Harbin Institute of Technology unveils dual-gas LITES sensor with one QTF

By AI, Created 3:30 PM UTC, May 22, 2026, /AGP/ – A Harbin Institute of Technology team has developed a mixed-frequency heterodyne demodulation system that lets one quartz tuning fork detect methane and acetylene at the same time with low crosstalk. The approach could cut complexity and cost for industrial safety and environmental monitoring sensors.

Why it matters: - The new design points to simpler multi-gas sensors that can run real-time, simultaneous measurements without the hardware burden of separate demodulation chains. - Low-cost, compact gas sensing is important for industrial safety, leak detection, pollution monitoring and harsh-environment applications. - The architecture could help move LITES systems closer to portable field deployment.

What happened: - A team led by Professor Yufei Ma at Harbin Institute of Technology developed a mixed-frequency heterodyne demodulation architecture for dual-gas light-induced thermoelastic spectroscopy, or LITES. - The sensor uses a single quartz tuning fork to detect methane and acetylene at the same time. - The work appears in Light: Advanced Manufacturing. - The DOI is 10.37188/lam.2026.054.

The details: - The mixed-frequency heterodyne demodulation scheme converts photothermal signals at different frequencies to a shared intermediate-frequency carrier. - The approach removes the need for multiple high-frequency reference sources. - The system uses both the fundamental and first overtone vibration modes of one custom-designed QTF. - A three-stage frequency-domain isolation chain reduces crosstalk through fourth-order Butterworth filters, frequency mixing circuits and narrowband lock-in amplification. - Testing showed inter-channel crosstalk below 0.057%. - Both channels delivered concentration linearity with R2 > 0.999. - Maximum nonlinear error reached 1.39% full scale for methane and 1.48% full scale for acetylene. - Average relative system error was 0.95% for methane and 0.93% for acetylene. - With a 300-second integration time, the minimum detection limit was 0.13 ppm for methane and 2.93 ppm for acetylene. - The paper says the architecture simplifies system synchronization and cuts hardware cost.

Between the lines: - The key advance is not just sensitivity. It is the ability to keep simultaneous dual-gas sensing while avoiding the crosstalk and complexity that often limit multiplexed designs. - Using one QTF for two gases suggests a path toward smaller instruments with fewer optical and electrical components. - The results also show that LITES can be adapted for more practical multi-gas monitoring beyond laboratory setups.

What’s next: - The team plans to move the demodulation technology into an application-specific integrated circuit, or ASIC, for miniaturized portable sensors. - The researchers also plan to expand detection to three or more gas species by using higher-order QTF vibration modes and additional laser wavelengths. - Field tests are planned in industrial and environmental settings. - Expected applications include natural gas pipeline monitoring, chemical plant safety and atmospheric environmental protection.

The bottom line: - Harbin Institute of Technology’s mixed-frequency approach shows a cleaner route to true simultaneous multi-gas LITES sensing, with lower crosstalk and less system complexity than conventional multiplexed designs.