应用于光遗传的双光通道32记录点植入式光电极

光遗传(Optogenetics)结合光学和遗传学手段,可以精确地控制特定神经元的活动,为神经科学的研究提供了强有力的手段.光电极在光遗传研究中起着关键的作用,它可以将光导入到动物体内,并通过电极记录神经元在光调控下的活动.为了减小体积、增加功能,依托高密度集成硅微电极和裸光纤,设计并制备了一种植入部分横截面尺寸不超过0.1 mm2、包含2个平行的给光通道和32个记录点的光电极器件.与传统的单光通道电极相比,两个通道可以更灵活地配置不同的激发波长,对不同位点的神经元同时进行激活或抑制.32通道的硅电极与传统的金属丝电极相比,集成度更高,能够以更高的空间分辨率记录神经元在激发前后的活动情况.     

脑机接口技术的基础研究：神经元与二极管

随着微电子学与光电子学进入“后摩尔时代”，高性能光电器件与生物系统的融合逐渐成为一个重要的发展方向。采用高性能半导体光电器件和系统解决神经科学领域面临的技术难题，尤其是借助光学、电学等手段对神经信号进行调控和传感，受到了越来越广泛的关注。本综述论文以电子工程领域的基本单元之一——二极管与神经科学领域的基本单元——神经元之间的相互作用为切入点，总结了本课题组近年来的代表性研究工作。通过对材料器件进行设计和加工，实现了生物相容的植入式光电器件。这些光电器件通过光电信号的转换与神经信号相互作用，可以实现对生物细胞、组织和活体系统的光遗传学调控、无线光电刺激、原位荧光检测和光电传感等功能。这些新型的光电器件技术对于基础神经科学研究和神经疾病诊疗都具有重要意义。     

对NpHR光敏感蛋白具有刺激作用的光电极研制

光电极是研究光遗传学不可或缺的工具之一。波长为460nm的蓝光可以对ChR2神经蛋白产生刺激,而波长为580nm的黄光可以刺激NpHR神经蛋白,对生物体的反应产生抑制。目前,蓝光波段的光电极具有很高的功率密度,可以满足光遗传学的研究,而黄光波段半导体发光器件的发光效率较低,因此对黄光波段的光电极研究较少。在蓝宝石衬底蓝光光电极研制的基础上,通过激发黄色荧光粉和量子点两种形式获得黄光,并通过沉积SiO2/TiO2分布式布拉格反射镜（DBR）有效滤除了蓝光波段的激发光,最后通过沉积Ag金属反射镜增强黄光信号,制备出荧光粉基和量子点基黄光光电极。与荧光粉基黄光光电极相比,量子点基黄光光电极具有更高的功率密度、更窄的光谱半宽和更薄的厚度。在1～10mA的注入电流下,量子点基黄光光电极的功率密度为4.46～15.37mW/mm2,满足刺激NpHR神经蛋白的要求。     

基于光控蛋白质相互作用的光遗传学技术及其应用

光遗传学技术是一种新型的生物技术,融合了光学及遗传学技术,可以实现光对细胞活动的控制。在光遗传学应用当中,靶向细胞可用基因来改造和表达光敏蛋白质,并可被光所调控。光遗传学技术利用光敏离子通道蛋白对特定神经细胞进行精准、快速的光控,已经掀起了神经科学研究领域的一场革命。除了光敏离子通道之外,能产生蛋白质相互作用的光敏蛋白也已被广泛应用于光遗传学研究。本文讨论了常见的基于蛋白-蛋白相互作用的光敏蛋白,然后介绍了基于光控蛋白-蛋白相互作用的光遗传学技术在光控基因表达、相分离、代谢工程和细胞器运输中的应用。     

多量子阱光开关器件的激子吸收及光调制特性

我们分析了 Ga As/Al Ga As半导体多量子阱 (MQW)光开关器件的室温激子吸收行为及光调制特性 ,优化设计了多量子阱结构 ,研制出常通型和常关型两种类型光开关器件 ,并对器件的光调制特性进行了测量与研究。实验得出的结论与理论计算相符合 ,常通型器件对比度约为 10∶ 1;常关型器件对比度约为 4∶ 1。     

侧向注入的载流子注入型SOI光开关中的热效应分析V

根据热场方程,分析了侧向载流子注入pin结SOI脊波导器件中的热光效应影响,数值分析和实验现象表明,在该类电光子器件中,载流子注入产生的热光效应影响明显,尤其对于SOI材料的小截面脊波导结构。如1000微米调制长度的器件,在正常工作时,温升引起的折射率上升已占总的效应的1/8;同时提出了通过调整电极位置来进行散热的减小热光效应影响的方案。     

数字微镜器件的时空特性

数字微镜器件是一种新型的微电子、微机械、微光学集成器件，可广泛的用于大屏幕投影显示。实际上，数字微镜器件作为一种新型的空间光调制器，在光学信息处理和结构照明型三维传感中也具有广泛的应用前景。本文介绍了数字微镜器件和数字光处理器的基本原理，分析这种器件的时间空间特征，讨论了这种时空特性对结构照明型三维传感应用的影响。本文还给出了反映这种时空特性的实验结果。     

宽带光波导调制器的研究

宽带光波导调制器是光纤通信系统中重要器件之一。本文分析了Ｍ－Ｚ干涉型光波导调制器的工作特征，研究了集总参数型电极的带宽特性，在ＬｉＮｂＯ３基片上设计制作了光波导调制器并测量了主要参数。     

光可变衰减器的研究进展

光可变衰减器(VOA)作为波分复用(WDM)网络中关键的功率管理器件,能够实现信道均衡和自动增益控制功能.微电机械系统(MEMS)型和热光型VOA以其衰减范围宽、功耗低、体积小、易于集成等优点成为研究重点,热光特性极佳的聚合物材料则成为最引人注目的热光材料.文章对已有的VOA器件作了概括分类,介绍了各种MEMS型VOA,还从热光材料的角度,总结了聚合物材料的研究成果,对已见报道的基于聚合物的各种热光型VOA进行了重点的描述和分析.最后给出了VOA的两种网络实例.     

半导体双稳态激光器在光注入下的实验研究

本文报道了InGaAsP/InP 双区共腔脊形波导双稳激光器在外光注入下产生光-光双稳特性及光-光放大的实验结果,给出了器件在直流及脉冲工作时的光-光双稳特性,并对结果进行了初步分析.     

A new optrode design for intramural optical recordings

Intramural measurements of V(m) and Ca(i)(2+) are important in the studies of cardiac arrhythmias and defibrillation. We developed a new design of an "optrode" (bundle of optical fibers) for use in intramural cardiac mapping. The optrodes are made from seven optical fibers with the fiber ends polished at 45° angle and coated with mirror surfaces. The optrodes are enclosed in smooth epoxy resin cast, which protects mirror surfaces from damage and ensures constant optrode diameter along its length. The optrodes are strong enough to be easily inserted into heart muscle, can be reused multiple times, and they may reduce artifacts in the measurements of the effects of defibrillation shocks on V(m).     

A signal detection system based on Dempster-Shafer theory andcomparison to fuzzy detection

This paper describes a signal detection algorithm based on Dempster-Shafer theory. The detector combines evidence provided by multiple waveform features and explicitly considers uncertainty in the detection decision. The detector classifies waveforms as including a signal, not including a signal, or being uncertain, in which case no conclusion regarding presence or absence of a signal is drawn. The probability numbers required in the Dempster-Shafer formulation are defined as piecewise linear functions that can be described by two parameters, and the effects of these parameters on detector performance, using simulated data, are compared to Bayesian detection and to a fuzzy signal detector that also considers uncertainty. The performance of the Dempster-Shafer and fuzzy detectors shows similar dependence on the parameters, although, if parameters are adjusted so that the number of correctly classified waveforms are equal, the Dempster-Shafer detector has more uncertain classifications and fewer errors than the fuzzy detector, providing superior performance. The Dempster-Shafer detector incorporates a different type of uncertainty than the fuzzy detector, which may contribute to this difference in performance. The difference may also reflect the different mathematical operations used     

The tripole antenna: An adaptive array with full polarization flexibility

The performance of an adaptive array using three mutually perpendicular dipoles (a "tripole") is studied. A desired signal and an interference signal, each with arbitrary angle of arrival and polarization, are assumed incident on the array. Uncorrelated thermal noise is also assumed present on each element signal. The output desired signal-to-interference-plus-noise ratio (SINR) is computed as a function of the signal arrival angles and polarizations. It is shown that for most angles of arrival and polarizations, the array has an excellent ability to protect a desired signal from interference. Certain special cases where the performance is not good are discussed in detail.     

Performance analysis of a class of transient detection algorithms-aunified framework

The detection of short-duration nonstationary signals, which are commonly referred to as transients, is often performed in the time-frequency-transform domain. An analytical framework within which the performance of different detectors based on linear transforms can be easily compared, for different classes of signals, is developed. A given class of transients is modeled as a signal existing in a linear subspace, plus a mismatch signal. Closed-form expressions are derived for the best and the worst detection performance for all possible transients in a given class. Using this framework, the performance of detectors based on the Gabor transform and on the short-time Fourier transform is evaluated and compared     

Energy-Adaptive Signal Processing Under Renewable Energy

This paper presents an energy-adaptive performance management technique for the design of embedded signal processing systems powered by renewable energy sources. By jointly considering the non-deterministic characteristics of renewable energy and the unique relationship between signal processing performance and the required energy consumption, a progressive performance tuning approach is developed to dynamically determine an acceptable signal processing performance in accordance with the changing energy level at runtime. Several practical issues such as energy prediction errors and battery capacity are investigated, and their impacts on the proposed technique are evaluated. The proposed technique is applied to a DCT-based image sensing system. Simulation results demonstrate that by adaptively tuning signal processing kernels with renewable energy, significant improvements in time coverage and energy efficiency can be achieved in the presence of unstable harvested energy.     

Robust adaptive beamforming for general-rank signal models

The performance of adaptive beamforming methods is known to degrade severely in the presence of even small mismatches between the actual and presumed array responses to the desired signal. Such mismatches may frequently occur in practical situations because of violation of underlying assumptions on the environment, sources, or sensor array. This is especially true when the desired signal components are present in the beamformer "training" data snapshots because in this case, the adaptive array performance is very sensitive to array and model imperfections. The similar phenomenon of performance degradation can occur even when the array response to the desired signal is known exactly, but the training sample size is small. We propose a new powerful approach to robust adaptive beamforming in the presence of unknown arbitrary-type mismatches of the desired signal array response. Our approach is developed for the most general case of an arbitrary dimension of the desired signal subspace and is applicable to both the rank-one (point source) and higher rank (scattered source/fluctuating wavefront) desired signal models. The proposed robust adaptive beamformers are based on explicit modeling of uncertainties in the desired signal array response and data covariance matrix as well as worst-case performance optimization. Simple closed-form solutions to the considered robust adaptive beamforming problems are derived. Our new beamformers have a computational complexity comparable with that of the traditional adaptive beamforming algorithms, while, at the same time, offer a significantly improved robustness and faster convergence rates.     

高精度测速设备动态目标模拟研究

针对基于动态目标模拟方法,检验和考核高精度测速设备性能,训练操作手的实战水平,提出了一种基于高精度测速设备理论弹道的动态模拟方案,通过对预先提供的理论弹道文件,进行插值、坐标转换和中频模拟等步骤,解算出理论弹道文件中包含的信号电平、多普勒频率和目标位置等信息,并据此产生中频模拟信号[1,2]。模拟信号作为动态模拟信号送给高精度测速设备,用于检验和考核设备性能,训练操作手的实战水平。利用理论弹道数据产生高精度测速设备的动态模拟数据,具有精度高、贴近实战的特点。     

Phase Compensation Receivers for Optical Communication

Phase compensation receivers are investigated in the context of optical communication, with particular emphasis on low visibility channels. It is shown that phase compensation can be viewed as a reduction of the number of spatial modes in the signal field so that an improvement in communication performance can be realized by a receiver which exploits the spatial coherence of the compressed signal mode. The phase compensation receiver structure separates nicely into configurations for measuring the phase of the signal field across the aperture and the required processors to obtain the phase compensation control from the measurements. The optimum phase control, which is chosen to spatially concentrate the signal power in the focal plane, is shown to be the minimum-mean-squared-error estimate of the aperture field phase, when the estimation error is "small enough." The phase observation-estimator structures are placed in an idealized phase compensated receiver. Minimum signal power requirements for adequate phase estimation performance are established. Communication performance, in terms of the parameters that describe the low visibility channel, is examined for both compenstated and uncompensated receivers. Depending on the system used, and for phase coherence times in the tens of milliseconds, phase compensation is most appealing for signaling rates from the middle kilobit to low megabit per second range; the resulting improvement in communication performance made possible by phase compensation is as much as 40-60 dB in optical power relative to an uncompensated receiver.     

Demod-Remod Coherent Tracking Receiver for QPSK and SQPSK

A demod-remod coherent tracking loop for QPSK and SQPSK is described and analyzed. This type of receiver is attractive since all of the available signal power is despread and used to generate the tracking error signal when the pulses reaching the nonlinearities are rectangular. The same demod-remod circuit is widely used for bandlimited pulses, for which less than full power is converted to the carrier phase error signal. All system parameters pertinent to system performance are enumerated. The effects of the IF and arm filters on the statistics of the noise are determined. With respect to the signal, the filters are considered only insofar as they reduce the delivered signal power. It is demonstrated how a tracking phase error converts some of the signal power into additional noise power. The results of performance computation are presented.     

超宽带信号与常规通信信号的共存性研究

文章简要介绍了脉冲式超宽带信号对GPS系统的影响,以及脉冲式超宽带信号、直接序列超宽带信号、MB-OFDM信号对卫星数字接收机性能的影响,特别分析了不同的信号特征对这些系统干扰的相关性,为了提高系统频率的利用效率,并保证潜在的其他通信系统的性能,超宽带设备需要具有干扰的检测和避让的技术能力。