Author Affiliations
Abstract
School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 201800, China
A fiber-based source that can be exploited in a stimulated emission depletion (STED) inspired nanolithography setup is presented. Such a source maintains the excitation beam pulse, generates a ring-shaped depletion beam, and automatically realizes dual-beam coaxial alignment that is critical for two beam nanolithography. The mode conversion of the depletion beam is realized by using a customized vortex fiber, which converts the Gaussian beam into a donut-shaped azimuthally polarized beam. The pulse width and repetition frequency of the excitation beam remain unchanged, and its polarization states can be controlled. According to the simulated point spread function of each beam in the focal region, the full width at half-maximum of the effective spot size in STED nanofabrication could decrease to less than 28.6 nm.
nanolithography vortex fiber direct laser writing STED controlled fabrication Chinese Optics Letters
2021, 19(7): 072201
1 中国科学技术大学光学与光学工程系, 安徽 合肥 230026
2 光电对抗测试评估技术重点实验室, 河南 洛阳 471003
利用Mach-Zehnder (M-Z)结构的尾纤型铌酸锂(LiNbO3)电光强度调制器作为主动调Q开关元件,采用974nm半导体激光器作为泵浦源,峰值吸收系数为110 dB/m的掺杂铒光纤作为增益介质,实现了1550 nm波长的全光 纤主动调Q激光器。通过电光强度调制器对腔内损耗进行了周期性调制,实现Q开关作用, 获得了稳定的调Q脉冲输出。通过改变泵浦功率和调制频率研究了脉冲宽度和峰值功率的变化 规律,调制频率在50 Hz～88 kHz内调整时可以得到稳定输出脉冲。调制频率为1 kHz时 获得最窄脉冲宽度246 ns, 峰值功率近5 W。
激光技术 主动调Q Mach-Zehnder电光调制器 多峰现象 laser techniques actively Q-switching Mach-Zehnder electro-optical modulator multi-peak phenomenon
1 安徽大学历史系, 安徽 合肥 230039
2 中国科学院大学科技史与科技考古系, 北京 100049
3 中国社会科学院考古研究所, 北京 100710
4 浙江大学化学系, 浙江 杭州 310027
采用傅里叶变换红外光谱(FTIR)对天然石灰石、 模拟白灰面以及采自陶寺遗址和殷墟遗址的白灰面进行了分析检测, 以探明陶寺和殷墟遗址白灰面所用原料。 结果显示, 人工烧制石灰碳化后所形成的方解石, 其ν2/ν4比值高达6.31, 明显高于天然石灰石中的方解石, 从而表明人工烧制石灰碳化所形成的方解石较之天然石灰石中的方解石具有较高的晶体无序度; 随着研磨程度的增加, 天然石灰石中的方解石和人工烧制石灰碳化形成的方解石, 其ν2和ν4值逐渐减小, 人工烧制石灰碳化形成方解石的ν2-ν4特征趋势线斜率较高, 从而为考古出土人工烧制石灰的判定提供了一种简便、 有效的方法。 根据此判别方法, 陶寺和殷墟遗址的白灰面很可能是采用人工烧制石灰所制备的, 表明中国古代先民在距今4300多年的新石器时代晚期已掌握了石灰烧制技术。
白灰面 人工烧制石灰 天然石灰石 红外光谱 Lime powders Man-made lime Natural limestone Infrared spectrum
中国科学技术大学 物理学院，安徽 合肥 230026
针对基于非线性偏振旋转(NPR)原理的被动锁模光纤激光器稳定性差和不能自行进入锁模状态的问题，本文设计了自动锁模电路,用于对激光器进行实时调控以获得稳定的锁模输出。该项设计利用高速光电探测器(PD)将NPR被动锁模光纤激光器输出的光信号转化为电脉冲信号，经过线性放大、整形处理后输出至单片机进行计数；单片机根据快速锁模判定算法判断该激光器的输出状态，并自动反馈调节加装在光纤激光器上的电控偏振控制器(PC)，从而实现激光器的锁模稳定状态输出。实验结果表明，对于重复频率为6.238 MHz的NPR被动锁模激光器，自动锁模电路能够在6 ms内检测到失锁状态，在最长10.24 s内自动搜索达到稳定锁模工作状态。对于重复频率在16 MHz以下的NPR被动锁模激光器，自动锁模电路都能够快速地实现自行启动或将启动后因故失锁的状态调节回锁模状态，达到预先的设计要求，具有结构简单、成本低、功耗低及性能稳定等优点。
光纤激光器 被动锁模 电控偏振控制器 自动锁模电路 非线性偏振旋转 fiber laser passive mode locking electronic polarization controller automatic mode-lock circuit Nonlinear Polarization Rotation(NPR) 光学 精密工程
2013, 21(12): 2994
Author Affiliations
Abstract
Department of Optics and Optical Engineering, University of Science and Technology of China, Hefei 230026, China
A nanosecond square pulse fiber laser based on the nonlinear amplifying loop mirror (NALM) is numerically analyzed by the nonlinear Schr¨odinger equation. The fiber cavity with a NALM has a tendency to provide pulse shaping effect with nonlinearity increasing in the NALM, and the nanosecond square pulse is generated by the pulse shaping effect. The numerical results show that the stable square pulse can be obtained when the parameters of the NALM are chosen appropriately. The generated square pulses have flat top and no internal structure.
光纤激光器 纳秒方波脉冲 非线性放大环镜 脉冲整形 140.3538 Lasers, pulsed 060.2320 Fiber optics amplifiers and oscillators 060.3510 Lasers, fiber 140.4050 Mode-locked lasers Chinese Optics Letters
2011, 9(9): 091405
Author Affiliations
Abstract
Institute of Photonics, Department of Physics, University of Science and Technology of China, Hefei 230026, China
We present a flat-top laser beam generation scheme using coherent beam combining of hexagonally arranged Gaussian lasers. To produce a beam with a flat-top profile, we optimize the amplitude and phase of each unit laser using the least-square method. Simulation results show that with 13 unit lasers, a beam with the flatness of less than 1% in the optimizing region can be achieved. The main lobe contains over 95% of the total power. The scheme requires no external beam shaping element and has the potential to be designed for high-power applications.
光束整形 相干合束 平顶光束 衍射光学 140.3298 Laser beam combining 140.3300 Laser beam shaping 050.1970 Diffractive optics Chinese Optics Letters
2010, 8(1): 45
