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: Disclosed is a method and apparatus for reducing or eliminating the speckle intensity distribution of an imaging and/or tracking system The benefits of utilizing a highly coherent source (12) as an imaging and tracking system are well known. However, such a coherent source (12) provides a speckle intensity distribution which reduces the effective resolution capability of the imaging system. This invention takes a coherent beam of light (14) and impinges it into a Raman cell (16) to obtain a broad spectral bandwidth beam of light having additional side wavelengths other than the original wavelength. In addition, this invention provides a means to improve the beam quality of all of the Raman lines. Therefore, a composite beam having broad spectral bandwidth composed of individual spectral lines having good beam quality is generated. As a result of the broad spectral bandwidth, images formed from targets illuminated by such a composite beam are substantially free of speckle intensity variations.

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: An optical blue parametric generation relies upon a nonlinear optical cryl of lithium borate (LiB.sub.3 O.sub.5) properly oriented to generate blue light when appropriately located in a resonant optical cavity and pumped with high intensity light at 355 nm. Beam walk-off and beam pump divergence are greatly reduced due to a specific orientation of non-critical phase-matching so that the 355 nm pump source provides for a sufficient phase-match for output generation near the H Beta Fraunhofer wavelength at 486 nm and also provides for a temperature tuning of the lithium borate crystal to permit exact coincidence to a particular output wavelength so that optical parametric generation from 470 to 487 nm may be assured by the appropriately tuned lithium borate crystal.

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: First and second relatively high power laser beams are directed into a volume enclosing a flow field of molecules of a molecular species. The beams are focussed to form an overlapping region of the beams in the flow field, for tagging a portion of the associated molecules by driving them into their first vibrational state by stimulated Raman pumping. A high intensity beam of light is directed into the flow field proximate the overlap region for intercepting the tagged molecules, and causing them to fluoresce, thereby permitting their displacement to be measured through observation thereof, for determining the velocity of the associated molecules and flow field.

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 converter comprising an input optical pump beam (16) from a laser (18) that propagates through first and second Raman cells (12,24) and causes Stokes shifted waves (14,26) to be generated therein, and a polarizer (34) disposed between the Raman cells (12,24). The polarizer (34) is switchable during laser operation to cause the Stokes shifted waves (14) from the first Raman cell (12) to be circularly or linearly polarized, thereby causing the Stokes shifted waves (26) in the second Raman cell to be generated as rotationally shifted or vibrationally shifted waves respectively. The polarizer (34) may be switched to the selected circular or linear polarization, or may be repeatedly switched therebetween at regular or pseudo-random intervals. A second polarizer (32) may be disposed upstream of the first Raman cell (12) for selectively switching the polarization of the input pump beam (16) during laser operation. The polarizers (32) and (34) may each be used alone or in combination with each other.

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 laser diode produces a laser beam having a carrier frequency component and a sideband frequency component. An optical resonator receives the laser beam and substantially couples the carrier frequency component and substantially rejects the sideband frequency component. An electronic locking system receives the rejected sideband frequency component and adjusts the laser diode to lock the carrier frequency component to the resonator frequency. A laser control controls the allocation of power between the carrier frequency and the sideband frequency component such that the resonator output may be controlled and pulsed.

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: 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.