Novel Ge1-xSix-on-Al2O3-Based Rib Optical Waveguide Mid-IR Sensors on SiO2 Platform

In this letter, we present the first proof of Ge
_1-x
Si
_x
-on-Al
₂
O
₃
-based novel rib optical waveguide (WG) for N
₂
O and CO gas detection at 4.5 and 4.67 µm, respectively. We optimize the rib WG structure using theoretical models to achieve high sensitivity, minimal detectable gas concentration, and low propagation loss. The device's sensitivity and minimal detectable concentration of N
₂
O and CO at λ = 4.5 and 4.67 µm, respectively, are excellent. The sensitivity and minimal detectable value (
C
_min
) for N
₂
O (CO) for the optimized device structure are
$1.75 \times {{10}^{-5}}$
ppm
⁻¹
(
$6.8 \times {{10}^{-6}}$
ppm
⁻¹
), and 18.93 ppm (14.97 ppm), respectively. The
C
_min
value demonstrate a significant improvement compared with previously reported findings and international standards. These findings demonstrate that Ge
_1-x
Si
_x
platforms pave the way for the development of high-performance, compact optical WGs for MIR applications.