Advanced Porous Silicon Photonic Devices for Biosensing Applications

Abstract

Ring resonator and photonic crystal nanobeam devices are demonstrated in porous silicon waveguide and Bloch surface wave films for on-chip biosensing applications. These advanced photonic structures combine the strong light-matter interaction and multilayer versatility intrinsic to porous silicon films with the high quality factor and low modal volume advantages of resonant photonic devices. The porous morphology promotes direct light-matter interaction of confined optical modes with small target molecules that infiltrate the pores. A novel Bloch surface and sub-surface wave porous silicon multilayer film is demonstrated that allows size selective detection of both large and small molecules by supporting both a surface wave mode and one or more guided modes within the multilayer porous silicon film. By facilitating large molecule detection via the Bloch surface wave, this porous silicon structure overcomes major limitations in the size and molecular weight of species that porous silicon sensors are capable of sensitively detecting. In addition, porous silicon ring resonators and nanobeams are demonstrated for the first time and exhibit a 40-fold sensitivity improvement over nonporous silicon-on-insulator ring resonator and nanobeam sensors. Finally, the first experimental realization of a Bloch surface wave ring resonator is reported and is demonstrated in the porous silicon material system. This new structure may open the door to new opportunities in integrated optics; a molecular sensing application is demonstrated as a first example. Overall, the ability to create multilayer porous silicon films and incorporate on-chip photonic devices allows the development of novel photonic resonator families that show particular promise for future lab-on-a-chip and sensor array devices.