适用于圆筒形增益区的同轴四镜腔的失调分析

采用矩阵光学方法，对适用于可见光的圆筒形增益区同轴四镜腔中的腔镜因倾斜而产生的失调特性进行了分析，给出了相关计算公式。该四镜腔由同轴的一个复曲面全反镜和两个光学玻璃加工的透镜和一个平面输出镜组成。以He-Ne激光器为例，给出了数值计算结果，关键元件复曲面镜的失调对输出的影响较大。这为腔元件的加工以及腔镜的安装调试提供了参考。     

用声光调制器实现的1 W Nd∶YAG单纵模环形激光器

鉴于单向环形腔是目前获得较大功率单纵模激光最有效的方式之一,为使环形腔单向运行,需要在环形腔内插入对正反2个方向的光产生损耗差的光学元件。采用激光二极管泵浦Nd∶YAG晶体,用声光调制器作为光学二极管使环形腔单向运行,实现四镜矩形环形腔单纵模激光器。实验中谐振腔的稳定性由增益介质的热透镜保证,声光调制器给正反2个方向的光提供损耗差,这使得在竞争过程中有较大损耗的光不能运行从而获得单向输出。实验获得了连续功率1 W、光束质量因子M2为1.21 的1.06 m单纵模激光。     

Dual-wavelength, two-crystal, continuous-wave optical parametric oscillator

We report a cw optical parametric oscillator (OPO) in a novel architecture comprising two nonlinear crystals in a single cavity, providing two independently tunable pairs of signal and idler wavelengths. Based on a singly resonant oscillator design, the device permits access to arbitrary signal and idler wavelength combinations within the parametric gain bandwidth and reflectivity of the OPO cavity mirrors. Using two identical 30 mm long MgO:sPPLT crystals in a compact four-mirror ring resonator pumped at 532 nm, we generate two pairs of signal and idler wavelengths with arbitrary tuning across 850-1430 nm, and demonstrate a frequency separation in the resonant signal waves down to 0.55 THz. Moreover, near wavelength-matched condition, coherent energy coupling between the resonant signal waves, results in reduced operation threshold and increased output power. A total output power >2.8 W with peak-to-peak power stability of 16% over 2 h is obtained.     

注入功率比可调控的双泵浦复合腔501 nm青光激光器

为了探究提高500?nm附近激光高准确度应用的理论和技术依据,本文采用双泵浦源复合腔结合非线性和频变换,实现腔内两种波长基频光无增益竞争,可提高基频光输出功率,同时在复合腔内进行多次非线性频率变换,通过调控基频光注入功率比,使腔内光子数配比达到1:1,从而有效提高了光-光转换效率及和频输出功率.对首次建立的理论模型进行...     

两腔级联纠缠增强的理论分析

高纠缠度的纠缠源是实现高保真度量子信息传输与处理的保障,因为受到光学元器件自身性能不完美的限制,通过有效的操控手段来提高光场的纠缠度是十分必要的.连续变量Einstein-Podolsky-Rosen纠缠态光场可以利用工作在阈值以下的非简并光学参量放大器来获得.将两个非简并光学参量放大器级联,可以利用第二个光学腔来操控第一个光学腔输出的纠缠态光场,在一定条件下实现光场的纠缠增强.本文通过理论分析设计出两种光学腔级联的实验系统,其中,纠缠产生装置采用具有三共振结构的半整块驻波腔,输出到目前为止世界上单腔获得两组份纠缠态光场纠缠度的最高值,操控光学腔采用驻波腔或四镜环形腔的结构.详细对比分析了不同结构的操控腔对纠缠增强效果的影响,得出利用不同腔形作为操控腔的最佳实验方案.同时分析了级联腔输出光场的纠缠度随不同物理参量的变化关系,得出进一步优化的最佳实验系统参量,为实验获得更高纠缠度的纠缠态光场提供了依据.     

光纤激光器自混合干涉效应研究

针对光纤激光器自混合干涉传感应用,研究了光纤激光器自混合干涉特性,运用四镜法布里-珀罗腔模型对掺铒线形腔光纤激光器自混合干涉效应进行了理论分析,对不同反馈水平下的自混合干涉信号进行了数值模拟,获得了光反馈条件下光纤激光器输出特性.外腔长度的改变会调制激光器的输出强度,外腔长度变化半个波长,对应一个干涉条纹,弱反馈条件下,由反馈引起的激光器的频率变化可以忽略.设计了基于光纤激光器的自混合干涉实验,实验结果和理论分析相符合.此研究结果为进一步开展光纤激光器的自混合干涉传感应用研究奠定了理论与实验基础.     

Millimeter-wave gyroklystron amplifier experiment using arelativistic electron beam

A fundamental-mode TE₁₁₁° two-cavity intense-beam gyroklystron amplifier experiment, operating at an accelerating voltage of 1 MV, is reported. The two cavities that were tested are designed to serve as bunching cavities for a high-power output cavity. The two-cavity amplifier has demonstrated a linear gain of 15 dB and an unsaturated output power of ~40 kW, with the intracavity gain and power ~4 dB higher. The frequency of the second cavity has been found to track the frequency of the driven cavity over a range of 300 MHz around a center frequency of 35 GHz. Stable amplifier operation was achieved with beam currents as large as 150 A and a velocity pitch ratio of 0.36. The stable operating range was limited by spurious oscillation in the TE₁₁₂° mode. Theoretical calculations indicate that higher gains might be attainable if this mode could be suppressed     

输出功率5.2 W的全固态连续单横模671 nm红光激光器

设计了全固态连续单横模671 nm红光激光器.利用880 nm LD双端端面泵浦Nd:YVO4复合晶体,实现了均匀泵浦并改善了激光晶体热效应;考虑到影响倍频转化效率的各种因素,优化设计了Z字形四镜激光谐振腔,采用I类临界相位匹配晶体LBO作为腔内倍频晶体;当泵浦功率为42.5W时,获得了5.2W的连续单横模671 nm红光输出,光-光转化效率达到12.2％,激光器长期功率稳定性优于±2.5％(1 h).     

Completely solid-state LD-side-pumped Nd:YAlO<Subscript>3</Subscript> CW blue laser with intracavity frequency tripling

We report a completely solid-state continuous-wave (CW) blue laser operating at 447 nm utilizing intracavity frequency tripling of an LD-side-pumped Nd:YAlO₃ (Nd:YAP) laser operating at 1341.4 nm. An LBO crystal with type-I critical phase matching and a KTP crystal with type-II critical phase matching (CTM) were used for the second harmonic generation (SHG) and the third harmonic generation (THG), respectively. In view of the analysis of the cavity stability, a four-mirror folded cavity was designed and the output characteristics were theoretically analyzed. Experimental characteristics obtained were shown to be in agreement with the theoretical analysis. The maximum output power of the 447 nm CW blue laser reached 114 mW, which corresponds to a red-to-blue conversion efficiency of 9%.     

激光陀螺锁区特性的研究

从理论和试验两个方面,研究了四边形腔环行激光陀螺的锁区特性.利用环行腔中背向散射光束具有相干性,导出了环行谐振腔综合背向散射与反射镜、反射镜之间的相对位置的关系.在有两个位移反射镜的四边形谐振腔中,理论上得到了综合背向散射系数与谐振腔腔长具有双波长周期.利用综合背向光强实验及锁区与陀螺工作模数实验分别验证了理论的正确性.试验证实散射光的强度与谐振腔的工作模数存在双模周期性,综合背向散射系数大,陀螺锁区大,反之亦然.     

Research on the phase-locking and beam characteristics of a new axisymmetric-fold-combination CO2 laser

A new type of axisymmetric-fold-combination CO₂ laser, which is constituted by several axisymmetric four-mirror cavities, is studied theoretically in this paper. The mutual energy coupling occurring within the communal discharge region of the unstable resonator to inject seed signals into each sub-resonator is demonstrated by theoretical deduction. The numerical results have proved that phase-locking could be achieved in this cavity, and the beams with phase-locking have both a higher intensity and a smaller light spot than the ones without phase-locking.     

Gain width and rise time studies of pulsed unstable optical parametric oscillators

Gain width and rise time of a pulsed singly resonant unstable optical parametric oscillator have been investigated based on theoretical models of parametric gain and threshold in the spherical wave assumption. A simplified analytic expression for the gain width is derived, which has been illustrated to be of adequate accuracy for the theoretical model. It is demonstrated that the theoretical model and analytic expression are applicable to the plane-parallel resonator when some special values are taken. The gain width and rise time are found to be determined by important parameters, such as cavity physical length, cavity magnification factor, reflectance of the output coupler, input pump peak power, and pump pulse width. PACS 42.60.Da; 42.65.Yj     

Analytical solution to the transient beam loading effects of a superconducting cavity

Transient beam loading is one of the key issues in any high beam current intensity superconducting accelerators, and needs to be carefully investigated. The core problem in the analysis is to obtain the time evolution of effective cavity voltage under transient beam loading. To simplify the problem, the second order ordinary differential equation describing the behavior of the effective cavity voltage is intuitively simplified to a first order one, with the aid of two critical approximations which lack proof of their validity. In this paper, the validity is examined mathematically in some specific cases, resulting in a criterion for the simplification. It is popular to solve the approximate equation for the effective cavity voltage numerically, while this paper shows that it can also be solved analytically under the step function approximation for the driven term. With the analytical solution to the effective cavity voltage, the transient reflected power from the cavity and the energy gain of the central particle in the bunch can also be calculated analytically. The validity of the step function approximation for the driven term is examined by direct evaluations.After that, the analytical results are compared with the numerical ones.     

Kerr lens effects in a folded-cavity four-mirror linear resonator

The Kerr-lens model locking of a folded-cavity four-mirror linear Ti: sapphire laser is simulated by applying the ABCD ray-tracing technique for a Gaussian beam. The intensity dependent Kerr-lens ABCD matrix of the Brewster-plate shaped active medium is derived. A split-step parabolic refractive index model is used. the astigmatism compensation condition is derived from the ABCD ray-tracing. Simulations are carried out for a symmetric resonator and an asymmetric resonator design. Hard-aperture loss mode locking and soft-aperture gain mode locking are discussed. The optimum design parameters (slit position for hard-aperture loss mode locking, pump beam focusing for soft-aperture gain mode locking, gain cavity spacing, gain medium position) for Kerr-lens mode locking are determined.     

关于氦氖激光器声光调制锁模的实验研究

本实验中,将声光调制锁模器放置在氦氖激光器中的谐振腔里,控制谐振腔中的增益,使声波的频率调制与激光器固有频率间隔一致,从而达既可以到锁模的效果,又可以增加增益,减少能量损耗。通过功率计与示波器检测出激光脉宽、脉冲周、纵模间隔等物理量,与理论值进行比较,判断激光锁模实验的效果。本实验使用的氦氖激光器腔长大于1.55m,是双面全反射腔,可以利用激光锁模技术得到纵模进行比较,从而获得单色性好的超短脉冲激光。     

高光束质量、高功率稳定性激光器的设计及实验研究

高光束质量、高功率稳定性激光器在激光加工、激光测量等领域具有广泛的用途.为了实现激光器腔内光斑聚焦同时减少色散和体积,人们常常将曲面反射镜用在激光谐振腔中,但光束倾斜入射到曲面反射镜往往会引起像散,从而导致光斑质量恶化,并降低激光器的性能.另一方面,在高功率激光器或超短脉冲激光器中,激光增益介质热透镜焦距的起伏,是导致激光输出功率波动的主要原因之一.针对激光器的像散和功率波动这两个问题,本文提出了一套简单高效的解决方案,在考虑像散补偿和热透镜效应的基础上,基于传播变换圆理论,首次提出一种可实现高光束质量、高功率稳定性激光器谐振腔的设计方法,并对采用该方法所设计出的超短脉冲激光器进行理论与实验研究.研究结果表明,利用该方法设计的激光谐振腔,两端臂像散能够完全被补偿,实验上实现了基模高斯光束输出;当激光晶体热透镜焦距改变时,该方法所设计出的激光谐振腔内各关键位置光斑半径的变化,显著地小于普通谐振腔,在相同外界条件下,其输出激光功率稳定性明显优于普通激光器.     

Stable mode-locking operation in a Cr:forsterite laser with a five-mirror cavity

The experimental finding of more-stable mode-locking operation in a five-mirror cavity than in a conventional four-mirror cavity for a Cr:forsterite laser [IEEE J. Quantum Electron. 33, 1975 (1997)] was interpreted by ABCD-matrix formalism. Since the optimum cavity configuration operation for mode-locking operation was attainable in the middle of the stable cavity condition, we conclude that one can easily achieve KLM alignment and stable mode locking with a five-mirror cavity.     

近对称谐振腔的变换圆图解分析

 利用传播圆-变换圆图解分析方法，通过对不同结构谐振腔的分析和对比，得出一种宜于推广的自锁模激光谐振腔——近对称谐振腔，其锁模运转易于启动且工作性能比较稳定；通过实验对近对称腔的工作性能进行了验证，并对一种五镜锁模腔进行了分析。五镜腔实质上等价于近对称四镜腔。     

Experimental implementation of a self-tuning control system for decentralised velocity feedback

Simulations have previously shown that, for broadband excitation, adjusting the gain of a local velocity feedback loop to maximise their absorbed power also tends to minimise the kinetic energy of the structure under control. This paper describes an experimental implementation of multiple velocity feedback loops on a flat panel, whose gains can be controlled automatically by an algorithm that maximises their local absorbed power. Taking care to remove excessive phase shift in the control loop allows a stable feedback gain that is high enough to experimentally demonstrate the transition in control action between optimum damping and pinning of the structure. A simple search algorithm is then used to adapt the feedback gains of two control loops to maximise their local absorbed powers, thus demonstrating self-tuning. By measuring the power absorbed by each of these loops and also estimation of the kinetic energy of the plate from velocity measurements for a wide range of the two feedback gains, it is shown that not only does the adaptive algorithm converge to a set of feedback gains that maximise total power absorbed by the two feedback loops, but also that this set of feedback gains is very close to those that minimise the measured kinetic energy of the panel.     

基于XGM的SOA波长变换器噪音特性分析及优化设计

利用动态载流子恢复时间可以精确模拟基于交叉增益调制的SOA全光波长变换器的饱和增益效应,本文将SOA分段ASE噪音功率和分段动态模型结合,得到沿长度分布的ASE噪音功率,并讨论了偏置电流、泵浦光和探测光的波长、功率、SOA长度对消光比和信噪比的影响理论计算结果表明,大的偏置电流有利于提高消光比和信噪比;对于一定的输入波长,相对较大的泵浦光和相对较小的探测光变换效果好;SOA的长度存在最佳值.