Large-area single-mode VCSELs and the selfaligned surface relief

The e®ect of mode-pro¯le speci¯c etching of the top layer in selectively oxidized VCSEL structures at 850 nm emission wavelength is examined. For high reproducibility, a self-aligned etching technique is used which aligns surface etch and oxide aperture by only one additional photoresist step. By optimizing layer structure and etch spot size, completely single-mode devices with aperture diameters up to 16m are obtained. Maximum single-fundamental mode output power of 3.4mW at room temperature and over 4mW at 0 ±C is obtained with a maximum far-¯eld angle of 5.5 ±. Using parameters for etch spot height and diameter, Gaussian beam spot size and phase curvature, the measured di®racted far-¯eld distribution is ¯tted well over a 20 dB intensity range. The chosen ¯t parameters therefore enable to estimate the amount of phase curvature within the VCSEL for di®erent operation currents, which cannot be obtained with available measurement methods. 1