“laser”的概念、定义、翻译、参考文献-科学参考

laser

Physics

(light amplification by stimulated emission of radiation) A light amplifier usually used to produce monochromatic coherent radiation in the infrared, visible, and ultraviolet regions of the electromagnetic spectrum.

Nonlaser light sources emit radiation in all directions as a result of the spontaneous emission of photons by thermally excited solids (filament lamps) or electronically excited atoms, ions, or molecules (fluorescent lamps, etc.). The emission accompanies the spontaneous return of the excited species to the ground state and occurs randomly, i.e. the radiation is not coherent. In a laser, the atoms, ions, or molecules are first ‘pumped’ to an excited state and then stimulated to emit photons by collision of a photon of the same energy. This is called stimulated emission. In order to use it, it is first necessary to create a condition in the amplifying medium, called population inversion, in which the majority of the relevant entities are excited. Random emission from one entity can then trigger coherent emission from the others that it passes. In this way amplification is achieved.

The laser amplifier is converted to an oscillator by enclosing the amplifying medium within a resonator. Radiation then introduced along the axis of the resonator is reflected back and forth along its path by a mirror at one end and by a partially transmitting mirror at the other end. Between the mirrors the waves are amplified by stimulated emission. The radiation emerges through the semitransparent mirror at one end as a powerful coherent monochromatic parallel beam of light. The emitted beam is uniquely parallel because waves that do not bounce back and forth between the mirrors quickly escape through the sides of the oscillating medium without amplification.

Some lasers are solid, others are liquid or gas devices. Population inversion can be achieved by optical pumping with flashlights or with other lasers. It can also be achieved by such methods as chemical reactions, discharges in gases, and recombination emission in semiconducting materials (see recombination process).

Lasers have found many uses since their invention in 1960, including laser welding, surgery, holography, printing, optical communications, and the reading of digital information. See also dye laser; four-level laser; free–electron laser.

Laser. A simple ruby laser.

Chemistry

(light amplification by stimulated emission of radiation) A light amplifier (also called an optical maser) usually used to produce monochromatic coherent radiation in the infrared, visible, and ultraviolet regions of the electromagnetic spectrum. Lasers that operate in the X-ray region of the spectrum are also being developed.
Nonlaser light sources emit radiation in all directions as a result of the spontaneous emission of photons by thermally excited solids (filament lamps) or electronically excited atoms, ions, or molecules (fluorescent lamps, etc.). The emission accompanies the spontaneous return of the excited species to the ground state and occurs randomly, i.e. the radiation is not coherent. In a laser, the atoms, ions, or molecules are first ‘pumped’ to an excited state and then stimulated to emit photons by collision of a photon of the same energy. This is called stimulated emission. In order to use it, it is first necessary to create a condition in the amplifying medium, called population inversion, in which the majority of the relevant entities are excited. Random emission from one entity can then trigger coherent emission from the others that it passes. In this way amplification is achieved.
The laser amplifier is converted to an oscillator by enclosing the amplifying medium within a resonator. Radiation then introduced along the axis of the resonator is reflected back and forth along its path by a mirror at one end and by a partially transmitting mirror at the other end. Between the mirrors the waves are amplified by stimulated emission. The radiation emerges through the semitransparent mirror at one end as a powerful coherent monochromatic parallel beam of light. The emitted beam is uniquely parallel because waves that do not bounce back and forth between the mirrors quickly escape through the sides of the oscillating medium without amplification.
Some lasers are solid, others are liquid or gas devices. Population inversion can be achieved by optical pumping with flashlights or with other lasers. It can also be achieved by such methods as chemical reactions and discharges in gases.
Lasers have found many uses since their invention in 1960. In chemistry, their main use has been in the study of photochemical reactions, in the spectroscopic investigation of molecules, and in femtochemistry. See also dye laser; four-level laser; Pockels cell.

Computer

A light source with special properties (principally spectral purity, narrow output beam, and ease of modulation) that make it particularly useful in optical storage devices and some kinds of printer, and also in fibre optics communication systems.

Electronics and Electrical Engineering

Acronym for light amplification by stimulated emission of radiation. A source of monochromatic coherent radiation in the visible, ultraviolet, or infrared regions of the electromagnetic spectrum.
In an atom, an electron can jump from one allowed energy level E₂ to an empty level E₁, accompanied by the absorption or emission of a photon of electromagnetic radiation of the appropriate wavelength, λ, given by Planck’s law:
$| E_{2} - E_{1} | = h ν = \frac{h c}{λ}$
If E₂ exceeds E₁, then emission of radiation occurs. Spontaneous emission occurs when an electron in the atom changes energy level without any specific external stimulus. Stimulated emission occurs in response to excitation by a photon of the same energy as the energy difference, E₂ − E₁. The incident and emitted photons are both in phase: coherent radiation. Laser action is based on the process of stimulated emission. For continued emission of radiation, the number of electrons in the higher energy level E₂ must be greater than the number in the lower level E₁. This state is known as population inversion. Population inversion is a nonequilibrium state, and internal relaxation processes will tend to restore the electron distribution to the thermal equilibrium state. External power must therefore be applied to maintain the inverted population in a laser; for example, applied electromagnetic radiation of a shorter wavelength can excite other electrons into a third energy level above E₂, and this level is then the source of electrons for E₂. For continued stimulated emission, photons of the appropriate wavelength must continually pass through the laser medium. This can be achieved by placing two mirrors, facing each other at each end of the laser region, the distance between them being a whole number of wavelengths: this is a Fabry–Perot cavity, and is resonant at the laser wavelength. Spontaneous and stimulated photons then travel back and forth between the mirrors, stimulating further emission of photons, and building up a high intensity of light. If one of the mirrors is only partly reflecting, this light can be emitted in the form of a high-intensity monochromatic coherent beam or pulse.
Laser action can take place in solid, liquid, and gaseous media. The ruby laser was the first solid laser; population inversion was achieved by light excitation. Gas lasers are excited by a continual electric discharge (see gas discharge tube); population inversion is a result of collisions between the gas particles and high-energy ions and electrons excited by the high voltage, creating the excited glow. Semiconductor lasers are made using forward-biased p-n junctions, the injection of carriers across the junction providing the inverted population.
See also semiconductor laser; maser.
http://www.optique-ingenieur.org/en/courses/OPI_ang_M01_C01/co/OPI_ang_M01_C01_web_1.html An introductory lesson on lasers

Geology and Earth Sciences

An acronym for light amplification by stimulated emission of radiation, a device for emitting a single, intense beam of coherent, monochromatic light (i.e. light at a single wavelength). See also maser.

单词	laser
释义	laser Physics (light amplification by stimulated emission of radiation) A light amplifier usually used to produce monochromatic coherent radiation in the infrared, visible, and ultraviolet regions of the electromagnetic spectrum. Nonlaser light sources emit radiation in all directions as a result of the spontaneous emission of photons by thermally excited solids (filament lamps) or electronically excited atoms, ions, or molecules (fluorescent lamps, etc.). The emission accompanies the spontaneous return of the excited species to the ground state and occurs randomly, i.e. the radiation is not coherent. In a laser, the atoms, ions, or molecules are first ‘pumped’ to an excited state and then stimulated to emit photons by collision of a photon of the same energy. This is called stimulated emission. In order to use it, it is first necessary to create a condition in the amplifying medium, called population inversion, in which the majority of the relevant entities are excited. Random emission from one entity can then trigger coherent emission from the others that it passes. In this way amplification is achieved. The laser amplifier is converted to an oscillator by enclosing the amplifying medium within a resonator. Radiation then introduced along the axis of the resonator is reflected back and forth along its path by a mirror at one end and by a partially transmitting mirror at the other end. Between the mirrors the waves are amplified by stimulated emission. The radiation emerges through the semitransparent mirror at one end as a powerful coherent monochromatic parallel beam of light. The emitted beam is uniquely parallel because waves that do not bounce back and forth between the mirrors quickly escape through the sides of the oscillating medium without amplification. Some lasers are solid, others are liquid or gas devices. Population inversion can be achieved by optical pumping with flashlights or with other lasers. It can also be achieved by such methods as chemical reactions, discharges in gases, and recombination emission in semiconducting materials (see recombination process). Lasers have found many uses since their invention in 1960, including laser welding, surgery, holography, printing, optical communications, and the reading of digital information. See also dye laser; four-level laser; free–electron laser. Laser. A simple ruby laser. Chemistry (light amplification by stimulated emission of radiation) A light amplifier (also called an optical maser) usually used to produce monochromatic coherent radiation in the infrared, visible, and ultraviolet regions of the electromagnetic spectrum. Lasers that operate in the X-ray region of the spectrum are also being developed. Nonlaser light sources emit radiation in all directions as a result of the spontaneous emission of photons by thermally excited solids (filament lamps) or electronically excited atoms, ions, or molecules (fluorescent lamps, etc.). The emission accompanies the spontaneous return of the excited species to the ground state and occurs randomly, i.e. the radiation is not coherent. In a laser, the atoms, ions, or molecules are first ‘pumped’ to an excited state and then stimulated to emit photons by collision of a photon of the same energy. This is called stimulated emission. In order to use it, it is first necessary to create a condition in the amplifying medium, called population inversion, in which the majority of the relevant entities are excited. Random emission from one entity can then trigger coherent emission from the others that it passes. In this way amplification is achieved. The laser amplifier is converted to an oscillator by enclosing the amplifying medium within a resonator. Radiation then introduced along the axis of the resonator is reflected back and forth along its path by a mirror at one end and by a partially transmitting mirror at the other end. Between the mirrors the waves are amplified by stimulated emission. The radiation emerges through the semitransparent mirror at one end as a powerful coherent monochromatic parallel beam of light. The emitted beam is uniquely parallel because waves that do not bounce back and forth between the mirrors quickly escape through the sides of the oscillating medium without amplification. Some lasers are solid, others are liquid or gas devices. Population inversion can be achieved by optical pumping with flashlights or with other lasers. It can also be achieved by such methods as chemical reactions and discharges in gases. Lasers have found many uses since their invention in 1960. In chemistry, their main use has been in the study of photochemical reactions, in the spectroscopic investigation of molecules, and in femtochemistry. See also dye laser; four-level laser; Pockels cell. Computer A light source with special properties (principally spectral purity, narrow output beam, and ease of modulation) that make it particularly useful in optical storage devices and some kinds of printer, and also in fibre optics communication systems. Electronics and Electrical Engineering Acronym for light amplification by stimulated emission of radiation. A source of monochromatic coherent radiation in the visible, ultraviolet, or infrared regions of the electromagnetic spectrum. In an atom, an electron can jump from one allowed energy level E₂ to an empty level E₁, accompanied by the absorption or emission of a photon of electromagnetic radiation of the appropriate wavelength, λ, given by Planck’s law: $\| E_{2} - E_{1} \| = h ν = \frac{h c}{λ}$ If E₂ exceeds E₁, then emission of radiation occurs. Spontaneous emission occurs when an electron in the atom changes energy level without any specific external stimulus. Stimulated emission occurs in response to excitation by a photon of the same energy as the energy difference, E₂ − E₁. The incident and emitted photons are both in phase: coherent radiation. Laser action is based on the process of stimulated emission. For continued emission of radiation, the number of electrons in the higher energy level E₂ must be greater than the number in the lower level E₁. This state is known as population inversion. Population inversion is a nonequilibrium state, and internal relaxation processes will tend to restore the electron distribution to the thermal equilibrium state. External power must therefore be applied to maintain the inverted population in a laser; for example, applied electromagnetic radiation of a shorter wavelength can excite other electrons into a third energy level above E₂, and this level is then the source of electrons for E₂. For continued stimulated emission, photons of the appropriate wavelength must continually pass through the laser medium. This can be achieved by placing two mirrors, facing each other at each end of the laser region, the distance between them being a whole number of wavelengths: this is a Fabry–Perot cavity, and is resonant at the laser wavelength. Spontaneous and stimulated photons then travel back and forth between the mirrors, stimulating further emission of photons, and building up a high intensity of light. If one of the mirrors is only partly reflecting, this light can be emitted in the form of a high-intensity monochromatic coherent beam or pulse. Laser action can take place in solid, liquid, and gaseous media. The ruby laser was the first solid laser; population inversion was achieved by light excitation. Gas lasers are excited by a continual electric discharge (see gas discharge tube); population inversion is a result of collisions between the gas particles and high-energy ions and electrons excited by the high voltage, creating the excited glow. Semiconductor lasers are made using forward-biased p-n junctions, the injection of carriers across the junction providing the inverted population. See also semiconductor laser; maser. http://www.optique-ingenieur.org/en/courses/OPI_ang_M01_C01/co/OPI_ang_M01_C01_web_1.html An introductory lesson on lasers Geology and Earth Sciences An acronym for light amplification by stimulated emission of radiation, a device for emitting a single, intense beam of coherent, monochromatic light (i.e. light at a single wavelength). See also maser.
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