Design of an optical nanoantenna with focusing subwavelength grating couplers and metallic reflector

In the development of integrated large-scale optical phase array, compact optical nanoantennas are needed. For high resolution arrays, the nanoantenna footprint and the separation between them should be as small as possible to reduce the number of interference orders in the far field [1]. In the development of this nanoantennas in our InP membrane on Silicon (IMOS) platform [2], we use deeply etch focusing grating to reduce the size [3]. In order to increase the optical power emitting up, we add a metal reflector of Silver underneath the semiconductor with a small buffer of 50 nm of 푆푖푂2. This metal layer will also works as a thermal heater, which will change the optical properties of the semiconductor changing the direction of the upcoming light. The last element to be add is a subwavelength ridge which reduces the unwanted Fresnel reflections by reducing the refractive index contrast [3].