Transverse-mode selection and noise properties of external-cavity vertical-cavity surface-emitting lasers including multiple-reflection effects

A theoretical analysis has been undertaken of steady-state transverse-mode selection in vertical-cavity surface-emitting lasers (VCSEL's) that are subject to optical feedback in an external-cavity configuration. Multiple reflections in the external cavity are taken into account. The influence of thermal effects on mode selection is also treated, and noise properties of the configuration are discussed. In the analysis specific attention is paid to the competition between the two lowest-order modes (LP01 and LP11 degenerate modes) that are appropriate to the chosen circularly symmetric vertical-cavity surface-emitting laser structure. It is shown that preferential excitation of either mode can be effected by the appropriate choice of optical feedback delay. It is also shown that multiple reflections in the external cavity can affect the mode selection, depending on the optical feedback delay. Thermal effects are shown to be detrimental for transverse-mode selection. Strategies for the minimization of thermal effects on mode selection are also discussed. Finally, the relative intensity noise spectrum for each transverse mode is shown to maintain its double-peaked structure and low mode-partition noise in the presence of optical feedback. A change from a twin-peaked to a single-peaked structure of this spectrum is also observed when the optical feedback delay is changed. (C) 1999 Optical Society of America [S0740-3224(99)00911-X].