Wide continuously tunable 1.55μm vertical air-cavity wavelength selective elements for filters and VCSELs using micromachined actuation

Tailored scaling allows the effectiveness of physical effects and mechanical stability to be enhanced. This is shown for micromachined 1.55 mu m vertical-resonator-based filters and VCSELs, capable of wide, continuous, and kink-free tuning by a single control parameter. Tuning is achieved by mechanically actuating one or several membranes in a vertical air-gap resonator including two highly reflective DBR mirrors. Electrostatically actuatable single-chip filters including InP/air-gap DBR's (3.5 periods) reveal a continuous tuning up to 14% of the absolute wavelength. Varying a reverse voltage (U = 0 .. -3.2V) between the membranes (almost flat in the unactuated condition) a tuning range up to 142nm was obtained. Varying a reverse voltage (U = 0 .. -28V) between the membranes (strained and curved in the unactuated condition) a tuning range up to 221nm was obtained. Optically pumped and continuously tunable 1.55 mu m VCSELs show 26nm spectral tuning range, 400 mu W maximum output power, and 57dBm SMSR. This two-chip VCSEL has a movable top mirror membrane, which is precisely designed to obtain a specific air-gap length and a tailored radius of curvature in order to efficiently support the fundamental optical mode of the plane-concave resonator. The curved top mirror DBR membrane consists of periodically alternating differently stressed silicon nitride and silicon dioxide multilayers. The lower InP-based part consists of the lnP/GalnAsP bottom DBR and the GalnAsP active region.