187 results about "Population inversion" patented technology

The present invention discloses a laser amplifier with high gain and low thermally induced optical aberrations on the amplified laser beam. The amplifier designs allow simple multipass configurations to optimally extract the gain and reduce thermally induced index of refraction aberrations, making it possible to obtain an amplified laser beam of high quality combined with very high overall gains comparable to those achievable with expensive regenerative amplifiers. The amplifier includes a thin active laser solid to create the population inversion and associated heat generation within the thin laser active solid possible for the desired gain value. The system includes a cooling device in thermal contact with the thin active laser solid to provide good heat transport and high reflectivity coatings at the wavelengths of the pump and laser wavelengths. The pump light sources are laser diodes tuned to the maximum absorption of the laser active material. The amplifier also includes an optical system to transport the pump light to the laser active solid in such a way as to further confine the absorption of light along the two orthogonal directions in the plane of the laser active solid in order to get high population inversion and consequently high gains possible.

A CS optical pulse train generation method, which is able to change the half width of an optical pulse constituting a CS optical pulse train, and which is compact and has low power consumption. A distributed Bragg reflector semiconductor laser utilized in this method is one which is constituted comprising an optical modulation region, a gain region, a phase control region, and a distributed Bragg reflector region. Current is injected into the gain region by way of a p-side electrode and a n-side common electrode by a constant current source, forming the population inversion required for laser oscillation. Optical modulation required to manifest mode locking is carried out in the optical modulation region. A diffraction grating is formed in the distributed Bragg reflector region. A CS optical pulse train with a repetitive frequency of frep is generated by adjusting the effective indices of both the phase control region and the distributed Bragg reflector region such that, of the longitudinal modes of the mode-locked semiconductor laser diode, the two longitudinal modes close to the frequency f0, which is the Bragg wavelength of the distributed Bragg reflector region converted to a frequency, become f0+(frep / 2) and f0−(frep / 2).

A method for doping semiconductors used for far infrared lasers with non-hydrogenic acceptors having binding energies larger than the energy of the laser photons. Doping of germanium or silicon crystals with beryllium, zinc or copper. A far infrared laser comprising germanium crystals doped with double or triple acceptor dopants permitting the doped laser to be tuned continuously from 1 to 4 terahertz and to operate in continuous mode. A method for operating semiconductor hole population inversion lasers with a closed cycle refrigerator.

A quantum cascade source, such as a QC laser, is provided comprising a plurality of repeat units each including an active region and an injector region. The active region includes at least two quantum wells that, in response to an applied electrical bias, provide a first, second, and third electron energy level, each resulting from a respective quantum well excited state. The first and second energy levels are configured so that an electron transition from the first energy level to the second energy level emits a photon of a selected wavelength. The second and third energy levels are configured so that an electron transition from the second energy level to the third energy level comprises a nonradiative transition to empty the second energy level sufficiently quickly to promote a population inversion between the first and second energy levels.

The invention provides a device and a method for generating an active laser frequency standard based on a four-energy-level quantum system. An air chamber in which a gain medium is filled is formed in a Fabry-Perot cavity, wherein the gain medium is the atomic gas of the four-energy-level quantum system. Pumping laser is emitted into one end of the Fabry-Perot cavity, and the atomic gas is excited from a ground-state energy level to a fourth energy level. Atoms in the fourth energy level are transited to a low energy level through spontaneous radiation, and atom population inversion is realized between a third energy level and a second energy level. The atoms in the third energy level are transited to the second energy level through spontaneous radiation or stimulated radiation photons, stimulated radiation is generated under the action of the Fabry-Perot cavity, and laser is output from the other end of the Fabry-Perot cavity. The active laser frequency standard is high in frequency stability and accuracy.

A nano-scale surface analysis system comprises an electrically powered apparatus for the generation of soft x-ray laser radiation. The apparatus comprises an excitation circuit having at least two or more electrically conducting structures separated by a liquid dielectric for providing a high current excitation pulse, and a capillary structure having a capillary with a length to diameter ration of about 20 to 1000 for enclosing a selected lasing material, wherein the excitation circuit is capable of generating a plasma volume within the capillary structure to produce a population inversion. The generator further comprises a focusing optic for receiving the soft x-ray radiation from the emissions source and focus the soft x-ray radiation onto a target for forming a nanoplasma, the soft x-ray radiation being focused onto an area of the target having a diameter of less than 100 nm.

A laser device using an inorganic electro-luminescent material doped with a rare-earth element is provided. A dielectric layer such as SiO2 is arranged on a silicon substrate. A polycrystalline thin film of Er-doped ZnS or ZnSe is arranged on the dielectric layer. An electrode is formed on the dielectric layer. After a waveguide structure is substantially formed, a reflector is formed at both ends of the waveguide structure to form a laser resonator. An active medium is a polycrystalline material of Er-doped ZnS or ZnSe. When an AC voltage is applied between an electrode attached to the substrate and an electrode attached to an uppermost part, the effect of emitting light at 1550 nm and generating population inversion is used.

The present invention relates to a Q-switching-induced gain-switched erbium pulse laser system, capable of generating erbium laser pulses within the 2.5 μm to 3.0 μm wavelength region, by means of Q-switching operation at 1.6 μm. At first, an Er3+-doped gain medium is pumped and Q-switched at the wavelength region from 1.58 μm to 1.62 μm, so that a Q-switched pulse is formed from the Er3+-doped gain medium. The Q-switched pulse results in an instant positive population inversion between the levels 4I11 / 2 and 4I13 / 2 of the Er3+-doped gain medium, followed by a gain-switched laser pulse at the wavelength region from 2.5 μm to 3.0 μm.

The present invention provides quantum cascade lasers and amplifier that operate in a frequency range of about 1 Terahertz to about 10 Terahertz. In one aspect, a quantum cascade laser of the invention includes a semiconductor heterostructure that provides a plurality of lasing modules connected in series. Each lasing module includes a plurality of quantum well structure that collectively generate at least an upper lasing state, a lower lasing state, and a relaxation state such that the upper and the lower lasing states are separated by an energy corresponding to an optical frequency in a range of about 1 to about 10 Terahertz. The lower lasing state is selectively depopulated via resonant LO-phonon scattering of electrons into the relaxation state.

A phonon maser is comprised of a resonant cavity, a superconductive gain medium, and pumping means. The resonant cavity is comprised of highly reflective means and partially reflective means. The superconductive gain medium is an elongated superconductor, which may be a crystalline high-temperature ceramic superconductor or a single-crystal superconductor. The pumping means provide electromagnetic energy for the superconductive gain medium in order to form and then excite Cooper pairs. Trapped in the resonant cavity and amplified by the population inversion, the resonating bundles of superposed free phonons eventually break through the partially reflective means and enter the vacuum of space in a collimated, coherent, and all-penetrating beam of bundles of superposed guest phonons. This beam changes properties of the ambient space, including its gravitational energy.

The invention discloses a cavity pump light parameter oscillator of single-ended output. The oscillator comprises a laser pump source, a focusing lens, an input coupling mirror, a laser gain crystal, a diachronic mirror, a non-linear crystal, a first curved surface mirror, piezoelectric ceramic arranged on the non-linear crystal and a second curved surface mirror arranged on a reflected light path of the diachronic mirror. The input coupling mirror, the laser gain crystal, the diachronic mirror, the non-linear crystal and the first curved surface mirror form a laser resonant cavity. The first curved surface mirror, the non-linear crystal, the diachronic mirror and the second curved surface mirror form a signal light resonant cavity. The pump source carries out pumping via the focusing lens, population inversion is formed in a gain medium, laser oscillation is formed in the laser resonant cavity, and an oscillated laser generates signal light and forward and backward idle light via the non-linear crystal. Backward idle light is reflected by the second curved surface mirror and then is coupled and output with forward idle light generated by the non-linear crystal via the first curved surface mirror so as to realize single-ended output of intermediate infrared idle light.

The invention discloses a novel orthogonal-polarization dual-wavelength laser which belongs to a novel laser and is a dual-wavelength continuous pulse laser or a dual-wavelength repetition-rate pulse laser realizing mutual orthogonality of a horizontal polarized wavelength 1 and a vertical polarized wavelength 2 in polarization directions by adopting an anisotropic neodymium-doped laser crystal with a multichannel transition property. The laser device comprises the anisotropic neodymium-doped laser crystal, such as Nd:YAlO3, Nd:YVO4, Nd:YLF or Nd:GdVO4 and other crystals, a pumping system and an optical resonant cavity, wherein the pumping system is used for pumping the laser crystal to enable active ions (Nd<3+> ions) in the laser crystal to form distribution for population inversion; the optical resonant cavity is used for the resonation of dual-wavelength radiation of the horizontal polarized wavelength 1 and the vertical polarized wavelength 2 of the active ions in transmission emission; and finally, orthogonal-polarization dual-wavelength laser of the horizontal polarized wavelength 1 and the vertical polarized wavelength 2 are simultaneously outputted in the same light path both by the same output coupling mirror. The orthogonal-polarization dual-wavelength laser provides a novel laser source and a novel technical approach to acquisition of high-power, high-coherence or difference-frequency (THz radiation waves) laser, can broaden the application of dual-wavelength laser, and has a broad application prospect and use values in the fields of non-linearity frequency conversion, fiber-optic communication and the like.

The present invention provides quantum cascade lasers and amplifier that operate in a frequency range of about 1 Terahertz to about 10 Terahertz. In one aspect, a quantum cascade laser of the invention includes a semiconductor heterostructure that provides a plurality of lasing modules connected in series. Each lasing module includes a plurality of quantum well structure that collectively generate at least an upper lasing state, a lower lasing state, and a relaxation state such that the upper and the lower lasing states are separated by an energy corresponding to an optical frequency in a range of about 1 to about 10 Terahertz. The lower lasing state is selectively depopulated via resonant LO-phonon scattering of electrons into the relaxation state.

The invention discloses a terahertz wave amplification device based on optical pumping substrate-free graphene. The terahertz wave amplification device comprises a THz (terahertz) radiation generation device, a THz radiation amplification device and a THz radiation detection device, wherein the three devices share a femtosecond laser through a beam splitter. Incident femtosecond optical pulses are divided into two beams through the beam splitter, wherein one beam is of an optical detection path for entering into the THz radiation detection device, the electro-optic sampling detection principle is utilized for detecting generated and amplified terahertz pulses; the other beam is further divided into two beams, namely Beam 1 and Beam 2 via the other beam splitter; the Beam 1 is of THz generated light, the optical rectification effect is utilized to generate THz radiation on the surface of a nonlinear crystal, and the radiation is irradiated onto the substrate-free graphene via an off-axis parabolic mirror as signal light; and the Beam 2 is of pumping light of the graphene, the substrate-free graphene is stimulated to realize population inversion of a current carrier, and stimulated amplification of the THz radiation is realized on the action of the THz signal light.

The present invention relates to a laser light source having a structure for effectively suppressing generation of an optical surge upon a restart after suspension of output of pulsed light. The laser light source comprises a first light source outputting light with a first wavelength as pulsed light, a second light source outputting light with a second wavelength different from the first wavelength, an optical amplification fiber as an optical amplifier amplifying the pulsed light outputted from the first light source and the light outputted from the second light source, and a control unit controlling the output of the light from the second light source in accordance with the light output from the first light source. The first light source has an ON state in which repetitive output of the pulsed light on a fixed cycle starts and continues, and an OFF state in which the output of the pulsed light is suspended during a duration of not less than the fixed cycle. The control unit controls the second light source to output the light to the optical amplification fiber during the duration of the first light source being in the OFF state, so as to suppress a rise of population inversion of a rare earth element added in the optical amplification fiber.

The invention relates to a method and device for producing an active light clock with a gain medium and a quantum reference medium separated. The device comprises an optical resonant cavity, the quantum reference medium and the population-inversion gain medium, wherein the quantum reference medium and the population-inversion gain medium are located inside the optical resonant cavity and separated from each other in space, and the quantum reference medium is located in a magnetic field. A laser light field produces the Faraday magneto-optical rotation effect on an atomic clock transition spectral line of the quantum reference medium in the outer magnetic field, under the back feeding effect of the optical Fabry-Perot resonant cavity and under the condition that a collimating lens conducts collimation on light beams, the gain medium products stimulated radiation and reaches a laser oscillation threshold, and laser light of the active light clock is formed and output from the output end of the optical resonant cavity. According to the method and the device, the two mediums which are completely independent and separated in space are used for meeting the requirements that the output power of the active light clock is high and the narrow line of the active light clock is wide, and the output laser light has very good frequency stability and accuracy.

The field of the invention is that of solid-state ring lasers or laser gyros. The laser gyro according to the invention comprises at least one optical cavity in the form of a ring and a solid-state amplifying medium which are designed so that two counterpropagating optical modes can propagate in opposite directions one with respect to the other inside said optical cavity and pass through the amplifying medium, said amplifying medium being coupled to an electromechanical device imparting on said amplifying medium a periodic translational movement along an axis substantially parallel to the direction of propagation of said optical modes. Thus, the population inversion grating, written by the standing wave into the amplifying medium, which disturbs the nominal operation of the laser gyro, is greatly attenuated.

The invention discloses 3.7-4.2-micron all-solid-state laser orientated intermediate infrared holmium-neodymium dual-doped laser crystal, and relates to the field of an intermediate infrared laser gain material. In the laser crystal, trivalent holmium ions are used as active ions, and the corresponding energy level transition is Ho3<+>: 5I5-5I6; the trivalent neodymium ions have dual functions, which can be used as the trivalent holmium ion sensitized ions to enable the crystal to be suitable for commercial and high-power LED pumping on one hand; on the other hand, the trivalent holmium ions also can be used as de-activation ions of the trivalent holmium ions to greatly shorten the energy level service life of the lower laser energy level 5I6 of the trivalent holmium ions; meanwhile, the energy level service life of the upper laser energy level 5I5 of the trivalent holmium ions is not changed obviously, so that population inversion can be realized, effective laser output is achieved, and the laser threshold value can be lowered and laser efficiency can be improved; and the laser crystal can be used for 3.7-4.2-micron laser output and has the significant application prospects in the fields of medical treatment, scientific research, military affairs and the like.

The invention discloses a polarization-stable optical fiber laser cascade amplifier, which comprises a laser space isolator for preventing return seed laser from damaging a seed source, the laser space isolator is connected with a first polarizing beam splitter for splitting laser in different directions, the first polarizing beam splitter is connected with a first optical fiber collimator, the first optical fiber collimator is connected with a first combiner, the first combiner is connected with a first gain optical fiber for generating population inversion, the first gain optical fiber is connected with a second optical fiber collimator, the second optical fiber collimator is connected with a Faraday rotator mirror for rotating the laser polarization angle by 45 degrees, the Faraday rotator mirror is connected with a total-reflection mirror for returning incident light along the original path, the pumping input end of the first combiner is connected with a first pumping source, and one reflecting end of the first polarizing beam splitter servers as a polarization-maintaining pulse output end. The polarization-stable optical fiber laser cascade amplifier has the advantage that the polarization-stable optical fiber laser cascade amplifier can always keep the polarization state of amplified and outputted high-power laser stable in the process of amplification.

A system and method for laser light amplification provides amplification of a laser light beam emitted from a laser light source as low-amplification seed laser light signal. The low-amplification seed laser light signal is transmitted to an amplification component. The amplification component amplifies the low-amplification seed laser light signal by stimulating emissions of the population inversion provided by a pumping diode to generate an amplified laser light signal. The system and method further directs the amplified laser light signal to an output destination. The destination may be an object undergoing laser ultrasound testing. The amplified laser light may reflect with a modulation characteristic of a sound energy wave about the object. The reflected laser light may be collected by an interferometer and used in the detection and characterization of the sound energy wave. The result of the present invention is a system and method of operation providing higher pulse rates, improved pointing stability, and optionally variable pulse rates for a variety of uses, including for non-destructive laser ultrasonic testing of materials.

The present invention is to provide an optical fiber amplifier for clamping and equalizing gain in optical communication systems comprising: a gain clamping amplifier unit for clamping the gain, so as to make input signals have the same output power for each channel by applying a compensating signal; a second isolator for passing the input signal light from said gain clamping amplifier unit and isolating the light coming from the opposite direction; a gain equalizing filter for equalizing the output gain spectrum from the input signal from said second isolator; and a post-amplifier unit for amplifying the signal from said gain equalizing filter. Thus, the optical fiber amplifier is capable of clamping gain automatically by maintaining the same population inversion, and capable of maintaining the same gain equalization for the wide signal gain band to achieve the high transmission capacity, in cases that the number of channel varies in the input signal, while providing a high output signal power.

In the basic Diode-Pumped Alkali Laser (DPAL) device, excitation to the n .sup.2P.sub.3 / 2 electronic level by a single diode laser pump source leads to a population inversion between the first excited electronic .sup.2P.sub.1 / 2 level and the ground .sup.2S.sub.1 / 2 level, permitting the construction of efficient, high-power, compact DPAL laser oscillators in the near infrared spectral region. The present invention extends the single-step excitation DPAL to a two-step excitation, or up-conversion DPAL to produce efficient, powerful laser operation in the visible blue and near UV spectral regions (viz., in the range 460-323 nm). The present invention describes an apparatus and method that efficiently sums the energy of two, near-infrared diode pump photons in alkali vapor atoms, followed by stimulated emission to their electronic ground levels.

An apparatus for the crystalline, mass and selective syntheses of diamonds and carbon nanotubes (CNT) includes a chamber having at least one source of carbon and possibly a source of metal on a substrate surface (atoms, clusters and / or nanoparticles); at least one resistance heating element; at least one exciting and heating laser at least one IR source; at least one magnetic field generator; and at least one pressure device. In operation, carbon and metal atoms are supplied to the heated reaction chamber for contacting with substrate supported catalyst, a heating laser beam and an IR source, and then for contacting with an intense magnetic field sufficient amount of interaction between the excited carbon and metal atoms IR, laser, thermal energy and the magnetic field so as to excite, create, catalyze and stabilize electronic spin transitions and high electronic spin states of the excited carbon and metal atoms (for the production of high spin triplett, quartet and pentet carbon atoms) under chemical vapor deposition conditions, leading to the activated and more efficient rehybridization of these high spin carbon atoms for the massive chemical condensation of diamonds and / or CNTs. The specific photons of the laser may stimulate the nucleation of specific helical and diametric CNTs. An even greater massive chemical condensation is driven by selective, periodic and rapidly heating the metal catalyst via the IR-heating source for more efficient localization of energy for electronic, chemical and transport dynamics of high spin carbon atoms through the catalyst for lower ambient temperature selective condensation of CNT. The external magnetic field also provides conditions for creating, stabilizing, reacting and confining these high spin carbon and metal atoms. The continual supply, rehybridization and population inversion of carbon atoms overtime provides conditions conducive the massive and selective diamond and / or CNT productions. By operating the device to physically catalyze and stabilize electronic fixation of high spin states of carbon atoms by intense static arid / or dynamic magnetic fields, the chemical contamination is eliminated or may be modulated for controlled doping during the formation of diamonds and / or CNT, respectively. By operating the device to electronically fix carbon using the catalyst and magnetic fields, the electronic rehybridization rate is enhanced over the rates of currently used older arts of chemical catalytic fixation due to the reinforcing external magnetic field under CVD conditions relative to the intrinsic field of the catalyst and spin interactions with carbon atoms in the absence of the external magnetic field. The external field stabilizes high spin states of carbon and metal atoms, and enhances the intrinsic spin effects of the transition metal for chemical catalytic fixation. Moreover, an intense static external magnetic field stabilizes high spin carbon intermediates leading to stimulated diamond formation. On the other hand an intense dynamic external magnetic field intensified intrinsic spin density waves of the catalyst for enhanced CNT formation. This monumental discovery of magnetically activated rehybridization and stabilization of excited carbon contributes a watershed in the industrial massive production of diamonds and CNT when this magnetic discovery is coupled to new heating methods using IR photons. Furthermore, the stronger magnetic stabilization in this art relative to the weaker inherent fields in the catalyst of the older chemical catalytic art allow lower temperature generation of diamond and CNT. This new art provides diamond-CNT composite materials for novel diamond-CNT interfaces, new doping during the synthesis of diamond. Also in this new art, the magnetic densification of high spin carbon atoms allows more low pressure synthesis of diamond relative to older art. By switching the magnetic field on and off, this new art allows the selection of diamond or carbon nanotube growth.

A maser assembly includes a pump light source; a maser material including molecules that are excited through the absorption of light (1) from the pump light source, and which subsequently transfer via intersystem crossing (9) into the sublevels of their triplet ground states, so causing a population inversion between two sublevels (16,18); an electromagnetic structure in which the masing material is disposed, and which supports a microwave mode that is both resonant in frequency with and magnetically coupled to the transition between these two sublevels; and where energy is supplied to the microwave mode through stimulated emission (25) across the transition at such a rate as to exceed the mode's electromagnetic losses, the microwave mode being a maser mode. The assembly includes provisions for effecting substantially continuous maser activity during operation of the assembly. The laser crystal may be a (perdeuterated) pentacene in p-terphenyl which is held at room temperature without an additional magnetic field and the dye molecules in the single crystal may be pumped by blue LED with a frequency conversion to the yellow and green with the help of a Ce:YAG fluorescent pump light concentrator.

The invention discloses a seed light injecting master-slave matching method comprising the following steps of: generating seed light the wavelength of which is continuously scanned; injecting the seed light the wavelength of which is continuously scanned into a controlled laser oscillator; continuously scanning the wavelength of the injected seed light, wherein the scanning range covers longitudinal dies of one or more controlled laser oscillators; establishing population inversion by the controlled laser oscillator under the action of a pumping source and generating a stimulated radiation source; and outputting laser with the wavelength being equal or close to that of the injected seed light, wherein the mode matched with the wavelength of the injected seed light in the stimulated radiation gets the upper hand. According to the invention, the injection signal the wavelength of which is continuously scanned is generated by the seed light source, the length of the light cavity of the controlled laser oscillator can freely fluctuate without being controlled and the master-slave matching can be realized dynamically, so that the invention has the advantages of simple structure and low cost and is easy for operation.

The invention discloses a heterojunction semiconductor laser and a manufacturing method thereof. Two layers of Adelta-stacked phosphorene and three layers of Adeltadelta-stacked phosphorene are used to form an I-type semiconductor heterojunction through horizontal connection, and thus, population inversion in a laser diode can be realized and the working current can be effectively reduced. The semiconductor laser diode comprises a lower electrode (1), a substrate (2), a lower coating layer (3), an active layer (4), an upper coating layer (5) and an upper electrode (6) sequentially from bottom to top. The heterojunction of the same material is selected, crystal lattice matching is more easily achieved, the manufacturing process is simpler, the two layers of Adelta-stacked phosphorene and the three layers of Adeltadelta-stacked phosphorene can form the heterojunction through horizontal connection simply by a van der waals force. Through a mechanical stripping method, small-layer phosphorene with different stacked structures can be obtained.

The invention discloses a self Raman yellow light laser of a composite cavity structure. A laser diode pumping source emits pump light in an absorption belt of a gain medium, the pump light is focused inside the gain medium through a transmitting energy fiber and a coupling lens set, the gain medium absorbs the pump light to form population inversion, and base frequency laser generation is formed under the feedback action of a laser resonant cavity composed of a resonant cavity shared reflector and a laser total reflector; when base frequency laser passes through the gain medium, Raman gains are generated, and after the Raman gains are greater than the cavity loss of a Raman resonant cavity composed of the resonant cavity shared reflector, a beam splitter and a yellow light output mirror, stable Stokes light generation is formed in the Raman resonant cavity; the frequency of Stokes light is doubled in a frequency doubling crystal, and the generated yellow light secondary harmonic wave is output by the yellow light output mirror. The composite cavity structure is adopted, the length of a base frequency laser resonant cavity is largely decreased, and therefore the stable area of the resonant cavity is effectively enlarged, and the effect of improving the output power of the self Raman yellow light laser is achieved by applying higher pumping power.

The invention discloses a large power fiber laser with inner cavity frequency doubling, comprising a fiber laser resonant cavity and an inner cavity double-frequency system, wherein the fiber laser resonant cavity comprises at least one pair of cavity mirrors to form the resonant cavity; the resonant cavity is provided with at least one group of high power pump light sources, at least one fiber combiner which couples the pump light into active fiber to form population inversion, at least one signal wavelength selector, and at least one section of large mode field double-cladding polarization-maintaining rare earth doped fiber; the inner cavity double-frequency system comprises at least one frequency doubling crystal, at least one reflector, and at least one dichroic mirror, wherein a laser beam passes through the frequency doubling crystal and is output by the dichroic mirror. According to the inner cavity frequency doubling large power fiber laser, double-cladding large mode field fiber is adopted to increase the output power of near infrared fiber laser; by means of inner cavity frequency doubling, the conversion efficiency of double-frequency is substantially increased; by means of the polarization maintaining fiber, the fiber near infrared laser output polarization direction is made to be consistent with that of the frequency doubling crystal and stable double-frequency output is obtained.

The present invention discloses a laser amplifier with high gain and low thermally induced optical aberrations on the amplified laser beam. The amplifier designs allow simple multipass configurations to optimally extract the gain and reduce thermally induced index of refraction aberrations, making it possible to obtain an amplified laser beam of high quality combined with very high overall gains comparable to those achievable with expensive regenerative amplifiers. The amplifier includes a thin active laser solid to create the population inversion and associated heat generation within the thin laser active solid possible for the desired gain value. The system includes a cooling device in thermal contact with the thin active laser solid to provide good heat transport and high reflectivity coatings at the wavelengths of the pump and laser wavelengths. The pump light sources are laser diodes tuned to the maximum absorption of the laser active material. The amplifier also includes an optical system to transport the pump light to the laser active solid in such a way as to further confine the absorption of light along the two orthogonal directions in the plane of the laser active solid in order to get high population inversion and consequently high gains possible.