角锥棱镜激光谐振腔的基本特性

 分析了角锥棱镜对光束的相位变换作用，带二面角误差的角锥棱镜可等效于6块光楔的组合，其楔角的大小和方向由二面角误差决定。对在腔内往返传输的光线在镜面上的位置进行了分析，结果表明：3个二面角误差相同且不为零的角锥棱镜构成的谐振腔为约束非稳腔。用Fox-Li迭代法数值模拟得到了不同棱镜二面角误差情况下的谐振模式。模拟结果表明：圆形镜腔情况下基本振荡模式接近于TEM₀₃模的拉盖尔高斯光束；当3个二面角误差不相同时，模式中各个区域的强度分布不对称。采用3个二面角误差基本接近且绝对值较小的棱镜可以提高光束质量。     

Study on the possibilities of controlling the laser output beam properties by an intracavity deformable mirror

The possibilities of controlling the laser beam properties by a deformable mirror introduced into the laser optical cavity were studied theoretically and experimentally. The experiments were performed under conditions of an industrial high power transverse flow cw CO₂ laser operating with a stable resonator of a folded configuration. A deformable bimorph mirror of a surface profile controlled by the voltage applied to the mirror electrodes is implemented to the laser system as a back cavity mirror or as a one of the inner folding mirrors. The near-and far-field characteristics of the laser beam versus the resonator configuration controlled by the changes of the focal length of the deformable mirror are discussed in the paper. The analysis reveals that the resonator with an inner deformable mirror is much more sensitive to the mirror curvature variations than the resonator in which the deformable mirror is used as a back cavity mirror. The presented results show that dynamic and controllable changes in the resonator properties result in the controlled modification and optimisation of the laser output power and spatial parameters of the laser radiation.     

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。     

Flat amplitude multiwavelength Brillouin–Raman random fiber laser with a half-open cavity

In this paper, we experimentally demonstrate a novel configuration of multiwavelength Brillouin–Raman random fiber laser (MBRRFL) utilizing a half-open cavity. The laser resonator is formed by fiber loop mirror at the Brillouin pump (BP) side and random distributed Rayleigh backscattering in a 10 km dispersion compensating fiber. As a result, we are able to obtain a flat amplitude bandwidth of 16.8 nm from 1,550.0 to 1,566.8 nm built-in 210 uniform Brillouin Stokes lines with 0.08 nm spacing and an average OSNR of 13.5 dB. We also studied the influence of BP power and wavelength on the MBRRFL’s performance. Furthermore, comparing with the open cavity configuration, the discrepancies in power level and linewidth between neighboring channels are overcome by using the half-open cavity.     

失调多腔镜型环形谐振腔共轭光轴位置精度分析

为了详细分析由多个反射镜构成的谐振腔内的闭合光轴(共轭光轴)的特性以及存在条件, 首先从光束传输坐标变换的角度, 分析了由多个平面镜所构成的谐振腔的共轭光轴存在条件, 得出了奇数平面镜谐振腔仅当平面镜间具有高精度的相同垂直度时才存在闭合光轴, 而偶数平面镜谐振腔总是存在闭合光轴的结论, 并给出了腔共轭轴随腔镜方向失调而产生的角度变化关系. 然后从矩阵光学的角度分析包含球面镜的谐振腔的共轭光轴在腔镜间传输时的方向变换问题, 具体分析了由两个平面镜和一个球面镜构成的三角形环形谐振腔的闭合共轭光轴存在的问题. 结果表明, 当不同的镜子出现角度偏差时, 腔内仍然存在闭合的共轭光轴, 并给出了对应的腔轴变化以及新谐振面的位置及方向. 由此表明由于球面镜的加入降低了谐振腔共轭轴存在性对平面镜间高精度平行度的要求, 为基于高品质光学无源腔的光谱测量技术的高精度装调工作提供了理论指导.     

Widely tunable linear-cavity multiwavelength fiber laser with distributed Brillouin scattering

We demonstrate a multiple wavelength Brillouin/erbium fiber laser in a linear cavity configuration.The laser cavity is made up of a fiber loop mirror on one end of the resonator and a virtual mirror generated from the distributed stimulated Brillouin scattering effect on the other end.Due to the weak reflectivity provided by the virtual mirror,self-lasing cavity modes are completely suppressed from the laser cavity.At Brillouin pump and 1480-nm pump powers of 2 and 130 mW,respectively,11 channels of the demonstrated laser with an average total power of 7.13 dBm can freely be tuned over a span of 37-nm wavelength from 1530 to 1567 nm.     

角锥棱镜腔激光二极管抽运被动调Q激光器

为了提高传导冷却条件下激光二极管(LD)侧向抽运被动调Q激光器的光束质量和输出稳定性,采用了两组半圆柱面激光二极管阵列侧向交错抽运两根串接的激光棒,实现了均匀抽运和散热。通过实验分析了横模结构对被动调Q稳定性的影响,设计了角锥棱镜-高斯输出镜非稳腔,在显著提高器件光束质量的同时,明显改善了被动调Q的稳定性,并保证了谐振腔的机械稳定性。在此基础上研制了一台重复频率20 Hz、单脉冲能量64 mJ、脉冲宽度7 ns、稳定性优于±5%、光束发散角0.6 mrad、光-光效率9.1%,且光轴指向稳定的工程实用器件。     

高功率激光器抗失调谐振腔的实验研究

为简化高功率激光器谐振腔结构,提高激光谐振腔的稳定性,增加基模体积,改善光束质量,提出了两种新型激光谐振腔结构,分别是带角隅反射镜的激光谐振腔和直角内圆锥面反射镜激光谐振腔。使用高功率脉冲CO2激光器,研究了这两种激光谐振腔的输出特性和腔镜失调的关系,并结合平凹稳定腔,对三种激光谐振腔的抗失调稳定性进行了对比。实验结果表明,随着全反镜或平面输出镜失调角的增加,角隅腔激光器的单脉冲输出能量下降速度小于直角内圆锥面全反镜腔。两种新型谐振腔全反镜的抗失调稳定性都超过平面输出镜。角隅全反镜谐振腔和直角内圆锥面全反镜谐振腔的抗失调稳定性均大大超过平凹稳定腔。     

Bessel-Gauss resonator with internal amplitude filter

We investigate a conventional resonator configuration, using only spherical curvature optical elements, for the generation of Bessel-Gauss beams. This is achieved through the deployment of a suitable amplitude filter at a Fourier plane create by careful selection of the geometric cavity parameters, such as mirror curvatures and resonator length. We analyze the loss behaviour of the odd and even modes, and show that the lowest Bessel-Gauss mode does not necessarily have the lowest loss.     

A Wavelength and Spectrum Measurement of an Extremely-Short-External-Cavity Laser Diode by Precisely Controlling Slider Flying Height

In this paper we propose a measurement method that uses a laser diode (LD) attached to a flying slider and a semi-transparent rotating disk mirror for an extremely-short-external-cavity configuration. Not only the wavelength, but also the spectrum and the light output are measured at room temperature with the external cavity length, the reflectivities of the LD facets and the external mirror, and the drive current as parameters. We have confirmed wavelength variation as great as 30 nm by changing the external-cavity length for a 1.3-$mUm wavelength laser diode with an antireflection coating on the LD facet facing the external mirror.     

带受激布里渊散射相位共轭镜的Nd:YAG激光器

应用液体中受激布里渊散射相位共轭镜,与普通反射镜一起构成位相共轭谐振腔,得到了能量在10OmJ以上,脉宽在15ns以下的激光脉冲输出。实验测量了各种腔结构参数对输出能量的影响,并用相位板对该腔干扰,测量了其补偿特性。     

Effective mass in quantum effects of radiation pressure

We study the quantum effects of radiation pressure in a high-finesse cavity with a mirror coated on a mechanical resonator. We show that the optomechanical coupling can be described by an effective susceptibility which takes into account every acoustic modes of the resonator and their coupling to the light. At low frequency this effective response is similar to a harmonic response with an effective mass smaller than the total mass of the mirror. For a plano-convex resonator the effective mass is related to the light spot size and becomes very small for small optical waists, thus enhancing the quantum effects of optomechanical coupling.     

200 W双谐振腔组合单向输出准连续绿光激光器

研究了最大平均输出功率达206 W的高功率准连续绿光激光器.利用ABCD定律及高斯光束在腔内的自再现条件,分析了激光晶体热透镜效应及热致双折射效应对谐振腔稳定性和输出光束质量的影响.实验中将两个型号相同的LD侧面泵浦激光模块分别置于一个平-凹V型谐振腔和一个平-凹直腔内,形成两束稳定运转的1 064 nm基频光,经过声光Q开关和倍频晶体后,产生两束倍频光,均到达平面折叠镜,最终由平面折叠镜单向重叠输出.当激光模块的泵浦电流为50 A,声光调Q的重复频率为22.4 kHz时,最大平均输出功率为206 W,最大单脉冲能量为9.2 mJ,脉冲宽度为201 ns,峰值功率为45.8 kW的532 nm绿光输出,倍频效率达到60.2%.激光器2 h工作的功率不稳定度优于2.5%.     

角锥阵列改善固体热容激光器光束质量

 为改善光束远场质量,探索研究了角锥反射器的应用,利用角锥棱镜的准相位共轭特性,将角锥棱镜阵列作为热容激光器的后腔镜,抑制腔内波前畸变,并通过数值模拟计算对角锥阵列的单元边长进行优化设计。实验结果表明:角锥阵列对光束远场质量有明显的改善,当角锥阵列的单元边长为4 mm时,实现光束远场7倍衍射极限输出。     

Experimental analysis of a continuously pumped,repetitively Q-switched Nd/YAG laser

The threshold operation and performance of a high pulse repetition frequency Nd/YAG laser are discussed. A rotating mirror Q-switch was used, and detailed studies of the variation of Q-switched threshold with motor frequency, and of the pulse build-up time with input power have been carried out. The results indicate that the switching angle varies with mirror reflectivity but is practically independent of resonator length. The latter is attributed to thermal lens action in the laser rod modifying the nominally plane parallel resonator configuration thereby leading to a spherical configuration. Under these conditions, the switching angle becomes independent of resonator length, but depends strongly on the induced focal length of the lens (laser rod). The degrading effect on the Q-switched laser performance of the mis-match at the laser rod surfaces is then discussed and finally the conditions for achieving maximum energy output in a single pulse are derived and experimentally verified.     

Bragg-induced orbital angular-momentum mixing in paraxial high-finesse cavities

Numerical calculation of vector electromagnetic modes of plano-concave microcavities reveals that the polarization-dependent reflectivity of a flat Bragg mirror can lead to unexpected cavity field distribution for nominally paraxial modes. Even in a rotationally symmetric resonator, certain pairs of orbital angular momenta are necessarily mixed in an excitation-independent way to form doublets. A characteristic mixing angle is identified, which even in the paraxial limit can be designed to have large values. This correction to Gaussian theory is of zeroth order in deviations from paraxiality. We discuss the resultant nonuniform polarization fields. Observation will require small cavities with sufficiently high Q. Possible applications are proposed.     

Fiber-optic tunable filter with a concave mirror

In order to implement a fiber-optic Fabry-Perot tunable filter with a simple configuration, a concave mirror is made at the end of the optical fiber. The concave mirror is fabricated by attaching a thin polycarbonate (PC) film on the fiber end, pressing the PC film with a fiber ball to form a dimple, and then depositing a multilayer dielectric mirror. The concave mirror aligned to the fiber core makes the cavity alignment easy with a simple alignment configuration. Because of the self-alignment function of this cavity, a small, reliable, and fast filter could be fabricated.     

抽运角锥棱镜腔电光调Q固体激光器

利用角锥棱镜的退偏效应实现了电光调Q固体激光器的偏振耦合输出.器件采用热传导冷却半圆柱面LD阵列侧向泵浦Nd∶YAG泵浦几何,获得在20 Hz运行条件下,脉冲能量163 mJ/pulse、脉冲宽度6.5 ns、发散角3.5 mrad、能量稳定性±2.8％、光光效率16.7％的理想性能.与传统平行平面腔相比,具有效率高、峰值功率大、输出能量和脉宽可调,且输出稳定等优点.     

猫眼激光谐振腔横模选择特性研究

将猫眼逆向器作为激光谐振腔的一个腔镜组成猫眼谐振腔。介绍了猫眼逆向器的结构,阐述了猫眼逆向器中凸透镜和凹面镜的间距改变时猫眼曲率半径的相应变化,并通过有效地控制该间距来选择激光横模,从而保证基横模输出。在激光谐振腔衍射积分方程的基础上,运用牛顿柯特斯数学方法,对不同参量下的猫眼激光谐振腔的横模状况进行分析,得出了各阶横模对应的特征值和功率损耗,计算出保证基横模输出的参量,并与实验对比,得到了一致的结论,为激光器的横模选择和控制提供了一种简便易行的新方法。     

Quantum nondemolition measurement by optomechanical coupling

 We show that a single-port optical cavity with a movable mirror can provide a quantum non-demolition measurement of the intensity of a light beam. Due to radiation pressure, the cavity length is sensitive to the light intensity and can be measured with a secondary light beam. Signal-meter correlations can be made very large even at non-zero temperature. We study these correlations when the moving mirror is a plane–convex crystal resonator and we show the importance of spatial matching between light and acoustic modes. Received: 12 June 1996/Revised version: 3 September 1996