Microcavity Emitters and Detectors

Abstract

Modern crystal growth methods allow multilayer heterostructures to be incorporated in a variety of novel and useful devices. For example, the use of distributed Bragg reflectors (DBR’s) with high reflectivity designed for a specific wavelength has led to microcavities for both light emitters and detectors. This has revolutionized the design of semiconductor lasers, which now have resonant cavities on the order of a single wavelength of light. Photodetectors also have been changed by incorporating DBR’s to form microcavities for absorption. The resonant-cavity photodiode structure in effect decouples the quantum efficiency from the transit-time. It is also possible to introduce additional periodicities in the mirror design to achieve reflectivity at two (or four) separate wavelengths. These wavelength-selective mirrors should have a variety of applications in wavelength division multiplexing. Lasers and detectors employing resonant cavities on the wavelength scale will play an important role in a variety of future optoelectronic applications, and for optical interconnects. By using techniques such as selective oxidation of AlAs layers, it is possible to define cavities in the lateral plane as well as vertically between the DBR’s. As a result of these advances in the design of microcavities, new approaches to low-dimensional confinement of photons are possible, in analogy to the study of electron confinement.