Trace gases can be detected quickly and accurately with light, but current optical methods can only detect gases over a narrow range of wavelengths. Wei et al. developed a cost-effective optical gas detector that can detect trace gases over a wide bandwidth.

The team found a single cheap quartz tuning fork can detect simulated trace gas signals as efficiently as several expensive photodetectors working in conjunction together. The fork was sensitive to signals over the entire range, indicating it can be used over a wide range of wavelengths.

“The main result reported in our paper is the demonstration of the flat spectral response of quartz tuning forks employed as photodetectors for infrared radiation [a wavelength range typically used to detect distinct gas molecules],” author Vincenzo Spagnolo said.

To create the device, the team analyzed how quartz tuning forks absorbed infrared radiation and converted it to electric signals using the thermoelastic effect. The team simulated several devices using finite-element methods before choosing and building an optimal photodetector design.

The quartz tuning fork demonstrated a “spectrally flat” responsivity of about 2.2 kilovolts per watt when used to detect lasers at different infrared wavelengths.

The author plans to continue optimizing the geometry of the quartz photodetector to achieve maximal response.

“This step is crucial to reduce the efforts required to achieve a proper alignment maximizing the tuning fork response,” Spagnolo said. “In this way, we plan to obtain a reliable, rugged photodetector for spectroscopic applications.”

Source: “High and flat spectral responsivity of quartz tuning fork used as infrared photodetector in tunable diode laser spectroscopy,” by Tingting Wei, Andrea Zifarelli, Stefano Dello Russo, Hongpeng Wu, Giansergio Menduni, Pietro Patimisco, Angelo Sampaolo, Vincenzo Spagnolo, and Lei Dong, Applied Physics Reviews (2021). The article can be accessed at