A 23.75-GHz frequency comb with two low-finesse filtering cavities in series for high resolution spectroscopy

A laser frequency comb with several tens GHz level is demonstrated,based on a Yb-doped femtosecond fiber laser and two low-finesse Fabry-Perot cavities（FPCs） in series.The original 250-MHz mode-line-spacing of the source comb is filtered to 4.75 GHz and 23.75 GHz,respectively.According to the multi-beam interferences theory of FPC,the side-mode suppression rate of FPC schemes is in good agreement with our own theoretical results from 27 dB of a single FPC to43 dB of paired FPCs.To maintain long-term stable operation and determine the absolute frequency mode number in the23.75-GHz comb,the Pound-Drever-Hall（PDH） locking technology is utilized.Such stable tens GHz frequency combs have important applications in calibrating astronomical spectrographs with high resolution.

Pulse collapse and blue-shifted enhanced supercontinuum in a photonic crystal fiber

The blue-shifted supercontinuum generation in a photonic crystal fiber pumped by high peak power femtosecond pulses with a wavelength located in the anomalous dispersion region is investigated experimentally and numerically.The formation of a blue-shifted enhanced supercontinuum due to the pulse collapse is demonstrated.The process of the pulse collapse is measured by using the grating-eliminated no-nonsense observation of ultrafast incident laser light e-fields technique（GRENOUILLE）.Numerical simulations in spectral and temporal domains are conducted.The data from the numerical simulations are in good agreement with the experimental results.Our experimental results and numerical simulations show that pulse collapse is the determining factor in the generation of a blue-shifted supercontinuum.

Design of a Solid-Core Large-Mode-Area Bragg Fiber

We report the design and simulation results of a solid-core Bragg fiber with 3-bilayer periodic cladding. The simulation results present single mode bandgap guidance, a large effective area of -400 μm2 around 1.08 μm, a very low bend loss of 0.038dB/m at 1.08μm even under tight bend radius （R = 4cm）, and excellent beam quality. The results indicate that the proposed fiber could be a competitive solution for high-power fiber laser applications.

Frequency-stabilized Yb：fiber comb with a tapered single-mode fiber

We demonstrate a stable Yb：fiber frequency comb with supercontinuum generation by using a specially designed tapered single-mode fiber, in which a spectrum spanning from 500 nm to 1500 nm is produced. The carrier-envelope offset signal of the Yb：fiber comb is measured with a signal-to-noise ratio of more than 40 dB and a linewidth narrower than 120 kHz. The repetition rate and carrier-envelope offset signals are simultaneously phase locked to a microwave reference frequency.

腔道肿瘤光动力诊疗内窥技术的发展及临床应用现状

光动力疗法是一种利用激光、光敏剂发生光化学反应从而特异性杀灭肿瘤细胞的药械联合疗法。治疗的柔性光纤可随人体自然腔道的弯曲而弯曲,通过内窥镜活检通道,光纤能够到达腔内近距离照射肿瘤部位。内窥镜辅助光动力疗法因具有显著的局部疗效和微创治疗优势而被广泛应用于腔道恶性肿瘤的治疗中。本文介绍了光动力治疗肿瘤疾病的内窥镜技术的发展,提出了在实现术前诊断、术中可视、视场统一及诊疗一体等目标中存在的技术问题,并汇总了解决方案。本文概述了光动力诊疗内窥技术在腔道肿瘤诊疗中的临床应用现状,以期为光动力治疗的精准化发展提供参考。