Temperature dependence of the spontaneous emission factor in microcavities

Abstract

In the literature, theoretical studies have indicated the quantisation of optical modes by cavity confinement may lead to enhancement of spontaneous emission factor β. Placement of a radiating system within a cavity with a dimension the order of one wavelength alters the number of allowed optical modes to which photons couple. However, this does not guarantee enhancement. A typical semiconductor laser will be required to operate over a temperature range of at least 80 o C. Here we model the confinement of a radiating source between two DBR mirrors forming a planar microcavity and consider β as a function of temperature where we use a calculated temperature dependent emission line, which the authors believe to be the first investigation including cavity effects. The results show that at threshold β has a broad maximum with increasing temperature.

Temperature effects in metal-clad semiconductor nanolasers

“…The effect of the temperature on the real parts of the cladding and semiconductor permittivities is not as dramatic. The rapid rise in β max with temperature and the subsequent broad maximum was similarly observed for VCSELs and microcavities [48,49]. However, the critical temperature at which β decreases sharply appears to be lower for a subwavelength cavity.…”

“…This appears to be a direct consequence of the sparse mode density in the cavity that we have considered. Furthermore, as a consequence of the small number of total modes, β max is much higher in the metallo-dielectric lasers that we analyze, compared to those analyzed in [48] and [49].…”

“…However, the critical temperature at which β decreases sharply appears to be lower for a subwavelength cavity. The transition temperatures of [48] and [49] were approximately 240 K and 290 K, respectively. In this sense, our analysis demonstrates the rather non-intuitive result that β of a subwavelength cavity may be more robust to temperature variation than that of a larger laser.…”

“…As an example, we simulate a nanolaser geometry similar to that shown in Figure 3A, but with a gain radius of 250 nm and optimal shield thickness of 100 nm, using the commercial software COMSOL Multiphysics' EM module. In Figure 3D, the resonant wavelengths of the first six cavity modes are plotted as a function of temperature, for both a positive [46] and effectively negative TOC [48,49] of the gain medium. The latter corresponds to the empirical observations of Massum et al [48] and Ramoo et al [49].…”

“…In Figure 3D, the resonant wavelengths of the first six cavity modes are plotted as a function of temperature, for both a positive [46] and effectively negative TOC [48,49] of the gain medium. The latter corresponds to the empirical observations of Massum et al [48] and Ramoo et al [49]. In these works on InGaAsP-based cavities, the resonant wavelength was observed to increase with the temperature.…”