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N Peyghambarian

Publications and source records attributed to N Peyghambarian.

At least 19 recordsLinked to original sources
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↗
PubMed2001

Two-photon resonant third-harmonic generation in La2CuO4.

Combining linear absorption and nonlinear third harmonic generation (THG) experiments, we investigate details of the electronic structure of the highly correlated electronic system in La2CuO4. We demonstrate strong THG mainly due to the charge transfer excitation from O (2p(sigma)) to Cu (3d(x2-y2)). The THG spectrum shows pronounced features due to three-photon and two-photon resonance enhancement as well as quantum interference effects. We obtain excellent agreement with a THG spectrum calculated in terms of the excitonic cluster model and can identify both odd and even symmetry excitation modes.

Journal Article↗
PubMed1998

Infrared photorefractive polymers and their applications for imaging.

Photorefractive polymers with high diffraction efficiency in the visible and near-infrared regions of the electromagnetic spectrum have been developed. These polymers, which have a large dynamic range because of their high orientational birefringence, incorporate a dye designed to have a large dipole moment and a high linear polarizability anisotropy. Such polymers have enabled demonstrations of imaging through scattering media, using a holographic time-gating technique at a wavelength that is compatible with the transparency of biological tissues and with the emission of low-cost semiconductor laser diodes.

Birefringence↗