Donald R Dewhirst

US Patent:

50900161, Feb 18, 1992

Filed:

Feb 15, 1991

Appl. No.:

7/655614

Inventors:

Donald R. Dewhirst - Torrance CA
Robert D. Stultz - Huntington Beach CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

H01S 330

US Classification:

372 3

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. The two focal points (34 and 36) may be in the same or separate Raman cells (16, or 16' and 18).

US Patent:

46602046, Apr 21, 1987

Filed:

Aug 2, 1984

Appl. No.:

6/637097

Inventors:

Donald R. Dewhirst - Torrance CA
Robert L. Duvall - Torrance CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

H01S 3125

US Classification:

372 16

Abstract:

A CO. sub. 2 TEA laser utilizing an intra-cavity rotating prism Q-switch (70) for angularly switching the resonator gain by periodically causing the resonator mirrors (54, 56) to be in alignment. An opto-electronic timing device (79), which includes a graded index glass rod (76) rotating with the Q-switch prism, generates a pulse to initiate the laser discharge at the proper time before the mirrors are aligned so that the laser output pulse occurs when peak gain is achieved. The Q-switch speed of rotation is chosen such that the time interval in which the mirrors are aligned is not long enough to support the tail portion of the pulse typical of the gain switched CO. sub. 2 TEA laser.

US Patent:

48212725, Apr 11, 1989

Filed:

Oct 31, 1986

Appl. No.:

6/924108

Inventors:

Hans W. Bruesselbach - Santa Monica CA
Donald R. Dewhirst - Torrance CA

Assignee:

Hughes Aircraft Co. - Los Angeles CA

International Classification:

H01S 330

US Classification:

372 3

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. A polarizing means (70) and quarter-wave plate (60) are disposed along the optical path between the Raman medium (32) and the pump laser (20) for allowing propagation of the first wavelength to the Raman medium (32) but preventing SBS radiation from entering the pump laser (20) from the Raman medium. Alternatively, the pump laser includes an output reflection means (124) that is substantially 100% reflective of radiation at the second wavelength and partially reflective of radiation at the first wavelength.

US Patent:

51516268, Sep 29, 1992

Filed:

Feb 19, 1991

Appl. No.:

7/657280

Inventors:

Donald R. Dewhirst - Torrance CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

H01L 4108

US Classification:

310331

Abstract:

In a Raman cell (10) which is subject to optical distortion of the path of a laser beam (40) by heating of the gas from the Raman conversion process, vibrating blades (50) cause the gas to mix and thus provide thermal homogeneity within the beam path.

US Patent:

48092827, Feb 28, 1989

Filed:

Nov 2, 1987

Appl. No.:

7/125801

Inventors:

Donald R. Dewhirst - Torrance CA

Assignee:

Hughes Aircraft Co. - Los Angeles CA

International Classification:

H01S 311

US Classification:

372 16

Abstract:

A CO. sub. 2 TEA laser Q-switch uses an intra cavity rotating prism (70) with internally reflecting surfaces (76, 78) at near the critical angle to produce a variable optical loss such that the gain of the laser is switched as the prism rotates through the critical angle. The nitrogen tail portion of the laser output pulse can be eliminated by switching the gain just after the main pulse at the beginning at the tail. An opto-electronic timing device (100), which includes a graded index glass rod (101) rotating with the Q-switch prism, generates a pulse (88) to initiate the laser discharge at the proper lead time before the prism switches the resonator gain.

US Patent:

50480421, Sep 10, 1991

Filed:

Nov 19, 1990

Appl. No.:

7/615118

Inventors:

Thomas P. Moser - Redondo Beach CA
Donald R. Dewhirst - Torrance CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

H01S 322

US Classification:

372 59

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.

US Patent:

46564330, Apr 7, 1987

Filed:

Aug 19, 1982

Appl. No.:

6/409477

Inventors:

James D. Franklin - Los Angeles CA
Donald R. Dewhirst - Torrance CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

H01S 311
H01S 300

US Classification:

330 43

Abstract:

A laser amplifier buffer arrangement for selectively switching laser energy in a double pass laser amplifier. The buffer arrangement comprises a wedge of birefringent material which angularly separates incident laser energy into polarized components, and an electro-optic polarization switch which may be selectively controlled to circularly polarize the polarization components of light passing therethrough. A plane mirror is employed to reflect the polarized components back through the switch and wedge. The wedge and switch are aligned in a manner such that an arbitrarily polarized input beam is separated into two orthogonally polarizated components that traverse separate paths through the buffer. The polarized components are reflected back through the switch and wedge by the mirror which is aligned with the normal bisecting the polarization component separation angle. When the switch voltage is off, both polarization components are misaligned with the incident beam energy when transmitted by the buffer, therefore preventing the laser amplifier from superradiant lasing.

US Patent:

39597407, May 25, 1976

Filed:

Feb 6, 1975

Appl. No.:

5/547663

Inventors:

Donald R. Dewhirst - Torrance CA

Assignee:

The United States of America as represented by the Secretary of the Air
Force - Washington DC

International Classification:

H01S 311

US Classification:

331 945Q

Abstract:

A configuration of a pair of crystalline quartz wedges utilized as polarizers is combined with an electro optic switch to constitute a laser Q-switch. The two wedges are identical and are positioned on either side of the switch and oriented such that one compensates the angular deviation and dispersion of the other.