The Droplet Laser

A laser is a fairly simple thing at heart. You need a couple of mirrors a chunk of material with the appropriate atomic characteristics and an energy source to get it all started. When teaching lasers to my undergraduates I often flippantly remark that “if you hit it hard enough, pretty much anything will lase,” [1] meaning that if you can get enough pump energy in the material requirement of the laser material don’t matter too much. While this isn’t quite true, it didn’t stop some of the original laser pioneers trying to make an ‘edible‘ laser out of jelly (or Jello-o for American viewers). In this they didn’t quite succeed, but they were able to get gelatin doped with fluorescein dye to lase and this could then be eaten, as the dye “was almost non-toxic”.

In some recent work (Optics Letters 38 1669 (2013), behind a paywall, sorry) work between my group and Alper Kiraz‘s at Koc University in Istanbul we have had a shot at making both slightly unusual and potentially edible substances lase, namely a microscopic droplet of water. This too is based on using the water droplet as a host medium for the lasing material (Rhodamine-B – which is likely a carcinogen, so you might not want to digest it) and a bit of glycerol for stability. Our work is based on using optical tweezers to trap the droplet in mid-air using an infra-red laser and then we illuminate it with a second pulsed, high energy, (green) laser. The droplets (water aerosols) are around 10 microns, so 10 millionths of a meter, in diameter. Pretty small! The nice thing about water droplets is that they tend to form very nice spheres, and this gives us a very simple way to form an optical cavity. Normally we would use mirrors to form the cavity, for example in a Helium-Neon laser, but here like that gets into the droplet can undergo total internal reflection and can get trapped inside. This enables a large optical field to build up and gets us above the energy threshold needed to see any laser action. This effect is called a whispering gallery resonance, and is the same effect as seen (or heard) in cathedral domes, like the ‘Whispering Gallery‘ in St. Paul’s Cathedral in London. Here, if you stand on one side of the gallery and whisper into the wall, the sound is able to creep around so that your friend on the opposite side of the dome can hear you clearly.

In the figure below you can see the output from the laser – these are in the form of cavity ‘modes’, which are the little spikes in the diagrams. The top two figures show the outputs below the laser threshold, while the third shows a higher pump energy and laser action. The inset shows the trapped laser droplet.

The figure shows the outputs of the cavity formed by the water droplet – the peaks indicate the ‘modes’ of the cavity, where a whole number of wavelengths fit round the droplet circumference. The top two figures show the output below the laser threshold, while the lower figure shows ‘laser modes’.

Our laser is not the first to make use of water droplets as the lasing host – there has been work on bigger droplets trapped using ultrasound and on surfaces but ours is the first to make use of optical tweezers to hold the laser. This should enable us to look at very small droplets, explore tuning of the laser through controlled heating, and it gives us significant control over the movement and placement of the droplets.

So what could you do with a droplet laser? Well there is quite a lot of work on using whispering gallery modes in solid spheres as sensors, and one could imagine extending this to liquid spheres. As we can easily place things within the droplets we could also use them as more general probes – the idea would be that perturbation of the laser in some way would allow us to probe the contents of the droplet. It might also allow us to sensitively probe the shape and dynamics of the droplet, which is very hard to do otherwise due to the very strong surface tension. We are only just starting to think about the possibilities.

On a personal note, this is an experiment that I thought up many years ago, and which we started to do when I worked in St. Andrews. We got some preliminary results showing droplet fluorescence but then the PhD student working on it had to write up and finish and we never quite got back to it. So it’s very satisfying to have finally done it, with a little help from my friends, and also that no-one else has done it in the meantime!

[1] Turns out this was a phrase used by Art Schawlow (see here, well worth a read), which means either great minds think alike, or I pinched it from him. I’ll stick with the former.

Physics and Life Sciences/Biophotonics Initiative

It seems appropriate that as EPSRC starts up its ‘Understanding the Physics of Life‘ network (also discussed by Athene Donald on Occam’s Razor) that we in Dundee are also starting up a new collaborative project between Life Sciences and Physics. The College of Life Sciences in Dundee is a world leading centre of research in a range of biological topics and in many ways is the dominant research centre in Dundee. Physics plays a rather more modest role in the life of the University, but in recent years we have been gathering significant momentum, and a range of pilot projects between physics and life sciences have now started to deliver results.

We have had some grant success recently as well, playing a part in an MRC Optical Microscopy proposal funded through Life Sciences and we have also just been awarded an Innovative Doctoral Programme ITN based at Dundee to help train a number of early career researchers in fully interdisciplinary projects. This should become active next year and lead to a significant boost in the number of projects we run between our two departments.

To try and cement these relationships further we have also established a trial project to host a space within Life Sciences that can be used by physicists to develop new techniques and tools side by side with the biologists. Our initial goals are to look at the development of new light sheet microscopy devices as well as test out in-house developed lasers for suitability as multiphoton imaging sources. We have a one year postdoctoral position advertised at present to work on these topics and also try and act as an interface point for staff looking to try out new pilot projects – including some of my own on intracellular optical manipulation. So if you are looking for a new interdisciplinary biophotonics role or know someone who is, please apply at the link above (you can contact me for more info).

We are also expanding our staff in biophysics – we have just welcomed Dr Ulrich Zachariae to the Division, who will work on computational biophysics problems, and hopefully will form close ties to the Drug Discovery Unit here, and will be welcoming a further biophotonics staff member next month. We have also been very lucky in our recruitment process for ‘Dundee Fellows’ and we’ll be adding another computational biophysicist later in the year, and hopefully to other biophysics areas depending on if offers are accepted.

Our goal in all this is to try and tackle new and bigger scientific problems by working together and we have exciting plans to try and make this area grow further at Dundee. So I am hopeful that we can make a big mark in the ever expanding research world at the physics and life sciences interface.

Printing the Moon

A few weeks ago I had the good fortune to attend a conference (in a loose sense) that was a million miles away from my normal academic meetings – South by Southwest (SxSW). This is a huge multifacted event, with over 100,000 attendees covering interactive. film, music, education and every other form of tech meets new media that you can think of.

I was there because I know a man who knows a woman who happens to work at NASA. My brilliant colleague Jon Rogers, a product designer in our Art School, works on a range of projects exploring how to make data ‘physical’. NASA, who have a desire to make their open data more used by interested parties have been developing a ‘Space Apps‘ challenge to try and focus people, in a crowdsourced manner, around certain topic areas. As one might imagine these challenges and their solutions are fairly software based, but NASA also wanted something a bit more hardware oreintated – hence ‘Making Space Apps Physical’. Jon wanted to try and broaded this idea out and so asked a couple of other designers, Sandra Wilson and Jayne Wallace and myself to get involved, adding to the team that already included Ali Llewellyn from NASA. This led to us submitting a panel proposal for SxSW this year, which was (surprisingly) accepted, based around this idea of making space a bit more immediate, a bit easier to interact with.

And so the “Print the Moon” project was born – my little contribution. The idea arose from an Advanced Higher (final year Scottish high school pupil) who wanted to try and do an experiment on Astronomy. We lent her a telescope and then suggested that she could try and do some measurement on craters on the moon looking at their shadows. Even with a decent telescope like ours this is not so easy, so I thought about how you might be able to do the same thing in the lab. With the ability to 3D print objects it seemed like it should be possible to print out a crater and then just use a torch or other light source to do the experiment, and this was the challenge I sent to a group of our keen undergraduates.

Essentially the problem was to find the right data and then take that and turn it into something readable by the 3D printer (or rapid prototyper). The data was provided by NASA’s Lunar Reconnaisence Orbiter with it’s Lunar Orbiter Laser Altimeter instrument providing 3D surface topography. The students then ported this into Matlab to plot the surface, sent it over to Meshlab for cleaning up and then sent it to Solidworks to output it to the printer. As an educational tool this has proved very valuable, as the students had never really used any of these before (expect Matlab). A copy of the Korolev Crater is shown below, from the dark side of the moon. You can then do a bit of trigonometry to try and get the crater dimensions based on shadow data. So all in all it works quite well.

3D version of Korolev on the dark side of the Moon. Spot the deliberate mistake.

And we took this over to South by Southwest and talked about it on the panel, and I even got to meet an astronaut. I’m very proud of my students getting stuck into something like this – a project that has no academic bearing on their courses – done just as it’s a bit of fun and it helps you to learn some new skills. I also think we could maybe push this towards a publication in something like the American Journal of Physics and will hopefully have some Nuffield Bursary students working on this over the summer to try and gather the necessary data.

Our students were also on hand at an event organised by New Media Scotland, the LateLab, as part of the Edinburgh Science Festival to talk about their work. And there is still more to come, with other events still to make use of out little chunk of the moon. Oh, and if you want to get involved, there is a Space Apps Challenge: “Dark Side of the Moon“.

Dundee Fellows: Where are the applications?

My department is part of the College of Arts, Science and Engineering at the University of Dundee and the College has recently been running a new type (for Dundee) of recruitment scheme, called the “Dundee Fellows“. This is a cohort recruitment program, offering all sorts of mentoring, media training and cross college networking opportunities, as well as being a permanent academic post. It’s an excellent opportunity for good postdocs to take the next step on an academic career path and establish their own group. The application deadline passed yesterday and we have hundreds of applications in total. I’m not sure of the number in physics, but we have a healthy proportion of that, and it looks like we have a large number of excellent candidates. So I don’t have anything to grumble about – this scheme will help us add more talented researchers to our growing department. But…while the number of applications applications sounds like a lot, this covers physics, biomedical engineering, maths, civil engineering, computing and the myriad of things that artists and designers do.

There are, I believe, around 46 physics departments in the UK, and I would suspect the average number of 30 staff in each would not be unreasonable. I would also suspect that the staff:postdoc ratio must be as a bare minimum something like 1:1? So that would give us around 1500 postdocs in UK physics. Now as we are not really recruiting in a range of areas (nuclear, particle, astro etc) we can whittle this number down somewhat, say by 1/2, which would lead 750 still in the general areas of photonics, materials and biological physics and other stuff we would be interested in. Assuming a postdoc is 3 years on average, 1/3 of these will be in their final year, with at least two years experience, so 250. Let’s then assume half of these actively wish to leave academia, and that half of those who wish to stay couldn’t come to Dundee for personal reasons. This leaves around 60. We do not have 60 applications from postdocs based in the UK. My assumptions may be way off, but that number doesn’t sound too bad.

As you hear all the time about the poor state of career progression in academia (which is true), why is it that I do not have a much bigger pool of people applying for positions here? I am genuinely curious. Possibilities are (i) that we did not advertise well/clearly enough, (ii) we are not an attractive destination for aspiring academics in physics, (iii) postdocs aren’t really sure how to apply for such positions, or where to find out about them, (iv) postdocs overestimate the number of permanent jobs that come onto the market, (v) postdocs quite like being postdocs. I’m sure there are others. There are a fixed number of jobs, and a fixed number of locations, with usually one University per location – so the options and choices are not great. If you are not mobile in this market you will be very limited in what you can do. My advice is not to apply for every job that comes out, but if in doubt take a bit of a punt, you might end up in somewhere like Dundee and be very surprised at what you find (in a good way).

I’d be particularly interested to hear from people who are looking for a permanent post in physics, saw the advert and decided not to apply. Any other thoughts welcome too, of course.

 

Science Grrl and the Community

Last year I noted that as the new head of physics at Dundee I should do more to promote women in STEM fields. This came after a bit of homework that my daughter received highlighted the stereotypes that schoolkids get all too readily when thinking and discussing scientific issues. As it turns out part of my role is to try and help guide the Physics Division towards accreditation in programmes such as Athena Swan and the Institute of Physics’ Project Juno. These have certainly got me thinking much more about the diversity issues that both Higher Education organisations and the wider community face.

The first thing I am pleased to be able to announce that we are doing is a small bit of community engagement. I am very much of the opinion that Universities have an important role to play in their local communities, and that we can in our own way help to transform the environment around us by opening up new opportunities, introducing new ideas and providing the best education we can to our local young people. I wanted to try and let schools know that there is an issue with the way in which girls at school interact with and perceive science, and that this ultimately impacts on the number of girls who end up on STEM courses and in STEM jobs, and that this, in my opinion is a huge waste of talent. I think this dovetails quite nicely with the goals of the Science Grrl group and the idea that “Science is for everyone”. To try and highlight this idea we have sent out a Science Grrl calendar to all the schools in Dundee. This is just a small action, but I hope, from a personal point of view, that it is just the start of wider engagement that we can make with these issues, and just the start of a processes of making more of an impact in and around Dundee.

The Science Grrl 2013 Calendar

if you happen to be a Dundee based teacher, I’d be interested in hearing your views on these ideas, and if we can help in anyway, just get in touch.

Many thanks also to Heather, Louise and everyone else at Science Grrl for sorting out all the calendars!

The Faculty Search

Currently my department is hiring. We have at least one position for a lecturer (equivalent to a US Assistant Professor) and one for a full Professor. You have to be a big cheese in the UK to get to call yourself “Professor”. This is the first time I have been on a search and selection committee for a faculty member and it’s a interesting and tough process. I thought I’d just share some thoughts on how we have gone about this, for prospective applicants into UK Universities. In our case we spread our net fairly wide. The position is in a generic area called “Physics Aligned to the Life Sciences” which is one of the core themes of the Scottish Universities Physics Alliance or SUPA, which Dundee is part of. Within this theme pretty much anything bio-related to physics is covered. We decided not to hone down on a more specific area and try and recruit the best person we could that aligned with one or more of our research themes. This led to us getting a large number of very high quality applications. It was a tough choice – so how did we decide?

Fit to specification: The first bit of advice I have is to make sure that you write your cover letter, CV and research statement so as to clearly state how you fit the position. While our call wasn’t specific as to topic area it would seem clear that applicants should be able to state how their work aligned itself to the life sciences. Writing that you were really interested in biology wasn’t going to cut it, and for some really strong physical sciences applicants this is where they fell down. We wanted to see at least some evidence of how applicant’s work either had been applied to biophysics research or evidence that they had thought out how their work might be applied in Dundee (and not just generically).

Experience: Clearly what you have done to date matters a lot – it shows the kind of trajectory that you are on, how much of an original thinker you are and what you might be capable of. So the areas you have worked on, your general productivity and the papers you have produced make a big difference, but the reality is that this is only part of the package – you might have been unlucky in where you have worked, or the projects you had been assigned may just not have gone to plan. We recognise this, and so if your papers and background are a little lacking for whatever reason then your research statement becomes really important. We did consider how applicants would look as far as the upcoming Research Excellence Framework (REF) review is concerned. This is perhaps a little unfortunate, but the reality is this is a strong consideration.

Metrics: So does your h-index matter? Does your publication count make a difference? Number of citations? Where you publish? In modern academia these things to have a huge significance attached, and probably much more than they should. I don’t think we compared anybody’s h-index – bearing in mind these are entry positions, and the wide variety of postdoc positions that people have means you can’t compare such things, or even the number of publications in any strong meaningful way. One of my colleagues had a clear idea that as a postdoc you should be producing one decent paper per year, and this was used as a rough kind of bar, but not a digital pass/fail barrier. I think we did consider numbers of citations as part of the indication of the value of the papers published, but this, again, was to help us form a view of how valued work was, and clearly for a paper published the week before application there will be no citation data. Papers that were in peer review or ‘to be submitted’ were of little value in helping any decision to be reached, but those under review gave some small indication of overall productivity, if not quality. Finally I think the panel probably paid more attention to where papers were published over other metrics, but again we did very much try and look at the whole picture – I’m fairly pleased that we put more emphasis on the research ideas and potential to deliver than pure numbers.

Potential: So you want to come and work with us, but what are you going to be doing? Your research statement  needs to outline a coherent program of work, and has to address something interesting in an innovative way. Incremental changes are not so persuasive. Clearly you also have to be realistic, and this is where the challenge lies – outline something of grand enough ambition but in such a way that we can believe you will be able to deliver. For our position we also wanted applicants to try and identify how their proposed work would fit in Dundee – one of the criteria was to bridge gaps between physics and life sciences and medicine – so we wanted them to really think about how they would fit in and who they might work with. We wanted them to show that they really wanted to be at Dundee. In my mind this is almost the most important section – it gives you the opportunity to show your talent regardless of what you have achieved.

Interview: You make a good impression on paper but you have to be to talk the talk as well. We decided on an American style full day visit for each interviewee. So the candidates got to speak to a range of people across the University. Again we asked applicants to think about who they might like to see, with a view to pushing them to think about why they wanted to be here and what they might do when they arrived. They were also asked to give a talk. All this information was fed back to the interview panel to try and give us a rounder picture of each applicant. Our interview panel had physicists, biologists and others on it, and it meant that we could push candidates to really get down to the detail, the potential and the importance of what they were proposing to do. The main thing that came out from this was that candidates who had written strong research statements were able to give much clearer answers as to what they would be doing should they come to work in Dundee.

The bottom line was we want new colleagues with great potential, people who will try and push at big challenges, either by attacking them directly or by developing new and innovative techniques that can be applied in a more general sense. We are looking for people who would be good colleagues, who would ‘fit in’ and who were able to interact with undergraduates and help grow our teaching programmes. After this really interesting process I think that is what we will get.

And so it begins: Scientific Sterotypes

My daughter’s homework this week wasn’t too unusual – a little bit of maths, a reading book and some writing and comprehension. Her writing exercise was linked to her current project work, which is related to science this term. For the past few weeks she has been looking at magnets and some of their properties (in a simple sense, as she is only in Primary 3). What particularly caught my eye was the picture used to illustrate her assignment, which was to write a few sentences using appropriate adjectives and descriptions, of a hugely stereotypical ‘scientist’ in the old man Einstein mold with a set of test tubes.

In a generic sense this is fine, take an image and write some descriptive words and phrases about it and then put these into more context within some sentences. I can’t really argue with that. What I do take issue with is the tired old cliche of the stereotypical scientist. This is the type of thing that seeps into kids brains, and while it maybe not put them off, it does add to their perception of science as being uncool. At the moment I think the kids love science, they like doing experiments, and finding things out – but give them ten years of these stereotypes and it begins to become a problem. This is where it starts.

Additionally, I like to imagine my daughters are capable of anything, and that being much better scientists that I will ever amount to is well within their grasp – but again years of reinforcement of scientists being slightly disheveled old men will ultimately take its toll (I should point out that I am a dishevelled male scientist, so maybe I’m on shaky ground here). I made this point to my duaghter, and as she is a good pupil, she stuck up for her teacher. Apparently the character is from a computer game they use at school. But in a way I hope the teachers can do better. Then, of course, I realised that the teachers at primary school probably don’t know better – these are the stereotypes that they have grown up with. Teachers don’t have my same concern about the lack of female students in, for example, physics and engineering subjects and jobs because they are, through no fault of their own, unaware this is an issue. Science communication needs to extend much further than just the pupils.

I have watched with interest the development of, for example, projects like Sciencegrrl, and Geek Girl Scotland, with a dispassionate interest – I sympathise their cause and see the need for such iniatives, but I didn’t quite see how it fits in with me. Now I can – so I’ll get a Sciencegrrl calendar and pass it on to my local school, and as, for the moment, the Head of Physics at Dundee University, I will try to look at ways to improve our attractiveness to female applicants, and explore ways in which we might help out more in the community to try and stop such stereotypes staying as wide spread as they are.

Update: I have now ordered a Science Grrl calendar, so will donate it to my kids’ school when it arrives. You should get one too.