New Publication: Tunable pseudo-magnetic fields for polaritons in strained metasurfaces

Congratulations to final year PhD student Charlie-Ray Mann whose theory paper, entitled ‘Tunable pseudo-magnetic fields for polaritons in strained metasurfaces’, has been published in the prestigious journal Nature Photonics.

The work has also been featured on the University of Exeter’s news website.

Charlie-Ray Mann, the lead scientist and author of the study, explains:

Charlie-Ray Mann- lead scientist and author of the paper published in Nature Photonics

The interaction between charged particles and magnetic fields gives rise to some of the most fascinating phenomena in physics, ranging from the beautiful Aurora Borealis to the famous quantum-Hall effect. Unfortunately, because photons do not have an electric charge they are inert to real magnetic fields as they do not experience a Lorentz force.

Taking inspiration from graphene physics, we have shown that you can generate `artificial’ magnetic fields for light by distorting honeycomb metasurfaces in a specific way. These distortions generate a ‘synthetic’ Lorentz force which can deflect the surface polaritons into effective cyclotron orbits, and for larger distortions one can also observe Landau quantization of the polaritons — phenomena once thought to be exclusive to charged particles.

However, the main drawback with this approach is that to change the artificial magnetic field one is usually required to modify the distortion in the lattice. This is extremely challenging, if not impossible to do with photonic structures, hindering our ability to tune the artificial magnetic field after the structure has been fabricated — that is, the artificial magnetic fields are usually fixed by design.

In this theoretical work we have proposed an alternative mechanism to tune the artificial magnetic fields, which requires no change to the metasurface distortion. By exploiting the hybrid light-matter character of the surface polaritons, we show that one can tune the artificial magnetic field by modifying the real electromagnetic environment surrounding the metasurface.

Specifically, we’ve shown that by embedding the metasurface inside a photonic cavity or waveguide, one can tune the artificial magnetic field by modifying a single external parameter: the cavity width. In fact, we’ve even demonstrated that you can switch off the artificial magnetic entirely at a critical cavity width, without having to remove the distortion in the metasurface — something that is impossible to do in graphene or any system that emulates graphene.

Using this new mechanism you can bend the trajectory of the polaritons using a tunable Lorentz-like force that can be switched on/off, and you can drastically reconfigure the polariton Landau level spectrum by simply changing the cavity width.

Earlier this year, Charlie-Ray Mann was awarded a £5,000 prize from the Rank Prize Funds 2020.

Emanuele Gemo and Joaquin Faneca present at Photonic West conference

Fourth year students Emanuele Gemo and Joaquin Faneca recently attended Photonic West, the biggest conference in the world of photonics, which was held in San Francisco, Moscone centre. In this conference, Emanuele was presenting his work based on “Sub-wavelength plasmonic enhance phase change memory”. Joaquin Faneca was giving an oral presentation relating to his work on “Reconfigurable integrated circuits based on functional materials” and a poster called “On-chip sub-wavelength Bragg grating design based on GSST”.

Emanuele Gemo presenting
Joaquin Faneca presenting

Ioannis Leontis in conferences at Washington DC

Third year PGR and vice-president of EUOPS (Exeter University Optics and Photonics Society) Ioannis Leontis discusses his experience of two conferences he was recently invited to:

In September 2019, as vice-president of EUOPS (Exeter University Optics and Photonics Society), I was invited to participate in two OSA (Optical Society of America) conferences in Washington DC. The first one, Leadership Conference 2019 (SLC 2019), was mainly focused on students in optics and included were workshops for improving student skills, transitioning from student to professional and choosing a profession. Moreover, there were very interesting presentations about hot topics in photonics, such as a presentation about the new Infrared Space Telescope of NASA “James Webb”. Concerning the second one, OSA Frontiers in Optics and Laser Science conference 2019 (FiO+LS 2019), it was a very interesting technical conference in optics with multiple parallel sessions about Nanophotonics and Plasmonics, Quantum Technologies, and photonics application in biology including a plenary talk of Nobel Prize Laureate in Physics. In general, both OSA conferences were of great scientific interest and it was a great opportunity for improving my scientific networking and to expand my scientific horizon in optics.

PGR Emanuele Gemo at ePIXfab Silicon Photonics Summer School

From 1st-5th July 2019, third year PGR Emanuele Gemo attended ePIXfab’s silicon photonics summer school at Scuola Superiore Sant’Anna in Pisa, Italy.

PGR Emanuele Gemo

Emanuele gives an insight into his experience:

The experience in Pisa has been definitely valuable.

From the organization perspective, nothing has been left unplanned or uncared for. The venue was the main hall of the University of S.Anna, Pisa, built on the pre-existing 15th-century monastery, which does not add scientific value but is indeed pleasant. The buffet lunches, the organized visit to the historical city center, and the gala dinner have been spotless, laying the foundation for an efficient network building with researchers and academics from all Europe and beyond.

From the content perspective, the initial focus was on the provision of a needed background on the fundamentals of silicon photonics, to allow the audience to make the most out of the information-packed following lectures. These spanned through a wide range of fields, such as fabrication techniques, plasmonics, non-linear phenomena, conventional and quantum device and applications, with the course program being tailored to follow a natural and logical sequence (i.e. from light sources to passive devices, then to active devices, detectors, integration, and eventually innovative approaches). The visit to the CNIT labs has also been extremely interesting and provided a deeper insight into the hands-on research carried out in Pisa.

Most of the courses were very well delivered. I would have preferred a tighter focus on the fundamentals, but I also acknowledge how the panoramics onto the many fields has been of great value, providing a wider and yet precise picture of the concepts of silicon photonics research and applications.

Gooch and Housego Industry Visit

In May this year, our first year PGRs (Cohort 5) visited Gooch and Housego, a global leader in photonics technology in Torquay, for an insight into their company and the wider industry.

G&H are experts across a uniquely broad range of photonic technologies – crystal growth, optical materials processing, acousto-optics and electro-optics, fiber optics, DFB laser modules, precision optics (thin-film coating, birefringent optics, non-linear, planar and aspheric), RF driver electronics in addition to light measurement and calibration solutions.

Through tours and presentations, the PGRs experienced what it was like to work in this modern industry. Building on the ethos of our Beyond a PhD talks, some students spoke further with the staff to see which careers are open to them post-PhD.

We would like to thank G&H for hosting our PGRs to offer such insights in their business.

PGRs Emily Glover and Vicky Kyrimi at Phononics 2019

Second-year PGR Emily Glover and fourth-year PGR Vicky Kyrimi presented at Phononics 2019– a biannual conference series that started in 2011. This year’s conference ran from 3rd to 7th June, and was held in Tucson, Arizona.

Emily presented a poster, entitled ‘Tunable Magnetoelastic Phononic Crystals’, and Vicky presented a talk on  ‘A Metasurface comprising Spiral shaped Local Resonators for Surface Acoustic Waves’. This is what Emily said of her experience:

The conference was my first experience presenting my research internationally, and was a great opportunity to meet and learn from some of the top professors in the Phononics community. The conference included a half-day excursion to visit the local desert museum, to learn more about Tucson and the famous Saguaro cactus that can only be found in Arizona, as well as a session for early career researchers about networking skills.

Vicky said of her experience:

I’m happy to mention that the work I presented at this conference was accepted for publication. I attended the conference banquet which was a great opportunity for networking with people in my field.

See below for photos from the event.

PGR Emily Glover presents poster- ‘Tunable Magnetoelastic Phononic Crystals’
PGR Vicky Kyrimi giving a talk on ‘A Metasurface comprising Spiral shaped Local Resonators for Surface Acoustic Waves’ (Vicky Kyrimi et al 2019 J.Phys. D: Appl. Phys in press)
The conference included a visit to Tucson Museum (pictured)

Joaquin Faneca awarded Optics and Photonics Education Scholarship by SPIE

Third year PGR Joaquin Faneca has been awarded a $3000 grant from SPIE. SPIE, an international society for optics and photonics, was founded in 1955 to advance light-based technologies. Serving more than 264,000 constituents from approximately 166 countries, this not-for-profit society advances emerging technologies through interdisciplinary information exchange, continuing education, publications, patent precedent, and career and professional growth.

In 2019 SPIE awarded $293,000 in education scholarships to 85 outstanding individuals, including Joaquin, for their potential long-range contribution to optics, photonics, or other related fields. Joaquin’s individual project was orientated in programmable photonic integrated circuits based on functional materials such as phase change materials or 2D materials.

He plans to use the money to purchase some books and to go to San Francisco to the Conference Photonic West in February next year, where he will be given the recognition and the diploma of the grant in a student lunch event there. He will submit a proceedings and present a poster there.

Integrated phase-change photonics for memory and computing devices

PGR Emanuele Gemo

This video, narrated by our third year PGR Emanuele Gemo, gives a short description of the integrated phase-change photonic memory, a device allowing to store and retrieve non-volatile information on optical chips.

Emanuele’s research project is focused on the theoretical study of this class of devices, and on the proposal of solutions to improve its energy, speed and memory density performances. This device architecture has the potential to be exploited not only for memory applications, but also for in-memory computing: this aim is pursued by the EU2020 funded Fun-COMP research project, led by Prof. C.David Wright, which is a collaboration between seven academic and industrial partners focused to create a light signal based – biologically inspired neuromorphic platform, of which the phase-change photonic memory is an integral part.

The video has been created for the Fun-COMP website, to explain to an extended audience this key building block, with simple terms and yet drawing upon all the essential elements.

Emanuele co-authored “Tunable Volatility of Ge2Sb2Te5 in Integrated Photonics”, a paper which was recently published in prestigious journal Advanced Functional Materials