Fiber-coupled short Fabry-Perot resonators

An air-gap Fabry-Perot resonator with plane mirrors between closely spaced fiber ends may yield low throughput because of the poor match between the modes of typical single-mode fibers and the resonant mode in the air-gap cavity. The throughput can be improved by confining the resonant mode by a hollow dielectric tube placed inside the resonator. Short fiber-coupled Fabry-Perot resonators with and without an inserted hollow dielectric waveguide and expressions for their transmission losses are derived. It is shown that the throughput of both types of resonator can be improved significantly by using fiber with large mode size to couple to the resonator. The special fiber is then spliced to a conventional single-mode fiber. It is concluded that the resonator with an inserted hollow dielectric waveguide offers increased throughput for resonators with high finesse     

一种基于光纤环境G-T腔的光交错复用器

提出利用级联光纤环镜构成全光纤G -T干涉仪,并运用光波叠加原理和传输矩阵理论详细研究了其滤波和相位特性,给出了其相移表达式,分析了级联光纤环镜中各参数对其相位特性的影响。在此基础上,设计了一种基于级联光纤环镜G -T腔的新型全光纤交错复用器,该器件光学结构简单,具有DWDM系统所需的截止度和平坦度。     

Measurement of the electric field pattern of a Fabry-Perot resonator used in quasi-optical gyrotrons

The field pattern of the resonator used in a quasi-optical gyrotron operating in the millimetre wave range is measured. Two resonators are studied: one composed of a spherical mirror and an ellipsoidal grating and the other symmetric using two mirrors with annular slots. The measurements indicate that the electric field distribution is gaussian, in spite of the complex geometry of the resonator, and thus provide an experimental basis for the assumption often used to compute the efficiency of quasi-optical gyrotrons.     

多棒平行平面腔动态工作特性的研究

基于等价腔方法,将高功率固体激光器使用的二棒平行平面腔的结果推广到多棒平行平面腔。推导出了g*参数和等价腔长的解析表达式。对这类光腔的动态工作特性做了详细分析,并给出了数值计算例。研究表明,对两类多棒对称平行平面腔,在g*参数图上的动态特性曲线是过原点的一条直线。若多棒的热焦距有小的偏差,特性曲线不再是直线。然而,用适当调节镜和棒以及棒间距离的方法可以使特性曲线重新成为一条直线。因而采用这种方法可以补偿棒的热焦距偏差,给出了有关的数学公式。     

高斯反射率方形平凹腔激光模场的有限元分析

利用柯林斯公式和边界有限元方法，将方形球面镜腔的衍射积分方程转化为矩阵方程，并对高斯反射率方形平凹腔的模场分布进行了数值计算。研究结果表明，高斯反射率方形平凹腔具有较好的选模性能，可以应用于高功率激光器以获得高质量的激光光束。     

适用于圆筒形放电区的四镜半外腔的失调分析

基于矩阵分析方法,对提出的圆筒形增益区的四镜半外腔的腔镜失调特性进行了分析,并用数值计算例子加以说明,给此类新型激光器的实际工作,如加工腔元件、选择腔参数、安装调试等提供了参考.     

Explicit formulas for the fundamental mode of a linear resonator with elliptic mirrors and construction of higher order modes

A linear resonator bounded by elliptic (hyperbolic) mirrors with noncoinciding principal curvature directions is considered. Explicit analytic formulas describing the fundamental mode of such resonator are derived in the principal approximation. A procedure of constructing higher order modes is developed. The potentialities of the technique are exemplified by considering a resonator with mirrors whose shapes are close to spheres and a resonator with elliptic mirrors whose shapes are close to each other.     

环形腔内光束的传输特性

本文以四面镜8字形稳定环形腔为代表,利用传输矩阵法、等效厚透镜法和腰斑处为参考面展开等三种方法,对环形腔内光束的传输特性作了详细的计算和分析,并与驻波腔的结果进行了比较。对象散的影响亦作了讨论。     

Design and Cold Tests of Asymmetric Quasioptical Resonators

This paper presents the design and test of asymmetric quasioptical resonators for gyrotron applications, where most of the diffraction output coupling comes from the smaller of two mirrors. A computer code based on scalar diffraction theory is used to calculate the resonator losses and the electric field near the mirrors. Resonators with mirror separations approaching confocal have reduced side lobes in the diffraction patterns, which should allow for better power transmission and focusing. Cold tests have been performed at 94 and 141 GHz to measure the quality factor of the asymmetric resonators as a function of mirror separation and mirror misalignment. Typical resonator parameters include 65 cm mirror separation, 1-3% output coupling and 85% of the losses from the small mirror. A half-symmetric resonator with one flat and one curved mirror has also been investigated. The calculated values of Q are in reasonably good agreement with the cold test measurements.     

Cold tests of quasi-optical gyrotron resonators

Cold tests which have been performed on quasi-optical gyrotron resonators at frequencies near 94 and 120 GHz to measure cavity Q are discussed. The separation between the resonator mirrors was varied between 0.15 and 0.35 m. Quality factors ranging from 10000 to 100000 are shown. Good agreement is shown between the measured data and values calculated from scalar diffraction theory. The experimental effect of misaligning the mirrors is examined     

Acoustooptic modulators for single-mode fibers

The design of in-line acoustooptic modulators for single-mode fibers is discussed. The basic configuration consists of a cylindrically symmetric piezoelectric transducer fabricated on the fiber surface, so that the fiber itself acts as a cylindrical acoustic resonator. Depending on the fiber design, the acoustic wave can induce phase, birefringence, or polarization modulation of the light in the fiber. Pairs of the polarization modulators in series can be used to shift the optical frequency. Factors affecting the performance of all of these devices are discussed.     

The advantages of a negative branch unstable resonator for use with free-electron lasers

The sensitivity to misalignment of an almost concentric stable resonator is compared to that of a negative branch confocal unstable resonator, with specific applications to free-electron lasers. The practicability of both resonators is examined for both grazing and normal incidence configurations within the constraints of maximum feasible length, finite angular stability of resonator mirrors, size (determined by cooling requirements) of laser beam on mirrors, and minimum electron beam spot size in the wiggler. For the examples presented, a numerical fast Fourier transform propagation code was used.     

高斯镜平凸非稳腔本征模场的有限元数值计算

为了研究激光在高斯镜平凸非稳腔中的模式和相位特征,在SIEGMAN分析多元件非稳腔的理论基础上,采用有限元数值方法计算耦合输出镜镜面反射率为高斯分布的圆镜平凸非稳腔本征模场分布。将光场在腔内一次往返的ABCD系数代入惠更斯-基尔霍夫衍射积分方程,可以写出光场往返一次的衍射积分方程。将镜面分割成若干个等宽圆环,把衍射积分方程转化成矩阵相乘形式,经过数值计算,得到理想空腔和非共轴空腔优先起振的光场本征模式分布结果与相位特性。计算结果表明,当合适选择输出镜半径与高斯反射率分布,可以得到光斑半径为0.3cm的基模高斯光束输出,此计算结果与实验结果相符。同时也讨论了耦合输出镜对光束质量的影响。     

On Optimum Mirrors of the Fabry-Perot Resonator Filled with Anisotropic Medium (Short Papers)

A Fabry-Perot resonator formed by parabolic cylindrical reflecting mirrors and filled with anisotropic medium is analyzed theoretically. For the resonance of the extraordinary wave in such a resonator, optimum shapes of the reflecting mirrors exist, which are derived from the boundary conditions on each mirror.     

内含热薄透镜四镜环形腔的光束特性

二平二凹四镜8字型环形腔是色心激光、激光陀螺等研究经常采用的谐振腔。本文采用热薄透镜模型,运用等效腔方法,分析了四镜环形腔的光束特性。详细讨论了热效应对谐振腔基本特性的影响,给出了四镜环形腔的热不灵敏条件。这些结果对谐振腔的设计和应用具有一定的指导作用。     

考虑波导壁影响开放腔孔耦合品质因数的计算

本文计算了矩形波导壁孔耦合球面开放腔的孔耦合品质因数。计算运用了偶极子近似模型，考虑了波导壁对偶极子磁极化率张量的影响。计算结果和文献（２）中实验值吻合得很好。     

Spectral characteristics of coupled-waveguide Fabry-Perotresonators and filters

Conventional Fabry-Perot resonators provide a narrow spectral width but lack the capability of longitudinal mode discrimination. A coupled-waveguide Fabry-Perot structure made of two parallel waveguides with reflecting mirrors at the ends is proposed for applications as mode selective resonator in single-mode diode lasers and as narrow-band wavelength filters. The interference of counter propagating waves from reflection by end mirrors and the coupling of waves between the two parallel waveguides contribute to the operation of this resonator structure. Thus, the device exhibits the attributes of both Fabry-Perot resonator and directional coupler. The coupled-mode theory of parallel waveguides is employed to analyze the structure. Both cases of identical and unidentical waveguides are examined. Resonance conditions and spectral characteristics are determined. It is shown that the coupled-waveguide Fabry-Perot resonator provides significant improvement in mode discrimination capability and longitudinal mode spacing over the conventional Fabry-Perot resonator     

扭转椭圆双折射光纤环形腔输出特性

对扭转椭圆双折射光纤环形腔的带阻输出特性进行了分析和计算。结果表明，任意椭圆偏振态输入，光纤的双折射和扭转使光纤环形腔带阻输出特性中的谐振峰分裂为两组，对应于光纤的两个本征偏振态。谐振频率发生偏移，偏移量取决于光纤的双折射参数和扭转速率，两组谐振峰的相对幅度取决于光纤的双折射参数、扭转速率和输入偏振态。若输入偏振态为双折射光纤本征偏振态之一，就仅出现一组谐振峰。光纤的双折射和扭转对环形腔的精细度没有影响。     

Dielectric mirror embedded optical fiber couplers

Dielectric mirrors in multimode and single-mode silica fibers have been produced by a fusion-splicing technique. Mirrors oriented normally and at a 45° angle to the axis have been studied. Fibers with angled internal mirrors serve as compact directional couplers with low excess optical loss (≈0.2 dB for multimode and 0.5 dB for single mode at 1.3 μm) and excellent mechanical properties. The reflectance is found to be wavelength dependent and strongly polarization dependent. Far-field scans of the reflected output power measured with a white-light source show a pattern that is almost circularly symmetric. The splitting ratio in a multimode coupler measured with a laser source is much less dependent on input coupling conditions than in conventional fused biconical-taper couplers. Spectral properties of multilayer mirrors oriented normally to the fiber axis have been investigated experimentally, and a matrix analysis has been used to explain the results     

Dual-wavelength erbium-doped fiber laser with asymmetric fiber Bragg grating Fabry-Perot cavity

A novel dual-wavelength fiber laser with asymmetric fiber Bragg grating（FBG） Fabry-Perot（FP） cavity is proposed and experimentally demonstrated. A couple of uniform FBGs are used as the cavity mirrors, and the third FBG is used as intracavity wavelength selector by changing its operation temperature. Experimental results show that by adjusting the operation temperature of the intracavity wavelength selector, a tunable dual-wavelength laser emission can be achieved. The results demonstrate the new concept of dual-wavelength lasing with asymmetric FBG FP resonator and its technical feasibility.