Hughes Aircraft Company

The Perkin-Elmer Corporation

Raytheon Company

Steven H Macomber

Jeffrey S Mott

Peter J De Groot

Gregg M Gallatin

Andrew H Montroll

Patricia A Lee

Surface-emitting distributed feedback (SEDFB) lasers having a curved grating with a shape that produces good beam quality. A preferred shape is one for which the grating curves away from the center of the gain region of the laser. The use of the curved grating of the present invention produces good beam quality from broad area SEDFB lasers with high power and high efficiency. The present invention overcomes self-induced filament formation and dynamic instabilities that limit achievable beam quality. The present invention provides for a holographic method for fabricating curved gratings for the SEDFB lasers that is consistent with laser batch processing.

Curved grating surface-emitting distributed feedback laser

An array (10) of diode lasers (12) is comprised of a substrate (22) having a plurality of electrically conductive surface areas (24, 24a, 24b, 24c) and a plurality of diode laser subassemblies (20) individual ones of which are conductively coupled to one of the plurality of surface areas (24a). Each of the diode laser subassemblies includes a diode laser (12), preferably a SE-DFB diode laser, that is conductively coupled to and mounted upon a first surface of an electrically conductive body or submount (14). The submount has a second opposite surface that is electrically coupled to and mounted upon one of the electrically conductive areas, preferably with a layer (25) of compliant, deformable material such as indium foil or an indium alloy. The individual diode lasers are preferably electrically connected in a series, voltage adding configuration. The substrate further includes a plurality of electrical conductors for connecting to individual ones of the diode lasers such that a current flow can be established through a single diode laser. This facilitates the alignment process, and also enables individual diode lasers to be selectively energized. For each of the subassemblies there is provided at least one electrically conductive clamping member (26, 28, 30) for compressively urging the submount towards the substrate and for also coupling a current flow to the diode laser. A predetermined number of the subassemblies are arranged in a linear pattern on the substrate, and a lens (34) is disposed relative to the diode lasers in the linear pattern for collimating an output beam from individual ones of the diode lasers. A cylindrical lens is a presently preferred embodiment for the collimating lens.

Voltage adding diode laser array

A surface-emitting distributed Talbot filter laser that provides for radiation of energy in in-phase radiating modes to produce improved beam quality. The distributed Talbot filter laser of the present invention comprises a plurality of sets of parallel stripe contacts, wherein adjacent parallel sets of parallel stripe contacts are offset from each other. The laser may optionally employ a phase corrector for reducing sidelobe energy. In addition, the plurality of stripe contacts may each have a relatively large stripe width to increase a near-field fill factor of the laser and thereby reduce sidelobe energy. The gain profile of the laser is patterned using the offset stripe contact design, such that the stripe pattern matches the intensity profile of the preferred in-phase mode. The stripe pattern is comprised of offset parallel arrays of stripes spaced apart by a distance D and having length nD.sup.2 /.lambda., wherein n is the effective index of refraction and .lambda. is the wavelength of the laser radiation in a vacuum. The in-phase radiating mode has a central far-field lobe located on-axis, resulting in a higher radiance laser.

Distributed talbot filter surface-emitting distributed feedback laser

An improved broad area surface emitting distributed feedback semiconductor laser diode device (10) includes a P-side ohmic contact (28) and an N-side ohmic contact (36). A potential difference is applied across these contacts to create an electric field that induces a stimulated emission of coherent photon radiation. The coherent photon radiation produced by the stimulated emission process is incident upon a second order grating having a curved pattern incorporated therein (29). An output beam, directed normal to a chemically etched output window (38), is produced by a first order diffraction of photon radiation from the surface of the second order curved grating (29). The output beam has a more uniform lateral mode near-field output intensity profile and a more uniform lateral mode near-field phase. The output beam also has a desired single-lobed lateral mode far-field output intensity profile. Moreover, the device (10) concentrates approximately 1 Watt of power into this single lateral mode far-field lobe.

Curved grating surface emitting distributed feedback semiconductor laser

An apparatus 10 for exposing a curved grating pattern of monochromatic light on a photoresist coated semiconductor wafer 12 includes an argon gas laser 14 that outputs a monochromatic light beam 16. This monochromatic light beam 16 is filtered and collimated to produce a monochromatic light beam with a planar wavefront 24. A portion of this planar wavefront passes through a cylindrical lens array 26 and a first baffle slit 30, producing multiple cylindrical wavefront 34 that is incident upon a hypotenuse face 38 of a right angle prism 40. Another portion of the planar wavefront passes through a second baffle slit 32, producing a smaller planar wavefront 36 that is also incident upon the hypotenuse face 38 of the right angle prism 40. A destructive interference between a reflected multiple cylindrical wavefront 92 and a direct planar wavefront 90 inside the prism 40 produces a curved grating pattern of monochromatic light on an adjacent prism face 42. This curved grating pattern of monochromatic light is projected toward the semiconductor wafer 12, thereby exposing the photoresist coated wafer surface 48 with the curved grating pattern.

Apparatus and method for fabricating a curved grating in a surface

A Talbot filtered surface emitting distributed feedback semiconductor laser array (12) includes two surface emitting distributed feedback semiconductor laser device subarrays (20, 22) that are separated by a free propagation region (24) having a length equal to a Talbot distance, z.sub.T. Within each subarray (20, 22) there is a like number of surface emitting distributed feedback semiconductor laser device elements (18) that are laterally isolated from each other by optical absorbing material stripes (26) to prevent evanescent coupling. A Talbot spatial filter array (28) of optical absorbing material islands (34) is fabricated in the free propagation region (24) at one half the Talbot distance. The Talbot spatial filter array (28) establishes fundamental lateral mode oscillation in the array (12), thereby producing a high quality laser beam with a predominantly single lobed far-field.

Talbot filtered surface emitting distributed feedback semiconductor

A chirped grating surface emitting distributed feedback semiconductor laser device (10) includes a P-side ohmic contact (28) and an N-side ohmic contact (36). A potential difference is applied across these contacts to create an electric field that induces a stimulated emission of coherent photon radiation. The coherent photon radiation produced by the stimulated emission process is incident upon a linearly varying, second order chirped grating surface (29). An output beam, directed normal to a chemically etched output window (38), is produced by a first order diffraction of photon radiation from the chirped grating surface (29). The output beam has a non-uniform longitudinal mode near-field output intensity profile and a non-abrupt longitudinal mode near-field phase, both due to a reduced destructive interference interaction in a second order diffraction of photon radiation along the grating surface (29). The output beam also has a desired single lobed longitudinal mode far-field output intensity profile. Moreover, the device achieves a 20% power efficiency due to the reduced destructive interference in the second order diffraction.

Chirped grating surface emitting distributed feedback semiconductor laser

An apparatus 10 for exposing a chirped grating pattern of monochromatic light on a photoresist coated semiconductor wafer 12 includes an argon gas laser 14 that outputs a monochromatic light beam 16. This monochromatic light beam 16 is filtered and collimated to produce a monochromatic light beam with a planar wavefront 24. A portion of this planar wavefront passes through a cylindrical lens 26 and a first baffle slit 30, producing a cylindrical wavefront 34 that is incident upon a hypotenuse face 38 of a right angle prism 40. Another portion of the planar wavefront passes through a second baffle slit 32, producing a smaller planar wavefront 36 that is also incident upon the hypotenuse face 38 of the right angle prism 40. A destructive interference between a reflected cylindrical wavefront 92 and a direct planar wavefront 90 inside the prism 40 produces a chirped grating pattern of monochromatic light on an adjacent prism face 42. This chirped grating pattern of monochromatic light is projected toward the semiconductor wafer 12, thereby exposing the photoresist coated wafer surface 48 with the chirped grating pattern.

Apparatus and method for fabricating a chirped grating in a surface

An optical radar system for coherent ranging and velocimetry. Modulation of a laser diode by light backscattered from a target is used to determine distance and velocity of a target. An array of laser diodes are used to determine the velocity and topography of a target. Three laser diodes are used to determine speed and orientation of a rotating disk.

Position and velocity imaging system using 2-D laser diode array

An integrated semiconductor source of high-power, single spatial mode, narrow spectral mode modulated radiation. A frequency selective feedback laser diode is disposed on the same semiconductor crystal with a power amplifier having a diverging active area which causes emitted light to be distributed over a large exit facet area.

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Bethel, CT, United States of America

Steven H Macomber