A review of MEMS external-cavity tunable lasers

The paper reviews the state-of-the-art of miniaturized tunable lasers constructed by microelectromechanical systems (MEMS) technology, covering various topics of laser configurations, theoretical studies and some design issues, with primary focus on the uniqueness of MEMS tunable lasers in comparison to conventional opto-mechanical counterparts. Further studies have also been presented to investigate the tuning range and stability in order to provide a deep understanding of the specialities of MEMS lasers in the sense of physics. The introduction of MEMS has endowed two special features to tunable lasers. One is that MEMS facilitates external cavities at very short (<100 νm) and even extremely short length (<10 νm), leading to unusual tuning behaviors and different design concerns. The other is that the photolithography of the MEMS process makes it possible to fabricate gratings/mirrors in arbitrary profiles, which may inspire the innovation of new laser configurations that can only be realized by MEMS technology. With further work on integration and packaging, MEMS lasers would be able to deliver their merits of small size, fast tuning speed, wide tuning range and IC integration compatibility, and to broaden their applications to many fields.