Dynamic Strain Modulation of a Nanowire Quantum Dot Compatible with a Thin-Film Lithium Niobate Photonic Platform

Abstract

The integration of indistinguishable single photon sources in photonic circuits is a major prerequisite for on-chip quantum applications. Among the various high-quality sources, nanowire quantum dots can be efficiently coupled to optical waveguides because of their preferred emission direction along their growth direction. However, local tuning of the emission properties remains challenging. In this work, we transfer a nanowire quantum dot onto a bulk lithium niobate substrate and show that its emission can be dynamically tuned by acoustooptical coupling with surface acoustic waves. The purity of the single photon source is preserved during the strain modulation. We further demonstrate that the transduction is maintained even with a SiO 2 encapsulation layer deposited on top of the nanowire acting as the cladding of a photonic circuit. Based on these experimental findings and numerical simulations, we introduce a device architecture consisting of a nanowire quantum dot efficiently coupled to a thinfilm lithium niobate rib waveguide and strain-tunable by surface acoustic waves.

Widely tunable solid-state source of single-photons matching an atomic transition

“…In recent years, various techniques have been reported that achieved tuning of the QD emission but many are not suitable for NW-QDs. The QD-emission tuning techniques include stress-induced wavelength shift by piezoelectric actuators [10][11][12][13][14][15], laser-induced crystallization of the surrounding environment [16], thermal [17] and laser annealing [18], local electric Stark field [19], temperature-controlled tuning in a QD microlens [20], surface acoustic wave (SAW) modulation [21][22][23], laser-induced atomic intermixing in NW-QDs [24], stress induced by depositing dielectric material (SiO 2 ) on the nanowire surface [25], and external magnetic fields applied to NW-QDs [26]. However, these techniques often come with significant limitations and only few of them allow independent tuning of multiple quantum dots on the same chip.…”