串联微环谐振器的光学特性

根据波导耦合方程,导出了串联微环谐振器的传输矩阵,并分析了环数、环间耦合系数以及损耗对串联微环谐振器输出特性的影响。数值模拟表明,串联微环谐振器具有光子带隙的特征。当环数增加时,通带内满足谐振条件的波长数增加;当环间耦合系数增加时,可使通带带宽加宽;通过适当选择环数和环间耦合系数,可以实现滤波和波分复用(WDM)的功能。选用脉冲宽度为50 ps的高斯型激光脉冲注入微环谐振器,发现当环间耦合系数较小时,出射脉冲相对于入射脉冲具有光学延迟的效果,并且随着环数的增加,延迟时间逐渐增大,而当环间耦合系数较大时,光学延迟效果不明显。     

Widely Tunable Coupled Cavity Lasers at 1.9 μm on GaSb

Wide range tunable lasers based on the coupling of two Fabry-Peacuterot resonators have been realized in the (AlGaIn)(AsSb) material system. The laser consists of two longitudinally oriented ridge waveguide cavities coupled through an etched gap. By carefully controlling the injection current of each resonator and, therefore, varying the corresponding resonator temperature, a single-mode tuning range of 45 nm is achieved     

基于亮模式调控的双频等离激元诱导透明超材料

设计了一种太赫兹波段双频等离激元诱导透明(DBPIT)超材料。该超材料由位于中央的空竹(Diabolo)型结构单元 和对称分布于其两侧的不同尺寸的两个开口谐振环(SRR)组合而成,空竹结构单元和两 个SRR分别充当该体系的亮、暗 模式谐振器。数值仿真结果表明,超材料透射频谱具有明显的双透明窗特征,通过调节亮 模式的几何尺寸,可以实现对双透 明窗透射幅度的调控。基于经典的三谐振子模型(three-oscillator model)及表面等 离激元(surface plasmon theory)理论, 阐述了DBPIT效应的物理机制:亮模式分别与两个暗模式之间的近场强耦合。亮模式采用 具有磁场增强功能的空竹结构, 有助于提高暗模式的磁场响应,进而大幅度增强亮、暗模式之间的耦合,达到提高透明 窗透射幅度的目的。这项工作为设计 具有高度灵活性的多波段功能器件(如慢光器件、可调谐传感器和多波段选择性开关器 件)开辟了新的途径。     

Cold tests and modeling of low-Q quasi-optical resonators

Measurements are reported on low-Q open resonators at 85 GHz with a large centered coupling hole in each mirror. This is the first study of open resonators with large diffraction losses and efficient input coupling at millimeter wavelengths. The input resonator for a quasi-optical gyroklystron is described with quality factor Q=2000 and 13% round-trip losses where approximately 65% of the incident power in the waveguide is coupled to the fundamental TEM₀₀ mode. Two models have been developed to calculate the coupling from the rectangular waveguide through a circular aperture into the open resonator. Both models properly account for the increased diffraction loss of the resonator when coupling apertures are present. Measured results are in reasonably good agreement with values calculated using both scalar diffraction theory and an equivalent-circuit model     

Periodic structures on coupled slot resonators in the grounding layer of microstrip transmission line

The spectrum of natural frequencies of the resonator has been calculated. The specified resonator includes a microstrip transmission line with discontinuity in the form of two rectangular coupled slot resonators in the grounding layer. Based on the above spectrum and using the transverse resonance method the scattering matrix of the principal wave of the microstip transmission line on this discontinuity was calculated. The scattering characteristic of the periodic structure consisting of a finite number of cells in the form of coupled slot resonators in the grounding layer of microstrip line indicates that with due regard for their mutual coupling the losses in the first stopband can be reduced by 3–5 dB as compared with the characteristic obtained by tandem connection of the scattering matrices of separate slot resonators in the grounding layer of microstrip line.     

Magnetostatic surface wave straight-edge resonators

The performance of the magnetostatic surface wave straight-edge resonator (MSSW-SER) is presented. The resonator uses a rectangular YIG film to propagate MSSWs where the straight edge serves as a reflector. Problems arising from coupling to width mode resonances and their effect on the main resonance are investigated. Through a careful choice of YIG and transducer parameters, the interference effects of the width mode resonances with the main resonance are minimized. As a result, highQ tunable microwave resonators with a tuning range from 2–20 GHz, insertion loss less than 10 dB, and spurious rejection better than 10 dB could be designed and fabricated. This MSSW resonator could be used to construct a tunable low-phase-noise feedback oscillator. However, the tuning range of this MSW feedback oscillator is limited by the phase change of the external amplifier circuit.     

A composite-resonator mode description of coupled lasers

We investigated the behavior of two lasers operating with coupled resonators. Our analysis involves a decomposition of the laser field in terms of the passive composite resonator eigenmodes. The interaction between the laser field and the active medium is found to lead to mode coupling, The dominant coupling mechanism is cross saturation among composite-resonator modes. The effects of cross saturation on the output of the coupled lasers are investigated. Our results are valid for all values of coupling between lasers. Examples of lockbands calculated using the composite-resonator mode analysis are presented.     

The Michelson resonator free-electron laser. I. Passive modestructure and mode decay

A general analysis of the evolution of phase locking in an RF linac-driven Michelson resonator free-electron laser (FEL) is presented. By providing a delay of one RF period in the secondary arm of the interferometer, successive optical pulses can be coupled at the beamsplitter, so that they build up from noise with a definite phase relationship. Phase locking is described in terms of longitudinal mode decay by extracting the mode losses directly from the passive frequency response of the resonator. The analyses predict significant mode structure simplification in microsecond macropulses, so that high-resolution spectroscopy is feasible on RF linac-driven FELs. Simulations of the perfectly tuned Michelson resonator FEL are described from spontaneous radiation to saturation, using a one-dimensional pulse propagation code. Excellent agreement with the analytical results in the small-signal regime is demonstrated     

Relationship between the slowing and loss in optical delay lines

In this paper, we demonstrate the relation between the amount of slowing and the amount of insertion loss in an optical slow wave structure when the material used has finite absorption. The delay properties are calculated as a function of wavelength for a single Fabry-Perot resonator and a delay line consisting of multiple coupled resonators. In all of these delay lines, if the amount of delay increases, the insertion loss of the line likewise increases. For low material loss, the normalized increase in delay is equal to the normalized increase in insertion loss. We also compare a coupled resonator delay line to a simple waveguide made of the same material and with the same amount of delay. The simple waveguide always has less insertion loss than the coupled resonator line because of the unavoidable reflection from the coupled resonator line. Even in the case of an asymmetric mirror delay line with zero reflection at the input, the simple waveguide has less insertion loss.     

太赫兹硅基微环谐振器的设计与分析

设计了一个工作频率在太赫兹大气传输第一窗口的硅基波导型微环谐振器。利用传输矩阵法和耦合模理论计算微环谐振器的传输函数,并对波导耦合系数进行分析,获得微环谐振器的临界耦合条件。采用时域有限差分法分析微环谐振器的性能参数,并与串联双环谐振器性能参数相比较。结果表明：单环谐振器的自由谱宽范围为27 GHz,插入损耗为0.3 dB。单环与双环谐振器的响应谱线形状因子分别为0.16和0.52,即串联双环谐振器使谐振谱线顶端更平坦,滚降度增高。Abstract：关键词：     

基于枝节线加载谐振器的可调滤波器设计

传统基于变容二极管的双频电可调滤波器由于外部容值的加入,该类滤波器的插损变大,同时相对带宽锐减。基于多模谐振器结构,提出了一种新型的工作频段独立、电可调的双频带通滤波器。该滤波器由短路枝节线加载谐振器和一对1/4 波长谐振器组成。在各自的谐振器末端加载带有变容二极管的外部偏置电路,1/4 波长谐振器构成第一通带,短路枝节线加载谐振器构成第二通带,两通带之间互不干扰,单独调节。应用奇偶模分析法及调节耦合间距的方法,确保双通带均出现两个极点,保证其带宽的稳定性。该电可调滤波器第一通带可调范围为0.7 ~0.85 GHz,第二通带可调范围为0.9 ~1.05 GHz,同时双频带的相对带宽基本保持在10% 以上,较以往的双频电可调滤波器,该款滤波器的相对带宽有了较为明显的提升。     

The Filling Factor of Shielded Dielectric Resonators

The use of dielectric resonators at microwave frequencies usually requires a shield to prevent loss of energy by radiation, and a coupling network. The efficiency of a given circuit depends on the filling factor, which expresses the circuit ability to store most of the input energy in the resonator, and little in the coupling network and surrounding space. The resonator is sometimes excited by means of a coupling loop inside the shield, or with a propagating waveguide. In any case, some energy is stored outside the dielectric material. A calculation is presented for the internal and external stored energies, for the case of a rectangular dielectric resonator in a rectangular waveguide. Verification was performed by measuring the insertion loss of an acoustic delay line, which illustrates an interesting application of dielectric resonators.     

两种小型谐振器在微带均衡器中的应用

本文阐述了新型发卡式谐振器和矩形螺旋形谐振器及其在微带均衡器中的应用,利用上述两种谐振器分别设计了两种微带均衡器单子结构电路,通过仿真发现采用新型发卡式谐振器的均衡器单子结构电路具有频率调谐功能;而采用螺旋形谐振器的均衡器单子结构电路不仅具有频率调谐功能,而且具有衰减幅度调节功能,解决了由于实际加工误差引起的频率和衰减偏移问题。最后根据实际需要采用这种螺旋形谐振器设计了一个微带均衡器并给出了其频率曲线。     

Time resolved beam divergence from a copper vapor laser withunstable resonator

The temporal evolution of the far-field intensity distribution (and hence beam divergence) for the output of a CVL operating with both on-axis and off-axis unstable resonators is investigated in detail. The CVL output pulse consists of several temporally resolved components, where each successive component has lower divergence approaching the diffraction limit. A comprehensive model for the divergence of each temporal component from a CVL operating with a variety of unstable resonators is presented. In this model the resonator controls the output divergence by imposing geometric constraints on the propagation of spontaneous emission on repeated round-trips through the unstable resonator equivalent lensguide. Effects of resonator asymmetry and radial gain variations on the far-field intensity distribution (and hence divergence) are evaluated. Experimental measurements of the temporal evolution of output divergence from a CVL operating with both on-axis and off-axis unstable resonators and for a variety of excitation conditions are also presented. For CVL operation at high pulse repetition frequency the ASE at the start of the laser pulse has an annular profile. This annular gain distribution is found to modify the output far-field intensity distribution of the earlier temporal components of the laser pulse. For on-axis unstable resonators these components are found to have annular far-field intensity distributions, whereas for off-axis unstable resonators they have greatly reduced but anisotropic divergence     

Dielectric resonator with discrete electromechanical frequency tuning

A novel approach for discrete frequency tuning of dielectric resonators based on electromechanical actuators such as the microelectromechanical system is presented. The concept is based on the intermodal coupling between the TE/sub 01/spl delta// mode of a cylindrical dielectric resonator and the radially arranged planar slotline resonators. The resonance frequency of the dielectric resonator is changed by switching a resistive load at the open end of each quarter-wave slotline resonator leading to a variation of the coupling between the slotline resonator mode and the TE/sub 01/spl delta// mode of the dielectric resonator. As a consequence, the resonance frequency of the TE/sub 01/spl delta// mode changes. Based on this novel tuning concept, discrete tuning by 5 MHz in 0.25-MHz frequency steps was demonstrated for a test resonator at 2 GHz. The unloaded quality factor is about 12000 and the measured switching time is about 1 ms.     

Wide tunable double ring resonator coupled lasers

A double ring resonator coupled laser (DR-RCL) is proposed and analyzed in this letter. Benefiting from the uniform peak transmission, narrow bandwidth and other superior characteristics of traveling wave supported high-Q resonators, DR-RCLs offers many promising advantages over the conventional tunable lasers, including ultra wide wavelength tuning range, high side mode suppression ratio, uniform threshold and efficiency, narrow linewidth, low frequency chirp, and simple fabrication. A DR-RCL with a moderate optical loss ~10 dB/cm in the ring resonators can achieve a wavelength tuning enhancement of ~50. With such a large tuning leverage, DR-RCLs could utilize the electrooptic effects to achieve ultrafast tuning speed with a wide tuning range covering the material gain bandwidth     

Waveguide laser resonators with a tilted mirror

We present a multimode theory of square-bore waveguide laser resonators with one well-aligned and one tilted plane mirror. Our theoretical results for mode content, resonator loss, and power output agree reasonably well with experimental results from an RF-excited CO2laser with a376 times 1.5 times 1.5mm Al/Al2O3waveguide. The mode propagation coefficients of this structure are discussed. We model a diffraction grating as a plane mirror with a wavelength-dependent tilt, and conclude that previous single-mode theory has underestimated the severity of the line-hopping constraint on tunable waveguide CO2laser performance.     

Design and modeling of waveguide-coupled single-mode microringresonators

We discuss a first-order design tool for waveguide-coupled microring resonators based on an approximate solution of the wave propagation in a microring waveguide with micron-size radius of curvature and a large lateral index contrast. The model makes use of the conformal transformation method and a linear approximation of the refractive index profile, and takes into account the effect of waveguide thickness, dispersion, and diffraction. Based on this model, we develop general design rules for the major physical characteristics of a waveguide-coupled microring resonator, including the resonance wavelength, the free spectral range, the coupling ratio, the bending radiation loss and the substrate leakage loss. In addition, the physical model provides leads to alternative coupling designs. We present two examples, one using a phase-matching parallel waveguide with a smaller width than the ring waveguide, and the other using a vertical coupling structure. Both these designs significantly increase the coupling length and reduce or eliminate the dependence on a narrow air gap in a waveguide coupled microring resonator     

可调谐单纵模多波长光纤激光器的研究

为了实现对台阶高度和绝对距离等物理量的高精度干涉测量,采用在一个光纤激光器中构建多个激光谐振腔的方法,构建了能同时发出多波长激光的光纤激光器。每个激光谐振腔都利用掺铒光纤作为增益介质,利用光纤光栅作为波长选择元件,改变光纤光栅的布喇格波长,即可改变对应谐振腔的激光波长。各个激光谐振腔独立但部分重叠,在重叠区域利用光纤耦合器构成复合子腔,使每个激光谐振腔都是复合激光谐振腔,从而使每个激光谐振腔都发出单纵模激光。结果表明,该光纤激光器能同时发出功率和频率都稳定的多波长激光,且每个波长都是单纵模激光;在4h内,每个波长的波长稳定性优于0.01nm。该设计对可调谐单纵模多波长光纤激光器的研究是有帮助的。     

基于枝节加载开环谐振器的带阻滤波器设计

提出了一种具有良好谐波抑制功能的双枝节加载开环谐振器,加载枝节采用均匀阻抗结构,与同尺寸的开环谐振器相比,结构更紧凑,能够更好地抑制寄生模,而且可以达到更低的谐振频率。分析了加载枝节参数对带阻滤波器抑制二次谐波的影响。通过在加载的双枝节间引入集总可变电容,可以使谐振器具备谐波抑制性能的同时,实现中心频率可调的功能。基于双枝节加载环谐振器设计出一种可调带阻滤波器,中心频率可以在900MHz ~2. 65GHz 范围内调节,而且最低寄生阻带能够抑制到8GHz。