Baru -baru ini, Pusat Russell untuk Sains Lightwave Advanced Institut Optik dan Mekanik Fine Institute, Universiti Sains dan Teknologi Pertubuhan Bangsa -Bangsa Bersatu, Institut Pengajian Lanjutan, Institut Sains Sains, dan IFIBO} Jurnal optik teratas antarabangsa "Optica", dan buat kali pertama mencapai kecekapan tinggi, kesetiaan tinggi dan kesucian fleksibel tunggal yang tinggi, beratus-ratus femtoseconds, 2 {11} Hasil ini bukan sahaja memberikan penyelesaian yang berkesan untuk kekurangan denyutan ultrafast pertengahan inframerah dalam penghantaran, tetapi juga meletakkan asas bagi pengembangan aplikasi laser pertengahan inframerah
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%.
Para penguji juga membandingkan skim penghantaran dengan laluan optik spatial panjang yang sama dan serat fluorida pepejal . hasilnya menunjukkan bahawa semasa penghantaran denyutan ultrafast dalam serat fluorida pepejal, kesan nonlinear terlalu kuat, menyebabkan pucat yang jelas, Serat dalam penghantaran kuasa tinggi puncak pertengahan inframerah ultrafast denyutan . Eksperimen mencapai kecekapan tinggi, kesetiaan tinggi dan kesucian tinggi mod mid-inframerah laser fleksibel,
Keputusan penyelidikan yang berkaitan telah diterbitkan dalam jurnal teratas laser dan optoelektronik, Optica, dengan tajuk "penghantaran fleksibel jalur lebar, 100 fs pertengahan inframerah-inframerah dalam jalur penyerapan air menggunakan fiberus fotonik dan comely fiberus dan comely fiberus. Teknologi, dan Li Zeqing, pelajar kedoktoran Institut Optik dan Mekanik yang baik, adalah pengarang bersama, dan Huang Jiapeng, Jiang Xin dan Pang Meng dari Pusat Russell adalah pengarang bersama-sama .
Rajah 1. Persediaan Eksperimen dan Keputusan . (a) Laluan optik eksperimen . kanta, lensa CAF2 plano-convex; HWP, plat separuh gelombang; QWP, plat gelombang suku; FM, Bend Mirror; FTIR, Fourier transform spektrometer inframerah; AC, autokorrelator . (b) imej SEM struktur serat . (c) spektrum kerugian yang diukur menggunakan kaedah pemangkasan, kawasan yang teduh mewakili ketidakpastian pengukuran (oren, paksi kiri), dan keluk penyebaran yang dikira (} PCF . (e) Menggunakan bahan znse 30 mm dan 5 mm, output nadi dengan lebar nadi yang hampir berubah-ubah 98 fs dicapai .
Rajah 2. Perbandingan mod penghantaran yang berbeza . (a) Spektrum penyerapan normal wap air . (b) output laser langsung (kelabu) dan spektrum penghantaran dalam laluan optik spatial (ungu) (merah) . Bahagian kanan menunjukkan spektrum yang diperbesarkan dalam julat 2.7-2.8 μm . (c) generasi soliton Raman dalam serat fluorida pepejal .
