Microwave-package measurements at the Q band

The elements of the ? equivalent circuit of S4 microwave packages with a range of bond-lead geometries have been measured at the Q band.     

全光纤微型珐-珀干涉式高温传感器

通过在单模光纤SMF28e后有轴心偏移地熔接一段特种光子晶体光纤(MM-HNA-5)制作了一种全光纤微型珐-珀(F-P)干涉仪.分析了这种干涉仪的光学原理和形成机理,并利用MM-HNA-5光纤热光系数较大的特点,将这种干涉仪应用于温度测量.实验结果表明:这种干涉传感器可测量的高温范围可达1 200℃,远大于常规传感器的测量范围,且当干涉腔长为3.46 mm 时,其光程差的温度灵敏度约为103 nm/℃,线性度为O.995 7.可以预见:这种结构稳定、体积小、精度高、测温范围广的全光纤F-P干涉温度传感器在国防及民用工业中将具有极大的潜在应用价值.     

All-fiber interferometer for chromatic dispersion measurements

An all-fiber interferometric method for chromatic dispersion measurements in meter-length single-mode fibers is presented. In a Michelson setup the physical length of a reference fiber was varied so as to obtain adjustable optical delay. Time resolution, ease of manipulation, and mechanical isolation are considerably improved with respect to conventional interferometers. Resolution of group delay measurement and chromatic dispersion over the full 1100-1700-nm spectral range are better than 5 fs and 0.1 ps/nm-km, respectively     

Fizeau fringe interferometer for fibre outside diameter measurements

A simple interferometer for making accurate outside diameter measurements of optical fibre is described. The apparatus, which measures the diameter in terms of Fizeau fringes, is easy to implement, requires minimal alignment and can be constructed from low-cost components. The device has a precision of ±0.03 ?m and an ultimate accuracy of 1 part in 106.     

Q band microwave-biased photoconductive detector

A microwave-biased photoconductive detector operating in a cavity resonant at 36 GHz is described. The potential advantages of working at this high microwave frequency are outlined, and the microwave system is described. A photocurrent gain of 55 is reported, and measurements show that this value is degraded by about 25% at optical-modulation frequencies approaching 1 MHz.     

Q band GaAs Schottky-barrier IMPATT

Microwave power at Q band is reported from GaAs Schottky-barrier avalanche diodes. A nickel-contacted epitaxial GaAs structure in a flipped mesa configuration was used. In a Q band waveguide cavity, 0.5 W was obtained at 26.7 GHz using a pulsed voltage source.     

Two-beam interferometer for optical constants measurements at near-millimeter wavelengths

A simple and versatile instrument for the measurement of optical constants in the near millimeter spectral region is described. Studies of quasi-optical components used in this instrument for effective beam transmission and control are reported. These studies include transmission characteristics of dielectric waveguides and performance of a variable coupler based on frustrated total internal reflection. Operation of this instrument as a two-beam interferometer for determining the index of refraction or as a device to measure transmission for determining the absorption coefficient are described. Values measured with this instrument at 245 GHz, using an optically pumped molecular laser as the source, are reported for several low-loss materials. Appropriate corrections and error estimates are discussed. The potential for improvement and increased accuracies are discussed.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Internal temperature distribution measurements in high powersemiconductor lasers

A novel technique to measure internal temperature distributions within high power semiconductor lasers with substrates transparent to the laser radiation is presented. The temperature resolution is better than 1°C with a spatial resolution of 1-2 μm. The results show highly non-uniform transverse temperature distributions and significant heating close to the facet at high output powers     

Effect of band shapes on carrier distribution at high temperature

This paper indicates both experimentally and graphically how the distribution of carriers changes above a critical temperature Tc, which is related to the density of states ρ in the band tails. Thus,kT_{c} = E_{0}, whererho = rho_{0} exp (DeltaE/E_{0}). The emission spectrum shifts with changing excitation (band filling) at lower temperatures (T < T_{c}) and stays at a constant value independent of excitation at higher temperatures (T > T_{c}). Experimental results of photoluminescence studies with GaAs crystals show that the quantity E0, obtained from the dependence of the peak energy upon the degree of excitation is the same as the quantitykT'_{c}, obtained from the dependence of the peak energy upon temperature. This is in agreements with the analysis. For lasing diodes, the threshold will increase steeply with increasing temperature above Tc, if the excited carriers are located mostly in the exponential states of the band tail.E_{0} = (10 sim 20)meV and Tc= (120 sim 250degK) are typical for crystals of heavily compensated GaAs.     

SiC thin-film Fabry-Perot interferometer for fiber-optic temperature sensor

Polycrystalline SiC grown on single-crystal sapphire substrates have been investigated as thin-film Fabry-Perot interferometers for fiber-optic temperature measurements in harsh temperatures. SiC-based temperature sensors are compact in size, robust, and stable at high temperatures, making them one of the best choices for high temperature applications. SiC films with thickness of about 0.5-2.0 /spl mu/m were grown at 1100/spl deg/C by chemical vapor deposition (CVD) with trimethylsilane. The effect of operating temperature on the shifts in resonance minima, /spl Delta//spl lambda//sub m/, of the SiC/sapphire substrate has been measured in the visible-infrared wavelength range. A temperature sensitivity of 1.9/spl times/10/sup -5///spl deg/C is calculated using the minimum at /spl sim/700 nm. Using a white, broadband light source, a temperature accuracy of /spl plusmn/3.5/spl deg/C is obtained over the temperature range of 22/spl deg/C to 540/spl deg/C.     

Material selection for efficient transferred-electron devices at Q band

A large number of measurements have been carried out on 11 different slices of GaAs and on devices fabricated from these slices. This has made it possible to establish a useful correlation between the impurity profiles of the GaAs slices and the microwave performance of devices fabricated from them.     

室内走廊环境高频段宽带无线信道测量与建模

为了验证在高频段进行宽带无线通信的可行性,介绍了针对室内走廊环境进行的14 GHz宽带无线信道测量和所获取的信道特征。基于频域信道冲激响应测量方法,设计搭建了宽带无线信道测量平台,较好地克服了高频段电波传播能量实时测量采集的难度。基于实测数据提取信道参数化模型,获取了高频段电波传播特性参数统计分析结果,包括路径损耗与阴影衰落、时延扩展、角度扩展。测试与分析结果表明:高频段电波传播时延小、方向性强,适用于宽带互联通信。     

Gunn-diode operation at Q band frequencies

Operation of Gunn oscillators at Q band frequencies is reported. Useful c.w. output powers were obtained and a practical resonant circuit was examined.     

Finline L to Q band upconverter

An L to Q band upconverter using finline configuration is developed. The conversion losses of 9.45±0.35 dB are achieved over 400MHz bandwidth. A more effective 180° hybrid and a planar backshort are used in the finline upconverter.     

气体高温辐射特性窄谱带模型参数库构建

不同推进剂火箭发动机尾焰中主要辐射气体组分不同,采用谱带模型法精确快速求解不同推进剂火箭发动机尾焰红外辐射特性,需要构建描述气体辐射特性的谱带参数数据库。提出了一种谱带参数库构建方法并开发了计算程序,以HITEMP2010数据库为基础构建了波数间隔5 cm-1、温度间隔100 K的CO2和H2O谱带模型参数库,通过与实验测量对比吸收系数分布特性、与逐线计算法对比透过率分布特性验证了所提出模型和开发程序的准确性;在此基础上,分别以HITEMP2010和HITRAN2012数据库为基础构建了辐射气体CO、OH、NO和NO2的谱带模型参数数据库,并结合逐线计算法对比分析了不同温度下、不同光学行程下透过率分布特性。     

Algorithm for large-phase-modulation measurements (fibre optic interferometer systems)

A new algorithm is presented suitable for measurement of large-phase-modulation magnitudes using data from a spectrum analyser. Large-phase-modulation measurements were carried out on piezoelectric-cylinder fibre-optic phase modulators revealing nonlinearity and hysteresis in the response of the device.<>     

A DCN laser interferometer for electron density measurements of plasmas

The main characteristic of this interferometric system is such that the systems can be used for DCN laser (λ=195μm, 190μm) and also for HCN laser (λ=337μm) by changing the work medium, regulating the temperature of tube wall and adjusting the optic path, without changing any optic element.     

Submillimeter laser interferometer for high density plasma diagnostic

There are presented the results of investigation of the one-channel homodyne laser interferometer λ=119 µm made on the basis of the hollow dielectric beamguide and quasioptical functional devices. The interferometer is designed for determination of the plasma electron density of the TOKAMAK-7. The density response threshold is 0.7% from the expected plasma density and the phase difference measurement total error is 5°     

一种确定高窄带滤光片峰值波长的方法

本文介绍一种主动式高窄带滤光片峰值波长的测量方法。该方法可以有效的测量出窄带滤光片的敏感波长，而不需要太复杂的设备。通过染料激光谐振腔的模式竞争，可以测量出滤光片的透射或反射波的波长。