GaAlAs/GaAs micromachined tunable vertical filter with low tuning voltage below 5 volts

MEMS based tunable filters and vertical cavity surface-emitting lasers (VCSELs) are attracting much interest because of their unique features, such as wide continuous tuning, polarization insensitive operation and 2-dimensional array integration. There remain difficulties in tuning range and tuning voltage of such MEMS based filters using electrostatic force because a micromachined cantilever is pulled down by an electrostatic force and its actual allowed movement is limited to be 1/3 of the air gap width. Also, a tuning voltage is typically several tens of volts. In this paper, we propose and demonstrate a GaAlAs/GaAs micromachined tunable filter with a thermal strain control layer and a heating element, which enable low tuning voltage. We present the design of thermally tunable filters with a tuning range of over 300 nm. Experimentally, we demonstrate wavelength tuning of a thermally tunable MEMS filter, which shows a record low tuning voltage of 4.7 V for tuning range of 23.2 nm.