High temperature operation of lattice matched and strained InGaAs-InP quantum well lasers

The temperature dependence of lattice matched and strained InGaAs-InP quantum well lasers operating between 1.48 and 1.56 mu m is described. Devices grown under tensile and compressive strain, with an In concentration in the range of 0.43>     

The diffraction of elastic waves by an imperfect fusion bond

We consider diffraction by a semi-infinite crack located alonga fusion interface between two differing elastic media. Twotypes of crack, namely open and partially closed cracks, areinvestigated. An open crack is modelled by a stress-free contactboundary condition and a partially closed crack is modelledby a spring contact boundary condition. For the latter, thejump in the stress across the crack is assumed to be proportionalto the jump in the displacement across the crack. This situationarises in, for example, a K-weld where the fine grain of theparent material (for example, ferritic or forged austeniticsteel) is in stark contrast with the coarse-grained weld metal(for example, austenitic weld metal). In the metal weld thedirection of the grain axis varies through the metal. However,diffraction is a local phenomenon and so the austenitic steelis assumed to have a zonal axis so that it may be modelled bya transversely isotropic composite. The ferritic or forged austeniticsteel will be modelled as an isotropic material.     

Optical demultiplexing at 6 Gb/s using a semiconductor laser amplifier as an optical gate

A semiconductor laser amplifier (SLA) has been employed successfully for optical demultiplexing in two-channel optical time division multiplexed system experiments at 6 and 2 Gb/s. Demultiplexing of 6-Gb/s (2-Gb/s) signals was demonstrated with a power penalty of 1.6 dB (3.0 dB) at bit error rates of 10/sup -9/. It is also shown that a reduction of the generated amplified spontaneous emission can be obtained by optical gating/demultiplexing for systems incorporating inline amplifiers. A 0.5-dB improvement in sensitivity was achieved as a result of using an SLA for demultiplexing from 2.0 to 1.0 Gb/s in a system with one inline Er/sup 3+/-doped fiber amplifier.<>     

Tunable electroabsorption modulated laser integrated with a bent waveguide distributed-feedback laser

The fabrication of the first 1.55-/spl mu/m wavelength tunable electroabsorption modulated laser integrated with a bent waveguide distributed-feedback laser is reported. A low-threshold and stable single-mode operation is obtained when the devices were uniformly pumped. A single-mode output power close to 10 mW from a single-mode fiber (40 mW in free space) is obtained with a 0 V bias to the modulator and an extinction ratio of up to 15 dB at 2.5 V. This single mode stability is due to the continuously distributed phase shift implemented in the structure. With a nonuniform injection, it was possible to select one particular mode out of the three neighboring modes inside the broad-reflection band of the reflector. A tuning range of 3.5 mm was obtained while maintaining an output power of more than 2 dBm from each mode.     

Fabrication of InGaAsP/InP buried heterostructure laser usingreactive ion etching and metalorganic chemical vapor deposition

1.3-μm InGaAsP/InP buried heterostructure lasers were fabricated using Ch₄/H₂ reactive ion etching (RIE) for mesa definition and metalorganic chemical vapor deposition for blocking laser growth. Results show that high-quality lasers can be made using RIE, with threshold current as low as 10 mA. It was also found that a slight chemical etching of the RIE mesas was necessary to obtain lasers with as high quality as those fabricated entirely by wet etching     

1.5 ?m phase-shifted DFB lasers for single-mode operation

Fabrication and single-mode laser oscillation were demonstrated for modified DFB lasers where the phase of the corrugations was shifted at the centre by a quarter guided-wavelength and which, in principle, provided a resonance at the Bragg wavelength and stable single-mode oscillation. Phase-shifted corrugations were fabricated using electron-beam lithography.     

Measurement of a VPE-transported DFB laser with blue-shiftedfrequency modulation response from DC to 2 GHz

The frequency modulation characteristics of a VPE-transported 1.53 μm wavelength GaInAsP-InP DFB semiconductor diode laser was measured. Below approximately 0.7 mW optical output power per facet, it exhibited a smooth, blue-shifted, frequency modulation response from DC to 2 GHz. In the modulation frequency range of 10 MHz to 100 MHz it exhibited a |Δf/ΔI| of 0.5-1.8 GHz/mA, depending on the biasing level     

Growth and dielectric properties of Ta_2O_5 single crystals grown by laser heated pedestal growth technique

Ta2O5 single crystals have been grown by the laser heated pedestal growth (LHPG) technique up to several centimeters length with diameter of 1.1 mm. The crystal, characterized by X-ray diffraction, dielectric measurement, and thermal expansion analysis, has Htri-Ta2O5 symmetry. Dielectric permittivity, loss tangent along [001] and [110] direction were investigated over the temperature range from -80 ℃ to 100 ℃. Large dielectric anisotropy in Ta2O5 single crystal was observed. At room temperature, the dielectric permittivities (1 MHz) along [001] and [110] are 33.2 and 231.9, respectively. The reason of dielectric enhancement in Ta2O5 crystal grown by LHPG was also discussed.     

基于流形正则化非负矩阵分解的高光谱数据降维

采用基于流形正则化非负矩阵分解(MR-NMF)的高 光谱数据降维方法。新方 法通过构建样本的近邻图描述数据几何结构,然后将其作为正则项加入NMF的目标函 数中进行组合优化。在真实的高光谱数据集HYDICE上进行的实验结果表明,新方法能 够提高高光谱图像分类的精度。     

Simple-structure integrated coherent transceiver with novelcounter-receiving heterodyne detection scheme

A novel counter-receiving heterodyne detection (CRHD) scheme for a four-section integrated coherent transceiver for access networks is proposed. Error free detection at 100 Mbit/s is achieved with the CRHD scheme. This scheme leads to the relaxation of the design requirements of integrated coherent transceivers and facilitates duplex transmissions with coherent transceivers. A novel full-duplex transmission approach is also proposed and experimentally demonstrated