Discrete correlation processor as a building core of a digital optical computing system: architecture and optoelectronic embodiment

In this paper we present a general-purpose discrete correlation processor (DCP) expected to be the building core block of a digital optical computing system. The DCP-1 is embodied by optoelectronic devices such as a VCSEL and a complementary metal-oxide silicon photodetector. The application targets of the DCP-1 are optical interconnection and various types of digital optical computing. It is expected that digital optical computing techniques coupled with the optoelectronic technology will provide large capability and flexibility in information processing. Introduction of a processing scheme of optical array logic enlarges the applicable field of the DCP-1 as well as its processing capability. With the experimental DCP-1 a bit error rate smaller than 10(-9) was obtained for A . B? operation under a 500-kHz clock rate.     

Transportable optical frequency comb based on a mode-locked fibre laser

A new transportable frequency comb has been developed at the National Physical Laboratory. The transportable frequency comb is based around a MenloSystems FC1500 optical frequency synthesizer, which is capable of measuring any frequency between 500 and 2100 nm. Measurements made by the comb while off-sites are referenced to the SI second via a global positioning system (GPS)-disciplined Rapco 2804AR rubidium oscillator. All components of the system (except for the GPS antenna) have been integrated into a single mobile unit. Measurements of high-stability narrow-band optical sources using this system, with either the GPS-disciplined oscillator or a hydrogen maser as a reference, are described. Some of these measurements were made simultaneously with a hydrogen-maser-referenced Ti:sapphire-based comb. It was found that the GPS-referenced transportable comb has a fractional inaccuracy of better than 4 10^-12 (averaged over several hours) when compared with the maser-referenced Ti:sapphire comb, and a fractional frequency instability of 1times10^-12 for an averaging time of 10 s. It was also demonstrated that continuous frequency measurements are possible with this system over a period of 60 h or more.     

Super high resolution for long-range imaging

A new optical system with a resolution that is superior to the resolution of the usual optical systems with diffraction limit is presented. We introduce a newly generated narrow light beam that propagates for a long range while almost maintaining its beam width and show that the beam width is narrower than that of the diffraction limit of normal optics. Thus a super high resolution is achieved for a long range, e.g., a range of a few kilometers, by the use of a 10-cm-diameter telescope. The high resolution for long-range imaging can be obtained by a Galilean telescope with a negative eyepiece that has a spherical aberration. We demonstrate theoretically high-resolution imaging by using simple objects and assuming a telescope 10 cm in diameter and a visible wavelength. A comparison of simulation results by the conventional optical system and by the special optical system clearly shows the superiority of the new system.     

Development of an ultrastable fiber optic frequency distributionsystem using an optical delay control module [for frequency standard andVLBI]

An ultrastable fiber optic frequency distribution system is described. The ultrastable phase stability is achieved by configuring a closed phase-locked loop with a single-mode optical fiber transmission line in which two optical carrier signals with different wavelengths are transmitted as a forward and a backward signal, and installing an optical delay control module which has no differential dispersion effect between the two optical carrier waves and induces no electrical noise. A phase stabilized optical fiber (PSOF) is used for the signal transmission line. The stabilities of this system are 7.5×10^-17 and 1.1×10^-17 in Allan standard deviation at 1000 and 10000 s averaging time, respectively, while the environmental temperature of the PSOF cable varies as much as the range of 10°C and the rate of 10°C/12 h     

The central pixel of the MAGIC telescope for optical observations

The MAGIC telescope has been designed for the observation of Cherenkov light generated in Extensive Air Showers initiated by cosmic particles. However, its 17 m diameter mirror and optical design makes the telescope suitable for direct optical observations as well. In this paper, we report about the development of a system based on the use of a dedicated photo-multiplier (PMT) for optical observations. This PMT is installed in the centre of the MAGIC camera (the so-called central pixel). An electro-to-optical system has been developed in order to transmit the PMT output signal by an optical fibre to the counting room, where it is digitized and stored for off-line analysis. The performance of the system using the optical pulsation of the Crab nebula as calibration source is presented. The time required for a 5σ detection of the Crab pulsar in the optical band is less than 20 s. The central pixel will be mainly used to perform simultaneous observations of the Crab pulsar both in the optical and γ-ray regimes. It will also allow for periodic testing of the precision of the MAGIC timing system using the Crab rotational optical pulses as a very precise timing reference.     

平面光学元件平面度动态干涉拼接测量

开展了基于动态干涉仪的平面光学元件平面度干涉拼接测量,并研究了影响测量和拼接的主要误差。用二级减振的方法来抑制环境中振动的影响;根据允许的变化条纹数来控制二维移动平台导轨精度。建立了以ZYGO公司的DynaFiz干涉仪为子口径采集仪器的干涉拼接系统,开展了单口径平面度测量及拼接实验,完成了200mm×300mm 平面光学元件的平面度测试,并与大口径干涉仪所测试的全口径测量数据进行比对,拼接结果的10次实验均方差为0.001λ(λ=632.8nm)。     

Vibration transducer using an ultrashort Fabry-Perot cavity

We report here on the development of an optical transducer for mechanical vibration, making use of an ultrashort Fabry-Perot cavity. The noise level measured by a cavity 150 μm long is ~1.3 × 10(-16) m/√Hz at ~1 kHz, which was obtained without a frequency-stabilization system. It was, however, large compared with the shot noise.     

Sequenced, dual-pulse TEA N2-laser for opticaldiagnostics

A simple spark gap is incorporated into a subnanosecond TEA N₂ laser system for generating sequenced, dual-pulse output. The time interval between the two laser pulses can be varied from about 10 to over 100 ns. This makes the system very suitable for optical diagnostics of fast transient plasmas. It provides a cost-effective alternative to electrooptic-based systems     

Wavefront sensor based on varying transmission filters: theory and expected performance

The use of wavefront sensors (WFS) is nowadays fundamental in the field of instrumental optics. This paper discusses the principle of an original and recently proposed new class of WFS. Their principle consists in evaluating the slopes of the wavefront errors by means of varying density filters placed into the image plane of the tested optical system. The device, sometimes called ‘optical differentiation WFS’ is completed by a digital data-processing system reconstructing the wavefront from the obtained slopes. Various luminous sources of different wavelengths and spectral widths can be employed. The capacities of the method are discussed from the geometrical and Fourier optics points of view, then by means of numerical simulations. It is shown that the ultimate accuracy can be well below λ/10 and λ;/100 peak-to-valley (PTV) and RMS respectively, provided that certain precautions are taken.     

新型光缓存器及2×622Mb／sATM光交换系统

给出了一种新型的光缓存器的结构，以解决在ＡＴＭ光交换中的信元碰撞问题。这种缓存器是由光纤延迟线、光波导开关阵及非线性半导体光放大器构成。文中还报告了一种用于交换各用户不同速率的信元（可达６２２Ｍｂ／ｓ）的ＡＴＭ光交换实验系统，系统的总容量为了１．２Ｇｂ／ｓ。     

A calorimeter for μW level optical power transfer standard

A calorimeter which can measure microwatt-level optical power has been developed for an optical power transfer standard. It can measure the optical power of a light beam and can be used with optical fiber simply by attaching an adapter. This calorimeter sensor uses a compensative absorber to reduce the influence of pressure fluctuation and temperature variation in the measurement room and an ultra-low-noise preamplifier. With this calorimeter, the standard deviation of the measured value is in the range of 0.02-0.4% in 20-mW to 10-μW optical power measurements. An error evaluation for an optical power level of 10 μW yielded a two-sigma (two standard deviation) total uncertainty of 0.9%     

Discrimination of optical sources by use of adaptive blind source separation theory

Optical systems based on rotating reticles were invented to determine the polar coordinates of a primarily IR optical source. Such systems fail when several optical sources are present in their field of view simultaneously. It is demonstrated experimentally that this drawback can be overcome by the application of a blind-signal-separation algorithm on the output signals of a modified optical system. The separation of the modified optical system responses into independent components yields modulating functions that carry information concerning the polar coordinates of the corresponding single optical sources.     

Design and implementation of optical system for Placido-disc topography

Corneal topography provides powerful support in the diagnosis and treatment of corneal disease by displaying the corneal surface topography in data or image format. To realize the precise detection of corneal surface topography, an optical system for the corneal topography that is based on a Placido disc is designed, which includes a ring distribution on a Placido disc, an imaging system and a collimating illumination system. First, a mathematical model that is based on the corneal topography working principles is established with MATLAB to determine the distribution of white-and-black rings on the Placido disc, in which the ellipsoid facial rings-target of the Placido disc is utilized. Second, the imaging lens structure is designed and optimized by Zemax software. Last, the collimating illumination lens structure is designed by paraxial ray trace equations. The quality of the corneal topography, which is based on our designed optical system, is evaluated. The high-contrast image of uniformly distributed white-and-black rings is observed through the CCD camera. Our optical system for the corneal topography has high precision, with a measuring region of the cornea with a diameter of approximately 10 mm. Therefore, the creation of this optical system offers guidance for designing and improving the optical system of Placido-disc topography.     

An MCM-Based Microsystem for Colorimetric Detection of Biomolecules in Biological Fluids

This paper presents a multichip module microsystem for biological fluid analysis. It is composed of three parts, namely 1) CMOS silicon optical detection microsystem, which includes a photodetector and a light-to-frequency converter for readout; 2) dielectric thin-film-based optical filter on top of the photodetector fabricated using IC-compatible postprocessing; and 3) glass die on top containing the microchannels fabricated using SU-8 techniques. The application is in low-cost quantitative measurement of the concentration of biomolecules in biological fluids. Its operation is based on optical absorption in the part of the visible spectrum that is defined by the specific biomolecule. Signals proportional to the intensity of the light transmitted through the biological fluid are available at the output in the form of bit streams, which allows simple computer interfacing. The quantitative measurement of the total protein in urine is successfully demonstrated. The photodiode responsivity is 224 mA/W with a full-width at half-maximum of 10 nm at$lambda = 600 hboxnm$. The optical system sensitivity is 1$hboxkHz/W m^-2$at$lambda = 670 hboxnm$.     

First-order optical systems with unimodular eigenvalues

It is shown that a lossless first-order optical system whose real symplectic ray transformation matrix can be diagonalized and has only unimodular eigenvalues is similar to a separable fractional Fourier transformer in the sense that the ray transformation matrices of the unimodular system and the separable fractional Fourier transformer are related by means of a similarity transformation. Moreover, it is shown that the system that performs this similarity transformation is itself a lossless first-order optical system. Based on the fact that Hermite-Gauss functions are the eigenfunctions of a fractional Fourier transformer, the eigenfunctions of a unimodular first-order optical system can be formulated and belong to the recently introduced class of orthonormal Hermite-Gaussian-type modes. Two decompositions of a unimodular first-order optical system are considered, and one of them is used to derive an easy optical realization in more detail.     

Chip-scale universal detection based on backscatter interferometry

An on-chip detector based on backscatter interferometry has been developed to perform subnanoliter-volume refractive index measurements. The detection system consists of a simple, folded optical train based on the interaction of a laser beam and an etched channel, consisting of two radii joined by a flat portion, thus defining a curved surface in the shape of a hemisphere in a silica (glass) plate. The backscattered light from the channel takes on the form of a high-contrast interference pattern that contains information related to the bulk properties of the fluid contained within the probe volume. Positional changes of the interference pattern (fringes) allow for the determination of deltan at the 10(-6) level, corresponding to 743 microM or 139 x 10(-15) mol or 12.8 x 10(-12) g of sucrose, in a probe volume of only 188 x 10(-12) L. A theoretical model of the on-chip backscatter interferometric detector has also been developed, evaluated, and found to be in agreement with experimental data. It is shown that the model can be used to predict general system performance for changes in the optical train such as the chip's wall thickness and channel diameter.     

空间光通信系统的设计及实现

提出一种较全面的空间光通信系统结构。该系统的光发射接收子系统采用三发三收的设计方法,以增大光的发射功率和接收功率;APT子系统采用望远镜进行粗瞄准,音频调制光标信号进行精瞄准;控制子系统采用Ethernet接口,远程通过Internet对系统进行测量和控制的设计方法。给出一个近地大气空间光通信系统的设计实例, 其信号传输速率为155Mbps,传输距离为4km,在误码率不大于10-9条件下,系统接收灵敏度达到-52dBm。     

光纤频率传递的链路不对称性分析

基于光纤的频率传递在时频同步体系的构建与应用中占据着重要地位。为了在射频稳相传输系统中定量研究由于温度不对称和波长不对称所引入的延迟波动和色散残余等因素对系统稳定性的影响,使用光学仿真软件搭建了简易频率传递系统与3 000 km光纤链路进行10 GHz射频信号传递的仿真分析。通过分析发现链路中引入的温度不对称对系统频率稳定性影响较小,而波长不对称所导致的影响较大,随着正反向波长的差异增大,系统频率稳定性恶化量级在10^-13/ s以上。此研究分析对实际环境下的长距离光纤频率传递系统的建设及优化具有实际指导作用。     

Optical effect of diffractive multifocal focusing of radiation on a bicomponent diffraction system

It is shown for the first time, to our knowledge, that when a plane wave illuminates a certain type of bicomponent optical system, consisting of two plane screens with circular apertures on a given optical axis, a multifocal diffractive focusing effect can appear. Here the diffraction picture in the focal planes represents the circular nonlocal bands of the Fresnel zones with a bright narrow peak at the center, whose intensity can exceed by 6-10 times the value of the incident-wave intensity. The detected optical effect is observed across a wide range of wavelengths, lambda = 0.4-10(3) mum, and ratios of the aperture diameters d(1) >/= 2d(2) = 25-1000lambda, and it is also insensitive to changes in the medium of the wave propagation. For the large diameters of input holes, d(1) = 2d(2) > 100lambda, or for wavelengths in the radio-frequency region of the spectrum, the bicomponent diffraction system acts as a long-focus lens with a high-intensity Gaussian distribution of radiation, at times exceeding the initial intensity, persisting at large distances (z = 1-100 cm) from the diffraction system.     

Differential optical absorption spectroscopy system used for atmospheric mercury monitoring

A high-resolution differential optical absorption spectroscopy (DOAS) system for long-path atmospheric pollution monitoring is described. The system, consisting of a broadband lamp and a dispersive, fast-scanning optical receiver, separated by a few kilometers, was used in measurements of different pollutants, highlighted by the monitoring of the local concentration of atomic mercury. Mercury levels in the ppt (1:10(12)) range were assessed by comparisons with laboratory measurements.