Nanopixel Waveguide Polarization Rotator Towards Integrated CRDS Breath Sensor for Self-Lasing Suspension

In the context of an aging global population, breath analysis offers a non-invasive method to assess health.One approach uses Cavity Ring-Down Spectroscopy (CRDS), where an optical amplifier compensates for feedback loop loss.However, the self-lasing phenomenon (arising when coherency is secured at a wavelength other than the sensing light) reduces device sensitivity.To mitigate this, a polarization rotator is introduced in the ring cavity, ensuring amplification benefits only the sensing light.As we develop an integrable CRDS system on a Silicon-On-Insulator (SOI) platform, we demonstrate that a 90 polarization rotation is crucial.SOI nanopixel waveguides with two converters and air holes can achieve an 86 to 94 rotation over a 20-nm wavelength range, with insertion loss manageable by the EDFA.A hole diameter of 70 nm offers a balance between reduced loss and efficient mode conversion, though larger holes may enhance mode confinement, particularly for TE10 and TM00 modes.