Integrated Optical Gas Sensors on Silicon-on-Insulator Platform

Abstract

Abstract:We demonstrate highly sensitive micro-optical hydrogen and ethanol sensors on SOI microring resonators (MRR) using chemical coatings sensitive to the corresponding gases. Hydrogen concentrations below the lower explosion limit and ethanol vapor concentration below 100ppm are detected. ©2010 Optical Society of AmericaOCIS codes: (000.0000) General; (000.0000) IntroductionApplications such as environmental pollution monitoring, industrial process & explosion control, and forensic breath analysis heavily rely on gas sensors.The Optical gas sensing route is becoming attractive compared to other competitive technologies, such as electrical gas sensors, for various reasons. Robustness, multiplexing of sensor arrays, safety, remote sensing and low power consumption are among the interesting features about the optical sensors [1].Most of the optical sensors reported to date have been based on optical fibers. These sensors have enabled multiplexed multipoint and remote gas sensing. However, fiber optical sensors are not convenient for integration. On the other hand, inexpensive and compact gas sensors which can elegantly fit to a wide range of applications have been of a significant interest in the gas sensing community. The possibility to miniaturize gas sensors opens a way to a chip level implementation, integration with other vital functionalities, and mass fabrication. This way, fairly cheap, highly compact and multi -purpose gas sensors can be available. However, the implementation of optical gas sensors at integrated level has been challenging mainly due to the technological limitations.Optical structures fabricated on the silicon on insulator (SOI) platform have recently been proving to be promising for a wide range of integrated optical applications [2]. These structures have been demonstrated with submicron scale features and can be realized on a very small area on a chip owing to the high index contrast between the waveguides and the surrounding claddings. Moreover, the compatibility of the SOI devices to CMOS fabrication tools and the promise of inexpensive mass fabrication makes them highly attractive. Owing to these facts, the research on SOI optical structures is recently extending beyond the telecom to other applications such as optical bio-molecule and gas sensing.We demonstrate two highly sensitive gas sensors, namely, a hydrogen sensor and an ethanol sensor based on SOI microring resonators.

Modelling and simulation of a thermally induced optical transparency in a dual micro-ring resonator

“…Hilfiker et al [ 13 ] explores the technique of optical gas detection using absorption spectroscopy based on the Beer–Lambert Law. Another study [ 15 ] examines the use of a tungsten oxide-coated micro-ring resonator as a hydrogen sensor.…”