Ultraviolet laser written devices for quantum photonics

Abstract

Photonic platforms play a key role in quantum technology. Silicon nitride integrated photonics is emerging as a promising photonic quantum platform due to its low loss and ease of integration into semiconductor fabrication pipelines. Photonic crystal fibre can be a practical quantum light source for photonic-based quantum networks. This thesis explores controlled UV exposure, applied to these these two platforms, as well as commercial fibre for advancing quantum technology. In this thesis, fibre Bragg gratings are UV written into PCF, integrating filtering for single photon sources. Fibre Bragg gratings are also fabricated in PCF with the goal of making a fibre optical parametric oscillator. This is to be used to generate a squeezed vacuum. Additionally, in this work, silicon nitride UV photosensitivity is demonstrated and quantitatively investigated in both PECVD and LPCVD silicon nitride layers. The latter is achieved by applying hydrogen loading. The maximum refractive index changes in these layers are found to be 0.05 and 0.006, respectively. This allows for the passive fine-tuning of resonant components, such as ring resonators and MZIs on chips, which are interesting for quantum photonic circuits. This mechanism also allows for the first demonstration of laser-written Bragg gratings in silicon nitride. A refractive index modulation of 2.4x10−4 is shown, comparable to that typically used in Ge-doped fibre Bragg gratings. This thesis also investigates the use of fibre Bragg gratings in commercial fibre for new single-photon pair generation applications. Two proposals are made. The first is the use of π-phase shifted, 3rd order Moiré gratings for use as a short, fibre pair source of high purity, narrow spectral width and enhanced brightness. For this, a model of triply resonant spontaneous four-wave mixing is constructed. The second proposal is the use of the intra-cavity field of a fibre Brillouin laser as a source of pump light for photon pair generation. The second is experimentally tested and shown to produce correlated pairs using low pump powers in SMF 28 fibre.

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Identifiers

ORCID for Alexander Iain Flint: orcid.org/0000-0001-5103-0419

ORCID for James Gates: orcid.org/0000-0001-8671-5987

ORCID for Peter G.R. Smith: orcid.org/0000-0003-0319-718X

ORCID for Rex Bannerman: orcid.org/0000-0002-1428-6308

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