Recently, the Russell Center for Advanced Lightwave Science of Hangzhou Institute of Optics and Fine Mechanics, the United Nations University of Science and Technology Hangzhou Institute for Advanced Studies, the Shanghai Institute of Optics and Precision Mechanics of the Chinese Academy of Sciences, and Ifibo (Ningbo) Optoelectronics Technology Co., Ltd. published their latest research results V mezinárodním nejvyšším optickém časopise "Optica" a poprvé dosáhl vysoce efektivní, vysoce věrné a vysoké čistoty s jedním režimem flexibilní přenos téměř wattové úrovně, stovky femtosekundy, 2 . 8 μm pásma v polovině infračervených pulsů v Pulses Pulses PULS. Tento výsledek poskytuje nejen efektivní řešení nedostatků ultrarychlých pulzů v přenosu, ale také stanoví základ pro rozšíření laserových aplikací s polovinou infračervených laseru
High-power mid-infrared ultrafast broadband light sources have important applications in advanced spectroscopy, material fine processing, medical surgery, and remote sensing. The limitations of laser transmission have hindered the further expansion of mid-infrared laser applications. In traditional transmission methods, the absorption of various gas molecules in the spatial optical path causes deformation of the output light spot and deterioration of pulse quality. Solid mid-infrared optical fiber has serious nonlinear accumulation, which causes serious distortion of the output time-frequency signal. To solve this problem, the research team used a self-made single-hole eight-ring structure Hollow-core PCF (length 5 m) to transmit mid-infrared ultrafast pulses. Thanks to the advantages of low transmission loss, low nonlinear effect accumulation and support for rapid vacuum extraction of Hollow-core PCF, the team not only solved the problems caused by traditional transmission methods, but also successfully achieved efficient transmission with an overall efficiency of >70%.
During the experiment, the experimenters used a self-built mid-infrared pulse fiber laser as the light source and a 5 m long Hollow-core PCF as the transmission medium. The two ends of the Hollow-core PCF were fixed in the air chamber so that the Hollow-core PCF could be evacuated using a vacuum pump. After the vacuum was drawn (the entire extraction process took less than 1 minute, and the gas pressure was drawn to ~10 mbar), the team successfully achieved an overall laser efficiency of > 70%, a Gaussian spot output that was close to the diffraction limit, and the entire system showed excellent stability. In addition, the spectral shape of the output in the frequency domain was basically consistent with the input. In the time domain, due to the small amount of waveguide dispersion of the hollow-core PCF (-2.04 fs2/mm @ 2.8 μm), the pulse width was widened from the input 117 fs to 404 fs. Subsequently, the experimenters added Ge and ZnSe positive dispersion materials to compensate for the negative dispersion introduced by the hollow-core PCF, coupling lens and air chamber window, and obtained an output with a pulse width of 98 fs (close to the transformation limit pulse width of 96 fs), with a peak power of 170 kW. In addition, the experimenters also used the autocorrelation trace to estimate that the output fundamental mode energy accounted for >95%.
Experimentátoři také porovnávali přenosové schéma s prostorovou optickou cestou stejné délky a pevnými jádrovými fluoridovými vlákny . Výsledky ukazují, že při přenosu ultrarychlých pulsů v pevných jádrech fluoridových vláknech je příliš silné, což je příliš silné účinky, které jsou v tilovaném účinku. crystal fibers in the transmission of high-peak power mid-infrared ultrafast pulses. The experiment achieved high-efficiency, high-fidelity and high-single-mode purity mid-infrared laser flexible transmission technology, laying a good foundation for the application of broadband mid-infrared ultrafast light sources in spectroscopy, infrared countermeasures and remote sensing.
The relevant research results were published in the top journal of lasers and optoelectronics, Optica, with the title "Flexible delivery of broadband, 100 fs mid-infrared pulses in the water-absorption band using hollow-core photonic crystal fiber". Lin Wei, a joint doctoral student of Shanghai Institute of Optics and Fine Mechanics and University of Science and Technology of China Hangzhou Institute of Advanced Technologie a Li Zeqing, doktorský student Šanghajského institutu optiky a jemné mechaniky, jsou spolupravějící autoři a Huang Jiapeng, Jiang Xin a Pang Meng z Russell Center jsou autoři .}
Obrázek 1. Experimentální nastavení a výsledky . (a) Experimentální optická cesta . objektivu, potažená CAF2 Plano-Convex Lens; HWP, napůl vlnová deska; Qwp, čtvrtletní deska; FM, ohybové zrcadlo; FTIR, infračervený spektrometr Fourier Transform; AC, autocorrelator. (b) SEM image of the fiber structure. (c) Loss spectrum measured using the truncation method, the shaded area represents the measurement uncertainty (orange, left axis), and the calculated dispersion curve (blue, right axis). (d) Output power through a 5-meter-long Hollow-Core PCF . (e) Použití 30 mm Znse a 5 mm GE materiály, byl dosažen pulzní výstup s téměř transformační šířkou pulsu 98 fs .
Figure 2. Comparison of different transmission modes. (a) Normalized absorption spectrum of water vapor. (b) Direct laser output (gray) and transmission spectrum in the spatial optical path (purple), transmission spectrum of hollow-core PCF in air (green), and transmission spectrum of hollow-core PCF in vacuum (red). The right side shows the enlarged spectrum in the range of 2.7-2.8 μm. (c) Raman soliton generation in a solid-core fluoride fiber. The FTIR spectrum is on the left and the autocorrelation trace is on the right.
