用于冷原子干涉仪激光时序控制的DDS跳频系统设计与实现

为了满足冷原子干涉实验对时序控制的需求,设计并实现了一个基于LABVIEW软件的激光时序控制DDS系统,其工作过程为通过设计的LABVIEW上位机软件输入需要产生的频率和频率间隔时间,ARM芯片根据LABVIEW软件发送来的控制信息实现对射频信号芯片的控制,CPLD芯片用来控制射频信号之间的时间间隔,最后DDS芯片产生与控制信息相对应的射频信号。与目前同类装置相比,系统实现了跳频时间和频率更加精确和工作稳定性更好。经过系统的调试分析以及性能测试,DDS跳频系统能够满足原子干涉仪激光时序控制需求。通过测试DDS装置,DDS装置能够输出准确输出射频频率值,并且射频频率时间间隔能精确到微秒。DDS装置可以有效控制冷原子干涉仪的激光时序,在探询时间为120毫秒且重复率为2.2赫兹的情况下,冷原子重力仪的重力测量灵敏度达到 。     

Nonlinear gain computation for the sheet beam crossed-fieldamplifier

When the RF amplitude in a crossed field device is much smaller than the external DC voltage, the energy exchange between an electron and the wave is given by the change in the potential energy of the electron guiding center. The shift of the beam center of charge follows the space bunching into “spokes” caused by the RF-induced drift. A nonlinear estimate for the gain is derived and applied to the linear format crossed-field amplifier fed by a continuous sheet beam. The adiabatic approximation for the guiding center trajectories in the low gain regime determines the fraction of trapped/streaming particles and the energy exchange for each group. The radiation gain equals the change in the electron potential energy resulting from the shift in the beam center of charge across the anode-cathode voltage. The drift kinetic energy is approximately conserved, opposed to other microwave devices converting kinetic energy into radiation. The theory accounts for the symmetry of the response curve relative to the frequency detuning ω-ω₀, and the flat top near resonance. The analytic predictions agree with the experimental measurements of the gain versus frequency response     

DC and analog/RF performance of C-shaped pocket TFET (CSP-TFET) with fully overlapping gate

A C-shaped pocket tunnel field effect transistor (CSP-TFET) has been designed and optimized based on the traditional double-gate TFETs by introducing a C-shaped pocket region between the source and channel to improve the device performance. A gate-to-pocket overlapping structure is also examined in the proposed CSP-TFET to enhance the gate controllability. The effects of the pocket length, pocket doping concentration and gate-to-pocket overlapping structure on the DC and analog/RF characteristics of the CSP-TFET are estimated after calibrating the tunneling model in double-gate TFETs. The DC and analog/RF performance such as on-state current (I_on), on/off current ratio (I_on/I_off), subthreshold swing (SS) transconductance (g_m), cut-off frequency (f_T) and gain-bandwidth product (GBP) are investigated. The optimized CSPTFET device exhibits excellent performance with high I_on (9.98×10 ^{- 4} A/μm), high I_on/I_off (～ 10¹¹), as well as low SS (～ 12 mV/dec). The results reveal that the CSP-TFET device could be a potential alternative for the next generation of semiconductor devices.     

High performance oscillator with 2-mW output power at 300 GHz

Material structures and device structures of a 100-GHz InP based transferred-electron device are designed in this paper. In order to successfully fabricate the Gunn devices operating at 100 GHz, the InP substrate was entirely removed by mechanical thinning and wet etching. The Gunn device was connected to a tripler link and a high RF(radio frequency)output with power of 2 mW working at 300 GHz was obtained, which is high enough for applications in current military electronic systems.     

Equilibrium profiles for RF-plasma sources with ponderomotiveforces

An analysis is given of the influence of the electron ponderomotive force on the equilibrium plasma profiles of partially ionized, radio frequency discharge sources, The ponderomotive force can be written as a gradient of a potential varying with the square of the RF field in the plasma and is largest for electrons, The impact of this electron ponderomotive force on density and electrostatic potential profiles is demonstrated using a one-dimensional analytic model with supporting numerical solutions and a two dimensional fluid simulation. For nearly collisionless plasmas the ponderomotive force is valid when ω_ce^h/ω<1 where ω_ce ^h is the electron cyclotron frequency due to the RF magnetic field and ω is the RF driving frequency, In processing plasmas with parameters that satisfy this validity criteria, the equilibrium density profiles are weakly modified, For nearly collisionless processing plasmas with parameters such that ω_ce^h /ω>1, the ponderomotive force, is modified by other nonlinear force terms that need to be evaluated     

Characteristics of all-optical 3R regenerators using cascaded second-order nonlinear effect in quasi-phase matched lithium niobate devices

We numerically show that quasi-phase matched (QPM) lithium niobate (LN) devices employing the cascaded second-order nonlinear effect of second harmonic generation (SHG) and difference frequency mixing (DFM) have all-optical decision gate characteristics. The decision gate function is realized by a parabolic transmittance for a low-power region and a limiting characteristic for a high-power region. The limiter function is attributed to the large group-velocity mismatch between the fundamental and second harmonic pulses. This operation principle differs from those of other all-optical 2R (reamplification and reshaping) or 3R (2R and retiming) regenerators that have been proposed in the past. Furthermore, we show that an initial time offset between the signal and clock pulses can improve the output signal power or the switching efficiency of the device. Based on the numerical results, we propose a method for designing all-optical 3R regenerators using the cascade of SHG and DFM in the QPM-LN devices. Following the design method, all-optical 3R operation at the bit rate of 200 Gbps can be achieved using a 1-cm-long waveguide device.     

Dynamic control of light propagation and optical switching through an RF-driven cascade-type atomic medium

We study nonlinear optical behaviors in pulse propagation through a medium consisting of four-level cascade-type cold atoms, where a radio-frequency (RF) field couples upper two-folded levels and double-dark resonances (DDRs) can arise. By numerically solving the coupled Bloch-Maxwell equations for atom and field simultaneously in space and time, we demonstrate dynamic control of light propagation and optical switching in such a four-level atomic medium. The proposed scheme may have potential applications in the design of optical switching and optical storage devices.     

基于AlN声表面波滤波传感器器件的有限元仿真

声表面波器件是一种利用压电材料的压电效应与逆压电效应工作电子器件, 文章首先详细描述了声表面波器件的设计与仿真过程,运用有限元分析的方法分别计算了利用声表面波的 SAW 器件与利用体波的 BAW 器件的性能与各项参数,对相关的器件进行了计算分析,分别用上述方法研究了基于 AlN 薄膜的声表面波器件和悬臂梁结构的体波器件,推导得出了器件的电学导纳与频率之间的关系, 通过分析器件的导纳-频率曲线,推导出器件内部声波的模式以及合适的工作频率,最终得出在 IDT 周期为 8 微米的情况下,SAW 器件的理想工作频率是 0.7-1.95GHz,BAW 器件的理想工作频率在 0.6-3.2GHz 的结果。     

Development and Performance Analysis of a Photonics-Assisted RF Converter for 5G Applications

This article presents a simple, ultra-wideband and tunable radiofrequency (RF) converter for 5G cellular networks. The proposed optoelectronic device performs broadband photonics-assisted upconversion and downconversion using a single optical modulator. Experimental results demonstrate RF conversion from DC to millimeter waves, including 28 and 38 GHz that are potential frequency bands for 5G applications. Narrow linewidth and low phase noise characteristics are observed in all generated RF carriers. An experimental digital performance analysis using different modulation schemes illustrates the applicability of the proposed photonics-based device in reconfigurable optical wireless communications.     

多铁性磁电器件研究进展

多铁性材料可以实现力、电、磁等多物理场之间的相互耦合,在小尺寸、快速响应和低功耗的磁电器件领域具有重要的应用前景.在应用需求的推动下,以具有磁电耦合效应的多铁性材料为基础的磁电器件在设计、微纳加工和性能优化等方面的研究取得了持续的进展.本文简要介绍了基于磁电耦合效应的几种原型器件的最新进展,包括可调谐电感、滤波器、磁电存储器、能量回收器、磁电传感器和磁电天线等,分析总结了各种磁电器件的工作原理及其性能表现,讨论了当前多铁性磁电器件研究所面临的问题和挑战,并提出了改进磁电器件性能的研究方向.     

High optical performance and practicality of active plasmonic devices based on rhombohedral BiFeO3

First principles calculations of electronic and optical properties of multiferroic oxide BiFeO₃ are used in combination with a plasmonic device model of optical switch to show that a BiFeO₃ based device can have much better performance than devices based on existing materials. This arises from the combination of octahedral tilts, ferroelectricity and G‐type antiferromagnetism in BiFeO₃ leading to a strong dependence of the optical refractive indices on the orientation with respect to the polarization. A prototype of a plasmonic resonator with an R‐BFO thin film layer is used as an example and shows excellent switch and modulation responses. The proposed approach provides potential opportunities to develop high performance nanophotonic devices for optical communication.     

Synthesis of hexagonal boron nitride thin film on Pt substrates for resistive switching memory applications

Hexagonal boron nitride (hBN), due to its high reliability as a two-dimensional (2D) dielectric material, has attracted much attention for its potential applications in nanoelectronic devices. Here, the use of radio frequency (RF) magnetron sputtering-grown hBN films to construct hBN-based resistive switching (RS) memory device is reported, and the RS mechanism is deduced. The hBN-based RS memory shows low operating voltage, reproducible write cycles, and long retention time. First-principles simulations further confirm the resistive switching. This work provides an important case to facilitate the future applications of 2D materials in the RS memory.     

Organic second-order non-linear optical materials and devices

Organic second-order nonlinear materials are currently receiving considerable attention for fabrication of frequency mixing and electro-optic devices. In this paper the key concepts in the development of organic nonlinear materials and waveguide device design are introduced. The recent advances in nonlinear waveguides for frequency doubling and electro-optic devices are reviewed.An invited paper     

FPGA-based amplitude and phase detection in DLLRF

The new generation particle accelerator requires a highly stable radio frequency (RF) system. The stability of the RF system is realized by the Low Level RF (LLRF) subsystem which controls the amplitude and phase of the RF signal. The detection of the RF signal's amplitude and phase is fundamental to LLRF controls. High-speed ADC (Analog to Digital Converter), DAC (Digital to Analog Converter) and FPGA (Field Programmable Gate Array) play very important roles in digital LLRF control systems. This paper describes the implementation of real-time amplitude and phase detection based of the FPGA with an analysis of the main factors that affect the detection accuracy such as jitter, algorithm's defects and non-linearity of devices, which is helpful for future work on high precision detection and control.     

KTP倍频器件温度适应性扩展研究

针对目前最常用的KTP倍频晶体, 综合考虑其有效非线性系数和温度半宽度, 采用折中设计有效扩展KTP倍频器件适用温度范围. 对大适用温度范围的KTP倍频器件的设计方法进行了详细的理论分析, 并设计了一种温度半宽度为-20 ℃到50 ℃的KTP倍频器件. 实验结果表明该器件在15 ℃时达到峰值转换效率22.7%, 温度半宽度为70 ℃. 和通常情况下设计的KTP倍频器件相比, 尽管倍频转换效率有所下降, 但显著提高了适用温度范围. 且在温度半宽度高达70 ℃情况下, 其有效非线性系数仍大于LBO, BBO等倍频器件. 该方法对于扩展倍频器件的温度适应性具有普适性.     

用于侦察告警的Bragg声光接收机

针对测频器件的缺陷,提出了利用声光器件对电磁波进行实时测频的设计方案。根据现代光学理论设计了声光频谱分析系统,研制出软硬件设备。通过试验和仿真,达到了对电磁频谱进行实时检测分析的目的。与其他测频器件相比,所设计的系统体积小、耗能少、稳定性好,传递速度快,且易于计算机控制。采用声光器件制成的Bragg声光接收机能够在复杂的电磁环境中同时快速检测出多束射频电磁波,在电子战中有很高的应用价值。     

Electro-Optic Polymer Integrated Optic Devices and Future Applications

Recent developments in electro-optic polymer materials and devices have led to new opportunities for integrated optic devices in numerous applications. The results of numerous tests have indicated that polymer materials have many properties that are suitable for use in high-speed communications systems, various sensor systems, and space applications. These results, coupled with recent advances in device and material technology, will allow very large bandwidth modulators and switches with low drive voltages, improved loss, long-term stability, and integration with other microelectronic devices such as MEMS. Low drive voltage devices are very important for space applications where power consumption scales as the square of the modulator half-wave voltage. In addition, we have demonstrated novel dual polymer modulators for mixing RF signals to produce sum and difference frequency modulation on an optical beam. This novel approach allows the suppression of the modulation at the two input RF signals, and only the mixing signals remain superposed on the optical beam. The dual modulator can be used for various encoding/decoding and frequency conversion schemes that are frequently used for both terrestrial and space communications. Another application of polymer integrated optics is in the field of optical sensing for high-frequency (GHz) electric fields.     

Ultra-low temperature radio-frequency performance of partially depleted silicon-on-insulator n-type metal-oxide-semiconductor field-effect transistors with tunnel diode body contact structures

Radio-frequency(RF) characteristics under ultra-low temperature of multi-finger partially depleted silicon-oninsulator(PD SOI) n-type metal-oxide-semiconductor field-effect transistors(nMOSFETs) with tunnel diode body-contact(TDBC) structure and T-gate body-contact(TB) structure are investigated in this paper.When operating at 77 K,TDBC device suppresses floating-body effect(FBE) as well as the TB device.For TB device and TDBC device,cut-off frequency(f_T) improves as the temperature decreases to liquid-helium temperature(77 K) while that of the maximum oscillation frequency(/max) is opposite due to the decrease of the unilateral power gain.While operating under 77 K,f_T and f_(max) of TDBC device reach to 125 GHz and 77 GHz,representing 8%and 15% improvements compared with those of TB device,respectively,which is mainly due to the lower parasitic resistances and capacitances.The results indicate that TDBC SOI MOSFETs could be considered as promising candidates for analog and RF applications over a wide range of temperatures and there is immense potential for the development of RF CMOS integrated circuits for cryogenic applications.     

Electro-Optic Polymer Integrated Optic Devices and Future Applications

Recent developments in electro-optic polymer materials and devices have led to new opportunities for integrated optic devices in numerous applications. The results of numerous tests have indicated that polymer materials have many properties that are suitable for use in high-speed communications systems, various sensor systems, and space applications. These results, coupled with recent advances in device and material technology, will allow very large bandwidth modulators and switches with low drive voltages, improved loss, long-term stability, and integration with other microelectronic devices such as MEMS. Low drive voltage devices are very important for space applications where power consumption scales as the square of the modulator half-wave voltage. In addition, we have demonstrated novel dual polymer modulators for mixing RF signals to produce sum and difference frequency modulation on an optical beam. This novel approach allows the suppression of the modulation at the two input RF signals, and only the mixing signals remain superposed on the optical beam. The dual modulator can be used for various encoding/decoding and frequency conversion schemes that are frequently used for both terrestrial and space communications. Another application of polymer integrated optics is in the field of optical sensing for high-frequency (GHz) electric fields.     

High frequency shear horizontal plate acoustic wave devices

It has been shown recently that shear horizontal acoustic waves propagating in piezoelectric plates whose thickness h is much less than the acoustic wavelength λ possess a number of attractive properties for use in sensor and signal processing applications. In order to exploit the potential benefits of these waves, however, one needs to fabricate devices on very thin plates. We have developed a suitable fabrication method which can be used to realize devices on such thin plates. In this method, the device is first fabricated on a plate of normal thickness (approximately 500 μm) and the substrate is then lapped from the back side to reduce the thickness. The technique has been utilized to realize devices on plates of thickness less than 70 μm. A shear horizontal plate acoustic wave (SH-PAW) delay line of fundamental resonant frequency greater than 25 MHz and insertion loss less than 7 dB has been realized on a 60 μm thick Y – cut, X – propagation lithium niobate substrate. The device also shows strong response near the third harmonic frequency of 75 MHz.