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.

Beam-quality measurements on the output of a 915-nm AlGaAs-InGaAs-GaAs slab-coupled optical waveguide laser (SCOWL) are reported. This device had a nearly circular mode (3.8 mum by 3.4 mum 1/e(2) widths in the near-field) and was capable of a single-ended continuous-wave output power of greater than 1 W. Measurements of M-2 indicate that the SCOWL output beam is nearly diffraction-limited in both directions with M-x(2) similar to M-y(2) similar to 1.1 over the entire range of output powers measured.

This paper reports on recent progress in AlGaAs/InGaAs slab-coupled optical waveguide laser (SCOWL) devices. 975-nm and 915-nm SCOWL devices have been operated in single fundamental mode output to > 1-W output power. Further increases in single-mode power at 975 nm have been achieved by scaling the waveguide thickness. Array of SCOWL devices with up to 10 elements have also been constructed. The power scales essentially with the number of elements, and 9.8 W of total cw power has been obtained from a 10-element array.

A high-brightness semiconductor diode laser concept, which utilizes a slab-coupled optical waveguide region to achieve several potentially important advances in performance, is described. Results on devices, which utilize this design concept, in InGaAsP/InP and AlGaAs/InGaAs/GaAs are presented.

We recently proposed a new class of semiconductor diode laser, the slab-coupled optical waveguide laser (SCOWL) that offers several advantages for single-spatial mode, high-output power devices. Mode filtering due to slab coupling of higher-order modes allows for a much larger single mode and a lower density at the facets, and the low loss permits die construction of long devices that reduce beat dissipation in the device at high power operation. In addition, SCOWL devices can be designed such that the spatial mode profile is nearly circular, allowing for high-coupling efficiency butt coupling (without the use of lenses) to single-mode fibers.

Bromineion-beam-assisted etching produces smooth vertical sidewalls in GaAs, GaP, InP, AlSb, and GaSb as well as in the usual alloys formed from these materials. Care must be taken, however, during etching to match the specific material system with an appropriate substrate etch temperature. For example, vertical walls were obtained using substrate temperatures in the range of 150 to 200°C with InP, 80 to 140°C with GaAs and GaP, and below 30°C with AlSb and GaSb. GaN has also been etched with the technique. Our etching experience and the vapor pressure data for bromine with group III and group V elements lead us to believe that all of the various technologically important III-V binaries, ternaries, and quaternaries can be etched. Etch rates of most of the materials can be varied from several nm/min to 0.16 µm/min through the bromine flow rate, Ar + ion beam density and energy, and the substrate temperature. Bromine ion-beam-assisted etching also appears to have an advantage over chlorine ion-beam-assisted etching in many situations, in that substrate temperature ranges can be found for which vertical sidewalls are maintained while etching through layered structures composed of various alloys of the materials. Here we present results obtained from etching a number of III-V binaries, alloys, and heterostructures.

Bromine ion-beam-assisted etching produces smooth vertical sidewalls in GaAs wafers with substrate temperatures in the range of 20–200 °C and smooth vertical sidewalls in InP wafers with substrate temperatures in the range of 150–200 °C. Etch rates can be varied from several nm/min to 0.16 μm/min through the bromine flow rate, Ar+ ion beam density and energy, and the substrate temperature. The etching rate ratios of bromine-only etching (no Ar+ ion beam) to argon ion-beam-assisted bromine etching to argon ion etching (no bromine) with an ion beam density of 40 μA/cm2 and ion beam energy of 500 V were measured to be 11.5:23:1 and 16:125:1 at a substrate temperature of 200 °C and 2:42:1 and 1:40:1 at a substrate temperature of 100 °C for GaAs and InP, respectively. Such rate enhancements were found to be typical with these materials. Bromine ion-beam-assisted etching also appears to have an advantage over chlorine ion-beam-assisted etching in that high anisotropy can be achieved with bromine in both the GaAs and the InP materials systems at substrate temperatures as high as 200 °C as compared to chlorine where the etching of GaAs is spontaneous and isotropic at temperatures above 150 °C.

Recent advances in the Epitaxy-on-Electronics (EoE) integration process, which combines commercial GaAs VLSI electronics with conventional epitaxial growth and fabrication to produce complex, monolithic optoelectronic integrated circuits (OEIC's), have resulted in improved integrated light-emitting diodes (LED's), eliminated any impact on the preexisting electronics, and increased the robustness of the integration process. An EoE-integrated OEIC combining a photodetector, electronics, and LED is presented which demonstrates the capability of this technology to now satisfy practical optoelectronic systems requirements.

Optical interconnects for use in high speed computing and communication systems require dense optoelectronic integrated circuits (OEICs). Monolithic integration of III-V optoelectronics with VLSI-complexity electronics will yield OEICs of the high density, performance, manufacturability, and reliability. The Epitaxy-on-Electronics (EoE) technique monolithically integrates optoelectronic devices with commercially-fabricated, fully-metallized GaAs VLSI integrated circuits. This manuscript reviews the EoE process and details the fabrication of integrated LEDs. This LED-OEIC process is being used by optical interconnect systems researchers on a prototype basis through the OPTOCHIP project; the current status of this effort is reviewed.

Uniform linear arrays of strained-layer multiple-equantum-well InGaAs-AlGaAs ridge-waveguide diode lasers have been fabricated that operate near 980 mn and have low threshold currents I-th and high differential quantum efficiencies eta(d). Uniformity was achieved by a combination of uniform ion-beam-assisted etching with an electron cyclotron resonance ion source and uniform organometallic vapor-phase epitaxial (OMVPE) growth. We investigated the effects of device geometry, namely, ridge width, cavity length, and remaining cladding thickness outside the ridge t, on I-th and eta(d). For uncoated lasers with 500-mu m-long cavities; 2- to 3-mu m-wide ridges, and t = 165 +/- 75 nm fabricated in double-quantum-well OMVPE material, I-th was typically in the range 6-7 mA and eta(d) was >40% per facet, A 24-element array of 2-mu m-wide, 200-mu m-long ridge-waveguide lasers with a high reflection coating on the back facet exhibited excellent uniformity, with threshold currents and single-ended differential quantum efficiencies that averaged 3.4 mA and 72%, respectively, Similar arrays with high-reflectivity coatings on both facets exhibited threshold currents as low as 2 mA.

An anamorphic microlens has been developed to couple a tapered unstable-resonator laser directly to a single-mode fiber, and has demonstrated capability for simple, compact and efficient high-power diode laser systems. Far high collection and coupling efficiencies, the refractive microlens has been fabricated by utilizing both sides of a GaP substrate, in which the first side was used to remove the astigmatism of the laser output and the second side to focus the beam to a spot size comparable to the fiber mode. The microlenses have been accurately formed by using a recent technique of mass-transport smoothing of etched multimesa preforms. Initial fiber-coupling experiments showed powers as high as 360 mW at the fiber output, and coupling efficiency as high as 29.5% has been measured at a lower power.< >

Summary form only given. Modules which implement high-density parallel free-space board-to-board optical interconnections have been constructed with linear arrays of components. These free-space optical interconnections provide the capability for dense z-axis interconnections perpendicular to boards or multichip modules. Each parallel interconnection contains an edge-emitting InGaAs laser array, transmitter and receiver lens arrays, and an InGaAs detector array flip-chip attached to a GaAs heterojunction bipolar transistor amplifier array

Highly precise f/0.9 refractive anamorphic microlenses have been fabricated in GaP substrates by mass-transport smoothing of etched multiple-mesa structures. Astigmatic outputs from tapered unstable-resonator lasers have been collimated to a nearly round beam of near diffraction-limited 0.43-degrees divergence. Initial good efficiencies (as high as 35%) have been obtained in coupling the laser output into a single-mode fiber. These lenses are highly promising for realizing simple compact optical systems that exploit the high power capability of tapered lasers.

We describe the successful fabrication of the first mass-transported microlenses in GaAs, suitable for monolithic integration with lasers. We also describe a novel two-sided microlens in a GaP substrate, designed for high collection efficiency from a tapered laser and direct coupling to a single-mode fiber

Precision f/1 microlenses have been fabricated in GaP by smoothing a multiple-mesa structure etched with a designed width and length variation. High-resolution lithography and ion-beam- assisted etching were used for mesa definition and resulted in accurate lens profiles after mass-transport smoothing at 900–1070 °C. This much simplified fabrication technique is highly promising for efficient, diffraction-limited micro-optical elements.

We describe the fabrication of the first anamorphic microlenses which are needed for the astigmatic output of unstable-resonator lasers and traveling-wave amplifiers with laterally tapered (i.e., flared) gain regions. Such lenses offer a means to realize simple and compact optical systems exploiting the demonstrated high-power capability of the new lasers

Large-numerical-aperture microlenses have been fabricated in compound semiconductors by chemical etching and mass transport (surface-energy minimization) and have been monolithically integrated with GaInAsP/InP surface-emitting lasers. The microlenses showed smooth surface, accurate profiles, and near diffraction-limited beam collimation. Techniques have been developed for accurate alignment between microlenses and buried-heterostructure waveguide gain regions fabricated on opposite sides of a substrate. The integrated devices showed room-temperature pulsed threshold currents of 70 mA, narrow beam divergence of 1.25 deg, and are potentially advantageous for fiber coupling, optical interconnects, laser-array applications, etc.

A new surface-emitting diode laser has been demonstrated, which consists of a buried-heterostructure waveguide gain region on one side of the substrate and a bifocal microlens of 210 μm diameter on the other side. The bifocal microlens is composed of a collimating lens in the center (70 μm diameter) and a spherical mirror in the surrounding region, for output collimation and optical feedback, respectively. Accurate alignment between the gain region and the microlens has been obtained by using the focused light spot produced by the latter. Initial device results show room-temperature pulsed threshold currents around 92 mA (with a low of 70 mA) and far-field patterns with a narrow central lobe of 1.25°.

Centimeter-size single-crystal InP or GaAs wafers have been fused together entirely, face to face or side by side, after a heat treatment in a graphite/quartz reactor which can press the wafers together through differential thermal expansion. Diodes formed by fusing p- and n-type wafers showed normal current-voltage characteristics and light emission. Fusion between lattice-mismatched wafers (i.e., InP and GaAs) has also been demonstrated.

Arrays of high quality refractive microlenses have been formed in GaP substrates by mesa etching followed by a heat treatment in which the multistep mesas were smoothed due to surface energy minimization. A smooth lens surface and an accurately controlled lens profile have been obtained. Microlenses of 130 μm diameter and 200 μm focal length have been used to collimate the outputs of GaInAsP/InP and GaAs/GaAlAs diode lasers and have yielded a nearly diffraction-limited beam divergence of 0.68°.