Digital chemical etching is used to trim the output mirror thickness of wafer-fused VCSELs emitting at a wavelength near 1.5 mu m. The fine control of the photon cavity lifetime thus achieved is employed to extract important device parameters and optimize the combination of the threshold current, output power, and direct current modulation characteristics. The fabrication process is compatible with industrial production and should help in improving device yield and in reducing manufacturing costs. (c) 2014 Optical Society of America