Postgraduate research opportunities Generation of quantum light states with low-noise-VECSEL-pumped optical parametric oscillators
ApplyKey facts
- Opens: Friday 1 November 2024
- Deadline: Friday 7 February 2025
- Number of places: 1
- Duration: 4 years
- Funding: Equipment costs, Home fee, International fee, Stipend, Travel costs
Overview
This 4-year PhD project is part of the EPSRC-funded Centre for Doctoral Training in Applied Quantum Technologies. As well as completing a PhD project in an aligned topic, CDT students will also benefit from technical and skills-based training in all aspects of quantum technologies.Eligibility
All applicants must have or expect to obtain a first-class or second-class honours degree, or equivalent, in a relevant subject OR have or expect to obtain a Masters degree.

Project Details
Cavity-enhanced nonlinearities, in particular optical parametric oscillation (OPOs), are among the most widely used systems for the generation of non-classical states of light, of interest for several quantum applications, such as imaging [1], communication [2], and computing [3]. However, OPOs remain bulky and complex, especially when one accounts for the addition of the noise suppression required for typical laser sources. Vertical-external-cavity surface-emitting lasers (VECSELs), on the other hand, are capable of very low noise operation and are intrinsically shot-noise limited over a broad frequency range. Further they provide the means to embed the nonlinear process directly inside the laser cavity. Recently, our group demonstrated the use of a VECSEL as the pump source for a single-frequency OPO for the first time, achieving broadly tuneable, narrow linewidth at optical communications wavelengths [4], taking advantage of low noise and relaxation-oscillation-free laser dynamics. To-date, this intra-VECSEL cavity singly resonant OPO (VECSEL ICSRO), has undergone ‘standard classical’ characterisation only. In this project, we will investigate the quantum properties of the system for the first time, in a variety of operating regimes:
- Below threshold, OPOs are a source of squeezed vacuum, a quantum state typically exploited for achieving sub-shot noise sensitivity in optical interferometry and narrowband heralded single photons [5].
- Above threshold the OPO generates squeezed coherent states and intense twin beams, characterised by an intensity difference noise that is theoretically zero. These beams can then be exploited for sensing and metrology e.g. for high-sensitivity spectroscopy.
- Far above threshold (>4x threshold) can lead to regimes in which signal and idler beams are simultaneously individually squeezed in intensity, i.e. not only would their intensity be quantum correlated but the individual beams could also exhibit sub-shot-noise statistics. However, this is typically spoiled by the classical noise of the pump laser and by cavity relaxation oscillations. This has previously been experimentally realised in microcavity OPOs [6], owing to their low threshold of a few μW, where low noise pump lasers are easily available. A relaxation-oscillation-free VECSEL ICSRO could potentially target the realisation of sub-shot-noise laser beams at relatively high power (100s mW).
Demonstration of quantum states of light from a compact, highly stable, ultra-low noise VECSEL-based OPO platform will allow for the creation of transportable lasers for tests in quantum imaging and sensing, such as spectroscopy and sensitive trace gas-detection.
Further information
EPSRC Centre for Doctoral Training in Applied Quantum Technologies
Funding details
The funding provided for these fully funded PhDs will include four years of both tuition fees and monthly stipend payments.
Fully funded studentships are available at the UK home rate and international rate.
Home Students
To be eligible for a fully funded UK home studentship you must:
- Be a UK national or UK/EU dual national or non-UK national with settled status / pre-settled status / indefinite leave to remain / indefinite leave to enter / discretionary leave / EU migrant worker in the UK or non-UK national with a claim for asylum or the family member of such a person, and
- Have ordinary residence in the UK, Channel Islands, Isle of Man or British Overseas Territory, at the Point of Application, and
- Have three years residency in the UK, Channel Islands, Isle of Man, British Overseas Territory or EEA before the relevant date of application unless residency outside of the UK/ EEA has been of a temporary nature only and of a period less than six years
International Students
There are a limited number of international studentships for exceptional candidates who do not meet the UK home status mentioned above.
Candidates should check if they require an ATAS certificate; eligible nationalities are listed on GOV.UK (UK Foreign & Commonwealth Office).
International candidates whose first language is not English must demonstrate their proficiency in the English language with IELTS certification or equivalent.
While there is no funding in place for opportunities marked "unfunded", there are lots of different options to help you fund postgraduate research. Visit funding your postgraduate research for links to government grants, research councils funding and more, that could be available.
Supervisors

Primary Supervisor: Professor Jennifer Hastie
Secondary supervisors: Professor Alan Kemp, Dr Paulo Hisao-Moriya, Professor Lucia Caspani, Loyd McKnight (industry collaborator) (Fraunhofer)
Apply
Applications should be submitted via the AQT website in the first instance.
Number of places: 1
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