Ultra-Low Loss, Chip-Based Hollow-Core Waveguide Using High-Contrast Grating

Abstract : The goal of this program is to develop a chip-scale, integrated photonic platform with fiber-like losses for optical delay applications. The ability to generate long optical delays with low intrinsic loss is useful for a wide range of high precision military applications and systems including: high time-bandwidth product analog optical signal processors and delay lines for wideband RF systems, optical buffers for all-optical routing networks, and ultra-stable optical interferometers for sensing applications, e.g. rotation sensors. We report a completely new concept of chip-scale hollow-core waveguide (HCW) which eliminates dispersion and nonlinearity in typical waveguide core. We demonstrated a new waveguiding design consisting of two parallel silicon-on-insulator wafers, each containing a single layer of high-contrast subwavelength grating (HCG) to reflect light in-between. The optical confinement without any physical boundary is created by variation of HCG dimensions and demonstrated for the first time in a planar HCW with a record low loss of 0.37 dB/em. Two-dimensional light confinement in are demonstrated for both straight and curved waveguides. The unique waveguide geometry not only adds new elements into the waveguiding theory, but also will make possible costeffective manufacturing of integrated optics for chip-scale gas/fluidic sensor, athermal photonic delays lines, and lab-on-a-chip applications.