A compact mid-infrared dual-gas CH 4 /C 2 H 6 sensor using a single interband cascade laser and custom electronics Weilin Ye a, b , Chuantao Zheng* a,c , Frank K. Tittel a , Nancy P. Sanchez d , Aleksander K. Gluszek a, e , Arkadiusz J. Hudzikowski a, e , Minhan Lou a , Lei Dong f , Robert J. Griffin d a Department of Electrical and Computer Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA, b College of Engineering, Shantou University, 254 Daxue Road, Shantou 515063, P. R. China, c State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, P.R.China, d Department of Civil and Environmental Engineering, Rice University, 6100 Main Street, Houston, TX 77005, USA, e Laser & Fiber Electronics Group, Faculty of Electronics, Wroclaw University of Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland, f State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, P.R.China *Corresponding author. zhengchuantao@jlu.edu.cn ABSTRACT A compact mid-infrared (MIR) dual-gas sensor system was demonstrated for simultaneous detection of methane (CH 4 ) and ethane (C 2 H 6 ) using a single continuous-wave (CW) interband cascade laser (ICL) based on tunable laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy (WMS). Ultracompact custom electronics were developed, including a laser current driver, a temperature controller and a lock-in amplifier. These custom electronics reduce the size and weight of the sensor system as compared with a previous version based on commercial electronics. A multipass gas cell with an effective optical length of 54.6 m was employed to enhance the absorption signal. A 3337 nm ICL was capable of targeting a C 2 H 6 absorption line at 2996.88 cm -1 and a CH 4 line at 2999.06 cm -1 . Dual-gas detection was realized by scanning both the CH 4 and C 2 H 6 absorption lines. Based on an Allan deviation analysis, the 1 σ minimum detection limit (MDL) was 17.4 ppbv for CH 4 and 2.4 ppbv for C 2 H 6 with an integration time of 4.3 s. TDLAS based sensor measurements for both indoor and outdoor mixing ratios of CH 4 and C 2 H 6 were conducted. The reported single ICL based dual-gas sensor system has the advantages of reduced size and cost without influencing the mid- infrared sensor detection sensitivity, selectivity and reliability. Keywords: Mid-infrared, Interband cascade laser, Dual-gas detection, Wavelength modulation 1. INTRODUCTION Methane (CH 4 ) is a main contributor to the greenhouse effect and a safety hazard in the production of chemicals. Hence the monitoring of CH 4 concentration levels is critical in urban or rural areas [1, 2]. Ethane (C 2 H 6 ) [3, 4] is the second- largest component of natural gas after CH 4 , and is mainly used in the chemical industry. Simultaneous detection of C 2 H 6 and CH 4 is an effective method to discriminate the CH 4 origin between thermogenic (e.g. natural gas production) and biogenic sources (e.g. landfills, wetlands) . Therefore, a dual-gas sensor was developed to perform the detection of CH 4 at an atmospheric concentration of ~ two parts-per-million by volume (ppmv) and C 2 H 6 of several parts-per-billion by volume (ppbv) to tens of ppbv. Infrared laser spectroscopy [5-9] is advantageous compared to other detection methods in terms of cost, size and no sample pretreatment. Furthermore, TDLAS can achieve high-precision sensing capabilities and fast response. TDLAS [10-12] enables direct concentration measurements and has proven to be an excellent tool for trace gas detection in Quantum Sensing and Nano Electronics and Photonics XIV, edited by Manijeh Razeghi, Proc. of SPIE Vol. 10111, 1011134 · © 2017 SPIE · CCC code: 0277-786X/17/$18 doi: 10.1117/12.2250941 Proc. of SPIE Vol. 10111 1011134-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 02/07/2017 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx