TRANSVERSE MODE SELECTION AND NOISE PROPERTIES OF EXTERNAL CAVITY VCSELs INCLUDING MULTIPLE REFLECTION EFFECTS

A theoretical analysis has been undertaken of the steady state transverse mode selection in Vertical Cavity Surface Emitting Lasers (VCSELs) subject to optical feedback in an external cavity connguration. Proper account is taken of multiple re-ections in the external cavity. The innuence of thermal eeects on the mode selection is also treated and noise properties of the connguration are discussed. The analysis pays speciic attention to the competition between the two lowest order modes (LP 01 and LP 11 degenerate modes) appropriate to the chosen circularly symmetric VCSEL structure. It is shown that preferential excitation of either mode can be eeected by appropriate choice of optical feedback delay. It is also shown that multiple reeec-1 tions in the external cavity can aaect the mode selection depending on the optical feedback delay. Thermal eeects are shown to be detrimental for transverse mode selection. Strategies to obtain a minimum impact of thermal eeects on mode selection are also discussed. Finally, relative intensity noise spectrum for each transverse mode is shown to maintain its double peak structure and low mode partition noise in the presence of optical feedback. A change from a twin peak to a single peak structure of this spectrum is also observed when changing the optical feedback delay.