h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Are you still there? Sorry for simply leaving a message, but I am new here and trying to find my way around... all alone...
Have been to Edinburgh lst July and loved it.

Glad you enjoyed it.

I *am* still around but can't post much due to work commitments.

I see that you've been visited by the welcoming committee - they're a great bunch of people who can show you the ropes.



Stop by for a now and then, if you like - although it may be a long time between refills

ok, I am patient, and I am on your trail now, LOL let me add and some and hopefully we can meet again, I am like you now always able to communicate in here. Easier to email or IM but not surfing.

Where does your name come from? is this a form of Iain???

On my trail?

*looks furtively over shoulder*

OK, but don't say you've not been warned...



Actually, you haven't, have you?

My name is a kind of derivation of Iain - both come from the same root as John, Juan, Johann and so on. It's an anglicised version of the Gaelic name Eoin - pronounced a little like Owen. Mine is pronounced more like "Yoo-an".

"Canicula" - means little dog?

*tiptoes from behind*

*taps him on his shoulder*

Hey!!! you just couldn't see me as I had ducked out... yesterday my work load was stronger than I.
Canicula means little dog and is also the star Sirius in Canis Major. Refers to my favorite character in a book series.

So Euan is pronounced as Yoo-an, but Iain like Ee-a-een? Is this your real name, sounds very celtic too me.

It is my real name!

I couldn't think of a witty name to use, so thought that I might just as well use my real one. It is Celtic, and I am a Scot, so it's appropriate. I have my parents to thank for that Iain is pronounced 'ee-an', as far as I am aware, although that could be Anglicised.

I've never heard of Sitius being called Canicula - I would have thought that it *might* have been Procyon, given that's in Canis Minor. It's been too long since I did any serious astronomy, though, that I might have forgotten.

Bad day at work? What is work, if you don't mind me asking?

Funny, but I love your name... LOL, would be interesting to find out the person behind it.

My work is a bit difficult to describe. I have majored in chemistry, but now I am working as a kind of global quality manager. In our little tiny department we are working with leadership to find the best quality strategies and as we are a big subsidiary of an even bigger company we often have to implent their ideas. Balnace scorecards, six sigma and so. This work includes a lot of travelling. Like it and not,depends.

And you? with what work are you paying your bills?

Oh and may I add you to my friens list? Don't know what it does but still?

Of course you may - what it does is that anytime a friend creates a new journal entry (like your entry entitled "Today is interesting") then you will automatically be subscribed to it. Be warned, some people are prolific journalers.

How do I pay my bills? Well, I'm a Ph.D student of laser physics, that's how. We don't exactly have things like majors in the sciences over here (well, a few have what might pass for major/minor schemes) but I suppose you could say I majored in laser physics with a substantial minor in general physics, with a little astrophysics thrown in for good measure (sub-honours, but hey, who's counting ).

Oh yes, and I'm married to an (ex-physics student) accountant - that helps alleviate the strain a litle bit.

Thanks for explaining the friends list to me! Ah, I think I am more on the lazy side.

Laser physics, I am impressed. Oh I am working for a optical fiber company and whre lasers play a significant role in communications.

Don't know how to explain my course of studies, as I studied in Germany chemistry, which may sound like a Bachelors in Physics, dunno, but I had what it's called "Vordiplom" in Ohysics and Chemistry, "Diplom" in Chemistry (which should be the masters) and had my doctorate studies in crystallographie. Good for you that you found a good "match"! Makes life much easier when you have the same level of understanding.

Ok, offffffffff to work

Good match it is - although I wish that some of her work wasn't so far away, or time consuming.

Optic fibres are fun, although I have seen one let go because the laser pulse sent down it was too intense! It was quite funny to see the glass just melt...

So, from crystallography to optic fibres - quite a change, no?

gosh that must have been a nice temperature then! Silica glass the substance for optical glass fibers will melt at 1500 K (or so??).

Yup qas quite a change, especially as the cabling materials are more or less thermoplastic!

What kind of experiments are you working on, when you might tell?

The laser pulses have peak powers in the mid gigawatt range and thus develop some nice temperatures. We use it for making holes in things (like metal, glass, etc).

What do I do? That's a little complicated. I think my Ph.D will be titled 'Nonlinear microscopy' or something along those lines.

How much do you know about optics? And specifically the interaction of light with materials (absorption, emission, refraction etc.)?

Uhm addmittingly I have forgotten a lot, but I had 2 years of Physics and a Bachelors in Physiscs, and then in instumental analytics the interaction of electrons and light are the basics for Infrared, UV, and other spectrometrics (oops whats the word???), then of course the others like NMR which works with the nuclear spin. I don't know how the British University system works, the American is pretty different from the German one. In Germany we have to gain broad and deep knowledge, while in the US students gain very deep knowledge in a very narrowed field. For my masters tests I could choose in each field a specialised one, in inorganic the metal organic chemistry, in Physical Chemistry Instrumental Analytics (here you go!) and in Organic Chemistry a related field. Even in my PhD exam (the doctorate was in crystallographie, which means exploring crystal structures of compounds you "created") I got examined in Instrumental Analytics. Guess I do have some knowledge about the topic.

OK. Stand by for some technical stuff.

In electromagnetics, the response of a material to an external electric field is governed by a quantity called the susceptibility, symbol chi. This leads to a polarisation of the material, P, which is generally proportional to the magnitude of the electric field.

Should bring back some memories!

If a very high external field is applied, the response of the material becomes non-proportional. The linear relationship between field and polarisation becomes a power series, with terms in field squared, cubed and so on.

May be familiar?

Therefore we say that the response is nonlinear - and that's what I do, in general terms. It's nonlinear optics - the high external field in generated by a femtosecond laser.

In linear optics, an atom will emit and absorb radiation in single photon steps (for example, He:Ne laser emits radiation at 633nm. The radiation for this step is only at 633nm). When a high power pulse interacts with a material it is possible to get simultaneous absorption of two (or more) photons to excite to the same energy level (in the case I mentioned, if the He:Ne absorbed normally at 633nm, a high power pulse at 1266nm would be absorbed - half the energy per photon, but two photons simultaneously absorbed).


I use this effect to do microscopy. The laser can be focused down to a very tight spot - giving high lateral resolution. The fact that the effect I use is dependent on the intensity of the laser means that if the beam is tightly focused (and therefore highly divergent after the focus) then the absorption is generated in only a small volume in space. Therefore, by scanning the spot in three dimensions I can build up a high resolution 3D image of samples.

The powers I use are fairly high - for example, in one experiment I use a 1 watt (time average) Ti:Sapphire laser. One watt sounds pretty low, but the pulses come in 100 femtosecond packets, seperated by 10 nanoseconds. Therefore, the peak power is around 100 kW. Another system I use has an even higher ratio - goes to 10 GW.

Yes, it did brought back lots of memories. Just wondering, the effect that you have a resonance with the double (and triple and so forth) to the original wavelength is used in other techniques as well.
May have to think about it over the night... will be back with questions.

Thanks a bunch!

You're welcome. I see you're online just now.

Was it the Raman spectroscopy? The guys at our university played with a powerful laser, green light, very experimental.
Geez, it's been a long time, I need to look it up in my books.

What are your findings so far?

Could be Raman. That's a nonlinear process.

What have I found? Well, I've imaged semiconductor circuitry and fluid flows so far. I can take 3d images of computer chips (in principle - it can be a little fiddly). I can monitor two fluids mixing in some detail too. Not particularly excitin, but it works.

Hm I think it's excitin, you are gettin pretty into smallest ranges. For computer chips there might be even a commercial application coming out of this...

Raman is non linear, and we use it to characterize molecules with not polar or symmetrical groups. the other ones are accessible with Infrared but even there we used the overtones for some analysis function.