All-optically induced currents resulting from frequency modulated coherent polarization

TL;DR

This study demonstrates a new class of optically induced photocurrents in GaAs quantum wells generated by frequency-modulated coherent polarization using ultrafast pulses, revealing complex current response behaviors.

Contribution

It introduces a novel method to generate and observe optically induced currents driven by frequency-modulated coherent polarization, expanding understanding of microscopic transport in semiconductors.

Findings

Photocurrents only occur with frequency-modulated coherent polarization.

Currents vanish at resonant excitation and reverse with detuning sign.

Continuous-wave excitation does not produce these currents.

Abstract

We employ polarization-shaped ultrafast optical pulses to generate photocurrents which only arise if the optically induced coherent polarization is frequency modulated. This frequency modulation is obtained via detuned excitation of light-hole excitons in (110)-oriented GaAs quantum wells. The observed photocurrents vanish for resonant excitation of excitons and reverse their direction with a change of the sign of detuning. Moreover, the currents do not exist for continuous-wave excitation. Our work reveals the existence of a new class of photocurrents and visualizes the complexity of current response tensors. This is helpful for the better understanding of optically induced microscopic transport in semiconductors.