Rate equation analysis of microcavity lasers

TLDR

The study investigates the light‑output properties of single‑mode microcavity lasers whose dimensions are comparable to the emitted wavelength. The authors derive a simple rate‑equation model for a four‑level laser that incorporates enhanced spontaneous emission into the cavity mode. Increasing spontaneous‑emission coupling into the cavity eliminates the lasing threshold, boosts efficiency, suppresses relaxation oscillations, and speeds the dynamic response, demonstrating the cavity’s spontaneous‑emission alteration is crucial.

Abstract

We describe the light output properties of single mode lasers having cavity dimensions on the order of the emitted wavelength. A simple rate equation formula is derived for a four-level laser assuming enhanced spontaneous emission into the cavity. These rate equation analyses show that increasing the coupling of spontaneous emission into the cavity mode causes the lasing properties to become quite different from those of usual lasers having cavity dimensions much larger than a wavelength. We find that the lasing threshold disappears, the light emission efficiency increases, relaxation oscillations do not occur, and the dynamic response speed is improved. It is shown that the spontaneous emission rate alteration caused by the cavity plays an essentially important role for these characteristics.