Coherent, Inc.

Thomas F Johnston, Jr

Michael W Sasnett

Gerald H Williams

William P Proffitt

James L Hobart

David A Dewey

Dennis G Fischer

Nubar Sahag Manoukian

Bruce E Perilloux

Robert C Rempel

Arnold L Bloom

Kenneth G Witte

Larry Giammona

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. Once the quality of the beam is calculated, the location of the original beam waist and its diameter can be derived. Once all of the beam parameters are derived, the propagation characteristics of the beam can be predicted.

Apparatus for measuring the mode quality of a laser beam

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. Once the quality of the beam is calculated, the location of the original beam waist and its diameter can be derived. Once all of the beam parameters are derived, the propagation characteristics of the beam can be predicted.

A laser 10 is disclosed in which there are incorporated one or more diffractive optical elements (DOE's) 20. The DOE's can be used in place of conventional optics to save costs and allow design of resonators not heretofore possible. The ability to vary the reflectivity of the surface of a DOE in any desired pattern allows unprecedented control of both the intracavity mode as well as the mode of the output beam.

Laser resonators employing diffractive optical elements

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. Once the quality of the beam is calculated, the location of the original beam waist and its diameter can be derived. Once all of the beam parameters are derived, the propagation characteristics of the beam can be predicted. In one embodiment of the subject invention, the device includes a blocking member (602) having a knife edge (604) disposed perpendicularly to one of the knife edges of the apertures carried on the hub. The blocking member is translated in discrete steps for each revolution of the hub. The measurement of the power transmitted past the knife edge and blocking member can be used to generate a two-dimensional pixel map of beam intensity.

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 seletively passing the beam. Preferably, one of the appertures 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. Once the quality of the beam is calculated, the location of the original beam waist and its diameter can be derived. Once all of the beam parameters are derived, the propagation characteristics of the beam can be predicted. In the preferred embodiment, the lens is defined by a doublet (533, 535) designed to minimize spherical aberration. In addition, the spacing between the lens pair is varied to minimize the net aberration at the operating wavelength of the laser.

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 (14) 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. Once the quality of the beam is calculated, the location of the original beam waist and its diameter can be derived. Once all of the beam parameters are derived, the propagation characteristics of the beam can be predicted. In the preferred embodiment, the transformed beam waist is located by taking incremental measurements of beam diameter, at both the front and rear planes of the hub, as the lens is moved a distance at least a great as the diameter of the hub. The diameter measurements are spliced together by the processor to provide an axial profile of the beam over a distance twice as large as the diameter of hub. This data can then be analyzed to find the minimum which corresponds to the location of the transformed beam waist.

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.

Scannable laser with integral wavemeter

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.

Dye laser with rotating wedge alignment servo

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.

Broadband optical diode for a ring laser

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.

Vertex-mounted tipping Brewster plate for a ring laser

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.

Method and apparatus for automatically reacquiring a predetermined

An adjustable etalon mode selector is mounted within the optical cavity of a laser and includes a pair of spaced prisms mounted along the optical axis of the cavity with the laser beam passing therethrough and means for selectively adjusting the spacing between the prisms in a manner such that the resonant frequency of the laser cavity and etalon combination remains constant during the adjustment of the prism spacing in order that a particular mode of the operating wavelength spectrum of the laser may be selected for output, without the adjustment modulating the cavity natural resonant frequency.

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Auburn, CA, United States of America

Thomas F Johnston, Jr