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Auger recombination carrier lifetimes in HgCdTe quantum wires and quantum boxes with band gaps in the two to five micrometer range were investigated. The results showed that the Auger recombination lifetime in a quantum wire was shorter thanthat observed in quantum wells, and the increased state density resulted in decreased wire width. However, there was no Auger recombination observed in a quantum box.

Tensile strain was used to enhance exciton absorption and to increase the saturation limit in quantum wells. The results showed that in-plane hole mass was either very large or negative because of the valence-band mixing in a strained quantum well, and this resulted in heavy exciton mass and small exciton radius. Exciton absorption was observed to increase due to the larger electron-hole overlap probability.

Two relatively simple renewal processes whose power spectral densities vary as 1/f(super D) are constructed: 1) a standard renewal point process, with 0 < D < 1; and 2) a finite-valued alternating renewal process, with 0 < D < 2. The resulting event number statistics, coincidence rates, minimal coverings, and autocorrelation functions are shown also to follow power-law forms. These fractal characteristics derive from interevent-time probability density functions which themselves decay in a power-law fashion.

This paper reports a novel recurrence theory that enables us to calculate the exact joint probability density function (pdf) of the random gain and the random avalanche buildup time in avalanche photodiodes (APDs) including the effect of dead space. Such calculations reveal a strong statistical correlation between the gain and the buildup time for all widths of the multiplication region. To facilitate the calculation of the photocurrent statistics in the presence of this correlation, the impulse-response function of the APD is approximately modeled by a function of time whose prespecified shape is appropriately parameterized by two random variables: the gain and the buildup time. The evaluation of the variance of the photocurrent under this model leads to the definition of the shot-noise-equivalent bandwidth of the APD, which captures the statistical correlation between the gain and the buildup time. It is shown that the shot-noise-equivalent bandwidth in GaAs APDs is greater, by approximately 30%, than the traditional buildup-time-limited 3-dB bandwidth, which is calculated from the mean of the impulse-response function. A thorough analysis of the performance of APD-based integrate-and-dump digital receivers reveals that the strong correlation between the gain and the buildup time accentuates intersymbol interference (ISI) noise, and thus, adversely affects receiver sensitivity at high transmission rates beyond previously known limits. [ABSTRACT FROM PUBLISHER]

A generalized history-dependent recurrence theory for the time-response analysis is derived for avalanche photodiodes with multilayer, heterojunction multiplication regions. The heterojunction multiplication region considered consists of two layers: a high-bandgap Al0.6Ga0.4As energy-buildup layer, which serves to heat up the primary electrons, and a GaAs layer, which serves as the primary avalanching layer. The model is used to optimize the gain-bandwidth product (GBP) by appropriate selection of the width of the energy-buildup layer for a given width of the avalanching layer. The enhanced GBP is a direct consequence of the heating of primary electrons in the energy-buildup layer, which results in a reduced first dead space for the carriers that are injected into the avalanche-active GaAs layer. This effect is akin to the initial-energy effect previously shown to enhance the excess-noise factor characteristics in thin avalanche photodiodes (APDs). Calculations show that the GBP optimization is insensitive to the operational gain and the optimized APD also minimizes the excess-noise factor. [ABSTRACT FROM PUBLISHER]

We analyse the quantitative improvement in performance provided by a novel quantum key distribution (QKD) system that employs a correlated photon source (CPS) and a photon-number resolving detector (PNR). Calculations suggest that given current technology, the CPS/PNR implementation offers an improvement of several orders of magnitude in secure bit rate over previously described implementations. [ABSTRACT FROM AUTHOR]

Discusses new techniques to `squeeze' the uncertainty of light, which is allowing researchers to conduct experiments with greater precision than possible with laser light. Nonclassical light; Mathematical representation of electromagnetic field;Graphical representation; Quadrature-squeezed light; Antibunched light; Photon-number-squeezed light; Applications.