We present an optical tandem single sideband receiver that eliminates the need for guardbands between adjacent WDM channels, while also receiving signals that have different data on the two sidebands of the same optical carrier.

For maximal performance, solar cells should resemble semiconductor lasers; i.e. they should be constructed in the form of a double heterostructure. This configuration is also sometimes called ''minority carrier mirrors''. We have found rather good performance in SIPOS-crystalline silicon-SIPOS double heterostructures as well as in a p-n homojunction made entirely of SIPOS. This sheds some light on the truly outstanding performance of the n/sup +/-SIPOS: Si heterojunction which has a J /sub o/ = 10/sup -14/ Amps/cm/sup 2/. It has been recognized for some time that the structure of an ideal solar cell should resemble that of a semiconductor laser. The solar cell should be built in the form of a double heterostructure. In this configuration, a narrow bandgap active layer is sandwiched between two wide bandgap layers of opposite doping. The wide bandgap materials may be called ''minority carrier mirrors'' although this term is more frequently applied to high-low homojunctions at the rear of solar cells.

In this paper, we review the previous work in optical code division multiple access (CDMA) systems. Owing to the explosive growth of bandwidth demand in recent years, the current trend in optical communication system designs is to achieve one bit per hertz utilization of the available bandwidth in the optical fiber. Full orthogonality is important in order for optical CDMA systems to achieve high throughput. We describe two spectrally encoded optical CDMA systems which both give us full orthogonality. The throughput of the non-coherent spectral amplitude encoded system is limited by both speckle noise interference and shot noise interference. The multi-wavelength spectral phase encoded system is limited by shot noise only. Performance analysis is also given in this paper.

An entanglement-preserving photodetector converts photon polarisation to electron spin. Up and down spin must respond equally to oppositely polarised photons, creating a requirement for degenerate spin energies, ge ≃ 0, for electrons. The authors present a plot of ge factor against lattice constant, analogous to bandgap against lattice constant, that can be used for g factor engineering of III-V alloys and quantum wells.

Printed antennas exemplified by the microstrip patch antenna offer an attractive solution to compact, conformal and low cost design of modem wireless communications equipment, RF sensors and radar systems. Recent applications have pushed the frequency well into the ram-wave region even in the commercial arena as evidenced by the worldwide race to develop advanced collision warning radar systems for automobiles at the 76 GHz band.[1] Microstrip-based planar antennas fabricated on a substrate with a high dielectric constant (Si, GaAs and InP) are strongly preferred for easy integration with the MMIC RF front-end circuitry. However, it is well known that patch antennas on high dielectric constant substrates are highly inefficient radiators due to surface wave losses and have very narrow frequency bandwidth (approximately one to two percent). This situation becomes extremely severe as applications move to higher frequencies, resulting in patch antennas with reduced gain and efficiency as well as an unacceptably high level of cross polarization and mutual coupling within an array environment. Therefore, much effort has been made recently to realize high efficiency patch antennas on high permittivity substrates, including using the latest micromachining technology.[2,3]

The rate at which isoprene is emitted by a forest depends on an array of environmental variables, the forest’s biomass, and its species composition. At present it is unclear whether errors in canopy-scale and process-level isoprene emission models are due to inadequacies in leaf-to-canopy integration theory or the imperfect assessment of the isoprene-emitting biomass in the flux footprint. To address this issue, an isoprene emission model (CAN- VEG) was tested over a uniform aspen stand and a mixed-species, broad-leaved forest.\nThe isoprene emission model consists of coupled micrometeorological and physiological modules. The mi- crometeorological module computes leaf and soil energy exchange, turbulent diffusion, scalar concentration profiles, and radiative transfer through the canopy. Environmental variables that are computed by the micro- meteorological module, in turn, drive physiological modules that calculate leaf photosynthesis, stomatal con- ductance, transpiration and leaf, bole and soil/root respiration, and rates of isoprene emission.\nThe isoprene emission model accurately predicted the diurnal variation of isoprene emission rates over the boreal aspen stand, as compared with micrometeorological flux measurements. The model’s ability to simulate isoprene emission rates over the mixed temperate forest, on the other hand, depended strongly upon the amount of isoprene-emitting biomass, which, in a mixed-species forest, is a function of the wind direction and the horizontal dimensions of the flux footprint. When information on the spatial distribution of biomass and the flux footprint probability distribution function were included, the CANVEG model produced values of isoprene emission that compared well with micrometeorological measurements. The authors conclude that a mass and energy exchange model, which couples flows of carbon, water, and nutrients, can be a reliable tool for integrating leaf-scale, isoprene emission algorithms to the canopy dimension over dissimilar vegetation types as long as the vegetation is characterized appropriately.