Proposal of novel strip high-mesa waveguide for infrared absorption sensing

Here we propose novel waveguide of strip high-mesa waveguide for infrared absorption sensing for the first time. The higher optical portion out of the waveguide (we define this portion as “Γ_air”) is the key feature for the infrared absorption, and the novel waveguide realize extremely high Γ_air of 76% at the wavelength λ=1550 nm theoretically.

1. Introduction

High-mesa waveguide is attractive because this waveguide has a potential of, not only very small radius of curvature, detecting function in infrared absorption spectroscopy especially for breath-sensing [1]–[6] as a certain portion of the optical field may profile out of the waveguide depending on the waveguide width [3]. One of the critical issues for the high-mesa is their mesa-height (approximately ), which arises a difficulty in the etching-process, and may lead to relatively high propagation loss due to the scattering cased by the sidewall roughness formed during the etching process [3]. To overcome this problem, we newly propose strip high-mesa waveguide in this paper. Although the estimated total mesa-height counts up to approximately , the simulated results of the proposed novel waveguide show extremely high optical portion out of the waveguide (we define this portion as ) of 76% at the wavelength .