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Physics Seminar

Optical control of colour centres in hexagonal boron nitride

Speaker: Isaac Luxmoore (University of Exeter)
Date: Wednesday 30 March 2022
Time: 15:00
Venue: N/3.28

Colour centres in the two-dimensional semiconductor, hexagonal boron nitride (hBN), show considerable promise as room temperature quantum emitters, with high-brightness, narrow photoluminescence linewidths and a zero phonon line fraction that can reach 80%. Furthermore, investigation into the electronic behaviour of these defects has established that some species have spin levels that are addressable via optically-detected magnetic resonance (ODMR), providing a route for hBN colour centres to be exploited in quantum information processing and/or quantum sensing applications.

In the first part of this talk I will discuss our multicolour excitation experiments with colour centres that have zero phonon line emission around 2 eV. Firstly, we demonstrate controllable optical switching with different colour lasers as a method to photo-ionize and photo-charge between optically bright and dark states of the colour centres. Secondly, we use stimulated emission depletion (STED) as a spectroscopic probe, complementary to photoluminescence excitation spectroscopy, and reveal differences between the electron-phonon interaction in the ground and excited states. Thirdly, we show that hBN colour centres are a viable fluorophore for STED imaging, achieving a spatial resolution of ~50 nm. In the second part of the talk I will discuss our recent ODMR experiments with an ensemble of negatively charged boron vacancies. In this work, we use a time-resolved ODMR technique to probe the electronic structure of these defects. We extract the spin-dependent intersystem crossing rates and detect the spin of the optically excited state, where a zero-field splitting of ~2.1 GHz is measured.

Short bio: Isaac Luxmoore studied Electronic Engineering at the University of Sheffield, gaining his PhD in 2009 for work on focused ion beam processing of superconducting and optoelectronic devices. Isaac subsequently joined the Physics Department at Sheffield, where he worked for four years on III-V semiconductor quantum dots, photonic crystals and nanophotonic integration. In 2012 Isaac joined the University of Exeter as a research fellow, working on graphene-based optoelectronic devices for mid-IR and THz applications, with a focus on graphene plasmonics, before taking on a Lectureship in May 2016. The common theme in Isaac’s research is nanofabrication, working with a wider range of materials and techniques. His current research interests are focused on the photonic integration of 2D materials for a range of applications, including quantum technology, THz devices and bio-sensing.