C. Klingshirn

Quantum‐confined Stark effect in InGaAs/InP quantum wells grown by organometallic vapor phase epitaxy

We report the first observation of the quantum‐confined Stark effect in InGaAs/InP multiple quantum wells grown by organometallic vapor phase epitaxy. The effect is observed both in transmission and photoconductivity measurements. The observed spectral shift agrees with the theory.

Modulation of absorption in field-effect quantum well structures

Experimental and theoretical investigations of the absorption in a single-modulation-doped quantum well (QW) used as conducting channel of a field-effect transistor are presented. By applying a voltage to the gate, the electron concentration can be varied between 0 and approximately 10/sup 12/ cm/sup -2/. The continuous transition can be optically followed from an undoped to a highly doped QW. Effects of band filling are observed, along with renormalized effects at the first subband edge and electrostatic effects at the higher ones. It is shown that optical techniques can give in situ information on the electron density and temperature as well as on the electrostatic fields inside field-effect structures. >

Optical reading of field-effect transistors by phase-space absorption quenching in a single InGaAs quantum well conducting channel

We present the first observation of absorption quenching by electrical control of the carrier density in a single semiconductor quantum well used as conducting channel in a field‐effect transistor. The effect is large enough to allow direct reading of the transistor logic state.

Degenerate and nondegenerate four-wave mixing and laser-induced gratings in CdS

Abstract Using CdS as a model substance, we present new results in the spectroscopy with laser-induced gratings. We investigate self-diffraction in reflection and transmission, the diffraction of a probe beam and nondegenerate four-wave mixing.

Picosecond transient gratings in CdS1−xSex mixed crystals

Abstract We performed transient grating experiments to study various relaxation processes of localized excitons in CdS1xSex mixed crystals. At low temperatures we observe a strong nonlinear response, spectrally in the localized states. We measured the phase relaxation time of localized excitons with a correlation technique. At low excitation levels we found long phase relaxation times of 75 ps. In a three beam configuration of a transient grating experiment we investigated the recombination as well as the diffusion of excitons within the localized states. We observed a reduced mobility compared to the mobility of free excitons in the pure compounds and found diffusion coefficients D

Optical nonlinearities of quasi two-dimensional excitions under various excitation conditions

Abstract Excitonic nonlinearities under nonresonant, quasi-stationary excitation conditions in a GaAs/AlGaAs multiple quantum well structure are investigated. By detuning the pump laser below the lowest heavy hole resonance, we find the first hint of the AC Stark effect in this excitation regime. In another series of experiments we study the light hole to heavy hole relaxation dynamics under ps excitation. Long transition times, exceeding 500 ps, are observed.

Novel low-power optical nonlinearity in semiconductor quantum well electro-optic effect devices

We report a new type of GaAs/AlGaAs electro‐optic effect device which offers a built‐in optical nonlinearity at extremely low power operation working in the pW to μW regime. The device consists of semitransparent metal electrodes evaporated directly onto the undoped AlGaAs cladding layers of a multiple quantum well structure. We briefly characterize the optical nonlinearity which is based on the quantum‐confined Stark effect and discuss the underlying physical mechanism which relies on the suppression of the internal electric fields of the biased sample. The use of such structures is proposed especially for applications as possible low‐power and low‐cost optical bistable switch.

Optical Reading of InGaAs Modulation Doped Field Effect Transistor

We present the first observation of absorption quenching in a semiconductor quantum well by electrical control of the carrier density. We have observed this novel effect at room temperature in a single modulation-doped InGaAs quantum well which was used as the conducting channel of a field effect transistor. The effect is extremely large and we have used it for direct optical determination of the state of the modulation doped field effect transistor (MODFET).

Quantum-Confined Stark Effect in InGaAs/InP Quantum Wells Grown by Metal-Organic Chemical Vapor Deposition

Large shifts of absorption spectrum in InGaAs/InP multiple quantum wells with applied electric fields are reported. Applications for light modulators are discussed.