FM noise property of mutually optical injection‐locked semiconductor lasers considering propagation time between lasers

Abstract

Locking bandwidth and FM noise properties of mutually optical injection‐locked semiconductor lasers are described, taking into account an optical delay time between lasers. By introducing a figure of merit of optical injection specifying unilaterality of the optical injection, optical injection‐locking systems with an arbitrary inverse optical injection from a slave laser to a master laser can be described adequately. It is found from the analysis that for a short delay time, the locking bandwidth and the FM noise depend on both the round‐trip phase angle and the figure of merit of optical injection. In the case of a long delay time, the FM noise and the spectral linewidth are reduced significantly with increasing locking bandwidth. Finally, an undulation similar to that in the external cavity semiconductor laser appears in the FM noise spectrum. The experimental results obtained by using semiconductor lasers emitting at 0.83 μm agree well with the analytical results.