MEMS variable optical attenuator using a translation motion of 45° tilted vertical mirror

A reflection-type variable optical attenuator (VOA) using the translation of a 45° tilted vertical mirror is proposed. The translation of the mirror results in an optical axis offset between transmitting and receiving optical signal, which attenuates the transmitted optical power. Single- and dual-mirror-type VOAs are implemented and compared. A conic-cladding fiber and collimating lensed fiber are applied for low insertion loss. Optical attenuation performances are predicted using the CODE V optical simulator. An electrical spring method is studied for mode separation of the mirror actuator. The self-aligned metal interlayer process is applied for achieving a notching-free mirror surface. Performances of the fabricated VOAs are measured and discussed. An attenuation range is achieved from −0.9 dB (0 V) to −35 dB (10 V). The wavelength-dependent loss (WDL) is as small as 0.4 dB even at −20 dB attenuation level. Excellent polarization-dependent loss (PDL) less than 0.24 dB is achieved in the whole attenuation range.