Quantum-enhanced THz spectroscopy and imaging

Lead Research Organisation: University of Glasgow
Department Name: School of Engineering

Abstract

Quantum mechanics promises to be the driving force underneath the next technological revolution, and quantum cryptography, providing a commercial solution for the ultimate security, may well be considered the harbinger of this change. With this proposal, we aim at showing how quantum mechanics can allow to overcome the limits faced in the detection of long wavelength radiation, specifically at terahertz frequencies.

Terahertz is a portion of the electromagnetic spectrum that is both extremely hard to access to, and incredibly important from a technological standpoint. It is indeed a key player in security (explosives, drugs, and hazard-free concealed weapons detection), telecommunications (increased data-rate of short distance wireless communication), monitoring and quality control (spectroscopy). Despite its high potential, the lack of efficient sources and detectors prevents a widespread commercial application of terahertz time-domain spectroscopy and imaging.

Yet, a number of high-tech companies are investing into terahertz technology and recent market studies hint for a 40%/year increase in the turnover associated to this technology.

It is therefore vital to identify now strategies for overcoming the limitations of the current terahertz detectors. This proposal aims at developing such a strategy exploiting the unique properties of quantum, entangled states of light.

Entangled photons, separated in space but sharing a common wavefunction, can be generated by commercial nonlinear crystals and boost unusual properties not accessible by classical means. Two of these properties, namely the ability to acquire twice the phase of a classical state upon propagation and the reduced amplitude noise below the classical shot-noise limit, offer a mean for increasing the sensitivity of terahertz time-domain detectors, that operate indeed as a differential phase sensor. Combining such an improvement with recent concepts of super-resolved imaging will also result in an increased resolution of long wavelength mapping.

Combining for the first time concepts of quantum optics, recognised as a main pillar for our future technology, and of terahertz photonics, boosting a number of underdeveloped application potential, this proposal is in line with the research strategy set by the UK research councils, and promise to deliver impact on a number of different disciplines, such as biology and material science, as well as on the quality control and security inspection activities.

Planned Impact

This proposal aims at developing an application of quantum optics targeting an increase in our detection capability in the terahertz portion of the electromagnetic spectrum.

The majority of the research on quantum optics so far addressed fundamental questions, however the amount of knowledge accumulated has now reached the critical mass able to deliver high-impact technologies. This is the main drive underneath the multi-million pounds' investments in quantum-related researches by Canada, US, EU, Japan and for the 270 million pounds the UK Government has devoted to quantum technologies research via the UK National Quantum Technologies Programme. On the other hand, the terahertz spectral region is extremely important from a technological standpoint as it offers advantages compared with competing technologies in fields such as biological and medical imaging, security inspection, quality control and telecommunications. Several UK companies such as Teraview, QMC-instruments and ThruVision Systems, as well as other international players (Menlo Systems, Toptica, Rainbow Photonics, TeTechs, Gentec) are developing technologies and investing to secure their share in what is expected to be a billion pounds' market, by 2024 (BCC news source). Therefore, the success of this project will both contribute to develop a strategic scientific objective and to a growing commercial opportunity.

- Academy. From an academic perspective, the impact will be delivered thanks to a direct engagement with the staff from the Glasgow-led Quantum Hub (QuantIC), and via an intense and and effective dissemination strategy encompassing participation to international conferences, publication of journal papers and collaborations with world renown leaders in the area of research tackled by the proposal, as described in the Academic beneficiaries section.

- Economy. The commercial potential will be tested thanks the active participation to the research efforts of an international industrial partner (TeTechS, CA), the support and the precious feedbacks from a UK leading terahertz company (QMC-instruments), the possibility to access the QuantIC 4M£ Partnership Resource Fund and to obtain the expert feedback on technology transfer matters from the QuantIC Business Development Manager, part of the Hub support package.

- Society. To improve the social impact of this project we plan to perform outreach and public engagement activities with the aim of educating the public on basic concepts of quantum mechanics and the role they will play in the forthcoming technology. Also in this case an effective strategy will be devised with the support of the QuantIC Hub, via the help of its Public Engagement and Communication Officer. In addition, to maximise the effectiveness of the communication, we shall rely on the professional work of graphic designers for the preparation of dissemination material.
 
Description This project aims at investigating the impact of quantum optics in the spectroscopy and imaging at THz frequencies. The main achievements are:
1) New ways of detecting THz radiation by mixing the unknown field with a short pulse in a transparent medium (Photonics 2017, Optica 2018). Two approached has been followed, both based on centrosymmetric, large bandgap dielectric materials (Fused Silica and Diamond). In the first case, an effect similar to cross-phase modulation has been used to generate a visible signal from the nonlinear interaction between an unknown THz field and a probe pulse. In the second case, the electric-field-induced second harmonic generation effect was used to detect THz radiation in an engineered chip-size detector.
2) New applications for THz spectroscopy and imaging, for the study of Ancient artefacts (Physical Review Applied 2017). We have studied how THz spectroscopy can determine the ageing stage of cellulose, and we applied the finding to investigate the difference between natural and artificial ageing of cellulose-based artefacts.
3) Design of a new scheme for the detection of THz radiation using quantum light in intracavity phase interferometry, supported by a newly started collaboration (D.C Diels, University of New Mexico, UK). This led to a successful bid to the EPSRC Impact Acceleration Account and the engagement of two new industrial partners (Covesion, and Chromacity, both UK SMEs). This research is now developing and will be part of further projects.
4) We succeed in the study on new ways to produce the broadband radiation required for measuring THz pulses in the time-domain, well suited for the nonclassical case (Optics Express 2018). To this end, we increased the efficiency of parametric down conversion and amplification over a broad bandwidth using a temperature gradient in a non-critically phase matched nonlinear crystal (LBO).
5) Finally, we have been studying physics and the material properties of time-varying media as they are a promising source of squeezed (nonclassical) radiation at THz and optical frequencies. This resulted in two publications in high-impact journal (Nature Communications 2018, Physical Review Letters 2018).
Exploitation Route A successful demonstration of improved detection of THz radiation with nonclassical radiation has expected impact on the healthcare and security sectors, as well as pharmaceutical and the study of cultural heritage. All these fields indeed benefit from increased sensitivity in THz spectroscopy and imaging. The PI has taken part in local engagement activities (Glasgow Crucible) where he had the chance to meet with local expertise which eventually resulted in the onset of a new collaboration. Chromacity is a local company that is indeed interested in exploit the potential of enhanced THz time-domain spectroscopy and is working with the PI towards the projects' goal.
While it is still too early to see the impact of the outcomes obtained so far, the application of the new detection techniques discovered (Optica 2018) could be licensed from laser manufacturing companies, such as Chromacity, to broaden the bandwidth of THz time-domain spectroscopy. At the same time, the knowledge developed on the broadband amplification via autoresonant phase matching (Optics Express 2018) could be exploited by another partner of the PI (Covesion) that is contributing to the development of nonclassical states of light for metrological and communications applications.
Sectors Education,Healthcare,Manufacturing, including Industrial Biotechology,Culture, Heritage, Museums and Collections,Pharmaceuticals and Medical Biotechnology,Security and Diplomacy

URL http://www.teoclerici.com
 
Description The results of this project triggered the collaboration with Chromacity and Covesion. Although the findings were not directly transferred outside the academy; they had an impact in engaging with the two companies.
First Year Of Impact 2018
Sector Other
Impact Types Cultural,Economic

 
Description An alternative approach to quantum-enhanced THz generation
Amount £31,581 (GBP)
Organisation University of Glasgow 
Department University of Glasgow Impact Acceleration Award
Sector Academic/University
Country United Kingdom
Start 11/2017 
End 04/2018
 
Title Broadband and efficient adiabatic three-wave-mixing 
Description  
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title Phase-insensitive Scattering of Terahertz Radiation 
Description  
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
 
Title Solid-state-biased coherent detection of ultra-broadband terahertz pulses 
Description  
Type Of Material Database/Collection of data 
Year Produced 2017 
Provided To Others? Yes  
 
Description IPI 
Organisation Chromacity Ltd
Country United Kingdom 
Sector Private 
PI Contribution The PI proposed a new way to detect THz radiation by using Intracavity Phase Interferometry. He desgined the experimental system required to test this technique.
Collaborator Contribution Covesion provided support and material on the nonlinear crystal required for the optical parametric oscillator. Chromacity provided technical support on the design and stabilisation of the oscillator and supported the activity with a dedicated laser system. Professor Jean-Claude Diels (University of New Mexico) provided support on the design of the detector and the basic concepts underlying intracavity interferometry based measurements.
Impact This activity is still ongoing.
Start Year 2017
 
Description IPI 
Organisation Covesion Ltd
Country United Kingdom 
Sector Private 
PI Contribution The PI proposed a new way to detect THz radiation by using Intracavity Phase Interferometry. He desgined the experimental system required to test this technique.
Collaborator Contribution Covesion provided support and material on the nonlinear crystal required for the optical parametric oscillator. Chromacity provided technical support on the design and stabilisation of the oscillator and supported the activity with a dedicated laser system. Professor Jean-Claude Diels (University of New Mexico) provided support on the design of the detector and the basic concepts underlying intracavity interferometry based measurements.
Impact This activity is still ongoing.
Start Year 2017
 
Description IPI 
Organisation University of New Mexico
Department Department of Physics and Astronomy
PI Contribution The PI proposed a new way to detect THz radiation by using Intracavity Phase Interferometry. He desgined the experimental system required to test this technique.
Collaborator Contribution Covesion provided support and material on the nonlinear crystal required for the optical parametric oscillator. Chromacity provided technical support on the design and stabilisation of the oscillator and supported the activity with a dedicated laser system. Professor Jean-Claude Diels (University of New Mexico) provided support on the design of the detector and the basic concepts underlying intracavity interferometry based measurements.
Impact This activity is still ongoing.
Start Year 2017
 
Description Jean Claude Diels 
Organisation University of New Mexico
Country United States 
Sector Academic/University 
PI Contribution We have contacted Professor Jean-Claude Diels to establish the possibility of using Intracavity Phase Interferometry, a technique he invented, for the detection of THz radiation. We have designed the optical cavity and the detection scheme.
Collaborator Contribution The new partnership with Professor Jean-Claude Diels was instrumental in determining a novel method to detect THz radiation, which is currently under investigation, based on Intracavity Phase Interferometry. He provided feedback and contributed with the know-how on cavity design. He is also coming to the University of Glasgow for a round of measurements funded by the University of Glasgow Impact Accelerator Account.
Impact Currently we are still working on the cavity design.
Start Year 2017