Multiharmonic frequency-chirped transducers for surface-acoustic-wave optomechanics

TL;DR

This paper introduces multiharmonic frequency-chirped transducers for surface acoustic waves, enabling wideband, stable phase-locking with laser pulses, and demonstrates their application in quantum dot optomechanics and quantum information processing.

Contribution

The work presents a novel transducer design that combines multiharmonic split-finger architecture with frequency chirping to achieve wideband, efficient surface acoustic wave generation and phase-locking with laser pulses.

Findings

Achieved stable phase-locking at 320 MHz between acoustic waves and laser pulses.

Demonstrated wide frequency band generation for multiple harmonics.

Monitored quantum dot spectral modulation in time domain.

Abstract

Wide passband interdigital transducers are employed to establish a stable phase-lock between a train of laser pulses emitted by a mode-locked laser and a surface acoustic wave generated electrically by the transducer. The transducer design is based on a multi-harmonic split-finger architecture for the excitation of a fundamental surface acoustic wave and a discrete number of its overtones. Simply by introducing a variation of the transducer's periodicity $p$, a frequency chirp is added. This combination results in wide frequency bands for each harmonic. The transducer's conversion efficiency from the electrical to the acoustic domain was characterized optomechanically using single quantum dots acting as nanoscale pressure sensors. The ability to generate surface acoustic waves over a wide band of frequencies enables advanced acousto-optic spectroscopy using mode-locked lasers with fixed repetition rate. Stable phase-locking between the electrically generated acoustic wave and the train of laser pulses was confirmed by performing stroboscopic spectroscopy on a single quantum dot at a frequency of 320 MHz. Finally, the dynamic spectral modulation of the quantum dot was directly monitored in the time domain combining stable phase-locked optical excitation and time-correlated single photon counting. The demonstrated scheme will be particularly useful for the experimental implementation of surface acoustic wave-driven quantum gates of optically addressable qubits or collective quantum states or for multi-component Fourier synthesis of tailored nanomechanical waveforms.