Study On The Steady Gain And Dynamic Switching Characteristics Of Vertical-Cavity Semiconductor Optical Amplifiers

With the development of vertical-cavity surface emitting lasers (VCSELs), vertical-cavity semiconductor optical amplifiers (VCSOAs) have been the topic of increasing interest. Compared with conventional edge-emitting semiconductor optical amplifiers (SOAs), VCSOAs have the inherent advantages of polarization insensitivity, high fiber coupling efficiency, and easy for fabricating two-dimensional arrays on wafer. Therefore, VCSOAs have a wide range of potential applications in optical communication networks, optical signal processing, and optical computations.Considering the fact that coupling efficiency into VCSOA is hard to evaluate in existing rate equation models of VCSOA, according to the boundary condition of Fabry-Perot resonator and the gain enhancement factor varying with axial position of the standing wave effect in micro-cavity, a new model of VCSOA is established by using traveling-wave equation and position dependent carrier equation. By finding the self-consistent solution of equations, the distributions of carriers and photons in cavity are presented. Meanwhile, reflection gain is investigated, and basic agreement with theoretical and experimental data is obtained.The dynamic switching characteristics of VCSOA are theoretically analyzed with transfer matrix method and carrier rate equation for the first time, which is different from conventional gain formula of Fabry-Perot resonator. The results show that switching delay time on the order of ns and output extinction ratio of more than 15 dB are obtained when VCSOA is used as optical switch. Meanwhile, switching delay time and output extinction ratio can be simultaneously improved by decreasing the mirror periods of top distribution Bragg reflector (DBR) under the condition that large gain can be achieved, and setting the off-state in the level which is a little larger than that of gain cancellation. In order to verify the theoretical model, amplifying response is obtained when both input signal and pump are pulses simultaneously, which is in basic agreement with experimental result.