Biomedical subjects

N H Kwong

Publications and source records attributed to N H Kwong.

5 recordsLinked to original sources

PubMed2006

Large excitonic enhancement of optical refrigeration in semiconductors.

We present a theoretical analysis for laser cooling of bulk GaAs based on a microscopic many-particle theory of absorption and luminescence of a partially ionized electron-hole plasma. Our cooling threshold analysis shows that, at low temperatures, the presence of the excitonic resonance in the luminescence is essential in competing against heating losses. The theory includes self-consistent energy renormalizations and line broadenings from both instantaneous mean-field and frequency-dependent carrier-carrier correlations, and it is applicable from the few-Kelvin regime to above room temperature.

Journal Article↗

PubMed2005

Distortionless light pulse delay in quantum-well Bragg structures.

We describe a reflection scheme that allows Bragg-spaced semiconductor quantum wells to be used to trap, store, and release light. We study the temporal and spectral distortion of delayed light pulses and show that this geometry allows multibit delays and offers a high degree of distortion compensation.

Journal Article↗

PubMed2004

Quantum-dot quantum-interference infrared design proposal photodetector: and modeling of performance characteristics.

A novel design of an IR photodetector operating at wavelengths around 10 microm is presented. It is based on a three-level quantum coherence effect in semiconductor quantum dots as measured in balanced-homodyne detection in a Mach-Zehnder interferometer. The advantage of this design is the combination of room-temperature operation and fast response time, whereas the major drawback is the high noise-equivalent power.

Computer Simulation↗

PubMed2003

Electromagnetically induced transparency in semiconductors via biexciton coherence.

We report an experimental demonstration and theoretical analysis of electromagnetically induced transparency in a GaAs quantum well, in which the absorption of an exciton resonance is reduced by more than twentyfold. The destructive quantum interference in this scheme is set up by a control pulse that couples to a resonance of biexcitons. These studies illustrate that many-particle interactions, which are inherent in semiconductors and are often detrimental to quantum coherences, can also be harnessed to manipulate these coherences.

Journal Article↗

PubMed2001

Evidence for intervalence band coherences in semiconductor quantum wells via coherently coupled optical Stark shifts.

We report the experimental observation of coherently coupled heavy-hole-light-hole Stark shifts, i.e., light-hole exciton shifts under heavy-hole exciton pumping conditions, in InGaAs quantum wells. The theoretical analysis of the data is based on a full many-body approach (dynamics-controlled truncation formalism) in the third-order nonlinear optical regime. It is shown that the Stark shift data can be interpreted as strong evidence of suitably defined nonradiative intervalence band coherences in a semiconductor quantum well. Hence, the observations establish a semiconductor analog of Raman coherences in three-level atoms.

Journal Article↗