The demand for greenhouse gas measurement has increased dramatically due to global warming. A 1.57-μm airborne double-pulse integrated-path differential absorption (IPDA) light detection and ranging (LIDAR) system for CO₂ concentration measurement was developed. The airborne field experiments of this IPDA LIDAR system were conducted at a flight altitude of approximately 7 km, and the weak echo signal of the ocean area was successfully received. The matched filter algorithm was applied to the retrieval of the weak signals, and the pulse integration method was used to improve the signal-to-noise ratio. The inversion results of the CO₂ column-averaged dry-air mixing ratio (XCO₂) by the scheme of averaging after log (AVD) and the scheme of averaging signals before log were compared. The AVD method was found more effective for the experiment. The long-term correlation between the changing trends of XCO₂ retrieved by the IPDA LIDAR system and CO₂ dry-air volume mixing ratio measured by the in-situ instrument reached 92%. In the steady stage of the open area (30 km away from the coast), which is almost unaffected by the residential areas, the mean value of XCO₂ retrieved by the IPDA LIDAR system was 414.69 ppm, with the standard deviation being 1.02 ppm. Compared with the CO₂ concentration measured by the in-situ instrument in the same period, bias was 1.30 ppm. The flight path passed across the ocean, residential, and mountainous areas, with the mean value of XCO₂ of the three areas being 419.35, 429.29, and 422.52 ppm, respectively. The gradient of the residential and ocean areas was 9.94 ppm, with that of the residential and mountainous areas being 6.77 ppm. Obvious gradients were found in different regions.

A narrow-linewidth 972.26 nm laser with a 4.5 pm spectral linewidth was generated from a BBO optical parametric oscillator using a volume Bragg grating as the cavity end mirror, pumped by a 532.23 nm single-longitudinal-mode laser at a 1 kHz repetition rate. The system achieved 0.94 W maximum output power with <2.4 ns pulse duration, yielding 23.5% signal conversion efficiency. Extracavity second-harmonic generation produced 0.41 W of 486.13 nm blue light with a 2.0 pm linewidth and 43.6% conversion efficiency. The wavelength could be tuned over 0.4 nm by varying the grating temperature between 12.6°C and 52.6°C. © 2026 Chinese Optics Letters

In this paper, we report a diode side-pumped injection-seeded single-frequency Tm,Ho:YLF laser, which operated at lasing threshold and emitted at 2051.2 nm. The assistance of Fabry-Pérot (FP) etalons to seed injection via mode selection was investigated. An acouto-optic Q-swiched output of 6.7 mJ was achieved at 5 Hz. A temporal pulse duration of 310 ns with spectral linewidth of 2.0 MHz and frequency stability of 0.8 MHz rms was detected. The beam profile was a high quality Guassian TEM₀₀ mode with M²_x/y = ~ 1.15/1.14. The application of this 2 µm laser as light source in the wind detection coherent Lidar system was verified.