Okay, what have I accomplished? With the help of Clément, my Fourier-transform code in Igor spits out lovely optical path length calculations. I've tested it on three typical Fabry-Perot cavities of known width, and the results agree with the nominal width to within a few percent, the accuracy also reported by the group in their 2007 paper on the topic. So my code is probably working properly. The regular FP's have lovely, evenly-spaced peaks in path-length-space, corresponding to light that travels twice the width of the cavity (by reflecting once off the side), four times, six times, and so on...the amplitude of each successive peak decreases, indicating that the once-reflected path is the dominant one. So far so good. When I start looking at the non-parallel FP's, things go a bit wonky. All the amplitudes decrease, first of all, indicating that the poor little microcavity is having some trouble lasing. Some multiples are skipped...I'm not really sure what's happening. Mélanie will save the day!
I'm also supposed to be investigating the lasing thresholds, by tracking the amplitude of some particular spectral peak (not the transformed peaks) with increasing pump energy. I've taken a fair amount of data, but have yet to fully analyze it. By virtue of not falling asleep while taking data, I've already noticed that the threshold is increasing as the angle of the sides increases. This seems sensible enough. Stay tuned for more exciting discoveries!
Yesterday happened to be the longest day of the year. Happy solstice! Et joyeuse Fête de la Musique! Apparently there's a tradition (a summary is here) of an evening of music everywhere in Paris - ensembles, bands, street musicians, professionals, amateurs - everyone sets up shop anywhere and everywhere and plays all night. The other students in my lab group talked about it all week, and several of the REU students made plans to walk around downtown and hear what we could hear.
I was rather worried when the hail started in the afternoon. But it turned out that Paris was just getting the bad weather out of its system, as the evening was gorgeous. With Mélanie's emailed permission, I left work a few hours early. Kierstin and I headed out to find the Pantheon, to see it and to look for the Celtic musicians I promised, having looked over some handy websites earlier. We never found those musicians (I learned later they were nearby but not actually at the Pantheon), but had a pleasant walk. Kierstin, who is madly in love with Proust and his search for lost time, went into raptures of delight upon discovering and purchasing a macaroon cookbook from a bookstore named Le Temps Retrouvé. So the quest was successful in its own way.
Then we took the RER one stop north to the Denfert-Rochereau area. There was a huge stage set up near the station, but no bands yet (though they were piping in music that I recognized from my childhood). I really like this area of the city. It's almost in the heart of the city, but it's more residential than touristy. It feels real. So I was perfectly happy when we decided to walk from there to Notre Dame. Maybe an hour and many map-consultations later, we made it! All roads lead to Notre Dame in the end. We were just in time to meet Mir, Josh, and a large international group of students from their lab.
To shorten a story complicated inevitably by the dynamics of large groups, Mir, Josh, Kierstin, a late-arriving Margaret, and I wound up wandering the streets listening to various groups. There were some very good drummers by St. Michel, a brass band in the street behind them, an amateur rock group who sang in German, some soulful guitarists...everywhere there was music. And so many people! Despite my general dislike of crowds, I had a great time. And I ate a cinnamon-sugar crêpe. Yum.
The highlight of the evening was Josh's own saxophone performance. We found a quiet place right down by the Seine and he gave a concert that it was a pleasure to hear. Though there wasn't much foot traffic nearby, the myriad sight-seeing boats cruising up and down the Seine were a prime audience, and the passengers applauded him as they passed. Way to go, Josh!
The public transportation ran until 5:00 am last night, but we made it back to the dorms around midnight. If you had asked me a year ago - a few months ago even - I never would have guessed that I would spend this summer solstice listening to street music in the heart of Paris.
This evening has been quieter. Mir, Kierstin, Linda, and I leave for Bonn at 6:00 tomorrow morning! So no posts for a few days, but I hope to have many exciting adventures to report after the weekend.
A lundi!
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