An all-silicon integrated optical sensor based on multi-mode interference

Temperature sensing with optical devices is a very promising research field because of many attractive features common to all-optical sensing schemes. All-silicon integrated sensors have many interesting features from their inherent low processing cost to integrability with signal-processing electronics. In this paper, we present a novel approach to temperature sensing with optoelectronic devices which relies on the usage of bare silicon as the transducing material. The device is composed by a single mode input waveguide, an MMI region where the higher order modes are allowed to propagate and two output waveguides. The refractive index variation in the MMI section due to temperature shifts induces different phase velocities of the propagating modes. Analytical calculations are presented together with BPM simulations aimed to the maximization of the sensitivity of the sensor.