Measurement of attenuation and change of refractive index due to water vapour in the atmosphere at 890 GHz

An open-resonator technique is used to measure the attenuation and change of refractive index at 890 GHz for a variable water-vapour content in the atmosphere, using an HCN laser as a source. The refractive index increases uniformly with water-vapour content, a change of relative humidity from 0 to 50% at 26°C resulting in an index change of 1.3 × 10?4. An attenuation of 85±20 dB/km was measured for 50% relative humidity at 26°C.     

High-temperature operation of 1.55 ?m InGaAsP double-channel buried-heterostructure lasers grown by LPE

High-temperature operation of InGaAsP double-channel buried-heterostructure (DCBH) lasers emitting at 1.55 ?m is reported. The 1.55 ?m InGaAsP DCBH lasers have threshold currents as low as 18 mA at 20°C. The threshold current temperature sensitivity between 10°C and 75°C is characterised by a T0 value of 55?66 K. Electro-optical derivative measurements show that the 1.55 ?m InGaAsP DCBH laser does not have substantial above-threshold leakage current for junction temperatures as high as 75°C. Finally, these devices were operated at temperatures as high as 110°C, the highest CW operating temperature obtained to date for a 1.55 ?m InGaAsP laser.     

Fluoride glasses for infra-red optical fibres

Fluoride glasses in the ZrF4-BaF2-RF3 system (R=Gd, Yb) have been investigated as potential low loss materials for achievement of fibres transmitting wavelengths at about 3?5 ?m. Optical measurements confirm the interest in such components and PbF2 doping allows substantial refractive index increases, making for feasible doped core glass preforms.     

Small-active-area germanium avalanche photodiode for single-mode fibre at 1.3 ?m wavelength

A germanium avalanche photodiode of 30 ?m active area diameter has been fabricated and tested. The multiplied dark current is as low as 5 nA at room temperature. A module using this diode and a spherical lens has been assembled and coupled with a single-mode fibre of core diameter 10 ?m. The quantum efficiency of the module is 90% at 1.3 ?m. The sensitivity is measured at 45 Mbit/s and at 1.3 ?m. Minimum detectable powers obtained for 10?11 error rate are ?51.9 dBm and ?50.7 dBm at 25°C and 50°C, respectively.     

1.3 ?m InGaAsP DCPBH multiquantum-well lasers

We report the fabrication and performance characteristics of InGaAsP double-channel planar buried heterostructure (DCPBH) lasers with multiquantum-well active layers emitting at 1.3 ?m. These lasers have threshold currents in the range 40?50 mA at 30°C, external differential quantum efficiencies of ?50% at 30°C and T0 values ?160 to 180 K in the temperature range 10?60°C.     

Research on Michelson interference refractive index sensing technique based on double-core microfiber

We propose a novel refractive index sensor based on Michelson interferometer by using double-core microfiber. Through the reflection of the end and taper of double-core fiber (DCF), the Michelson interference spectrum is formed. Owing to the structure characteristic of double-core microfiber, this interferometer can achieve the measurement of refractive index (RI) and temperature. The experimental results show that the refractive index sensitivity of the interferometer is 2 377.80 nm/RIU at the diameter of the taper waist of 8.76 µm. In the temperature ranges from 30 °C to 60 °C, the temperature sensitivity is 0.070 48 nm/°C. This sensor has the advantage of high refractive index sensitivity.     

High-power aging tests of 1.3 and 1.5 ?m VIPS lasers

1.3 and 1.5 ?m VIPS lasers were tested under high-power aging levels up to 130 mW. The output powers of the lasers were enhanced by AR/HR-coating of facets and optimisation of cavity lengths. Aging power levels were 75% of ?Pmaxand were up to 130mW at 25°C and up to 90 mW at 70°C for 1.3?m VIPS lasers. The median lifetimes were estimated to be 150,000 h at 25°C and 60,000 h at 70°C. For the 1.5?m VIPS lasers, the aging power levels were up to 90 mW at 25°C and up to 50 mW at 70°C. Median lifetimes of about 60,000 h and 45,000 h for 25 and 70°C aging tests, respectively, were achieved.     

Temperature tuning of LiNbO3 electro-optic waveguide TE/TM mode convertors

A novel temperature tuning technique for LiNbO3 electro-optic waveguide mode convertors is described. Operation of both X- and Z-cut LiNbO3 devices with greater than 99% conversion efficiency at the fixed wavelength of 1.52 ?m is reported and tuning rates of ?0.9 nm°C?1 and ?1.0 nm°C?1, respectively, demonstrated.     

Return loss characteristics of optical fiber connectors

This paper describes the return loss characteristics for four typical contact type connectors: perpendicular and oblique endface connectors employing either physical contact or contact via index matching material. The high index layer on the polished fiber endface and the index matching material, which are important connector parameters, are investigated by measuring the return loss from one perpendicular fiber endface coated with the material and by etching the fiber endface. It is useful to apply two materials with different refractive indices to derive the refractive index and thickness of high index layers on perpendicular fiber endfaces. The index matching material we use has a refractive index of 1.467 at 20°C and a thermal coefficient of -2.9×10^-4/°C at 1.3 μm. We performed return loss calculations and experiments of the four contact type connectors. The worst value at any temperature from -40 to 80°C can be estimated, by measuring the return loss of these connectors at room temperature     

InGaAsP/InP separated multiclad layer stripe geometry lasers emitting at 1.5 ?m

InGaAsP/InP separated multiclad layer stripe geometry lasers emitting at 1.5 ?m are reported. The CW threshold current at 25°C is only 82 mA and the maximum temperature where CW lasing is obtained is 65°C. The characteristic temperature of the pulsed threshold current is 60 K. The transverse mode is fundamental and the longitudinal mode is single up to 1.5 times the threshold under CW operation. A few samples operated for over 1000 h at 50°C under constant optical power operation of 5 mW/facet.     

利用高对比度光栅实现光束大角度偏转

为了分析高折射率对比度光栅(HCG)参量和入射波长对光束偏转角的影响,采用严格耦合波法设计了透射光束可偏转非周期三角HCG,并通过时域有限差分法证明了所设计的非周期三角HCG可实现30.3°的透射光束偏转.结果表明,当低折射率介质材料折射率从1增加到1.4时,透射光束偏转角可实现11°的调谐;当入射波长从波长1.5μm...     

1.3 ?m InGaAsP index-guided multirib waveguide laser array

Phase-locked InGaAsP index-guided multirib waveguide laser arrays emitting at 1.3 ?m have been fabricated. These devices have threshold currents in the range 400?500 mA at 30°C and have been operated to pulsed output powers as high as 400 mW. More than 100 mW of output power has been obtained up to an ambient temperature of 60°C. The lasers emit in multilongitudinal modes with a far-field divergence of 20° × 40°.     

High-Temperature Sensing Using Miniaturized Fiber In-Line Mach–Zehnder Interferometer

A miniaturized single fiber in-line Mach-Zehnder interferometer is proposed for high-temperature sensing. The interferometer has a microcavity in one of its arms, formed by removing part of the fiber core and cladding, while the other arm remains in the fiber core. Because the fiber core exhibits a temperature coefficient of refractive index which is different from that of air, the interferometer is sensitive to temperature variation. The microcavity structured interferometer also has excellent sustainability to high temperatures up to 1100°C . The system is compact, reliable and can detect the temperature at precise location.     

Distributed temperature sensor using Nd3+ -doped optical fibre

We report the measurement of temperature distribution with an Nd3+ -doped multimode optical fibre. By exploiting the temperature-sensitive absorption bands of the doped-glass core, temperature was measured to an accuracy of 2°C over the range ?50°C to 100°C. A spatial resolution of 15 m over a fibre length of 140 m was obtained.     

Performance characteristics of high-brightness, CW, diode laser arrays

Recently developed, high-brightness diode laser arrays have been tested at 50°C at output powers of 0.5 W CW and 1.0W CW from 100?m- and 200?m-wide active regions, respectively. The extrapolated lifetimes at room temperature exceed 40000 h. The maximum CW power output prior to catastrophic degradation of the facets is 2.0 W for the 100?m device and greater than 3 W for the 200?m-aperture device.     

Fibre loss increase due to hydrogen generated at high temperatures

The loss changes at 1.39 and 1.88 ?m are measured for various nylon-jacketed fibres at a high temperature of 200°C. The loss increase at 1.39 ?m is due to the Si-OH-bond formation, and that at 1.88 ?m is caused by the absorption of hydrogen molecules in the silica glass. It is found that the loss increase due to the OH-bond formation is in proportion to the time-integrated concentration of the generated hydrogen molecules.     

Dispersive and scattering properties of a ZrF4 based glass

In a previous letter we presented the material dispersion in a ZrF4 based fluoride glass. The zero crossover wavelength ?c was found to occur between 1.6 and 1.7 ?m. Here, we analyse the refractive index measurements against wavelength data in order to obtain some physical parameters of this material on which ?c is dependent: electronic energy gap E0, electronic oscillator strength ED, lattice oscillator strength E1 and structure factor B. Such values, which are not yet known for fluoride glasses, will be then compared with those corresponding to SiO2 glass. Evaluation of the Rayleigh scattering coefficient will also be made.     

CMOS logic cell switching speed thermal characterisation

A study of the switching speed performance of basic CMOS logic cells in the (junction) temperature range 25?250°C is reported. Experimental measurements for capacitively loaded inverters and NAND gates of two standard 4 ?m CMOS processes are compared to theory and to SPICE2G. 6 simulations. It is found that, to a good approximation, a simple delineation factor (lying between 0.004 and 0.006/deg C in this study), applied to the average gate delay at a given temperature, correctly predicts this parameter. Logic cells are thereby typically found to be up to 65% slower at 250°C than they are at room temperature.     

Room-temperature 1.55?m optical bistability in a GaInAs/AlInAs multiple-quantum-well etalon

1.55 ?m optical bistability has been observed in a Gain As/AlInAs MQW etalon at room temperature, and we have shown that the nonlinear mechanism responsible for the bistability is due to an electronic nonlinearity in the refractive index.     

1.55 ?m InGaAsP low-threshold buried-crescent injection laser

Fabrication of 1.55 ?m InGaAsP buried-crescent (BC) injection lasers with a p-n-p-n blocking structure is described. The BC lasers exhibit a threshold current as low as 14 mA at 25°C, very high yield, output power more than 10 mW and high-temperature operation up to 80°C. These BC lasers have continued to operate in stable CW mode at 50°C for more than 1000 h. The lifetime of the 1.55 ?m InGaAsP lasers at 50°C is estimated to exceed about 2.5 × 104 h.