Amplitude-frequency characteristic of a nonlinear spin wave interferometer operating in a quasi-nonlinear regime

A thin-film nonlinear spin wave interferometer has been experimentally studied. The concept of a quasi-nonlinear operation regime is introduced for the first time and the boundaries of the quasi-nonlinear dynamic range of the interferometer are experimentally determined. It is shown that the nonlinear spin wave interferometer operating in the quasi-nonlinear regime can be characterized, like linear devices, by the amplitude-frequency characteristic (AFC). However, an increase in the signal power level within the quasi-nonlinear dynamic range at the input of the nonlinear interferometer leads, in contrast to the case of a linear device, to a frequency shift of the AFC. An analysis of the AFC shift indicates that a 180° change in the phase difference between the interfering signals at each separate frequency is achieved for the input power varied within the limits of the quasi-nonlinear dynamic range. This behavior shows the possibility of using the nonlinear interferometer for the processing of microwave signals without undesired distortion of the signal waveform.     

Nonlinear microwave spin wave interferometer

The characteristics of a nonlinear microwave spin wave interferometer were experimentally studied for the first time. The interferometer was implemented according to a bridge scheme with a nonlinear spin wave phase shifter based on an yttrium-iron garnet film. The maximum sensitivity of the nonlinear interferometer with respect to the input signal level was reached with a phase shifter operating on the forward volume spin waves. In the GHz frequency range, an increase in the microwave power up to a few mW led to a signal phase shift exceeding 180 °.     

Suppressing pulsed microwave signals in a nonlinear spin wave interferometer

The suppression of S-band microwave pulses in a nonlinear spin wave interferometer was experimentally studied for the first time. The microwave interferometer employed a nonlinear spin wave phase shifter based on an yttrium iron garnet film. A signal representing a periodic sequence of rectangular pulses with a power of up to 2.5 mW passes through the nonlinear interferometer without distortion, while an increase in the pulse power to 13.8 mW results in virtually complete suppression of the pulsed signal.     

平衡式E/F类功率放大器的设计与实现

为了解决功率放大器设计过程中存在的效率低和输入/输出端回波损耗较大的问题,设计了一种工作频率为1.5 GHz的平衡式功率放大器。通过采用3 dB定向耦合器对射频信号进行分配及合成,大大降低了输入/输出端的驻波系数,并将逆F类功率放大器的谐波控制网络引入E类功率放大器的匹配电路中。使用ADS对晶体管进行负载牵引和源牵引,得到晶体管的输入/输出阻抗,同时结合晶体管的寄生参数,在输出匹配电路中对二次谐波、三次谐波分别进行开路和短路处理,且为了进一步提高功率放大器的工作性能,在输入电路结构中抑制了二次谐波。选用GaN HEMT器件CGH40010F晶体管,利用ADS软件进行电路仿真,并采用Rogers4350b高频板材制作该功率放大器的实际测试电路板。仿真优化和实测表明：在输入功率为28 dBm时,该功率放大器的输出功率为41.54 dBm,漏极效率为76.99%,功率附加效率（power additional efficiency,PAE）达到73.59%,输入/输出端驻波系数小于2,同时具有160 MHz的高效率带宽,且最大输出功率较单管功率放大器提高了3 dB。实测结果与仿真数据有一定的误差,但仍有较好的一致性,满足设计指标要求,验证了设计方法的可行性。该设计方法具有效率高和回波损耗低的优势,提高了功率放大器的设计效率,使它在当今高效绿色节能的射频微波通信系统中具有广阔的应用前景。     

Coupled-wave Analysis of the Bragg Effect Waveguide Coupler

Abstract

A coupled-wave analysis is presented for the Bragg effect waveguide coupler. This device consists of a slanted volume phase grating which is integrated inside the lightguiding layer of an optical waveguide. The wave propagation is described by a set of leaky wave modes. Self-consistency relations are derived to determine the angular mode spectrum and the corresponding radiation loss coefficients. A maximum input coupling efficiency of 80% is predicted for an incident Gaussian beam. The power of a waveguide mode should be emitted into a single output beam reaching an efficiency of almost 100%.     

Generation of chaotic microwave pulses with the help of passive synchronization of spin wave self-modulation frequencies in self-oscillatory ring systems

Passive synchronization (PS) of spin wave self-modulation frequencies of a chaotic microwave signal has been observed for the first time in a self-oscillatory ring system involving a nonlinear passive element with saturable absorption. The development of PS led to the generation of a periodic train of chaotic microwave pulses with an off/duty ratio exceeding 20. It is established that the repetition period of chaotic microwave pulses can be controlled by changing gain in the ring system.     

Design of couplers for traveling wave RF structures using 3D electromagnetic codes in the frequency domain

In this paper, a simple equivalent circuit model of a traveling wave RF structure with input and output couplers is introduced. A few properties related to evaluating the reflection coefficient of the single coupler are then obtained and discussed. From these properties, a general procedure to design couplers for traveling wave structures using 3D electromagnetic codes in the frequency domain is derived. Finally, an example of coupler design for a 2π/3 X band accelerating structure is illustrated.     

Kerr nonlinear coupler with varying linear coupling coefficient

Abstract

We investigate a codirectional nonlinear coupler composed of two Kerr nonlinear waveguides. Unlike the conventional device, the linear coupling between the guides is supposed to be a variable function of the propagation distance. We calculate quantum statistical and dynamical properties of the Kerr nonlinear coupler with a coherent input and analyse the influence of coupling variation on oscillations in mean photon number. The possibility to control the switching characteristics and principal squeezing effect by adjusting the form of coupling function is shown.     

An electroacoustic method for measuring the intensity of high-powermicrowave pulses

A microwave electric field intensity meter for single high-power radiowave pulses is described. A surface acoustic wave (SAW) dielectric acoustic line is used which has nonlinear electroacoustic properties and is comprised of two transducers. The first (nonlinear) transducer is affected by a microwave electric field and provides the SAW excitation due to nonlinear effects. A delayed SAW signal, carrying information about the electric field strength, is received by a linear interdigital transducer     

Multistrip couplers for surface acoustic wave sensor application

We present a new surface acoustic wave gas sensor utilizing a multistrip coupler on LiNbO₃ and LiTaO₃ substrates and using copper phthalocyanine as a sensor layer for NO₂. The sensor signal originates from surface conductivity changes induced by the adsorbed NO₂. This variation in conductivity leads to a changing coupling efficiency of the multistrip coupler and thus to variations in the insertion loss of the device. Rayleigh and shear wave devices with operating frequencies of 170 and 243 MHz have been tested. A sensitivity of better than 1 ppb NO₂ in air was achieved     

Effective matching in a nonlinear directional coupler with waveguide mismatching and nonuniform nonlinearity

A variable-coupling-coefficient nonlinear directional coupler with mismatching and nonuniformity is studied by means of coupled mode equations with effective mismatching. It is pointed out that the effective mismatching can be cancelled out for any given input power by properly adjusting the magnitudes of the mismatching and nonuniformity. Numerical examples are given to show that complete power transfer between two waveguides can be achieved for a mismatched and nonuniform nonlinear directional coupler and for a Gaussian as well as an exponential variable-coupling-coefficient nonlinear directional coupler.     

A 2*4 all optical decoder switch based on photonic crystal ring resonators

Based on photonic crystal ring resonators and nonlinear Kerr effect in this paper, we proposed a 2*4 all optical decoder switch. Our proposed structure has two logic input ports and one bias input port. This decoder switch has four output ports. Via these two logic input ports, we control the bias signal to transfer toward which output port. We employed numerical methods such as plane wave expansion and finite difference time domain methods for analyzing the proposed structure.     

GaAs超高速光调制器的研制

从理论与实验两方面研究了ＧａＡｓ定向耦合型行波光调制器，首次报导了重掺杂ｎ＾＋型薄层对电场分量相当于导体，对磁场分量相当于绝缘体这一发现；首次提出了一种具有对称宽电极的新型结构，并研制成功开关电压为８．５Ｖ，微波折射率为３．６，在３０ＧＨｚ情况下传输损耗小于１０ｄＢ／ｃｍ，根据ｓ参数测试３ｄＢ带宽达到３２ＧＨｚ的行波调制器。     

基于扫频技术的乐甫波器件测试系统

介绍了乐甫波器件的结构,设计制作了乐甫波器件,给出了乐甫器件的制作参数,搭建了基于扫频技术的测试系统,包括信号源模块、信号采集模块、微控制器模块等.通过DDS芯片AD9912在一定频率范围内,以一定频率间隔扫频输出高频正弦激励信号,利用AD8302芯片测量扫频范围内每一频率点的器件输入激励信号与输出响应信号幅值比,描绘出幅频特性曲线,并给出器件谐振频率.该测试系统的测量结果与网络分析仪基本一致,实现了网络分析仪的扫频功能.     

Adiabatic polymer-glass-waveguide all-optical switch

We propose an adiabatic all-optical switch that is composed of an asymmetric Y-branch ion-exchanged glass waveguide with a strip of nonlinear polymer loaded on top of one branch. The properties of nonlinear wave propagation in the device are investigated in detail. By extending the effective-index method to the analysis of nonlinear waveguides, we calculate the nonlinear dispersion curves in successive sections to explain the evolution of normal modes in the device. As the multivalued propagation constants exist in the tapered directional coupler region, the device possesses an abrupt switching behavior and nonreciprocal properties. To demonstrate nonlinear switching behaviors in the Y-branch waveguide further, we employ a beam propagation method to simulate optical-field propagation. The inputs by three different ports are investigated, and the results agree well with the dispersion-curve analysis.     

Theoretical treatment, simulation, and experiments of doubly resonant sum-frequency mixing in an external resonator

We describe the theoretical treatment of the doubly resonant sum-frequency mixing in an external resonator. The nonlinear conversion efficiency is increased by the resonantly enhanced circulating powers at both wavelengths. The model predicts the circulating powers in the resonator at two input wavelengths: the powers that are reflected off the input coupler and the output power at the sum frequency. Numerical simulation gives the design optimization of the system. The result of the simulation is compared with the result of a continuous-wave 355-nm generation experiment, where 0.66-W of output power was obtained.     

一种带自反馈光纤谐振腔的全光纤MZI型梳状滤波器的理论研究

为了改善全光纤马赫-曾德尔干涉仪(MZI)型梳状滤波器(interleaver)的输出特性,提出了由一个2×2光纤耦合器和一个带自反馈光纤谐振腔的光纤耦合器级联组成的改善型的全光纤MZI型梳状滤波器。根据其结构,利用光纤传输理论和矩阵理论推导出了该器件的输出表达式,并进行了数值模拟分析。结果表明：该器件在合理参数的情况下,利用带自反馈光纤谐振腔引入的相位调节效应,使其25 dB截止带宽为46.7 GHz,约占50 GHz频率间隔的93.4%,输出光谱形态近似于方波。当存在传输损耗时,两束干涉光信号的幅度不存在明显的差异,降低了传输损耗对滤波器消光特性的影响,与传统的光纤谐振环辅助非平衡MZI型梳状滤波器相比,不仅降低了传输损耗对滤波器消光特性的影响,而且还将所需的光纤耦合器数目减少至2个,使其在未来的密集波分复用系统中能发挥重要作用。     

Integration of grating couplers in two-story waveguides for rotary displacement sensing

An integrated-optic device, constructed by stacking two types of grating coupler in a two-story structure of waveguides, is proposed for sensing angular displacement of spindle rotation. In the first story a guided wave is diffracted by a grating coupler and becomes a sensing beam. The sensing beam is reflected by a mirror with a quarter-wave plate attached to a spindle head and is coupled back into the second story by another grating coupler. We measured the rotary displacement of the spindle by detecting variation of polarization direction of the reflected beam. A prototype device has been designed and fabricated, and the operation principle is experimentally confirmed.     

A Wide-Band Digitally Controlled Frequency and Phase Multiplier

A method is considered for designing a wide-band digitally controlled frequency and phase multiplier based on nonlinear polynomial transformation of Chebyshev type applied to the initial harmonic signal. The method provides an output signal with a frequency a multiple of the input signal 1. Computer calculations are used to examine the output signal.     

All-optical logic devices with cascaded nonlinear couplers

The switching behaviors of cascaded nonlinear couplers were investigated. They have nearly ideal digital-switching characteristics, and their output power levels can be adjusted by means of varying the nonlinear coupling coefficient of the final coupler. The two-input excitation nonlinear cascaded couplers can perform not only switching operations but also a series of logic operations. The logic operations depend mainly on the coupling length of the two-input coupler and its initial inputs. The power corresponding to the rising and falling ridge of the logic operating waveforms can be shifted effectively by means of varying the switching power of the reshaper. Allowable ranges of three important parameters-coupling length of the two-input coupler L(1), bias optical power P(bia), and phase difference psi between the signal and bias beams for six fundamental logic operations-were calculated. Curves for design considerations and suggestions for the best choice of parameters for stable and reliable logic operations and, or, xor, nand, nor, and nxor are also presented individually.