224 research outputs found
Design and Optimization of High-Speed Resonant Cavity Enhanced Schottky Photodiodes
Cataloged from PDF version of article.Resonant cavity enhanced (RCE) photodiodes (PD’s)
are promising candidates for applications in optical communications
and interconnects where high-speed high-efficiency photodetection
is desirable. In RCE structures, the electrical properties
of the photodetector remain mostly unchanged; however, the
presence of the microcavity causes wavelength selectivity accompanied
by a drastic increase of the optical field at the resonant
wavelengths. The enhanced optical field allows to maintain a high
efficiency for faster transit-time limited PD’s with thinner absorption
regions. The combination of an RCE detection scheme with
Schottky PD’s allows for the fabrication of high-performance
photodetectors with relatively simple material structures and
fabrication processes. In top-illuminated RCE Schottky PD’s,
a semitransparent Schottky contact can also serve as the top
reflector of the resonant cavity. We present theoretical and
experimental results on spectral and high-speed properties of
GaAs–AlAs–InGaAs RCE Schottky PD’s designed for 900-nm
wavelength
The laser-hybrid accelerator for radiobiological applications
The `Laser-hybrid Accelerator for Radiobiological Applications', LhARA, is conceived as a novel, uniquely-flexible facility dedicated to the study of radiobiology. The technologies demonstrated in LhARA, which have wide application, will be developed to allow particle-beam therapy to be delivered in a completely new regime, combining a variety of ion species in a single treatment fraction and exploiting ultra-high dose rates. LhARA will be a hybrid accelerator system in which laser interactions drive the creation of a large flux of protons or light ions that are captured using a plasma (Gabor) lens and formed into a beam. The laser-driven source allows protons and ions to be captured at energies significantly above those that pertain in conventional facilities, thus evading the current space-charge limit on the instantaneous dose rate that can be delivered. The laser-hybrid approach, therefore, will allow the vast ``terra incognita'' of the radiobiology that determines the response of tissue to ionising radiation to be studied with protons and light ions using a wide variety of time structures, spectral distributions, and spatial configurations at instantaneous dose rates up to and significantly beyond the ultra-high dose-rate `FLASH' regime. It is proposed that LhARA be developed in two stages. In the first stage, a programme of in vitro radiobiology will be served with proton beams with energies between 10MeV and 15MeV. In stage two, the beam will be accelerated using a fixed-field accelerator (FFA). This will allow experiments to be carried out in vitro and in vivo with proton beam energies of up to 127MeV. In addition, ion beams with energies up to 33.4MeV per nucleon will be available for in vitro and in vivo experiments. This paper presents the conceptual design for LhARA and the R&D programme by which the LhARA consortium seeks to establish the facility
Heterostructures for Optical Devices
Contains research objectives and reports on eight research projects.Joint Services Electronics Program (Contract DAAL03-86-K-0002)Joint Services Electronics Program (Contract DAALO3-89-C-0001)National Science Foundation (Grant EET 87-03404)Charles Stark Draper Laboratory (Contract DL-H-315251)Xerox Corporation FellowshipMIT Fund
Heterostructures for High Performance Devices
Contains an introduction and reports on ten research projects.Charles S. Draper Laboratory, Contract DL-H-315251Joint Services Electronics Program, Contract DAAL03-89-C-0001National Science Foundation Grant, Grant EET 87-03404MIT FundsInternational Business Machines CorporationNational Science Foundation Grant ECS 84-1317
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