Tim Stephens



I have a degree and PhD in Physics.


Work History:

Heriot-Watt University, Photonic Solutions, Oxford Lasers



Current Job:

Product Development Scientist

Me and my work

I use light to measure what’s in things, so people can make richer butter or tastier chocolate.

I work for a start-up company that is developing some space technology called a spectrometer, which is a machine that can measure the different colours of light. The first version of our spectrometer was designed to be fitted to a satellite to measure the atmosphere on Mars. Our version is very tough and can be attached directly to machines, which is something that no other instrument like this can do.

Here’s a photo of our current prototype


You put samples on the silver disc at the top, and light shines into it through the little black-looking dot. Then the light reflects back into the body of the instrument where we measure its colour.


Our spectrometer doesn’t look at visible light like you would see in a rainbow, but infrared light that is invisible to our eyes. When you shine infrared light through different things (like butter, or chocolate, or plastic, or lots of other things), very specific colours are absorbed by the material, depending on what it is. This means that if you know which colours are absorbed, you can work out exactly what the material is made from. People who make all kinds of everyday chemicals really want to be able to check that they’re making the the right thing, and our spectrometer helps them to do that.

Our spectrometer is a Fourier Transform spectrometer. This means that it works by creating something called an interference pattern by splitting the light going into the spectrometer into two beams, and then reflecting each of these off a different mirror. When you bring the beams back together, you get a pattern of lines, which we look at with a special camera. Each different colour of light creates a different patten of lines, just like a fingerprint, so we use some maths (a Fourier Transform) to work out what the pattern means and tell us which colours of light are present.

My last job was using lasers as giant flash lamps to take photographs of fast moving particles (things like sand, or droplets of paint in a spray) and then using computers to work out how fast they were moving or what size they were. I used this so that people who make cars could make sure that the paint was perfect, or so that the people who make jet engines could know whether their engine would work in the desert. I designed the equipment and then took it all over the world to help people who’d bought it or had a problem to solve where we could help.
Medical Diagnostics
At the same time as that, I had a part-time job where I built machines to look at something called immunoassay plates. These are the plates that you see ‘scientists’ moving liquids about in when the TV news wants to talk about genetics. They are actually a load of little wells where you can mix cells and stains to work out whether the cells have a particular disease, or some other quality. My machines looked at the results of the staining and then helped researchers to diagnose the disease or find what they were looking for in a systematic way.
Gas Detectors
Before that, I worked to invent very compact sensors to detect gases using light (similar to the work I’m doing now) which were made from optical fibres, and before that, I did a PhD in Physics where I tried to make as much laser light as possible go through optical fibres without them exploding.

My Typical Day

I work with four other people to improve how our spectrometer works, invent new ways to measure things with it, and understand what it’s telling us.

Since we’re only a young company, we don’t really have specific jobs and we don’t really have customers yet either. This means that every day is actually quite different.

Here’s a picture of my desk with one of our early prototypes on it.


For example, in the week before the Christmas holidays, I spent a day trying to look at the light emitted from a furnace in a metal refining factory (this involved setting up our equipment in a very dirty place within the factory and trying to make sure that the input lens was pointing at the correct place in the furnace, which itself was nearly 1000ºC).

The next day, we analysed the data with some software that we’ve written to try to make sense of the information that we’d collected.

The day after that, I used one of our new prototypes to try to understand a problem that we’d been having with some measurements. This involved collecting lots and lots of data with the spectrometer, then trying to find patterns in it that matched up with things that I knew were going on in the laboratory (like people coming in and out). Then, I used our analysis software to plot those things onto graphs so that I could discuss and explain my findings with my colleagues.

The next day, I built an environmental test chamber to test another spectrometer in different atmospheric gasses. Lots of gasses (things like water vapour and carbon dioxide, but also pollutants like nitrogen dioxide, nitrous oxide, and methane) absorb light that our spectrometer can measure. This means that we can see how much of each is around us when we make a measurement. The test chamber lets me check to see each gas individually by letting me make sure that the spectrometer is only submerged in pure nitrogen, then we can add other gasses as we want.


My Interview

What's your favourite food?

Ice Cream

What invention amazes you the most?

The internet. The amount that it’s changed in my lifetime — I can remember dial-up BBSs (ask your parents) — is astonishing.

What is the most fun thing you've done?

I’m loving watching my infant son grow up and learn to do new stuff.

What did you want to be after you left school?

A weatherman (or an inventor).

If you weren't an engineer, what would you be?

I can’t imagine doing anything different than the sort of work that I do today.

What's the best thing you've done as an engineer?

What or who inspired you to become an engineer?

I always loved taking things apart when I was little and then trying to understand how they worked. That is what made me become an engineer.

Who is your favourite singer or band?

iTunes says that it’s Arcade Fire that I’ve listened to the most.

If I could change one thing about the world...

My favourite CHRISTMAS LECTURE memory is:

I remember watching them when I was little and being amazed at the experiments that they were doing live on TV.

If you could do anything, how would you hack your home?

Give us a hack we can do at home!

Other stuff

Work photos:

Here I am at my desk.



On the day that I took this, I was using a special 3d modelling program to understand how the rays of light shine through our spectrometer, and was using that information to try to improve the design.

Here’s my desk today


Here’s a photo that I took of the satellite dish that’s next to my office, along with some hacking that I’ve done to make a light-painting rig.