Graphene for Supercontinuum Generation

In our most recent paper, my student and I looked at exploiting non-linearity of Graphene in a plasmonic structure for Supercontinuum Generation (SCG).

This work has been exciting to us for many reasons:

  • working on 2D materials. Graphene is a quick start and we are exploring other 2D materials and novel materials as well
  • exploiting plasmonic effects to go beyond sensing applications
  • we found Graphene behaving as a metal without negative permittvity and saw formation of Surface Plasmon Polaritons (SPP) at 300 and 371K. To us this is really exciting and could mean some new Physics lies in wait for exploration.

We generated a multi-octave broadband SC spectrum ranging from 1.5–25 micron at a low input peak power of 1 W.

Typically we expect that at a metal-dielectric interface, SPPs are formed when

k2/k1  = − ε2/ε1 ,

where ε2 and ε1 are the
permittivity of the metal and dielectric respectively. In our case, the permittivity of Graphene is not negative,  however we still observe the formation of SPPs. The values we obtained are summarised below:

graphene permittivity

Calculated conductivity and permittivity of single layer Graphene at 1550 nm for 450 meV and  500 meV – 300 K and 371 K

This performance SC spectrum ranging from 1.5–25 micron was possible due to the high Kerr non-linearity of Graphene and also the tailored waveguide dispersion we obtained.

 

Look out for more on this…

 

 

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A Retreat in Bavaria!

in the Optical style….

I was intrigued when invited to attend and give a talk at the SPP Retreat on Tailored Disorder in Kostenz, Germany last month organised by Prof. Cordt Zollfrank of TU Munich and collaborators, Prof. Helge Otto Fabritius. I am so glad that I accepted this invitation.

So what was so special about the retreat?

SPP 1839 Retreat held at Kloster Kostenz

SPP 1839 Retreat held at Kloster Costing

For starters it was hosted in the beautiful Bavarian Forest foothills in a monastery. So there was lovely scenery, fantastic beer (and wine!)… The mornings had a programme of excellent talks and the afternoons and evenings had a social programme (we went to a glassblowing workshop), a visit to an interactive Physics museum where adults had as much fun (if not more than( kids. Dinner would be followed by beer and wine in our special  hangout room!

The small numbers in the retreat (about 35) created a lovely intimate atmosphere and in this relaxed setting over beer and gorgeous sit down meals it was possible to get to know everyone, form some links, make friends ….  a perfect networking opportunity.

Weissbeer at the monastery- yum!

Weissbeer at the monastery- yum!

The technical aspect was very well served by the format: single track or focus of the retreat:   Tailored Disorder – A science- and engineering-based approach to materials design for advanced photonic applications. There were a handful of invited talks and the rest by PhD students on their projects on the theme. This led to lively interaction and because of the single focus from various aspects, the discussions were always interesting.

My favourite talk was by Prof. Laura Na Liu of Heidelberg University on dynamic/active 3D plasmonic nanostrucutres. Her presentation style was amazing: she explained in simple language and yet managed to convey the highly complex concepts. Perhaps the most elegant concepts she spoke (that appealed to me) were using DNA origami and complementarity of DNA base pairs to shift orientation of bundles/move a bundle along the origami etc.

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Laser inscribed SPP 1839 apple

By attaching gold nano rods to these origami and changing the origami the plasmonic response could be changed/monitored dynamically.

For PhD students and young postdocs I think this sort of meeting is invaluable: they can really interact with the invited speakers and hearing focused talks learn a lot, give their talks without feeling too intimidated. I am now a fan of Optics retreats!

Whenever I have the privilege of attending an event such as this which combines thebest science with the best of other things in life: great company, food and drink, nature…I  always feel blessed that being a scientist has given me more than my wildest imagining.

 

A report from CLEO 2017

Last week I spent some super time at CLEO 2017 in San Jose, California.

The conference as usual was very good and I will write about my favourite talks. There were some new and exciting events that made the conference more special. I gave my own short course on FEM at CLEO now for the 4th time, so that was fun.

So the talks first: I found Dr. Nergis Mavalavala‘s plenary talk on LIGO very cool. It is good to hear about fields where Optics is being used for cutting edge research, while the field is not primarily Optics. Astrophysics has long been an interest for me, so no huge surprises that I liked this talk. I was excited to learn that India is planning a LIGO type detector too!

The session on halide perovskite lasers and particularly the talk by Tze Chien Sum, Nanyang Technological University, Singapore was excellent to understand the current state of the art in these lasers and the challenges facing the field now.

The application and technology review on Supercontinuum Generation (SCG) was another great session: focus on SCG theoretical and experimental development was covered in talks including a historical perspective. It gave a sense of how an entire research field evolved and is still current! My favourites talks in this session were by Alan Willner ( a past president of OSA) on Structured Light using Spatial, OAM and Wavelength Domains for Terabit/sec Communications; and by Adam Devine of  Fianium, who spoke on Supercontinuum  Laser Sources Future Await Wide Applications.

The best technical part however for me was the Bright Idea competition sponsored by Quantel. I was asked to judge the competition with 3 others. We heard 4 talks, and each was amazing. In 15 minutes the competitors took us from the basics in their fields to the research frontier, and what they were going to do, why this was important and the innovation in their approach.
I learned about photo acoustic imaging of the brain, quantum optics (a topic I have always found a bit difficult) and aerodynamics research.  It was an incredibly difficult decision to make amongst the 4 finalists, but eventually the winner was from University of Otago, Harald Schwefel who spoke on Photon Triplets for Quantum Optics and Secure Communication. Next year I think I might submit an entry into the competition as well!

Now to the exciting new events: there was a workshop on unconscious bias, the first I attended. We were shown images and we discussed our reactions to these… this led to realising what are the underlying, unconscious but almost immediate reactions we have, how we categorise or classify.  How we react to people and see someone as warm and relatable or as competent and capable, while someone else as untrustworthy/incompetent. It was a revelation! I would highly recommend trying one of these if you can.

I was stunned to realise how much the colour of a person’s skin meant to me when I judged the person as warm or not. That led me to think if I was then letting this influence my decisions on students, on hiring people, on my volunteer work…

I came away with much to think about from CLEO: both technical and also personal.

St. Petersburg and what I learned there

I last blogged about visiting Leuven for OSA to talk about networking in a workshop on career development for PhD students. I picked up some great career tips there.

The very next day after the Leuven workshop, I flew to St. Petersburg to participate in an Optics Seminar and a Women in Photonics event for IEEE Photonics Society at ITMO University, organised by Anna Voznesenskaya (Dean of Laser and light dept., ITMO University).

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IEEE Women in Photonics Session at ITMO University, St. Petersburg

This was my first visit to Russia (a country that I have long been fascinated with) so I was excited beyond belief.

My expectations were exceeded and my thinking challenged!

For a first the number of women in Photonics (and Science, Engineering etc.) at ITMO (and the Russia Federation) seems to be far larger compared to many other countries. I met women who were Heads of Department, Deans, Vice Deans in the technical departments in the university and tech businesses.

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Working hard: Presentation skills workshop

The morning half of the programme saw a workshop on presentation skills by the foreign languages department, headed by Yulia Ryabukhina. This was a brilliant interactive and fun workshop and we focussed on communicating science to non-experts. Working in small groups we all had to make presentations on photonics!

The afternoon session focused on career paths of 4 women from STEM. We had Prof. Irina Livshits who is a legend in the field of optical design talking about her work and career. We had a younger professional, Natalya Demkovich (Head of dept., Bee Pitron SP Ltd.) talk about her transition from student to young professional and head of a department and some of the challenges on the way. We had an excellent talk

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Conclusion of the workshop

from Natalia Bystriantseva on her experience of working on light design for the built environment and the importance of doing work which agrees with one’s own intellectual philosophy and principles. Her thoughts on how design centred around human beings leads to happier and better used built spaces really resonated with me and it is something I want to learn more about.

Following the talks, we had breakout groups to come up with points on mentoring, networking, volunteering etc. One thing that made sense was that E&D aside, students and young professionals all can benefit from professional development and skills training.

That aside, these ladies rocked!

Honestly, they were the most effortlessly confident, smart and intelligent women I have seen. The idea that they could be discriminated or would be didn’t seem to occur to them and their professional stature seems to reflect that.

So: why is Russia more equitable for women in STEM?

I think that needs more probing and I feel we could definitely learn from our colleagues in Russia. Demographically there are more women than men there- which would help. An outcome of Soviet times as well perhaps? But there has to be more: and I really want to explore it.

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Having a blast at the holography museum with Prof. Irina 

Apart from the workshop I was given such fantastic hospitality and warmth by Anna, Irina etc. I had lovely Georgian food, I was show Irina’s labs and the holography museum where we had tremendous fun! I visited the world famous Hermitage museum and the Church on Spilled Blood, the Russian Museum….

I found every aspect of life here fascinating. I ate caviar on my toast!! I had vodka for breakfast!!! I found St. Petersburg to be huge: buildings were sprawling and compared to London it felt like everything was magnified in size at least 10 times. I had the great pleasure of seeing some of the works of the master, Wasilly Kandinsky – what a treat that was.

Language was a barrier and I wish I had brushed up my Greek let

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Blinis with salmon and red caviar

ters to read signs better and made more effort to learn Russian phrases to communicate more with people. I found people to be a bit shy, but very warm and helpful when I approached them in spite of the language issue. Though after living in London I realised I had gotten so used to the multicultural nature of the city, seeing almost no people of colour in St. Petersburg was a bit weird for me. Not to say it is not multicultural: there are people and the way of life (food etc) from the various republics that form the Russian Federation.

Above left a picture of the Palace Square with the Hermitage (Winter Palace in the background); right: Inside the Hermitage at the private chapel of the Tsars!

All it amounts to is that I need to go back for some thorough research into:

  • How is there better equality for women in science
  • Learn from Irina about optical design
  • Explore St. Petersburg and other cities
  • Get myself a Faberge egg replica and a Palek box that I missed out on this time

 

 

 

 

Chocolate milk in Leuven and other things…

I was lucky enough to be invited to a PhD career development day at KU Leuven as an OSA Travelling Lecturer this last month.

I had a wonderful experience (you may roll your eyes and say: “she says that for all the places she visits!” True but I can’t help it if I have such great hosts in such lovely locations).

First work and then I’ll talk about the chocolate milk…

The OSA student chapter at Leuven, recognising that most PhD students worry about their future prospects put together a really smart programme: 1 hour session by Cathy from Cheeky Scientist on transitionising from academia to industry, I had an hour on networking skills and then a final hour with Wim Van Kerchove

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Lunch with the chapter officers and speakers

(www.crossint.eu) on applying for industry jobs.

 

About 180 students attended the workshop and there were questions for all the speakers. Plenty of students came up to talk to us in the reception that followed as well so there was a chance to get to know some people on a more individual level apart from getting a sense of the concerns of the larger group.

Looking for a job is a serious matter and requires effort and time. Cathy and Wim’s talks were very helpful in explaining how building a profile and network are needed not on the day one starts the great job quest, but well in advance. Cathy’s tips on how to create a good job search strategy, a good linkedin profile were very illuminating.

While Wim gave some really crucial insights into how recruitment folks and headhunters look at job applicants: a view from the other side. He stressed that most jobs are not advertised and therefore networking, apprenticeships etc. are very important in finding a job.

To me a really important thing that both Cathy and Wim stressed on was that it should be about finding a job that suits you, not just any job. Happiness and satisfaction should be present in your job and ensure a good work life balance. Remember that when you are looking and feel desperate!

IMG_0007

Legendary chocolate milk!

My hour on networking skills was spent exploring what networks are, how they are useful, how each person’s networking style should be suited to their personality, and finally how networks can be built, grown and tapped. I emphasise here as I did in Leuven, to have a thriving network, one must give back to it not just take from it, else the network will wither.

 

If you want to know more you will have to invite me to your chapter!

Now to the chocolate milk and chocolates.

On the evening before the workshop I saw a young man drinking chocolate milk at a bar. I was intrigued and at lunch with Valerie and the others, I had some too. I got a glass of milk accompanied by a bowl of chocolate pellets. These melted into the hot milk and gave me the most delicious chocolatey chocolate milk I ever had. Not only that, Valerie Yousef and the others got us lovely Belgian chocolates.

A quick word on Leuven itself: beautiful medieval town with very friendly and

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Incredible architecture at Leuven

helpful locals. I had so much help finding my hotel in spite of the language barrier. I feel so much more welcome in a place when the local populace is welcoming- makes the experience richer. Leuven has a lot of Dutch influence so canals, language, shops… I was reminded strongly of Amsterdam.

 

And so I departed for London feeling rather satiated, ready for my next adventure to St. Petersburg!

Excitement, diversity and soft skills

I’m so excited that I can barely spell correctly in writing this post.

I have the opportunity to visit a very very wonderful place, a city that have always dreamt of going to and a country that I’ve always wanted to visit: St Petersburg.

And the cherry on the cake is visiting Leuven in Belgium just before that.

At. St. Petersburg, the ITMO University is organizing a career development day focused on Women, and this is co-sponsored by the IEEE Photonics Society, Women in Photonics. Events will focus soft skills: communication, presentation, writing, networking as well as career advice.

Leuven has a PhD development day which includes talks on networking and why that is important.

Learning the skills that are not taught in any technical course such as the ones above, are critical to career success and personal development. It helps that professional bodies and universities are now working with staff and students on these. Focusing on specific challenges faced by women/minority groups can additionally enrich our profession by retaining and supporting the best talent.

Not to mention that in the process one may get to go to wonderful places!

Just waiting now for my visa- wish me luck!

Workshops with a difference

Small workshops and conferences are fun!

When the speakers come from fields very different from you own, the fun quotient seems to increase even more.

This was reinforced for me at the recent workshop on Biomimetics held at Imperial College. Getting to hear talks from chemists, biologists, zoologists,  physicists and engineers on talks that had one primary connection: bio-inspiration or bio-mimicry was really interesting.

Animals that prey tend to have slit pupils as opposed to round pupils for animals that don’t prey. Connect that to design of optical systems, computer vision and algorithms!

Or think of how colour originates from arrangement of butterfly wing scales because of wave interference effects rather than pigments. Now use this for colour that doesn’t fade.

It helped that I had the opportunity to invite some speakers I really wanted to hear as a co-oganiser!

Another thing I like about smaller events is the informal nature: fewer people and enough time provides space for meaningful interaction. The atmosphere is intimate and relaxed. Spending a day (or two) with a small group helps foster interaction.

Next time I’ll blog about another smaller workshop that I enjoyed in Delhi.

Cheers till then!

Some more student success

Success is always sweet. The success of one’s students is even sweeter!

I have the pleasure of co-supervising a very capable young man called Souvik Ghosh, who has recently won the best oral presentation award at Photonics 16 conference in the Photonics Modelling/Quantum Optics category.

To win such a prestigious award at an international conference is a big feat.  Certainly I am almost as proud as Souvik is.

You can see the paper that won him the award here: souvik_photonics-2016.

Thermodynamics and Photonics: a match made in California

Some of the best Science is that of sinple, elegant and seemingly outrageous ideas: the sort that relate to the basics of Physics.

At a recent plenary talk at Photon16 by Professor Shanhui Fan this is exactly what we got to see and hear. The idea of solar cells converting illumination (or what Shanhui calls positive illumiunation) into current is not new.

However he went a step further: negative illumination!

When a cell is dark, and if its temperature is higher than the ambient it must give away the excess energy to maintain thermodynamic equilibrium. Presto- current in the opposite direction compared to the daylight!

Ergo a cell that can generate electrical power in the day and the night!

To me this concept is beuatiful because it uses some fundamental and very simple Physics.

This sort of thinking that focuses not on technological aspects or narrow single disciplines alone but rather sees Science/Physics as a whole is what challenges status quo and leads to exciting new discoveries!

 

Visting OSA Student chapters!

As an OSA Ambassador in the centenanial year for OSA I had the privilege of visiting student chapters in India. In this post I want to record my impressions of that visit.

I traversed from north India (New Delhi, the capital city) to the Eastern cost (Hyderabad) and then Kolkatta before retracing my steps. Each of the flights I took within India was fully 2 hours at the least and the size of the country reminded me that visiting several chapters really needs several days in addition to the actual visits. Not to mention the heat which was beginning to really turn on as the Indian summer got underway (think temperatures of 46 degrees Celsius in Delhi).IMG_1026

The heat, the long flights and hectic schedules were however almost forgotten when interacting with the chapters, being overwhelmed by their generous hospitality and impressed by their work. The passion and enthusiasm that I saw in the students was so infectious and energizing that I feel grateful I could interact with these wonderful students.

In Delhi I met the IIT Delhi student chapter and gave a talk to an audience of 30. There were plenty of questions about the Finite Element method and its implementation, how to deal with field continuity across boundaries and taking care of reflections. On the chapter side the discussion revolved around the best way to engage more of the members in organizing activities and participation.

The IIT Delhi student chapter told me about their activities: seminar series, open days where schools student would visit and be shown demonstrations, quiz competitions and a very successful IONS conference as well. It all sounded wonderful and I was very pleased for a personal reason: I had started this chapter way back in 2003 as a PhD student. So to me the sustained success of the chapter is very satisfying.

This was something we talked about too: when chapter leaders complete their degrees and move on, how to hand over the leadership so there is a continuity in the activities. Good communication was seen to be key! As well as learning from the success stories of other chapters globally to get ideas for events . The chapter was vibrant, active and engaged.

Having thoroughly enjoyed the visit to my alma mater I then hopped to Hyderabad. The Vidya Jyothi Institute of Technology chapter was my host in this historic city which serves the best biryani ever.

I cannot describe adequately how deep an impression the chapter has left on me. Sitting in the outskirts of Hyderabad, the chapter is hosted in a largely undergraduate institution, with some very keen and intelligent students. The chapter was holding seminars and doing some invaluable outreach work going to poor schools and even orphanages, bringing Optics and Science to underprivileged children who would not otherwise ever have access to things like the OSA discovery kit. They are inspiring children who have little opportunity and really brining to life the mission and vision of OSA in a way that deserves recognition and support. I only wish more chapters in India, Asia and Africa would go to schools in poorer neighbourhoods.

Our discussions were ofcourse not confined only to their activities but also the interests of the chapter members! Again the enthusiasm for Science and the love for different aspects of science was like a current running through the room.  Beyond Optics, I was trying to answer questions about black holes and the Large Hadron Collider!

Carrying with me the fantastic experience of Delhi and Hyderabad it was fitting that I went to Kolkatta, the city where Optics was born in India. It is also the city where some of the best sweets are made!

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In a series of joint events hosted by University of Calcutta, IIT Kharagpur, Institute of engineering and Management, that lasted the entire day i met more than a 100 students!

The morning lecture was the University Of Calcutta after which we shared a bus, several cars to go to the Institute of Engineering and Management for lunch and the second lecture, followed by a interaction only session at the University of Engineering and Management.

 

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To say I was overwhelmed by the brilliance of the students, their ideas, their questions and their interest, would be an understatement. If someone could bottle the energy in the room, they could power a city for a week!

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From solar cell optimization, to whether optical computers would be viable to grapheme waveguides the technical discussion was wideranging. The chapters and their activities again were very diverse and there was a real interest from the students in getting new ideas for events.

To each of the chapters, the members, the organisers and faculty advisors I cannot say “thank you” enough times. I loved this experience and I only wish I could have spent more time at each place.

Some common themes that I picked up from all the chapters were:

  • looking for new ideas for events/engaging members. In my view learning from the success and best practice of chapters the world over is a great way to do this. As is engaging with other local chapters
  • paying the OSA memberhip fees via credit cards was not easy for some chapters, and I have since learned that local bodies such as Optical Society of India (OSI) can collect the OSA dues if members also join OSI.

When I set out from London, I wondered how the trip would pan out. Now that I am back I know this: I want to go again!!