Static, dynamic, and noise characteristics of vertical-cavity surface-emitting lasers

Thesis (Ph. D.)--University of Rochester. Institute of Optics, 1998. Missing bibliography pages covering references 29-73.An important aspect of vertical-cavity surface-emitting lasers (VCSELs) that needs to be improved is its stable operation in a single transverse mode. Due to relatively large dimensions of VCSELs (~ 10 μm radius), spatial hole-burning and carrier diffusion affect device performance significantly, especially because VCSELs often operate in several transverse modes at high injection currents. In this thesis, a comprehensive numerical study of such spatial effects on the static, dynamic, and noise characteristics of VCSELs is presented. The computer model includes the spatial dependences of both the optical field and the carrier density. Device characteristics are analyzed under different operating conditions, including continuous-wave (CW) operation, gain-switched operation, optical feedback, and optical injection. Both single-mode and two-mode operations are analyzed. Under CW operation, transverse-mode competition induced by spatial hole-burning is found to affect the static and noise characteristics significantly. In particular, transverse-mode competition affects the mode-partition noise. Under single-mode gain-switched operation, it is shown that by using an appropriate electrical contact, spatial hole-burning can be avoided and shorter pulses can be obtained. Under two-mode gain-switched operation, transverse-mode competition gives rise to rich nonlinear dynamics. The effect of external influence has also been studied. It is found that optical feedback or optical injection can force a two-mode VCSEL to operate in a single transverse mode under appropriate conditions. However, distant feedback or injection outside the locking region can destabilize the CW operation and lead to interesting nonlinear dynamics. The feedback strength and the injection power at which oscillations occur depend critically on the strength of intermodal coupling. In general, results indicate that strong intermodal coupling reduces the sensitivity of the VCSEL towards external influence. Experiments have been conducted on a VCSEL to investigate the multiple-transverse-mode emission characteristics. Results show that multimode operation leads to considerable degradation of device performance, such as the distortion of light-current curves of the orthogonally polarized components, degradation of spatial beam quality, broadening of the optical spectrum, and modification of the mode-partition noise. Optical feedback effects on VCSEL characteristics have also been explored, and it is found that feedback leads to quasi-periodic oscillations