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排序方式: 共有88条查询结果,搜索用时 15 毫秒
1.
The single fundamental mode output power of photonic crystal vertical cavity lasers is improved by varying sizes of oxide apertures and defect lasing apertures. A maximum output power of 3.1 mW in the fundamental mode has been achieved with a new fabrication process that involves only focused ion beam etching to create holes in selectively oxidised VCSELs. 相似文献
2.
Planar optical waveguides are an attractive tool for use in analytical chemistry and spectroscopy. Although similar to fiber optics, planar waveguides have been slow to be commercially accepted due to the difficulty of coupling light into the guide. Generally, prism coupling is the method of choice in the laboratory, as efficiencies approaching 80% can be reached. However, prisms are impractical for routine use for several reasons: expensive positioning equipment is required, coupled power is sensitive to environmental fluctuations, and prism coupling prohibits the fabrication of a truly planar device. The use of thin gratings on the surface of the waveguide allows for a two-dimensional structure to be maintained, while providing enough efficiency to be useful as a sensor. Our research efforts focus on developing a technique to make inexpensive, reproducible gratings that are easy to fabricate. By chemically modifying the surface of a commercial grating with a suitable release agent, it is possible to emboss replica gratings onto a variety of waveguide types. The fabrication of embossed gratings will be described, and their performance on glass, ion-diffused, polymer, and semiconductor waveguides will be presented. 相似文献
3.
Advances in selective wet oxidation of AlGaAs alloys 总被引:3,自引:0,他引:3
Choquette K.D. Geib K.M. Ashby C.I.H. Twesten R.D. Blum O. Hou H.Q. Follstaedt D.M. Hammons B.E. Mathes D. Hull R. 《IEEE journal of selected topics in quantum electronics》1997,3(3):916-926
We review the chemistry, microstructure, and processing of buried oxides converted from AlGaAs layers using wet oxidation. Hydrogen is shown to have a central role in the oxidation reaction as the oxidizing agent and to reduce the intermediate predict As2O3 to As. The stable oxide is amorphous (AlxGa1-x) 2O3 which has no defects along the oxide/semiconductor interfaces but can exhibit strain at the oxide terminus due to volume shrinkage. The influence of gas flow, gas composition, temperature, Al-content, and layer thickness on the oxidation rate are characterized to establish a reproducible process. Linear oxidation rates with Arrhenius activation energies which strongly depend upon AlAs mole fraction are found. The latter produces strong oxidation selectivity between AlGaAs layers with slightly differing Al-content. Oxidation selectivity to thickness is also shown for layer thickness <60 nm. Differences between the properties of buried oxides converted from AlGaAs and AlAs layers and the impact on selectively oxidized vertical cavity laser lifetime are reported 相似文献
4.
Loss between elements of coherently coupled vertical-cavity surface-emitting laser (VCSEL) arrays typically causes out-of-phase operation with on-axis intensity nulls in the far-field. We show that in-phase evanescently coupled VCSEL arrays may be defined by proton implantation. An advantage for implanted in-phase coherently coupled VCSEL arrays is that this approach employs a simple and reliable fabrication process where the absence of loss between elements leads to in-phase coupling. We present data for 2, 3, and 4 element in-phase implant-defined coherently coupled VCSEL arrays. 相似文献
5.
The changes in the morphology and the composition of Raney Ni composite-coated electrodes was investigated during leaching in concentrated NaOH aqueous solutions. The rate of hydrogen generated during leaching is increased by stirring the solution, raising the temperature and increasing the NaOH concentration to 6.09 M. The depletion of Al from the Raney Ni particles results in phase transformations and the metal/solution interfacial area increases with time. It is suggested that the electrodeposited nickel has a dominant influence on the hydrogen discharge since the electrocatalytic activity is practically independent of the leaching time. 相似文献
6.
Numerical investigation of self-heating effects of oxide-confined vertical-cavity surface-emitting lasers 总被引:1,自引:0,他引:1
We present a comprehensive numerical model to simulate self-heating effects of oxide-confined vertical-cavity surface-emitting lasers (VCSELs) under continuous-wave operation. The model self-consistently accounts for the close interaction between optical, electrical, and thermal processes in VCSELs. In particular, hot carriers and nonequilibrium optical phonons in the quantum wells are modeled by solving a carrier energy balance equation and an optical phonon rate equation. Our numerical simulations reveal that they are responsible for aggravated thermal rollovers in VCSELs' L-I characteristics. Detailed comparisons are made and good agreement is obtained between simulations and experiments for the L-I-V and lasing wavelength characteristics of VCSELs with varying oxide aperture size. Various mechanisms that result in the L-I thermal rollover behavior are also investigated with the aid of simulations. 相似文献
7.
Many embedded systems and consumer appliances require high performance at extremely low price points, and they need them yesterday! Meeting these needs is the latest challenge for system and processor architects. SandCraft recognized this challenge early on and developed the Montage architecture to meet these needs and generate revenue that fuels business growth. Montage implements MIPS-compatible processors for license to MIPS licensees. We have implemented two Montage incarnations now on the market: the SR1 and the SR1-GX high-performance microprocessor cores. Other designs are in the pipeline. With the intellectual property in place, the architecture will proliferate and show that low cost and flexibility do not have to come at the cost of compromising performance. Here, we describe the philosophy behind the development of the Montage architecture and illustrate some of the thinking that resulted in this processor line 相似文献
8.
K.D. Choquette G. Hasnain Y.H. Wang J.D. Wynn R.S. Freund A.Y. Cho R.E. Leibenguth 《Photonics Technology Letters, IEEE》1991,3(10):859-862
GaAs quantum well vertical-cavity surface emitting lasers fabricated using low damage reactive ion etching are discussed. Lasers which are partially and completely etched through their structure are compared. The surface recombination velocity of exposed GaAs is not exacerbated in deep etched lasers; other loss mechanisms in shallow etched lasers have comparable impact on laser performance. Etched lasers exhibit low voltage and small differential series resistance at threshold, while devices fabricated by a combination of etching and ion implantation possess lower threshold current. It is found that reactive ion etching has little additional effect on laser operation, whereas the different device structures considered do influence laser performance.<> 相似文献
9.
Crawford M.H. Schneider R.P. Jr. Choquette K.D. Lear K.L. 《Photonics Technology Letters, IEEE》1995,7(7):724-726
We report on temperature dependent characteristics and single mode performance of one-wave cavity, planar implanted, AlGaInP-based vertical-cavity surface emitting lasers. By optimizing the overlap between the gain peak and the cavity mode of the structure, we demonstrate record device performance, including 8.2 mW maximum output power and 11% power conversion efficiency for multimode operation and 1.9 mW and 9.6% power conversion efficiency for single mode operation at 687 nm. Improved performance at elevated temperatures is also achieved, with 1.5 mW output power demonstrated at 50°C from a 15-μm-diameter device 相似文献
10.