Abstract: A diode laser array comprises a substrate of a semiconductor material having first and second opposed surfaces. On the first surface is a plurality of spaced gain sections and a separate distributed Bragg reflector passive waveguide at each end of each gain section and optically connecting the gain sections. Each gain section includes a cavity therein wherein charge carriers are generated and recombine to generate light which is confined in the cavity. Also, the cavity, which is preferably a quantum well cavity, provides both a high differential gain and potentially large depth of loss modulation. Each waveguide has a wavelength which is preferably formed by an extension of the cavity of the gain sections and a grating. The grating has a period which provides a selective feedback of light into the gain sections to supporting lasing, which allows some of the light to be emitted from the waveguide normal to the surface of the substrate and which allows optical coupling of the gain sections.

Abstract: Photons of an electromagnetic source wave are frequency-upshifted as a plasma is rapidly created around the path of this propagating source wave. The final frequency can be controlled by adjusting the gas density. A controlled time-varying frequency (chirped) pulse can be produced by using a controlled spatially varying gas density. The plasma must be created in a time which is short compared to the transit time of the light through the plasmas region. For very fast creation over one to at most a few light periods of an overdense plasma, static magnetic fields with short wavelengths are created.

Abstract: A system and method for producing relatively square laser pulses derived from relatively Gaussian laser pulses. The system comprises a phase conjugate laser system that comprises a laser oscillator, an amplifying medium and a phase conjugate mirror having a nonlinear confined at a predetermined pressure. The mirror is adapted to truncate the front portion of an applied laser pulse. A plasma switch is disposed between the laser oscillator and the amplifying medium that has a gas confined therein at a predetermined pressure. The plasma switch and phase conjugate mirror cooperate to truncate the laser pulse to produce a laser pulse having a relatively square shape. Controlling the pressures in the plasma switch and phase conjugate mirror provides a means of controlling the formation of square-shaped laser pulses. In addition, a delay line may be employed in the system that is controllable in length that assists in controlling the truncation of the pulse in the plasma switch.

Abstract: A traveling-wave device for amplification of RF signals at microwave frequencies, primarily from UHF to submillimeter wavelengths, comprised primarily of broad-coupled parallel striplines of which one is a cathode stripline and the other a non-intercepting gate stripline disposed between conducting plates. Electrons are emitted from the cathode stripline and accelerated by DC electric fields through the non-intercepting gate stripline on which the microwave signal is propagating in a transmission mode which has reversed directions of the microwave electric field on each side of the gate stripline. The odd mode component of the microwave electric field, between the gate stripline and cathode stripline, serves to modulate and/or stimulate electron emission from the cathode stripline and the reversed direction of the microwave electric field between the gate stripline and the conducting plate decelerates the electrons to add their energy to the propagating wave for amplification.

Abstract: The effective reflectivity of angled antireflection-coated facets of a traveling-wave laser amplifier is significantly reduced by flaring the waveguiding portion of the amplifier in the immediate vicinity of the facets. In this way, low-reflectivity facets are achieved with simple low-cost antireflection coatings, thereby providing economical amplifiers characterized by wide bandwidth and high output saturation power.

Abstract: This invention is directed toward reducing substantially the loss incurred when two optical fibers of different mode diameters are coupled together. In this invention, the coupling of one fiber to that of another where the fibers are of different mode diameters is not with a tapered fusion, core-to-core splice, but with an evanescent field fiber coupler. Briefly, to achieve amplification of a weak optical signal, an amplifying fiber is inserted into the system at one or a plurality of locations. More specifically, at a desired location, the transmission fiber is severed to provide two sections and the severed sections are transversely coupled to the amplifying fiber. The weak signal from the first section of the transmission fiber is coupled into the amplifying fiber via a first evanescent field type of fiber coupler; and the amplified signal is coupled from the amplifying fiber to the second section of the transmission fiber via a second evanescent field type of fiber coupler.

Abstract: A high signal reception efficiency, multi-channel Bragg cell is provided for an interferometric acoustooptic signal processor. The Bragg cell comprises a block of acoustooptic material which is illuminated on one block surface by a laser beam. A plurality of sets of electroacoustic transducers are mounted on another surface of the block which is normal to the first block surface and each transducer set is responsive to the output of a different one of a plurality of antennae so that the laser beam is acoustooptically modulated by the signal outputs from the antennae as it passes through the block. The transducers are arranged in a phased array comprising the plurality of transducer sets. A Fourier transform lens receives and focusses the modulated beam from the block to produce a two dimensional display which represents the power spectrum of the antennae outputs as a function of the angles of incidence of the antennae with respect to an incoming electromagnetic wavefront.

Abstract: A deflectable beam spatial light modulator formed from a structure of a reflecting layer, typically metal, on a spacer layer, typically photoresist, which in turn is on a substrate containing electronic addressing circuitry is disclosed. Also, the method of fabrication including a plasma etch after dicing of the substrate into chips is disclosed.

Abstract: An electrostatically deflectable plate spatial light modulator with light reflecting plates (106) composed of aluminum alloy and with symmetrically located supporting hinges (108) connecting the plates (106) to support posts (104); this provides a thick stiff plate and a thin compliant hinges with deflection perpendicular to the plane of the plates.

Abstract: A device for amplifying an input optical signal includes an optical amplifier having a gain control region in which the input optical signal is amplified, a first detecting region for detecting the input optical signal, and a second detecting region for detecting an amplified optical signal. The gain of the optical amplifier is controlled by a gain control signal from a signal source. A controller, responsive to detecting signals from the first and second detecting regions, produces a source control signal which is supplied to control the signal source.

Abstract: A gas laser with a discharge bore defined by a single-bore extruded ceramic discharge tube is disclosed. An outer tube is located over the discharge tube so as to define an annular space therebetween. Caps are located over both ends of the tubes and each cap is provide with at least one gas transport passage so the discharge bore and the annular space are in communication. The annular space is filled with electrically insulating, thermally conducting components such as washers, baffles and ceramic granules. When the laser is in operation the annular space serves as a gas return path so a uniform equilibrium pressure is maintained in the discharge bore. The components in the annular space inhibit the flow of electrical current in the space so all of the current flow is through the discharge bore so as to excite the gas therein. The components in the annular space also provide a thermally conductive path between the discharge tube and the outer tube to diffuse heat away from the discharge bore.

Abstract: An interferometric acoustooptic signal processor utilizing a circular antenna array to cover a 360 degree field of view. Each antenna element of the array is connected to an input port of a Butler matrix. The signals are phase shifted within the Butler matrix and applied to a multi-channel periodic Bragg cell, resulting in generation of one or more acoustic waves therein. A laser beam is used to illuminate the Bragg cell and is modulated due to interaction with the acoustic waves, resulting in diffraction of the laser beam and generation of a diffracted beam pattern output from the Bragg cell. A Fourier transform lens focuses the diffracted laser beam on a back focal plane at a point characterized by two perpendicular coordinates designating the input signal power spectrum and the angle of incidence in relation to the antennae, respectively.

Abstract: An improved adaptive optics system is disclosed for correcting atmospheric phase aberrations. A satellite (10) laser beacon is operated at the Stokes shifted Raman wavelength. After passing through the atmosphere (A), the signal is phase conjugated (16) and amplified in the Raman amplifier (12). The result is a high energy laser beam with phase conjugated aberrations which may be returned to the satellite (10).

Abstract: A single frequency lightwave system employs semiconductor, optical amplifiers arranged in tandem with suitable nose filtering and isolation between amplifier stages. Feedback control maintains overlap between the signal frequency and one of the passbands of the amplifiers. Either direct detection or coherent detection can be used. Also described is a receiver front end which includes such an amplifier between the incoming signal and a photodetector. Both transmission systems and switching systems are described.

Abstract: A method of and an apparatus for projecting an incident laser beam into a broad contact-type light amplifier. The laser beam is projected after the intensity distribution of the laser beam is made to coincide with the electromagnetic field distribution in the fundamental mode of the light amplifier. Since only the fundamental mode is used as the propagation mode of the light amplifier, a Gaussian beam amplified by the light amplifier is emitted. Consequently, the laser beam emitted from the light amplifier can be made into a several-micron spot by condensing the laser beam to a diffraction limit.

Abstract: A four-pass conjugate optical amplifier system and method are disclosed in which a linear polarized optical beam is directed by various optical elements through four passes of a power amplifier, preferably a diode laser structure. The beam is phase conjugated at the optical midpoint between the second and third amplifying passes, and is controlled by the optical elements so that its polarization is substantially the same during the first and second passes, and again substantially the same during the third and fourth amplifying passes. This is accomplished by a reflective coating on the back facet of the diode laser structure, with a non-reciprocal polarization rotation element located in the beam path between the phase conjugate mirror and power amplifier. For considerably enhanced power amplification, the beam may be divided into an array of subbeams, which are individually amplified by four passes through respective power amplifiers.

Abstract: A polarization independent semiconductor amplifier is used in a double-pass configuration; that is, the output of the amplifier is passed through a 45.degree. Faraday rotator to a mirror and then through the rotator and the amplifier again. Polarization independent gain is thus achieved.

Abstract: A surface emitting grating is coupled to an optical amplifier and has grating elements tilted non-normal relative to the amplifier optical axis. The angle of tilt in one embodiment is such that the grating reflections are refracted out of the amplifier region. The amplifier may have a tilted light receiving end serving as an input port in a second embodiment to cause internal reflections from the grating to be reflected to an amplifier boundary at an angle greater than the critical angle to cause the reflections to pass out of the amplifier region. In the latter embodiment, the grating tilt angle is minimized to reduce the surface emission beam angle tilt from the normal to a relatively small angle.

Abstract: An improved semiconductor optical amplifier with shortened gain-recovery time is disclosed. In the inventive device a carrier-storage region is placed adjacent to the gain region of the amplifier. Passage of carriers from the storage region to the gain region rapidly replenishes the carrier population within the gain region, thereby permitting rapid recovery of the amplifier gain.

Abstract: A superfluorescent broadband fiber laser source comprises a fiber doped with laser material coupled to a multiplexing coupler. In the preferred embodiment, a source of pumping illumination provides pumping light to the doped fiber, and the coupler is adjusted to have a 0% coupling efficiency at the wavelength of the source. The pumping light is sufficiently intense to produce amplified spontaneous emission within the doped fiber, and gives rise to a forward signal and a backward signal. One of the superfluorescent signals is reflected back to the doped fiber by a reflector cemented to one end of the doped fiber or to one end of another fiber through the coupling function of the coupler. The coupler is adjusted to provide complete coupling at the frequency of the lasing light. The temperature dependence of the coupler can be selected to reduce or cancel the temperature dependence of the superfluorescent signal. Other arrangements utilizing the multiplexing properties of the coupler are also described.

Abstract: An optical beam scanner incorporating an array of beam deflection elements commonly controlled to steer an optical beam impingent on the array is described. The beam steering elements are arranged in the array as individually controlled elements and the deflection of the beam is accomplished by setting the phase tilt and the phase offset of each element according to a calculation which removes modulo 2.pi. phase shift from the required position relative to a flat plane. Thus, the array elements can be thin and need only supply about 2 radians of phase shift. These elements may be incorporated in a planar array using beam deflection elements such as liquid crystal beam deflectors by choosing a drive scheme representing either a blazed array or a flat piston array.

Abstract: Photons of a laser pulse have their group velocity accelerated in a plasma as they are placed on a downward density gradient of a plasma wave of which the phase velocity nearly matches the group velocity of the photons. This acceleration results in a frequency upshift. If the unperturbed plasma has a slight density gradient in the direction of propagation, the photon frequencies can be continuously upshifted to significantly greater values.

Abstract: A technique for coherent aperture filling by amplitude phase exchange is described which suppresses the far field side lobes of an array of lasers. The power contained in these side lobes is transferred to the central lobe so that it contains greater than 90% of the total array power. This is achieved by a field transformation which generates from the uniform phase and varying amplitude distribution of the input array a varying phase modulation with nearly uniform, i.e., aperture filled, amplitude distribution in the output beam. Far-field grating lobes from the nonuniformity in phase are then suppressed by an additional phase correcting element matched to compensate the phase modulation. In a preferred embodiment, the field transformation element, including a single step binary phase shifter flanked by a pair of lenses in an a focal imaging configuration, is followed by a binary phase grating for phase compensation.

Abstract: A coupled-cavity circuit for a microwave electron tube is shown having one or more cavities whose cross-sections are polygonally shaped, such as rectangles. Located in one or more corners of the polygonally shaped cavities are irises which have a higher resonant frequency. These irises are generally triangularly shaped with rounded corners and one leg of the triangle rounded about the drift tube of the microwave electron tube.

Abstract: An ultrafast traveling wave optical modulator capable of functioning at frequencies greater than 100 GHz having an optical waveguide parallel to a transmission line. The optical waveguide is in a substrate of electro-optic material (GaAs with GaAlAs layers forming the optical waveguide). The transmission line is a pair of coplanar electrodes on the substrate. A superstrate having an effective dielectric constant substantially equal to the square of the index of refraction of the substrate (a GaAs body in which the electric field on the line is substantially confined) eliminates the mismatch in velocity of propagation of the traveling electrical and optical signals thereby increasing the response time of the modulator so that it can function when the electrical modulating signal on the line exceeds 100 GHz in bandwidth.

Abstract: A crossed-field amplifier circuit of the type using a CFA tube with a slow-wave structure for the anode and the cathode, each with an input and an output terminal, and a magnetic field in the axial direction, and signals of the same frequency from a common source and of controlled phase difference and amplitude applied to the input terminals of the anode and cathode slow-wave structures whose fringing fields interact with the electron cloud between the anode and the cathode to form well defined cloud fingers which result in amplification of the input signals to provide at the output terminal of the anode an amplified signal having lower random noise than hitherto available from CFA amplifiers.

Abstract: An optical amplification method or system for an optical communication system which transmits signal light from the transmitting side to the receiving side via an optical transmission medium formed by an optical fiber or space. In accordance with the present invention, the signal light entered a certain state of polarization in at least one part of the transmitting side, the receiving side and the optical transmission medium is separated into two orthogonal polarized waves by a polarizing beam coupler/splitter. The two polarized waves are amplified by optical amplifiers disposed in correspondence to their state of polarization, respectively. The amplified orthogonal polarized waves are combined together by another polarizing beam coupler/splitter.

Abstract: A laser amplifier with high gain and high power efficiency comprises a gain medium characterized by at least two optical paths through the gain medium. An optic supplies the input laser pulse along a first optical path, so that the laser pulse has a transverse dimension D.sub.i as it propagates along the first optical path and exits the gain medium as a first pass amplified pulse. A second optic expands the first pass amplified pulse in the transverse dimension to an expanded pulse with transverse dimension D.sub.e, and guides the expanded pulse along a second optical path through the gain medium. The laser pulse exits the gain medium as a second pass amplified pulse. A third optic in a preferred system guides the second pass amplified pulse along a third optical path through the gain medium so that the laser pulse exits the gain medium as the output pulse.

Abstract: Briefly, in this invention, the output optical power of an optical amplifier is determined by detecting and measuring the electrical signal induced on the bias lead of the optical amplifier when an optical data stream with additional amplitude modulation passes through the optical amplifier. This additional amplitude modulation can consist of a base band signal, a pilot tone and/or a sub-carrier which is amplitude modulated, frequency modulated or phase modulated. The modulation depth and bandwidth of the additional amplitude modulation should be kept small enough that the data stream is not excessively affected. The induced electrical signal provides a measurement of the optical power at the output facet of the optical amplifier. Control of the output power of the optical amplifier is effected by controlling the bias current applied to the bias lead of the optical amplifier.

Abstract: A multi channel averaging circuit for use with an optical sensing system utilizing back-scattering light for establishing the scattering profile along a fibre sensor, e.g. to determine the temperature distribution along the optical fibre sensor. The circuit comprises a number of connected in parallel, charge coupled devices (3-9) energized by a clock (10) and arranged to store successive elements of a signal waveform derived from the back-scattered light. The stored analogue signals are fed sequentially into the averaging circuit (11), sampled, and then digitized by an A to D converter (13).

Abstract: An optical semiconductor device comprises cathode and anode regions, and a gate region having a forbidden band gap narrower than those of the cathode and anode regions. The gate region is sandwiched by the cathode and anode regions. The optical semiconductor device further comprises a plurality of windows for receiving and radiating lights so that the alignment of light axes can be easily performed for a plurality of input and output lights.

Abstract: A surface state photodiode is used as the photosensitive element for a Spatial Light Modulator, which includes a liquid crystal layer. The surface of the photodiode which faces the liquid crystal layer has formed thereon surface states, by means of adsorption of foreign molecules to create a depletion layer, thereby effecting a high dark impedance region. Such a Spatial Light Modulator provides for a high resolution image and simplicity in manufacture.

Abstract: The source and the device comprise a generator of a pump wave, optical means for coupling with a monomode optical fiber for guiding and highly confining the pump wave so that a four photon non linear interaction is created. At least one section of this optical fiber is disposed in a thermostat controlled enclosure associated with a temperature control device so as to obtain continuous tuning in a range of frequencies belonging to the near infra red spectrum.

Abstract: A staggered quadrature phase shift keyed modulator which avoids the need for timing circuits. Three phase modulators serially change the phase of a laser beam so that it may sequentially have a total phase shift of .pi., .pi./2, 0, -.pi./2. The input signal is divided into two pulse trains, one of which is delayed to provide the stagger. The two pulse trains are logically combined to form three control signals for the modulators.

Abstract: In an eye-safe coherent laser radar, a laser diode optically pumps a solid state non-planar ring laser to produce the coherent output laser radiation. The laser radiation is passed through a Faraday isolator to an optically pumped slab three-stage linear amplifier imparting 56 db gain. A telescope transmits the amplified laser radiation to illuminate a target. Optical radiation returned from the target is collected by the telescope and focused into a single transverse mode fiber-optic waveguide for combination in the fiber with reference lasant radiation by means of a single mode fiber coupler. The combined optical radiation is then detected by a photodetector to produce a difference frequency output representative of parameters of the target.

Abstract: An improved phase conjugate master-oscillator power-amplifier laser system for providing a high-power low-distortion laser output beam. The system includes an improved oscillator such as a ring oscillator which rejects any of the output beam which is inadvertently fed back to the oscillator, thereby preventing unwanted oscillation. The system also includes an attenuator such as a spatial filter or an optical isolator that attenuates any amplified spontaneous emissions that may be reflected from the power amplifier to the oscillator, thereby preventing oscillator degradation that would otherwise result. The invention is particularly well-suited for a laser system which employs an SBS mirror for phase conjugation.

Abstract: A tilt-angle gun provides a conically-shaped electron beam formed in a magnetically-shielded region which is injected into a coaxial waveguide of the amplifier embodiment of the invention and into a coaxial cavity of the oscillator embodiment immersed in the main magnetic focussing system to form a hollow gyro beam of large radius. RF power input and the amplified rf power output are simply and easily provided through circular input and output waveguides coupled respectively to each end of the coaxial waveguide by slotted sections. The electron beam and the output rf energy are naturally physically separated so that extraction of the rf output is facilitated and occurs with little rf power loss.

Abstract: A novel single sideband electro-optic modulator includes a planar waveguide structure allowing only circularly polarized optical and microwaves to propagate therein with equal phase velocities comprises a strip loaded GaAlAs/GaAs/GaAlAs structure with appropriate microstrip electrodes. The present modulator is readily fabricated using established microelectronic fabrication techniques and a modified MOCVD epitaxial growth process.

Abstract: A CW pumped regenerative laser amplifier system capable of producing amplified laser pulses of variable repetition rate (e.g., 10 Hz to 10 kHz) with high energy stability. The regenerative amplifier is seeded by pulses injected into the optical cavity of the amplifier from a CW pumped modelocked laser.

Abstract: A semiconductor diode structure including a light-absorbing substrate, an active region, and a pair of cladding layers surrounding the active region. Lasing is inhibited by means of an inclined end facet, which reflects light down into the substrate, where it is absorbed, to provide only one pass of the spontaneously emitted light through the active region. One disclosed embodiment has a conventional end facet for the out-coupling of edge-emitted light. Another embodiment includes a surface-emitting facet formed in an opening in the substrate adjacent to the inclined facet. Yet another embodiment has two inclined facets. One inclined facet may serve to reflect light into the absorbing substrate, or both may serve to reflect light through separate surface emitting facets.

Abstract: A nonlinear optical fluid with radiation-absorbing small particles uniformly suspended in the fluid. For radiation below a threshold value, radiation passes through with slight attenuation. Above the threshold, only a limited level of radiation is passed, the limit being below the damage level of a sensitive optical detector.

Abstract: An optical modulator comprises a crystal (15) of material exhibiting the pyroelectric effect, and charge-dissipating means for dissipating any charge built up on the optical faces of the prism. The charge-dissipating means may comprise point electrodes (30) positioned adjacent to the optical faces (21) of the crystal and connected to an alternating-current high-voltage power supply (31). The electrodes produce charged ions which neutralize any charge on the optical faces of the crystal. The crystal may be used as the Q-switch in a laser.

Abstract: A wavelength resonant semiconductor gain medium is disclosed. The essential feature of this medium is a multiplicity of quantum-well gain regions separated by semiconductor spacer regions of higher bandgap. Each period of this medium consisting of one quantum-well region and the adjacent spacer region is chosen such that the total width is equal to an integral multiple of 1/2 the wavelength in the medium of the radiation with which the medium is interacting. Optical, electron-beam and electrical injection pumping of the medium is disclosed. This medium may be used as a laser medium for single devices or arrays either with or without reflectors, which may be either semiconductor or external.

Abstract: A method and apparatus for phase conjugate optical modulation involves creating a phase hologram within a nonlinear medium by overlapping, within the nonlinear medium, a pair of laser beams, travelling along paths angled slightly with respect to one another. A third beam reads this hologram to produce the phase conjugate wave. An electric field is generated through the medium transversely to the overlapping laser beams within the medium. The intensity of the output conjugate beam is modulated according to the field strength of the applied electric field.

Abstract: A microwave signal linearizer for a travelling wave tube amplifier (TWTA) provides for simple and flexible adjustment of a predistortion network suitable for independently compensating for a wide range of travelling wave tube amplifier-induced distortions. The linearizer or predistortion network is formed by three divided parallel passive microwave signal channels, the first channel having a coaxial microwave limiter diode network, the second channel having a variable attenuator for adjusting amplitude modulation (AM/AM) non-linearity, and a third channel for adjusting amplitude modulation to phase modulation (AM/PM) non-linearity. Signals directed to the first and second channels are combined in a 180.degree. hybrid network to produce a difference signal which is directed through a difference channel to a 90.degree. hybrid network. The signals through the third channel are directed to the 90.degree.

Abstract: A narrow-bandwidth, unstable laser resonator comprising: an output section ncluding a laser gain medium for generating and amplifying light, a first reflective element for reflecting and collimating light from the gain medium back through the gain medium, and a second reflective element having a hole therein, the second reflective element being responsive to the collimated light passed through the gain medium for reflecting most of the collimated light out of the unstable laser resonator as an output beam and for passing the remaining portion of the collimated light through the hole therein as a residual beam; and a feedback ring including an optical path, a beam splitter for passing a first portion of the residual beam into the optical path in a first direction, a frequency-narrowing element disposed at a position in the optical path where the first portion of the residual beam is collimated, the frequency-narrowing element being operative to narrow the frequency bandwidth of the first portion of the residua

Abstract: A single mode optical fiber is used to detect electrical currents or magnetic fields from a source to a high degree of accuracy. Phase modulation of an optical beam is used to determine the changes of physical properties of a magnetostrictive material which jackets the fiber or around which the fiber is wound. An electromagnetic field, such as that emanating from a high intensity field wire, is measured by the device which acts as a current transformer and meters peak-to-peak electric currents of approximately 10,000 amperes or more with accuracy exceeding 0.1%. The invention structure of the device provides advantages such as operation safety, EMI immune leads, low cost, light weight, and dielectric construction among others.

Abstract: A power supply for helix and collector electrodes of a traveling wave tube is driven by an AC power source having a frequency of at least 500 KHz. The helix supply includes plural, stacked voltage double AC to DC modules responsive to the 500 KHz source. The collector supply includes plural AC to DC modules, each having a diode full wave rectifier bridge, connected in stacked relation. Each of the modules includes a transformer with a ferrite, toroidal core dimensioned so that it is not driven into saturation by the 500 KHz source. Each module also includes inexpensive, signal switching diodes having a recovery time of approximately 4 nanoseconds. The ratio of the collector to helix DC voltages is maintained constant by threading a common lead through the apertures of the toroidal cores of the helix and collector modules. A separate common lead threaded through the apertures of the toroidal cores in the collector modules is connected directly to the 500 KHz power source.

Abstract: To provide a solution of the problem of medium dispersion in a two-line Raman amplifier which may increase the intensity-length product requirement and limit the conversion efficiency. By adjusting the angles between the input beams, the four-wave mixing phase mismatch due to medium dispersion may be eliminated. This couples together the Raman gains of the two lines so that the effective pump intensity for each is the total pump intensity. Since both lines convert in about the same amplifier length, independent of the relative power in each, the conversion efficiency is not limited by the inability to optimize the length for both lines simultaneously.

Abstract: An acousto-optic tunable filter (AOTF), instead of being used for its intended use of frequency or wavelength tuning a laser from within its resonant cavity, is used outside the laser cavity to amplitude modulate the output beam of the laser. This is accomplished by directing the laser output beam into the AOTF and applying an A.C. voltage to a piezo-electric transducer which is a part of the AOTF.