Variable optical attenuator using thermo-optic two-mode interference device with fast response time.

A thermo-optic two-mode interference (TMI) waveguide structure with a silicon trench and heat-insulating grooves in both sides of the core has been proposed for a variable optical attenuator (VOA) with fast response time. Thermal analysis of the proposed thermo-optic TMI waveguide structure with a silicon oxinitride (SiON) core has been performed by using the implicit finite difference method. The heating power required to achieve the attenuated power of approximately -25.5 dB for a VOA with a silicon trench is 460 mW , which is approximately 1.8 times less than that of a VOA without a silicon trench. The response time is estimated as approximately 98 micros, which is faster than the response time of the existing VOA.