Low loss hollow-core waveguide on a silicon substrate

Abstract

Optical-fiber-based, hollow-core waveguides (HCWs) have opened up many new applications in laser surgery, gas sensors, and non-linear optics. Chip-scale HCWs are desirable because they are compact, light-weight and can be integrated with other devices into systems-on-a-chip. However, their progress has been hindered by the lack of a low loss waveguide architecture. Here, a completely new waveguiding concept is demonstrated using two planar, parallel, silicon-on-insulator wafers with high-contrast subwavelength gratings to refl ect light in-between. We report a record low optical loss of 0.37 dB/cm for a 9- μm waveguide, mode-matched to a single mode fi ber. Two-dimensional light confi nement is experimentally realized without sidewalls in the HCWs, which is promising for ultrafast sensing response with nearly instantaneous fl ow of gases or fl uids. This unique waveguide geometry establishes an entirely new scheme for low-cost chip-scale sensor arrays and lab-on-a-chip applications.