Phase noise of the radio frequency beatnote generated by a dual frequency VECSEL

Abstract

In this study, we demonstrate both experimentally and theoretically the phase noise characteristics of the radio frequency (RF) beatnote, generated by optical mixing of the two orthogonally polarized modes in a dual frequency Vertical External Cavity Surface Emitting Laser (VECSEL). We investigate the high frequency (100 kHz to 50 MHz) behavior of the RF phase noise for different nonlinear coupling strengths between the two laser modes, which generate the RF beatnote through optical mixing. In the theoretical model, we have only considered the effect of the intensity noise of the two laser modes on the phase noise via strong phase-intensity coupling due to large Henry factor of the semiconductor gain medium of our VECSEL. The model is based on the assumptions that the only source of noise for the two laser modes is the pump intensity fluctuations and the pump fluctuations entering into the two laser modes are white noises of identical amplitudes, partially correlated and in phase.