Author Affiliations
Abstract
1 College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China
2 School of Information and Communications, National University of Defense Technology, Wuhan 430035, China
3 Nanhu Laser Laboratory, National University of Defense Technology, Changsha 410073, China
4 Hunan Provincial Key Laboratory of High Energy Laser Technology, National University of Defense Technology, Changsha 410073, China
High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demonstrated. The active polarization control technology based on the root-mean-square propagation (RMS-prop) algorithm is employed to guarantee a linearly polarized output from the system. A maximum output power of 402.3 W at a repetition rate of 80 MHz is realized with a polarization extinction ratio (PER) of > 11.4 dB. In addition, the reliable operation of the system is verified by examining the stability and noise properties of the amplified laser. The M2 factor of the laser beam at the highest output power is measured to be less than 1.15, indicating a diffraction-limited beam quality. Finally, the amplified laser pulse is temporally compressed to 755 fs with a highest average power of 273.8 W. This is the first time, to the best of our knowledge, that the active polarization control technology was introduced into the high-power ultrafast fiber amplifier.
active polarization control root-mean-square propagation algorithm linearly polarized laser chirped pulse amplification femtosecond laser fiber laser Chinese Optics Letters
2024, 22(4): 041403
Author Affiliations
Abstract
College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China.
An all-fiber Mamyshev oscillator with a single amplification arm is experimentally demonstrated to achieve high-energy and high-average-power ultrafast pulse output, with the initiating of an external seed pulse. In the high-energy operation, a maximum single-pulse energy of 153 nJ is achieved at a repetition rate of 9.77 MHz. After compression with a pair of diffraction gratings, a measured pulse width of 73 fs with a record energy of 122.1 nJ and a peak power of 1.7 MW is obtained. In the high-average-power operation, up to 5th harmonic mode locking of the oscillator is realized via slightly adjusting the output coupling ratio and the cavity length. The achieved maximum output power is 3.4 W at a repetition rate of 44.08 MHz, while the corresponding pulse width is compressed to around ~100 fs. Meanwhile, the system is verified to be operated reliability in both high-energy and -average-power operation regimes through assessing its short- and long-term stabilities. To the best of our knowledge, these are the highest records in pulse energy and average power delivered from a single all-fiber ultrafast laser oscillator with picosecond/femtosecond pulse duration. It is believed that even higher-energy and -average-power ultrafast laser can be realized with the proposed laser scheme through further increasing the core diameter of the all-fiber cavity, providing promising sources for advanced fabrication, biomedical imaging, laser micromachining, and other practical applications, as well as an unprecedented platform for exploring undiscovered nonlinear dynamics.
Ultrafast Science
2023, 3(1): 0016
1 中国医学科学院药用植物研究所, 北京 100193
2 北京城市学院生物医药学部, 北京 100094
忍冬属中药材种类多、 产量大, 外观性状特征相似, 区分较为困难。 采用傅里叶变换红外光谱对来源于忍冬属的忍冬(金银花)、 红腺忍冬、 灰毡毛忍冬、 黄褐毛忍冬4种中药材进行测定, 红外光谱扫描范围为4 000～400 cm-1, 得到图谱后进行图谱解析; 采用谱带较密集的指纹区(1 800～400 cm-1)计算红外光谱图相似系数和二阶导数谱, 同时结合SMICA(簇类独立软模法)聚类分析法对红外指纹图谱进行分类和异同点比较。 结果表明, 4种忍冬属中药材红外光谱整体峰形相似, 谱峰位置和峰高都比较接近, 在1 629～1 635、 1 376～1 384、 1 265～1 282、 1 152～1 158、 1 050～1 051、 814～816、 611～614和534～537 cm-1附近均有吸收, 但忍冬中1 731 cm-1CO伸缩振动吸收峰最明显, 仅灰毡毛忍冬与忍冬显示出1 105和1 103 cm-1C—O的伸缩振动吸收峰。 红腺忍冬与灰毡毛忍冬1 317 cm-1 CH的弯曲振动吸收峰最明显, 黄褐毛忍冬1 075 cm-1处糖醇类物质的C—OH伸缩振动特征峰最明显。 相似系数结果表明4种中药材间存在一定差异, 其中红腺忍冬与黄褐毛忍冬差异最大, 相似系数为0.94。 二阶导数光谱中, 4种中药材在1 700～1 300和971～780 cm-1波段差异明显。 采用Assure ID软件以药材吸收波数为变量进行聚类分析, 红腺忍冬与黄褐毛忍冬的类间距最大, 为6.86, 进一步表明红腺忍冬与黄褐毛忍冬差异最大。 聚类模型中, 4种中药材的识别率和拒绝率最高值为100%, 最低值达99%; 类模型图中, 不同基原药材两两分开, 表明红外光谱结合SIMCA聚类分析能够鉴别忍冬属4种中药材; 取已知基原的样品对聚类分析模型进行验证, 均被正确识别。 因此, 红外光谱与聚类分析法相结合可以快速、 无损鉴别忍冬属4种中药材, 为忍冬属中药的基原鉴别提供了一种科学有效的方法。
红外光谱法 聚类分析法 忍冬属 中药 Infrared spectroscopy Cluster analysis Lonicera japonicar Traditional chinese medicine 光谱学与光谱分析
2023, 43(11): 3518
Author Affiliations
Abstract
1 College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, China
2 Nanhu Laser Laboratory, National University of Defense Technology, Changsha, China
3 Hunan Provincial Key Laboratory of High Energy Laser Technology, National University of Defense Technology, Changsha, China
A high-power all polarization-maintaining (PM) chirped pulse amplification (CPA) system operating in the 2.0 μm range is experimentally demonstrated. Large mode area (LMA) thulium-doped fiber (TDF) with a core/cladding diameter of 25/400 μm is employed to construct the main amplifier. Through dedicated coiling and cooling of the LMA-TDF to manage the loss of the higher order mode and thermal effect, a maximum average power of 314 W with a slope efficiency of 52% and polarization extinction ratio of 20 dB is realized. The pulse duration is compressed to 283 fs with a grating pair, corresponding to a calculated peak power of 10.8 MW, considering the compression efficiency of 88% and the estimated Strehl ratio of 89%. Moreover, through characterizing the noise properties of the laser, an integrated relative intensity noise of 0.11% at 100 Hz-1 MHz is obtained at the maximum output power, whereas the laser timing jitter is degraded by the final amplifier from 318 to 410 fs at an integration frequency of 5 kHz to 1 MHz, owing to the self-phase modulation effect-induced spectrum broadening. The root-mean-square of long-term power fluctuation is tested to be 0.6%, verifying the good stability of the laser operation. To the best of our knowledge, this is the highest average power of an ultrafast laser realized from an all-PM-fiber TDF-CPA system ever reported.
chirped pulse amplification high average power thulium-doped fiber laser ultrafast laser High Power Laser Science and Engineering
2023, 11(6): 06000e73
红外与激光工程
2023, 52(6): 20220869
Author Affiliations
Abstract
College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha, China
An all-fiber high-power linearly polarized chirped pulse amplification (CPA) system is experimentally demonstrated. Through stretching the pulse duration to a full width of approximately 2 ns with two cascaded chirped fiber Bragg gratings (CFBGs), a maximum average output power of 612 W is achieved from a high-gain Yb-doped fiber that has a core diameter of 20 μm with a slope efficiency of approximately 68% at the repetition rate of 80 MHz. At the maximum output power, the polarization degree is 92.5% and the M2 factor of the output beam quality is approximately 1.29; the slight performance degradations are attributed to the thermal effects in the main amplifier. By optimizing the B-integral of the amplifier and finely adjusting the higher-order dispersion of one of the CFBGs, the pulse width is compressed to 863 fs at the highest power with a compression efficiency of 72%, corresponding to a maximum compressed average power of 440.6 W, single pulse energy of 5.5 μJ and peak power of about 4.67 MW. To the best of our knowledge, this is the highest average power of a femtosecond laser directly generated from an all-fiber linearly polarized CPA system.
chirped pulse amplification femtosecond laser fiber laser high-power laser ultrafast laser High Power Laser Science and Engineering
2023, 11(2): 02000e25
光子学报
2021, 50(10): 1014002
