Multiharmonic Frequency-Chirped Transducers for Surface-Acoustic-Wave Optomechanics

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 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 multicomponent Fourier synthesis of tailored nanomechanical waveforms.{|}~\ and rate \] were incommensurate ( \] ≠ • {|}~\ , being integer) to average the dynamic modulation of the QD over a full rf cycle in a single time-integrated spectrum [71].Phase-locked excitation with tunable laser of fixed repetition rate

Distinctive characteristics of carrier-phonon interactions in optically driven semiconductor quantum dots

“…First examples where phonons coupled to semiconductor quantum dots improve application relevant properties include the here discussed phonon-assisted state preparation [23,[25][26][27]218], the establishment of off-resonant QD-cavity couplings [28][29][30][31][32][33][34][35][36], the phonon mediated brightness enhancement of dots detuned from an embedding cavity [260], the possibility to enhance the photon purity with excitations spectrally separated from the excitation [288], a high cavity-photon feeding efficiency that is robust against variations of the driving frequency [37] as well as the possibility to trigger simultaneous photon emission from remote quantum dots with different transitions frequencies [218]. Further applications comprise lasing manipulated by phonon pulses [289][290][291], position sensing using phonon shifts [292] or modulations of quantum dots via surface acoustic waves [293][294][295][296]. In view of these developments future devices can be expected to benefit from phonons rather than being limited in their functionality.…”

Quantum Dot Optomechanics in Suspended Nanophononic Strings

“…First, multi‐passband IDTs were fabricated in a standard lift‐off process using a Cr/Au (5 nm/50 nm) metallization which is inert to hydrofluoric acid (HF) etching employed to release the nanophononic strings.…”

“…Most strikingly, the broadening observed for the QD inside the nanophononic string is largely enhanced compared to the QD in the unpatterned region. The observed broadening can be described by a Lorentzian line modulated in time with a frequency It is given by in which and w denote the amplitude of the optomechanical modulation and the unperturbed linewidth of the QD emission line, respectively. Best fits of Equation (full lines in Figure b,c) faithfully reproduce the experimental data and allow us to quantify to be 0.23 and 1.40 meV for the Rayleigh SAW and on the nanophononic string, respectively.…”

Remote Phonon Control of Quantum Dots and Other Artificial Atoms

“…[ 70 ] While in the introduced geometry only a single SAW frequency can be launched, new developments use more sophisticated finger patterns of the IDT that allow to tune the SAW frequency between a few hundred MHz and a few GHz in a single device. [ 71 ] To reach smaller frequencies, one can follow a wave mixing approach and reach frequencies below the Hz range by difference frequency generation of slightly detuned SAWs. [ 72 ] Reviews that treat the current status and future perspectives of SAWs can be found in refs.…”

“…a) Schematic picture of the sample structure. Reproduced under the terms of a Creative Commons Attribution 4.0 License (CC-BY) [71]. Copyright 2018, The Authors, published by the American Physical Society.…”