Investigation of Scattering Losses in a Buried Tunnel Junction 4 µm GaSb VCSEL

The aim of this work is to investigate the scattering losses induced by the buried tunnel junction (BTJ) in a VCSEL operating at 4 µm for gas spectroscopy [1] . In this device, losses are even more important than in a standard VCSEL, due to the presence of an active region (AR) of type II which displays lower gain compared to type I. This is due to a reduced carrier wavefunction overlapped integral. Therefore a robust optical design should guarantee minimal losses. In fact, the presence of the BTJ inside the cavity enables scattering losses, which is a very well known problem in long wavelength VCSEL; in [2] the effect of the BTJ size in a VCSEL emitting at 2.3 µm was investigated by keeping the etching height constant and varying the step aperture and smoothness.