Large-area single-mode VCSELs and the self-aligned surface relief

The effect of mode-profile specific etching of the top layer in selectively oxidized vertical-cavity surface-emitting laser (VCSEL) structures at 850- nm emission wavelength is examined. For high reproducibility, a self-aligne d etching technique is demonstrated which aligns surface etch and oxide ape rture by only one additional photoresist step. By optimizing layer structur e and etch spot size, completely single-mode devices with aperture diameter s up to 16 mum are obtained. Maximum single-fundamental-mode output power o f 3.4 mW at room temperature and over 4 mW at 0 degreesC is obtained with a maximum far-field angle of 5.5 degrees. Using parameters for etch spot hei ght and diameter, Gaussian beam spot size and phase curvature, the measured diffracted far-field distribution is fitted well over a 20-dB intensity ra nge. The chosen fit parameters therefore enable one to estimate the amount of phase curvature within the VCSEL for different operation currents, which cannot be obtained with available measurement methods.