a
second photon of
Exactly the same energy (frequency)
Phase
Polarisation
Direction of propagation
In other word, a coherent beam
resulted.
15. Background Physics
• In a system, all three mechanisms occur.
• However the stimulated emission is very very
sluggish compared to the spontaneous emission
• We need to have a much stimulated emission as
possible for lasing action
16. d) Population Inversion and Optical Pumping:
Usually , the number of atoms in the lower energy state is more than that in
the excited state. According to Boltzmann, the ratio of atoms in the energy
states j and i at a temperature T is given by
N2 e – E2 / kT – (E – E ) / kT
= = e 2 1
N1 e – E1 / kT
For population inversion : N2 > N1 i.e.
N2 E2 E1
1 1 1
N1 k BT
E2 E1 E2 E1
exp 1 0
k BT k BT
E2 E1 E
1 higher terms 1 <0
k BT k BT
Here; ΔE is +ve quantity, kB is also +ve quantity, The only option left is T is –ve, it means the
population is inverted or we have achieved the population inversion.
17. The rate of stimulated Absorption of photons is given by
Ra = N1P12 = N1B12u(ν) and
The rate of stimulated emission of photons is given by
Rste = N2P21 = N2B21u(ν) Rste N2
Since B12= B21, therefore Ra N1
That is, if N2 > N1, the rate of stimulated emission is more than the rate of
stimulated absorption. This results in the increase of u(ν) and hence amplification
of light becomes possible. The state of the matter radiation system in which N2>N1
called Population inversion.
To emit photons which are coherent (in same phase), the number of
atoms in the higher energy state must be greater than that in the ground
state (lower energy).
The process of making population of atoms in the higher energy state
more than that in the lower energy state is known as ‘population
inversion’.
The method by which a population inversion is achieved is called
‘pumping’. In this process atoms are raised to an excited state by
injecting into system photon of frequency different from the stimulating
frequency.
Population inversion can be understood with the help of 3-energy level
atomic systems.
18. E2 Excited State
E1 Meta Stable State
E0 Ground State
Atoms
Atoms
E2 Excited State
hν
E1 Meta Stable State
hν
hν
E0 Ground State
Pumping
E2 E2
E1 E1
Atoms hν’
Atoms hν’
E0 E0 hν’
Rapid fall after 10-8 s After Stimulated Emission hν’
hν’
19. N0
N1
Thermal Equilibrium
N2
E0 E1 E2
N1
Thermal Equilibrium
N2
N0
Population Inversion
Key: Bar represents the E0 E1 E2
Population Inversion
population of atoms
20. The atoms by induced absorption reach excited state E2 from E0. They stay
there only for 10-8 seconds.
After this time they fall to meta-stable state where they stay for quite a
longer time (10-3 seconds). Within this longer time more number of atoms
get collected in the meta-stable state which is large than that at lower energy
level.Thus population inversion is achieved.
In atomic systems such as chromium, neon, etc, meta-stable states exist.
Three Components of Laser Devices:
1. The Pump: It is an external source which supplies energy to obtain
population inversion. The pump can be optical, electrical or thermal.
In Ruby Laser, we use optical pumping and in He - Ne Laser, we use electric
discharge pumping.
2. The Laser Medium: It is material in which the laser action is made to take
place. It may be solid, liquid or gas. The very important characteristic
requirement for the medium is that inversion should be possible in it.
3. The Resonator: It consists of a pair of plane or spherical mirrors having
common principal axis. The reflection coefficient of one of the mirrors is
very near to 1 and that of the other is kept less than 1. The resonator is
basically a feed-back device, that directs the photons back and forth through
the laser medium.
21. LASER COMPONENTS
Optical Resonator
Output
Beam
Active
Medium
High Reflectance Half silvered Mirror
Mirror (HR)
Excitation Mechanism
Or pump
22. Three Components of Laser Devices:
1. The Pump:
I. It is an external source which supplies energy to obtain
population inversion. The pump can be optical, electrical
or thermal. In Ruby Laser, we use optical pumping and in
He - Ne Laser, we use electric discharge pumping.
II. The energy supplied by the pump excites the atoms to
higher energy levels and through spontaneous emission
of through non-radiative processes the population
inversion occurs.
III.The lifetime of the metastable energy state, in which
population inversion occurs must be very large as
compared to the normal life time of the excited atom in
any other energy state.
22
23. 2. The Laser Medium: It is material in which the laser action
is made to take place. It may be solid, liquid or gas. The
very important characteristic requirement for the medium
is that inversion should be possible in it.
Many lasers are named after the material used.
For Example: The output of Ruby laser is at 694.3 nm
and that of He-Ne laser is at 632.8 nm
and of CO2 laser is at 10.6 μm.
Note: Laser action has been observed in more than half of the
known atoms and laser wavelength may extend from
ultraviolet region to the infra-red region.
The most important charactristic requirement for the laser
Medium is that we should be able to obtain the population
inversion in it. According ot Boltzmann condition if N1 and
N2 be the number of atoms in the energy state E1and E2
24. h
N2 kT
e
N1
Where, hν = E2- E1
Therefore, N2is in general less than N1 . Because of this resion
vigorous pumping may be required for sustaining the population
inversion and so only certain pairs of energy levels with
appropriate lifetime can be inverted.
3. The Resonator: It consists of a pair of plane or spherical
mirrors having common principal axis. The reflection
coefficient of one of the mirrors is very near to 1 and that of the
other is kept less than 1. The resonator is basically a feed-back
device, that directs the photons back and forth through the
laser medium and in the process, the number of photons is
multiplied due to stimulated emission.
25. Principle of Laser:
An atomic system having one or two meta-stable states is chosen.
Normally, the number of atoms in the lower energy state is greater than
that in the meta-stable state.
This population is inverted by a technique known as pumping.
The atoms are made to fall from meta-stable state to lower energy state
and photons are emitted by stimulated emission.
The photons are reflected back and forth in the active medium to excite the
other atoms.
Thus a large number of photons are emitted simultaneously which
possess the same energy, phase and direction. This process is called
‘amplification of light’.
To produce laser beam, the following two conditions must be fulfilled:
1. The meta-stable state should all the time have larger number of atoms than
the number of atoms in lower energy state.
2. The photons emitted due to stimulated emission should stimulate other
atoms to multiply the photons in the active medium.
26. Lasing Action
1. Energy is applied to a medium raising electrons to an unstable
energy level.
2. These atoms spontaneously decay to a relatively long-lived, lower
energy, metastable state.
3. A population inversion is achieved when the majority of atoms have
reached this metastable state.
4. Lasing action occurs when an electron spontaneously returns to its
ground state and produces a photon.
5. it will stimulate the production of another photon of the same
wavelength and resulting in a cascading effect.
6. The highly reflective mirror and partially reflective mirror continue
the reaction by directing photons back through the medium along
the long axis of the laser.
7. The partially reflective mirror allows the transmission of a small
amount of coherent radiation that we observe as the “beam”.
8. Laser radiation will continue as long as energy is applied to the
lasing medium.
27. Lasing Action Diagram
Excited State
Spontaneous
Energy Emission
Metastable State
Introduction
Stimulated
Emission of
Energy
Radiation
Ground State
28. Laser Action or Laser Process
Laser Process can be divided into four steps
E3
Stimulated Spontaneous
Step: 2
Absorption Emission
E2
Pumping
Step: 3 Stimulated
Emission
Step: 1 E1
Step: 4 Spontaneous
Emission
E0
Ground Level Meta Stable
Energy Level
30. Atomic transitions
Almost all electronic transitions that occur in atoms that involve photons
fall into one of three categories:
Stimulated absorption
32. Different Lasers
Classification in number of ways:
1. According to the state of laser medium: Gas,
Liquid and Solid Laser.
2. According to the type of pumping: Flight light,
Chemical Action, and Electric Discharge Lasers
3. According to the nature of output: Pulsed (P) or
Continuous Wave (CW) Lasers
4. Classification on the basis of Spectral region of the
light: Ultra-Violet, Visible or Infra-Red Lasers.
33. Different Types of Lasers
Sr. Name of Laser Wavelength Classification on the basis of
No.
State of Nature of Spectral
Laser Output Region
Medium
1. Nitrogen Laser 337 nm Gas Pulsed Ultra-violet
2. Dye laser 400-700 nm Liquid Pulsed or Visible or
continuous infra-red
wave
3. He-Ne Laser 632.8 nm Gas Pulsed Visible
4. Ruby Laser 694.3 nm Solid continuous Visible
wave
5. CO2 Laser 10.6 μm Gas continuous Infra-red
wave
35. Ruby Laser: Ruby is Synthetic sapphire, aluminum oxide (Al2O3)
doped with Chromium Oxide (Cr2O3)
The ruby laser is used as a pulsed laser, producing red light at 694.3 nm. After receiving a pumping from the
flash tube, the laser light emerges for as long as the excited atoms persist in the ruby rod, which is typically
about a millisecond.
Chromium atom play the active role for laser action and aluminum and oxygen atoms
remain inert
It is a three level laser
43. Diode Laser: Semiconductor laser
Laser Diode is an interesting variant of LED in which its special construction
help to produce stimulated radiation as in laser.
In conventional solid state or gas laser, discrete atomic energy levels are
involved whereas in semiconductor lasers, the transitions are associated with
the energy bands.
In forward biased p-n junction of LED, the higher energy level (conduction
band) is more populated than the lower energy level (valence band), which is
the primary requirement for the population inversion.
When a photon of energy hν = Eg impinges the device, while it is still in the
excited state due to the applied bias, the system is immediately stimulated to
make its transition to the valence band and gives an additional photon of
energy hν which is in phase with the incident photon.
+ Roughened
hν surface
Ec
P
hν N
Optically
hν P flat side
N Laser beam
Ev
-
44.
45. The perpendicular to the plane of the junction are polished. The remaining
sides of the diode are roughened.
When a forward bias is applied, a current flows. Initially at low current, there
is spontaneous emission (as in LED) in all the directions. Further, as the bias
is increased, a threshold current is reached at which the stimulated emission
occurs.
Due to the plane polished surfaces, the stimulated radiation in the plane
perpendicular to the depletion layer builds up due to multiple reflections in
the cavity formed by these surfaces and a highly directional coherent
radiation is emitted.
Diode lasers are low power lasers used as optical light source in optical
communication.
46. Carbon dioxide Laser:
It is one of the earliest high power molecular gas laser that uses
carbon dioxide molecule.
It gives continuous output power above 10 kW.
It is also capable of extremely high power pulse operation.
It consists of discharge tube of size of about 2.5 cm diameter and
5.0 cm is length.
Both ends of the tube are sealed by optically plane and parallel
mirrors, one of them being semi-silvered and other one is fully
silvered.
Exhaust
CO2 : N2 : He = 15 : 15 : 70
CO2 N2 He
Fully Silvered Semi-Silvered
Mirror Power Supply Mirror
48. The CO2 gas laser mixture contain 15% CO2, 15% N2 and 70% He
at a pressure of few mm of Hg.
The CO2 gas laser pumping is achieved with the help of electric
discharge
Energy Transfer
CO2(001)
10.6 μm
CO2(100)
CO2(020)
CO2(010)
Ground State CO2(000)
N2 CO2
49. It is one of the most efficient lasers, capable of
operating at more than 30% efficiency. Hence this
laser is suitable for industrial applications both in
terms of energy efficiency and high output beam;
it is used for welding and cutting.
49
50. Characteristics of Laser Light:
1. Laser light is highly directional.
A laser beam departs from strict plarallelism only because of diffraction
effects. Light from other sources can be made into an approximately
parallel beam by a lens or a mirror, but the beam divergence is much
greater than for laser light.
2. Laser light is highly coherent.
Wave trains for laser light may be several hundred kilometre long.
Interference fringes can be set up by combining two beams that have
followed separate paths whose lengths differ by as much as this amount.
The corresponding coherence length for light from a tungsten filament
lamp or a gas discharge tube is typically considerably less than 1 m.
51. 3. Laser light is highly monochromatic.
Tungsten light, spread over a continuous spectrum, gives us no basis for
comparison. The light from selected lines in a gas discharge tube, however,
can have wavelengths in the visible region that are precise to about 1 part in
106. The sharpness of laser light can easily be thousand times greater, or 1
part in 109.
4. Laser light can be sharply focussed. Flux densities for focussed laser light
of 1015 W cm-2 are readily achieved. An oxyacetylene flame, by contrast, has
a flux density of only 103 W cm-2.
5. Tuning: Some lasers can be used to emit radiation over a range of
wavelengths. Laser tunability leads to applications in photochemistry, high
resolution and Raman spectroscopy.
6. Brightness: The primary characteristic of laser radiation is that lasers have
a higher brightness than any other light source. Brightness is defined as the
power emitted per unit area per unit solid angle.
52. Applications of Laser Light:
1. The smallest lasers used for telephone communication over optical fibres
have as their active medium a semiconducting gallium arsenide crystal
about the size of the pin-head.
2. The lasers are used for laser fusion research. They can generate pulses of
laser light of 10-10 s duration which have a power level of 1014 W.
3. It is used for drilling tiny holes in diamonds for drawing fine wires.
4. It is used in precision surveying.
5. It is used for cutting cloth (50 layers at a time, with no frayed edges).
6. It is used in precise fluid-flow velocity measurements using the Doppler
effect.
7. It is used precise length measurements by interferometry.
8. It is used in the generation of holograms.
9. It is used to measure the x, y and z co-ordinates of a point by laser
interference techniques with a precision of 2 x 10-8 m. It is used in
measuring the dimensions of special three-dimensional gauges which, in
turn are used to check the dimensional accuracy of machine parts.
10. Medical applications: It has been used successfully in the treatment of
detached retinas and cancer. A single pulse of laser beam of duration of a
thousandth of a second only is needed for welding the retina.
53. Applications of Laser Light:
1. Communication: Modulated laser beams are being used for
transmitting messages. Due to high degree of coherence,
the loss of transmitted energy is comparatively much less.
2. Surgery: Laser beam has been used successfully for
bloodless surgery. For Example:
• It can be used to weld the detected retinas. The
Laser beam can be used for drilling the teeth,
removal of tumors, removal of infected cell etc.
• It can further be used fro preventing the tooth decay
by depositing hard materials on the surface of the
tooth.
3. Industry: Laser can be focus into very fine beam, resulting
in raising of temperature to about 1000 K and can be used
for drilling holes and fusing and melting of metals
54. Applications of Laser Light:
4.Measurement of Long Distances: During Apollo flight no 11,
on July 20, 1969, Armstrong and Aldrin planted a previously
designed array of triple prisms on the moon. The laser
beam sent from the earth was reflected from these prisms
and was received on the earth. It enable us to determine the
distance of the moon from the earth with an error within 6
m. Later, experiments lowered the error to within 30 cm.
5. Nuclear Fusion: Laser beam can be used to induce the
nuclear fusion. By concentrating the laser beam to a very
very narrow spot, temperature may rise to about 108 K and
nuclear fusion can occur at this temperature.
6. Scientific Research: Used in Michelson Morley Experiment.
This experiment was conducted to test ether drift.
In this experiment, the beam of two infra-red laser of
slightly different frequencies were obtain by means of a
beam splitter and the beat frequency was determined.
55. Laser Output
Continuous Output (CW) Pulsed Output (P)
Energy (Joules)
Energy (Watts)
Time Time
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.
56. Types of Laser Hazards
1. Eye : Acute exposure of the eye to lasers of certain wavelengths
and power can cause corneal or retinal burns (or both). Chronic
exposure to excessive levels may cause corneal or lenticular
opacities (cataracts) or retinal injury.
2. Skin : Acute exposure to high levels of optical radiation may
cause skin burns; while carcinogenesis may occur for ultraviolet
wavelengths (290-320 nm).
3. Chemical : Some lasers require hazardous or toxic substances
to operate (i.e., chemical dye, Excimer lasers).
4. Electrical : Most lasers utilize high voltages that can be lethal.
5. Fire : The solvents used in dye lasers are flammable. High
voltage pulse or flash lamps may cause ignition. Flammable
materials may be ignited by direct beams or specular reflections
from high power continuous wave (CW) infrared lasers.