Wavelength-Tunable Heterogeneous Integrated MEMS-VCSEL for Gas Detection

Optical gas detectors have the advantages of high sensitivity and fast response, which are widely used in industrial production and daily life. However, the detection of different gases needs to match the corresponding absorption light source, which limits the universality and miniaturization of optical gas detectors. This study proposes a wavelength-tunable heterogeneous integrated microelectromechanical (MEMS) vertical-cavity surface-emitting laser (VCSEL) to achieve detection of multiple gases. We demonstrated a wavelength tuning range exceeding 31 nm and a side mode suppression ratio (SMSR) exceeding 45 dB in this MEMS-VCSEL. This exquisite structure couples the concentration and refractive index of gas in the cavity with the output wavelength by changing its optical phase and is high-sensitive to optical cavity length. We theoretically calculate the non-linear detection characteristics of MEMS-VCSEL and obtain a maximum sensitivity of 140 nm/refractive index unit (RIU) and a maximum figure of merit (FOM) of 780 RIU<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup>. In addition, the absolute errors of gas concentration in sweep-frequency detection are lower than 0.3%, which has been reduced by 35% compared to single-frequency detection. This MEMS-VCSEL will provide more possibilities for developing next-generation high-integration and non-selective gas detectors, which have flexible applications in gas detection under different specific atmospheres.