D.E. Mull

Wafer fusion: A novel technique for optoelectronic device fabrication and monolithic integration

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.

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.

Gallium phosphide microlenses by mass transport

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°.

Large‐numerical‐aperture microlens fabrication by one‐step etching and mass‐transport smoothing

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.

High-power nearly diffraction-limited AlGaAs-InGaAs semiconductor slab-coupled optical waveguide laser

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 /spl mu/m by 3.4 /spl mu/m 1/e/sup 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/sup 2/ indicate that the SCOWL output beam is nearly diffraction-limited in both directions with M/sub x//sup 2/ /spl sim/ M/sub y//sup 2/ /spl sim/ 1.1 over the entire range of output powers measured.

Large‐numerical‐aperture InP lenslets by mass transport

Lenslets with diameters up to 130 μm and numerical apertures of 0.39–0.75 have been formed in InP substrates by using mass transport to smooth out chemically etched multilevel mesa structures. The lenslets show a smooth surface with an accurately controlled profile (i.e., curvatures) and are capable of forming clear images. Some lenslets (with a diameter of approximately 67 μm) have been used to collimate the output of a buried‐heterostructure diode laser (of 1.3 μm wavelength) and resulted in a nearly diffraction‐limited beam divergence of 1.4°.

Practical OEICs based on the monolithic integration of GaAs-InGaP LEDs with commercial GaAs VLSI electronics

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 (OEICs), have resulted in improved integrated light-emitting diodes (LEDs), 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.

Fabrication of two-sided anamorphic microlenses and direct coupling of tapered high-power diode laser to single-mode fiber

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.<<ETX>>

Accurate fabrication of anamorphic microlenses and efficient collimation of tapered unstable‐resonator diode lasers

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° 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.

High-speed high-density parallel free-space optical interconnections

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.