Nanophotonic structures for waveguide couplers and polarizers

Abstract

We review our recent work on nanophotonic waveguide devices. We shall discuss structures which efficiently couple light into a plasmonic slot waveguide, and the use of a hyperuniform disordered photonic bandgap structure to make a highly compact waveguide polarizers. Nanoscale photonic integration was successfully used to demonstrate the monolithic integration of 850 photonic components on a CMOS microprocessor with over 70 million transistors [1]. This large disparity in the number of photonic and electronic devices on the same chip arises because of the limitation in how small conventional silicon photonic devices can be made. In this talk we shall describe our recent work in two different approaches to enable the integration of smaller photonic devices. One approach for smaller photonic devices is to exploit the guiding of light at metal-dielectric interfaces from surface plasmon-polariton (SPP) modes. Plasmonic devices not only offer the advantage of smaller size, but in the case of optical modulators they can also provide higher energy efficiency and high speed operation [2]. One important challenge for plasmonic devices on silicon chips is how to couple light efficiently into the plasmonic device. We shall present some of the different designs of nanophotonic couplers to couple light efficiently from a conventional silicon waveguide to a plasmonic slot waveguide [3]. Another approach to make smaller photonic devices is to exploit the photonic bandgap of nanophotonic structures for highly compact resonators, filters or polarizers. Unlike convention photonic crystals which require high precision in the periodicity of the photonic lattice, photonic bandgaps from hyperuniform disordered structures [4] are more tolerant to fabrication errors. We shall describe a waveguide polarizer with over 30 dB extinction ratio over a 98nm optical bandwidth that occupies a short length of 8 µm (including the waveguide tapers) based on a hyperuniform disordered photonic bandgap structure [4].