J. N. Walpole

High‐power strained‐layer InGaAs/AlGaAs tapered traveling wave amplifier

High power, nearly diffraction‐limited cw performance has been obtained from a traveling wave amplifier, fabricated in a strained‐layer InGaAs/AlGaAs laser structure, with a laterally tapered gain region and with a cavity‐spoiling feature to prevent laser oscillation. The input beam diffracts as it propagates, efficiently filling the tapered active region. For input optical power of 85 mW from a Ti:sapphire laser, total cw output of 1.44 W has been achieved with 1.28 W in a central lobe with width less than 1.2 times the diffraction limit at 977 nm wavelength. Only 15 mW of power incident on the amplifier was sufficient to provide 1 W output into the central lobe.

High-power, strained-layer amplifiers and lasers with tapered gain regions

Laterally tapered gain regions designed to accommodate the diffraction of narrow single-lobe beams that have been used in both optical amplifiers and lasers are described. Amplifier output power of 3.5 W with 3.1 W in a 1.05 times diffraction-limited lobe and laser output power of over 4 W with approximately half the power in a 1.7 times diffraction-limited lobe have been achieved.<<ETX>>

Microchannel heat sinks for two-dimensional high-power-density diode laser arrays

The operation of a two-dimensional GaInAsP/InP diode laser array with CW power dissipation up to 500 W/cm/sup 2/ into a Si microchannel heat sink is discussed. The approximately 1*4-mm/sup 2/ laser array was used to characterize the heat sink, and the value of 0.040 degrees C cm/sup 2//W was obtained for the thermal resistance per unit area. The extrapolated value for a 1-cm/sup 2/ heated area is 0.070 degrees C cm/sup 2//W. >

A novel technique for GaInAsP/InP buried heterostructure laser fabrication

A simple fabrication technique for GaInAsP/InP buried heterostructure lasers has been developed based on a newly observed mass transport phenomenon on chemically etched InP mesas. Threshold currents as low as 9.0 mA have been obtained.

Low‐threshold InGaAs strained‐layer quantum‐well lasers (λ=0.98 μm) with GaInP cladding layers and mass‐transported buried heterostructure

Buried‐heterostructure quantum‐well lasers fabricated by mass transport are reported for In0.18Ga0.82As/GaAs/Ga0.5In0.5P strained‐layer structures grown by atmospheric pressure organometallic vapor‐phase epitaxy. Threshold current densities as low as 85 A/cm2 are measured for broad‐stripe lasers, and buried‐stripe devices show threshold currents as low as 3 mA and differential quantum efficiencies as high as 34% per facet without coatings.

Double‐heterostructure PbSnTe lasers grown by molecular‐beam epitaxy with cw operation up to 114 K

Double‐heterostructure Pb1−xSnxTe lasers with active regions of Pb0.782Sn0.218Te have been grown by molecular‐beam epitaxy which operate cw up to heat‐sink temperatures of 114 K. Temperature tuning of the emission from 15.9 to 8.54 μm wavelength is obtained, with emission at 77 K near 11.5 μm. The current‐voltage characteristics show an abrupt change in slope at threshold, indicating high incremental internal quantum efficiency.

Surface-emitting GaInAsP/InP laser with low threshold current and high efficiency

A buried‐heterostructure laser has been developed whose output is deflected to a direction perpendicular to the substrate surface by a monolithically integrated 45° (parabolic) mirror. The latter is fabricated by smoothing a chemically etched multistep structure using a mass‐transport phenomenon. The present devices show threshold current as low as 12 mA, differential quantum efficiency as high as 47% and a surface‐emitting far‐field pattern with a main lobe as narrow as 12°.

GaInAsP/InP Double-heterostructure lasers

A method and apparatus is described wherein a buried double heterostructure laser device is formed utilizing epitaxial layers of quaternary III-V alloys of gallium indium arsenide phosphide and wherein the buried layer is formed by first etching the p-type top layer of the structure down to the quaternary active layer forming a mesa. A second etchant is then provided which preferentially etches the active layer. This etchant is used to undercut the top layer by removing the active layer on both sides of the top mesa surface providing a narrow strip of active layer underneath the undercut mesa. The undercut is then filled in by a heat treatment process which results in migration or transport of the binary top layer and binary bottom layer to fill in the undercut, leaving the active layer buried in the binary material. In an alternate embodiment of the invention, the two-step etching process plus the transport phenomena is utilized to form the mirror surface of a laser device. The device may include a support mesa and control mesa structure and may also be used to fabricate optical waveguide structures.

Single heterojunction Pb1−x Snx Te diode lasers

Single heterojunction diode lasers in the Pb1−xSnx Te alloy system have been fabricated by low‐temperature vacuum deposition of n‐PbTe on a p‐Pb0.88Sn0.12 Te substrate. The lasers have lower threshold current densities and operate cw at higher temperatures than homojunction devices in this material. At laser threshold the incremental diode resistance drops abruptly from 0.5 Ω to a series resistance limited value of 0.08 Ω, a previously unobserved effect in diode lasers which indicates very high internal quantum efficiency.

AlGaAs-InGaAs slab-coupled optical waveguide lasers

The slab-coupled optical waveguide laser (SCOWL) concept, recently proposed and demonstrated, is extended to the AlGaAs-InGaAs-GaAs material system. Both 980- and 915-nm SCOWL devices feature a nearly circular large-diameter single-spatial mode that can be butt coupled with high efficiency to a single-mode fiber. Single-ended continuous-wave output powers of greater than 1 W have been obtained at 980 nm.