Abstract

A high-Q Mach–Zehnder interferometer (MZI)-coupled microring is presented for optical sensing with high sensitivity and a large measurement range. By optimizing the length difference between the two arms of the MZI coupler, the MZI-coupled microring with a high-Q factor and high extinction ratio is obtained. In the present example, the Q factor of the designed silicon-nanowire-based microring is as high as $1.8\times {10}^5$ when the silicon nanowire has a propagation loss $L=2\mathrm{dB}∕\mathrm{cm}$. Due to this high-Q factor, the sensitivity for the change $\Delta n$ of the effective refractive index is about ${10}^{-5}–{10}^{-6}$ by measuring the shift of the resonant wavelength. Because of the wavelength dependence of the coupling ratio of the MZI coupler, it is possible to have only one resonant wavelength with a high extinction ratio in a very large wavelength span [i.e., the quasi-free spectral range of the MZI-coupler microring], which offers a very large measurement range covering the refractive index change of gas/liquid samples (e.g., $0⩽\Delta n<0.48$ in the present example).

© 2009 Optical Society of America

Highly sensitive Si nanowire-based optical sensor using a Mach–Zehnder interferometer coupled microring

Jianwei Wang and Daoxin Dai
Opt. Lett. 35(24) 4229-4231 (2010)

Coupling-induced high-sensitivity silicon microring intensity-based sensor

Huaxiang Yi, David S. Citrin, and Zhiping Zhou
J. Opt. Soc. Am. B 28(7) 1611-1615 (2011)

High-sensitivity liquid refractive-index sensor based on a Mach-Zehnder interferometer with a double-slot hybrid plasmonic waveguide

Xu Sun, Daoxin Dai, Lars Thylén, and Lech Wosinski
Opt. Express 23(20) 25688-25699 (2015)

Highly sensitive digital optical sensor based on cascaded high-Q ring-resonators

Daoxin Dai
Opt. Express 17(26) 23817-23822 (2009)

Nested nonconcentric microring resonators with high-Q and large fabrication tolerance

Raktim Haldar, Sandeep Ummethala, Rajat K. Sinha, and Shailendra K. Varshney
J. Opt. Soc. Am. B 38(12) 3743-3753 (2021)