This document provides an introduction to lasers and their applications. It begins with recommended textbooks on the subject, then provides a chart showing the laser spectrum and examples of different laser types and their wavelengths. The remainder of the document discusses the basic components and functioning of lasers, including the gain medium that provides stimulated emission, the pump source to create population inversion, and the optical cavity formed by mirrors. It also provides brief histories of the development of masers and the first ruby laser.
This document discusses laser linewidth and the factors that contribute to it. It provides equations to relate population inversion to gain and laser oscillation threshold. Key points:
- Laser linewidth is not a single sharp frequency due to the Heisenberg uncertainty principle. Energy levels have a lineshape function that represents their width.
- Rate equations describe how stimulated emission and absorption change the population of energy levels over time and relate this to the laser intensity.
- Gain occurs when there is population inversion where more atoms are in the excited state than ground state. The gain coefficient relates how much the optical field is amplified per unit length in the laser medium.
- For lasing to start, the gain must overcome the cavity
This document provides an introduction to lasers and their applications. It begins with recommended textbooks on the subject, then provides a chart showing the laser spectrum and examples of different laser types and their wavelengths. The remainder of the document discusses the basic components and functioning of lasers, including the gain medium that provides stimulated emission, the pump source to create population inversion, and the optical cavity formed by mirrors. It also provides brief histories of the development of masers and the first ruby laser.
This document provides an overview of lasers, including:
1. A definition of a laser as a device that generates light through stimulated emission.
2. Descriptions of the key components and processes that enable laser operation, including population inversion and optical feedback.
3. Examples of common laser applications like CD players, fiber optics, and medical devices.
4. Safety considerations regarding laser hazards and the importance of controls and personal protective equipment when working with lasers.
Gas sensing properties of Nanocrystalline metal oxidesshantanusood
Nanocrystalline metal oxides are commonly used as gas sensor materials. They undergo a change in electrical resistance when exposed to target gases due to interactions between the metal oxide surface and gas molecules. The document discusses how reducing the particle size of metal oxides to the nanoscale allows them to exhibit novel optical and electrical properties not seen in their bulk forms. This is because metastable states that exist only at high temperatures in bulk materials can be accessed at room temperature when the particle size is sufficiently small. Several examples of metal oxides and their sensitivity to different gases in both bulk and nanostructured forms are provided. The mechanism of gas adsorption and sensing is also explained.
The document discusses lasers, including their principle, construction, types, and uses. It begins by explaining that a laser works by stimulating electrons to produce coherent and monochromatic photons through population inversion. The key components of a laser are a pump source to cause excitation, a gain medium such as gas or solid, and an optical resonator with mirrors. Common medical lasers described include CO2, Nd:YAG, diode, and excimer lasers used for procedures like photocoagulation, photodisruption, and photoablation. Industrial and scientific uses as well as laser safety are also covered at a high level.
Laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. It differs from other sources of light in that it emits light coherently, which allows for a high intensity beam with low divergence. The key components are an amplifying medium that can be pumped to invert a population of atoms or molecules to higher energy levels, and an optical resonator formed by two or more mirrors to provide feedback of the light emitted from the amplifying medium. When the population inversion condition is achieved, stimulated emission produces a cascade of photons with the same phase and wavelength.
This chapter discusses the optical properties of phonons in materials. It covers:
1) Optical and acoustic phonons - some interact directly with light, others cause light scattering.
2) Optical excitation of phonons - how phonons contribute to optical properties through the dielectric function.
3) Phonon polaritons - mixed phonon-photon excitations in crystals near resonance frequencies.
4) Light scattering - concepts of Brillouin, Raman, and Rayleigh scattering involving phonons.
5) Coherent Raman spectroscopy - an experimental technique that enhances weak Raman scattering signals.
(1) Photonic band gap (PBG) crystals can manipulate light in the same way semiconductors control electric currents. They prevent light propagation within a photonic band gap through Bragg scattering and defects.
(2) PBG crystals are fabricated by drilling holes in a dielectric material in a periodic lattice. This creates a range of frequencies where light is blocked.
(3) Applications include photonic crystal fibers for endlessly single mode fibers, photonic crystal lasers, filters, and planar waveguides for compact integrated photonic circuits. Future directions include all-optical transistors for terabit routing and quantum computing.
This document discusses laser linewidth and the factors that contribute to it. It provides equations to relate population inversion to gain and laser oscillation threshold. Key points:
- Laser linewidth is not a single sharp frequency due to the Heisenberg uncertainty principle. Energy levels have a lineshape function that represents their width.
- Rate equations describe how stimulated emission and absorption change the population of energy levels over time and relate this to the laser intensity.
- Gain occurs when there is population inversion where more atoms are in the excited state than ground state. The gain coefficient relates how much the optical field is amplified per unit length in the laser medium.
- For lasing to start, the gain must overcome the cavity
This document provides an introduction to lasers and their applications. It begins with recommended textbooks on the subject, then provides a chart showing the laser spectrum and examples of different laser types and their wavelengths. The remainder of the document discusses the basic components and functioning of lasers, including the gain medium that provides stimulated emission, the pump source to create population inversion, and the optical cavity formed by mirrors. It also provides brief histories of the development of masers and the first ruby laser.
This document provides an overview of lasers, including:
1. A definition of a laser as a device that generates light through stimulated emission.
2. Descriptions of the key components and processes that enable laser operation, including population inversion and optical feedback.
3. Examples of common laser applications like CD players, fiber optics, and medical devices.
4. Safety considerations regarding laser hazards and the importance of controls and personal protective equipment when working with lasers.
Gas sensing properties of Nanocrystalline metal oxidesshantanusood
Nanocrystalline metal oxides are commonly used as gas sensor materials. They undergo a change in electrical resistance when exposed to target gases due to interactions between the metal oxide surface and gas molecules. The document discusses how reducing the particle size of metal oxides to the nanoscale allows them to exhibit novel optical and electrical properties not seen in their bulk forms. This is because metastable states that exist only at high temperatures in bulk materials can be accessed at room temperature when the particle size is sufficiently small. Several examples of metal oxides and their sensitivity to different gases in both bulk and nanostructured forms are provided. The mechanism of gas adsorption and sensing is also explained.
The document discusses lasers, including their principle, construction, types, and uses. It begins by explaining that a laser works by stimulating electrons to produce coherent and monochromatic photons through population inversion. The key components of a laser are a pump source to cause excitation, a gain medium such as gas or solid, and an optical resonator with mirrors. Common medical lasers described include CO2, Nd:YAG, diode, and excimer lasers used for procedures like photocoagulation, photodisruption, and photoablation. Industrial and scientific uses as well as laser safety are also covered at a high level.
Laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. It differs from other sources of light in that it emits light coherently, which allows for a high intensity beam with low divergence. The key components are an amplifying medium that can be pumped to invert a population of atoms or molecules to higher energy levels, and an optical resonator formed by two or more mirrors to provide feedback of the light emitted from the amplifying medium. When the population inversion condition is achieved, stimulated emission produces a cascade of photons with the same phase and wavelength.
This chapter discusses the optical properties of phonons in materials. It covers:
1) Optical and acoustic phonons - some interact directly with light, others cause light scattering.
2) Optical excitation of phonons - how phonons contribute to optical properties through the dielectric function.
3) Phonon polaritons - mixed phonon-photon excitations in crystals near resonance frequencies.
4) Light scattering - concepts of Brillouin, Raman, and Rayleigh scattering involving phonons.
5) Coherent Raman spectroscopy - an experimental technique that enhances weak Raman scattering signals.
(1) Photonic band gap (PBG) crystals can manipulate light in the same way semiconductors control electric currents. They prevent light propagation within a photonic band gap through Bragg scattering and defects.
(2) PBG crystals are fabricated by drilling holes in a dielectric material in a periodic lattice. This creates a range of frequencies where light is blocked.
(3) Applications include photonic crystal fibers for endlessly single mode fibers, photonic crystal lasers, filters, and planar waveguides for compact integrated photonic circuits. Future directions include all-optical transistors for terabit routing and quantum computing.
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 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.
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.
Q-switching is a technique used to produce high-power laser pulses. It involves preventing the laser from oscillating to allow the population inversion in the lasing medium to build up to a high level. Then, by suddenly allowing oscillation, all the stored energy is emitted in a single giant pulse with peak power much higher than during normal operation. The pulse duration is typically 10-7 to 10-8 seconds. Q-switching provides a means to drastically increase the laser power output through stimulated emission of a very large number of atoms in the active medium.
This document discusses laser beam characteristics including:
1. Lasers produce monochromatic, coherent beams with high directionality and low divergence.
2. Coherence refers to the correlation between the phases of waves and is measured both temporally and spatially.
3. An example calculates the coherence length and time for a laser beam filtered to have a bandwidth of 10 nm and wavelength of 532 nm.
The document summarizes the key aspects of an Nd:YAG laser. It discusses that the Nd:YAG laser uses neodymium-doped yttrium aluminum garnet as the lasing medium, which emits light at a wavelength of 1.064 micrometers when optically pumped by a flashlamp. It provides details on the laser's construction, which includes an Nd:YAG rod and krypton flashlamp enclosed in an ellipsoidal reflector to focus the pumping light. The document also outlines several common applications of Nd:YAG lasers, such as cutting, welding, medicine, and communications.
This document discusses different modes of laser operation, including continuous wave (CW), pulsed, Q-switching, and mode-locking modes. It describes free running laser pulse mode, where the pulse width is controlled by the pumping pulse. For Q-switching, a device is inserted to make the quality factor vary between minimum and maximum, producing very short, high power pulses. Mode-locking synchronizes multiple cavity modes, resulting in ultrashort intensity spikes spaced by the cavity roundtrip time.
Photonic materials manipulate photons to achieve certain functions. Photonic crystals are a type of photonic material that displays unusual properties in interacting with light due to a periodic modulation of refractive index. They can trap light in cavities and waveguides by creating photonic band gaps that prevent light from propagating in certain directions. Potential applications of photonic crystals include photonic integrated circuits, lasers, sensors, and replacing conventional optical fibers.
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 four wave mixing, a third-order nonlinear optical effect where two optical waves interact in a nonlinear medium to generate two new optical waves. Four wave mixing occurs when three optical waves mix according to the frequency coupling condition that the sum of the frequencies of any two waves equals the sum of the frequencies of the other two waves. It also requires phase matching between the waves. Specific applications of four wave mixing discussed include optical phase conjugation using phase conjugation mirrors, and optical parametric amplification.
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.
Lasers work by stimulating the emission of photons from excited atoms or molecules in an active medium placed within an optical cavity formed by mirrors. When photons emitted through stimulated emission are reflected multiple times within the cavity, they cause additional atoms to emit photons coherently, producing a very intense and directional beam of highly monochromatic light. Lasers have applications in welding, cutting, holography, medicine, and more due to their unique properties of coherence, directionality, intensity, and monochromaticity.
The document discusses the principles and applications of femtosecond lasers. It begins by introducing lasers and their properties such as monochromaticity, directionality, and coherence. It then discusses femtosecond lasers specifically, noting that they have pulse durations in the femtosecond range which reduces collateral tissue damage. Mode-locking allows lasers to generate femtosecond pulses by phase-locking multiple longitudinal modes simultaneously. The document covers topics such as mode-locked lasers, pulse duration, time-frequency relationships, group velocity dispersion, and methods of passive and active mode-locking.
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.
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.
Laser science is principally concerned with quantum electronics, laser construction, optical cavity design, the physics of producing a population inversion in laser media, and the temporal evolution of the light field in the laser. It is also concerned with the physics of laser beam propagation, particularly the physics of Gaussian beams, with laser applications, and with associated fields such as non-linear optics and quantum optics.
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.
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 laser applications in optical communication and optical fibers. It describes how light is guided through optical fibers via total internal reflection. Key fiber optic concepts are explained, including core, cladding, numerical aperture, single mode vs multimode fibers, and mode field diameter. Examples of calculations for number of fiber modes and single mode fiber radius are provided.
1. A gas is compressed from 6.0 L to 4.0 L at a constant temperature of 5.0 atm. The work done on the gas is +30 liter atm.
2. A system's internal energy increases by 80 J when 50 J of work is done on it. The heat change of the system is +30 J.
3. A refrigerator operates in a cyclic and reversible manner between 0°C inside and 27°C outside. If it absorbs 334.72x103 J from the inside, the heat rejected outside is 340 J.
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 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.
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.
Q-switching is a technique used to produce high-power laser pulses. It involves preventing the laser from oscillating to allow the population inversion in the lasing medium to build up to a high level. Then, by suddenly allowing oscillation, all the stored energy is emitted in a single giant pulse with peak power much higher than during normal operation. The pulse duration is typically 10-7 to 10-8 seconds. Q-switching provides a means to drastically increase the laser power output through stimulated emission of a very large number of atoms in the active medium.
This document discusses laser beam characteristics including:
1. Lasers produce monochromatic, coherent beams with high directionality and low divergence.
2. Coherence refers to the correlation between the phases of waves and is measured both temporally and spatially.
3. An example calculates the coherence length and time for a laser beam filtered to have a bandwidth of 10 nm and wavelength of 532 nm.
The document summarizes the key aspects of an Nd:YAG laser. It discusses that the Nd:YAG laser uses neodymium-doped yttrium aluminum garnet as the lasing medium, which emits light at a wavelength of 1.064 micrometers when optically pumped by a flashlamp. It provides details on the laser's construction, which includes an Nd:YAG rod and krypton flashlamp enclosed in an ellipsoidal reflector to focus the pumping light. The document also outlines several common applications of Nd:YAG lasers, such as cutting, welding, medicine, and communications.
This document discusses different modes of laser operation, including continuous wave (CW), pulsed, Q-switching, and mode-locking modes. It describes free running laser pulse mode, where the pulse width is controlled by the pumping pulse. For Q-switching, a device is inserted to make the quality factor vary between minimum and maximum, producing very short, high power pulses. Mode-locking synchronizes multiple cavity modes, resulting in ultrashort intensity spikes spaced by the cavity roundtrip time.
Photonic materials manipulate photons to achieve certain functions. Photonic crystals are a type of photonic material that displays unusual properties in interacting with light due to a periodic modulation of refractive index. They can trap light in cavities and waveguides by creating photonic band gaps that prevent light from propagating in certain directions. Potential applications of photonic crystals include photonic integrated circuits, lasers, sensors, and replacing conventional optical fibers.
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 four wave mixing, a third-order nonlinear optical effect where two optical waves interact in a nonlinear medium to generate two new optical waves. Four wave mixing occurs when three optical waves mix according to the frequency coupling condition that the sum of the frequencies of any two waves equals the sum of the frequencies of the other two waves. It also requires phase matching between the waves. Specific applications of four wave mixing discussed include optical phase conjugation using phase conjugation mirrors, and optical parametric amplification.
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.
Lasers work by stimulating the emission of photons from excited atoms or molecules in an active medium placed within an optical cavity formed by mirrors. When photons emitted through stimulated emission are reflected multiple times within the cavity, they cause additional atoms to emit photons coherently, producing a very intense and directional beam of highly monochromatic light. Lasers have applications in welding, cutting, holography, medicine, and more due to their unique properties of coherence, directionality, intensity, and monochromaticity.
The document discusses the principles and applications of femtosecond lasers. It begins by introducing lasers and their properties such as monochromaticity, directionality, and coherence. It then discusses femtosecond lasers specifically, noting that they have pulse durations in the femtosecond range which reduces collateral tissue damage. Mode-locking allows lasers to generate femtosecond pulses by phase-locking multiple longitudinal modes simultaneously. The document covers topics such as mode-locked lasers, pulse duration, time-frequency relationships, group velocity dispersion, and methods of passive and active mode-locking.
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.
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.
Laser science is principally concerned with quantum electronics, laser construction, optical cavity design, the physics of producing a population inversion in laser media, and the temporal evolution of the light field in the laser. It is also concerned with the physics of laser beam propagation, particularly the physics of Gaussian beams, with laser applications, and with associated fields such as non-linear optics and quantum optics.
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.
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 laser applications in optical communication and optical fibers. It describes how light is guided through optical fibers via total internal reflection. Key fiber optic concepts are explained, including core, cladding, numerical aperture, single mode vs multimode fibers, and mode field diameter. Examples of calculations for number of fiber modes and single mode fiber radius are provided.
1. A gas is compressed from 6.0 L to 4.0 L at a constant temperature of 5.0 atm. The work done on the gas is +30 liter atm.
2. A system's internal energy increases by 80 J when 50 J of work is done on it. The heat change of the system is +30 J.
3. A refrigerator operates in a cyclic and reversible manner between 0°C inside and 27°C outside. If it absorbs 334.72x103 J from the inside, the heat rejected outside is 340 J.
1) This document discusses laser levels and saturation in a two-level system laser. It explains that population inversion is not possible in a purely two-level system through direct pumping alone.
2) The distribution of atoms in the two energy levels of a two-level system at thermal equilibrium is described by Boltzmann's law. As temperature increases, the population of the higher energy level approaches but can never exceed that of the lower level.
3) Equations are presented showing that at steady state in a two-level system, the population of the excited state cannot exceed 50% of the total population. Gain saturation is also discussed, where the gain of the laser medium becomes limited at higher intensities.
1. This document discusses thermodynamics concepts related to heat engines and refrigerators. It provides example calculations for efficiency of different heat engines like Stirling engines and Carnot engines.
2. Multiple choice questions are provided related to efficiency, heat transfer, temperature of hot/cold reservoirs in Carnot engines and refrigerators operating on Carnot cycle.
3. Formulas for efficiency of different heat engines and refrigerators are given along with sample calculations.
The document discusses different types of lasers including ruby, neodymium, and titanium-sapphire lasers. Ruby was the first successful laser developed by Maiman in 1960 using a ruby crystal doped with chromium ions as the active medium. Neodymium lasers replaced ruby lasers due to higher efficiency and ability to operate continuously, with neodymium commonly doped in yttrium aluminum garnet crystals. Titanium-sapphire lasers provide tunable output across the visible and near-infrared spectrum and are commonly optically pumped by other lasers such as argon ion lasers.
This document discusses various applications of lasers for optical alignment and tooling. It explains that lasers provide higher brightness than conventional light sources, making them visible from long distances. Both helium-neon and semiconductor diode lasers have been used for tooling applications such as determining displacement and establishing angles. Laser tooling requires only one operator and provides more consistent measurements between operators compared to conventional optical tooling.
The document provides examples and problems related to thermodynamics. Example 1 involves calculating the final temperature of a system consisting of a brass block and ice water. Example 2 calculates the root mean square speeds of nitrogen and oxygen molecules in air. Example 3 determines the new temperature of an ideal gas that is compressed.
This document discusses different types of lasers categorized by their gain medium. It provides details on atomic gas lasers like helium-neon lasers and ion gas lasers like argon ion lasers. Helium-neon lasers use a mixture of helium and neon gases as the gain medium, with the helium assisting in the population inversion process to allow lasing from neon. Argon ion lasers use argon gas that is ionized, with the argon ions providing the lasing transition. Excimer lasers use excimer or exciplex molecules as the gain medium, which only exist in excited states and allow efficient population inversion.
Ideal gases approximate the behavior of real gases at low pressures and densities. The kinetic theory of gases describes ideal gases as large numbers of tiny particles that move freely and undergo elastic collisions. The kinetic theory assumptions lead to simple relationships between pressure, volume, temperature, and number of moles or particles for ideal gases. The van der Waals equation accounts for the finite size of gas particles and their intermolecular attractions, better describing the behavior of real gases that deviate from ideal gas behavior at high pressures and low temperatures.
Thermodynamics is the study of heat, work, and energy. It describes macroscopic properties of systems in thermal equilibrium. A system is defined along with its surroundings and properties. Systems can be open, closed, or isolated. Thermodynamic properties include extensive properties that depend on system size and intensive properties that do not. The four laws of thermodynamics relate temperature, heat, work, and energy within a system. Heat transfer and phase changes involve latent heat in addition to specific heat.
The document discusses Gibbs free energy (G), which is a measure of the useful energy in a chemical reaction. A reaction will occur spontaneously if G decreases. G is defined as enthalpy (H) minus temperature (T) multiplied by entropy (S). The Gibbs free energy change (ΔG) for a reaction determines whether it is spontaneous or not. If ΔG is negative, the reaction proceeds spontaneously, and if ΔG is positive or zero, the reaction is at equilibrium or non-spontaneous. The Clapeyron equation relates the change in vapor pressure of a substance to temperature and can be used to calculate phase diagrams.
The document provides information about various physics concepts related to atomic structure:
1) It defines the photoelectric effect and gives the formula for maximum kinetic energy of photoelectrons.
2) It discusses atomic spectra and the Rydberg formula for calculating wavelengths of emitted/absorbed photons. It also defines various atomic spectral series.
3) It summarizes Rutherford's atomic model and its limitations, as well as concepts like isotopes, isotones, isobars, radioactive decay, and the functions of moderators and coolants in nuclear reactors.
Lecture 14 on Blackbody Radiation.pptxTheObserver3
1) The document summarizes a physics lecture about blackbody radiation and the early development of quantum mechanics. It describes Max Planck's solution to the ultraviolet catastrophe by proposing that (2) the energy of electromagnetic waves is quantized in units of hf, where h is Planck's constant, and (3) the energy levels of atoms are also quantized. This led to Planck's formula for blackbody radiation spectrum, which fit experimental data and avoided the ultraviolet catastrophe.
Electro magnetic radiation principles.pdfssusera1eccd
The document discusses principles of electromagnetic radiation relevant to remote sensing. It describes how energy from the sun interacts with the atmosphere and earth's surface, and is then detected by remote sensors. It explains that electromagnetic radiation can be modeled as waves or particles. The wave model describes properties like wavelength and frequency, while the particle model describes radiation as photons with energy proportional to frequency. The document also outlines the electromagnetic spectrum and different processes involved in electromagnetic radiation like reflection, refraction, and scattering in the atmosphere.
3.1 Discovery of the X Ray and the Electron
3.2 Determination of Electron Charge
3.3 Line Spectra
3.4 Quantization
3.5 Blackbody Radiation
3.6 Photoelectric Effect
3.7 X-Ray Production
3.8 Compton Effect
3.9 Pair Production and Annihilation
This document describes the ATTA (Atom Trap Trace Analysis) experiment which aims to precisely measure trace amounts of krypton isotopes in liquid xenon. ATTA uses laser cooling and trapping techniques to isolate and count individual atoms. The document outlines the ATTA system, which involves exciting atoms to a metastable state using a plasma source, slowing and collimating atoms using optical molasses and Zeeman slowing, and finally trapping atoms using magneto-optical traps. Precisely measuring krypton contamination levels in xenon is important for the larger XENON dark matter detection experiment to understand background signals and increase sensitivity to detect weakly interacting massive particles (WIMPs).
1. Bohr's model of the atom describes electrons orbiting the nucleus in fixed, quantized energy levels.
2. Light is emitted when an electron moves from a higher to lower energy level, with frequency determined by Planck's equation.
3. Hydrogen emits a line spectrum due to its quantized energy levels. The Rydberg equation calculates wavelengths from transitions between levels in Lyman, Balmer, Paschen, Brackett, and Pfund series.
This document discusses electromagnetic radiation and the wave-particle duality of light. It explains that electromagnetic radiation travels as waves with characteristics of wavelength and frequency. The energy of individual photons is related to their frequency by Planck's constant. Electrons in atoms can only occupy certain allowed energy levels, absorbing or emitting photons of specific frequencies as they transition between levels. This explains atomic emission spectra and helped develop the theories of quantum mechanics.
The document discusses the Compton effect, which describes the scattering of photons by charged particles like electrons. It provides the mathematical description using conservation of energy and momentum. The Compton effect leads to a shift in the wavelength of scattered photons. Practical applications of the Compton effect include Compton scatter densitometry to measure electron density, Compton scatter imaging for 3D electron density mapping, and Compton profile analysis to characterize materials.
Med.physics dr. ismail atomic and nuclear physics Ismail Syed
This document discusses various topics in nuclear and atomic physics including:
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Laser lecture01
1. 14/06/2015
1
6/14/20151
412 PHYS
Lasers and their
Applications
Department of Physics
Faculty of Science
Jazan University
KSA
Lecture-1
6/14/20152
Recommended texts
The lectures and notes should give you a good base from which to start your
study of the subject. However, you will need to do some further reading. The
following books are at about the right level, and contain sections on almost
everything that we will cover:
1. “Principles of Lasers,” Orazio Svelto, fourth edition,
Plenum Press.
2. “Lasers and Electro-Optics: Fundamentals and
Engineering,”Christopher Davies Cambridge University
Press.
3. “Laser Fundamentals,” William Silfvast, Cambridge
University Press.
4. “Lasers,” Anthony Siegman, University Science Books.
2. 14/06/2015
2
LASER SPECTRUM
10-13 10-12 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 1 10 102
LASERS
200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 10600
Ultraviolet Visible Near Infrared Far Infrared
Gamma Rays X-Rays Ultra- Visible Infrared Micro- Radar TV Radio
violet waves waves waves waves
Wavelength (m)
Wavelength (nm)
Nd:YAG
1064
GaAs
905
HeNe
633
Ar
488/515
CO2
10600
XeCl
308
KrF
248
2w
Nd:YAG
532
Retinal Hazard Region
ArF
193
Communication
Diode
1550
Ruby
694
Alexandrite
755
6/14/2015
6/14/20154
Introduction (Brief history of laser)
The laser is essentially an optical amplifier. The word laser is an acronym that stands
for “light amplification by the stimulated emission of radiation”.
The theoretical background of laser action as the basis for an optical amplifier was
made possible by Albert Einstein, as early as 1917, when he first predicted the
existence of a new irradiative process called “stimulated emission”.
His theoretical work, however, remained largely unexploited until 1954, when C.H.
Townes and Co-workers developed a microwave amplifier based on stimulated
emission radiation. It was called a MASER
3. 14/06/2015
3
6/14/20155
Others devices followed in rapid succession, each with a different laser
medium and a different wavelength emission.
- In 1960, T.H.Maiman built the first laser device (ruby laser) which
emitted deep red light at a wavelength of 694.3 nm.
- Ali Javan and associates developed the first gas laser (He-Ne
laser), which emitted light in both the infrared (at 1.15mm) and
visible (at 632.8 nm) spectral regions.
6
6. 14/06/2015
6
A laser consists of three parts:
1. A gain medium that can amplify light by means of the basic process of stimulated
emission;
2. A pump source, which creates a population inversion in the gain medium;
3. Two mirrors that form a resonator or optical cavity in which light is trapped,
traveling back and forth between the mirrors.
11 6/14/2015
Brewster Angle Gain region
Examples of Electrical and Optical pumping
12
6/14/2015
Dr. Mohamed Fadhali
Dr. Mohamed Fadhali
7. 14/06/2015
7
Lasers are quantum devices, requiring understanding of the gain medium.
Laser light usually generated from discrete atomic transitions
13
Laser: Light amplification by stimulated emission of radiation
A laser converts electricity or incoherent light to coherent light.
Laser-matter interaction
Is a radiation emitted from a hot body. It's anything but black!
The name comes from the assumption that the body absorbs at every frequency
and hence would look black at low temperature . It results from a combination of
spontaneous emission, stimulated emission, and absorption occurring in a
medium at a given temperature.
It assumes that the box is filled with molecules that, together, have
transitions at every wavelength.
14
Blackbody radiation
8. 14/06/2015
8
(perfect blackbody: reflectivity = trasmissivity = 0
emissivity = absorptivity = 1 )
Model: Assume a hole in large box with reflective interior walls: incident light from ~all
angles will make multiple passes inside box, resulting in thermal equilibrium inside box.
15
Blackbody radiation
Approach:
1. Calculate all possible ways EM radiation ‘fits in the box’
depending on the wavelength (density of states calculation)
2. First (wrongly) assume that each radiation mode has E=KBT/2
energy (this was the approach before the photon was known)
results in paradox
3. Fix this by assuming energy in field can only exist in energy
quanta & apply Maxwell-Boltzmann statistics problem solved
For three dimensional case, and taking cavity with dimensions a×a×a →(V = a3),
we find allowed modes with equally spaced k values
We can now calculate the density of states as a function of several parameters,
e.g. number of states within a k-vector interval dk.
Each allowed k-vector occupies volume k in k-space (reciprocal space):
3
3x y zk k k k
a a a a
16
ALLOWED MODES AND DENSITY OF STATES
9. 14/06/2015
9
Number of k-vectors in k range of magnitude dk depends on k:
In two dimensions: number of allowed
k-vectors goes up linearly with k
In three dimensions: number of allowed
k-vectors goes up quadratically with k
width dk
17
Mode density
volume 1/8 sphere = Vs
33
1 4 1 4 2
8 3 8 3
s
k n
V
c
Number of modes in this volume = 2 × Vs / k and k = (/a)3
3
3
33
3
3
3
33
3
8
3
4
2
2
3
4
8
1
2
a
c
n
a
c
n
a
c
n
N
The mode density (modes per unit volume) in frequency range d becomes
With the group index, which we set as ngn
Mode density
10. 14/06/2015
10
Classically (e.g. in gases), it was known that each degree of freedom had E = KBT/2
(e.g. atom moving freely: three degrees of freedom: E=3/2 KBT.
Applying this to the calculated mode density gives (incorrectly!) the energy density:
This gives rise to the Ultraviolet catastrophe
6/14/2015
0 2
0
2x10
7
4x10
7
6x10
7
8x10
7
1x10
8
T = 5000 K
T = 6000 K
T = 3000 K
SpectralRadianceExitance
(W/m
2
-mm)
Wavelength (mm)
M = T
Cosmic black body background
radiation, T = 3K.
Rayleigh-Jeans
law
6/14/2015
11. 14/06/2015
11
one photon energy × probability of
having 1 photon present in mode
two photons × probability of
having 2 photons present in mode
normalization factor
The effect of energy quantization
* Analytical solution for blackbody radiation
The equation for energy per mode can be solved analytically:
Giving the following energy density inside the cavity at a given frequency :
This is the Planck blackbody radiation formula
6/14/2015
HW: Prove that?
12. 14/06/2015
12
Short wavelength behavior:
Result of quantum nature of light
mode density thermal population
6/14/2015
23
Blackbody Radiation
• (Stimulated) Absorption
• Spontaneous Emission
• Stimulated Emission
All light-matter interactions can be described by one of three
quantum mechanical processes:
…We will now look at each.
6/14/201524
Fundamentals of Light-Matter Interactions
13. 14/06/2015
13
Interaction of Radiation with Atoms and Molecules:
The Two-Level System
The concept of stimulated emission was first developed by Albert Einstein
from thermodynamic considerations. Consider a system comprised of a two-
level atom and a blackbody radiation field, both at temperature T.
6/14/201525
This is, of
course,
absorption.
Energy
Ground level
Excited level
Absorption lines in an
otherwise continuous
light spectrum due to a
cold atomic gas in front
of a hot source.
Atoms and molecules can also absorb photons, making a
transition from a lower level to a more excited one
14. 14/06/2015
14
When an atom in an excited state falls to a lower energy level, it emits a
photon of light.
Molecules typically remain excited for no longer than a few nanoseconds.
This is often also called fluorescence or, when it takes longer,
phosphorescence.
Energy
Ground level
Excited level
Excited atoms emit photons spontaneously
Ni is the number density of
molecules in state i (i.e.,
the number of molecules
per cm3).
T is the temperature, and
kB Boltzmann’s constant
= 1.38x10-16 erg / degree
= 1.38x10-23 j/K
exp /i i BN E k T
Energy
Population density
N1
N3
N2
E3
E1
E2
28
In what energy levels do molecules reside?
Boltzmann population factors
15. 14/06/2015
15
*
In the absence of collisions, molecules
tend to remain in the lowest energy state
available.
Collisions can knock a molecule
into a higher-energy state.
The higher the temperature,
the more this happens.
22
1 1
exp /
exp /
B
B
E k TN
N E k T
Low T High T
Energy
Energy
Molecules
3
2
1
2
1
3
Boltzmann Population Factors
2
1
Calculating the gain: Einstein A and B coefficients
Recall the various processes that occur in the laser medium:
Absorption rate = B N1 r()
Spontaneous emission rate = A N2
Stimulated emission rate = B N2 r()
16. 14/06/2015
16
Interaction of Radiation with Atoms and Molecules:
The Two-Level System
The processes of spontaneous emission and (stimulated) absorption were well
known. Einstein had to postulate a new process, stimulated emission in
order for thermodynamic equilibrium to be established.
2
1
Spontaneous
Emission
Stimulated
Absorption
Stimulated
Emission
2 21N A
2 21 2 21 ( )N W N B r 1 12 1 12 ( )N W N B r
3
( ) . /J s mr
From thermodynamic equilibrium
3
2 21 2 21 1 12( ) ( ) ( ) . /N A N B N B J s mr r r
Units of B must be consistent with units of r() units of A are sec-1.
Absorption calculations are best done using A to avoid confusion on units.
3 3
3
8 1
( )
1
h
k TB
hn
c e
r
2 1( )
2 2
1 1
B
E E
K TN g
e
N g
and
3 3
21 21 2 21 1 123
8
,
hn
A B g B g B
c
2 21 2 21 1 12N A N W N W
HW: How to
reach to this
expression ???
17. 14/06/2015
17
Absorption, emission, amplification depend on number of atoms in various states
Define concentration of atoms in state 2 as N2 (units often cm-3)
To find N1(t) and N2(t), you need to model time dependence of all processes
Process 1: spontaneous emission
Chance of spontaneous emission per unit time is A (Einstein coefficient)
If there are N2 atoms excited per volume, then at later time t we will have less, or
2 2
2
spsp
dN N
AN
dt
2 2N A t N
In differential form this becomes a rate equation of the form
where A is the rate constant for spontaneous emission and sp is the
life time for spontaneous emission given by sp=1/A
33
Rate equations: spontaneous emission
Suppose you can bring atoms in the excited state by some energy input
look at time dependence of N2 after the energy input is turned off at t=0:
( ) ( ) /2 2
2 2 0 spt
spsp
dN N
N t N e
dt
Note that the N2 drops to 1/e of its original
value when t=sp.
We have solved our first rate equation to
calculate the time dependent
concentration of excited atoms
6/14/201534
Rate equations: spontaneous emission
18. 14/06/2015
18
2
2 21 ( )
st
dN
N B
dt
r
B21 is the Einstein coefficient for stimulated emission
Under monochromatic illumination at frequency we can write this as
2
2 21( )
st
IdN
N
dt h
Rate equations – Stimulated emission
More complex situations, add more processes to the rate equations
Scales with the electromagnetic spectral energy density r()
where r()d is the energy per unit volume in the frequency range {, +d }
Process 2: Stimulated emission
with I /(h ) is the photon flux given and 21() the cross section for stimulated emission
Note that ()I /(h ) is the rate constant for stimulated emission (units again s-1)
Process 3: Absorption
for absorption (‘stimulated absorption’) we obtain a similar rate
equation:
2
1 12 1 12( ) ( )
abs
IdN
N B N
dt h
r
with B12 the Einstein coefficient for absorption
and 12 the absorption cross section
6/14/201536
Rate equations – Absorption
19. 14/06/2015
19
We now have the rate equations describing the population of levels 1 and 2
Population is the ‘amount of occupation’ of the different energy levels
2
1 12 2 21 2( ) ( )
dN
N B N B AN
dt
r r
1
1 12 2 21 2( ) ( )
dN
N B N B AN
dt
r r
Since we have only two states, we find
(atoms that leave state 2 must end up in state 1)
N1 and N2 should add up to the total amount of atoms: N1+N2=N
We can now solve the time dependent population N2 under illumination
Before doing that, let’s look at the relations between A, B12, and B21
dt
dN
dt
dN 21
Rate equations for two-level system
Hypothetical situation: closed system at temperature T with collection of
two-level atoms and no external illumination:
All processes together will result in a thermal equilibrium with a
population distribution described by a Boltzmann factor:
/2
1
Bh k TN
e
N
In equilibrium, on average 021
dt
dN
dt
dN
This implies that in equilibrium
2 12
1 21
( )
( )
B
h
k TN B
e
N A B
r
r
1 12 2 21 2( ) ( ) 0N B N B ANr r
Resulting in an equation relating the Einstein coefficients to the thermal distribution:
6/14/201538
Einstein coefficients in thermal equilibrium
20. 14/06/2015
20
2 12 12 12
12 21
( )
1 21 21 21
( ) ( )
1
( ) ( )
B
h
k T
T
N B B B
e B B B
N A B A B B
r r
r r
1
2
2 2
12 1 21 2 1 2
1
( )
1N
N
AN NA A
B N B N B N N B
r
1
( )
1
h
k TB
A
B e
r
Conversely, we can derive the ‘emission spectrum’ from our two-level atom
Substituting the thermal distribution over the available energy levels we obtain
which looks very similar to the Planck blackbody radiation formula :
3 3
3
8 1
( )
1
h
k TB
hn
c e
r
3 3 3
3 3
8 8A hn hn
B c
implying
At high temperatures e-h /k
B
T →1, and the radiation density becomes large:
Ratio between rates of spontaneous and stimulated emission
21 21
21 21
1
( )
h
k TB
A A
e
W B
r
21. 14/06/2015
21
HW. 1
Compare the rates of spontaneous and stimulated emission at room temperature (T
= 300K) for an atomic transition where the frequency associated with the transition
is about 3 × 1010 Hz, which is in the microwave region (KB=1.38 × 1023 J/K)
(b) What will be the wavelength of the line spectrum resulting from the transition of
an electron from an energy level of 40 × 10−20 J to a level of 15 × 10−20 J?
HW. 2
Consider the energy levels E1 and E2 of a two-level system. Determine the
population ratio of the two levels if they are in thermal equilibrium at room
temperature, 27◦C, and the transition frequency associated with this system is
at 1015 Hz
HW. 3
The oscillating wavelengths of the He–Ne, Nd:YAG, andCO2 lasers are 0.6328,
1.06, and 10.6µ m, respectively. Determine the corresponding oscillating
frequencies. What energy is associated with each transition?