VCSEL-based Gas Sensing

We develop compact sensors using vertical-cavity surface-emitting lasers (VCSELs), based on tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy (WMS), to determine greenhouse gas and air pollutant concentrations.

Jia Chen, "Compact Laser-Spectroscopic Gas Sensors using Vertical-Cavity Surface-Emitting Lasers", ISBN: 978-3-941650-30-5, 2011
J. Chen et al. “VCSEL-based Calibration-free Carbon Monoxide Sensor at 2.3 μm with in-line Reference Cell”, Applied Physics B: Lasers and Optics 102, 381-389
J. Chen, A. Hangauer, R. Strzoda, M. Fleischer, M.-C. Amann, “Low-Level and Ultra-Low Volume Hollow Waveguide Based Carbon Monoxide Sensor.” Opt. Lett. 35, 3577-3579
J. Chen, A. Hangauer, R. Strzoda, M.-C. Amann, “Laser Spectroscopic Oxygen Sensor Using Diffuse Reflector-based Optical Cell and advanced Signal Processing”, Applied Physics B 100, 417-425
J. Chen, A. Hangauer, R. Strzoda, M.-C. Amann, “Tunable diode laser spectroscopy with optimum wavelength scanning”, Applied Physics B 100, 331-339
Lijuan Lan, Jia Chen, Yingchun Wu, Yin Bai, Xiao Bi and Yanfang Li: Self-Calibrated Multiharmonic CO₂ Sensor Using VCSEL for Urban In Situ Measurement. IEEE Transactions on Instrumentation and Measurement 68, 1140 - 1147, 2018

Cavity attenuation phase-shift spectroscopy (CAPS)

Cavity attenuation phase-shift spectroscopy (CAPS) is a low-cost and highly sensitive instrument for trace gas as well as low concentration fine particulate measurement. It measures the gas/particle from the phase-shift of the light wave after long path attenuation inside the low loss cavity through absorption/scattering. In TUM-EI-ESM, models of CAPS have been built in the framework of ray-tracing and PSF (point spread function), and codes are developed to simulate the configuration parameters (light wave, cavity reflectivity, gas absorption, etc.) on the CAPS system, as shown in the lower-left subfigure. A prototype of CAPS has been set up in our lab, as shown in the right subfigure, which integrate the LED drive circuit, APD (Avalanche Photodiodes) and pre-magnification circuit as well as data acquisition. Preliminary results show that the CAPS system progresses well.