The demonstration of RF photonic links with bandwidths of 100 GHz or more is expected in the near future, due to rapid and continuing progress in modulator and detector technology. Since it is very difficult to electr...
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ISBN:
(纸本)081942918X
The demonstration of RF photonic links with bandwidths of 100 GHz or more is expected in the near future, due to rapid and continuing progress in modulator and detector technology. Since it is very difficult to electronically process such a large bandwidth after photodetection, photonic approaches that reduce the burden on the electronics are increasingly relevant. One such approach is an optical channelizer, where an RF modulated optical carrier is optically dispersed onto a detector array. Each element of the array only sees a portion of the original wideband RF spectrum. We analyze the RF performance of optical channelizers in terms of crosstalk and uniformity of response. Both direct detection and heterodyne channelizers will be considered. Analysis of this kind is necessary for our application, since the usual parameters of a dispersive optical system, such as resolution, resolving power or filter linewidth do not provide enough information to determine the RF performance. The analysis has shown that a Fabry-Perot filter based channelizer cannot provide adequate RF performance, while a grating-based channelizer can. For channelization to 1 GHz channels with a -70 dB crosstalk specification, a total grating length of roughly 80 cm is required, so a multiple bounce geometry is necessary to obtain a reasonably compact system.
We have developed a 64-channel time-resolved spectroscopy (TRS) system based on a time-correlated single photon counting (TCPC) method to achieve near infrared spectroscopy and/or optical computed tomography (CT) for ...
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ISBN:
(纸本)0819423904
We have developed a 64-channel time-resolved spectroscopy (TRS) system based on a time-correlated single photon counting (TCPC) method to achieve near infrared spectroscopy and/or optical computed tomography (CT) for clinical applications. This system employs advanced devices such as a high power picosecond light pulser (PLP), a high sensitive/fast photomultiplier tube (PMT) and a high speed signal processing circuit. The PLP offers an average optical power of around 0.25 mW, and the PMT has a quantum efficiency greater than 2 % at 800 nn. The signal processing circuit is composed of miniaturized CFD/TAC modules and signal acquisition unit with 1 MHz ADC, and provides 64 independent TCPC circuits for time-of-flight measurement. System performance was estimated by measuring transmitted and reflected light passing through tissue-like phantom models simulating the human breast and infant head. We concluded that this system has the sufficient performance for optical CT utilizing time-of-flight measurement.
Novel multiphasic nanostructured inorganic : polymer composites of C60 have been prepared by sol-gel processing. These composites offer the prospect of introducing multifunctionality by optimizing each phase for a par...
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ISBN:
(纸本)0819418897
Novel multiphasic nanostructured inorganic : polymer composites of C60 have been prepared by sol-gel processing. These composites offer the prospect of introducing multifunctionality by optimizing each phase for a particular response. Since the phase separation is at a nanometer size scale, the composites are optically transparent. Results are presented form the studies of spectroscopic characterization, optical power limiter behavior, and third-order nonlinear optical response.
We report on the results of experiments performed in areas of technology required to develop gigabit optical interconnects for communication at 1.3 micrometers wavelength. The goal of this work was to develop intercon...
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ISBN:
(纸本)0819415197
We report on the results of experiments performed in areas of technology required to develop gigabit optical interconnects for communication at 1.3 micrometers wavelength. The goal of this work was to develop interconnects not only with very high bandwidth, but with serve to multiple channels having multiple access and simple processing algorithms so as not to rely on high bandwidth electronics, as well. Optical correlation switches (i.e. optical `AND' gates) for use in time-division optical interconnects achieve these goals.
Volume diffraction gratings, resulting from the plasma effect, are encoded in a new class of materials. The effect, based on persistent photoconductivity (PPC) associated with DX centers. Exposure of samples to light ...
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Volume diffraction gratings, resulting from the plasma effect, are encoded in a new class of materials. The effect, based on persistent photoconductivity (PPC) associated with DX centers. Exposure of samples to light of sufficient photon energy generates free electrons via ionization of DX centers. Illumination with spatially varying light imprints a spatially varying free carrier density, which generates local refractive index changes via the plasma effect index changes. The extension of this effect to ii-VI semiconductors offers the possibility of stability at higher temperatures, availability of high quality bulk crystals, and a wider range of excitation and readout wavelengths. Samples used in initial experiments were In-doped CdZnTe, grown using the Bridgeman technique.
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