Nano-pixel polarization rotator for a photonic integrated breath sensor

Abstract

In response to the global aging population, a photonic-integrated-circuit sensor is investigated for the detection of disease markers within human breath content. The device relies on cavity-ring-down spectroscopy with an amplifying medium and loop feedback to secure sufficient sensitivity down to ppm-order concentrations detection. This configuration, however, might cause unwanted oscillation, and polarization rotation method has been proposed to prevent this issue. We have researched a waveguide-based polarization rotator using nano-pixel. The device consists of two regions: 1) From TE00 mode TE10 modes conversion, and 2) TE10 to TM00 modes conversion. As the intermediary TE10 mode quality is a key to realize polarization rotation performance, the purpose of this study is to realize high quality TE10 by employing mean-squared-error criterion for the waveguide design optimization. Finite-difference time-domain simulation with this method reveals TE10 mode with 1% accuracy that results in a polarization extinction ratio improved from 4.3 to 8.6 dB.