Researchers led by Professor Yufei Ma of the National Key Laboratory of Laser Spatial Information at the Harbin Institute of Technology and colleagues have developed an ultra-highly sensitive dual gases detection system based on photoacoustic spectroscopy using a long-wave, high-power, wide-tunable, single-longitudinal-mode solid-state laser. The study was published in Light Science & Applications.
With its broad range of applications in many sectors, photoacoustic spectroscopy (PAS) is a highly sensitive and selective trace gas detection technology. The PAS’s primary component, the laser sources, is essential to the system’s ability to detect. These days, quantum cascade lasers (QCLs) and distributed feedback diode lasers (DFB) are the most often utilized light excitation sources in PAS.
Due to their small cavity length and delicate chip, QCLs typically have hard operating conditions and poor beam quality, while DFB diode lasers typically have output powers in the tens of milliwatts. The limited wavelength tuning range of both source types restricts the detection of several gases with a single laser source.
The solid-state laser self-built in the presented system achieved high optical power (~136 mW) and long output wavelength (~2 μm) while keeping excellent beam quality and avoiding difficult circumstances, in contrast to the laser sources of DFB diode laser and QCL.
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It works well as the PAS’s excitation source because it can provide a strong, steady photoacoustic signal, which is useful for trace gas detection. Additionally, the solid-state laser with a single longitudinal mode offered a broad tuning range of 9.44 nm, enabling the targeting of H2O and NH3 absorption spectral characteristics.
The solid-state laser was utilized as the light source in three different QEPAS systems: (i) an external-cavity system with a custom-made QTF in an off-beam resonant configuration; (ii) a conventional PAS setup using a microphone as an acoustic detector; and (iii) an intra-cavity system with the QTF inside the laser cavity because of its advantage of small size.
The study demonstrates the appealing qualities of solid-state lasers as PAS excitation sources, and the solid-state laser-based intra-cavity QEPAS offers novel approaches to PAS system design.
National Natural Science Foundation of China (Grant No. 62335006, 62022032, 62275065, and 61875047), Key Laboratory of Opto-Electronic Information Acquisition and Manipulation (Anhui University), Ministry of Education (Grant No. OEIAM202202), Fundamental Research Funds for the Central Universities (Grant No. HIT.OCEF.2023011) supported the study.
Journal Reference:
Qiao, S., et al. (2024) Ultra-highly sensitive dual gases detection based on photoacoustic spectroscopy by exploiting a long-wave, high-power, wide-tunable, single-longitudinal-mode solid-state laser. Light Science & Applications. doi.org/10.1038/s41377-024-01459-5