Abstract: A laser includes a gas enclosure placed in an optical cavity and receiving a pump beam to generate at least one first-order and one second-order Stokes wave. One of the mirrors of the cavity is transparent to wavelengths which are higher than the first-order Stokes wave.

Abstract: An optical beam steering device (10) incorporates a laser (12), three Brillouin shifters (22 to 26, 44 to 48, 54 to 58), a four wave mixing cell (40) and a low power beam steering device (62). The first shifter (22 to 26) and the mixing cell (40) contain TiCl.sub.4, and the other shifters (44 to 48, 54 to 58) contain 20% CCl.sub.4 /80% CS.sub.2. The first and third shifters (22 to 26, 54 to 58) frequency downshift the laser beam (16) by .delta..upsilon..sub.A and .delta..upsilon..sub.B respectively. Light (16') from the first shifter (22 to 26) is amplified and provides a first pump beam input to the mixing cell (40). It then passes to the second shifter (44 to 48), for frequency downshifting by .delta..upsilon..sub.B and returns as a second cell pump beam ( 16"). Light (18') from the third shifter (54 to 58) passes via the low power beam steering device (62) to the cell (40) as a weak input signal beam (18").

Abstract: Novel optical fiber devices (amplifiers and lasers) are disclosed. The devices comprise one or more optical "cavities", depending on the type of device. The cavities typically are formed by means of in-line refractive index gratings in a length of silica-based optical fiber. The gratings typically have peak reflectivity of at least 98%. Use of such cavities enables CW pumping of the devices, making the devices suitable for use in optical fiber communication systems. In an exemplary embodiment the device is a Raman amplifier for 1.3 .mu.m signal radiation, and in another exemplary embodiment the device is a Raman laser having an output suitable for pumping an Er-doped fiber amplifier. An exemplary pump radiation source is a laser diode-pumped CW Nd:YAG laser.

Abstract: A raman cell oscillator/amplifier arrangement comprising a cell containing a raman high pressure gas or liquid medium with an axicon being located at each end of the cell, one axicon having an input window for a laser pump beam and the axicon at the cell's other end having an output coupler for the raman process converted beam. The axicons directs the laser pump beam towards an extended line focus along the axis of the cell at a shallow angle, the extended line focus for each axicon being collinear with each other to produce an extended raman gain region. By suitable design, it can be ensured that the pump beam energy density at focus is lower than either an optical breakdown or Brillouin backscatter threshold. This provides a means of efficiently producing a raman laser or amplifier having an extended raman gain region without developing problems of optical breakdown, Brillouin backscattering or self-focusing in the case of a liquid raman media.

Abstract: This invention provides a Raman laser wherein a light beam from a laser source (1) passes through a first chamber (3) and experiences Raman scattering, and then passes through a second chamber (9) and experiences further Raman scattering, such that the output of the Raman laser is frequency shifted. The first and second chambers may be distinct from each other enabling different types and pressures of gases to be utilised, or may be one and the same (20) providing a particularly compact arrangement. A Raman laser in accordance with the invention is particularly suitable for the production of light consisting of multiple rotational Raman orders, and particular embodiments enable frequency switching to be achieved and also provides arrangements which reduce the problems of boresight stability and gas circulation encountered with previous designs.

Abstract: A single focus backward Raman laser that is a compact, efficient apparatus for converting light at a first wavelength provided by a pump laser to light at a Raman-shifted wavelength. The laser is comprised of a gas cell, two lenses, a feedback mirror, an optical isolator, and a dichroic mirror, and the gas cell contains a Raman gas medium. The Raman gas medium may be methane, hydrogen, or deuterium, for example. The two lenses bring the pump and Raman light to a single focus in the gas cell and also recollimate the light after it exits the cell. The optical isolator is used to prevent the backward-scattered pump light from reentering the pump laser. The dichroic mirror is used to reflect out the backward-scattered Raman light, while transmitting the pump laser light. The present laser has a much improved beam divergence and is much less sensitive to optical misalignments than conventional Raman half-resonator designs.

Abstract: According to the invention, the Brillouin-effect radiation created in the Raman cavity (14) is returned into the pumping laser (1) to increase the Raman output power.

Abstract: A pulse compression and prepulse suppression apparatus (10) for time compressing the output of a laser (14). A pump pulse (46) is separated from a seed pulse (48) by a first polarized beam splitter (20) according to the orientation of a half wave plate (18). The seed pulse (48) is directed into an SBS oscillator (44) by two plane mirrors (22, 26) and a corner mirror (24), the corner mirror (24) being movable to adjust timing. The pump pulse (46) is directed into an SBS amplifier 34 wherein SBS occurs. The seed pulse (48), having been propagated from the SBS oscillator (44), is then directed through the SBS amplifier (34) wherein it sweeps the energy of the pump pulse (46) out of the SBS amplifier (34) and is simultaneously compressed, and the time compressed pump pulse (46) is emitted as a pulse output (52). A second polarized beam splitter (38) directs any undepleted pump pulse 58 away from the SBS oscillator (44).

Abstract: The present invention provides a Raman laser wherein hazardous radiation from a pump laser source 20 is focused by lens 25 via a cell 27 containing a Raman active medium before passing to a absorbing beam dump 30. Lasing action is maintained within the cell 27 by the action of mirrors 29 and 26 which are respectively totally and partially reflective to radiation generated at the Raman wavelength, and which are both transmissive to the pump beam. A Raman beam exits the cell via partially transmissive mirror 26 is refocused by lens 25 and passes through to the output of the device 31. This configuration provides a Raman laser where the "eyesafe" Raman beam is generated in a backwards direction relative to the pump beam, so that during normal operation, or in the event that the optics breakdown, or conversion does not take place within the cell, the output beam would not be contaminated by potentially harmful wavelengths at a hazardous level.

Abstract: Intracavity Raman lasers comprising a pump resonator and a Raman resonator that eliminates alignment problems associated with multi-mirror intracavity lasers. The pump resonators include a laser rod and a pump source. In one embodiment, a first retroreflector is disposed at one end of the pump resonator, and an output mirror is disposed at an opposite end thereof. A Q-switch, a dichroic mirror, and a prism are disposed between the laser rod and the output mirror. The pump resonator radiates pump energy at a first wavelength (1.06 .mu.m) between the first retroreflector and the output mirror. The Raman resonator includes a Raman gas cell having first and second lenses disposed on opposite ends thereof for focusing laser energy into the Raman cell, and a second retroreflector that forms one end of the Raman resonator. The output mirror forms an opposite end of the cell, and the dichroic mirror and the prism are disposed between the second retroreflector and the first lens.

Abstract: A laser having a glass enclosure placed in an optical cavity receives a pump beam and generates at least one first-order and one second-order Stokes wave. The construction is such that an optical waveguide placed in the gas enclosure is used to select the first and the second-order Stokes wave.

Abstract: A multi-mode Raman laser system wherein Raman conversion is performed by injecting exciting laser beam from transversely excited atmospheric pressure CO.sub.2 laser system into a Raman cell. Unstable resonator type oscillator is used as transversely excited atmospheric pressure CO.sub.2 laser system; and multi-mode Raman cell is used as the Raman cell. The quantity required for an excited CO.sub.2 laser system can thus be extensively reduced. Also, it is possible to reduce the input electric required for obtaining the same energy of 16 .mu.m light which is scattered light, because saturated conversion of excited light, can be achieved by multi-mode Raman cell, and system efficiency can be increased.

Abstract: A multi-wavelength surgical laser apparatus of improved construction employs a fluid-filled stimulated Raman scattering cell in an optical feedback path of a pump laser having a power in a range suitable for surgery, and drives the Raman cell at a high repetition rate in a manner to produce a laser output at a substantially shifted wavelength at a power commensurate with that of the pump laser. In a preferred system, the relative proportions of pump light and Raman scattered light are varied to achieve a desired cutting or coagulating action. Preferably, the pump laser is operated at a pulse repetition rate above five hundred Hz. The fluid Raman medium is pumped across the optical axis of the cell. The flow system effectively doubles the Raman conversion efficiency and permits high power output while lowering the Raman lasing threshold.

Abstract: A chromium doped solid-state high peak-power laser transmitter emits at a 4861.342 or 4340.50 Angstrom Fraunhofer line, lines of peak blue-seawater transmission and minimum solar radiation. A pink ruby gain medium doped with approximately 0.05% chromium ion is temperature tuned to an R2 line at 6924.51 Angstrom wavelength and an R1 line is dispersively suppressed in a laser oscillator cavity also tuned to 6924.51 Angstrom. The oscillator is Q-switched and the amplified high peak-power 6924.51 Angstrom R2 line output is frequency doubled to 3462.26 Angstrom and hydrogen Raman down-shifted 8310 cm.sup.-1 to the second-Stokes at 4861.342 Angstrom to produce said high peak-power output centered on the 4861.342 Angstrom hydrogen-beta Fraunhofer line. Optionally, a temperture tuned 6927.00 Angstrom R2 line laser oscillator wavelength from the pink ruby gain medium doped with approximately 0.05% chromium ion relies on frequency doubling the R2 line at 6927.00 Angstrom to 3462.

Abstract: A chromium doped solid-state high peak-power laser transmitter emits at a 4861.342 or 4340.5 Angstrom Fraunhofer line, lines of peak blue-seawater transmission and minimum solar radiation. A pink ruby gain medium doped with approximately 0.05% chromium ion is temperature tuned to an R2 line at 6924.51 Angstrom wavelength and an R1 line is dispersively suppressed in a laser oscillator cavity also tuned to 6924.51 Angstrom. The oscillator is Q-switched and the amplified high peaked-power 6924.51 Angstrom output is hydrogen Raman shifted to the first-Stokes at 9722.684 Angstrom which is frequency doubled to produce a high peak-power output at 4861.342 Angstrom hydrogen-beta Fraunhofer line. Optionally, a temperature tuned R2 line at 6927.00 Angstrom wavelength from the pink ruby gain medium doped with approximately 0.05% chromium ion is Raman shifted 2916 cm.sup.-1 in methane to the first-Stokes at 8681.0 Angstrom. Next, the first-Stokes at 8681.0 Angstrom is frequency doubled to the 4340.

Abstract: An infrared laser system includes a neodymium laser for generating a pulsed laser beam at a wavelength of 1.06 micrometers and a Raman cell containing a Raman active medium. The laser beam, having sufficient peak power to cause emission of light from the Raman active medium by stimulated Raman scattering, is directed through the Raman cell. Ethanol-d.sub.1 or methanol-d.sub.1 is used as the Raman active medium to generate wavelengths of about 2.8-2.9 micrometers. The laser is preferably a neodymium YAG laser.

Abstract: The present invention provides an apparatus and method for generating blue laser light having a wavelength corresponding to a solar Fraunhofer line. The blue laser light is at a frequency that has both excellent transmissibility through sea water and a high signal-to-noise ratio. A first laser beam, generated using an injection-locked excimer XeCl laser, is down-converted by a first-Stokes order shift of 2.times.4155 cm.sup.-1 in a first Raman cell containing H.sub.2 gas at a pressure of about 10 atmospheres. The output of the first Raman cell is down-converted by a first Stokes shift of 3628 cm.sup.-1 in a second Raman cell containing HD at a pressure of about 10 atmospheres so that the output of the second Raman cell has a wavelength of 486.366 nm. This wavelength corresponds to the FE I solar Fraunhofer line.

Abstract: This specification discloses an integrated type optical node comprising a substrate, a channel light waveguide formed on the substrate for connecting the transmission lines of an optical information system, an amplifying portion provided on the light waveguide for amplifying a light propagated through the waveguide, and a light branching-off portion provided on the light waveguide for coupling a light transmitter and/or a light receiver to the transmission lines. The specification also discloses an optical information system using such optical node.

Abstract: Disclosed is a laser source with beam scanning, of the type comprising: a pump laser source emitting a pump beam with a determined wavelength; a pressurized gas cell receiving the pump beam and emitting, by Raman effect, an output beam with a wavelength called a Stokes wavelength; a control light source transmitting a control beam to the gas cell, this control beam having a wavelength that is substantially equal to the Stokes wavelength; wherein said light source includes means for the spatial and/or temperal modification of the injection of the control photons of the control beam into said cell constituted by a multiple-laser strip structure, forming a power slave laser and cooperating with means for modifying the radiation pattern of said multiple-laser strip structure, so as to prompt the emission of the output beam in a variable direction.

Abstract: A Raman laser apparatus for producing a high energy output beam with low divergence. An optical pump beam (14) propagates through first and second focuses (34,36) inside a cell containing a gaseous Raman medium (20) at a pressure selected to promote stimulated Raman scattering (SRS) and suppress stimulated Brillouin scattering (SBS). The pump beam (14) generates a backward SRS wave at the second focus (36), which propagates back through the first focus (34) and acts as a seed for backward SRS therein. The backward SRS wave is amplified at the first focus (34), and extracted therefrom as an output beam (38) by output means (40). Any forward SRS wave which is generated at either the first focus (34) or the second focus (36) may be reflected back through the second focus (36) and then through the first focus (34) to further increase the backward SRS seed beam at the first focus. The output beam (38) is retro-reflected, and has beam divergence comparable to the pump beam divergence.

Abstract: A tunable laser source comprising a laser source emitting a pump beam towards a Raman cell. It transmits a beam at a Stokes wavelength to a non-linear crystal. Depending on the angle of this beam with the optical axis of the crystal, the non-linear crystal transmits two output waves at wavelengths that are different from the Stokes wavelength.

Abstract: Disclosed is a laser pulse generator in which a single pulse is generated from a train of pulses. The amplitude of this single pulse is the addition of the amplitudes of the pulses of the train of pulses. This addition is done in a non-linear crystal inserted in an optical loop. The train of pulses takes the place of a pump wave applied to the non-linear crystal and the signal circulating in the optical loop takes the place of a signal wave. This signal wave therefore benefits from a transfer of energy coming from the pump wave because of the interaction in the non-linear crystal.

Abstract: A two-cell Raman converter for generating a relatively large number of Stokes shifted waves from an input laser pump beam. A first lens focuses the pump beam into the first cell, whose output is recollimated and focused by second and third lenses into the second cell. The second cell output is recollimated by a recollimating lens to provide the final output. Each Raman cell employs stimuated rotational Raman scattering and Raman media at low pressures optimized to achieve maximum conversion into Stokes lines.

Abstract: The invention relates to a Raman converter of improved design, which does not require an exact alignment of the optical elements. There is provided is backward Raman converter which comprises a Raman medium which converts a laser radiation of a given wavelength to a different wavelength by Raman scattering, which comprises a dichroic coupler positioned between a pump laser at the one side of the Raman medium, directing the laser beam into the Raman medium, reflective means being positioned on the second side of the Raman medium, which reflects the Raman-shifted radiation back into the Raman medium, wherein the radiation is amplified by the interaction with the Raman medium and with the incoming pump laser beam. The amplified Raman shifted beam is coupled out of the system by means of the dichroic coupler.

Abstract: A methane Raman cell is provided with a catalytic composite comprising palladium on a titania substrate, which promotes the hydrogenation of gas products formed by the decomposition of methane from arcing, and thereby inhibits the reaction of these gas products to form deposits which adhere to the windows of the Raman cell. This Raman cell has greatly increased life. In an alternative embodiment, further improvements may be obtained by adding hydrogen dopant gas to the methane.

Abstract: This invention relates to deflection cells for laser beams. A deflection cell according to the present invention essentially comprises a deflector such as of the "acoustooptical" type, to deflect a low-power incident laser beam, and a system to make that deflected low-power incident beam, in a nonlinear Brillouin diffusion medium 11 like a gas such as methane (CH.sub.4), xenon, sulfur hexafluoride (SF.sub.6), or a liquid such as carbon disulfide (CS.sub.2), acetone, work with a high-power laser pump beam, forming a nonzero angle ".theta." with the deflected beam. Application, in particular, to telemetry and missile guidance for which the laser beam used as reference should be able to undergo orientation changes which are quick and in a large angular field.

Abstract: This invention relates to power laser generators in which it is possible to control the angular direction of output laser beams. The generator according to the present invention is characterized by the fact that it successively comprises on the same optical axis of propagation, a pilot laser beam generator to generate a laser beam wavelength, a controllable deflector, a beam separator, a laser amplifying medium with the wavelength of the pilot beam, and a phase conjugation nonlinear mirror. The laser generator is applicable, in particular, to missile guidance systems or in telemetry systems.

Abstract: A method of converting the laser radiation of a pump laser into another wavelength range by stimulated Raman scattering in which the laser radiation of the pump laser is conducted through a Raman medium, thus generating Stokes radiation in the other wavelength range, and an arrangement for implementing the method. The laser radiation from the pump laser leaving the Raman medium and the generating Stokes radiation are fed together to an amplifier for the laser radiation of the pump laser, and the thus amplified laser radiation of the pump laser is conducted together with the accompanying Stokes radiation through a further Raman medium for conversion of the amplified laser radiation of the pump laser into Stokes radiation.

Abstract: Raman cell beam combining apparatus for combining a seed beam with a pump beam being introduced into the Raman cell, and employing a segmented mirror for substantially correcting the relative tilt of individual incremental portions of the wavefront of the pump beam with respect to the wavefront of the seed beam, and such mirror having an array of flat non-coplanar wavefront shifting elements positioned parallel with respect to each other.

Abstract: A cell for holding a fluid medium for passing a beam of laser radiation through it to generate Raman shifted radiation is provided with a vaned agitator designed to effect flow of the fluid within the cell across the beam path, so that there is continually provided a fresh column of the optical medium within the beam path.

Abstract: A tapered optical fiber amplifier is designed to provide for long-distance, un-repeatered fiber optic communications. Two single-mode fiber portions are tapered to efficiently intensify and couple an information signal from a laser diode and a pump signal at a shorter wavelength into a fused, tapered single-mode fiber optic coupler. The concentrated information signal and concentrated pump signal are combined via the coupler which is coupled to a several-kilometer length of a relatively small core diametered single-mode fiber to create a nonlinear optical effect (stimulated Raman scattering) (SRS). The SRS causes Raman shift of the pump signal to amplify the information signal, resulting in amplified signals that are efficiently coupled out of the relatively small core diametered optical fiber with another single-mode optical fiber taper portion.

Abstract: A cavity which is resonant at a laser pumping frequency is defined by a reflective surface (92) and a mirror (110). A Raman medium (106) is contained within the cavity, as is a laser (90). A Q-switch (94), when not spoiling the Q of the cavity, allows photon density to increase within the cavity. When the Raman threshold of the Raman medium is exceeded, the Raman medium absorbs and then radiates photons. The radiated photons are at longer wavelength than the laser photons, and also occur in very short (less than ten nanoseconds) pulses. The radiated photons are reflected by a mirror (101) and exit the cavity through one of the reflectors defining the cavity (mirror 110). The invention shifts the wavelength and shortens the pulse duration of pulses produced by the laser (90).

Abstract: This invention relates to increasing the power output of a broadband Raman amplifier by angle-tuned phase matching of either multiple individual pump lines or a continuous spectra in a pump beam 1 relative to their corresponding Stokes lines or Stokes spectra in the Stokes seed beam 2 so that energy can transfer from the pump lines to the Stokes lines more efficiently. The invention can work in any solid or fluid Raman medium. The Raman cell could be in a length of optical fiber using the internal reflections in the optical fibers as mirrors 8. By using angle tuning, enhancement of the Raman gain is produced which allows the Raman amplifier to achieve high power output with much larger pump bandwidths than were previously possible. The input pump beam 1 is fanned by diffraction grating 3 so that the pump lines are at the proper angle to be phase matched with the Stokes seed beam 2 which may also be fanned.

Abstract: Applicant has discovered a correlation between photography, the laser mechanism, and SERS. It appears that all three effects or phenomena of photography, laser and SERS, originate from a similar mechanism, namely the amplifying factor comes from Einstein coefficients and subsequent description of inverse population--these being the essential building blocks for the aforementioned three phenomena. Accordingly, one aspect of the invention is to utilize the principles of photography in connection with SERS. Another aspect is to utilize the principles of photography in connection with lasers. A still further object is to employ all three fields to achieve the lasing and laser effects described in greater detail below.

Abstract: A lasing medium (3) and a Raman medium (20) share a common optical cavity. The lasing medium (3) projects laser light into the Raman medium (20) and, when a threshold intensity within the Raman medium is reached, the Raman medium absorbs the laser light and re-radiates coherent light at a shifted frequency. Optical elements within the system provide an optical cavity for the lasing medium and a second cavity for the Raman medium.

Abstract: Normal stimulated Raman scattering (SRS) is done in a gas cell with pump and Stokes seed input beams. The pump photons excite gas molecules in the gas cell from their ground state and the Stokes seed photons stimulate the de-excitation of the molecules back to a lower state (emitting more Stokes photons in the process). The SRS enhancer entails inputting another beam at a frequency, different from the pump and seed, tuned between a third molecular state and the Raman virtual state created by the pump/seed off-resonant two-photon transition. The third laser enhances the Raman virtual state, thereby also enhancing the two-photon transition rate. Since the two-photon transition is the SRS process, the Stokes amplification is enhanced.

Abstract: A miniaturized Q-switch is added to the resonant cavity of a compact laser diode pumped solid state laser to produce short high peak power pulses which are input into a single mode optical fiber to form a compact continuum generator. Q-switching the compact laser diode pumped solid state lasers takes advantage of the relatively high gain and short cavity length to provide a desirable combination of pulsewidth and pulse energy. Nd:YAG or Nd:YLF are useful solid state laser materials for Q-switching, or other longer lifetime rare earth ions such as erbium or holmium for greater energy storage. The Q-switch is formed of a material such as TeO.sub.2, SF.sub.10, or LiNbO.sub.3 with an acoustooptic figure of merit substantially greater tha fused silica. The high peak powers of the lasers are sufficient to exceed the threshold for Raman conversion in the fiber which produces a series of red shifted bands ending in a continuum by stimulated Raman scattering.

Abstract: Device for providing a train of light pulses at Raman shifted frequency comprises a first ring laser (for fundamental frequency) and a second ring laser (for Raman shifted frequency). Both ring laser intersect in a Raman laser medium which is common to the cavity of both ring lasers. The Raman cavity has output means partially transmissive at Raman frequency. Length of first and second ring laser cavities differs by .DELTA.L. Injection of a fundamental pump pulse and a small Raman seed pulse into their respective cavities results in output of a train of Stokes pulses.

Abstract: A Raman laser (10) is provided using a pump laser (22) as a source of radiation at a first wavelength and a Raman cell (30) for converting the first wavelength radiation to a second wavelength. The pump laser (20) provides polarized radiation at a predetermined first wavelength which is focused by a focusing means (40) into a Raman medium (32) which converts radiation at the first wavelength to a predetermined second wavelength by Raman scattering processes. A reflection means (50) which is aligned normal to the first wavelength radiation is disposed between the pump laser (20) and focusing means (40). The reflection means is substantially 100% reflective of radiation at the second wavelength and substantially non-reflective of radiation at the first wavelength.

Abstract: An all-fiber ring laser has a single, uninterrupted length of single-mode optical fiber that is formed into a loop by using an optical coupler. Pump signal pulses at a first optical wavelength are introduced into one end of the optical fiber. Each pump pulse propagates through the loop formed in the fiber and then exits the fiber. The pump signal pulses excite the molecules of the optical fiber to cause them to go to a higher, unstable energy level. When the molecules return to a lower energy level, photons are emitted at a second optical frequency that has a wavelength that is shifted from the wavelength of the pump signal to form laser signal pulses. The coupler is a multiplexing coupler that has a first coupling ratio at the wavelength of the pump signal and has a second coupling ratio at the wavelength of the emitted optical signal. The first coupling ratio is preferably close to zero and the second coupling coefficient is greater than 0.5.

Abstract: A laser system utilizing a Stimulated Brillouin Scattering SBS cell to produce optical phase conjugate retroreflection for nonmonochromatic light from a laser system.

Abstract: A method and apparatus for generating relatively narrow linewidth radiation, for example having a 1 MHz linewidth. The apparatus comprises a source of relatively broad linewidth, coherent radiation such as a semiconductor laser (1) generating optical radiation having a linewidth of 10 MHz. The broad linewidth radiation is injected into a waveguide ring (5), the characteristics of the radiation and the form of the waveguide ring (5) being such that stimulated Brillouin scattering occurs in use to generate the relatively narrow linewidth of the order of kHz, coherent wave travelling in an opposite direction to the broad linewidth radiation. A directional coupler (3) between the source (1) and the waveguide ring (5) separates the narrow linewidth wave from the injected radiation.

Abstract: A filter tap for optical communication systems includes an optical resonant cavity comprising generally parallel, facing dielectric mirrors spaced to permit resonance in a selected band of channels. Optical signals from an input portion of a main trunk line carrying optical signals on a plurality of bands are coupled to one of the mirrors at an end face of the resonant cavity and are coupled from the one mirror to an output portion of the main trunk line with minimal reduction in optical signals in nonselected bands. Optical signals in the selected band are coupled from the other of the mirrors on the other end face of the resonant cavity to a branch line. In one preferred embodiment, the cavity is a finer optic resonant cavity and trunk line optical fibers are coupled directly to one of the mirrors of the cavity. Power is coupled from the input portion to the output portion of the trunk line by evanescent coupling.

Abstract: A laser system having a gaseous Raman cell incorporate methane (CH.sub.4) as the Raman scattering medium. The cell includes gaseous hydrogen to prevent deposition of carbonaceous material from decomposed methane on the windows of the Raman cell.

Abstract: An optical signal pulse to be amplified and a pump signal pulse are launched consecutively into one end of an optical fiber, which may comprise a separate fibre or part of a transmission line. The pulses differ in wavelength by one or more Stokes shift and the order of launch is determined by the relative group velocities in the fibre. Owing to dispersion in the fibre the pulses overlap and overtake one another while they are transmitted along the fibre, the signal pulse being amplified as a result of Raman stimulated emission and compressed as a result of power depletion from the pump pulse, thus increasing the bandwidth of the transmission line.

Abstract: A device utilizing lasers wherein efficient wavelength shifting of the generated laser radiation is provided using stimulated Raman scattering both in atomic vapor and molecular media. A coupled pair of confocal unstable resonators in conjuction with an integral injection laser is utilized in a novel optical arrangement for providing the efficient conversion of laser power into Stokes radiation without beam obscurations. The wavelength, spectral bandwidth, polarization and beam divergence are controlled by the spatial evolution of the main laser output which is locked to the seed radiation provided along the optical axis by the injection laser. Mode matching of the wavefront is automatically achieved by the use of common optical surfaces which couple the injection laser, main laser and the Raman converter. The resulting Stokes output through a partially reflecting/transmitting mirror is an unobscured beam whose intensity profile is determined by the laser medium power distribution.

Abstract: A dispersion compensation delay line is added to a synchronously pumped fiber Raman ring oscillator to generate subpicosecond pulses. A pair of spaced gratings form the delay line. An interference filter is used as a bandwidth limiting tuning element to provide a good quality short pulse. An integrated design eliminates the discrete optical elements by using only an optical fiber and an optical fiber coupler.

Abstract: A portion of the pulsed output of a 3-mirror, folded, astigmatically compensated cavity of a c.w., mode-locked, color center laser is coupled into a single-mode, polarization-preserving optical fiber. Following compression of the pulses by their propagation through the fiber, the shortened pulses, which take the form of essentially solitons, are fed back into the laser cavity so as to coincide and be in phase with the pulses in the laser cavity. Through the process of stimulated emission in the color center crystal, the injected pulses force the laser itself to produce shorter pulses of essentially the same shape as the solitons. Also described are embodiments employing a mode-locked semiconductor, fiber-Raman laser, and unidirectional pulse propagation in the fiber. Two of the fiber-Raman laser embodiments have separate gain and pulse shaping sections of optical fiber joined by an optical fiber directional coupler.

Abstract: A system for linearly amplifying an optical analog signal by backward stimulated Raman scattering comprises a laser source for generating a pump pulse; and an optic fiber having two opposed apertures, a first aperture for receiving the pump pulse and a second aperture for receiving the optical analog signal, wherein the optical analog signal is linearly amplified to an amplified optical analog signal.

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.