径向偏振光瞳滤波共焦拉曼光谱显微系统研制

针对共焦拉曼系统空间分辨力提升的迫切需求,研制了一套径向偏振光瞳滤波共焦拉曼光谱显微系统(RPCRS)。该系统利用径向偏振光发生器(S波片)将激光器发出的线偏振光转换为径向偏振光;然后,利用光瞳滤波器对径向偏振光进行调制,从而压缩拉曼激发光斑;最后,利用共焦针孔消除焦点外位置的拉曼散射光,进一步提升共焦拉曼显微系统的空间分辨力。该系统具有较高的空间分辨力和横向灵敏度。以周期性刻线和标准台阶作为测试样品进行实验,实验结果表明,RPCRS的空间分辨力可以达到240 nm,横向灵敏度相比普通拉曼共焦系统提升了46.5%,测量标准不确定度为18.87 nm。该系统可用于高空间分辨共焦拉曼成像。     

用于纳秒级窄脉冲工作的大功率半导体激光器模块

介绍了一种将脉冲半导体激光器发射应用系统中脉冲整形电路、驱动电路、激光器保护电路、激光器集成封装成一个激光器模块的方式。当激光器工作于纳秒级窄脉冲状态下时,激光器封装引腿所产生电抗会使得耦合进激光器的脉冲波形劣化,能量损失。为得到上升时间短,波形半宽窄,峰值功率大的光输出,改进激光器管芯的结构并采用混合光电子集成的方式将驱动电路和激光器管芯封装在一个模块内,使得窄脉冲电信号高效地耦合进半导体管芯。分析验证了改进后的激光器模块的各项输出参数均得到改善。同等条件下,改进后的模块在光脉冲宽度为4.5ns时,峰值功率比单独封装激光器提高6倍多。此激光器模块可以得到宽度7ns左右,峰值光功率176W的光脉冲输出。测试了该模块在脉冲宽度为7ns左右的U-P曲线。     

应用单一超窄线宽激光器的多气体检测系统设计

应用超窄线宽半导体激光器的波长扫描和光谱调制技术,设计了一种高精度多组分气体实时在线检测系统.系统采用单一超窄线宽可调谐半导体激光器作为光源,设计了新型串联式气室结构减小横向空间、增加光程长,并通过三角波信号对光源光谱进行调制;结合时分复用和空分复用技术,利用超窄线宽激光的特性实现了CO,CO2,CH4多组分气体浓度的...     

纳秒声光调Q光纤激光器产生超连续谱

根据现有生成超连续谱方案的不足,搭建了一台全光纤结构的纳秒声光调Q激光器。该激光器中心波长为1 064.3nm,重复频率为20kHz,脉冲宽度为250ns;经过一级放大得到的输出功率为13.02 W。将信号光耦合进自行研制的高功率模场适配器(MFA),得到了10.7 W的信号光输出,耦合效率高达82.2%。将MFA与光子晶体光纤(PCF)熔接,得到了平均功率为5.43 W的超连续谱输出,光谱覆盖为900~1 700nm。由于实验采用的声光调制器(AOM)脉宽较宽,导致泵浦光峰值较低,非线性效应较弱,未能使超连续谱向可见光展宽。因此,建议采用较窄脉宽的AOM作为调Q元件来实现高峰值功率输出,以改善纳秒脉冲PCF产生的超连续谱特性。     

基于轴棱锥用主被动方式产生短 脉冲高功率近似无衍射光

利用轴棱锥构成的Bessel-Gauss谐振腔,首次由灯泵Nd:YAG调Q激光器主动式直接输出纳秒高功率近似无衍射Bessel-Gauss光脉冲。应用衍射理论给出的Bessel-Gauss场分布模型对结果进行分析,数值模拟和实验结果基本吻合。同时利用带抗共振环(ARR)的Nd:YAG调Q激光器输出的高稳定纳秒高斯脉冲,通过Axicon的光束整形,由被动方式获得近似理想的纳秒无衍射零阶Bessel光。利用胶片扫描法记录了光强分布的精细结构,测定得出无衍射光的中心光斑半径约为90μm,峰值功率密度高达2.3×10⁹ W/cm²。分析比较了主动和被动方式产生纳秒无衍射光的特性和优缺点。     

中国国产窄线宽光纤激光器取得重点突破

近日,FM Photonics宣布拥有完全自主知识产品的、属于中国人自己的"窄线宽光纤激光器"研制成功,并已实现规模化生产,填补了中国在该领域的空白。窄线宽光纤激光器是指激光以腔     

重复频率锁定的783 nm飞秒光纤激光器研制

设计并搭建了重复频率长时精确锁定的783 nm飞秒光纤激光器。该激光器基于全保偏非线性干涉环镜(NALM),实现掺铒光纤振荡器锁模脉冲输出,由与脉冲分离器级联的环境稳定掺铒光纤双级放大器进行功率放大,实现了平均功率1.30 W、脉冲宽度130 fs、重复频率77.1 MHz、1560 nm脉冲输出;通过周期极化铌酸锂(PPLN)光学晶体倍频,获得了平均功率为0.52 W、脉冲宽度为140 fs、783 nm脉冲输出。通过重复频率监测及锁相环技术,进一步将掺铒光纤振荡器的重复频率溯源至参考铷原子钟,12 h内频率抖动峰-峰值为5 mHz、标准偏差为1.2 mHz。该激光器系统具有稳定性高、集成度高、体积小的特点。     

全固态589nm激光器及其钠导星激发亮度

研制了一台LD侧面泵浦和腔内和频结构的小型全固态589nm激光器,报道了利用该激光器激发钠导星亮度的实验研究结果。通过数值模拟分析并设计了谐振腔腔长、晶体位置等,使其具有体积小、转换效率高等特点。研制了一套时域匹配电源用于补偿两路激光脉冲的时间差。对分束镜双侧进行特殊镀膜,获得了相应的线偏振光并提高了转换效率和热稳定性。采用插入标准具、特殊镀膜等技术抑制了1 338nm谱线的振荡。最后设计了相应的发射望远镜和接收系统用于钠激光导星的观测。测试结果表明,该激光器的输出功率大于8 W,重复频率为5kHz,线宽小于3.5GHz,对应808nm泵浦功率的转换效率达到2%。在长春市内天光背景下,冬季实验激发的导星亮度可达10.0等。     

采空区沉降监测的BOTDR光纤传感技术

基于布里渊光时域反射计(BOTDR)设计了应变检测系统,用于采空区的沉降监测。该系统使用窄线宽激光器和高消光比光调制器产生脉冲光,并通过相干探测和微波扫频获取高信噪比的原始信号,最后采用洛仑兹曲线拟合算法解调出布里渊频移分布曲线。实验中,选用10.19 km的传感光纤,在末端3.9 m长度光纤上施加不同应变,以模拟采空区的沉降,解调的频移误差为2.1 MHz,对应应变测量误差为48.7με,该系统能为采空区的沉降监测提供一种方案和技术。     

声光调QCO_2激光器

为满足激光测距、环境探测、空间通讯及激光与物质相互作用机理研究等领域应用要求,研制了声光调Q CO2激光器.针对影响声光调Q CO2激光器输出的各种因素,利用调Q脉冲激光器速率方程对该激光器输出的主要技术参数进行了理论分析和计算,提出了声光调Q CO2激光器优化设计的方法,并进行了验证实验.激光器脉冲重复频率为1 Hz～50 kHz, 在1 kHz运转时获得的输出激光脉冲宽度为180 ns,峰值功率为4 062 W,与理论计算基本一致.结果证明:通过声光晶体(AO)的优选及谐振腔的合理设计,可实现小型CO2激光器的高重频、窄脉宽,高峰值功率输出,并可通过光栅选线的设计方式和TTL信号控制实现此类激光器的波长调谐和编码输出.     

基于少模光纤的轴对称偏振光束的产生

首先介绍了轴对称偏振光束的基本概念以及特性,然后以少模光纤为模式转换器,通过旋转偏振控制器上光纤挤压器的旋钮对光纤中间部分施加压力,同时配合旋转光纤挤压器,以实验的方式获得了不同模式的轴对称偏振光束。通过调节偏振控制器以及输入光束和光纤的离轴状态,分别得到了径向偏振TM01模式,角向偏振TE01模式,奇数混合偏振HEodd21模式,偶数混合偏振HEeven21模式,以及线偏振HE11模式五种光纤所激发的模式。同时,还通过干涉实验中叉形光栅结构证明了相位奇点的存在。     

基于渡越-切伦科夫辐射原理太赫兹横向场频率特性的实验研究

基于渡越-切伦科夫辐射原理,单色飞秒激光脉冲聚焦到空气中形成等离子体进而辐射出径向偏振太赫兹波,径向偏振太赫兹波经过紧聚焦后在焦点处产生太赫兹波横向偏振分量。为了有效调控太赫兹横向分量的频率分布和振幅特性,首先,通过理论分析太赫兹横向场分量在外加电压下的分布规律,给出不同角度的外加电压对太赫兹横向场频率强度的影响。然后,采用对等离子体施加外部电场的方法,得到一个最佳的纵向电场角度产生高强度太赫兹横向偏振分量。对发展太赫兹波特性的基础研究以及太赫兹技术的应用具有重要的参考意义。     

Probing highly confined optical fields in the focal region of a high NA parabolic mirror with subwavelength spatial resolution

Parabolic mirrors with a high numerical aperture can be conveniently used to produce highly confined optical fields in the focal region. Furthermore, these fields can have interesting polarization behaviour due to the high numerical aperture. In particular, if the mirror is illuminated with a size matched radially polarized or azimuthally polarized doughnut mode, the electric field has in the focal region almost exclusively a longitudinal or a transverse polarization component. Such field distributions are interesting for applications in confocal or near‐field optical microscopy. Here we present experimental results where we have probed some of these field distributions by raster scanning a fine gold tip in nanometer steps through the focal region and detecting the scattered light intensity. The measured intensity patterns are compared with corresponding vector‐field calculations.     

Subnanosecond pulsing of a 3-MV Van de Graaff electron accelerator by means of a passive coaxial pulse shaper

A passive coaxial pulse shaper has been developed which produces a subnanosecond duration pulse with short rise and decay time from a long pulse with short rise time. The mechanical construction of the pulse shaper is a modified coaxial air line T-section. The pulse shaper has been incorporated in the pulsing circuit of a 3-MV Van de Graaff accelerator. The form of the resulting electron beam pulses was monitored both as the charge collected by a coaxial target and as the Cerenkov light emitted by a quartz plate. In both cases sequential sampling techniques were used. The electron beam pulses were found to have rise and decay tiems of approxiamtely 100 ps and a half-width as short as approximately 200 ps could be obtained. An advantage of this method of producing subnanosecond beam pulses is that it does not interfere with normal nanosecond pulsed operation of the Van de Graaff.     

A high-current nanosecond electron accelerator with a semiconductor opening switch

A compact nanosecond electron accelerator with an output energy of up to 4000 keV, a pulsed power of 100–180 MW, a beam current of 0.25–1.1 kA, and a pulse energy of 5–7 J is described. The accelerator operates with a pulse repetition rate of 200 Hz and ensures an average beam power of up to 1 kW. A nanosecond generator with a solid-state switching system, which is based on magnetic stages of pulse compression and a semiconductor opening switch, is used as a supplying device. The design and electric circuit of the accelerator are described, and test results are presented.     

基于双环形旋涡相位调制的多焦点产生

为提高光学显微成像及微粒控制的效率,提出一种通过双环形旋涡相位板对入射光为拉盖尔高斯柱矢量光束进行波前相位调制的多焦点产生方法。通过Debye矢量衍射理论分析了该相位板对焦点区域光强分布的影响。分析表明,经调节内外环旋涡相位拓扑数及内环的半径,可以对焦点区域光强分布进行整形,在焦平面上产生多焦点,而且通过改变入射柱矢量光束的偏振态,可以进一步得到光场由轴向分量为主的多焦点及由横向分量组成的多焦点。通过改变旋涡相位板的拓扑数及光束的参数,可以达到对光斑的数量的控制。这对于捕捉折射率高于周围环境折射率的微粒具有重要的应用价值。     

拉盖尔-高斯光经超表面的聚焦特性

为了研究椭圆偏振拉盖尔-高斯光经超表面的聚焦特性,重点分析了聚焦光场的电场强度以及相位分布特性。利用时域有限差分(FDTD)方法仿真椭圆偏振拉盖尔-高斯光经超表面的聚焦光场。研究表明,椭圆偏振拉盖尔-高斯光经超表面聚焦后会在聚焦光场的纵向分量电场中出现自旋角动量转化为轨道角动量的现象,通过改变超表面的数值孔径大小、拉盖尔-高斯光的偏振类型等参数可以调控涡旋光场形态分布。该现象可应用于光镊、量子加密、光学扳手等技术中。     

NON-LINEAR DYNAMIC BEHAVIOR OF THERMOELASTIC CIRCULAR PLATE WITH VARYING THICKNESS SUBJECTED TO NON- CONSERVATIVE LOADING

The non-linear dynamic behaviors of thermoelastic circular plate with varying thickness subjected to radially uniformly distributed follower forces are considered. Two coupled non-linear differential equations of motion for this problem are derived in terms of the transverse deflection and radial displacement component of the mid-plane of the plate. Using the Kantorovich averaging method, the differential equation of mode shape of the plate is derived, and the eigenvalue problem is solved by using shooting method. The eigencurves for frequencies and critical loads of the circular plate with unmovable simply supported edge and clamped edge are obtained. The effects of the variation of thickness and temperature on the frequencies and critical loads of the thermoelastic circular plate subjected to radially uniformly distributed follower forces are then discussed.     

A nanosecond SOS generator with a peak power of 4 GW

A high-current nanosecond generator with a peak power of up to 4 GW, an output voltage of 0.4–1 MV, a pulse duration of 8–10 ns, and pulse repetition rates of 300 Hz in a continuous mode and up to 1 kHz in the burst mode is described. The average output power at a pulse repetition rate of 1 kHz reaches 30 kW. The generator has an all-solid-state energy-switching system. A semiconductor opening switch on SOS diodes forms output pulses. The electric circuit and design of the generator are described, and the experimental results are presented. A device for eliminating prepulses across the load is proposed. The results of its testing and numerical simulation are presented.