Nonlinear theory of multimode action in loss modulated lasers

A set of cavity modes which are coupled together by an externally synchronous driven loss modulator is considered. The nonlinear polarization of the material is taken into account, and the mode coupling for the case when many modes are coupled together is treated nearly exactly. The formulas for the pulse shape and pulse width are explicitly derived for the case of a homogeneously broadened line. They show the dependence of these quantities on the system's parameters, such as pump power, modulator driving strength, detuning between modulator frequency, frequency spacing of the cavity modes, etc. Several configurations for the locked modes which have higher pulse widths are possible. This last result in particular seems to be completely new.     

Coupled phase-shift distributed-feedback semiconductor lasers fornarrow linewidth operation

Mode properties of a coupled phase-shift distributed-feedback (DFB) structure are analyzed and the feasibility of narrow-linewidth emission is shown theoretically. The structure consists of a multiple number of phase-shift DFB laser units which are arranged in tandem and coupled with each other through additional phase shift of corrugation. Optimum structure parameters were determined for two coupled laser units so that the frequency detuning is zero and the mode pattern is the flattest. The mode analysis shows that the intensity distribution is flatter and the normalized coupling constant can be larger than those for the conventional DFB laser with a single phase shift. This indicates that the cavity length can be extended with less influence from the longitudinal spatial hole burning effect     

Coupled mode theory of optical resonant cavities

This paper presents a theory describing coupled optical resonant cavities by means of systems of time-dependent coupled equations for the field amplitudes of standing waves in each resonator. The coupling coefficients entering the theory are derived from first principles. To the author's knowledge, this theory is new. The coupling coefficients can approximately be related to the amplitude transmission coefficients of traveling waves passing between the two resonant cavities. This relationship is checked for an example. Finally, we show that the mode amplitudes of one cavity can be eliminated so that the field in the other cavity becomes coupled to samples of itself taken at earlier times. The coupled-cavity theory applies to cavities with loss or gain. It is here expressed in scalar approximation, but it can easily be extended to vector fields.     

波导-双腔-量子点耦合系统透射谱的解析解研究

通过波导-双腔-量子点耦合系统的哈密顿量和系统算符的海森堡运动方程推导出系统的输入-输出关系。进一步地,我们利用格林函数理论,解析地定义了微腔和波导之间的耦合速率。并在此基础上求解系统算符的运动方程,推导出整个系统透射谱的解析形式。数值计算了整个系统透射谱与双腔之间的距离（其导致双腔与波导的耦合速率之间有一相位因子）和失谐因子之间的关系。研究发现透射谱紧密依赖于双腔距离和失谐因子。这种结构在量子信息、量子计算或光开关方面有着潜在的应用前景。     

Frequency-domain analysis of the mode-locked and frequency-doubled homogeneous laser

A frequency-domain analysis of the mode-locked intracavity frequency-doubled laser is pursued. An expression for pulse-width is derived based upon basic laser parameters and the nonlinear coupling of the frequency doubler. It is found that mode locking induces an additional loss to the cavity even in the ideal case, so that the frequency-doubled output power at optimum coupling is less than an optimally coupled fundamental frequency laser with identical losses.     

The Michelson resonator free-electron laser. II. Supermodestructure and mirror detuning effects

For pt.I, see ibid., vol.29, no.2, p.452-64 (1993). Conventional mode-locked laser theory is applied to the longitudinal mode structure in an RF linac-driven Michelson resonator free-electron laser (FEL). A greatly simplified derivation of the small-signal small-gain FEL coupled mode equations is obtained. These equations are solved numerically in the frequency domain to study the supermode evolution in the presence of mode dependent cavity losses. The results are compared with simulations of the detuned Michelson resonator FEL using a pulse propagation code based on the Maxwell-Lorentz equations of motion. Increasing the interferometer detuning broadens and shifts the cavity detuning curve, narrows the supermode spectrum, and decreases the hypermode decay rates. The practical consequences of each of these effects are discussed. A simple theory describing the dependence of the hypermode decay rates on interferometer detuning, in which the decay rates are abruptly decreased beyond a critical detuning that depends primarily on the slippage length, is outlined     

An original approach to the design of bandpass cavity filters withmultiple couplings

A novel approach to the design of general cavity filters with each cavity coupled to an arbitrary number of other cavities is presented. This approach is based on a suitable characterization of the filter structure which does not require one to model separately the cavities (resonators) and the coupling elements. Suitably defined equivalent admittances are associated with each cavity allowing one to design the filter structure once the parameters of a suitable low-pass prototype are given; an efficient procedure for the synthesis of such a prototype with equiripple passband response is also presented which allows one to arbitrarily prescribe transmission zeros placed in the complex plane (even asymmetrically). The described design approach is particularly convenient when the filter structure does not allow a simple modeling of the resonators and coupling elements separately. This is the case of slot-coupled cavity filters and of filter structures based on arrays of coupled transmission lines. It is also shown that the simplified design approach often adopted in the past, where only two coupled cavities at a time are considered, can produce large errors even in the case of filters with all attenuation poles at infinity (i.e., two couplings per cavity)     

基于对称型齿波导和纳米盘的类EIT和慢光效应

设计了一种新型的基于金属表面等离子体激元（SPPs）的亚波长金属-绝缘体-金属（MIM）型类电磁诱导透明（EIT）系统,该系统由一个直波导及其两边对称的齿形腔和纳米盘耦合而成。利用耦合模式理论对结构进行分析,并通过时域有限差分方法（FDTD）进行数值模拟。当齿形腔和纳米盘的共振频率相近,可以获得类EIT效应,改变齿形腔的长度和纳米盘的半径可以调节透明窗的位置。该装置可以用作高性能的类EIT滤波器,透过率高达77.5%,半高宽低至35.5 nm,群指数高达65,为高度集成光网络提供了一种新的方法,可应用于波长选择器、超快开关、光存储等设备。     

异型微腔本征模式分析

微腔模式特性的研究是微腔各种应用的基础.采用时域有限差分方法(FDTD)可以获得微腔模式的频谱响应特性.通过对平面平行腔的验证,发现FDTD方法可以获得同理论较吻合的结果.对平面圆腔的回音壁模(WGM)腔模特性的分析表明;这种腔体尺寸同波长相当的谐振腔具有较好的选模特性.通过腔边界由两个带变形参数的圆弧所构成的平面异型微腔在不同变形参数下模式特性的细致研究,则发现通过改变腔形可以达到改善腔模模式特性的目的,这表明优化腔形设计是优化腔性能的一条可行思路.     

基于模式匹配的同轴腔耦合分析及其应用

采用半解析的模式匹配方法分析并计算矩形同轴谐振腔之间窗口耦合的耦合系数,结合等效电路计算了存在第三个谐振腔时两同轴谐振腔之间窗口耦合的耦合系数.比较了计算两腔的耦合系数时,采用模式匹配法和有限元法的计算效率.结果表明,达到相同精度时,模式匹配法具有更高的计算速度.根据计算所得耦合系数设计了两个分别具有对称响应和非对称响应的C波段同轴腔滤波器,经调试后,滤波器测试结果与设计的理论响应吻合较好,验证了模式匹配方法计算矩形同轴谐振腔通过窗口耦合的耦合系数的有效性.     

强耦合双间隙微波谐振腔的特性分析

该文设计了一类适合用于较低频波段宽带多注速调管的新型微波谐振腔强耦合双间隙腔,并采用了较精确的三维电磁场模拟计算程序ISFEL3D对其各种主要参数和特性做了详尽的计算和理论分析,结果表明,强耦合双间隙微波谐振腔工作于模时具有特性阻抗高而且体积小的突出优点,同时模频率与2模频率的间隔明显增大。另外,该文还利用两种常用的集总元件等效电路对计算数据和结论进行验证,并对两种常用的等效电路的精确度做了讨论。     

半导体激光器

Surface-emitting semiconductor lasers can make use of external cavities and optical pumping techniques to achieve a combination of high continuous-wave output power and near-diffraction-limited beam quality that is not matched by any other type of semiconductor source. The ready access to the laser mode that the external cavity provides has been exploited for applications such as intra-cavity frequency doubling and passive mode-locking.     

两个失谐腔中两个原子的纠缠突然死亡

在两个腔都失谐的情况下,两个原子分别与两个光场耦合的模型中,研究了初始纠缠的两个原子出现了纠缠突然死亡现象的问题.从结果可以看出:两个原子的纠缠在任何情况下都呈现明显的周期性现象;两个原子的纠缠突然死亡不仅与两个腔的失谐量大小有关系,而且还与两个原子的初始纠缠度大小有关系,同时探讨了原子和场的两个耦合系数的比值大小对两个原子的纠缠突然死亡的影响.     

Analysis and suppression of SSN noise coupling between power/ground plane cavities through cutouts in multilayer packages and PCBs

The authors introduced a model of simultaneous switching noise (SSN) coupling between the power/ground plane cavities through cutouts in high-speed and high-density multilayer pack-ages and printed circuit boards (PCBs). Usually, the cutouts are used in multilayer plane structures to isolate the SSN of noisy digital circuits from sensitive analog circuits or to provide multiple voltage levels. The noise-coupling model is expressed in terms of the transfer impedance. The proposed modeling and analysis results are compared with measured data up to 10 GHz to demonstrate the validity of the model. It is demonstrated that the cutout is the major gate for SSN coupling between the plane cavities, and that substantial SSN coupling occurs between the plane cavities through the cutout at the resonant frequencies of the plane cavities. The coupling mechanism and characteristics of the noise coupling, from which a method of suppression of the SSN coupling evaluated was also analyzed and discussed. Proper positioning of the cutout and the devices at each plane cavity achieves significant noise suppression at certain resonant frequencies. The suggested suppression method of the SSN coupling was successfully proved by frequency domain measurement and time domain analysis.     

Tolerance of phase-locked VCSEL arrays to random and systematic parameter deviations among cavities

Cavity parameter deviations from their nominal values affect phase-locking in vertical-cavity surface-emitting lasers (VCSEL) arrays. The phase-locking tolerance is studied analytically and numerically for both random as well as systematic parameter variations. Parameter-induced deviations among the cavity eigenfrequencies cause the dominant effect. For small externally imposed variations, self-regulated nonlinear frequency pulling among cavities overcomes original detuning and permits phase-locking. The root mean square (rms) tolerance threshold is derived by solving a quasi-random matrix eigenvalue under simplifying assumptions. Tolerance increases with intercavity coupling strength and decreases with the array size M. Systematic variations, such as thermal drifts, exhibit a lower tolerance decreasing as /spl prop/1/M or faster, compared to random variations /spl prop/1//spl radic/M. Theory results qualitatively agree with large size array simulations employing actively coupled rate equations.     

Efficient generation of Bell-cat states in remote cavities

In the context of cavity quantum electrodynamics （QED）, a potential scheme is proposed to generate entangled coherent states. The scheme includes twice interactions of two-level atoms with cavities. In the first interaction, two atoms are sent into a microwave cavity with the large detuning respectively. And then the second interaction is that the two atoms enter another microwave cavity and are driven by a resonant classical field meantime. When we choose the proper interaction time and make measurement on the two atoms, the two microwave cavity mode fields are determinatively entangled. In addition, it is easy to generalize the scheme to multi-cavity and multi-atom.     

A coupled optoelectronic oscillator with three resonant cavities

A new single-mode optoelectronic oscillator (OEO) with three coupled cavities is proposed and demonstrated. A Fabry-Perot (F-P) cavity fiber laser and an optical-electrical feedback branch are coupled together to construct an optoelectronic oscillator, where the F-P cavity fiber laser serves as a light source, and a modulator is placed in the laser cavity to implement reciprocating modulation, which simultaneously splits the laser cavity into two parts and forms a dual-loop configuration. To complete an optoelectronic oscillator, part of optical signal is output from the F-P cavity to implement the feedback modulation, which constructs the third cavity. Since only the oscillation signal satisfies the requirements of all the three cavities, a single-mode oscillation can be finally achieved. Three resonant cavities are successfully designed without adding more optoelectronic devices, and the side-modes can be well suppressed with low cost. The oscillation condition is theoretically analyzed. In the experimental demonstration, a 20 GHz single longitudinal mode microwave signal is successfully obtained.     

Modeling of Tuning of Microresonator Filters by Perturbational Evaluation of Cavity Mode Phase Shifts

Microresonator filters, which are realized by evanescent coupling of circular cavities with two parallel bus waveguides, are promising candidates for applications in dense wavelength-division multiplexing. Tunability of these filters is an essential feature for their successful deployment. In this paper, we present a framework for modeling of tuning of the microresonators by changes in their cavity core refractive index. Using a reciprocity theorem, a perturbational expression for changes in the cavity propagation constants due to slight modifications of the cavity core refractive index is derived. This expression permits us to analytically calculate shifts in the spectral response of the 2-D resonators. Comparisons of the resultant shifts and spectra with direct simulations based on a coupled mode theory show satisfactory agreement.     

A Michelson interferometer with balanced detection for thecharacterization of modulation and noise properties of semiconductorlasers

A Michelson interferometer with balanced detection, built to study semiconductor lasers, is analyzed. The quantum noise due to vacuum fluctuations, coupling losses, detector quantum efficiency, and spatial mode mismatches are included in the analysis. The limits for frequency noise detection and the sensitivity of the interferometer are examined. It is observed that under ordinary measurement conditions the frequency noise can only be measured up to slightly above the cavity bandwidth of the laser. Comprehensive measurement procedures are proposed, and experimental results showing the frequency modulation response, measured from 10 kHz to 8 GHz, of a three-section distributed feedback (DFB) laser and the frequency noise spectra, measured from 30 MHz to 8 GHz, of a two-section distributed Bragg reflector (DBR) laser are presented. These results reveal new cavity detuning effects in the noise characteristics of tunable DBR lasers     

多腔径向耦合输出系统的等效电路分析

多腔径向耦合构成的输出系统具有多个频率点(离散状态)的宽带特性,该文从等效电路的观点出发,给出了多腔径向耦合输出系统的等效电路,根据Kirchhoff定律建立了矩阵方程,导出阻抗矩阵,解出其系统的谐振频率,鉴于它的多模特点抽出它的典型状态推导出它的模式结构,揭示了径向耦合双腔的模式分布,反对称于轴向耦合双腔(双间隙腔),它是由2--2模构成。