Trw Limited

Randall J St Pierre

Hagop Injeyan

George M Harpole

Carolyn S Hoefer

Rodger C Hilyard

Stephen P Palese

Lee O Heflinger

Lawrence J Lembo

James M Zamel

Mark Ernest Weber

William W Simmons

Larry G DeShazer

Marcy M Valley

David W Mordaunt

An optical amplifier for use with a solid state laser which includes a pair of elongated slabs of a solid state lasing material, such as a rare earth doped yttrium-aluminum-garnet (YAG) crystal. Two embodiments of the invention are disclosed. In both embodiments of the invention, each of the elongated slabs is formed with a square or generally rectangular cross-section. The slabs are configured such that the longitudinal axes of the slabs are generally co-axial aligned and the slabs are orientated such that the major axis of the slabs are generally orthogonal. By configuring the two slabs to be orthogonal with respect to one another, the integrated thermal lens becomes azimuthally symmetric and can be compensated by a simple external lens. In addition, the negative lensing affect along the major axis of one slab is used to compensate for the positive lensing affect along the minor axis of the other slab and vice versa, thus minimizing the affects of the astigmatism. In an alternate embodiment of the invention, a dove prism is used to rotate the beam instead of rotation of the slabs.

Laser with two orthogonal zig-zag slab gain media for optical phase distortion compensation

A system and method for monitoring the mode of an input beam to a phase conjugated master oscillator power amplifier (PC MOPA). In order to prevent catastrophic optical damage to the MOPA components, the method and system shuts down the master oscillator when a multi-mode input beam is detected.

Phase conjugated master oscillator-power amplifier breakdown control

A method of controlling the thermal optical path difference (OPD) in a lasing medium in a solid state laser during pumping of a lasing medium 10 including a pair of side faces 12 for receiving radiation during pumping and a pair of edge faces 16, comprises the steps of determining a temperature difference, .DELTA.T.sub.min, between the side faces and the edge faces that corresponds with approximately a minimum, OPD.sub.min, in the OPD, and maintaining about .DELTA.T.sub.min during pumping of the lasing medium, such that the OPD is maintained at approximately OPD.sub.min. The temperature difference is maintained by controlling heat transfer at the edge faces of the lasing medium. The temperature difference between the edge faces and the side faces can be actively controlled such that the method can be automated.

Optical path difference control system and method for solid state lasers

There is provided an optically pumped laser apparatus 10 which includes a heat conductive assembly 14 which is affixed to a solidstate yag laser crystal medium for generating a laser beam 49 within the laser crystal medium 12. The heat conductive assembly 14 comprises a heat diffusing element 32 which serves to diffuse the heat that is generated through the cooling surfaces 24 and 26. It includes a heat discharging structure 33 for removing the heat from the system. The efficiency of the laser system is improved by the geometry of pumping the crystal laser medium along the paths shown by the arrow 40 and to directing heat removed by the heat conductive assembly along the arrows 42, which paths are normal to one another and which provide an effective geometry that minimizes temperature variations within the laser crystal 12 to provide a low value for the OPD of the system. The heat conductive assembly 14 may include a liquid type heat exchanger 43, or heat pipes 33 to facilitate removal of the heat from the diffuser 32.

Passive conductively cooled laser crystal medium

A high power laser source having a preselected broad bandwidth, including a master oscillator providing a single-mode laser beam, a resonant electro-optical modulator and a source of radio-frequency (rf) modulation voltage, to produce a modulator output beam having sidebands spaced on each side of the nominal frequency of the single-mode laser beam. The bandwidth and the number of modes may be varied by controlling the voltage applied to the modulator. At least one additional modulator in series with the first provides for the addition of other sidebands overlaying those generated with just one modulator. In another embodiment of the invention, the modulator is installed in a PC MOPA (phase conjugated master oscillator power amplifier) configuration to provide modulation only on the return path of the beam from a phase conjugation device having a stimulated Brillouin scattering (SBS) medium. Because the electro-optical modulator is sensitive to polarization direction, it can be oriented to be effective only for the return beam, which has a different direction of polarization from that of the single-mode laser beam, thus optimizing the performance of the SBS medium.

Variable coherence length high brightness laser architecture

A device for producing phase conjugation of electromagnetic radiation using stimulated Brillouin scattering (SBS), comprising an SBS cell having a liquid perfluorocarbon as an SBS medium. The liquid perfluorocarbon is selected from the group of compounds having the formula C.sub.x F.sub.y, wherein x&gt;1 and y&gt;4. Preferably, x&gt;4 and y&lt;16, and most preferably, 4&lt;x&lt;7 and 6&lt;y&lt;15. Also, a solid state laser comprising the device. Also, a method for reducing the aberrations in a laser beam, such as aberrations created when the beam passes through an amplifying medium comprising the step of generating phase conjugation by SBS using a liquid perfluorocarbon as an SBS medium. Further, a method of producing an output laser beam comprising the steps of, generating an initial laser beam using a laser and phase conjugating the initial laser beam by SBS using a liquid perfluorocarbon medium as an SBS medium. The liquid perfluorocarbon is selected from the group of compounds having the formula C.sub.x F.sub.y, wherein x&gt;1 and y&gt;4. Preferably, x&gt;4 and y&lt;16, and most preferably, 4&lt;x&lt;7 and 6&lt;y&lt;15.

Ozone compatible stimulated brillouin scattering materials

A solid-state laser architecture producing a beam of extremely high quality and brightness, including a master oscillator operating in conjunction with a zig-zag amplifier, an image relaying telescope and a phase conjugation cell. One embodiment of the laser architecture compensates for birefringence that is thermally induced in the amplifier, but injects linearly polarized light into the phase conjugation cell. Another embodiment injects circularly polarized light into the phase conjugation cell and includes optical components that eliminate birefringence effects arising in a first pass through the amplifier. Optional features permit the use of a frequency doubler assembly to provide output at twice optical frequencies, and an electro-optical switch or Faraday rotator to effect polarization angle rotation if the amplifier material can only be operated at one polarization. The zig-zag amplifier is cooled by flow of cooling liquid, preferably using longitudinal flow to minimize temperature gradients in a vertical direction, and has cooling channel seals disposed in dead zones that receive no light, to minimize optical damage to the seals. Light is input to the amplifier at a near normal angle of incidence, to minimize polarization by reflection and to permit a polarizer to be used to extract an output beam from the amplifier. Antireflective coatings on edges and on sides of the amplifier eliminate parasitic oscillations, and wedge-shaped windows provide uniform pumping by eliminating gaps between diode arrays.

Solid-state zig-zag slab optical amplifier

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. The combination of the quarter-wave plate and the Faraday rotator provides better birefringence cancellation than either element acting alone.

Birefringence compensated laser architecture

High brightness solid-state laser with zig-zag amplifier

Apparatus and a related method for generating a second harmonic frequency optical output from a fundamental frequency input beam, without significant birefringence. The apparatus includes two Type II doubler crystals of equal length arranged with their corresponding axes parallel to each other, and a polarization rotator positioned between the doubler crystals, to rotate the polarization angle of a residual fundamental frequency component of an output beam from one of the crystals by 90.degree. or an odd multiple of 90.degree.. Random birefringence introduced into one of the doubler crystals is virtually canceled in the other, and the assembly of the two crystals and the polarization rotator may be angularly adjusted as needed for phase matching or tuning, without detracting from the birefringence compensation capability. The invention is also disclosed in the context of a phase conjugated master oscillator power amplifier (PC MOPA) system.

Birefringence-compensated alignment-insensitive frequency doubler

A highly-efficient solid-state blue laser that exploits a strong emission line provided by a solid-state laser medium of neodymium-doped scandium oxide (Nd:Sc.sub.2 O.sub.3) to produce a beam of coherent blue light at a wavelength matching the absorption line of cesium at 455.6 nm (0.4556 microns). The solid-state blue laser includes the laser medium of neodymium-doped scandium oxide, a semiconductor diode laser array for optically pumping the laser medium to produce a beam of coherent infrared radiation at a wavelength of approximately 1367 nm (1.367 microns), and optical means for tripling the frequency of the beam of coherent infrared radiation to produce a beam of coherent blue light at the wavelength of approximately 455.6 nm. The solid-state blue laser is simple, highly efficient and provides relatively high power outputs.

Growing community of inventors

Santa Monica, CA, United States of America

Randall J St Pierre