I. Brener

Terahertz emission from electric field singularities in biased semiconductors

Summary form only given. Fast electrical transients and terahertz (THz) radiation are generated when biased coplanar striplines are excited within the gap by short laser pulses. This generation process is particularly efficient when the excitation is carried out close to the anode and has been observed in a number of material systems. In this work we go one step further and use electric field singularities in metal-semiconductor microstructures to generate efficient THz radiation and electrical transients.

Cancellation of all Kerr nonlinearities in long fiber spans using a LiNbO/sub 3/ phase conjugator and Raman amplification

A LiNbO/sub 3/ phase-conjugator and Raman pumping in fiber are used in order to cancel all Kerr nonlinearities in long fiber spans. We demonstrate this effect in single and multichannel transmission at 10, 40, and 100 Gb/s.

Coherent control of terahertz emission and carrier populations in semiconductor heterostructures

A short laser pulse exciting semiconductor heterostructures will induce a time-varying polarization that in turn leads to the generation of terahertz radiation. Although there are several possible mechanisms for this time-dependent polarization, some depend critically on the dephasing time of the photoexcited carriers. For long dephasing times it is possible to control both the populations and the coherence of these particles by proper shaping of the optical pulse. We discuss our recent experimental and theoretical work on coherent terahertz radiation emitted from semiconductor heterostructures when the exciting optical fields are shaped in both amplitude and phase. Our shaping techniques include phase-locked pulse generation in a Michelson interferometer and pulse-train generation by phase-only filtering.

Repetitive excitation of charge oscillations in semiconductor heterostructures

We create forced excitonic charge oscillations in semiconductor heterostructures by excitation with periodic optical pulse sequences. The far‐infrared radiation that accompanies the charge oscillations shows temporal interference patterns for pulse sequences with different optical phase profiles, providing evidence for phase induced population transfers between exciton levels in a semiconductor.

Nonlinear optical study of the Fermi edge singularity: differences from atomic excitons in the virtual excitation regime

We discuss how the different nature of excitonic effects in modulation-doped quantum wells or metals (Fermi edge singularity) and undoped semiconductors (atomic excitons) manifests itself strongly in the nonlinear absorption spectrum for off-resonant pump excitation. We study this problem by extending our previous theoretical study of the Fermi edge singularity in linear absorption and obtain a new intuitive picture that extracts the physics conveyed by our experimental results. We point out that, in addition to phase-space filling, the pump-induced polarization increases the carrier effective masses and, as a result, can enhance excitonic resonances.

Polarization-insensitive parametric wavelength converter based on cascaded nonlinearities in LiNbO/sub 3/ waveguides

We developed a polarization-independent wavelength converter using periodically poled LiNbO/sub 3/ waveguides. The device uses a pump in the 1.5 mm band, has negligible polarization sensitivity and a penalty of less than 0.5 dB at 10 Gb/s.

High-resolution zero-dispersion wavelength fluctuation mapping in dispersion-shifted fiber

Summary form only given. Accurate dispersion management has become critical in high-speed wavelength-division multiplexing optical links. Several nondestructive techniques have been developed to measure the dispersion variations along the length of the fiber. However, occasionally very accurate information about the zero-dispersion wavelength (/spl lambda//sub 0/) is needed. Our technique provides a very accurate measurement of the spatial fluctuation of /spl lambda//sub 0/ and its spatial distribution. This technique, which uses four-wave mixing, can be applied also to measure the fluctuation in the chromatic dispersion and to other fibers /spl lambda//sub 0/ in the vicinity of 1.5 /spl mu/m.

Efficient wideband wavelength conversion using cascaded second-order nonlinearities in LiNbO/sub 3/ waveguides

We report on wavelength conversion and spectral inversion using cascaded second-order nonlinearity in periodically poled LiNbO/sub 3/ waveguides with an internal conversion efficiency of -8 dB, of more than 50 dB, and bandwidth of 76 nm.

Multiple channel wavelength conversion using engineered quasi-phase matching structures in LiNbO/sub 3/ waveguides

Summary form only given. Wavelength conversion based on difference frequency generation (DFG) is attractive for wavelength division multiplexed (WDM) optical networks. In this paper, we present DFG-based wavelength converters which use engineered quasi-phase matching (QPM) structures in LiNbO/sub 3/ (PPLN) waveguides, where the application of M pumps allows for simultaneous conversion of each of N input signals to M output wavelengths (wavelength broadcast).

Many-Body Effects at the Fermi Edge of Modulation Doped Semiconductors: a Numerical Study

Optical properties near the Fermi-edge of one-component Coulomb systems have been studied for more than half a century (for recent reviews see [1,2]). Originally the interest was focussed on x-ray spectra of metals. The development of modern crystal-growth technique allowed to realize similar systems in semiconductor materials. In these doped quantum-wells many-body effects which are responsible for the lineshape of optical spectra can be studied over a large range of densities applying the various tools of ultra-short time spectroscopy. The current interest in these systems results as well from the technological importance of them as from conceptual reasons, concerning basic aspects of quantum mechanics and manybody physics. Especially the study of nonlinear optical properties on an ultrashort timescale provides sensitive information about the relevant scattering processes which determine the dephasing and thus the lineshape of nonlinear spectra.