Study On Silicon Based MEMS Optical Switch

A novel self-aligned optical switch with torsional beams and vertical mirror is designed and fabricated based on silicon micromachhing technology for optical networks. It exhibits high properties, such as low insertion loss, high switching contrast, small crosstalk, low driving voltage and millisecond switching time.The large displacement of the micro actuator if needed for the low insertion loss in optical coupling. A novel large displacement actuator with torsional beams and vertical mirror is designed to solve the confliction among the low driving voltage, large displacement and high first mode frequency. The actuator presents low driving voltage (<36V), large displacement , suitable first mode frequency (500Hz) and fast switching time (<3ms) in device design. The insertion loss less than 1 dB is obtained in design according to the parameters of Corning Co. standard lensed fiber and the RMS of the etched vertical silicon (100) plane. The cross-coupling between the cells of electrostatically driving matrix is first studied by means of Finite Element Method (FEM) and the results have been applied in designing optical switch matrix.The switch is fabricated utilizing the bulk silicon micromachining technology. It shows the yield reaches 90% and being suitable for batch-fabrication. A matrix contained four cells is also fabricated and occupies an area almost as same as single switch which shows the switch is promising in building optical matrix.The driving voltage of the switch will be increased and the switching contrast will be decreased because there is convex corner under-cutting during the formation of silicon mirror etched by the aqueous KOH. This paper presents a novel compensation technology for the (100) silicon convex corner under-cutting with <100> direction masks. The convex comer under-cutting of mirror is well compensated utilizing the new compensationtechnology. A novel method is found for fabrication silicon tip during the process of the switch.The switch exhibits insertion loss 1.9dB and excellent switching contrast 70dB with the reflection of mirror while low insertion loss 1.48dB and the excellent switching contrast 70dB without the reflection of mirror. The switching time is 3.9ms and the crosstalk is -50dB. These specifications are comparable with those of the traditional mechanical optical switches.