Researchers at the University of Illinois have developed improvements to their innovative photonic integrated circuit (PIC) design, which features three-dimensional subsurface networks of optical components (UIUC ref. no. 2017-212). The paradigm, called "volumetric photonic integrated circuits" (VPIC), addresses the bottleneck of large surface area requirements faced by conventional PICs by embedding the networks vertically within a semiconductor (e.g., porous silicon) material.
The present improvements include a variety of new subsurface components which exhibit low loss and high total efficiency competitive with silicon photonics. Components include high Q microrings; lenses and waveguides for efficient coupling; Mach Zehnder interferometers; loop mirrors; and distributed Bragg reflectors.