Optical fibres coated with a UV-curable material at a speed of 12 m/s

The letter reports the successful achievement of coating silica fibre at a rate of greater than 10 m/s. We draw 125 ?m-diameter fibres from silica rods and preforms, and coated in-line with UV-curable material. All fibres were proof-tested at two different stress levels of 0.7 and 1.4 GN/m2 We also checked the transmission properties of the fibre. It is found that the optical properties of the fibre remain the same while the mechanical properties are comparable to those of the fibres coated at a low speed.     

炭基/锌掺杂铁磁体复合材料制备及其消光性能研究

为了实现抗红外烟幕高效环保的要求,同时实现质轻、宽波段吸波性能,采用一步水热法制备了炭基-锰锌铁氧体/镍锌铁氧体/钴锌铁氧体复合材料的前驱体,并在500~900 ℃的温度区间进行焙烧得到了炭基/锌掺杂铁磁体复合材料。通过X射线粉末衍射仪（XRD）、傅里叶红外光谱仪（FT-IR）、扫描电子显微镜（SEM）等表征方法,分析了复合材料的物相和形貌。根据朗伯比尔定律,采用傅里叶红外光谱仪的KBr压片法测试并计算了各材料在2.5~25 μm区间的红外消光系数,并且研究了焙烧温度对材料消光性能的影响。研究结果表明:炭基/锌掺杂铁氧体前驱体焙烧后生成的炭基/锌掺杂铁磁体复合材料的红外消光性能均有所增强,经过700 ℃焙烧后的炭/钴锌铁磁体红外消光系数最大,为0.25 m2/g,具有较好的红外消光性能。     

Low-OH-content fibre fabrication using particle-size control sol-gel method

By the sol-gel method using a new `particle-size control? technique, a low-OH content at a level of 0.1 parts in 106 and a minimum optical loss of 1.8 dB/km at 1.6 ?m wavelength has been achieved in pure silica core single-mode optical fibres. Improvement of dry gel properties using particle-size control is essential to bubble-free fibre drawing form dehydrated gel-derived glasses.     

Improved electrical and thermal properties of InP-AlGaAsSb Bragg mirrors for long-wavelength vertical-cavity lasers

The electrical, thermal and optical properties of n-doped InP-AlGaAsSb 1.5-/spl mu/m Bragg mirrors are reported. A voltage of 10 mV per pair at 1 kA/cm/sup 2/ has been obtained in these mirrors, due to a low conduction band offset. This record electrical performance, combined with a large refractive index contrast (n/sub H//n/sub L/=1.135) and improved thermal properties, makes the combination very promising for long wavelength vertical cavity surface emitting lasers.     

Ideal GaP surface-barrier diodes

The properties of GaP diodes with metal?semiconductor (m.s.) potential barriers are described. The structure was manufactured by the chemical deposition of metal (gold or metal) on the n GaP surface. The properties of these m.s. structures (forward current/voltage and photocurrent/photon-energy characteristics and typical parameters) are extremely close to an ideal theoretical model. Comparison of properties of the m.s. structures with properties of the best GaP structure made by vacuum evaporation shows that the method of chemical deposition which is more simple permitted she manufacture of more perfect m.s. structures.     

基于谐衍射特性的红外双波段光学系统设计

基于谐衍射光学元件的成像理论,将谐衍射透镜应用在传统红外单波段系统里,设计得到工作波段处于4.4～5.4μm和7.8～8.8μm的红外双波段光学系统。分析了谐衍射光学元件的特性,计算了光学系统的结构参数,并利用软件的多重结构进行了优化。设计结果表明,系统的光学传递函数在两个波段范围内,20 lp/mm时的归一化值均大于0.5,具有良好的成像质量。为红外光学系统的设计提供了一种全新器件。     

Epitaxial liftoff microcavities for 1.55-μm quantum-well spatiallight modulators

Microcavities operating at 1.55 μm have been realized according to the epitaxial liftoff (ELO) technique. The process is described and characterized. No significant variation of the optical properties of the grafted devices has been found. The technique is then applied to a spatial light modulator made by inserting a 3-μm multiple-quantum-well device in a short asymmetric Fabry-Perot microcavity. An enhancement by a factor 1000 of the performances of the switching component is obtained. The input diffraction efficiency reaches 2% in a degenerated four wave mixing configuration with a pulse energy of 1 μJ/cm² and without any applied electric field     

Pulsed laser-induced melting of precision diamond- machined Cu, Ag, and Au at infrared wavelengths

Threshold for characteristics of pulsed laser-induced damage have been measured on precision diamond-machined Cu, Ag, and Au surfaces at 10.6, 3.8, 2.7, and 1.06 μm wavelengths. Pulse lengths range from 2 μs to 9 ns, and focal spot diameters range from 238 to 52 μm. Comparison is made with melt thresholds calculated from one-dimensional heat flow considerations with a spot-size correction. The calculation incorporates waveform shape, as well as temperature-dependent absorption and thermal properties. Agreement is excellent for Ag, except at 1.06 μm, while agreement for Cu and Au is good only at 10.6 μm. Results suggest that disturbance of crystalline surface order has an important influence, especially at wavelengths shorter than 10.6 μm. A singular departure from calculated Cu and Au thresholds at 3.8 μm, using a multipeaked waveform, may have important implications for repetitively pulsed applications. For Cu at 10.6 μm, damage scales with pulse length according to thesqrt{tau}law provided the pulse length as appropriately defined.     

Nd:LiNbO3laser

Laser action at 1.0845 μm is demonstrated in a neodymium-doped LiNbO3crystal pumped by 0.7525-μm krypton laser, which happens to coincide with a Nd absorption line. Although LiNbO3is a good laser host, with good electrooptic and acoustooptic properties, laser damage limits its applicability at present unless one is willing to maintain the crystal at 165°C.     

Preparation and Properties of C—axis Oriented PT／PEK—c Films

The preparation of PT/PEK-c films is reported as well as their dielectric and optical properties.The c-axis orientation ratio of the films is 68%.Dielectric constant and loss factor at 10kHz is about 4.023 F/m and 0.003, respectively.The refractive indices of the films,ne and no, are 1.6573 and 1.6278 at 0.63μm wavelength, respectively.The optical band-gap of the film with a thickness of 2.33μm is found to be 3.06eV.     

适用于光纤放大器的Er3 -Yb3 共掺双包层光纤

研制出一种适用于光纤放大器的Er^3＋-Yb^3＋共掺双包层光纤（EYDCF），它在980nm和1530nm的吸收分别达到16．8dB／m和20．6dB／m，980nm吸收带半高宽达到200nm。在波长为980nm、泵浦功率为2w的条件下，可以得到28．8dBm（760mW）的输出，相比掺Er^3＋光纤（EDF），EYDCF的增益高，所需光纤长度短，所以非线性效应的发生得到抑制。     

A silicon homojunction infrared detector having an active metalfilm on an n++ layer

A silicon n⁺⁺pn homojunction infrared detector, in which a degenerate n⁺⁺ layer is backed by a metal film forming an ohmic contact, has been proposed and studied. The metal film is a photoelectric conversion region along with the n⁺⁺ layer. Although, for an n⁺⁺pn detector without the metal film, very poor rectifying properties are observed when the n⁺⁺ layer thickness is extremely reduced, the new detector, employing a thin PtSi film as the metal film, shows normal diode I-V characteristics, since the PtSi film provides increased surface conductivity. The new detector has achieved an increase in operatable temperature, or an extension of cutoff wavelength, and operated with cutoff wavelengths of 11.9 μm, 18.7 μm and about 30 μm at 70 K, 50 K, and 30 K, respectively, because the saturation current density for the new detector has been reduced to about one tenth that for the previously reported n⁺⁺pn detector. The responsivity for the new detector has increased to 1.1-3.8 times as large as that for the previously reported n⁺⁺pn detector, when both detectors have the same cutoff wavelength     

High-speed experiments on a QFP-based comparator for ADCs with18-GHz sample rate and 5-GHz input frequency

The authors report on the high-speed operation of a superconducting comparator circuit, based on coupling the quantum flux parametron (QFP) to an RF SQUID, which can be used to build a flash-type analog-to-digital converter (ADC). Simulations of this circuit show that it is expected to achieve operation with input signal bandwidths greater than 4 GHz and with a dynamic range equal to at least 4 b of resolution. A QFP-based comparator fabricated with a process using NbN/Pb-alloy Josephson junctions of 5 μm by 5 μm and a current density of 100 A/cm² has been examined to evaluate the properties of the QFP-ADC. Analog-to-digital conversion of the comparator has been observed with a QFP activation frequency up to 18.2 GHz. By employing a sampling method, input signals with frequencies up to 5.4 GHz have also been digitized     

Room-temperature CW laser operation at ~1.55 μm (eye-safe range)of Yb:Er and Yb:Er:Ce:Ca2Al2SiO7crystals

Room-temperature CW laser operation at 1.55 μm of Yb:Er:Ca₂Al₂SiO₇ (CAS) single crystal pumped at 940 nm and 975 nm has been achieved for the first time. Introduction of a third doping ion, Ce³⁺, decreases the Er ³⁺⁴I_11/2 excited-state lifetime and improves the laser properties. For Yb:Er:Ce:CAS single crystal, a maximum of 20 mW output power is produced for 285 mW absorbed power. With this material, a low threshold of 20 mW and a relatively high slope efficiency of ~5.5% are obtained. Preliminary results indicate possible improvement in the near future. Experimental threshold values and laser properties of CAS crystals with various compositions are in good agreement with calculations, performed using the rate-equations modeling. Comparison with a Yb:Er:phosphate glass laser is also presented     

A sinh resistor and its application to tanh linearization

We present a novel and simple subthreshold tunable resistor (sinhR) which exhibits a sinh I-V characteristic. This compact 8-transistor circuit generates an output current that is proportional to the sinh of its input differential voltage and has an offset-free characteristic, i.e., zero current at zero differential voltage, like a real resistor. In a 1.5-/spl mu/m CMOS chip implementation, we achieved a common-mode rejection ratio (CMRR) of 46 dB. As an example application, we use the expansive properties of our sinhR to linearize the compressive properties of a tanh differential pair by degeneration and cancel all nonlinearities up to fifth order. We demonstrate good agreement between theory and experimental results.     

Specific features of electroluminescence in heterostructures with InSb quantum dots in an InAs matrix

The electrical and electroluminescence properties of a single narrow-gap heterostructure based on a p-n junction in indium arsenide, containing a single layer of InSb quantum dots in the InAs matrix, are studied. The presence of quantum dots has a significant effect on the shape of the reverse branch of the current-voltage characteristic of the heterostructure. Under reverse bias, the room-temperature electroluminescence spectra of the heterostructure with quantum dots, in addition to a negative-luminescence band with a maximum at the wavelength λ = 3.5 μm, contained a positive-luminescence emission band at 3.8 μm, caused by radiative transitions involving localized states of quantum dots at the type-II InSb/InAs heterointerface.     

GaAs MOSFET using InAlP native oxide as gate dielectric

GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) using wet thermally oxidized InAlP as the gate insulator are reported for the first time. Leakage current measurements show that the 11-nm-thick native oxide grown from an In/sub 0.49/Al/sub 0.51/P layer lattice-matched to GaAs has good insulating properties, with a measured leakage current density of 1.39/spl times/10/sup -7/ mA//spl mu/m/sup 2/ at 1 V bias. GaAs MOSFETs with InAlP native gate oxide have been fabricated with gate lengths from 7 to 2 /spl mu/m. Devices with 2-/spl mu/m-long gates exhibit a peak extrinsic transconductance of 24.2 mS/mm, an intrinsic transconductance of 63.8 mS/mm, a threshold voltage of 0.15 V, and an off-state gate-drain breakdown voltage of 21.2 V. Numerical Poisson's equation solutions provide close agreement with the measured sheet resistance and threshold voltage.     

Fabrication and characterization of an AlGaN/PZT detector

Design,fabrication and characterization of a novel two-color detector for ultraviolet and infrared applications are reported.The detector has a simple multilayer structure composed of n-Al_(0.3)Ga_(0.7)N/i-GaN/p-GaN /SiO_2/LaNiO_3/PZT/Pt fabricated on a sapphire substrate.Ultraviolet and infrared properties are measured.For the ultraviolet region,a flat band spectral response is achieved in the 302-363 nm band.The detector displays an unbiased responsivity of 0.064 AAV at 355 nm.The current-voltage curve...     

Monolithic digital galvanic isolation buffer fabricated in silicon on sapphire CMOS

A monolithic four-channel digital galvanic isolation buffer in the 0.5 /spl mu/m silicon on sapphire (SOS) CMOS technology is reported. Advantage is taken of the insulating properties of the sapphire substrate to integrate on the same die both the isolation structure and the interface electronics. Each isolation channel has been tested to operate at data rates over 100 Mbit/s. The system can tolerate ground bounces of 1 V//spl mu/s and is tested for 800 V isolation. The system includes an integrated isolation charge pump to power the input circuit and is hence capable of operating from a single 3.3 V power supply.     

中波红外光学补偿三视场光学系统

针对320×240元致冷型凝视焦平面阵列探测器,设计了一种中波红外光学补偿三视场光学系统。该系统由变 焦物镜系统和二次成像系统构成,包括8块透镜(引入3个高次非球面,其余均为球面),并采用两个反射镜折叠光路。利用光学补偿变焦 原理和光学设计软件给出了系统的光学外形结构图,并对其像质和工艺性进行了分析。该系统可以通过对一组透镜的轴向定点移动实现 20°×15°、3.5°×2.6°和1.3°×1°三个视场的切换,系统变倍比为 1∶15。各视场在16 lp/mm空间频率处的光学传递函数(MTF)值均大于0.5,弥散斑直径的均方根(RMS) 值均小于20 m。工作波段为3.7 ～ 4.8 m,满足100 %冷光阑效率。该系统结构紧凑,工艺性好,成像质量高。