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1.
A compact, high-resolution analog-to-digital converter (ADC) especially for sensors is presented. The basic structure is a completely digital circuit including a ring-delay-line with delay units (DUs), along with a frequency counter, latch, and encoder. The operating principles are: (1) the delay time of the DU is modulated by the analog-to-digital (A/D) conversion voltage and (2) the delay pulse passes through a number of DUs within a sampling (= integration) time and the number of DUs through which the delay pulse passes is output as conversion data. Compact size and high resolution were realized with an ADC having a circuit area of 0.45 mm/sup 2/ (0.8-/spl mu/m CMOS) and a resolution of 12 /spl mu/V (10 kS/s). Its nonlinearity is /spl plusmn/0.1% FS per 200-mV span (1.8-2.0 V), for 14-b resolution. Sample holds are unnecessary and a low-pass filter function removes high-frequency noise simultaneously with A/D conversion. Thus, the combination of this ADC and a digital filter that follows can eliminate an analog prefilter to prevent the aliasing before A/D conversion. Also, both this ADC can be shrunk and operated at low voltages, so it is an ideal means to lower the cost and power consumption. Drift errors can be easily compensated for by digital processing. 相似文献
2.
We propose combined distributed-feedback/Fabry-Perot (DFB/FP) structures for surface-emitting semiconductor lasers. The analysis is based on coupled-wave equations modified for surface-emitting lasers. The proposed structures, which exhibit enhanced resonance due to a matching between the gain and field distributions resulting in a reduced threshold compared with simple FP structures, are formed by placing the DFB structure between two DBR mirrors of an FP resonant cavity and introducing phase layers between the DFB region and the mirrors. It was found that the periodic-gain structures are a special case of the combined DFB/FP structures in which the index coupling effect is assumed to be negligible due to a small fill factor or a small refractive-index difference. The effect of complex (gain and index) coupling on the design and the threshold characteristics of the structures is clearly illustrated. Some important design considerations that were neglected in the previous papers are addressed 相似文献
3.
The beam divergence in the vertical direction from a graded index separate confinement heterostructure (GRINSCH) multiquantum-well (MQW) laser has been studied. It is demonstrated both theoretically and experimentally that a circular beam MQW laser can be produced by choosing appropriate thicknesses for the GRINSCH layers, while maintaining other desired laser characteristics. The beam divergence is found to be more affected by the index change induced by injected carriers than by strain in the MQW active layer. Theoretical results are in good agreement with the measurements for 1.3-μm InGaAsP strained MQW lasers 相似文献
4.
63 nm continuous signal band of a 1.5 Tbit/s (75/spl times/20 Gbit/s) dense wavelength division multiplexed transmission over 200 km was demonstrated by applying Er/sup 3+/-doped tellurite fibre amplifiers. 相似文献
5.
A general spontaneous emission model is developed for surface-emitting (SE) distributed feedback (DFB) semiconductor lasers. The frequency distribution of spontaneous emission noise below lasing threshold and the spontaneous emission rate in lasing operation are formulated by using a transfer matrix method combined with the Green's function method. The effective linewidth enhancement factor is obtained from this model in terms of the elements of the transfer matrix. By way of example, the author applies the formulation to a standard SE DFB laser, and a SE λ/4-shifted DFB laser with a distributed Bragg reflector (DBR) mirror. In particular, the author analyzes the below-threshold spectrum, the threshold current density, the differential quantum efficiency, and the spectral linewidth of these lasers 相似文献
6.
Kageyama T. Miyamoto T. Makino S. Ikenaga Y. Nishiyama N. Matsutani A. Koyama F. Iga K. 《Electronics letters》2001,37(4):225-226
The authors present a near 1200 nm wavelength vertical-cavity surface-emitting laser (VCSEL) the active region of which is formed by GaInNAs/GaAs quantum wells grown by chemical beam epitaxy. Room temperature continuous-wave operation has been demonstrated with a high slope efficiency of 0.23 W/A, a high output power of over 1.0 mW, and a singlemode output power of 0.34 mW. The fabricated devices with different aperture sizes show low threshold currents of 1.2-2.1 mA and a record low threshold current density of 2.6 kA/cm2 in GaInNAs VCSELs 相似文献
7.
Atsushi Makino D. Ichikawa A. Matsumoto T. Kanda T. Watanabe 《Proceedings of the Combustion Institute》2013,34(2):2197-2204
Spontaneous ignition of compacted mixture has been examined not only experimentally but also theoretically, relevant to materials synthesis for Ni–Al system. Spontaneous ignition temperature, determined from the inflection-point of the temporal variation of surface temperature, is found to decrease at first, reach the minimum, and then increase gradually, with increasing size ratio, being defined as the ratio of compact and particle diameters and reported to be useful in correlating experimental results. The lowest temperature observed is as low as that, more than 200 K below the melting point 934 K of Al, at the size ratio of c.a. 700. While its decrease is attributed to the increase in the particle surface per unit spatial volume of compacted mixture, as reported in the literature, its increase found in the course of the present study can fairly be correlated to an enhancement of heat loss from each particle in the compacted mixture, by conducting a theoretical consideration. As for the dependence of spontaneous ignition temperature on the mixture ratio, a shifting occurs from a decreasing trend with increasing mixture ratio at small size ratios, less than about 700, to an insensitive trend to the mixture ratio, had not been reported in the literature. In addition, a fair degree of agreement, shown in experimental comparisons with theoretical results, indicates that the present formulation has captured the essential features of the spontaneous ignition of compacted mixture, especially for size ratios with large values. Since this kind of particle size effects, relevant to the spontaneous ignition of the compacted mixtures, has not been captured in the previous studies, its elucidation can be considered not only notable but also useful, in manipulating combustion process in materials synthesis, especially, in choosing a specific condition for the lowest spontaneous ignition temperature by varying the size ratio. 相似文献
8.
Sun-Chan Jeong Ichiro Katayama Hirokane Kawakami Yutaka Watanabe Hironobu Ishiyama Nobuaki Imai Yoshikazu Hirayama Hiroari Miyatake Masao Sataka Hiroyuki Sugai Satoru Okayasu Shin-Ichi Ichikawa Katsuhisa Nishio Shinichi Mitsuoka Takamitsu Nakanoya Takashi Hashimoto Takanori Hashimoto Masahito Yahagi 《Solid State Ionics》2009,180(6-8):626-630
The diffusion coefficients of Li in the NaTl-type Li intermetallic compound of β-LiGa have been measured by using a short-lived radioactive diffusion tracer. As the tracer, the α-emitting radioisotope of 8Li delivered as the energetic and pulsed beam from Tokai Radioactive Ion Accelerator Complex (TRIAC) was implanted into the β-LiGa compounds with the composition in the range of about 43 to 54 at.% Li. By analyzing the time-dependent yields of the α-particles measured according to the repetition cycle of the beam, the tracer diffusion coefficients were extracted over the wide range of Li composition. Abnormal composition-dependence of Li diffusion coefficients in β-LiGa was observed; the stoichiometric β-LiGa showed the highest diffusivity of Li. By referring to the composition-dependent diffusivity of Li in the iso-structural β-LiAl and β-LiIn, we could identify the abnormal diffusion of Li in very Li-poor composition of β-LiGa. The anomaly has been discussed qualitatively in terms of the formation of defect complex and the interaction between the constitutional defects. 相似文献
9.
Akchurin N Langland J Onel Y Bonner BE Corcoran MD Cranshaw J Nessi-Tedaldi F Nessi M Nguyen C Roberts JB Skeens J White JL Bravar A Giacomich R Penzo A Schiavon P Zanetti A Bystricky J Lehar F de Lesquen A van Rossum L Cossairt JD Read AL Derevschikov AA Matulenko YA Meschanin AP Nurushev SB Patalakha DI Rykov VL Solovyanov VL Vasiliev AN Grosnick DP Hill DA Laghai M Lopiano D Ohashi Y Shima T Spinka H Stanek RW Underwood DG Yokosawa A Funahashi H Goto Y Imai K Itow Y Makino S Masaike A 《Physical review D: Particles and fields》1993,48(7):3026-3036
10.
The pulse lasers, YAG-, CO2-, and N2-lasers, are examined for use in the cleaning of glass. Cleaning is found to be due to the evaporation and sputtering of stains on the glass by the heat energy of the laser light. Only the N2 laser can be used for the cleaning of the exit surface of the glass (the opposite side to the laser). A laser with a high peak power of about 106J/s and short-pulse duration below 100 ns is found to be necessary in practice. 相似文献