Quantum optomechanics explores the interaction between light and mechanical motion at a level where the quantised nature of light, or the zero-point fluctuations of motion, play a significant role. This project aims to leverage quantum optomechanical technologies, which have traditionally been used for fundamental quantum science research, to enable the next generation of acoustic sensors for Naval applications.
Quite generally, cavity optomechanical sensors consist of a mechanically compliant element coupled to a low loss optical cavity. When the mechanical element is exposed to an external force it is displaced in response. In the situation considered here, this force arises from an acoustic wave. The conversion from displacement to an optical response typically occurs via dispersive coupling, whereby the mechanical displacement alters the cavity length, and therefore the optical resonance frequency. The optical cavity serves to resonantly enhance the optical response to this displacement, enabling attometer displacement resolution and ultra-precise measurement of the acoustic wave.
The ultimate sensitivity of optomechanical sensors is set either by the thermal fluctuations of the mechanical element or by the intrinsic quantum mechanical properties of laser light, with the latter presenting an opportunity to further enhance performance by using non-classical states of light (i.e. squeezed light). The optical field also introduces quantum back-action on the mechanical element via radiation pressure forces, which can be used to control the acoustic state (i.e. effective temperature and resonant frequency) of the compliant mirror.
The optomechanical system considered in this project will build upon our recently developed device, which achieved a sensitivity two orders of magnitude better than existing in-air technologies when normalised to device area. Optimising the mechanical and optical properties of this device, with guidance from finite-element-modelling, is expected to enhance the performance by at least one order-of-magnitude.
To achieve the objectives outlined in the previous section, the PhD student must first become proficient in finite-element modelling (FEM) of mechanical and optical structures using COMSOL. Parallel to developing FEM simulations, the PhD student will be trained in the advanced fabrication techniques/strategies required to reliably make high quality optomechanical devices. This training will be performed within the Australian National Fabrication Facility node located at UQ.
After fabricating devices, the characterisation of sensing capabilities will require constructing a quantum limited fibre-based interferometer. Indeed, this is an area of research in which Prof. Bowen’s laboratory has substantial expertise.
The final activity of this project will be to surpass the sensitivity limits set by the quantum properties of laser light, such as those in our previous demonstration of an optomechanical acoustic sensor, by exploring the use of quantum correlated light (i.e. squeezed light) to further improve sensitivity.
Beyond activities directly associated to the project, there will be domestic and international travel to build further collaborations and present/attend at international conferences and workshops.
Eligibility / Selection Criteria
Applicants should hold, or expect to receive, a First Class Honours degree (or the equivalent) in physics and have an interest in quantum optomechanics and/or photonics based sensing.
How to apply
Prospective students email their documents directly to the advertising academic/s who make a decision and then invite their preferred applicant to submit a full application for admission. If choosing this option, students need to be aware that emailing their documents to a potential supervisor does not constitute submitting a full application. This option can cause delays because the student has to gather and submit the required documents after they have been selected. HLOs are never involved in this process. It is strictly managed by the academic.
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• To be considered for this scholarship, please email the following documents to Professor Warwick Bowen [email protected]
or Dr Glen Harris [email protected]
• Cover letter
• Academic transcript/s
Please note the following: Submitting the above documents does not constitute a full application for admission into The University of Queensland's PhD program. If you are selected as the preferred applicant, you will then be invited to submit a full application for admission. You can familiarise yourself with the documents required for this process on the Graduate School's website (https://graduate-school.uq.edu.au/node/69/2#2