Multifunctional Tunable Optical Filter Using MEMS Spatial Light Modulator

In this paper, we introduce a multifunctional tunable microelectromechanical systems (MEMS) optical bandpass filter that can continuously and independently tune the center wavelength and the passband spectral width. The filter function is achieved by dispersing the input light on a MEMS spatial light modulator (SLM) that is implemented with gold-coated mirrors microassembled on a MEMS platform. The mirrors are actuated by electrostatic combdrives that are bidirectional and have a maximum stable displacement of 44 ¿m in both directions for a total range of 88 ¿m. By actuating the SLM, the 1-dB bandwidth of the filter can be continuously tuned from 0.1 to 1.3 nm, and the 3-dB bandwidth can be tuned from 0.3 to 1.5 nm. In addition, the center wavelength can be fine tuned by actuating the movable blocking mirrors and coarsely tuned over a large spectral range by rotating the grating.