Research Investigation Directed Toward Extending the Useful Range of the Electromagnetic Spectrum
Abstract
We have made two important discoveries regarding the photon statistics in telecommunications devices. In the first, we have shown that the channel capacity of optical receivers in which photon arrival times are observed cannot be improved by modifying an initially Poisson photon stream and making it sub-Poisson. For photon-counting receivers, however, channel capacity enhancement is possible. In the second, we have evaluated system performance in the case of a cascade of fiber amplifiers. We have found that the photon-number distribution at the output of a cascade of erbium-doped fiber amplifiers, with coherent light at the input, turns out to be the noncentral-negative-binomial distribution, even in the presence of intervening loss. We have made significant advances in the investigation of the fundamental optical properties of semiconductors. For example, two relatively simple fractal renewal processes provide a framework for understanding charge transport in amorphous semiconductors; they give rise to spectral power densities with 1/f-like behavior. A new approach for enhancing exciton absorption and increasing the saturation limit in quantum wells, using tensile strain, is suggested; the method relies on valence-band mixing in a strained quantum well. The Auger recombination lifetime in a HgCdTe quantum wire is calculated to be shorter than that in a quantum well, but far shorter than that in a quantum box. Consequently, it seems that improved temperature performance can be expected from long-wavelength quantum-box lasers but not from quantum-wire lasers.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 31, 1992
- Accession Number
- ADA262704
Entities
People
- B. Bent
- E. Yang
- G. Flynn
- Isabella Herman
- M. Teich
- R. Osgood Jr.
- R. White
Organizations
- Columbia University