Xerox Corporation

Spectra Diode Laboratories, Inc.

William Streifer

Donald R Scifres

Robert D Burnham

David F Welch

Peter Cross

Thomas L Paoli

Robert G Waarts

G A Connell

John G Endriz

Howard M Stark

Robert N Goren

Gary L Harnagel

Fernando A Ponce

Neville Connell

Lawrence Morton Marks

Jerome R Klein

Hsing Kung

Dan H Fekete

A method using implantation to form a semiconductor laser or laser array with current blocking implants. A semiconductor material laser structure including layers of a first conductivity type, an active region and layers of a second conductivity type is formed. In a first embodiment, impurity ions of the second conductivity type are implanted into selected regions of a first conductivity type layer. The implanted ions form current blocking buried regions of the second conductivity type with current confining channels therebetween. Finally, the structure is thermally annealed. In a second embodiment, a disorder inducing impurity, which may be a saturable absorber, is diffused into selected portions of the layers of the first conductivity type through the active region. The diffusion converts side regions of those layers into the second conductivity type. Impurity ions of the first conductivity type are implanted to a uniform depth crossing through the side regions to form a buried region of the first conductivity type. Current is confined to the center undiffused region. Last, the structure is thermally annealed. A laser array with individually addressable conductive contacts is also described. Ion bombardment is used to create insulative surface regions to isolate adjacent contacts from one another.

Method of forming current barriers in semiconductor lasers

A diode laser external lens cavity configuration having a stripe mirror with two thin parallel stripes placed in front of the two lobes of the arrays for far field output pattern. The configuration includes a diode laser array or broad area laser, a lens system, such as a graded-index lens, disposed in front of the laser's front light emitting facet and the stripe mirror disposed in front of the lens system at the focal plane of the lens. The two stripes are parallel to one another on opposite sides of and equidistant from a vertical reference plane through the lens' center axis. One stripe is highly reflective, while the other is effectively only partially reflective having either a lower stripe reflectivity or shorter length than the first stripe. Other embodiments include a third stripe spaced from and collinear with the second stripe to form an etalon, and a grating in the cavity.

Diode laser with external lens cavity

GaAs/AlGaAs heterostructure lasers containing indium in at least one layer other than or in addition to the active region. Embodiments are described in which indium added in low concentration to the cladding functions to match the lattice constants between the cladding and active layers, in which indium is added in high concentration to form strain layers that prevent defect migration therethrough and if proximate to the active region decrease transparency current and increase differential gain, in which indium is added uniformly to all layers to suppress defect formation, and in which indium is added to a cap layer to reduce metallization contact resistance.

GaAs/AlGaAs heterostructure laser containing indium

A diode laser of the type having an array of laser emitters in a Talbot cavity in which edge reflectors are added to enhance feedback to edgemost emitters. In one embodiment, a transparent slab with reflectively coated sides is present between the phase plane of the emitted light and the Talbot cavity reflector. The phase plne is defined by a lenticular array placed a focal length in front of the laser emitters. In another embodiment, the Talbot cavity reflector has an increased reflectivity toward its edges. In all embodiments the Talbot cavity reflector is preferably spaced a distance na.sup.2 /.lambda. from the phase plane, where n is a positive integer, a is separation between adjacent emitters and .lambda. is the wavelength of emitted light. An integrated embodiment has the array and cavity reflectors defined ina single semiconductor body divided into active and ransparent region. Side mirrors are etched into the semiconductor body. The laser array may also be extended to two dimensions with individual lasers or laser bars fiber coupled to a lens surface, with an edge reflector and Talbot cavity reflector coated on an otherwise transparent slab.

Talbot cavity diode laser with uniform single-mode output

A method of making semiconductor laser arrays having an impurity disordered pattern of waveguides at least some of which are directly joined at branching junctions. The region near the branching junctions provides a phase boundary condition in which lightwaves propagating in adjacent waveguides are in phase. Using one impurity dose and one disordering depth in a first portion of the pattern and another in a second portion of the pattern provides a combination of strong and weak waveguiding with strong waveguides that eliminate evanescent coupling from occurring at least in the branching junction regions, and with weak guides near one or both end facets permitting evanescent coupling. The evanescent coupling between adjacent weak waveguides preserves the in phase relationship that was established in the Y-junction regions, resulting in a diffraction limited single lobe far field output. Alternatively, even without evanescent coupling, the modes can adjust their phases in the weak waveguides, where the propagation constant is less tightly specified by the geometry.

Method of forming a semiconductor laser

A pyrotechnic ignition method in which a semiconductor laser bar or bars containing a number of independent laser array sources deliver optical power in a specified sequence through optical fibers to a set of pyrotechnic elements in order to initiate a sequence of pyrotechnic events, such as a fireworks display, building demolition, emergency ejection sequence, satellite launch, etc. A command signal is transmitted and received, typically by a remote station from the user. The signal is decoded to generate a set of electrical signals representing addresses of individual laser arrays on the laser bar. The laser arrays are activated in the desired sequence in response to the set of electrical signals and emit laser light. This light is transmitted along optical fibers coupled to the individual laser arrays and terminating in pyrotechnic elements. The pyrotechnic elements are ignited in response to optical power received from the optical fibers, typically by direct heating of a detonator. The detonator may also be ignited photochemically or by electric current produced by a photoelectric sensor in response to sensing of the laser light.

Method of initiating a sequence of pyrotechnic events

A laser in which the central portion is provided with current pumping means consisting of an array of current confining stripe contacts to provide a multiple emitter active layer and the end sections of the laser are provided with transparent waveguides. The active layer of this laser can be abruptly stepped along the direction of light propagation, or provided with tapered end couplers, or in any other way made transparent, so that light escapes from the emitters of the active layer of the central portion of the laser into the transparent waveguides at the ends of the laser. The transparent waveguides are of a non-absorbing material of higher bandgap than the central active layer material, or of the same material but otherwise rendered transparent, so that the escaping light strikes the mirror facets and is reflected back, whereby a portion of the reflected light couples back into its emitter and provides the optical feedback for laser operation. Phase-locking is achieved because when the light from each emitter under each pumped stripe region emerges into the transparent waveguides, there is less or no lateral waveguiding, and therefore the light from each emitter diverges. Because of this divergence, when this light strikes the mirror facets, portions of the light from each emitter are reflected back into other adjacent emitters, thus phase-locking the laser output and making it highly collimated. Relative to conventional multi-emitter lasers, five to ten times higher output powers from the collimated beam are obtained, such increase in power occurring because the material at the laser mirror surface is transparent to the active region radiation and therefore is not damaged by the very intense light.

Phased-locked window lasers

A plurality of diode lasers is focussed onto a single region by arranging the diodes at equally spaced locations on a first arc. Each diode laser emits light in a slit-like pattern which is characterized by orthogonal axes. In a first group of cylindrical lenses, one associated with each diode laser, each lens has a refractive surface having an axis parallel to one of the emitting axes of the laser and refracts light to a focal region of defined dimensions. Each cylindrical lens is disposed along a second arc having a circular center common with the first arc. A second group of cylindrical lenses, one associated with each laser, is also disposed on a circular arc, concentric with the other arcs, but the second group has a refractive axis perpendicular to the first refractive axis. The second group of cylindrical lenses acts upon the second axis of the source image, focussing it to the common focal region. The first and second cylindrical lens groups may be combined into a toric surface within a single lens. The cylindrical lenses may either be individual lenses, or may be combined into a lenticular array. The lenses may be simple cylindrical refractive lenses, Fresnel lenses, or holographic lenses. A bright image of the source is formed at the common focal region. The diode lasers and cylindrical lenses may be arranged in three dimensions to produce very high optical power densities.

Diode laser arrangement forming bright image

Lasers and laser arrays having various optical elements, such as lenses, apertures, prisms, etalons and phase plates, integrated within the resonant optical cavity of the laser. The optical elements are created by introducing a lateral geometric contour in boundaries of refractive index changes thereby causing a change in shape of phase fronts of lightwaves propagating in the laser cavity in a manner analogous to optical elements. Boundaries may be defined between an active region and transparent window regions or may be formed in other layers with which lightwaves interact, such as the layers bounding the active region. Curved boundaries produce convergent or divergent lenses. Absorbing regions may bound window regions to produce apertures for lateral mode control. A periodic step shaped boundary can be used to shift the phase of lightwaves propagating in some laser array waveguides relative to lightwaves in others of the waveguides in order to cause beam emission of a desired supermode. Fresnel lenses, prisms and etalons can also be integrated within the laser.

Semiconductor laser with integrated optical elements

A semiconductor laser array having a plurality of waveguides at least some of which are directly joined at Y-junctions. The region near the Y-junctions provides a phase boundary condition in which lightwaves propagating in adjacent waveguides are in phase. A combination of strong and weak waveguiding is provided, with strong waveguides that eliminate evanescent coupling from occuring at least in the Y-junction regions, and with weak guides near one or both end facets permitting evanescent coupling. The evanescent coupling between adjacent weak waveguides preserves the in phase relationship that was established in the Y-junction regions, resulting in a diffraction limited single lobe far field output. Alternatively, even without evanescent coupling, the modes can adjust their phases in the weak waveguides, where the propagation constant is less tightly specified by the geometry.

Hybrid Y-junction laser array

A diode laser bar producing a linear array of laser beams without lateral superradiance. The laser bar has a double-heterostructure or quantum well structure. Etched channels in the substrate create lateral corrugations in the subsequently deposited layers including the active region. The corrugations alternate between offset groove and plateau regions in the lateral direction but are straight in the longitudinal light propagating direction. Any laterally propagating light is interrupted at steps, between groove and plateau regions, by deflection, scattering or transmission out of the active region. Interruption may also be achieved with a plurality of parallel etched grooves extending in the longitudinal direction. The grooves which cut through the active region present a semiconductor-air interface for reflection and/or scattering of laterally propagating light out of the active region. Proton bombarded regions may be provided above the step regions in the top layers to channel current and prevent optical burnout of the step regions. A small percentage of laser light may be allowed to laterally propagate into adjacent active regions to promote phase locking across the laser bar.

Lateral superradiance suppressing diode laser bar

A split contact phased array laser comprising a plurality of parallel emitters under phase locked operation and productive of an output beam having a preferred emission wavelength and preferred far field mode of operation. The charge distribution profile in the laser is changed to cause the output beam to deflect and scan in the far field. The improvement in the laser is the provision of at least three independently current pumped segments formed transversely of said emitters wherein at least one of the segments is current pumped above threshold level sufficient to primarily determine the emission wavelength and mode of operation of the laser while the current supplied to the remaining segments is below this level and is varied relative to one another to cause the output beam to deflect and scan in the far field without substantial change to the emission wavelength and mode of operation. This is because the charge density is essentially clamped under the one dominant contact segment and is only minimally influenced by further changes in the pumping current.

Split contact phased array lasers

A phased array semiconductor laser favoring emission in the 1st or Nth supermode over other potential supermodes of the laser comprising a plurality of spatially disposed laser elements formed relative to an active region to provide optical cavities for light wave generation and propagation under lasing conditions and wherein the optical field of laser elements are coupled into the optical cavities of adjacent laser elements to provide a phase locked condition across the array. The position of the outer laser element at each end of the array are spaced closer to adjacent laser element compared to the spacing provided between all the other of laser elements such that the coupling across the array is enhanced to produce at least one supermode with a nearly uniform and fairly rectangular shaped intensity envelope. The optimized optical coupling coefficient between the outer lasing elements and their adjacent laser elements is .sqroot.2 K, where K is the optical coupling coefficient between the other laser elements. The optical coupling coefficient of .sqroot.2 K between these outer lasing elements, however, may be within the range of 80% to 120% of .sqroot.2 K. The phase of some of the laser elements in the array may be reversed 180.degree..

Phased array semiconductor lasers with uniform and stable supermode

A semiconductor laser array having a plurality of sets of interconnecting waveguides, each joining two optical waveguides together at respective branching junctions. The array has a plurality of semiconductor layers disposed on a substrate, at least one of the layers forming an active region for light wave generation and propagation under lasing conditions. One or more structures, such as current confining channels, a channelled substrate and variable thickness active region define a plurality of adjacent optical emitting waveguides. The waveguides are coupled together in a coupling geometry which ensures that breaks or failures in one or more branches are bypassed, thereby maintaining in-phase laser array operation.

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Palo Alto, CA, United States of America

William Streifer