Generation and detection of mode-locked spin coherence in (In,Ga)As/GaAs quantum dots by laser pulses of long duration

TL;DR

This paper investigates how laser pulse duration affects the generation and detection of spin coherence in quantum dots, revealing that longer pulses and magnetic fields influence coherence efficiency through spin precession dynamics.

Contribution

It provides experimental and theoretical insights into the impact of pulse duration and magnetic field on spin coherence in quantum dots, a novel analysis in this context.

Findings

Longer laser pulses reduce spin coherence signals at given magnetic fields.

Magnetic field suppression of coherence depends on pulse duration.

Spin precession during pulses causes varying spin orientation, affecting readout efficiency.

Abstract

Using optical pulses of variable duration up to 80 ps, we report on spin coherence initialization and its subsequent detection in n-type singly-charged quantum dots, subject to a transverse magnetic field, by pump-probe techniques. We demonstrate experimentally and theoretically that the spin coherence generation and readout efficiencies are determined by the ratio of laser pulse duration to spin precession period: An increasing magnetic field suppresses the spin coherence signals for a fixed duration of pump and/or probe pulses, and this suppression occurs for smaller fields the longer the pulse duration is. The reason for suppression is the varying spin orientation due to precession during pulse action.