Abstract: A non-linear optical device in which quasi-phase matching between different optical waves of differing polarizations and refractive indices increases the interaction length between the waves. The quasi-phase matching structure includes a periodic structure over which the non-linear coefficient varies with a given period, preferably the sign of the non-linear coefficient being inverted between two alternating regions. In LiNbO.sub.3, the periodic structure can be achieved by electrical poling. The required period length is increased by selecting light waves of different polarizations for the non-linear interaction such that a large portion of the dispersion between the waves of different wavelength is compensated by the birefringence of the waves of different polarization. In particular, periodic poling can quasi-phase match radiation in the range of 0.80 .mu.m to 1.2 .mu.m to generate second harmonic generation radiation in the blue and green visible spectrum.

Abstract: In a quantum well semiconductor laser structure, a distributed Bragg reflector is used to select the polarization mode of the emitted light beam. The period of the distributed Bragg reflector matches the peak gain of one polarization mode providing optical feedback for that mode to be the light emitted. The distributed Bragg reflector can extend along the length of the active layer within the semiconductor structure or extend at one end of the active layer external to the semiconductor structure.

Abstract: A distributed gain medium, such as an optical fiber, is configured as a Sagnac interferometer or loop mirror, and this mirror is used as at least one of the two reflectors in the amplifier or laser. The distributed gain medium produces optical signal gain through nonlinear polarization, that may cascade through several orders. The Sagnac interferometer or loop mirror defines two optical paths that will support both common mode and difference mode optical signals. Pump fluctuations resulting from higher cascade orders are at least partially rejected through the difference mode signal path, thereby reducing the overall effect of pump fluctuation. The result is a broadband optical resonator, suitable for use at a variety of different wavelengths, including 1.3 .mu.m and 1.55 .mu.m wavelengths. Amplifiers based on this technology are "four-level," providing a pass through signal even when the pump laser is not functioning.

Abstract: An optical semiconductor device, such as an optical flter and an oscillation polarization selective semiconductor device for switching oscillation polarization modes between two different polarization modes, includes at least one gain region, at least one lossy region, a first control unit for controlling the gain region to control a gain spectrum of the device, and a second control unit for controlling the lossy region to control a cavity loss spectrum of the device such that a polarization dependency with respect to the two different polarization modes is imparted to the cavity loss spectrum. The gain region includes a light waveguide with an active layer which allows the two different polarization modes. The lossy region includes a light waveguide which allows the two different polarization modes.

Abstract: An optical isolator comprises an input polarizer configured to pass light at a predetermined optical polarization axis to a Faraday rotator and thereafter through an output polarizer. A magnet is disposed remotely and laterally away from the Faraday rotator, such that the external field of the magnet maintains the magnetization of the Faraday rotator substantially saturated. In accordance with another aspect of the invention the output polarizer is rotatably adjustable to substantially fine tune the isolator to a given laser wavelength. To this end light is transmitted through an input polarizer, and through a Faraday rotator magnetized in a first magnetization direction so as to rotate the polarization axis of the light passing through the Faraday rotator. The output polarizer is rotatably adjusted until such time that substantially no light travels through the output polarizer.

Abstract: In order to eliminate a mechanically movable section, such as a rotation mechanism of a diffraction grating, to achieve a compact fabrication of the whole apparatus, and to realize stable action for selecting a wavelength, a laser oscillator selecting a wavelength in a wavelength-tunable laser is composed of a laser resonator consisting of a mirror on the input side and a mirror on the output side; a laser medium which is placed in the laser resonator and can oscillate in a predetermined range of wavelengths; a crystal to which is piezoelectric element is attached, the crystal receiving acoustic waves from the piezoelectric element in accordance with a desired wavelength; and a polarizing plate which is placed in the laser resonator and transmits only the output light beam having a prescribed plane of polarization or having a prescribed direction of light propagation among the output light beams from the laser medium. The apparatus thereby outputs only the desired wavelength.

Abstract: An optical device includes a polarization section having a port, the polarization section being for receiving light at the port and for outputting light at the port with a state of polarization orthoconjugate to the light received at the port. The polarization section includes a reflector, a bidirectional nonreciprocal rotator and a bidirectional polarizer. The bidirectional nonreciprocal rotator has first and second ends, the first end being operatively coupled to the port. The bidirectional polarizer has first and second ends, the first polarizer end being operatively coupled to the reflector and the second polarizer end being operatively coupled to the second rotator end.

Abstract: At least a part of a first coherent beam of monochromatic light is incident bliquely on the reflecting surface of a mirror to produce a reflected beam in a direction different from that of the first beam. An interference pattern is produced within a volume defined by the intersection of the reflected beam with the first beam. A part of an optical fiber is positioned in the volume containing the interference pattern, and a grating is photo-induced in the optical fiber by exposure of the optical fiber to the interference pattern. A desired Bragg period in the grating can be selected by tilting the mirror to change the interference pattern.

Abstract: An optical system transmits a first radiation beam along a first axis and receives a reflected beam along that axis; the first beam having a first wavelength and a p-planar polarization; the second beam having the first wavelength, a p-planar polarized component, an s-planar polarized component, and a greater cross-sectional area than the first beam. The system includes a transmit/reflect mirror positioned at a 45.degree. to the first axis and free of apertures in its optical area, a radiation source, an element for directing radiation from the source along the first axis toward the mirror; an element for directing radiation outwardly from the mirror along the first axis, and for directing the second beam along the first axis toward the mirror. An antireflection coating on the primary side of the mirror passes radiation having the first wavelength and a p-planar polarization.

Abstract: A superfluorescent fiber source outputs highly polarized light without a substantial decrease in output power efficiency. According to one embodiment, a polarizer is spliced within the superfluorescent fiber at a selected location along the length of the fiber (e.g., near the middle of the fiber). According to another embodiment, the entire length of the superfluorescent fiber is polarizing to thereby assure that one of the polarizations of light is substantially extinguished while the other polarization of light is nearly double the power which that polarization would have if the polarizer were not present within the superfluorescent fiber. In this manner, superfluorescent sources can be adapted especially for use in fiber optic gyroscopes, or the like, which require highly polarized light, without a substantial reduction in efficiency.

Abstract: Cladding-pumped fibers are used for chirped pulse amplification of ultrashort optical pulses, increasing the average output power by one order of magnitude and substantially decreasing the cost of pump sources. Broad-area multimode diode pumped Er/Yb codoped fiber amplifiers and MOPA pumped high-power Er-doped fiber amplifiers are used to achieve chirped pulse amplification.

Abstract: A monolithic solid state laser structure is used to construct erbium lasers that are insensitive to external pressure changes and vibrations, and have improved cooling of the gain medium and reduced thermal lensing effect. In the monolithic laser structure, the gain medium is separated from an optically transmissive plate on one side and a wave plate on the other side by spacers to form narrow air gaps which provide effective cooling of the gain medium and reduced the thermal lensing effect. Such an arrangement is further combined with a pressure-insensitive Brewster polarizer, such as a solid Brewster polarizer or a pressure-sealed Brewster plate, to form a pressure-insensitive laser cavity. The wave plate cooperates with the Brewster polarizer to select the wavelength of the solid state laser.

Abstract: Apparatus, and a related method, for compensating for birefringence introduced in a birefringent medium, such as a solid-state amplifier. The invention includes the combination of a quarter-wave plate, a Faraday rotator and a mirror, which may be a phase conjugation cell. Light passing through the quarter-wave plate is substantially circularly polarized, which is advantageous if the mirror is a phase conjugation cell using stimulated Brillouin scattering (SBS). A second pass through the quarter-wave plate provides a linearly polarized beam of which the polarization angle is orthogonally related to that of the original beam, to facilitate out-coupling of energy from the apparatus. The Faraday rotator effects a total polarization angle rotation of 90.degree. in two passes and helps compensate for birefringence when the beam is passed through the birefringent medium again on the return pass.

Abstract: A polarized light coherent combining laser apparatus comprises a unit, which is constituted of a compensating phase difference plate, a polarized light separating element, and a phase difference plate. A phase difference and an angle of inclination of principal axes of the phase difference plate are set so as to satisfy specific conditions in accordance with the intensity ratio between two linearly polarized laser beams, which impinge upon the unit. The two linearly polarized laser beams, which have the directions of polarization orthogonal to each other and which impinge upon the unit, are combined with each other by the polarized light separating element. The combined laser beam is converted by the phase difference plate into a beam polarized linearly in a predetermined direction. The resulting beam passes through an analyzer, is reflected by a radiating mirror, and again impinges upon the unit.

Abstract: A diode pumped laser includes a resonator mirror and an output coupler, defining a laser resonator with a resonator optical axis. A strong thermal lens laser crystal with a TEM.sub.00 mode diameter is mounted in the resonator along the resonator optical axis. A diode pump source supplies a pump beam to the laser crystal in the laser resonator, and produces an output beam with a diameter larger than the TEM.sub.00 mode diameter to reduce thermal birefringence. A power source supplies power to the diode pump source. A polarizing element can be positioned in the resonator, along with a aperture stop The laser operates well over a large range of pump powers. Its slope efficiency in the TEM.sub.00 mode is greater than 40%, with an overall efficiency greater than 25%. One of the lasing crystals used is Nd:YVO.sub.4. 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: A pulsed laser includes a polarization section having a port, the polarization section being for receiving light at the port in a selected state of polarization and for outputting light at the port having a state of polarization orthogonal to the selected state of polarization. The laser also includes an amplifying section having a port, a bidirectional amplifier, and a rotator-reflector, the amplifying section being for receiving light at the amplifying section port and for outputting light at the amplifying section port amplified with respect thereto, the bidirectional amplifier being operatively coupled to the amplifying section port at a first end and operatively coupled to the rotator-reflector at a second end.

Abstract: A narrow-band laser apparatus comprises an optical resonator including first and second reflectors for reflecting radiation, a laser medium for amplifying radiation in said resonator and an etalon for selecting a given wavelength component from said radiation. A polarizing beam splitter is provided for linearly polarizing said radiation and also for acting as an output coupler. In order to obtain very narrow bandwidth radiation of high intensity, a Faraday rotator is provided for rotating the plane of polarization while maintaining the linear polarization thereby allowing a second wavelength selection element (such as a grating) to be efficiently employed to further narrow the output of the laser.

Abstract: A solid-state laser is made up of a solid-state laser crystal, a pump source for pumping the laser crystal, a resonator, an etalon disposed in the resonator for selecting an oscillation wavelength, and a nonlinear optical crystal disposed in the resonator for converting the wavelength of the solid-state laser beam. A wedge-shaped optical member, with two light-transmission end faces being not parallel to each other, is disposed in the resonator. A resonator mode is set to a mode, where the maximum output of a solid-state laser beam is obtained with respect to a resonator temperature in the vicinity of a temperature at which the maximum efficiency of wavelength conversion of the nonlinear optical crystal is obtained, by fixing the wedge-shaped optical member at an optimum position. A wedge-shaped nonlinear optical member may be used both as the nonlinear optical crystal and the wedge-shaped optical member, or a wedge-shaped etalon may be used both as the etalon and the wedge-shaped optical member.

Abstract: A laser system includes a linear array of broad area lasers. Such a laser source produces a beam that has a polarization axis in the direction in which the array extends and a coherency axis orthogonal to that. The laser is injection locked by phase conjugating a portion of the array's light output. The phase conjugator has a conjugation axis. The coherency axis is aligned with this conjugation axis. External cavity optics include a polarization rotator to align the polarization axis with the coherency axis before the beam reaches the phase conjugator. Thus, the polarization, coherency, and conjugation axes are all aligned, optimizing the action of the phase conjugator. The approach works in both a single-beam and a dual-beam phase conjugation mode. The result is a laser system output of higher intensity, greater coherence, and a narrower frequency range.

Abstract: An integral optical train comprising a plurality of optical components including a polarized glass element and a light-altering optical element. The polarized glass element may be a glass containing elongated particles of a silver halide selected from the group consisting of AgCl, AgBr and AgI, and the optical element may be a lens or a mirror.

Abstract: A polarized light coherent combining laser apparatus comprises a plurality of units, each of which is constituted of a polarizing element and a phase difference plate. A phase difference and an angle of inclination of principal axes of the phase difference plate of each unit is set so as to satisfy specific conditions in accordance with the intensity ratio between an S-polarized laser beam and a P-polarized laser beam, which impinge upon each unit. The P-and S-polarized laser beams impinging upon each unit are combined with each other by the polarizing element. The plane of polarization of the combined laser beam is rotated by the phase difference plate, and the resulting laser beam impinges upon the next unit. The laser beam having been radiated out of the last unit passes through an analyzer, is reflected by a reflecting surface of a radiating mirror, and again impinges upon each unit. The laser beams having again impinged upon the units are then reflected by mirror surfaces of amplifying media.

Abstract: Power laser includes a non-linear medium (NL1) within which a first beam of fixed direction (I1) and a second beam of orientable direction interfere with each other, an amplifying medium (2) placed along the direction of the first beam for amplifying the received light for transmitting an amplified beam towards the non-linear medium (NL1), which retransmits this bean in the direction of the second beam, and therefore in an orientable direction.

Abstract: An apparatus and method for stabilizing laser light wavelength relative to resonant optical absorption works with both continuous wave and pulsed lasers and employs the phenomenon of Zeeman energy level splitting to provide a error signal indicative of both the direction and magnitude of wavelength error.A laser system including a wavelength adjusting means produces laser light at a wavelength which differs by an adjustable amount from a resonant absorption wavelength of a selected substance. A first portion of the laser light is propagated through a right circular polarizing means to provide right circularly polarized (RCP) laser light. RCP laser light is propagated through a first volume occupied by the selected substance, said first volume being disposed in a magnetic field. The magnetic field vector is substantially parallel to the direction of laser light propagation within the first volume.

Abstract: The optical modulator of the invention comprises an electro-optic material or magneto-optic material EOD which modulates optical energy in accordance with an applied electromagnetic waveform. The electromagnetic waveform impressed in the EOD is controlled by a light activated switch, or switches, which varies the magnitude of the electromagnetic waveform to the EOD by switching portions of a transmission line (of which the EOD forms all or at least a part of the dielectric) in or out. The switch, or switches, may be configured between segments of one of the conductors of the transmission line and may overlay the electro-optic dielectric material. The transmission line may include a plurality of sections, each charged to a selected voltage, so that when switched by said light activated switches, the electromagnetic waveform to the EOD is controlled. When used in a laser cavity, the optical modulator can control the output of the laser cavity in response to optical input control signals.

Abstract: There is disclosed a solid-state laser resonator capable of outputting a high power linearly polarized laser beam, in which a laser beam subjected to the birefringence in the laser resonator is effected to minimize a component of the laser beam which is orthogonal with the direction of polarization definable by a Brewster plate upon traversing a quarter-wave plate, to enable the linear polarization output distribution of the laser beam to become uniform. With this, the emission efficiency and the output power of a linearly polarized laser beam are much improved.

Abstract: A laser system and power control have a polarization state changer that produces in response to an incident beam with selected polarization state at a first wavelength .lambda..sub.1 a beam at .lambda..sub.1 with a desired polarization state. A frequency converter responds to the beam at .lambda..sub.1 with the desired polarization state to produce a frequency converted beam at a second, different wavelength .lambda..sub.2. When the polarization state changer and the frequency converter are located within a laser cavity, the laser system is operable in three different states and produces an output beam at .lambda..sub.1 or .lambda..sub.2, or no output beam, depending on the polarization state changer. In this intracavity configuration the polarization state changer is also operable as a Q-switch.

Abstract: A laser resonator is provided for producing a radially polarized laser beam. The laser resonator includes an active laser medium disposed between a highly reflective end mirror and an opposing partial transmission mirror which define a laser resonator cavity therebetween for producing oscillating optical radiation. A conical Brewster window is further located within the laser resonator cavity and has an optically transparent medium oriented in accordance with the polarizing (i.e., Brewster) angle. As the optical radiation oscillates within the resonator cavity, the conical Brewster window causes the radiation transmitted therethrough to have a radial polarization. Accordingly, the laser resonator produces a laser output which has a radially polarized electric field associated therewith.

Abstract: A phase conjugation mirror (20) for use in a phase conjugation resonator (1). The phase conjugation mirror provides a nonlinear resonance enhancement for a coherent optical signal incident thereon. The phase conjugation mirror is comprised of a semiconductor material having a characteristic bandgap energy selected to be at an absorption bandgap edge, or slightly greater than the absorption bandgap edge, for the coherent optical signal.

Abstract: A laser oscillating apparatus equipped with a folded-type laser resonator designed to fold an optical axis by using a reflecting mirror (11) in addition to an output coupling mirror (4) and a rear mirror (10). The rear mirror (10) consists of a roof reflector having a ridge (10a) set at an angle of .pi./4 with respect to a plane generated by a folded optical axis. At this time, the reflectance of the rear mirror (10) is higher in a linearly polarizing component having an electric-field vector parallel to the direction of the ridge (10a) than that in a component having an electric-field vector orthogonally intersecting the ridge. The laser beam in the resonator is linearly polarized in the direction of the ridge (10a) in an optical path running between the rear mirror (10) and the reflecting mirror (11) closest to the rear mirror (10). The linearly polarized beam is reflected by the reflecting mirror (11). The reflecting mirror (11) generates a total .pi.

Abstract: An optical harmonic generating device is provided with reverse polarization layers which are made of non-linear optical crystal polarized in a lower direction and are periodically arranged at regular intervals, a non-reverse polarization layer which is made of the non-linear optical crystal polarized in the upper direction and is arrange to surround the reverse polarization layers, a wave guide penetrating through alternate rows of the reverse and non-reverse polarization layers, a first electrode arranged on the wave guide, and second electrodes arranged on both ends of the alternate rows. Electric field is induced between the first and second electrodes through the wave guide to change a refractive index of the reverse and non-reverse polarization layers.

Abstract: Saturable absorption, polarization, and retroreflection are integrated into a single solid-state optical element. The optical element comprises an undoped substrate having front and rear surfaces disposed at a predetermined angle. A dielectric coating is disposed on the rear surface of the substrate, and at least one saturable absorber platelet is disposed on the front surface of the substrate. The saturable absorbing species used in the platelet(s) are either F.sub.2 - color-centers in lithium fluoride or Cr.sup.4+ dopant ions in one of several suitable host optical materials. Linear polarization of the laser beam is achieved by orienting the input face of the optical element at Brewster's angle. The dielectric coating (mirror) on the back surface of the optical element provides 100% reflectivity. The optical element is a monolithic, simple to fabricate, easy to align multi-functional element for use in a laser resonator.

Abstract: A driving apparatus for a light source is provided with a light generating unit including a light source which emits a light component polarized in a first predetermined direction and another light component polarized in a second, perpendicular direction. The first and second light components are emitted in amounts which vary depending on the total emitted light output. A light splitter is provided for splitting the two polarized components in different splitting ratios into first and second light paths. A photodetector detects the light intensity in the first light path, and a control unit controls the light generating unit so as to maintain the light intensity in the second light path at a predetermined state based on the detection output of the photodetector.

Abstract: A high-output optical transmitter including a rare earth-doped fiber. The optical transmitter includes a signal light source for outputting signal light having a first predetermined plane of polarization and a pumping light source for outputting pumping light having a second predetermined plane of polarization. The plane of polarization of the signal light from the signal light source is rotated 45 degrees by a Faraday rotator such that the plane of polarization of the signal light output from the Faraday rotator and the pumping light are perpendicular to each other. The signal light from the Faraday rotator and the pumping light from the pumping light source are polarization-coupled by a polarization coupler and the combined light is introduced into the rare earth-doped fiber.

Abstract: A laser diode light source comprises at least two laser diodes (1,2). The beams (3,4) of the diodes (1,2) are combined together by, for example, a polarising beam combiner (11) and the combined beam (18) is focused by a lens (19) onto an optical cable (20). The beams (3,4) are also acted on in the long direction of the laser stripes of the diodes (1,2) by anamorphic beam shaping means (7,8;9,10) to reduce the length of the image formed at the end of fibre (20) by a predetermined factor, chosen such that the numerical aperture of the focused beam (18) in said long direction does not substantially exceed that of the optical fibre (20).

Abstract: A broadband laser which can be electronically tuned to a narrow line by insertion of a frequency selective element in the laser cavity.

Abstract: An unstable laser with improved beam quality has a laser medium and a pair of crossed Porro prism end reflectors positioned to form a resonator defining a light path through the laser medium. Beam expansion optics magnify the beam with each pass through the resonator and is accomplished with a negative lens at one end of the resonator and a telescope at the other end. The negative lens produces a diverging beam through a laser medium in one direction and the telescope recollimates the beam in the reverse direction. Radially varying birefringent compensation is accomplished in the resonator with a crystalline waveplate. Output coupling is achieved through the use of the waveplate in conjunction with polarizer optics.

Abstract: A solid state laser apparatus in which a fundamental laser beam generated in a laser medium is resonated so as to pass a nonlinear optical crystal element provided within a resonator to thereby generate a secondary harmonic laser light and a first optical element for suppressing a coupling caused by a sum-frequency generation between two polarization modes of the fundamental wave laser beam is provided within the resonator includes of a control device for controlling an effective resonator length of the resonator such that the two polarization modes of the fundamental wave laser beam become the same in oscillation intensity. Therefore, a mode hopping noise caused by the mode coupling of the fundamental laser beam within the same polarization mode can be avoided and the oscillation can be stabilized.

Abstract: An eye-safe laser operating at high efficiency, pulse repetition rate and power output is described. The laser comprises a diode-array pumped laser having a pumping wavelength range which produces a polarized output beam. The output beam passes through a nonlinear tunable parametric converter crystal having X, Y, and Z principal axes. Noncritical phase matching is produced in said laser by phase matching for a beam propagation parallel to a principal axis which results in a high efficiency of laser operation. The nonlinear tunable parametric converter crystal converts the wavelength of an otherwise unsafe laser beam output to one that is harmlessly absorbed by the human eye.

Abstract: Laser apparatus is described in which the optical cavity of a laser oscillator is specially provided with a polarizing device which has on its outer face a partially reflecting coating (such as a thin partially reflecting layer of low-loss dielectric material). The polarizing device serves both as an output coupler for narrow linewidth laser emission from the optical cavity and also as a means for substantially suppressing amplified spontaneous emission (ASE). A multiple-prism Littrow-mounted grating (MPL) dye laser apparatus embodying the invention achieves a laser linewidth of less than about 0.1 GHz (.DELTA..nu.), a ratio of intensity I of the ASE to the intensity I.sub..lambda. of the desired laser emission of about 10.sup.-10, an efficiency of somewhat more than 10%, and a short optical cavity length of less than 10 cm. The apparatus is also more rugged, more stable in frequency with changes in temperature, and less costly than similar previous lasers.

Abstract: An improved dye laser having a birefringent tuning filter comprised of one or more birefringent plates wherein each plate is oriented at Brewster's angle to the resonant light beam and is an integer multiple of the thickness of the thickness of the first plate characterized by the fact that the thickness of the first plate is chosen using a new tuning relationship so that a single order tuning curve covers a tuning range of interest. This single tuning curve is almost linear throughout the tuning range and has a tuning angle at the center of the range of approximately five degrees. Also, the tuning curve has a slope throughout the tuning range which provides sensitivity of selected wavelength to tuning angle which is neither too great nor too small. A further refinement in the structure is a non-birefringent polarizing plate at Brewster's angle which increases the losses imposed upon light passing therethrough which is polarized at other than Brewster's angle.

Abstract: Polarization self-modulation of a laser produces high-frequency optical modulation without the use of high-speed electronics. This is accomplished by inserting into a laser cavity a polarization converter, which rotates the polarization of the laser light periodically as the light passes through the converter as it circulates in the cavity. The frequency of the modulation is determined by the cavity length. In one configuration, a quarter-wave retardation plate is used as the intracavity polarization converter in a Fabry-Perot laser. In a second embodiment, the converter is an electro-optic crystal which acts as an electronically-controllable half-wave retardation plate.

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 laser apparatus comprises an optical resonator including first and second mirrors, and laser medium. An wavelength selection element is provided in the resonator for narrowing band-width. A polarizing conversion element for changing ratio of S to P components and polarizing beam splitter are provided for amplifying laser beam to output after wavelength selection and for reducing light load of the wavelength selection element. The polarizing conversion element is provided in the resonator light path. In another embodiment, the polarizing conversion element is provided in a branch light path formed by a second polarizing conversion element and a third mirror, where the second polarizing conversion element reflects and transmits P component at a given ratio and reflects S component. The wavelength selection element comprises a Fabry-Perot etalon, grating, or prism. The polarizing conversion element comprises a quarter-wave plate or a phase retarder mirror.

Abstract: A high power TEM.sub.00 mode Nd:YLF solid state laser includes at least two pumped Nd:YLF solid state rods in series within a laser resonator. A spherical lens may be incorporated within the resonator as required for establishing, in concert with the rods and resonator end mirrors, a large intracavity beam diameter at the position of the rods. A cylindrical lens may be provided to compensate for astigmatic thermal focusing of the Nd:YLF rods, or else the rods may be used in pairs, in which case the rods are rotated by 90.degree. about the laser axis with respect to each other, and a half-wave plate is inserted between the rods of each pair to maintain oscillation at a single wavelength.

Abstract: Rotational displacement of the birefringent lasing medium in a lasing cavity containing a polarizing element varies the spectral width of the generated laser light. The combination in a lasing cavity of a birefringent lasing medium, a polarizing element, a tuning element and a birefringent compensator permits output of narrow bandwidth spectrally tuned laser light continuously over the total gain bandwidth of the lasing medium by rotating the lasing medium, tuning to desired wavelength, and adjusting the birefringent compensator to optimize output of laser light.

Abstract: A laser amplifier in which the effective refractive index of the active region for the TE and TM modes is sufficiently different to provide multiple mode ripple beat frequency overlap within a 3dB gain envelope peak. The active region is made highly asymmetric with an aspect ratio of at least 10:1 and preferably 20:1 in order to provide the effective refractive index difference. Steps, grading or uniform difference in the material refractive index may also be used. The confinement factor ratio is made as high as possible by providing different material refractive index in the orthogonal dimensions of the active region cross section.

Abstract: In a semiconductor laser module with a built-in optical isolator which isolator consists of a polarizer, a Faraday rotator and an analyzer, an optical refraction sheet having a wedge-shaped section is disposed on the beam incidence side of the polarizer. Accordingly, even when the mechanical center axis of the optical isolator is placed to be in parallel with the optical axis of the semiconductor laser or in other words, even when the beam incidence-outgoing surfaces of the polarizer, Faraday rotator and analyzer are placed to be vertical to the incident parallel beams, the parallel beams incident into the optical isolator are refracted by the optical refraction sheet having the wedge-shaped section, so that the parallel beams passing through the beam incidience-outgoing surfaces of the polarizer, Faraday rotator and analyzer do not pass vertically and the return of reflected beams to the semiconductor laser can be thus reduced.

Abstract: An antiresonant nonlinear mirror to replace one mirror of a laser for passive modelocking of the laser, the antiresonant nonlinear mirror comprising: a beam splitter for coupling the mirror to a laser cavity; a mirror arrangement for defining an optical ring with the beam splitter in which two light beams produced by the beam splitter in response to a light beam from the laser cavity can counterpropagate around the ring; an intensity dependent anisotropic nonlinear element disposed within the ring; and a polarization sensitive element disposed within the ring for adjusting the birefringence thereof to produce spontaneous modelocking in the coupled laser cavity.

Abstract: In a gas laser having integrated mirrors wherein two longitudinal modes of the laser oscillation are excited during operation, and wherein the oscillatory planes thereof reside perpendicularly relative to one another, a stabilization of the angular position of the oscillatory planes is achieved in that an optically birefringent element is arranged in the beam path of the optical resonator.

Abstract: A laser for use in all fields of measurement using a heterodyne effect delivers two waves at different frequencies, having mutually orthogonal linear polarizations. It comprises a lasing medium placed in a laser resonating cavity defined by mirrors and a birefringent crystal placed on the path of the two waves. The lasing medium is located in the resonating cavity in a zone where the two waves are separated spatially. Two quarter wave plates, one of which has neutral lines at substantially 45.degree. from the polarization axes of the birefringent means, are placed in the common path of the two waves so as to give a helical polarization to the two waves between the plates.