We left Michigan around 9:40 last night (EST) and arrived in Paris this morning, local time of about 1130. The flight was a little less than seven and a half hours, and I probably got 3 hours of sleep at most on the plane, so I'm a little wiped out. I had the fortune to sit in a seat where half the leg room was taken up by an air conditioning unit (or some other nondescript black device with vents), so not only did my backpack not fit under the seat completely, but my badminton racquet didn't either, and I spend the entire flight with the racquet between my legs and Svelto's lasers on my lap.
After getting through customs and claiming our bags (which took a surprisingly short amount of time) we bought rail passes. The navigo passes don't start until Monday, so we had to buy 1-way tickets to Paris, which cost 8.50 e.
After getting to the hotel, we met with Francois and Adrian, two Paris Tech students who took us to go see a rugby game. It was pretty helpful to get their input, as they know the area infinitely better than we do.
I'm quite tired from today/yesterday. I don't have plans tomorrow other than going to an Irish church for mass, but until then, I plan to get well acquainted with my bed.
Saturday, May 29, 2010
Thursday, May 27, 2010
Orientation, Day 2
Today we went on a tour of some of the CUOS labs at UMich. Despite the fact that I am an optics major, it was the first time I've seen a femtosecond laser. It makes this very interesting whining sound after being focused by a lens, and if one looks very very closely, one can see the pulses actually ripping the air molecules. It looks almost like a very very thin spider web.
We then looked at the Hercules laser, currently the most concentrated in the world. I don't remember exactly what order of magnitude it operated at at peak intensity, but I doubt I know the SI prefix for it.
I've been thinking more and more about my presentation on Friday. I've read several articles, most of which seem to be very material specific: we shot xx material with yy fs duration pulses and found an ablation threshold of zz fluence (J/cm^2) . I feel like I have the gist of what's going on, so I'm going to try and put it in writing.
A laser, often Ti: Saphire according to most of my sources, probably Q-switched, emits a fs pulse of light. Outside of the laser cavity, one mode of polarization is selected by a combination Glan (or other) polarizer and half wave plate and attenuated as necessary. The beam is then directed and focused onto the sample; the papers I've read have used copper, marble, aluminum, and even paintings. When the material is struck by the focused femtosecond beam, the outermost layer (to some depth in microns) is either sublimated or more likely ablated, that is, turned into a plasma and ejected. From the ejected plasma, the emission spectra of the ablated material may be determined. Via prior analysis, either chemical or spectroscopic on a small fragment of the artwork/metal, the user knows what materials constitute the artwork and what materials constitute the varnish/dirt layers. Via laser induced breakdown spectroscopy (LIBS) of the ejected plasma particles, a scientist may determine how deep into the varnish he/she has blasted, and also when to stop. An alternate method involves the use of light of a frequency such that the varnish is strongly absorbent, but the artwork is not. This seems more useful, as the process would thus be self limiting, but also more difficult to fabricate and would depend strongly on the molecular components of the artwork and varnish, whereas the former procedure could be universally applied.
My main problem is that I know exactly 0 about plasma physics. I'm going to try to delve into the subject a little bit, and learn more about what happens between the pulse striking the varnish, and a plume being emitted.
As for my project, according to the description, it will be a study of laser cleaning as a function of pulse duration. I haven't run across any papers on the subject, which is exciting.
We then looked at the Hercules laser, currently the most concentrated in the world. I don't remember exactly what order of magnitude it operated at at peak intensity, but I doubt I know the SI prefix for it.
I've been thinking more and more about my presentation on Friday. I've read several articles, most of which seem to be very material specific: we shot xx material with yy fs duration pulses and found an ablation threshold of zz fluence (J/cm^2) . I feel like I have the gist of what's going on, so I'm going to try and put it in writing.
A laser, often Ti: Saphire according to most of my sources, probably Q-switched, emits a fs pulse of light. Outside of the laser cavity, one mode of polarization is selected by a combination Glan (or other) polarizer and half wave plate and attenuated as necessary. The beam is then directed and focused onto the sample; the papers I've read have used copper, marble, aluminum, and even paintings. When the material is struck by the focused femtosecond beam, the outermost layer (to some depth in microns) is either sublimated or more likely ablated, that is, turned into a plasma and ejected. From the ejected plasma, the emission spectra of the ablated material may be determined. Via prior analysis, either chemical or spectroscopic on a small fragment of the artwork/metal, the user knows what materials constitute the artwork and what materials constitute the varnish/dirt layers. Via laser induced breakdown spectroscopy (LIBS) of the ejected plasma particles, a scientist may determine how deep into the varnish he/she has blasted, and also when to stop. An alternate method involves the use of light of a frequency such that the varnish is strongly absorbent, but the artwork is not. This seems more useful, as the process would thus be self limiting, but also more difficult to fabricate and would depend strongly on the molecular components of the artwork and varnish, whereas the former procedure could be universally applied.
My main problem is that I know exactly 0 about plasma physics. I'm going to try to delve into the subject a little bit, and learn more about what happens between the pulse striking the varnish, and a plume being emitted.
As for my project, according to the description, it will be a study of laser cleaning as a function of pulse duration. I haven't run across any papers on the subject, which is exciting.
Tuesday, May 25, 2010
A Clean Slate
This blog is to be used to chronicle the activities, laboratory or academic, I undertake in Paris as part of the "Optics in the City of Light" iREU program via University of Michigan. My project is on the cleaning of artifacts with femtosecond lasers, as might have been evident from the blog title and URL. Although I'm working for Gerard Mourou, it seems like I'll be primarily working with Bianca Jackson, a postdoc working at Institut de la Lumière Extrême (I'm really going to have to figure out how to get those accents and not just copy paste them).
I flew in to Michigan from Baltimore yesterday afternoon. We spent most of today cutting through red tape; getting ID cards and the like, and also watching a laser safety video. It sounds like tomorrow will be a little more interesting, with a presentation about France as a country to work in on tap.
We have to make presentations (for Friday) detailing what we think the primary question/focus of our research in France is going to be. I've read the articles Bianca sent me, now I just need to mull over what exactly I think I'm going to be doing.
I flew in to Michigan from Baltimore yesterday afternoon. We spent most of today cutting through red tape; getting ID cards and the like, and also watching a laser safety video. It sounds like tomorrow will be a little more interesting, with a presentation about France as a country to work in on tap.
We have to make presentations (for Friday) detailing what we think the primary question/focus of our research in France is going to be. I've read the articles Bianca sent me, now I just need to mull over what exactly I think I'm going to be doing.
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