Radio-frequency stress-induced modulation of CdTe/ZnTe quantum dots

TL;DR

This paper demonstrates GHz-range surface acoustic wave modulation of individual CdTe/ZnTe quantum dots, enabling dynamic spectral tuning and potential applications in single-photon polarization control.

Contribution

It introduces a method to modulate quantum dot energy levels using GHz SAWs on ZnTe, despite weak piezoelectricity, and employs photoluminescence as a nanoscale sensor.

Findings

QDs' energy modulated by GHz SAWs causes spectral broadening.

Time domain spectroscopy detects dynamic PL energy shifts.

SAW enables polarization control of single photons under magnetic field.

Abstract

We demonstrate radio-frequency tuning of the energy of individual CdTe/ZnTe quantum dots (QDs) by Surface Acoustic Waves (SAWs). Despite the very weak piezoelectric coefficient of ZnTe, SAW in the GHz range can be launched on a ZnTe surface using interdigitated transducers deposited on a c-axis oriented ZnO layer grown on ZnTe containing CdTe QDs. The photoluminescence (PL) of individual QDs is used as a nanometer-scale sensor of the acoustic strain field. The energy of QDs is modulated by SAW in the GHz range and leads to characteristic broadening of time-integrated PL spectra. The dynamic modulation of the QD PL energy can also be detected in the time domain using phase-locked time domain spectroscopy. This technique is in particular used for monitoring complex local acoustic fields resulting from the superposition of two or more SAW pulses in a cavity. Under magnetic field, the dynamic spectral tuning of a single QD by SAW can be used to generate single photons with alternating circular polarization controlled in the GHz range.