Trw Limited

Northrop Grumman Systems Corporation

Hagop Injeyan

Randall J St Pierre

Carolyn S Hoefer

Stephen P Palese

James G Ho

Gerald W Holleman

Jacqueline G Berg

Robert R Rice

George M Harpole

Eric C Cheung

Rodger C Hilyard

Hiroshi Komine

Lee O Heflinger

Lawrence J Lembo

Stephen John Brosnan

James M Zamel

Charles W Clendening, Jr

Mark Ernest Weber

William W Simmons

Terry Lee Holcomb

Leonard J Marabella

Larry G DeShazer

Marcy M Valley

Steven P Palese

One embodiment of the present method and apparatus encompasses an apparatus that may have: a predetermined length, the self-imaging semiconductor waveguide having first and second opposed sides; quantum wells disposed within the self-imaging semiconductor waveguide along the length of the self-imaging semiconductor waveguide, the quantum wells being formed of a quantum well gain material; microchannel cooler that extends substantially the width of the self-imaging semiconductor waveguide, the microchannel cooler located adjacent the first side of the self-imaging semiconductor waveguide; and a plurality of pump arrays arranged along the microchannel cooler opposed from the first side of the self-imaging semiconductor waveguide; wherein the quantum well gain material is photopumped through the microchannel cooler.

Scalable semiconductor waveguide amplifier

An electrically controlled variable reflectance mirror that includes a Pockels cell which enables its retardation or birefringence to be controlled in order to vary the light outcoupled from a laser cavity. Since the retardation is a function of the voltage applied to the Pockels cell, the voltage can be used to control the fraction of the output beam that is outcoupled from the laser cavity. The Pockels cell is formed with a constant reflectivity profile to form an electrically controlled uniform reflectivity electro-optic mirror. In an alternate embodiment of the invention, the Pockels cell is configured with spatially varying retardation to form an electrically controlled graded reflectivity electro-optic mirror. Both embodiments of the invention enable a lasing system, such as a solid state lasing system, to be operated over a relatively wide range of operating parameters utilizing a single set of optics.

Electrically controlled uniform or graded reflectivity electro-optic mirror

A method is provided for seeding laser system () for single longitudinal mode oscillation. The method includes coupling laser system () to be seeded for single mode output to a seed laser radiation source (). Next, the frequency capture range () and spacing () of the axial modes () of the cavity () of the laser system () are determined. A seed spectrum () is then generated from the seed laser radiation source () with a bandwidth () corresponding to the axial mode spacing (). The seed spectrum () includes a comb of discrete frequency components () with one or more of the discrete frequency components () being within the frequency capture range () of at least one of the axial modes (). The seed spectrum () is then injected into the cavity () such that at least one of the axial modes () oscillates with the seed radiation.

Robust seeding technique for single mode laser oscillation

An optical amplifier (,) includes an elongated slab (,) of solid state lapsing material, such as a rare earth doped yttrium-aluminum-garnet (YAG) slab. In order to provide a relatively increased absorption length and thus a higher overall efficiency, the optical amplifier (,) in accordance with the present invention incorporates end pumping in which the pumped light is coaligned with the amplified light resulting in relatively longer absorption lengths and higher overall efficiencies. The coaligned pumped sources are directed to lateral faces of the slab (,) which include footprints (,) or windows. In order to cause internal reflection of the pump beam along the lapsing axis, the end faces (,) are formed at about a 45&deg; angle relative to the longitudinal axis which causes the pumped light to be reflected within the slab co-axially with amplified light. In order to confine the absorption of the pumped light to the center portion of the slab (,), the slab (,) may be formed from a composite material with the opposing end portions of the slab formed from an undoped host material while the center portion of the slab along the longitudinal axis is formed from a doped host material. Such a configuration provides relatively low residual thermal lensing with virtually no birefringence. In one embodiment, the pumping light from the diode arrays is coupled to the slab (,) by way of lenses (,) or lens ducts (FIG.,). In an alternate embodiment, the pumping light is coupled to the slab (,) by way of optical fibers (,). In yet another embodiment (FIG.,), the pumping light and laser beams are interchanged forming a low-loss straight through slab with end pumped architecture.

End pumped zig-zag slab laser gain medium

An optical amplifier which includes an elongated slab of solid state lasing material, such as a rare earth doped yttrium-aluminum-garnet (YAG). In order to provide a relatively increased absorption length and thus a higher overall efficiency, the optical amplifier in accordance with the present invention incorporates end pumping in which the pumped light is coaligned with the amplified light resulting in relatively longer absorption lengths and higher overall efficiencies. The coaligned pumped sources are directed to lateral faces of the slab which include windows, formed from an insulating coating such as an anti-reflection coating, at the pump wavelength. In order to cause internal reflection of the pump beam along the lasing axis, the end faces are formed at about a 45&deg; angle relative to the longitudinal axis which causes the pumped light to be reflected within the slab co-axially a with a amplified light. In order to confine the absorption of the pumped light to the center portion of the slab, the opposing end portions of the slab may be undoped while the center portion of the slab along the longitudinal axis is doped. Such a configuration provides relatively low residual thermal lensing with virtually no birefringence.

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

An optical amplifier which includes an elongated slab of solid state lasing material, such as a rare earth doped yttrium-aluminum-garnet (YAG). In order to provide a relatively increased absorption length and thus a higher overall efficiency, the optical amplifier in accordance with the present invention incorporates end pumping in which the pumped light is coaligned with the amplified light resulting in relatively longer absorption lengths and higher overall efficiencies. The coaligned pumped sources are directed to lateral faces of the slab which include windows, formed from an insulating coating such as an anti-reflection coating, at the pump wavelength. In order to cause internal reflection of the pump beam along the lasing axis, the end faces are formed at about a 45.degree. angle relative to the longitudinal axis which causes the pumped light to be reflected within the slab co-axially with a amplified light. In order to confine the absorption of the pumped light to the center portion of the slab, the opposing end portions of the slab may be undoped while the center portion of the slab along the longitudinal axis is doped. Such a configuration provides relatively low residual thermal lensing with virtually no birefringence.

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 solid state saturable absorber (SSSA) is formed from a slab of solid state material, such as Cr.sup.4+ : YAG. Optical distortion caused by the absorption process can be minimized by confining absorption to portions of the solid state slab which can be cooled efficiently. In accordance with an important aspect of the invention, the use of the SSSA in accordance with the present invention allows the repetition rate, pulse width, and energy level of the laser output pulses to be controlled by way of optical pump sources, such as a diode array. The solid state slab material allows for zig-zag propagation and thus, averaging of the thermal gradients caused by absorption, optical pumping and cooling which results in relatively low thermal lensing with virtually no birefringence and therefore allows for passive Q-switching applications in relatively high brightness laser systems. In an alternate embodiment of the invention, a plurality of thin cells are stacked and immersed in an indexed matched cooling fluid in order to increase the absorption length while minimizing optical distortion.

Optically controllable cooled saturable absorber Q-switch slab

The present invention provides a solid state laser gain medium 28 comprising: (a) a gain layer 30 having pump regions 32 and first and second contact regions 34 and 36, respectively; (b) a first transparent layer 38 optically connected to the first contact region 34 of the gain layer 30 by diffusion bonding; and (c) a second transparent layer 40 optically connected to the second contact region 36 of the gain layer 30 by diffusion bonding. The transparent layers 38 and 40 are transparent to the lasing wavelength of the gain medium 28. The present invention also provides an apparatus for amplifying laser light, comprising: (a) a solid state, slab geometry gain medium 44 having lateral pump faces 46 and a principal radiation absorption axis C; and (b) an excitation mechanism 48 located along the pump faces 46 of the gain medium 44 for generating polarized light along a polarization axis 52 wherein the polarization axis 52 is parallel with the principal absorption axis C of the gain medium 44 to provide increased radiation absorption. The present invention also provides a cooling system 58 for a solid state gain medium 60 generating laser output laser emission at a wavelength from about 2 .mu.m to about 3 .mu.m. The cooling system 58 including a coolant material such as D2O for reducing absorption of laser emissions by the coolant at wavelengths from about 2 .mu.m to about 3 .mu.m.

Three-level laser system

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 high efficiency solid state Raman laser system for shifting the frequency of an input beam emitted by a laser pumping system is described. The laser pumping system suppresses relaxation oscillations in the input beam and emits a constant power, mode-locked pulse train. A solid Raman medium is disposed inside a Raman resonator cavity to shift the frequency of the input beam to produce a Raman beam. The frequency of the Raman beam is finely tuned in the resonator cavity to eliminate high order Raman shifted wavelengths. The polarization of the Raman beam is selected using a polarizing element disposed in the resonator cavity. The Raman beam frequency is shifted using a non-linear medium inside the resonator cavity. The non-linear medium is preferably a frequency doubler. The Raman laser system is particularly suitable for producing high-quality yellow light for guide star applications.

High efficiency solid state raman laser system

A technique for operating a diode pumped solid state laser in a continuous-wave (cw) mode using diodes blocks (12) that are individually operated in a pulsed mode. For some high power laser applications, it is desirable to provide for operation in pulsed and cw modes, but pump diodes are typically designed for efficient operation in only one of these modes. The invention includes a controller (20) that pulses the individual diode blocks (12) on and off, but not necessarily in unison. For a pulsed mode of operation, the diodes (12) in an array are pulsed either at the same time, or sub-arrays are pulsed in a temporally interleaved manner for a higher effective pulse repetition rate. For the cw mode of operation, the diodes (12) are pulsed sequentially in sub-arrays (A-E), such that at least one sub-array is always energized and the complete array appears to be providing continuous pumping energy. In one embodiment, the sub-arrays (A-E) are columns of the array. In another embodiment, the sub-arrays (12') are each associated with a different solid-state gain medium (10'), the gain media being optically coupled in a single laser.

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Glendale, CA, United States of America

Hagop Injeyan