MEMS device for controlling evanescent field on side-polished optical fiber

Application of micro-electro-mechanical system (MEMS) technology for controlling the evanescent field is attractive because the dimension of the evanescent field is of the same order as that of the movement distance of the MEMS device. Two, different types of MEMS-based devices are proposed and developed for controlling the evanescent field generated at the surface of the side-polished optical fiber. The first one is a hybrid type and the other is a monolithic type. Both devices have merit and demerit from the aspects of process ease and alignment. The hybrid-type of device has a problem of close contact of the diaphragm with the side-polished optical fiber. The monolithic-type of device is a pre-aligned structure but has a difficulty in terms of polishing depth control on the single mode fiber. A change in the transmission spectrum due to device operation (movement of diaphragm with respect to polished optical fiber surface) has been noticed. However, the extent of change in transmission has to be improved. Fine control of polishing depth and parallel alignment of side-polished fiber with a diaphragm are the critical factors for effective interaction of the diaphragm with an evanescent field.