Spectroscopy of two-dimensional quantum light sources incorporated into functional devices

Abstract

Two-dimensional materials are promising building blocks for photonic-based quantum technologies. Single-photon emitters – the required quantum light sources for such applications – can be induced in some of these layered materials, with the prevalent example of tungsten diselenide WSe2 monolayer. They can be incorporated into electronic and photonic devices, being combined with other atomically thin materials into tailored heterostructures and transferred onto patterned substrates. Ow ing to their intrinsic nature, these novel two-dimensional quantum systems present a promising potential to overcome challenges such as collection efficiency limitation due to total internal reflection encountered in other solide-state sources like semiconductor quantum dots or colour centres in diamond. This thesis undertakes the nanofabrication and optical characterisation of two-dimensional quantum light sources incorporated into devices. Four projects were achieved during the PhD. They are described and discussed in this thesis. A chapter is dedicated to an argon atmosphere glovebox system I developed for the nanofabrication, monitoring, and characterisation of pristine two-dimensional samples is described. Second, a dichromatic pulsed laser excitation regime is employed to coherently drive WSe2 monolayer quantum emitters incorporated into planar cavities, with a successful observation of π-pulses. Third, these emitters are excited out-of-resonance with a continuous wave laser, and their coherence time is estimated from a Hong-Ou-Mandel interferometry experiment. A short time of ∼ 10 ps – as compared to their ∼ ns lifetimes – is obtained; it is due to the emitters inhomogeneous broadening. Finally, cw resonant excitation of WSe2 monolayer quantum emitters coupled to a Si3N4 waveguide is successfully achieved.