Coupling Losses and Discrimination of Annular Waveguide Laser Resonators

１ＩｎｔｒｏｄｕｃｔｉｏｎＳｉｎｃｅｔｈｅｆｉｒｓｔｒｅａｌｉｚａｔｉｏｎｏｆｔｈｅｏｐｅｒａｔｉｏｎｏｆａｗａｖｅｇｕｉｄｅｇａｓｌａｓｅｒｂｙＳｍｉｔｈ［１］ｉｎ１９７１,ｃｏｎｓｉｄｅｒａｂｌｅｓｔｕｄｉｅｓｈａｖｅｂｅｅｎｍａｄｅｏｎｔｈｅｗ...     

同轴圆筒波导激光器谐振腔的耦合损失及模式特征

计算了同轴圆筒波导谐振腔的耦合损失,结果表明存在三种低耦合损失谐振腔结构,最后分析了谐振腔的模式特性及其设计方法。     

输出环状光束的新型激光谐振腔

提出一种输出环状光束的新型激光谐振腔,即在稳定激光谐振腔中采用外环耦合方式得到环状光束的输出。利用For-Li数值迭代算法求解此类激光谐振腔的积分方程,通过计算机编程计算了平面一凹球面稳定谐振腔的输出端平面镜在不同半径的情况下,谐振腔镜面上和衍射耦合输出场基模的振幅和相位分布。计算结果预示了当输出端平面镜半径小于通常的稳定腔的基模半径时,衍射耦合输出场有稳定的环状光束输出。实验中TEA CO2激光器采用印刷电路板预电离结构,增益长度90cm,腔长5m,球面全反射镜曲率半径20m,输出端平面镜半径4．5mm,得到了内环半径为4．5mm、外环半径为5．5mm的基模环形光斑输出。从而在理论上和实验上证实了该方案产生环状光束的可行性。     

同轴放电环形增益区谐振腔镜面的场分布

 对几类环形增益区谐振腔进行了比较，得出利用谐振腔两镜之一的全工作面输出的新型环形增益区谐振腔是适合的谐振腔。提出了一种计算全工作面输出的同轴放电环形增益区谐振腔镜面场分布的方法，利用几何方法对腔镜镜面进行划分,得出了基于菲涅尔-基尔霍夫衍射积分定理的积分区域，并对该区域进行了有限元划分，应用计算机编程计算出了同轴放电环形增益区谐振腔镜面处的光场分布和相位分布。近场分布在环形区中央部分近似地呈高斯分布，且沿径向出现高阶模场分布特点，沿角向无差别。     

平板波导谐振腔耦合损失的厄米高斯展开分析法

平板波导内的场按自由空间传播的厄米高斯函数展开，计算了平板波导谐振腔的耦合损失，给出了平板波导中ＥＨ１１模的耦合损失与球镜的曲率及位置的关系。结果表明存在两种特定的结构使耦合损失最小。     

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。     

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.     

Evaluation of losses and group effective refractive index of Er3+:Ti:LiNbO3 optical waveguides

In this paper, we report some experimental results concerning several types of loss measurements of Er³⁺:Ti:LiNbO₃ optical waveguides by using optical methods. Using the Fabry-Pérot interferometry method, we evaluated the attenuation coefficient of an optical waveguide resonator for a laser radiation having λ = 1.55 μm. We also evaluated the insertion losses, polarization dependent losses, and coupling with external losses. Additionally, from the transmitted spectra of the symmetrical monomode Fabry-Pérot optical waveguide resonator, we were able to evaluate the value of the group effective refractive index.     

Dielectric shielded nanoscale patch laser resonators

Dielectric shielded nanoscale patch laser resonators are introduced. Low-index dielectric shield layers surrounding a high-index core are shown to significantly reduce both metal and radiation losses. Structures suitable for both optical and electrical pumping and smaller than the vacuum wavelength in all three dimensions are shown to have a low enough threshold gain to lase at room temperature. Shifting the gain medium core provides control over the radiation pattern of the resonator and enables coupling of the laser light into a waveguide, opening opportunities for chipscale integration.     

Diffraction losses of an asymmetric stable laser resonator using an equivalent resonator

An asymmetric stable laser resonator with one large mirror and the other mirror apertured is considered. An equivalent symmetric resonator is derived which enables the determination of the theoretical diffraction losses from Li's computations. Experiments are done to test the validity of the predictions. The experimental diffraction losses agree very well with the theoretical values and the usefulness of the concept of equivalent resonator is therefore confirmed.     

Design of a 2.5 THz submillimeter wave laser with optical pump beam guiding

A ring resonator design using the same set of mirrors for pump beam and submillimeter wave (SMMW) beam guiding is introduced. Optimal design is discussed on the example of a 2.5 THz methanol laser. It turns out that due to refocussing of the pump beam on the pinhole certain focal lengths of the focussing mirror, which mainly is responsible for the beam guiding, should be avoided. Diffraction losses and pinhole losses determine optimalg-parameters for which the pump beam guiding losses of the resonator are minimum, and optimal pump beam waist radii.The setup of an experimental laser with the optimized resonator and the experimental setup to measure laser performance are described, and results concerning laser output power, beam quality and efficiency are discussed.     

平板波导谐振腔的耦合损失和模式特征

相应于方波导或圆波导的三种低耦合损失的谐振腔结构，即平行平面、半共心、半共焦结构、计算了不同纵横比的平板波导内各种模式的耦合损失，讨论了平板波导激光器谐振腔的设计和模式特征。     

跑道形玻璃波导谐振腔滤波器的研制

采用Ag+-Na+离子工艺，在K9玻璃上制备了跑道形波导谐振腔滤波器.测试得到该滤波器自由光谱范围为FSR=0.177 nm，对比对为Cr＝7.5 dB.同时分析得到耦合器的耦合系数为κ=0.916，耦合器和环形腔的损耗因子分别为δ=0.55,γ=0.48.耦合器的两波导几乎相连、条波导边缘不规则和一次离子交换波导表面缺陷是造成该波导滤波器具有较大损耗的主要原因.通过改进工艺技术降低波导损耗，该滤波器可以用于光通信、传感等领域，也可与其它波导结构相结合实现新的功能.     

Angular spectrum theory to calculate coupling efficiency in rectangular waveguide resonators

Coupling efficiency of the rectangular waveguide resonators are discussed in terms of the method of angular spectrum theory. Under the condition given in the paper, the coupling coefficients for the EH₁₁ mode in the rectangular waveguide resonator are presented as a function of mirror curvature and position. It is shown that there exist two special geometries to provide low coupling efficiency. The method can be applied to the other modes.     

High-power multibeam CO2 laser for industrial applications

Multibeam CO₂ lasers consist of a large number of closely packed parallel glass discharge tubes, all sharing a common plane parallel resonator. This paper describes construction and operation of a CW multibeam CO₂ laser consisting 20 discharge tubes and cooled length of 1500 mm, delivering 1 kW power. A high-frequency pulser is used for producing preionization in all discharge sections for initiating the main DC discharge simultaneously in all discharge tubes. Plane parallel resonator consists of a plane ZnSe mirror of 90 mm diameter having 60% reflectivity and a gold-coated copper mirror of same diameter. This laser operates in waveguide regime and laser power is not critically sensitive to mirror misalignment.     

Quantum wells micro-ring resonator laser emitting at 1746 nm for gas sensing

Gas sensing for measurement of gas components, concentrations, and other parameters plays an important role in many fields. In this Letter, a micro-ring resonator laser used for gas sensing is experimentally demonstrated. The multi-quantumwells micro-ring laser based on whispering-gallery modes with an annular resonator and an output waveguide was fabricated. A single-mode laser with a wavelength of 1746.4 nm was fabricated for the first time, to the best of our knowledge,experimentally. The output power of 1.65 m W under 40 m A injection current was obtained with a side-mode suppression ratio over 33 d B.     

Hybrid optical resonator type laser proposed for direct coupling into optical fiber

Combining one stable resonator with a concave mirror and a coupling-hole plane mirror, and another unstable resonator having a concave mirror and a convex mirror, a new hybrid optical resonator type laser has been proposed by overlapping the concave mirror as a common one and fitting the convex mirror exactly to the coupling-hole. Using theABCD law, the so-called g-parameters are first found for beam confinement. Then, based on the eigen-equation, the field distribution on the plano-convex mirror is obtained with the g-parameters above. Knowing this field distribution results in an effective transmittanceG _{e e}. Finally, the ratio of the inner convex to outer plane mirror radii can be determined for an optimum coupling in both the limiting cases of homogeneously and inhomogeneously broadened gain media. Some numerical examples will also be given for a CO₂ laser having the proposed hybrid resonator.     

Tunable, narrow-band, grating-assisted microring reflectors

Tunable, grating-assisted ring resonator based optical mirrors are analyzed and their characteristics numerically evaluated. Mode number selection rules are presented to aid mirror optimization for high, narrow-band reflection and efficient sidelobe suppression. Data is presented on tuning sensitivity, on the effect of coupling on bandwidth and reflection coefficient, and on the influence of waveguide and grating loss on mirror performance. Group delay in the presence of loss and circuit parameter variations is also treated.     

Theory of a planar free-electron maser with transverse electromagnetic flux circulation in a 2D Bragg mirror

A planar free-electron maser with a resonator consisting of a 2D entrance Bragg mirror and a 1D exit Bragg mirror is theoretically studied in the framework of a nonstationary 2D model. In such a configuration, the 2D Bragg mirror provides synchronization of the radiation emitted by a wide (compared with the wavelength) ribbon-shaped electron beam. The transverse electromagnetic energy fluxes arising in this mirror are closed through an additional coupling waveguide, which provides a single-mode single-frequency masing regime insensitive to variation of the beam parameters over wide limits.     

热变形谐振腔的激光模式理论分析

 应用微扰理论,对微热变形腔的激光模式进行了理论计算与分析;给出了激光模式之间的耦合以及等效光束发散角与镜面变形量之间的关系。结果表明：镜面中心处热变形量越大,模式之间的耦合越强,激光腔模式发生畸变就越严重;当镜面中心处热变形量为0.5λ时,基模TEM₀的中心光强将下降50%,其等效光束发散角将增大到镜面无变形时的2倍。