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排序方式: 共有72条查询结果,搜索用时 15 毫秒
1.
Hansen P.B. Raybon G. Koren U. Miller B.J. Young M.G. Newkirk M.A. Chien M.-D. Tell B. Burrus C.A. 《Electronics letters》1993,29(9):739-741
A 2 cm long three-contact multisection laser has been fabricated for modelocking at very low repetition rates. Active modelocking yields 8.0-12.3 ps pulses at 2.2, 4.3 and 6.5 GHz corresponding to the fundamental, first, and second harmonics of the cavity resonance frequency. This device demonstrates the feasibility of fabricating monolithic pulse sources operating at rates as low as the OC-48 Sonet transmission rate (2.488 Gbit/s).<> 相似文献
2.
Woodward S.L. Koren U. Miller B.I. Young M.G. Newkirk M.A. Burrus C.A. 《Photonics Technology Letters, IEEE》1992,4(12):1330-1332
A distributed Bragg reflector (DBR) laser tuned by resistive heating is presented. It has a tuning range greater than 10 nm with only a 33% reduction in output power and a 10% increase in linewidth. Its behavior is easily modeled, agreeing well with simple theory 相似文献
3.
Tarak Amine Joseph W. Newkirk Frank Liou 《The International Journal of Advanced Manufacturing Technology》2014,73(9-12):1739-1749
A potential problem in applying the direct laser deposition (DLD) technique to material fabrication is the effect that subsequent deposited layers have on reheating previous laser deposition layers. Most of the previous investigations examined the effect of the laser deposition parameters on the microstructure and mechanical properties of a single layer. This work focused on the effect of the laser parameters of subsequent layers on the microstructure and mechanical properties of the deposited layers to select proper parameters and characterize the effect. The microstructure morphology and property values are affected by the varied parameters. This leads to some tempering and aging effects in the steels. The microstructure of the top layer was equiaxed, while the near substrate region was fine dendritic. Typically, both of the travel speed and power of the laser show the significant effects on microstructure and hardness. 相似文献
4.
Hansen P.B. Raybon G. Koren U. Miller B.I. Young M.G. Newkirk M.A. Chien M.-D. Tell B. Burrus C.A. 《Electronics letters》1993,29(7):639-640
An electroabsorption modulator has been monolithically integrated with an extended-cavity laser, which incorporates a Bragg reflector. Actively modelocked at the fundamental cavity resonance frequency of 4.5 GHz, the laser provides a train of 6.3 ps pulses with a centre wavelength of 1544 nm onto which data is encoded by the modulator. This 4.5 Gbit/s single-chip transmitter is suitable for systems employing short optical pulses.<> 相似文献
5.
Yoshihira Okanda Masao Fukusumi Soji Nenno John B. Newkirk 《Metallurgical and Materials Transactions A》1983,14(10):2131-2142
High temperature corrosion tests in 80 pct Na2SO4-20 pct NaCI were made on five Fe-30 wt pct Cr-5 wt pct Al alloys containing various amounts of cerium up to 0.68 pct. After the corrosion tests, samples were examined metallographically and by X-ray diffraction and X-ray microanalysis. It was found that the surface scale formed on each sample decreased in thickness as the Ce content increased. Electron probe microanalyses suggest that this retarding behavior is related to the early formation of a Ce-induced protective scale of α-Al2O3. The role of Ce in promoting the formation of the α-Al2O3 scale is discussed. 相似文献
6.
Tarak Amine Joseph W. Newkirk Hussam El-Din F. El-Sheikh Frank Liou 《The International Journal of Advanced Manufacturing Technology》2014,73(9-12):1427-1435
Several techniques can be used to improve surface properties of metals. These can involve changes on the surface chemical composition such as alloying or on the surface microstructure, such as hardening. In the present work, melting of the surface by a 9 kW CO2 CW laser of wavelength 10.6 μm was used to alter surface features of D2 tool steel. Carbon powder and nitrogen gas were used as sources of alloying elements during laser processing. The effect of various laser parameters (power and speed) on the microstructure and hardness of D2 tool steel was investigated. Laser powers from 1 to 8 kW and laser speeds from 5 to 15 mm/s were employed. It was found that as the laser power increases, the hardness of the melted zone decreases while that of the heat-affected zone increases. On the other hand, the depth of both of melted and heat-affected zones increases with power. 相似文献
7.
Kim I. Alferness R.C. Buhl L.L. Koren U. Miller B.I. Young M.G. Newkirk M.A. Chien M.D. Koch T.L. Raybon G. Burrus C.A. 《Photonics Technology Letters, IEEE》1993,5(11):1319-1321
A photonic integrated circuit with an InGaAs/InGaAsP multiple-quantum-well (MQW) traveling-wave optical amplifier and a grating-assisted vertical-coupler filter as a noise filter have been demonstrated. A fiber-to-amplifier/filter gain of ~0.5 dB and a 3-dB filter bandwidth (FWHM) of ~70 Å at 1.56 μm filter center wavelength have been achieved. This photonic circuit is potentially suitable as a building-block for preamplifier lightwave receivers or high-gain, high-power optical amplifiers which are essential for optical communication systems and lightwave networks 相似文献
8.
In the derivation of phase diagrams using solid- and liquid-solution thermodynamic equilibria, thermodynamic models are used
to extrapolate experimental data to a broader range of compositions and temperatures. Such models have historically increased
in complexity from the regular-solution formalism, with regard to both temperature and composition dependence of parameters.
The regular, quasi-regular, subsubregular, and quasi-subsubregular models have been applied to existing thermodynamic data
for four“simple” metallic systems of differing types (Cu-Ni, Pb-Ag, Sn-Zn, and Ge-Mg) to illustrate the effect of more accurate
thermodynamic modeling on the resulting predicted phase diagrams. Comparison with the actual phase diagrams demonstrates the
relative importance of“nonregularity” in the solution with regard to both composition and temperature in the accuracy of phase
diagram prediction.
This paper was presented at the International Phase Diagram Prediction Symposium sponsored by the ASM/MSD Thermodynamics and
Phase Equilibria Committee at Materials Week, October 21-23,1991, in Cincinnati, OH. The symposium was organized by John Morral,
University of Connecticut, and Philip Nash, Illinois Institute of Technology. 相似文献
9.
10.
Newkirk M.A. Koren U. Miller B.I. Chien M.D. Young M.G. Koch T.L. Raybon G. Burrus C.A. Tell B. Brown-Goebeler K.F. 《Photonics Technology Letters, IEEE》1992,4(11):1258-1260
A 1.5-μm multiquantum well amplifier divided into three sections with short contacts at the input and output facets is described. A simple derivation shows that the amplifier optical gain is proportional to the ratio of voltage changes at the facet contacts induced by the optical signal. Measurements of optical gain and contact voltage as a function of amplifier bias current are in good agreement with the theory 相似文献