Nail Varnish Ain't Just For Nails

I tried using the extremely advanced and sophisticated technology that is clear nail varnish to fix the fibre onto the glass slide - it works quite nicely. A bit of nail varnish remover recovers the glass slide and fibre too so nothing has to go to waste.
I did some reading up about the experiment this afternoon. I wonder if I can calculate the viscous drag and 'terminal velocity' of the beads when they are trapped and propelled. I have to sort out the oil immersion objective and CCD camera first though.
I am beginning to feel like this experiment will not be done within the next few weeks...

The Black Arts

So, I'm waiting for the battery cap for the detector. While it wings it's way to me, I am concentrating on fibers. Yuqiang spent this afternoon showing me how to pull fibers with the heat rig and then glue the tapers to glass slides.

• Total number of fibers broken: 6


• Number of fibers broken during pulling: 3


• Number of successful tapers: 2


• Number of fibers that caught fire: 1

I don't think these are very encouraging statistics. Jonathan described fiber-pulling as a black art. It seems very unpredictable - the same set of parameters giving you different results each time. After I had broken 3 fibers on the pulling rig, Jonathan suggested reducing the gas flow. This worked perfectly - my last taper was a beauty. Had to break it and throw it away though because tapers are basically poisonous needles.
I've noted down the frequency and time settings for pulling and reversing the rig for next time. I have to pull a shorter taper tomorrow or next day so that the cladding can be glued (or nail-varnished) onto the glass slide.

Gluing the fiber to the slide isn't as horrible as I thought it would be. After clamping the slide to a movable stage, it's purely an eyeball alignment process. After raising the slide up to a fiber mounted across two posts, you finely adjust it until the fiber and slide are within a millimetre of each other. If I wanted to be more accurate, I could use the focus dial of the microscope and see how many rotations are needed to focus the fiber and slide, in turn, at either end. Each rotation is calibrated in terms of distances. But, I'm only fixing a fiber to a slide which doesn't require extreme precision so that detail is unecessary.

Cleaving & Splicing

This evening, Yuqiang showed me how to cleave and splice fibers. I wanted to add a filter before the photodetector to reduce the laser beam power. The Thorlabs tech support guy told me that, although the manual says the damage threshold is 70mW, the detector gets fried with 60mW. Michael got me a small double lens stage with fibered connections. I had to splice my laser fiber onto the stage. The first splice didn't work so well but my second go was perfect.
I received the new photodetector before I went down to Tyndall (I convinced the Thorlabs tech support that the detector was broken before I got at it!). I had a suspicion that the laser power had killed the ball lens in the detector, but it didn't really make sense because I wasn't getting the correct voltage response on the oscilloscope even below the current (lasing) threshold. I hope the new detector does its job.

Detector Woes

Well, today sucked. There's no better way to put it. My detector doesn't work and the guy from Thorlabs thinks I broke it - which seems to be a very popular notion in the lab this week despite the fact that I have not actually broken anything yet. Yeah. Take note guys. I guess my best bet for now is to move onto the fibre pulling and imaging side of things. I have to sort out a proper CCD camera and set up the oil imersion microscope. Maybe tomorrow will be better.

Filling In The Blanks

Right - posting here has been a bit... Irregular. Although I was under the impression that my IRCSET application had floated off nicely into cyberspace to be picked up by referees and administrators and judging commitees, it was, in fact, lost and alone in computer-land. This year, IRCSET have attempted a software upgrade but seem to have left out the part where they debug and test it, resulting in many lost and faulty application forms. I have created a second application and Sile is going to submit it if they cannot find my original submission.

I characterised the laser today using both a diode and a spectrum analyser. The diode gave me a nice neat curve while the spectrum analyser allowed me to see some 'messy' data because of mode hopping and losses due to fibre connectors. The spectral power given by the spectrum analyser is essentially what is displayed in the voltage-current curve. The lasing threshold occurs between 20-25mA. I'm going to have a look at this again using my new detector and an oscilloscope either tomorrow or Thursday. Meanwhile, I have some rotten condensed state physics homework to finish.

Happiness Is...

...A working laser!

I took some brief data with a power meter just to get an idea where the lasing threshold was - see the graph below.

Hide and Seek

I'm not updating because my physics project has turned into an electronics project. I haven't even got the laser turned on yet - what will it be like when I'm actually attempting to trap with the evanescent field?!

New temperature and current controllers were ordered for me last week, and eventually the current controller turned up today. After various combinations of fuses, Kieran and me finally got it working. But we need the (still missing) temperature driver to check whether it does, in fact, work with the laser.

In other, much nicer, news, my IRCSET application is 98% complete. I hope to finish the last 2% off tomorrow.

Stupid Laser

Well, it is more likely "stupid me".
The laser didn't work. Which meant that I had to check each pin in the current and temperature drivers. But I still couldn't find the missing connection.

*grumble grumble*

I won't leave the lab tomorrow until I have it sorted!

15 Seconds Of Fame

After a very, well... eventful lunch this afternoon (thank you An Tuath Nua, TG4!), I finally got to practise some soldering in preparation for the connecting of laser and drivers. I soldered absolutely every wire onto every breadboard within reach. I'm pretty happy to do the real job now of connecting the 15-pin jack to 9-pin jack for the driver (with Michael's verification that I've matched the correct pins together in case of laser-explody issues).

This week I have focused on my IRCSET application more than anything (and my homework due for next week has suffered - but it's all about priorities, isn't it?). The application form takes a healthy chunk of time to complete mainly due to the personal proposal and project proposal. Writing 2000 words on why I am so wonderful and perfect for an MSc is tougher than you think!

Since the beginning of this project and making the decision to apply for an MSc with the group, I have realised there are many 'hidden extras' involved in working in Tyndall. Some extras are nice, like the French summer school for newbies. Some extras are surprising - my participation in the Cork City Marathon comes to mind... But then, there's the Journal Club. Public talking is just one of those things, isn't it? I'm scheduled to do a Journal Club talk on March 14th. Originally, I choose the paper written by Brambilla, Murugan, Wilkinson, Richardson dealing with bead velocities in evanescent fields. But then Michael gave a talk today on dark matter and the accelerating universe, so I was inspired to pick a completely random, off-the-wall paper rather than a quantum optics one. And I found an absolute cracker about spiderman suits and gecko gloves! My next aim is to mention Bose-Einstein Condensation somewhere during the presentation...

Oh and, the title of the post was a reference to our lab being featured in the TG4 programme 'An Tuath Nua'. Except, it actually wasn't featured at all despite Sile, Michael and Thejesh's efforts. We still got the free lunch though.

It Was Mentioned...

It was mentioned to me today that I hadn't updated in a week... But I have really been working! On Thursday, I accidentally volunteered myself for some programming courtesy of the guys in the lab. They wanted a Labview program that took pressure readings from a vacuum monitor every x seconds - the only problem being that the manual for the monitor appeared to be non-existent. I searched online but there was nothing except a horibly brief information sheet for it. No manual means no idea how to install a LabView driver. On the plus side, I got to learn LabView which I find quite delicate, and after a summer full of raw, unadulterated MS Visual C++, much easier on the brain.

I'm going to do some practise soldering before I connect up the laser drivers and laser tomorrow. Don't want it being messy!