Hamidreza Siampour

University of Cambridge, UK

Title: Hybrid quantum photonics with nanodiamonds and plasmons

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Biography

Dr. Hamidreza Siampour is a Research Associate at the University of Cambridge working on diamond-based quantum nano-sensors. He received a PhD degree in Nano-optics from the University of Southern Denmark for his thesis "A Nanophotonic Platform for Quantum Optical Integrated Circuits". From Jun-2019 to Jan-2022, he was a postdoc at the University of Sheffield working on the development of a semiconductor nanophotonic platform for directional spin-photon coupling. As a Visiting Researcher at Ulm University (07/2018-09/2018), he investigated GeV centers in nanodiamonds coupled to plasmonic waveguides. Before that, he was working on the project of single-atom electronics at Shanghai Jiao Tong University (2013-2016) where he proposed and developed the idea of Si nanowire core-shell phototransistors based on two-photon-absorption phenomena at telecom wavelengths. From 2009 to 2013 he was a Research Assistant at Isfahan University of Technology, where he developed a sequential quadratic programming algorithm for solving inverse scattering problems based on non-radiating current reconstruction.

Abstract

Hybrid quantum photonic platforms combining different photonic elements in a single functional unit have great potential to leverage the strengths of individual subunits while avoiding their respective limitations. The desired functionality of such a hybrid integration relies on strong light-matter interaction at the single-photon level, and requires nanometre-scale fabrication precision and potentially involves a material diversity that is incompatible with standard nanotechnological processes. In this talk, I will discuss our developments in realization of hybrid integrated quantum photonic circuits based on dielectric-loaded plasmonic waveguides, containing accurately positioned nanodiamonds (NDs) with colour centres. This includes a top-down fabrication technique that was developed for accurate and deterministic positioning of waveguide components to incorporate NDs containing a single (nitrogen, silicon or germanium) vacancy centre1. Moreover, a chip-integrated cavity was demonstrated combining resonant and plasmonic enhancement to increase the spontaneous emission rate of single photons with up to 42-fold at the cavity resonance2. We have also demonstrated on-chip remote excitation of single quantum emitters by the plasmonic modes in dielectric ridges atop colloidal silver crystals3. Quantum emitters were produced by incorporating single germanium-vacancy (GeV) centres in NDs, providing bright, spectrally narrow and stable single-photon sources suitable for highly integrated circuits. Cryogenic characterization of GeV-NDs indicated symmetry-protected and bright zero-phonon optical transitions with up to 6-fold enhancement in energy splitting of their ground states as compared to that found for GeV centers in bulk diamonds (i.e. up to 870 GHz in highly strained NDs vs. 150 GHz in bulk)4.