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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Terahertz Differential Absorption Spectroscopy Using Multi-Furcated Nd:YAG Microchip Laser for Gas Sensing
摘要： We demonstrate a frequency-domain differential absorption spectroscopy in the terahertz (THz) range for gas sensing applications. Our system is based on an injection-seeded THz-wave parametric generator driven by a multi-furcated Nd:YAG microchip laser. Within a single excitation cycle of the laser, the is-TPG generates up to three narrowband THz-wave pulses that are separated from each other in time by 78 μs and in frequency by 11 GHz, which is due to the spatial hole burning effect in the laser cavity. These pulses can be directly used to measure differential absorption signals, and first and second derivative spectra of target gas molecules without measuring reference spectra.
关键词： Nd:YAG microchip laser,gas sensing,differential absorption spectroscopy,THz-wave parametric generator,terahertz
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Temperature and Pumping Beam Radius Influence on Yb:YAG/Cr:YAG Microchip Laser Output
摘要： Miniature high peak power laser systems based on the microchip geometry are promising radiation sources for many applications, like micromanufacturing, remote sensing, data storage, LIBS, etc. The suitability and excellent performance of Yb:YAG/Cr:YAG micro-lasers were reported recently. This study follows our previous experiments and it is focused on investigation of the temperature and pumping beam radius influence on the output parameters of the longitudinally diode-pumped passively Q-switched Yb:YAG/Cr:YAG microchip laser. The goal was to reach as high as possible output energy for given pumping power. The tested microchip laser was based on monolith crystal (diameter 3 mm) which combines in one piece an active laser part (Yb:YAG crystal, 10 at.% Yb/Y, 3 mm long) and saturable absorber (Cr:YAG crystal, 1.36 mm long, initial transmission 90% @ 1.03 mm). The laser resonator pump mirror (HT for pump radiation, HR for generated radiation) was directly deposited on the Yb:YAG monolith part. The output coupler with reflection 55% @ 1.03 mm was placed on the Cr:YAG part. The microchip laser was placed in the temperature controlled cupreous holder inside vacuum chamber of the liquid nitrogen cryostat. For longitudinal pumping of Yb:YAG part, a fibre coupled (core diameter 400 mm, NA=0.22) laser diode was used. The laser diode was operating in pulsed regime (repetition rate 20 Hz, pulse length 3 ms, pumping power amplitude 33.6 W, operating wavelength 933 nm). Seven various pumping optics offering pumping beam waist radius wpmp (at 1/e2 of beam intensity) from 0.27 up to 1.05 mm were tested. The pulse duration, pulse energy, pulse build-up time, pulses repetition rate, and output beam divergence were measured in dependence on microchip temperature in range from 80 up to 350 K. It was found, that the pumping beam radius does not significantly influence on the pulse duration which was 1.5 ± 0.5 ns (FWHM). The single Q-switched pulse energy was increasing with the pumping beam radius up to wpmp=0.87 mm. The output energy was also possible to maximize by temperature tuning. The highest generated single Q-switched pulse energy (2.41 mJ) was obtained for pumping beam radius 0.87 mm at temperature 140 K for given pumping power. The corresponding peak power was 1.67 MW @ 1030 nm. The results showed that the temperature and pumping beam radius optimization can significantly improve the parameters of Q-switched pulses generated by Yb:YAG/Cr:YAG microchip laser.
关键词： Q-switched pulses,temperature influence,output energy,Yb:YAG/Cr:YAG microchip laser,pumping beam radius
更新于2025-09-12 10:27:22
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High-order cylindrical vector beams with tunable topological charge up to 14 directly generated from a microchip laser with high beam quality and high efficiency
摘要： Large topological charge optical vortex beams carrying orbital angular momentum have potential applications on optical trapping, optical communication with high capacity, quantum information processing. However, the beam quality is degraded in vortex beams generated with spiral phase plates or resonator mirrors with defect spots and optical conversion efficiency in solid-state lasers is sacrificed by controlling the loss of resonator. It is a big challenge for generating high beam quality, high-order cylindrical vector beams with large topological charge in compact solid-state lasers. Here, high-order cylindrical vector beams [Laguerre-Gaussian (LG) modes with zero degree and order of l, LG0,l] with tunable topological charges up to 14 have been generated in an annular beam pumped Yb:YAG microchip laser by manipulating the pump power-dependent population inversion distribution. Efficient performance with optical efficiency of 17.5% has been achieved. The output power is 1.36 W for a vector-vortex laser with 14 topological charges. The pump power dependent wavelength tunable and dual-wavelength laser oscillation in vector-vortex beams has been observed by controlling the reabsorption loss at 1030 nm. Wavelength tunable, dual-wavelength (1030 and 1050 nm) laser oscillation has been achieved for vector-vortex beams with topological charges of 8, 9, and 10. The laser beam quality factor M2 close to the theoretical value (l + 1) has been achieved for LG0,l vector-vortex beams with tunable topological charges up to 14. This work provides a new effective method for generating large topological charge high-order cylindrical vector beams in solid-state microchip lasers with high efficiency and high beam quality.
关键词： orbital angular momentum,cylindrical vector beams,topological charge,Yb:YAG microchip laser,optical vortex beams
更新于2025-09-11 14:15:04