Silicon substrate-integrated hollow waveguide for miniaturized optical gas sensing
Shaonan Zheng, Hong Cai, Linfang Xu, Nanxi Li, Zhonghua Gu, Yao Zhang, Weiguo Chen, Yanyan Zhou, Qingxin Zhang, Lennon Y. T. Lee
Abstract
Gas sensors have a wide variety of applications. Among various existing gas sensing technologies, optical gas sensors have outstanding advantages. The development of the Internet of Things and consumer electronics has put stringent requirements on miniaturized gas sensing technology. Here, we demonstrate a chip-scale silicon substrate-integrated hollow waveguide (Si-iHWG) to serve as an optical channel and gas cell in an optical gas sensor. It is fabricated through silicon wafer etching and wafer bonding. The Si-iHWG chip is further assembled with an off-chip light source and detector to build a fully functional compact nondispersive infrared (NDIR) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>CO</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> sensor. The chip size is <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:mn>10</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>mm</mml:mi> <mml:mo>×</mml:mo> <mml:mn>9</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>mm</mml:mi> </mml:mrow> </mml:math> , and the dimension of the sensor excluding the microcontroller board is <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:mn>50</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>mm</mml:mi> <mml:mo>×</mml:mo> <mml:mn>25</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>mm</mml:mi> <mml:mo>×</mml:mo> <mml:mn>16</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>mm</mml:mi> </mml:mrow> </mml:math> . This chip solution with compactness, versatility, robustness, and low cost provides a cost-effective platform for miniaturized optical sensing applications ranging from air quality monitoring to consumer electronics.