Abstract: Two solid state laser structures are provided which are optimized for multimode operation. The first laser structure has a plurality of normal incidence optically transmissive surfaces in the laser cavity. The most reflective one of those normal incidence surfaces is disposed at the optical center of the laser cavity. The gain medium is centered in the subcavity defined by a cavity mirror and the optical center. In the second laser structure, there are no normal incidence surface in the laser cavity, and the gain medium is disposed at the optical center of the laser cavity. The laser structures are employed to construct erbium glass lasers which are not only optimized for multimode operation but also have effective cooling of the gain medium and minimized thermal lensing effect.

Abstract: A folded Q-switched laser cavity uses total internal reflections of prisms to fold the intracavity beam. The index of refraction and the orientation of the prisms are selected to induce a predetermined phase delay between the two orthogonal polarization components of the linearly polarized intracavity beam. The predetermined phase delay rotates the intracavity beam polarization to an orthogonal direction such that an intracavity polarizer rejects the beam and the laser is held off from lasing. An electro-optic Q-switch cell is intermittently turned "on" whereby a second predetermined phase delay is induced onto the intracavity beam. The combination of the two predetermined phase delays results in a beam polarization orientation that is not rejected by the polarizer and the laser is not held off from lasing.

Abstract: A waveguide laser comprises a laser-active medium, a pump source for the laser-active medium and a resonator with a waveguide extending in an axial direction and formed from a cylindrical, outer optical waveguide surface and a cylindrical, inner optical waveguide surface. A resonator radiation field extends substantially parallel to the axial direction between the outer and inner optical waveguide surfaces. The waveguide laser further comprises two cavity mirrors between which the resonator radiation field extends and of which at least a first mirror comprises successive maximum and minimum reflectivity values in a direction azimuthal to the axial direction. The maximum and minimum reflectivity values of the first cavity mirror, viewed in the azimuthal direction, are arranged at the location of maximum and minimum intensities of a selected azimuthally closed mode of the resonator, which mode is enclosed by the resonator radiation field.

Abstract: A single-frequency semiconductor laser diode structure and a method for its fabrication. The structure includes a built-in etalon, which limits the frequency of operation of the device to a very narrow frequency band. For an edge-emitting diode, the etalon is formed over a cleaved end face of the semiconductor diode structure, and light is emitted from an opposed cleaved end face. For a surface emitting diode, the etalon is formed as an additional plurality of layers between a plurality of semiconductor layers forming the diode and a substrate on which the structure is formed. Transverse channels formed in the structure have side surfaces that act as mirrors, at least one of which is angularly inclined to the plane of the active region, to reflect light through the etalon layers and out through a parallel exterior surface of the structure. Multiple surface emitting lasers may be arrayed in closely spaced relation to each other, to form a powerful light emitting array.

Abstract: An amplitude-stable intracavity doubled laser comprises a pair of end mirrors defining a laser cavity having a length L. A laser medium having a gain region substantially smaller than the length L of the laser cavity is positioned within the laser cavity. A doubling crystal having a nonlinear conversion region substantially smaller than, the length L of the laser cavity is positioned within the laser cavity. A pump source is oriented to supply excitation energy to the laser medium. The laser medium and the doubling crystal located at positions within the laser cavity so as to cause the laser to lase in fewer than ten longitudinal modes and to output visible light with an amplitude noise of less than about 3% RMS on visible output from the laser.

Abstract: An apparatus and method for energy conversion of laser light with optical paramedic oscillation with reduced threshold and improved efficiency. A laser and an optical parametric oscillator are combined so that they share the same optical cavity. The laser field in the cavity is used as the seeding wave for the optical nonlinear material in converting the input pump wave into signal and idler waves, the idler wave having a frequency substantially identical to the laser frequency.

Abstract: A semiconductor laser emits semiconductor laser light with TM-mode oscillation. The emitted semiconductor laser light is collimated by a first collimating lens, passes through a Brewster plate that is arranged so that the direction of Brewster plane's p-polarized light is in alignment with the direction of polarization of the emitted semiconductor laser light, and is coupled to an incident portion of a wavelength-conversion waveguide by means of a focusing lens. While being guided through the waveguide, the emitted semiconductor laser light is converted into second-harmonic light by means of a polarization inversion region. Semiconductor laser light emanating from an emitting portion of the waveguide reflects from an output mirror towards a diffraction grating, for modulation in wavelength. Second-harmonic light emanating from the emitting portion of the waveguide is outputted from the output mirror.

Abstract: A semiconductor light emitting device includes a semiconductor light amplifier, a mirror which reflects light emanating from the rear end face of the semiconductor light amplifier to return the light to the rear end face of the semiconductor light amplifier, and a band pass filter which is inserted into the optical path of the light emanating from the rear end face of the semiconductor light amplifier and has a narrow transmission wavelength band.

Abstract: A position detecting apparatus comprises a light emitter which activates a laser source to emit a light beam so that mode hopping occurs, an interference optical system which directs the light beam from the laser source to a measuring light path on which an object to be measured is located and a reference light path on which a reflection mirror is placed and merges the reflected light beams coming back on the light paths so that the reflected light beams interfere with each other, a light sensor which receives the interference light beam provided by the interference optical system, and a position detector which determines the position of the object of measurement based on the interference signals produced by the light sensor before and after mode hopping caused by the light emitter.

Abstract: A passively controlled multiple output fiber laser system in which the frequency relationships between all of the optical outputs remain constant over time includes a plurality of fiber lasers for generating respective output beams. The lasers are positioned in close proximity to each other so that they experience the same environmental conditions. Each laser includes at least one Bragg reflection grating that controls the frequency and bandwidth of the laser's output beam. The Bragg gratings are formed so that they respond equally to environmental changes. In a preferred embodiment, the fiber lasers are made from a plurality of substantially identical photosensitive fibers, and Bragg gratings are exposed simultaneously under identical exposure conditions in each of the fibers. A multiple output fiber laser system suitable for heterodyne LADAR systems is also provided.

Abstract: A dual wavelength pumped low noise fiber laser includes a fiber laser 10 comprising a pair of Bragg gratings 14,16 at opposite ends of a fiber laser cavity 18 which is co-doped with two rare-earth dopants, Er.sup.+3 Yb.sup.+3, so as to allow lasing to occur at a lasing wavelength .lambda..sub.L. A first pump signal 20 efficiently pumps the Yb to the excited state and the Yb energy is transitioned to the Er atoms which ultimately lase at the desire lasing frequency. Because Yb is pumped so efficiently, high pump absorption is achieved, thereby providing high laser output power and, consequently, reduced RIN. Simultaneously, a second pump signal 52 directly pumps the Er at a different wavelength .lambda..sub.P2 which populates the lasing transition more quickly, thereby allowing sufficient bandwidth of a closed loop control on the second pump signal 52 to control low frequency RIN spiking due to relaxation oscillations in the laser.

Abstract: A gas laser consisting of a single elongated piece of dielectric material (1), with two hermetically sealed parallel elongated chambers (2) and (3), and an opening (4) connecting the two chambers. One of the elongated chambers (2) is of a cross section suitable for confining a laser gas discharge. The other elongated chamber (3) is a reservoir for laser gas, which also functions to dampen the unwanted acoustic waves generated by the laser gas discharge and as a means of extending the operating lifetime of the laser gas. The opening connecting the two elongated chambers serves to dampen the acoustic waves generated by the laser gas discharge traveling the length of the elongated laser chamber and to stop unwanted low angle wall reflections of laser light energy traveling at a slight angle to the length of the laser chamber.

Abstract: The design and application of an uncoated sapphire crystal as a beamsplitter and output coupler of a laser resonator includes placing the crystal sufficiently close to the Brewster angle to intercept a beam from a lasing medium in a free electron laser to provide a Fox-Smith type resonator or a Michelson type resonator depending on the optical path through the crystal to enable use of high power lasers in interferometric and optical coupling measurements.

Abstract: A light-emitting apparatus capable of selecting polarization direction of a light outputted therefrom includes a semiconductor laser and an optical amplifying device. The semiconductor laser is capable of selectively changing a direction of polarization plane of the output light to one of two orthogonal directions by controlling an excited state. The optical amplifying device amplifies the output light from the semiconductor laser. The optical amplifying device has amplification factors with respect to polarized light components in two orthogonal directions.

Abstract: The present invention relates to a tuneable ring laser with an output having a fixed, stable linear state of polarization with a fixed and known azimuth. The state of polarization at the output is fixed by compensating for component birefringence of the various ring elements that alter the polarization state and azimuth.

Abstract: A laser system wherein, in order that a high-output and high-quality single mode of a cross sectional area larger than the beam diameter determined by the construction of a resonator can be obtained stably, although this has heretofore been impossible, there is used a coupling mirror provided with a partial reflection film and an antireflecting film, a laser beam mode is selected using the partial reflection film, a phase difference between laser beam portions caused by a difference in construction between the partial reflection film and the antireflecting film is compensated using a phase difference compensating means, and there is formed an aperture whose diameter is set to a value of not larger than four times the diameter of the partial reflection film.

Abstract: A distributed feedback semiconductor laser selectively performs one of two oscillations in different polarization modes having different polarization planes. The laser includes a substrate, a light waveguide formed on the substrate, which at least partially includes an active layer, a diffraction grating formed around the waveguide, and an injecting unit for injecting a modulation current into a portion of the waveguide. The waveguide and the grating are constructed such that oscillation wavelengths of the polarization modes are different from each other and minimum values of threshold gain in the polarization modes near the Bragg wavelength are approximately equal to each other. The semiconductor laser can be driven by a minute modulation current and prevents degradation of response characteristics due to dynamic wavelength fluctuation in a high-frequency range when used in optical communication systems in which the switching of polarization mode is performed.

Abstract: A laser processing apparatus which makes it possible to select a laser beam mode always optimally suited to processing of a workpiece on the basis of a change in the focusing characteristic of each mode and the amount of movement of the beam's focal point with respect to a change in a laser output value. The laser processing apparatus includes a laser oscillator capable of changing the beam mode of its laser beam, and a processing table, all controlled by a controller which operates to change the beam mode of the oscillator in correspondence with a laser output during processing.

Abstract: The ellipticity of a thermal lens is controlled in a diode-pumped anisotropic crystal, such as Nd:YVO4. The crystal has two opposing optical end faces through which a pump beam and an output beam pass. The crystal also has opposing "c" axis crystal faces normal to a "c" axis of the crystal, and opposing "a" axis crystal faces that are normal to an "a" axis of the crystal. A mount supports the crystal and serves as a heat sink. A path is created to conduct heat from the crystal through the "c" faces, while the "a" faces are thermally isolated from heat conduction. The thermal lens ellipticity is controlled in order to produce a round, diffraction limited gaussian beam suitable for applications that require a high power, good quality beam from a simple, reliable laser source.

Abstract: The optical design of a laser resonator smooths out the intensity beam profile of the generated laser beam and prevents the formation of "hot-spots." The active laser resonator containing the active laser medium is optically coupled to a free space passive optical resonator to provide mixing and filtering of the spatial modes.

Abstract: A process for a simultaneous optical modulation transposition on several wavelengths. Use is made of a semiconductor laser able to freely oscillate on several longitudinal modes, the semiconductor laser being able to lock on a wavelength of an incident optical beam. The modulation is transposed on the modes which are not at the wavelength of the incident optical beam. Such a process may find particular application in optical telecommunication systems.

Abstract: A semiconductor laser oscillator structure and method is described having a tapered gain region in one-half of a laser cavity and a confocal oscillator region in another half of the cavity. An aperture is formed between two pairs of cavity spoilers located between the two cavity halves. One pair of spoilers is provided for receiving light which is reflected off of an output facet back into the semiconductor and removing it from the gain region. The other pair of spoilers removes light reflected from a curved mirror surface formed at the end of the other laser cavity half.

Abstract: A laser resonant cavity defined by a set of reflective end elements positioned to together form a closed optical path, again medium positioned along the closed optical path, means for exciting the gain medium to produce a laser beam within the cavity, at least one focusing element positioned within the cavity in optical alignment with the gain medium, and a prism positioned as one of the end elements of the cavity and providing angular dispersion of the laser beam. The prism, end elements, gain medium, and focusing elements are positioned with respect to each other such that the resonant cavity supports a coexistence of several monochromatic laser modes, each mode having a distinct propagation axis. Propagation axes of modes having relatively longer wavelengths traverse more of the prism than propagation axes of modes having relatively shorter wavelengths, resulting in the addition of a negative component to the group velocity dispersion of the laser cavity.

Abstract: Apparatus for mode discrimination in laser applications. A laser operating at a wavelength .lambda.c may have an undesired mode operating at .lambda.e. Mirrors are constructed such that the loss induced in the undesired mode by the wavelength centering of at least one of the mirrors exceeds the available gain of the laser.

Abstract: A single mode laser with a laser cavity consisting of an active medium and a first and second reflectors with an antiguide region or layer having a high refractive index positioned adjacent to the laser cavity to bleed off higher order lasing modes and preventing them from attaining the lasing condition. Specifically, light belonging to higher order modes leaks or bleeds into the antiguide region from the laser medium and from the first and second reflectors. When spacers for selecting the desired wavelength of laser light are provided, the light travelling through them leaks into the antiguide layer as well.Optimization of the bleeding of higher order modes into the passive antiguide region can be achieved by adjusting a taper angle of the laser cavity. Furthermore, by adjusting the ratio of the equivalent refractive index of the laser cavity and the passive antiguide region single mode operation at high current levels can be realized for apertures as large as 30 .mu.m.

Abstract: A semiconductor laser has been developed which is capable of efficiently transmitting a predetermined number of modes to an external fiber or waveguide. The laser includes an active gain region disposed in a laser cavity that is formed in a semiconductor material. A lens and a waveguide are also located in the laser cavity. The lens receives optical energy generated by the active gain region and directs this energy into one end of the waveguide. The waveguide transmits the optical energy from the laser to an external fiber or waveguide. The waveguide may be either a single mode waveguide or a multimode waveguide that selects a predetermined number of modes from among all the modes generated by the active region. If a single mode waveguide is employed, the output energy is composed of the fundamental frequency generated by the active region. If a multimode waveguide is employed, the output energy is composed of the predetermined modes selected by the waveguide.

Abstract: A laser cavity configuration employs a mode reshaping structure in a solid state waveguide. The mode reshaping may be by means of an adiabatic taper. Polarization switching may be employed in connection with the mode reshaping to obtain a high output power in a single transverse spatial mode from an integrated external cavity multiple-mode diode laser device. The structure provides stabilization and rapid tuning of the frequency of the diode laser, as well as use substantially all of the available power of the diode laser operating multimode. Various configurations and combinations are described. An advantage is that an integrated structure can provide output of the laser in a waveguide with single mode for subsequent applications. The external cavity diode laser according to the invention is consistent with a planar manufacturing process such that high volume, low cost products can be achieved.

Abstract: In order to improve a semiconductor laser system with a plurality of semiconductor laser units, from which laser radiation exits, a light-conducting fiber associated with each semiconductor laser unit, a coupling element for coupling the laser radiation exiting from the respective semiconductor laser unit into the respective light-conducting fiber, and a fiber bundle comprising the fibers as light conductor system, a total laser radiation formed by the sum of the laser radiations generated by the respective semiconductor laser units exiting from one end of this fiber bundle, the total laser radiation illuminating a target surface on an object to be irradiated during laser activity of all the semiconductor laser units, such that complex irradiation tasks can be performed it is suggested that the semiconductor laser units be designed such that they operate relative to one another in a phase-defined and frequency-defined mode operation, that the laser radiation of each semiconductor laser unit be coupled into th

Abstract: A semiconductor laser (10) having an external cavity used for coherent frequency and time domain reflectometry is provided. The laser (10) provides a very stable single longitudinal mode characteristic, a very narrow lasing linewidth, and a very low noise optical output. The laser (10) includes a semiconductor optical amplifier (14) emitting a coherent light beam from one facet, a phase modulator (22) receiving the coherent light beam and linearly varying an optical frequency of the laser, and an etalon (32) selecting and stabilizing one longitudinal mode of the laser cavity for lasing, narrowing the linewidth and reducing the noise. A computer-controlled and piezoelectric actuated wavelength-selective grating (58) varies the length of the laser cavity and thereby tuning the optical frequency of the selected longitudinal mode to track the transmission frequency of the etalon by maintaining maximum power intensity thereby stabilizing the selected mode.

Abstract: A laser system wherein, in order that a high-output and high-quality single mode of a cross sectional area larger than the beam diameter determined by the construction of a resonator can be obtained stably, although this has heretofore been impossible, there is used a coupling mirror provided with a partial reflection film and an antireflecting film, a laser beam mode is selected using the partial reflection film, a phase difference between laser beam portions caused by a difference in construction between the partial reflection film and the antireflecting film is compensated using a phase difference compensating apparatus, and there is formed an aperture whose diameter is set to a value of not larger than four times the diameter of the partial reflection film.

Abstract: A single-longitudinal-mode laser comprises a laser medium, an etalon, and a resonator. The etalon is located in the resonator in a state such that two light passage end faces of the etalon, which are parallel to each other, may make a predetermined angle with respect to a resonator axis. The longitudinal mode of the etalon coincides with a gain peak wavelength of the laser medium. The single-longitudinal-mode laser is free from the problems in that the threshold value of the pumping power for the oscillation of the laser becomes large, in that the output power of the laser becomes low, in that the profile of the radiated beam becomes distorted, and in that the single longitudinal mode characteristics become bad.

Abstract: Method and device for generating optical pulses.According to the invention, in order to generate an optical signal in the form of optical pulses, a semiconductor laser (2) is made to function as gain commutation, and a portion of the light produced by this laser is reinjected into the laser. The light to be reinjected is previously filtered by an optical filter (12) which is tuned to one of the modes of the laser. Another portion of the light produced by the laser is used as an optical signal after having been filtered this portion by the optical filter.

Abstract: A doubler for a pulsed multimode laser diode. A controllable feedback loop controls the laser output such that one of the output wavelengths, or the average of two of them, fall within the acceptance bandwidth of a non-linear optical medium. Alternatively, radiation emitted from the pulsed laser is reflected over a path length such that reflected energy reenters the laser during the build-up of a following pulse.

Abstract: A magnetic device attached to a ring laser gyro is used to prevent undesirable operating conditions in a ring laser gyro. Undesirable operating conditions occur when the ring laser gyro operates at specific wavelengths. The magnetic device used with the ring laser gyro creates a magnetic field that suppresses the operation at those specific wavelengths so that the undesirable operating conditions are removed.

Abstract: The subject invention relates to a new regime of lasing--superbroadband or pre-assigned spectral composition lasing. A new cavity construction and application of room temperature operable LiF color center crystals provide generation with a spectral width in one pulse practically coinciding with the luminescence spectrum of the active medium.

Abstract: We have discovered that at least some optical waveguide lasers such as Er-doped fiber lasers are subject to excessive output amplitude fluctuations, including severe fluctuations when the laser is subjected to mechanical shock. We have determined that these highly undesirable fluctuations are due to a resonance phenomenon, and that the fluctuations can be at least substantially reduced by means of a feedback loop that makes the amplitude of the output of the pump laser responsive to the amplitude of the output of the waveguide laser. We have also discovered that the operation of a pump laser/waveguide laser combination is frequently improved if an appropriate non-reciprocal element (e.g., an isolator or a tilted wavelength filter) is placed between the two lasers. An exemplary embodiment of the invention comprises the feedback loop as well as the non-reciprocal element.

Abstract: A single wavelength semiconductor laser comprises a laser cavity portion and a mode selector portion. The laser cavity portion includes a waveguide and perturbation means for imparting a periodical perturbation to the waveguide. The laser cavity portion functions as a mode selecting reflective mirror for coupling two modes, which have different absolute values of propagation constants, to each other, accompanied with a mode conversion. The two coupled modes respectively travel forward and rearward along the waveguide to constitute two degenerate laser resonance modes. The mode selector portion selectively outputs a predetermined laser resonance mode out of the two degenerate laser resonance modes, and the mode selector portion is structured so that light returning to the semiconductor laser from outside can be coupled only to the other of the two degenerate laser resonance modes.

Abstract: A solid-state laser for generating harmonic laser light substantially at a desired wavelength has a pump diode body made of a first material, which is preferably aluminum, having a first coefficient of expansion and a laser diode mounted in the pump diode body for generating pump energy. A laser body assembly, which is positioned on the pump diode body, is made of a second material, which is preferably steel, having a second coefficient of expansion. The first and second coefficients of expansion of the respective pump diode body and the laser body assembly have a known relationship such that the laser cavity expands and contracts at a particular rate as the temperature of the laser increases and decreases to provide a substantially constant generation of the harmonic laser light. A laser gain chip mounted on an entrance mirror, which forms the back end of a laser cavity, generates fundamental laser light in response to pump energy from the laser diode.

Abstract: A method for synchronizing an etalon to a preselected set of optical frequencies includes the step of generating a transmission spectrum for an etalon having a characteristic free spectral range that is a function of its effective length. The optical frequencies for the transmission spectrum are provided by two optical reference frequencies such as produced by a first and second frequency locked laser. The effective length of the etalon is set in relation to the optical reference frequencies.

Abstract: A new injection-controlled laser resonator incorporates self-filtering and self-imaging characteristics with an efficient injection scheme. A low-divergence laser signal is injected into the resonator, which enables the injection signal to be converted to the desired resonator modes before the main laser pulse starts. This injection technique and resonator design enable the laser cavity to improve the quality of the injection signal through self-filtering before the main laser pulse starts. The self-imaging property of the present resonator reduces the cavity induced diffraction effects and, in turn, improves the laser beam quality.

Abstract: A solid state laser apparatus is capable of suppressing a mode hopping phenomena by restricting longitudinal modes except a fundamental mode, thereby providing a very stable output. The solid state laser apparatus includes such components as a semiconductor laser emitting a pumping radiation for exciting a lasant material, a lens systems for focusing the pumping radiation and an optical resonator including a concave mirror. The lasant material may be formed of Nd:YVO.sub.4 doped with approximately 1 at % of Nd and a non-linear optical element may be formed of KTiOPO.sub.4 with an inclined c-axis.

Abstract: The use of feedback circuit in a laser device with a frequency selective element such as an etalon allows for the production of a substantially single longitudinal mode output indefinitely. The feedback circuitry is adapted to adjust the length of the laser cavity so that a longitudinal mode of the laser device is near transmission peak of the frequency selective element.

Abstract: An improved slab-waveguide CO.sub.2 laser which includes two parallel, rectangular, flat, spaced-apart, slab electrodes whose surfaces excite a laser gas and guide laser light in a plane perpendicular to the surfaces of the slab electrodes. The component of the light propagating parallel to the electrode surfaces is not guided and is acted on only by resonator mirrors which form an unstable resonator. The improved slab-waveguide CO.sub.2 laser operates on a single vibrational transition of the CO.sub.2 molecule by employing wavelength selective optics.

Abstract: A high power, highly efficient laser that produces a polarized, round diffraction limited gaussian beam is disclosed. A strong thermal lens laser crystal with controlled ellipticity, is mounted in a laserhead and pumped by a fiber-bundle-coupled diode source. The pump beam diameter in the crystal is greater than the crystal's TEMOO mode diameter. The laser operates well over a large range of pump powers. Its slope efficiency in the TEMOO mode is greater than 40%, with an overall efficiency greater than 25%. One of the lasing crystals used is Nd:YVO4. This material exhibits high gain and a short upper state lifetime. These properties make it attractive in designing a Q-switched laser, or one that is insensitive to optical feedback.

Abstract: The present invention is directed to providing compact systems and methods for producing and amplifying chirped pulses to provide high energy ultrashort pulses. Further, the present invention is directed to providing a compact system which is reliable and cost effective to fabricate. In accordance with exemplary embodiments, relatively compact tunable lasers can be used to directly generate long chirped optical pulses. For example, compact monolithic semiconductor lasers which have relatively small dimensions (e.g., dimensions smaller than large frame solid state lasers) and which permit their emission wavelength to be tuned (i.e., changed) relatively fast during the generation of an optical pulse can be used. These pulse sources eliminate any need for bulk components in the cavity of, for example, a mode-locked femtosecond laser. The relatively long chirped optical pulses can subsequently be amplified in plural amplification stages to increase their energy content.

Abstract: A semiconductor laser gain structure having a tapered gain region comprising cavity spoilers for receiving light which is reflected off of the output facet back into the semiconductor and removing it from the gain region so as to reduce or eliminate self-oscillation. The boundaries of the gain region are also designed to have a very low refractive index gradient so as to minimize reflection of light off of the boundaries back into the gain region. The gain structure may be embodied in a semiconductor laser oscillator or semiconductor laser amplifier depending on whether the input facet is or is not, respectively, anti-reflection coated. The output facet is anti-reflection coated in either embodiment.

Abstract: Controlled, high-power laser oscillator. A single laser gain medium is used to efficiently generate high-power, controlled laser light without exposing the control elements to high-power radiation. The control element or elements are separated from the oscillator gain volume by a separator optic which permits only a portion of the energy from the gain volume to enter the region of the control elements, laser light having the desired characteristics being returned to the gain volume through the separator optic. Energy not entering the control region exits the laser as oscillator output energy in order to obtain high efficiency.

Abstract: A diode-pumped solid state laser for single-mode operation contains a resonator with an input mirror and an output mirror between which an active laser medium, a polarizer and a birefringent crystal are disposed. The crystal is disposed with its optical axes in such a way that the latter form an angle of 45.degree. to the polarizing direction produced by the polarizer. The losses for the ordinary and extraordinary rays are adjusted to be substantially equal. A temperature control means is used to keep the temperature of the birefringent crystal at a constant value so that the refractive indices and the length of the crystal do not change.

Abstract: An apparatus for achieving in-phase mode operation of a diode laser. A photonic band gap mirror (photonic crystal) having a periodic lattice structure is placed in front of light emitted from one side of the laser diode array. Because of an incomplete photonic band gap in the photonic crystal, light normal to the crystal will be primarily reflected while light at an angle will be primarily transmitted through the mirror. Since in-phase emission is primarily normal and out-of-phase emission primarily off axis, the reflected light which is directed back into the laser cavity will be the predominant lasing mode. The out-of-phase mode primarily transmitted will have significantly larger losses. The resulting laser diode apparatus will therefore operate in-phase and produce a single lobe far-field distribution.

Abstract: A technique for generating a large number of stabilized optical frequencies suitable for use in a wide variety of applications, including a multi-channel optical communications system, optical processing, optical computing, and heterodyne generation of stabilized RF frequencies. The technique contemplates stabilizing the cavity of a master laser and using the cavity modes as the carrier frequencies. Preferably, the modes are coupled, as by mode-locking, in order to prevent the modes from competing with each other for the laser gain, which would cause large amplitude variations. Since the cavity is stabilized, all of the cavity modes are stabilized. In one set of embodiments, the master laser is used directly as the laser source, the components at the different mode frequencies are spatially separated (demultiplexed) so that the component at each mode frequency can be individually amplified and modulated (e.g., by electro-optic (EO) modulators).