Monolithically integrated resonant-cavity photodetectors for measurement and feedback control of spontaneous and stimulated emission

This paper presents a study of the physics and applications of resonant cavity pin photodetectors strategically positioned within the optical structure of vertical microcavity surface emitting devices. Conventional AlGaAs resonant cavity light-emitting diodes and vertical cavity surface emitting lasers (VCSELs) emitting near 780 nm are examined. However, the structures include resonant cavity detectors placed within the upper or lower distributed Bragg reflectors. The detectors consist of an undoped quantum well absorbing layer positioned at an antinode of the resonant standing wave.A classical model is developed to examine the detector's spectral responsivity. This embedded detector scheme provides an effective means for studying the spontaneous and stimulated emission components of microcavity light emitting devices. The photocurrent from the intracavity detector is proportional to the microcavity output power over a broad emission range. This is especially useful for the control of VCSEL output power by means of a feedback circuit.