Thomas B Johnston

US Patent:

41503422, Apr 17, 1979

Filed:

Jul 5, 1977

Appl. No.:

5/812698

Inventors:

Thomas F. Johnston - Sunnyvale CA
James L. Hobart - Los Altos Hills CA
Robert C. Rempel - Los Altos CA
Gerald H. Williams - Sunnyvale CA

Assignee:

Coherent, Inc. - Palo Alto CA

International Classification:

H01S 310

US Classification:

331 945S

Abstract:

Method and apparatus are disclosed in a frequency controlled tunable laser system which may be tuned selectively by an operator to any predetermined output radiation frequency within its operating range and servo-locked to maintain that output frequency, for rapidly and automatically maintaining and reacquiring a predetermined output radiation frequency despite momentary interruptions or perturbations of laser oscillation.

US Patent:

42721580, Jun 9, 1981

Filed:

Mar 2, 1979

Appl. No.:

6/016687

Inventors:

Thomas F. Johnston - Sunnyvale CA
William P. Proffitt - San Jose CA

Assignee:

Coherent, Inc. - Palo Alto CA

International Classification:

G02F 109
G01B 902

US Classification:

350375

Abstract:

A broadband optical diode consists of a Faraday element within a magnetic field and an optically active element. The materials and dimensions of the Faraday element and the optically active element are chosen so that their polarization rotations approximately match over a broad wavelength span, with the rotation angles and the mismatch between them specified by the conditions that the forward wave insertion loss does not exceed a maximum specified value, and the differential loss between forward and backward traveling waves is not less than a minimum specified value.

US Patent:

42688000, May 19, 1981

Filed:

Apr 30, 1979

Appl. No.:

6/034511

Inventors:

Thomas F. Johnston - Sunnyvale CA
William P. Proffitt - San Jose CA

Assignee:

Coherent, Inc. - Palo Alto CA

International Classification:

H01S 308

US Classification:

331 945C

Abstract:

A tipping Brewster plate, used for fine tuning a tunable ring laser, such as a dye laser, is located close to a flat mirror comprising one of the optical elements of the ring optical resonator, so that both the incident and reflected beam from the flat mirror pass through the tipping Brewster plate. When the ring laser is tuned by tipping the Brewster plate, no lateral displacement of the ring laser beam takes place.

US Patent:

48645788, Sep 5, 1989

Filed:

Mar 16, 1987

Appl. No.:

7/026068

Inventors:

William P. Proffitt - Cupertino CA
Gerald H. Williams - Sunnyvale CA
James L. Hobart - Los Altos Hills CA
Thomas F. Johnston - Sunnyvale CA

Assignee:

Coherent, Inc. - Palo Alto CA

International Classification:

H01S 310

US Classification:

372 20

Abstract:

A scannable dye laser is provided with an integral wavemeter under computer control. The wavemeter has improved fine and coarse readout components. Incremental laser scans are precisely linked together to provide long, continuous frequency scans. The fine readout of the wavemeter provides a means for accurately piecing together the incremental scans.

US Patent:

45148490, Apr 30, 1985

Filed:

Sep 7, 1983

Appl. No.:

6/529979

Inventors:

Kenneth G. Witte - Mountain View CA
Thomas F. Johnston - Sunnyvale CA

Assignee:

Coherent, Inc. - Palo Alto CA

International Classification:

H01S 313

US Classification:

372 29

Abstract:

A laser-pumped laser system is disclosed, such as a dye laser which is optically pumped by an argon ion laser. An improved servo system is provided for maintaining relative alignment of the pump laser beam with respect to the dye laser cavity. This is accomplished by rotating the pump beam such that the beam defines a conical surface, by means such as an optically-transmissive rotating wedge. Such rotation provides dithering along two orthogonal axes, which provides the necessary control information to maintain pump beam alignment.

US Patent:

52144852, May 25, 1993

Filed:

Jan 24, 1992

Appl. No.:

7/825512

Inventors:

Michael W. Sasnett - Los Altos CA
Thomas F. Johnston - Sunnyvale CA

Assignee:

Coherent, Inc. - Palo Alto CA

International Classification:

G01J 100

US Classification:

356121

Abstract:

A method and apparatus for determining the quality of a multimode laser beam (10). In the preferred embodiment, the apparatus includes a lens (32) for creating a transformed or imaged waist from the input beam. The location of the transformed beam waist and its diameter are then determined. These steps can be carried out by chopping the beam using a rotating hub (34) having apertures (36,38) for selectively passing the beam. Preferably, one of the apertures has a pair of 45. degree. knife edges (40,42). The transmission of the beam past the knife edge is monitored by a detector (30). In operation, the lens focal position is varied while the transmission of the beam past the knife edge is monitored in order to locate and measure the diameter of the transformed waist. The diameter of the beam at one other known location is measured. A processor then calculates beam quality by fitting these measurements to a mathematical model.

US Patent:

52670120, Nov 30, 1993

Filed:

Feb 5, 1993

Appl. No.:

8/014424

Inventors:

Michael W. Sasnett - Los Altos CA
Thomas F. Johnston - Sunnyvale CA

Assignee:

Coherent, Inc. - Palo Alto CA

International Classification:

G01J 100

US Classification:

356121

Abstract:

A method and apparatus for determining the quality of a multimode laser beam (10). In the preferred embodiment, the apparatus includes a lens (32) for creating a transformed or imaged waist from the input beam. The location of the transformed beam waist and its diameter are then determined. These steps can be carried out by chopping the beam using a rotating hub (34) having apertures (36,38) for selectively passing the beam. Preferably, one of the apertures has a pair of 45. degree. knife edges 40,42). The transmission of the beam past the knife edge is monitored by a detector (30). In operation, the lens focal position is varied while the transmission of the beam past the knife edge is monitored in order to locate and measure the diameter of the transformed waist. The diameter of the beam at one other known location is measured. A processor then calculates beam quality by fitting these measurements to a mathematical model.

US Patent:

53586980, Oct 25, 1994

Filed:

Feb 26, 1991

Appl. No.:

7/661359

Inventors:

James R. Butler - Houston TX
Thomas W. Johnston - Houston TX

Assignee:

Fina Technology, Inc. - Dallas TX

International Classification:

B01J 802

US Classification:

422218

Abstract:

A catalyst-bed radial gas-flow reactor system is disclosed utilizing a generally cylindrical catalyst bed located in an annualar area between an outer reactor shell and a generally coaxially located displacement member; wherein the gas flow through the reactor is optimized to extend catalyst life by including a non-cylindrical section in at least a portion of the displacement cylinder, and the gas-supply duct entering the reactor shell has baffling arranged to equalize flow velocities across the reactor diameter.