Quartz Enhanced Photothermal Spectroscopy (QEPTS) is a technique, which enables developing gas sensors characterized by a broadband operational range and superb sensitivity. QEPTS relies on the thermoelastic effect induced by the illumination of the Quartz Tunning Fork (QTF) with a modulated laser radiation, which generates a piezoelectric signal. QTF excitation can occur at any wavelength, which is impossible to observe in e.g. semiconductor detectors. The sub-dollar cost of a QTF delivers simultaneously broadband and sensitive detection capability and significantly reduced costs of the sensor. Furthermore, as in majority of laser-based sensors, the sensitivity of QEPTS-based systems can be easily enhanced by increasing laser-gas interaction path length. This is typically realized by using multipass cells (MPCs), which significantly increase the sensor’s complexity and decrease its robustness. Instead of using MPCs, an Antiresonant Hollow-Core Fiber (ARHCF), designed for light transmission in more than one spectral band can be used as a long gas absorption cell, leading to the increase in the sensor’s performance while keeping its design simple. Here, we present a sensor utilizing a combination of an ARHCF-based absorption cell and the QEPTS. In the developed system the gas-filled ARHCF substitutes an MPC. The spectroscopic signal analysis relies on the use of a simple QTF with a resonance frequency of 32.744 kHz connected with a self-made, low-noise amplifier and an addition of a wavelength modulation spectroscopy – based signal retrieval scheme for sensor’s performance enhancement. The sensor enables simultaneous detection of acetylene and methane at parts-per-million by volume level sensitivity, targeting their absorption lines in the near- and mid-infrared. The results confirm excellent suitability of the ARHCF-aided QEPTS sensors for being employed as a versatile gas detectors.
This research was funded by Narodowe Centrum Nauki (NCN), grant number UMO-2018/30/Q/ST3/00809.
Waveform sampling LiDAR is a hot topic in LiDAR technique due to its high precision geodesy and multi-layer target detection ability. Especially, the LiDAR systems applying streak tube have encouraging application due to their special properties about high-sensitivity and full waveform sampling ability. This paper describes a kind of LiDAR system applying the full waveform sampling stripe principle array. Basing on the planar fitting of square object, the elevation error of points cloud got from flight experiment is analyzed. The statistical properties of elevation error are got.
A high-repetition-rate, high-peak-power burst-mode laser for laser-based measurement applications is presented by using a master oscillator power amplifier structure. An laser diode arrays (LDA) side-pumped Nd:YAG acousto-optical (A-O) Q-switched laser serves as the master oscillator. Under pulsed pumping, pulse trains with 2-25 pulses are obtained when the repetition rate changes from 10 kHz to 100 kHz. The maximum pulse burst energy of 31.2 mJ is achieved in the A-O Q-switched pulse burst laser oscillator at 10 kHz. Two LDA side pumped Nd:YAG modules are employed in the amplification stage. After the amplification, the pulse burst energy at 10 kHz reaches ~170 mJ with a single pulse energy of 85.2 mJ and a pulse width of 14.5 ns, generating a peak power of 6.1 MW. At 100 kHz, the total burst energy reaches 220 mJ with a single pulse energy of 8.8 mJ in the pulse burst laser system.
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