We have microfabricated low-threshold, high-speed vertical-cavity lasers and optical switches by optimizing the mirror design, crystal growth, and ion etching of microresonators. By minimizing the sidewall ion damage in electrically pumped microlasers, we have defined large arrays of 3-μm-diam surface-emitting devices with threshold currents below 1.5 mA. Ion beam etching was also used to define 0.5–1.5 μm wide all-optical microresonator switches with recovery times as low as 30 ps and controlling energies as low as 0.6 pJ.

Vertical-cavity surface-emitting lasers14 show promise for a variety of applications. High-power, low-cost laser sources might result from large coherently coupled arrays. Small arrays could accomplish high-speed communication between electronic chips, overcoming a bottleneck that presently limits the speed of computers. In the longer term, arrays of laser-based logic gates may be used for photonic switching in communication networks or for digital or neural computing. In these information processing applications, minimizing the threshold is essential. The lowest threshold edge-emitting lasers57 contain a single quantum well (SQW) and require approximately 0.55 mA. Minimum thresholds will be attained by minimizing the volume of active material in the laser, which in turn requires high-reflectivity mirrors. GaAs-AlAs mirrors grown by molecular beam epitaxy (MBE) have achieved extremely high reflectivity (>99%), high enough to achieve optically pumped lasing in a vertical cavity with an

We have devised a novel vertical-cavity top surface-emitting GaAs quantum well laser structure which operates at 0.84 μm. The laser combines peripheral current injection with efficient heat removal and uses only the epitaxially grown semiconductor layers for the output mirrors. The structure is obtained by a patterned deep H+ implantation and anneal cycle which maintains surface conductivity while burying a high resistance layer. Peripheral injection of current occurs from the metallized contact area into the nonimplanted nonmetallized emission window. For 10-μm-diam emitting windows, ∼4 mA thresholds with continuous-wave (cw) room-temperature output powers ≳1.5 mW are obtained. Larger diameter emitting windows have maximum cw output powers greater than 3 mW. These are the highest cw powers achieved to date in current injected vertical-cavity surface-emitting lasers.

Quantum-confined Stark effect is combined with a Fabry–Perot resonance to build a multiple quantum well electro-optic modulator. The structure consists of GaAs/AlGaAs quantum wells between two epitaxial AlAs/AlGaAs dielectric multilayer mirrors, all grown by molecular beam epitaxy. The modulator uses refractive index changes induced by applied electric fields. In reflection mode of operation, the modulator demonstrates >5:1 contrast ratio and >50% absolute maximum reflectivity with 17 V applied.

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