Impact of pump wavelength on terahertz emission of a cavity-enhanced spintronic trilayer


FIG. 1.
Schematic of a spintronic trilayer with added dielectric cavity, grown on 0.5 mm of sapphire (Al2O3). The near-infrared pump pulse, incident through the substrate, is partially absorbed in the metallic layers, launching a spin current from the ferromagnetic (FM) layer into the nonmagnetic (NM) layers. The inverse spin Hall effect converts this ultrashort out-of-plane spin current into an in-plane charge current resulting in the emission of THz radiation into the optical far-field. A weak in-plane magnetic field (B) determines the magnetization direction and the linear polarization of the emitted THz field.

Congratulations to third year CDT PGR Rosamund Herapath for her recent publication of Impact of pump wavelength on terahertz emission of a cavity-enhanced spintronic trilayer in Applied Physics Letters.

In this paper, the authors enhance the THz generation of a novel, thin-film THz emitter by adding a set of dielectric overlayers. In doing so, they not only increase the intensity of the THz emitter by a factor of 4 in intensity, but also reduces the amount of IR pump beam transmitted (This will enable the emitter to be used within delicate systems).

She presented her findings in December 2018 at University of Warwick.

Charlie-Ray Mann: UK representative at the 69th Lindau Nobel Laureate Meeting

Charlie-Ray Mann has been officially accepted as a UK representative for the 69th Lindau Nobel Laureate Meeting (#LINO19) that will take place 30 June–5 July 2019.

LINO19 will be dedicated to physics. Until now, 41 Nobel Laureates have confirmed their participation. They will meet 580 young scientists from 88 countries for an inspiring dialogue.

Charlie is a 4th year theoretical physics PhD student in the CDT in Metamaterials. He graduated from the University of Exeter in 2015 with a 1st class degree in Physics, during which he was awarded two scholarships for academic excellence and received the Bertie Black Prize for the most outstanding academic performance in the College of Engineering, Mathematics and Physical Sciences.

His application was strongly supported by the Royal Society and by a combined effort of his supervisors (Dr. Eros Mariani & Prof. Bill Barnes), some of their colleagues in Physics, as well as our Head of Discipline, Prof Tim Harries, and the University’s senior management.

The participation to the Lindau meeting is a highly selective process as only one student can be nominated every year by an academic institution and only very few worldwide are finally selected by the Lindau committee.

We would like to congratulate Charlie for yet another prestigious achievement and are keen to learn about his experiences at this unique opportunity.

XM2 @ the KTN “Showcasing Emerging Technologies 2019 – Metamaterials” event

What we presented at KTN’s ‘Showcasing Emerging Technologies 2019 – Metamaterials’ event in Birmingham on 19 March 2019:

  • a tag prototype that could revolutionise metallic packaging security (Dr Paul Keatley, Emily Glover);
  • a numerical tool which can be used to design a new class of radio and microwave frequency-based components for communications devices (Dr Conor McKeever);
  • a demonstrator to showcase the modulation of a terahertz beam using optical light, which allows us to quickly take images at terahertz frequencies (Dr Lauren Barr);
  • research currently being undertaken to significantly reduce the profile depth of conformal antennas (Dr Cameron Gallagher).

Our CDT Director, Prof Alastair Hibbins, gave the event’s opening talk on history and relevance of Metamaterials science to the ~130 attendees from UK universities and industrial/governmental institutions.

UoE reseach fellow Dr Paul Keatley opened the demonstrator sessions with an exciting 5 minute pitch on the security tag prototype developed at the University of Exeter: A solution for future protection of high value merchandise in metallic packaging.

Picture (from left to right): Prof Ian Youngs (Dstl); Dr Paul Keatley (University of Exeter, UoE); Shane Davies (CDT in Metamaterials (XM2) PGR/Deregallera); Emily Glover (XM2 PGR, UoE); Dr Lauren Barr (TEAM-A QinetiQ/UoE, XM2 graduate); Dr Cameron Gallagher (PepsiCo/UoE, XM2 graduate); Josh Hamilton (QinetiQ/UoE, XM2 graduate to be [viva on 1 April!]); Dr Thomas Graham (University of Sussex, XM2 graduate); Prof Alastair Hibbins (XM2 Director, University of Exeter).

Pablo Martinez Pancorbo wins first prize in ChemBio category of RSC Twitter Poster Competition

Third year PGR
 Pablo Martinez Pancorbo
has won first prize in the ChemBio category of Royal Society of Chemistry‘s Twitter Poster Competition. Pablo’s poster was on Smart nanoparticle design for finding and killing early-stage single cancer cells.

The #RSCPoster Twitter Conference is an online event held entirely over Twitter to bring members of the scientific research community together to share their research, network and engage in scientific debate. The 2019 edition of #RSCPoster was the biggest yet, taking place for 24 hours starting at 09:00 AM GMT, 5 March 2019. In its fifth year, #RSCPoster boasted subject categories spanning the chemical sciences and related fields.

Reaching throughout the twitter chemical sciences community and beyond, #RSCPoster 2019 involved:
• Over 500 registered poster delegates
• 3186 Contributors
• 9759 Tweets
• Audience of over 2 million
• 14 million total impressions

To find out more about Pablo’s research, check out his student profile or his research blog.  Pablo’s winning poster is below:

Pablo’s winning poster

Careers event: 18 April 2019

On 18 April 2019 we will see the second edition of our STEM PhD student/postdoc-focussed careers event.

A range of organisations (e.g. Babwe Barton Enterprise, BAE Systems, Granted Consultancy, IBM, NPL, Oxford Instruments, WaveOptics) will introduce themselves in 15 minute talks as potential employers, outlining their current research challenges and what they are looking for in new recruits at postdoc level.

During an extended lunch networking session participants will have further opportunity to engage in more detailed conversation with the industry representatives.

In addition, the Institute of Physics will outline how they can support early career researchers in Physics in their career development.

All STEM PGRs and postdocs interested in a career in industry are welcome to attend. The event is free of charge, and registration will open in early April.



Upcoming events co-sponsored by XM2: “Materials for Clean Energy” and “Light in Complex Materials”

On 8 – 10 April two events will take place in areas related to the EPSRC CDT in Metamaterials:

The Materials for Clean Energy Conference [MCEC2019] (National Physics Laboratory, London) and the Light in Complex Materials Workshop [LCM] (Streatham Court, Exeter)

LCM will bring together the communities of scattering media, fibre optics and metamaterials together, to share visions and methods with each other, but particularly with the younger generation of students and early career researchers. Understanding and controlling the propagation of light through complex scattering materials promises a host of new technologies, advancing fields such as imaging, optical communication, optical computing and more.

MCEC2019 will focus on the latest developments in the fields of energy harvesting and energy storage, bringing together academics and industry leaders. It is organised by the EPSRC Centre for Doctoral Training in Metamaterials, with support from the National Physical Laboratory and the EPSRC CDT in Advanced Materials and Characterisation. The conference will be held along with the annual Energy Harvesting Network meeting, a self-sufficient network of UK academic and industrial researchers and end-users of energy harvesting technology.

New Publication: Diffraction by a truncated planar array of dipoles: A Wiener–Hopf approach

Having recently passed his viva and recently joined University of Pennsylvania in a posdoctoral role, PGR Miguel Camacho Aguilar, who graduates this summer, has just published a paper on Diffraction by a truncated planar array of dipoles: A Wiener–Hopf approach in the Special Issue on Canonical Scattering of the journal Wave Motion.


We present a rigorous solution to the problem of scattering of a semi-infinite planar array of dipoles, i.e., infinite in one direction and semi-infinite in the other direction, thus presenting an edge truncation, when illuminated by a plane wave. Such an arrangement represents the canonical problem to investigate the diffraction occurring at the edge-truncation of a planar array. By applying the Wiener–Hopf technique to the Z-transformed system of equations derived from the electric field integral equation, we provide rigorous close form expressions for the dipoles’ currents. We find that such currents are represented as the superposition of the infinite array solution plus a perturbation, which comprises both edge diffraction and bound surface waves excited by the edge truncation. Furthermore, we provide an analytical approximation for the double-infinite sum involved in the calculation which drastically reduces the computational effort of this approach and also provides physically-meaningful asymptotics for the diffracted currents.

Keep up to date with Miguel’s latest research at Miguel’s thesis title was “Microwave response of finite periodic metal structures”.


New Publication: Origins of All-Optical Generation of Plasmons in Graphene

Congratulations to fourth year CDT PGR Craig Tollerton who has recently published an article on Origins of All-Optical Generation of Plasmons in Graphene in Scientific Reports journal. Abstract below.


Graphene, despite its centrosymmetric structure, is predicted to have a substantial second order nonlinearity, arising from non-local effects. However, there is disagreement between several published theories and experimental data. Here we derive an expression for the second order conductivity of graphene in the non-local regime using perturbation theory, concentrating on the difference frequency mixing process, and compare our results with those already published.

Figure 1- Illustration of electromagnetic fields ( E → E→ ) (applicable to pump, probe, and DFG) propagating in the x-z plane. All the fields are p-polarized and the directions of propagation and polarizations are indicated by the red and black arrows respectively. The angles of incidence and transmission are defined in the figure as θ and ϕ.

We find a second-order conductivity (σ(2) ≈ 10−17 AmV−2) that is approximately three orders of magnitude less than that estimated from recent experimental results. This indicates that nonlinear optical coupling to plasmons in graphene cannot be described perturbatively through the electronic nonlinearity, as previously thought. We also show that this discrepancy cannot be attributed to the bulk optical nonlinearity of the substrate. As a possible alternative, we present a simple theoretical model of how a non-linearity can arise from photothermal effects, which generates a field at least two orders of magnitude larger than that found from perturbation theory.

For information on Craig’s previous publications, please check out his Google Scholar page.

Training and other events: March 2019 to July 2019

Please find below a table of all upcoming XM² training and other events from February 2019 until July 2019 as far as planning currently allows and subject to change. Please note that some locations and events have been updated since the previous month’s table.

PGRs, please highlight any XM²-training related absence times to your supervisors. In regards to annual leave or other absence time planning: All confirmed events have been sent to the PGRs via a calendar invitation, but please ensure to check the CDT in Metamaterials Outlook calendar and to liaise with your supervisors and the CDT in Metamaterials office () for approval BEFORE you make any bookings, as there might be a few more events coming up that are yet to be confirmed.

Supervisors, please be mindful of the XM² events when setting expectations on research deliverables with the PGRs.

06.03.19 CDT Groups All PGRs 14:30-15:30 Peter Chalk 2.1, 2.4, 2.5, 2.6
11.03.19 Beyond a PhD: Heather Lewtas All PGRs 12:30-13:30 Newman Purple
13.03.19 CDT Colloquium: Dr Anton Souslov All PGRs 13:30-14:30 Newman Purple
18.03.19 Presentation Skills 1st years 10:00-12:00 Physics 124
27.03.19 CDT Groups All PGRs 14:30-15:30 Peter Chalk 2.2, 2.3, 2.5, 2.6
17.04.19 CDT Colloquium: Femius Koenderink (title TBC) All PGRs 14:30-15:30 Harrison 004
18.04.19 Careers Event All PGRs 09:00-17:00 Reed Hall
01.05.19 CDT Groups All PGRs 14:30-15:30 Amory A239C, Queens MR1, Queens D, Harrison 171
10.05.19 CDT Colloquium: Steve
Barnett (title TBC)
All PGRs 12:30-13:30 Newman Blue
13.05.19 IP and Business Awareness 3rd years 12:30-13:30 Harrison 209
21.05.19-22.05.19 Project Management Training 1st years 09:00-16:30 Physics SCR
14.06.19 CDT Colloquium: Joaquin Rossier (title TBC) All PGRs 12:30-13:30 Streatham Court D
25.06.19 NPL Visit 4th years 12:30-13:30 Streatham Court D
28.06.19 Beyond a Phd: Irina Khromova and Sathya Sreetharaman All PGRs 12:30-13:30 Queens LT1
05.07.19 CDT Colloquium: Vihar Georgiev (Title TBC) All PGRs 12:30-13:30 Queens LT1


New SAG chair

As our 2015 cohort of researchers prepare to finish their PhD studies (in fact, two have already successfully completed progressed to postdoc careers in academia (Miguel Camacho Aguilar, University of Pennsylvania/US ) and industry (Joshua Hamilton, QinetiQ/UK)), we see changes to our Student Advisory Group (SAG):

Ben Hogan (4th year) is stepping down as chair to focus on finalising his thesis, and Julia De Pineda Gutiérrez (3rd year) is taking on the responsibilities to coordinate PGRs input into the management of the centre .

I would like to thank Ben for taking on the responsibilities of representing his cohort and leading SAG. He has been very engaged, active, and professional in his role, and a pleasure to work with. I have full confidence that he will apply himself successfully in future leadership roles.

Looking forward, I am pleased to see that Julia is keen to embrace the role as SAG chair.

She is supported by the cohort representatives