We review the family of optoelectronic devices whose performance is enhanced by placing the active device structure inside a Fabry‐Perot resonantmicrocavity. Such resonantcavity enhanced (RCE) devices benefit from the wavelength selectivity and the large increase of the resonant optical field introduced by the cavity. The increased optical field allows RCE photodetector structures to be thinner and therefore faster, while simultaneously increasing the quantum efficiency at the resonant wavelengths. Off‐resonance wavelengths are rejected by the cavity making RCE photodetectors promising for low crosstalk wavelength division multiplexing(WDM) applications. RCE optical modulators require fewer quantum wells so are capable of reduced voltage operation. The spontaneous emission spectrum of RCE light emitting diodes(LED) is drastically altered, improving the spectral purity and directivity. RCE devices are also highly suitable for integrated detectors and emitters with applications as in optical logic and in communication networks. This review attempts an encyclopedic overview of RCE photonicdevices and systems. Considerable attention is devoted to the theoretical formulation and calculation of important RCE device parameters. Materials criteria are outlined and the suitability of common heteroepitaxial systems for RCE devices is examined. Arguments for the improved bandwidth in RCE detectors are presented intuitively, and results from advanced numerical simulations confirming the simple model are provided. An overview of experimental results on discrete RCE photodiodes, phototransistors, modulators, and LEDs is given. Work aimed at integrated RCE devices,optical logic and WDM systems is also covered. We conclude by speculating what remains to be accomplished to implement a practical RCE WDM system.

Resonant cavity enhanced photonic devices

In complex optical systems comprising many individual components, precise mechanical alignment becomes a difficult problem. We propose to integrate free-space optical components using planar technologies for their fabrication.

Planar integration of free-space optical components

A normally-on electroabsorptive surface-normal Fabry-Perot reflection modulator is reported with an on/off ratio of 22, insertion loss of 3.7 dB, and bandwidth of 3.4 nm for an operating voltage swing of 11 V. The asymmetric Fabry-Perot structure is made with asymmetric mirrors using a quarter-wavelength grating of 15 1/2-periods on the bottom and an air-semiconductor interface on the top. The active region is 1.4 mu m thick and composed of 100AA GaAs/100 A Al/sub 0.2/Ga/sub 0.8/As multiple quantum wells. The structure provides both high-efficiency and bandwidth for surface-normal modulators. >

Electroabsorptive Fabry-Perot reflection modulators with asymmetric mirrors

The recent evolution of quantum-well self-electrooptic effect devices (SEEDs) for application in free-space optical switching and computing systems is reviewed. Requirements of these systems have stimulated the development of devices usable in large systems of cascaded devices (the symmetric SEED), large two-dimensional arrays of these devices with improved physical performance, logically smarter extensions of these devices (logic-SEEDs), and devices integrating electronic transistors with quantum-well modulators and detectors for both reducing the required optical energies and increasing functionality. This progress and its implications for future developments are summarized. >

Evolution of the SEED technology: bistable logic gates to optoelectronic smart pixels

The authors discuss a family of surface-normal electrooptic reflection modulators using asymmetric Fabry-Perot (ASFP) structures with GaAs-AlGaAs multiple quantum wells (MQWs) as the active medium. When an optimized top mirror reflectivity ( approximately 75%) is used, a voltage swing as low as 2 V is enough to change the device reflectivity by more than 40% with a contrast ratio of 50. A comparison with various Fabry-Perot structures shows that the ASFP is the best structure in terms of its operating voltage requirement and optical bandwidth. A sensitivity analysis shows that tolerances of 2 nm in operating wavelength, 0.5 V in operating voltage, 0.3% in layer thickness control or 10 degrees C in temperature variation can be expected from ASFPs with a finesse approximately 10. >

Surface-normal electroabsorption reflection modulators using asymmetric Fabry-Perot structures

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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C. W. Tu

Papers

Electrodispersive multiple quantum well modulator