L. West

Mid-wave infrared diode lasers based on GaInSb/InAs and InAs/AlSb superlattices

We report the characterization of a set of broad‐area semiconductor diode lasers with mid‐wave infrared (3–5 μm) emission wavelengths. The active region of each laser structure is a 5‐ or 6‐period multiple quantum well (MQW) with Ga0.75In0.25As0.22Sb0.78 barriers and type‐II (broken‐gap) Ga0.75In0.25Sb/InAs superlattice wells. The cladding layers of each laser structure are n‐ and p‐type InAs/AlSb (24 A /24 A) superlattices grown lattice‐matched to a GaSb substrate. By tailoring constituent layer thicknesses in the Ga0.75In0.25Sb/InAs superlattice wells, laser emission wavelengths ranging from 3.28 μm (maximum operating temperature=170 K) to 3.90 μm (maximum operating temperature=84 K) are obtained.

Spectroscopic and photorefractive properties of molybdenum‐doped barium titanate

Molybdenum‐doped barium titanate crystals have been grown and characterized. Electron paramagnetic resonance spectroscopy has confirmed the presence of Mo5+ centers in reduced crystals that correlate with a strong optical absorption band at ∼600 nm. Self‐pumped phase‐conjugation and electro‐optic beam‐coupling measurements indicate that the reduced crystals are photorefractive in the visible, as well as the near‐infrared wavelength region.

Optical control of microwaves with semiconductor n‐i‐p‐i structures

We control the microwave transmission of a GaAs n‐i‐p‐i structure by illuminating it with a cw argon ion laser. Tests in a broadband microwave modulator wave spectrometer show that an optical intensity of 800 mW/cm2 produces a 50% change in transmission for microwaves between 10 and 50 GHz.

3 to 5-um lasers employing GaInSb/InAs superlattice active layers

We demonstrate midwave infrared diode lasers than span the 3 - 4 micrometers range. Laser active regions are multiple quantum well structures with GaInSb/InAs, type-II, broken gap superlattices for the wells and GaInAsSb for the barriers. The superlattice constituents and dimensions were tailored to reduce losses from Auger recombination. AlSb/InAs superlattices are used for both n-type and p-type laser cladding regions. A device with emission at 3.2 micrometers lased up to 255 K. We have achieved 75 mW per facet at 3.0 micrometers at an operating temperature of 140 K with an 85 microsecond(s) ec input current pulse. Device output appears to be limited by resistive heating. A four-layer, strain-balanced superlattice design offers greater laser efficiency.

GaInSb/InAs superlattice-based infrared lasers

Mid-wave infrared lasers have been fabricated employing InAs/A1Sb superlattice cladding layers and multi-quantum well active regions consisting of Ga75In025Sb1InAs broken-gap superlattice wells and Ga75In025As023Sb,,77 barriers. Diodes demonstrated to date include lasers with emission wavelengths of 3.18j.tm at 255K, 3.40im at 195K, and 4.32p.m at 110K. Keywords: infrared, laser, diode, superlattice, multi-quantum well

MWIR lasers employing GaInSb/InAs broken-gap superlattice active regions and superlattice cladding layers

Substantial progress has been made recently in the development of room temperature MWIR semiconductor lasers. InAs/GaInSb broken-gap superlattices (BGSLs) are attractive candidates for MWIR laser active regions because they possess sufficient degrees of freedom to tailor the valence band structure while keeping the strain low enough to prevent the formation of misfit dislocations. The valence band structure can be optimized to suppress Auger recombination as well as other non-radiative recombination, thereby reducing laser threshold and increasing the maximum operating temperature. Here we report improved MWIR MQW laser diodes with Ga/sub 0.75/In/sub 0.25/Sb/InAs BGSL quantum wells. The laser structures employ Ga/sub 0.75/In/sub 0.25/As/sub 0.22/Sb/sub 0.78/ barrier layers, and InAs/AlSb superlattice cladding layers. The Ga/sub 0.75/In/sub 0.25/As/sub 0.22/Sb/sub 0.78/ barriers yield a type-I MQW with the BGSL active region, confining both electrons and holes, as well as enhancing the optical confinement factor of the structure due to their relatively large refractive index. The thicknesses of the Ga/sub 0.75/In/sub 0.25/Sb/InAs superlattice constituent layers have been varied to tune the emission wavelength of the devices, and a range of laser wavelengths has been demonstrated.

Mid-infrared semiconductor lasers with GaInSb/InAs type-II superlattices

We demonstrate midwave infrared (MID-IR) diode lasers that span most of the 3 - 4 micrometers range. Laser active regions are multiple quantum well (MQW) structures with GaInSb/InAs, type-II, broken gap superlattices for the wells and GaInAsSb for the barriers. The superlattice constituents and dimensions were tailored to reduce losses from auger recombination. AlSb/InAs superlattices are used for both n-type and p-type laser cladding regions.