Abstract: A semiconductor laser device with window regions according to the present invention is provided, in which a double hetero structure including cladding layers and an active layer sandwiched by the cladding layers is formed on a semiconductor substrate, the double hetero structure is buried in burying layers with a bandgap larger than that of the active layer, and the burying layers form window regions situated at both end facets of the double hetero structure, wherein the window regions have a waveguide structure including a plurality of semiconductor layers with different bandgaps.

Abstract: An improved broad area surface emitting distributed feedback semiconductor laser diode device (10) includes a P-side ohmic contact (28) and an N-side ohmic contact (36). A potential difference is applied across these contacts to create an electric field that induces a stimulated emission of coherent photon radiation. The coherent photon radiation produced by the stimulated emission process is incident upon a second order grating having a curved pattern incorporated therein (29). An output beam, directed normal to a chemically etched output window (38), is produced by a first order diffraction of photon radiation from the surface of the second order curved grating (29). The output beam has a more uniform lateral mode near-field output intensity profile and a more uniform lateral mode near-field phase. The output beam also has a desired single-lobed lateral mode far-field output intensity profile. Moreover, the device (10) concentrates approximately 1 Watt of power into this single lateral mode far-field lobe.

Abstract: Whenever any laser is interfaced with any type of optics there is always backscatter back into the laser. For diode lasers this backscatter makes it emit chaotic radiation where the frequency spectrum is broad and contains many different frequencies. This means that the laser has limited use as a source of information transfer in fibers. This weakness can be overcome, by driving the laser with an external cavity filled with a Kerr material. The addition of a Kerr material in the external cavity suppresses the chaos, or coherence collapse. Thus the new apparatus of laser plus external cavity filled with a Kerr material increases the stability of the diode laser.

Abstract: An optical mode coupling apparatus includes an Erbium-doped optical waveguide in which an optical signal at a signal wavelength propagates in a first spatial propagation mode and a second spatial propagation mode of the waveguide. The optical signal propagating in the waveguide has a beat length. The coupling apparatus includes a pump source of perturbational light signal at a perturbational wavelength that propagates in the waveguide in the first spatial propagation mode. The perturbational signal has a sufficient intensity distribution in the waveguide that it causes a perturbation of the effective refractive index of the first spatial propagation mode of the waveguide in accordance with the optical Kerr effect. The perturbation of the effective refractive index of the first spatial propagation mode of the optical waveguide causes a change in the differential phase delay in the optical signal propagating in the first and second spatial propagation modes.

Abstract: A laser light generating apparatus of the invention comprises an exciting light source (1) for generating a plurality of exciting laser beams, a laser medium (7) for generating at least two laser beams with radiation of the plurality of exciting laser beams at different positions thereof, reflecting means (8) for reflecting at least a part of the laser beams generated from the laser medium (7) and constructing a laser resonator (5) with thermal lenses (7a) through (7d) formed within the laser medium (7), and phase-compensating means (9) for compensating a phase of a laser beam from the laser resonator (5). Therefore, the laser generating apparatus becomes able to generate a laser beam whose energy is much concentrated within a small divergent angle. Furthermore, it becomes possible to control the laser beam in tracking by changing a phase-compensating amount of the phase-compensating means.

Abstract: A Coupled Multiple Output Resonator (CMOR) having two symmetric modules 10,20, is created by adding self-feedback (SFB) mirrors 104,106 aligned with apertures 100,102, in output scraper mirrors 14,24, respectively, to a conventional Multiple Output Resonator (MOR). The SFB mirrors re-inject a portion of the output beams 34,42 back into the resonator cavity as adjoint beams 108,110 which alter the modes of the system such that the CMOR only lases at desired modes where all the output beams 34,42 are in-phase. The CMOR provides substantially constant acceptable mode discrimination for more than 4 modules with only one SFB mirror per module and no additional external coupling paths between modules, thereby allowing the system to be scaled to any number of lasers without reduction of target intensity. Also, the SFB mirrors are small and are easily controlled to compensate for cavity mirror variations to maintain the desired mode discrimination.

Abstract: Efficient, low threshold laser emission from a laser crystal doped with chromium and neodymium ions is obtained when pumped by visible laser diodes in the range of 610 nm to 680 nm. A typical laser Cr,Nd:GSGG crystal having an extraordinarily broad absorption bandwidth allows high pump efficiencies when using visible laser diodes, particularly in comparison to the Nd:YAG laser. The broad absorption bandwidth tolerance of the Cr,Nd:GSGG crystal to the pumping wavelengths allows visible diode pumping of the neodymium transition without regard to the wavelength of the visible diodes. Longitudinal or end-pumping to take advantage of the emission properties of the visible laser diodes, a nearly hemispherical laser resonator configuration and other co-doped Cr,Nd laser host materials are disclosed. Consequently, costs are reduced for the semiconductor pump as well as producing a compact, efficient, lightweight and reliable laser previously unachievable with other types of laser or lamp pumping.

Abstract: Frequency modulated radar transmitters with a repetitive linear increase in frequency with time, referred to as "frequency chirps", are required for many radar applications. The present invention provides a simple way of obtaining such a chirped frequency modulation for a laser radar transmitter or the like. The principle is to translate an optical wedge in the direction of its wedge gradient at constant velocity across the optical path of a laser resonator. The resulting increase or decrease in the effective optical length of the resonator causes frequency chips. In a first embodiment of the present invention, a rotating phase plate on the face of a rotating wheel with the added phase varying linearly with angular position around the wheel is placed within a laser's resonator cavity to tune the optical pathlength of the cavity and thereby the longitudinal mode of the resonator to produce the chirp. This embodiment can be used in either a reflective or a transmissive mode.

Abstract: A solid-state laser having a laser resonator which includes an etalon to allow a single longitudinal mode of oscillation to occur in the width of the wavelength which permits the oscillation of the medium of the solid-state laser. The etalon is interposed in the resonator which is constituted of a surface of a resonant mirror and one end surface of a solid-state laser medium, and wherein the interval of the longitudinal modes of the etalon is set to be in the range from approximately one half to one width of the oscillation wavelength of the medium of a solid-state laser. At the same time, the ratio, with respect to the optical length, of the etalon to the resonator is selected to be about a half integer.

Abstract: A helium-cadmium laser having high reflector mirror and output coupler mirror properties which favor lasing at 353.6 nm while inhibiting lasing at 325.0 nm. The preferred characteristics of the high reflector and/or output coupler mirrors include transmission at 325.0 nm greater than 10% and transmission at 353.6 nm less than 5%.

Abstract: An internally folded scalable laser has a gain medium with an internal face nd an external face and at least one internal-fold face subtending an angle which may be about 90.degree.. An output coupler that is partially reflective of the resonator mode is oriented to receive and reflect resonator mode in a direction normal to the internal face to avoid resonator mode astigmatism and to define a folded hemispherically-shaped resonator cavity extending from the output coupler and through an active volume in the gain medium to the external face. A pumping mode source disposed adjacent to the external face is oriented to focus a first pumping mode in a direction normal to the external face in a boom waist at or inside the external face in the folded resonator cavity to define an active volume in the gain medium and to avoid pumping mode astigmatism.

Abstract: A high-power continuous-wave laser resonator (10) is provided, wherein first, second, third, fourth, fifth and sixth mirrors (11-16) form a double-Z optical cavity. A first Ti:Sapphire rod (17) is disposed between the second and third mirrors (12,13) and at the mid-point of the length of the optical cavity, and a second Ti:Sapphire rod (18) is disposed between the fourth and fifth mirrors (14,15) at a quarter-length point in the optical cavity. Each Ti:Sapphire rod (17,18) is pumped by two counter-propagating pump beams from a pair of argon-ion lasers (21-22, 23-24). For narrow band operation, a 3-plate birefringent filter (36) and an etalon (37) are disposed in the optical cavity so that the spectral output of the laser consists of 5 adjacent cavity modes. For increased power, seventy and eighth mirrors (101, 192) are disposed between the first and second mirrors (11, 12) to form a triple-Z optical cavity.

Abstract: In accordance with the present invention, an optical processing device and method are provided for processing with extremely low energy requirements. Spontaneous emissions from an excited optical gain medium generate a waveform that propagates within a cavity defined by the gain medium and a reflective device. A first spatial modulating element is disposed in the cavity in the path of the generated wavefront to impose a first spatial pattern thereon. A second spatial modulating element also is disposed in the cavity and imposes a second spatial pattern on the perturbed wavefront carrying the first pattern. When the first and second imposed spatial patterns have dual spatial pattterns, light is directed back along pathways through the cavity to induce stimulated emission and eventually resonance in the cavity.

Abstract: A laser is fabricated from an optical transmission medium having a laser cavity with an rare earth (e.g. Erbium) doped portion. At least one longitudinal mode is suppressed using a plurality of series coupled Fabry-Perot cavities, an optical grating, or a combination thereof. Ring lasers, Sagnac cavity lasers, Fox-Smith cavity lasers, and linear structures are disclosed.

Abstract: A laser that is capable of producing light from a chosen group of frequencies not adequate or available using a single gas laser is provided. The laser is capable of producing selected and well defined light wavelengths. The laser is also capable of eliminating unwanted frequencies in order to prevent such frequencies from competing with (robbing power from) the desired wavelengths. The laser constitutes a multiple gas laser. A combination of argon and krypton is used. Argon is known to produce a good blue laser beam in the area of 488 nm. Mixed with the argon is krypton. Krypton also produces a blue output at 482 nm and 476 nm. In addition, krypton produces strong outputs in red, yellow, and green wavelengths (647 nm, 568 nm, and 529 nm respectively). Accordingly, access to each of these colors is provided by the argon-krypton in the mixture. Certain light frequencies are unnecessary and undesirable. Elimination of undesirable wavelengths is accomplished primarily through the optics used.

Abstract: Non-linear effects in an optical fiber used for communicating AM signals at high power levels are reduced by increasing the linewidth of the pump laser output signal. The linewidth can be increased by optically broadening the laser output signal by driving an optical angle modulator with broadband electrical noise. The optical signal is then externally modulated with an AM information signal for transmission over an optical link fiber. The optical modulation can be provided using either an FM or PM optical modulator. A desired linewidth can be provided by controlling the optical modulation index during the optical modulation step and/or by controlling the bandwidth of the noise source. Other techniques for broadening a laser output signal, including modulating the signal by a periodic function such as a sine wave, or injecting spontaneous emissions into the laser cavity, are also disclosed.

Abstract: A narrow bandwidth incoherent optical source is provided. A superluminescent source includes a gain medium having an input end and an output end. The input end of the gain medium is optically coupled to a reflector to cause spontaneous emissions within a predetermined band exiting the input of the gain medium to be reflected back into the medium. Spontaneous emissions outside of the predetermined band are lost. The gain medium can comprise a doped fiber, such as an Erbium doped fiber. An optical isolator prevents the superluminescent source from lasing. By providing a plurality of reflectors operating in different bands, the superluminescent source can generate a plurality of optical carriers.

Abstract: A compact all-fiber, electrically tunable ring laser includes a diode-pumped erbium-doped fiber amplifier. The frequency of the laser is tuned by a fiber Fabry-Perot (FFP) etalon that is electrically tuned. An in-line optical isolator is used in conjunction with the FFP to eliminate undesired reflections. A second FPP with a narrow free spectral range (FSR) can be used in conjunction with a first FFP with a wide FSR.

Abstract: A modelocked laser with an unstable resonator configuration is described. The laser relies on adjoint mode feedback with a modulator in the low power feedback beam path which is not part of the main resonator. The optical cavity length and the path length of the feedback beam are adjusted to provide a pulsed, modelocked output beam.

Abstract: Accurate mode partition data from a laser are collected simply and rapidly in accordance with the principles of the invention wherein the laser output is directed to a filter which separates a central longitudinal mode from the side modes. The filter operates to present all side modes in a predetermined wavelength range simultaneously and continuously at the output of the filter. By subsequently comparing the intensity or power in the side modes delivered to the filter output with a predetermined threshold, it is possible to determine the frequency of occurrence and magnitude of mode partition events for side modes in the predetermined wavelength range.

Abstract: A system for controlling the polarization of lasers is described in which the polarization of laser radiation generated in a gain cavity is controlled by feedback of a controlled amount of polarized light from a polarizing cavity. The output mirror of the gain cavity forms an input mirror of the polarizing cavity.

Abstract: A dielectric interference film having a central region of one thickness and a peripheral region of a different thickness is superimposed on one of the mirrors of a ring laser gyroscope for the purpose of suppressing off-axis resonant modes that are characteristic of a resonant cavity. The central region is designed to intercept a large portion of the fundamental mode power and a lesser portion of the off-axis mode power. The difference in thickness between the central and peripheral regions causes the reflected light from the two regions to differ in phase by approximately one-half wavelength and destructively interfere. As a result of the imbalance of the fundamental and off-axis mode powers incident on the central region, the reflectivity losses of the off-axis modes are more pronounced than those of the fundamental mode with the result that the off-axis modes are completely suppressed.

Abstract: Multibeam coupling in a Kerr medium of nonlinear characteristics and finite response time is disclosed together with two different frequency spectrum examples of its use. In the first spectrum example, the modes are equally spaced and in the second spectrum the frequency separations are all unequal. In either case, as the beams propagate, both input spectra eventually reach a saturation characterized by a cascading of energy into the lowest frequency if the Kerr constant is positive. The direction of cascading of energy transfer is reversed to the highest frequency if the Kerr constant is negative. The examples disclosed include a typical Kerr medium and are representative of a multimode, equally spaced laser source and an unequally spaced source. For the equally spaced case, the optimum medium response time for conversion of Gaussian spectra is disclosed. If the frequencies are unequally spaced general conditions to be satisfied are disclosed, along with examples.

Abstract: A single mode pulsed dye laser oscillator is disclosed. The dye laser oscillator provides for improved power efficiency by reducing the physical dimensions of the overall laser cavity, which improves frequency selection capability.

Abstract: A stabilized local oscillator frequency for heterodyne laser sensors comped of an acousto-optic crystal which provides a constant frequency offset f.sub.1, to a portion of laser transmitter power at frequency f.sub.0, for injection locking a separate local oscillator connected to a detector which simultaneously mixes f.sub.1 with the return signal f.sub.0 from a target. The detector outputs the difference frequency between f.sub.0 -f.sub.1 which is processed for the desired information. Proper local oscillator tuning is maintained through the use of a piezo-electric translator regulating the axial length of the local oscillator.

Abstract: A laser is fabricated from an optical transmission medium having a laser cavity with an rare earth (e.g. Erbium) doped portion. At least one longitudinal mode is suppressed using a plurality of series coupled Fabry-Perot cavities an optical grating, or a combination thereof. Ring lasers and linear structures are disclosed.

Abstract: A method for controlling a narrow-band oscillation excimer laser which is suitable for control of an excimer laser used as a light source of a reduced projection exposer, and a system thereof. At least two wavelength selective element are disposed within a laser oscillator. There are provided a center wavelength control for causing an oscillation center wavelength determined by these wavelength selective elements to coincide with a desired value, an overlapping control for overlapping the transmission wavelengths of these wavelength selective elements, and a power control for controlling a voltage applied to electrodes located within a laser chamber to thereby control a laser output. Partial gas replacement is carried out when the application voltage to the electrodes within the laser chamber becomes high.

Abstract: A laser is fabricated from an optical transmission medium having a laser cavity with an rare earth (e.g. Erbium) doped portion. At least one longitudinal mode is suppressed using a plurality of series coupled Fabry-Perot cavities, an optical grating, or a combination thereof. Ring lasers and linear structures are disclosed.

Abstract: A laser amplifier package comprises two laser amplifiers coupled via two lenses and an optical isolator. The first and second laser amplifiers may both be run as amplifiers to give an overall improved gain and reduced residual facet reflectivity. The first amplifier may be run as a pulse source as part of an LEC or gain switched DFB laser assembly. Pulses generated to be, or compressed to, near transform limited enable the output from the package to be optical solitons. The second laser amplifier may be switched to provide modulation.

Abstract: The invention concerns a device for generating light, in particular light for use in length measurement using an interferometer. The frequency of the laser light emitted is controlled as a function of the wavelength in the surrounding gaseous medium (air) in such a way that the wavelength in the air remains constant. The light source in this device is a laser diode. Located external to the laser resonator is a device for feeding back to the resonator, at selected frequencies, light emitted by the laser diode.

Abstract: Improved side mode suppression with significantly reduced side mode suppression ratio fluctuation during laser tuning is realized in a distributed Bragg reflector laser structure by incorporating at least one reflector element which exhibits an asymmetric reflection characteristic versus wavelength over a band of wavelengths wide enough to include at least two longitudinal modes of the laser. That is, the asymmetric characteristic is wider than the mode separation for adjacent longitudinal modes of the laser. In one embodiment, a distributed Bragg reflector laser is shown wherein the Bragg reflector includes a corrugated waveguides with corrugations having a period which varies nonlinearly from .LAMBDA..sub.O at one end of the reflector to .LAMBDA.hd L at the opposite end of the reflector, where .LAMBDA..sub.O is greater than .LAMBDA..sub.L. Integrated and extended cavity or hybrid structures are described in both semiconductor and fiber laser structures.

Abstract: A monochromatic dye laser is constructed from a short cavity laser 61 with an external narrow bandwidth amplifier 62 designed to pass only a single mode. The frequency of the SCL is controlled by a servo fed from an interferometer which monitors the spacing of the laser mirrors, while the pass frequency of the NBA is controlled by a servo 68 fed by photodetectors 65,66 which monitor the amplitude of peripheral bands.

Abstract: Accurate mode partition data from a laser are collected simply and rapidly in accordance with the principles of the invention wherein the laser output is directed to a filter which separates a central longitudinal mode from the side modes. The filter operates to present all side modes in a predetermined wavelength range simultaneously and continuously at the output of the filter. By subsequently comparing the intensity or power in the side modes delivered to the filter output with a predetermined threshold, it is possible to determine the frequency of occurrence and magnitude of mode partition events for side modes in the predetermined wavelength range.

Abstract: A ring laser is provided with only two reflecting surfaces to define the cavity. A gain medium is located between the reflecting surfaces. At least one optical interface is located within the cavity and is oriented such that the beam will be deflected by refraction to create a ring path. The angle of incidence of the beam with the interface should be less than Brewster's angle and the surface should have an antireflective coating. The interface can be located on the lasant material, on a non-linear optical material or on a passive optical element. Preferably, the device is arranged to achieve unidirectional and single frequency operation. When the ring is used for intracavity second harmonic generation, the resultant output is amplitude stable because of the avoidance of mode beating. The second harmonic radiation is generated unidirectionally increasing useable output.

Abstract: An array of semiconductor laser diodes having parallel waveguide elements, of which each adjacent pair is coupled together by an X-shaped waveguide junction having a connecting waveguide in which lateral modes are formed as a result of merging of the pair of waveguide elements. The waveguide elements diverge again from the connecting waveguide at an angle great enough to ensure that there are high scattering and radiation losses near the point of divergence of the waveguide elements, for the fundamental mode in the connecting waveguide. If an adjacent pair of waveguide elements operate in phase, this excites the fundamental mode in the connecting waveguide, which is effectively suppressed by the losses that occur near the point of divergence from the connecting waveguide. The structure thereby discriminates against connecting waveguide in an in-phase mode, resulting in operation in the 180.degree.

Abstract: An actively stabilized laser is disclosed which includes a temperature tunable etalon in the laser cavity for single frequency operation. The operation of the laser is actively monitored to detect variations induced by changes in the length of the resonator. These changes tend to cause the frequency of the selected longitudinal mode to shift so that it is no longer aligned with the peak of the transmission curve of the etalon. When this misalignment occurs, operation deteriorates. By monitoring laser performance, the misalignment can be detected and the temperature of the etalon can be changed to realign its transmission peak to the selected mode. In the preferred embodiments, either the laser output power or the current supplied to the laser is monitored. This approach substantially reduces mode hopping.

Abstract: A laser having a phase conjugating reflector positioned with a resonant cavity of a laser configuration capable of multimode operation. The resonant cavity or other means associated with the laser configuration selects the preferred mode at threshold. The phase conjugating material builds up reflectivity as the light intensity is increased above threshold power levels to maintain the selected mode to high power levels. One embodiment has an external Talbot cavity with a first mirror in a Talbot plane of a multi-emitter laser array and with the phase conjugating material at a sub-Talbot plane. Another embodiment has an external GRIN lens cavity with a far field apertured stripe mirror for threshold mode selection. The phase conjugator is placed at a high light intensity position within the cavity such as adjacent to the stripe mirror or adjacent to the laser array. The laser source may be a linear laser diode array or a 2-D surface emitting laser array.

Abstract: An apparatus for coherent beam combining of lasers and for lateral mode control is disclosed, comprising a miniature Talbot cavity having at least a first and second surface. The first surface is to receive light from said lasers, and the second surface contains a reflecting mirror. In one embodiment, the mirror spaced apart from said first surface by a distance Z=nd.sup.2 /.lambda. where n is a nonnegative integer, .lambda. is the laser wavelength, and d is the laser aperture spacing. In this embodiment, the mirror is divided into reflecting and non-reflecting portions, the reflecting portions patterned to reflect only that portion of the light from said lasers having a half-period shift corresponding to a fundamental lateral mode. In another embodiment, the mirror is spaced apart from the first surface by a distance Z, such that nd.sup.2 /.lambda.<Z<(n+1)d.sup.2 /.lambda., where n is a nonnegative integer, .lambda. is the laser wavelength, and d is the laser aperture spacing.

Abstract: A laser adapted to operate at a constant, predetermined wavelength includes the following elements disposed in order within a laser cavity and aligned along the path of light flow therethrough: a highly reflective rear mirror, a halfwave plate, a Brewster window, an active laser medium, and an output coupler. The halfwave plate is designed to rotate incident light beams by 180.degree. at the predetermined wavelength and to rotate incident light beams by an amount other than 180.degree. at wavelengths other than the predetermined wavelength. In a preferred embodiment, the Brewster window is a thin film polarizer designed for the predetermined wavelength.

Abstract: A room temperature solid state laser for producing a laser emission at a wavelength of substantially 1.96 microns is disclosed. In a preferred embodiment, the laser includes: a laser cavity defined by a plurality of coated reflective elements to form a reflective path thereamong; a laser crystal disposed in the laser cavity and capable of lasing at substantially 1.96 mircons and 2.01 microns when excited; and means for exciting the laser crystal to lase at substantially 1.96 microns and at substantially 2.01 microns. The laser crystal is comprised of a host crystal material capable of accepting Cr.sup.3+ and Tm.sup.3+ ions. Through their respective reflectivities at each of the wavelengths at substantially 1.96 microns and 2.01 microns, the coated reflective elements collectively operate to produce substantial loss in radiation at the wavelength of substantially 2.

Abstract: A laser device according to the present invention having a semiconductor laser which has at least two longitudinal modes .lambda..sub.0 and .lambda..sub.1 both of which are able to oscillate, and oscillating at the single longitudinal mode .lambda..sub.0. The device further comprises input means which inputs a wave nearly coincident with .lambda..sub.1 to the semiconductor laser to switch the oscillating wavelength from .lambda..sub.0 to .lambda..sub.1. The semiconductor laser maintains its oscillating wavelength .lambda..sub.1 even if the intensity of said wave input from said input means reduces.

Abstract: In a laser in which two longitudinal modes of a laser emission are excited, high frequency stability and intensity stability of the laser emission are achieved in that the dimensioning of the laser is used to produce a coupling of the intensities of the two modes and thus at least one minimum of the gain curve over frequency appears. This curve is swept by modifying the optical length of the resonator and an extreme value of the curve is thereby stored. Proceeding from this extreme value, an intensity value is identified which deviates from the extreme value by a prescribed amount and this intensity value is kept within prescribed limits by adjusting the optical resonator length. This invention is particularly suitable for gas lasers and in particular helium neon-lasers.

Abstract: Disclosed herein in a side mounted aperture and a Faraday rotator assembly useful in conjunction with an out-of-plane multi-oscillator ring laser gyroscope. The aperture and Faraday rotator assemblies contain components which are optically contacted to one another as well as the ring laser gyroscope frame. The assemblies disclosed herein provide a simplified construction designed to fixture the Faraday rotator element in order to minimize handling and facilitate alignment to the ring laser gyroscope cavity, free from contamination and in proper alignment for optimum use of the Faraday rotator component and aperture needed for proper operation of an out-of-plane multi-oscillator ring laser gyroscope.

Abstract: In a fiber-optic communication system, a polarization independent semiconductor optical amplifier structure is achieved by tailoring the height-width aspect ratio of its active region to a value at least close to unity and at the same time using a laser cavity structure in which the end mirrors are buried in the semiconductor body in which the optical amplifier structure is built.

Abstract: A laser comprising a first mirror having a shape. The shape is generally spherical for typical lasers with the shape of the mirror being defined by the radius of curvature of a reflective surface on the mirror. A second mirror is provided mounted with the first to define a laser cavity. The cross-sectional sizes of the modes of oscillation within the laser cavity are defined by the shape of the first mirror. An aperture at a given location having a fixed cross-sectional size is mounted with the laser cavity. Alternatively, a laser bore which forms an effective aperture at a given location is used. A means is mounted with the first mirror for adjusting the shape of the first mirror so that the cross-sectional size of a selected mode at the given location matches the cross-sectional size of the aperture.

Abstract: In a laser device employing an optical resonator which is constructed of a total reflection mirror and a partial reflection mirror, a total reflection plane having an opening is interposed between the partial reflection mirror and the total reflection mirror, the total reflection plane may be formed of, for example, a dielectric thin film or a metallic totally-reflective thin film produced with a cluster ion beam, and the total reflection plane and the total reflection mirror are arranged so as to establish a resonant state. The total reflection plane is formed on an aperture of the partial reflection mirror. The opening of the total reflection plane may be ring-shaped, or a plurality of openings may be provided. The total reflection plane may be located centrally. In a laser device employing an unstable optical resonator, a beam deriving mirror may be disposed within the optical resonator.

Abstract: An adjustable aperture is formed by a plurality of spring members secured over a passage on a frame, each spring member having a first end secured to the frame, a body extending into the passage and a second end opposite the first. The flexible members are mounted so that the plurality of second ends of the spring members form the aperture. A plunger, secured to the frame and contacting the bodies of the spring members, is provided for deflecting the spring members in an adjustable mount along the axis of light going through the passage. By deflecting the spring members which are fixed to the frame, the size of the aperture formed by the second ends of the spring members can be adjusted. The aperture formed is well suited for control of transverse modes in lasers.

Abstract: By using a polarization controller, a semiconductor laser apparatus oscillating in the transverse magnetic mode in mode-locked state is realized, and a short optical pulse is generated. By coupling this mode-locked semiconductor laser to a wavelength conversion element, a second harmonic wave is generated, and an even shorter optical pulse is obtained at a higher power.

Abstract: Diffraction limited, single narrow lobe radiation from a large area laser is achieved in a system using an external ring laser cavity to return radiation to the laser via a spatial filter and a Faraday rotator. An antireflectance coating of sufficiently small reflectivity added to the large area laser converts it into a laser amplifier which provides optical gain in a ring laser cavity.

Abstract: A longitudinally pumped laser is characterized by one segment in which the cavity mode is astigmatic. A solid state medium is mounted within the one segment, so that a volume of the astigmatic cavity mode within the laser medium defines a cavity mode volume. A pump beam is supplied collinearly with the cavity mode through a means causing astigmatic focusing of the pump beam in the laser medium to define a pumped volume within the laser medium. The astigmatically focusing means is mounted according to a precalculated parameter that achieves the best possible average match of the pumped volume with the cavity mode volume, in light of the physical limitations on layout of the resonant cavity. The one segment may be defined by a first off-axis spherical mirror and a second off-axis spherical mirror, with a Brewster-cut solid state medium mounted in between.