Angular spectrum characters of high gain non-critical phase match optical parametric oscillators

The angular spectrum gain characters and the power magnification characters of high gain non-walk-off colinear optical parametric oscillators have been studied using the non-colinear phase match method for the first time. The experimental results of the KTiOAs04 and the KTiOP04 crystals are discussed in detail. At the high energy single resonant condition, low reflective ratio of the output mirror for the signal and long non-linear crystal are beneficial for small divergence angles. This method can also be used for other high gain non-walk-off phase match optical parametric orocesses.

MULTI-PEAK MATCH INTENSITY RATIO METHOD OF QUANTI-TATIVE X-RAY DIFFRACTION PHASE ANALYSIS

A new method for quantitative phase analysis is proposed by using X-ray diffraction multi-peak match intensity ratio. This method can obtain the multi-peak match intensity ratio among each phase in the mixture sample by using all diffraction peak data in the mixture sample X-ray diffraction spectrum and combining the relative intensity distribution data of each phase standard peak in JCPDS card to carry on the least square method regression analysis. It is benefit to improve the precision of quantitative phase analysis that the given single line ratio which is usually adopted is taken the place of the multi-peak match intensity ratio and is used in X-ray diffraction quantitative phase analysis of the mixture sample. By analyzing four-group mixture sample, adopting multi-peak match intensity ratio and X-ray diffraction quantitative phase analysis principle of combining the adiabatic and matrix flushing method, it is tested that the experimental results are identical with theory.

Phase-matching analysis of four-wave mixing induced by modulation instability in a single-mode fiber

Four-wave mixing induced by modulation instability in a single-mode fiber is analyzed from the phase-matching point of view. For the two-channel transmission, a method is proposed to select the four-wave-mixing-induced sidebands, which is based on the proper use of a continuous-wave and a pulse as light sources. We find that a mass of sidebands are generated in the modulation instability resonance region, and the power of the sideband increases with not only the peak power of the pump pulse but also the continuous-wave power which acts as a seed. The research will provide guidance for fiber communication and sensing systems using wavelength division multiplexing technology.

Adaptive Phase Matching in Grover’s Algorithm

When the Grover’s algorithm is applied to search an unordered database, the successful probability usually decreases with the increase of marked items. In order to solve this problem, an adaptive phase matching is proposed. With application of the new phase matching, when the fraction of marked items is greater , the successful probability is equal to 1 with at most two Grover iterations. The validity of the new phase matching is verified by a search example.

Rejection of Direct Blast Interference Based on Signal Phase-Matching Array Processing

In bistaic acoustic testing, there will be strong direct blast interference. An algorithm based on signal phase-matching array processing that rejects direct blast interference in bistatic acoustic testing has been studied, through which the object scattering signal is accurately extracted. Characteristics of bistatic acoustic testing and signal phase matching processing principle are fully integrated in this algorithm. Firstly, the direct blast interference is calculated from the receiving signal based on three subarrays signal phase matching processing. Secondly, the direct blast is rejected by subtraction from the receiving signal. In this way the limitations of the high signal to noise ratio that signal phase matching processing required for direct calculating the object scattering signal can be avoided. Simulation and sea trial results show that, when the ratio of signal to interference is greater than -20 dB, this algorithm of direct blast interference rejection based phase matching signal processing can accurately extract the object scattering signal.

Phase-matched second-harmonic generation in hybrid polymer-LN waveguides

Here we propose a hybrid polymer-LN waveguide for achieving phase-matched second-harmonic generation(SHG).From the aspect of super-mode theory,the geometric parameters of the hybrid semi-nonlinear waveguide were optimized to utilize both symmetric(even)and antisymmetric(odd)modes of the pump and SHG waves so as to facilitate phase matching with large modal overlap.Phase matching between a fundamental even(TE_(00)-like)mode at 1320 nm and a fundamental odd(TE_(01)-like)mode at 660 nm was found with a calculated modal overlap integral of 0.299,while utilizing the largest nonlinear coefficient d_(33),and achieving an efficient calculated normalized conversion efficiency of 148%W^(-1)·cm^(-2).Considering the fabrication feasibility of such hybrid waveguide with features including etchless,large dimension,and low structural sensitivity,we believe our findings would provide a useful reference for future on-chip efficient nonlinear conversion devices.

A two-mode squeezed light based on a double-pump phase-matching geometry

We theoretically investigate the frequency-nondegenerate and frequency degenerate squeezed lights with a four-wave mixing process(4WM)driven by two pump fields crossing at a small angle.Different from a 4WM process driven by a single pump field,the refractive index of the corresponding probe field,np,can be converted to a value that is greater than 1 or less than 1 by an angle adjustment.In the new region with np<1,the bandwidth of the gain is relatively large due to the slow change in the refractive index with the two-photon detuning.In this region with an exchange of the roles of the pump and probe beams,the frequency degenerate and spatial nondegenerate twin beams can be generated,which has potential application in quantum information and quantum metrology.

Phase matched scanning optical parametric chirped pulse amplification based on pump beam deflection

Combined with the optical beam deflection,a novel approach of phase matched broadband scanning optical parametric chirped pulse amplification(OPCPA)was proposed.For this scheme,there was no superfluous operations to the chirped signal pulse which propagated in a changeless direction straightforward,but the pump beam were deflected in space with time by passing through a KTN crystal,which was applied with varied driving voltage.The theories of phase matching of each chirped signal frequency based on pump beam deflection was analyzed detailedly.And the type-I amplification of chirped signal with 800 nm central wavelength and 20 nm bandwidth pumped by 532 nm in BBO crystal was simulated as a case in point.The simulation results showed that the spectral distribution of chirped signal pulse was almost the same as the initial form,i.e.,there was nearly no narrowing on the amplified spectrum by using of the scanning OPCPA based on pump beam deflection.In addition,the simulations demonstrated that it was worth minimizing the voltage deviation applied to KTN crystal as much as possible for the sake of better waveform,larger bandwidth and higher conversion efficiency of amplified signal pulse in the proposed scanning OPCPA.

Enhancement of Phase Matching Ability in One-Dimensional Photonic Crystal through Plasma Materials

We have theoretically studied the modal dispersion equation and effective refractive index of one-dimensional plasma photonic crystals (1-D PPCs) having different materials in one unit cell. The dispersion relations related for such structure is derived by solving Maxwell’s equation using the transfer matrix method. It is found that the presence of plasma in a unit cell enhanced the phase matching ability and provides additional degree of freedom to control phase matching condition compared to the conventional one-dimensional photonic crystals (1-D PCs).

Improved statistical fluctuation analysis for two decoy-states phase-matching quantum key distribution

Phase-matching quantum key distribution is a promising scheme for remote quantum key distribution,breaking through the traditional linear key-rate bound.In practical applications,finite data size can cause significant system performance to deteriorate when data size is below 1010.In this work,an improved statistical fluctuation analysis method is applied for the first time to two decoy-states phase-matching quantum key distribution,offering a new insight and potential solutions for improving the key generation rate and the maximum transmission distance while maintaining security.Moreover,we also compare the influence of the proposed improved statistical fluctuation analysis method on system performance with those of the Gaussian approximation and Chernoff-Hoeffding boundary methods on system performance.The simulation results show that the proposed scheme significantly improves the key generation rate and maximum transmission distance in comparison with the Chernoff-Hoeffding approach,and approach the results obtained when the Gaussian approximation is employed.At the same time,the proposed scheme retains the same security level as the Chernoff-Hoeffding method,and is even more secure than the Gaussian approximation.

Design of a coated thinly clad chalcogenide long-period fiber grating refractive index sensor based on dual-peak resonance near the phase matching turning point

A novel method for designing chalcogenide long-period fiber grating(LPFG) sensors based on the dual-peak resonance effect of the LPFG near the phase matching turning point(PMTP) is presented. Refractive index sensing in a high-refractive-index chalcogenide fiber is achieved with a coated thinly clad film. The dual-peak resonant characteristics near the PMTP and the refractive index sensing properties of the LPFG are analyzed first by the phase-matching condition of the LPFG. The effects of film parameters and cladding radius on the sensitivity of refractive index sensing are further discussed. The sensor is optimized by selecting the appropriate film parameters and cladding radius. Simulation results show that the ambient refractive index sensitivity of a dual-peak coated thinly clad chalcogenide LPFG at the PMTP can be 2400 nm/RIU, which is significantly higher than that of non-optimized gratings. It has great application potential in the field of chemical sensing and biosensors.

Algorithm of far-field centre estimation based on phase-only matched filter

Estimation of the far-field centre is carried out in beam auto-alignment. In this paper, the features of the far-field of a square beam are presented. Based on these features, a phase-only matched filter is designed, and the algorithm of centre estimation is developed. Using the simulated images with different kinds of noise and the 40 test images that are taken in sequence, the accuracy of this algorithm is estimated. Results show that the error is no more than one pixel for simulated noise images with a 99% probability, and the stability is restricted within one pixel for test images. Using the improved algorithm, the consumed time is reduced to 0.049 s.

Phase-Matching and Parametric Conversion for the Mid-Infrared in As₂S₃Waveguides

We illustrate two As2S3 waveguide designs for four-wave mixing, which can generate 3.03 μm mid-infrared light from a 1.55 μm near-infrared signal source and a 2.05 μm pump source. Through simulations, we verify that four-wave mixing phase-matching efficiencies up to 100% can be achieved using dispersion engineering to maintain the dispersion at 2.05 μm near to zero. The best conversion efficiency is –10 dB. When the waveguide length is 1 cm, the parametric conversion bandwidth is 1525 nm. We also evaluated the shift of 100% phase-matching efficiency wavelengths based upon fabrication tolerances.

Phase-Type分布数据拟合方法综述

Phase-Type(PH)分布具有良好的通用性和易于进行解析处理的特性,因此PH分布已经成为随机模型解析分析的重要工具。PH分布的数据拟合方法是应用PH分布的基础,分析了PH分布数据拟合的矩估计方法、极大似然估计方法及PH分布拟合重尾分布数据方法的研究现状,并讨论了PH分布数据拟合方法进一步的研究方向。

使用光谱分析实现弯管中两相流含气率的预测

空气被夹带进入发动机润滑油系统形成油气两相流后,会严重影响润滑系统的正常运行。因此实现发动机润滑油系统中油气两相流含气率的准确和快速测量具有十分重要的意义。基于光谱匹配方法,对发动机润滑油系统在弯管处的油气两相流含气率进行了测量研究。首先使用近红外、可见光和紫外光谱仪获取油气两相流在2个流速、5个温度工况下0.10%~1.00%含气率范围(间隔0.06%)的吸光度数据并进行分析,确认油气两相流在三个波段下均有吸收,且吸收强度与含气率有关;其次提出将数据预处理结合光谱相似性测度方法并应用于弯管含气率光谱分析中,显著降低了基于原始光谱的含气率预测的最大相对误差。在近红外波段通过使用数据增强方法如中心化(center)和标准化(autoscaling)并结合光谱角余弦方法,得出新润滑油的含气率最大相对误差相对于原始光谱得到的数值从48%降低到36%。利用该方法分别在三个波段进行含气率预测,试验工况包括2个流速、5个温度,分析了两相流的温度和流速对含气率预测的影响。温度30.0℃,流速5.1 m·min^(-1)下,含气率信息在紫外波段(193.5~413.8 nm)与光谱向量的方向或形状差异的联系更为紧密,含气率预测的最大相对误差仅为6%。在近红外和可见光波段,流速或温度一定时,最大相对误差随着温度或流速的增加均有减小趋势。紫外波段下温度对含气率预测效果没有特定的影响规律,随着两相流的流速增加,含气率预测的最大相对误差有增大趋势。结果表明对于透光性较好的新润滑油,使用紫外光谱仪进行含气率数据的采集,含气率的预测选用标准化预处理结合光谱角余弦方法,得到的含气率预测最大相对误差最小。

基于相关接收的雷达相参脉冲信号分选方法

相参性可以作为雷达信号分选的特征参数,能够有效避免“漏批”情况发生。文中基于相关接收原理,分析了不同初始相位差对相关接收后输出信号波形的影响。通过推导输出信号主峰波形表达式,建立了雷达脉冲信号的相参特征模型,并给出了信号分选流程。仿真表明该模型适用于脉冲信号交叠复杂的情况,在信噪比为-5 dB,初相差为0.2 rad时,仍具有一定分选正确率。

基于改进的迭代重加权OMP的稀疏FIR滤波器设计

有限脉冲响应(Finite Impulse Response, FIR)滤波器具备线性相位和稳定性的优点,在雷达信号处理、图像处理、电子对抗等领域被广泛应用。然而高性能的FIR滤波器通常需要较高的阶数,导致硬件实现成本高、系统功耗大。针对该问题,提出了一种改进的迭代重加权正交匹配追踪算法,设计稀疏的线性相位FIR滤波器。该算法采用Frobenius范数简化在每次迭代中求解目标稀疏FIR滤波器的过程,并且引入一个对数函数迭代更新权重。仿真结果表明,在某些情况下所提算法设计的滤波器比已有的稀疏滤波器设计方法具有更短的有效滤波器长度和更少的滤波器非零抽头个数,避免了硬件实现时乘法器和加法器的大量使用,从而有效地降低了实现成本和系统功耗。

基于电力线载波通信的智慧园区电力物联网精准时间同步方法

智慧园区各类新兴业务在电力物联网(power internet of things,PIo T)设备提供的数据支持下开展。这些业务具有严格的时间同步要求。如何在现有电力线载波通信(power line carrier,PLC)的基础上实现高精度、高可靠时间同步成为关键问题。针对上述问题,首先,该文建立基于PLC的智慧园区电力物联网精准时间同步网络模型,根据改进精准时间协议(precision time protocol,PTP)计算同步误差,在此基础上,建立基于数字锁相环的频率偏移补偿模型,降低累积误差;其次,提出站点(station,STA)时间同步误差最小化问题;最后,提出基于经验匹配的电力物联网精准时间同步算法,通过调整时间同步匹配成本,优化STA的时间同步路径选择策略。仿真结果表明,所提方法能有效提高时间同步精度。

Design of a CMOS Adaptive Charge Pump with Dynamic Current Matching

A novel structure for a charge pump circuit is proposed, in which the charge-pump （CP） current can adaptively regulated according to phase-locked loops （PLL） frequency synthesis demand. The current follow technology is used to make perfect current matching characteristics, and the two differential inverters are implanted to increase the speed of charge pump and decrease output spur due to theory of low voltage difference signal. Simulation results, with 1st silicon 0. 25μm 2. 5 V complementary metal-oxide-semiconductor （CMOS） mixed-signal process, show the good current matching characteristics regardless of the charge pump output voltages.

Study on Matching a 300 MVA Motor Generator with an Ohmic Heating Power Supply in HL-2M

A new 300 MVA/1350 MJ motor generator （MG） will be built to feed all of the poloidal field power supplies （PFPS） and auxiliary heating power supplies of the HL-2M tokamak. The MG has a vertical-shaft salient pole 6-phase synchronous generator and a coaxial 8500 kW induction motor. The Ohmic heating power supply （OHPS） consisting of 4-quadrant DC pulsed convertor is the one with the highest parameters among the PFPS. Therefore, the match between the generator and the OHPS is very important. The matching study with Matlab/Simulink is described in this paper. The simulation results show that the subtransient reactance of the generator is closely related to the inversion operation of the OHPS. By setting various subtransient reactance in the simulation generator model and considering the cost reduction, the optimized parameters are obtained as xd＂ = 0.405 p.u. at 100 Hz for the generator. The models built in the simulation can be used as an important tool for studying the dynamic characteristics and the control strategy of other HL-2M PFPSes.