Lasers
drorzel | June 29, 2011The first of the five categories of active research at DAMOP that I described in yesterday's post is "Ultracold Matter." The starting point for this category of research is laser cooling to get a gas of atoms down to microkelvin temperatures (that is, a few millionths of a degree above absolute zero. Evaporative cooling can then be used to bring the atoms down to nanokelvin temperatures, reaching the regime of "quantum degeneracy." This is, very roughly speaking, the point where the quantum wavelength of the atoms becomes comparable to the spacing between atoms in the gas, at which point the…
drorzel | June 28, 2011That's the title of my slightly insane talk at the DAMOP (Division of Atomic, Molecular, and Optical Physics of the American Physical Society) conference a couple of weeks ago, summarizing current topics of interest in Atomic, Molecular, and Optical Physics. I'll re-embed the slides at the end of this post, for anyone who missed my earlier discussion.
I put a ton of work into that talk, and had a huge amount of material that I didn't have time to include. I'd hate for that to go to waste, so I'm going to repurpose it for blog content over the next week or so. It'll probably be about a half-…
drorzel | June 16, 2011One of the odd things about going to conferences is the unpredictable difference between talks and papers. Sometimes, when you go to a talk, you just get an exact repetition of what's in the paper; other times, you get a new angle on it, or some different visual representations that make something that previously seemed dry and abstract really click. And, of course, sometimes you get new hot-off-the-apparatus results that haven't made it into print yet.
Maddeningly, there doesn't seem to be any way to know in advance which of these things you're going to get from the title and abstract. It…
drorzel | June 15, 2011Tuesday at DAMOP was dominated by my talk. Well, in my mind, at least. I suppose people who aren't me saw other interesting things.
OK, fine, I did go to some other sessions. I would link to the abstracts, but the APS web site is having Issues this morning.
In the Prize Session that always opens the meeting, Gerry Gabrielse from Harvard gave a really nice talk about his work on measuring the anomalous magnetic moment of the electron. This is the "g-factor" that I've cited before in calling quantum physics the most precisely tested theory in the history of science. Gabrielse is the guy behind…
drorzel | June 14, 2011That's the title of my talk this morning at DAMOP, where I attempt the slightly insane feat of summarizing a meeting with over 1000 presentations in a single 30-minute talk. This will necessarily involve talking a little bit like the person reading the legal notices at the end of a car commercial, and a few of the guide-to-the-meeting slides will have to flash by pretty quickly. Thus, for the benefit of those who have smartphones and care about my categorization of talks, I have put the slides on SlideShare in advance, and will embed them here:
What's So Interesting About AMO Phyiscs?…
drorzel | June 7, 2011I have to admit, I'm writing this one up partly because it lets me use the title reference. It's a cool little paper, though, demonstrating the lengths that physicists will go to in pursuit of precision measurements.
I'm just going to pretend I didn't see that dorky post title, and ask what this is about. Well, it's about the trapping and laser cooling of thorium ions. They managed to load thorium ions into an ion trap, and use lasers to lower their temperature into the millikelvin range. At such low temperatures, the ions in the trap "crystallize."
So, they've demonstrated that if you get…
drorzel | April 26, 2011This paper made a big splash back in November, with lots of news stories talking about it; it even made the #6 spot on Physics World's list of breakthroughs of the year. I didn't write it up then because I was hellishly busy, and couldn't take time away from working on the book-in-progress to figure out exactly what they did and why it mattered. I've got a little space now between handing the manuscript in last week and starting to revise it (probably next week), so while it's a bit late, here's an attempt at an explanation of what all the excitement was about.
So, what's this about, anyway?…
drorzel | March 11, 2011I've got three months to decide. I'll be giving an invited talk at the Division of Atomic, Molecular, and Optical Physics (DAMOP) with this title, with a goal of introducing the field to students and physicists from other fields:
In recent years, DAMOP has expanded to the point where the meeting can be quite daunting for a first-time attendee. This talk will provide an introduction to some of the most exciting current areas of research in Atomic, Molecular, and Optical physics, intended to help undergraduates, beginning graduate students, or physicists from other fields attending their first…
drorzel | February 20, 2011My talk yesterday at AAAS went well, if too long (the person who was supposed to be flagging the time got distracted, and never gave me any indicators that I was going on, and on, and on... But that's not really what I want to post about. The thing that triggered this is the speaker giveaway from AAAS, which is a combination laser pointer and 1GB USB drive.
"Big deal," you say. Those are cheap." And, yeah, they are, but when you think about it, that's really kind of amazing.
50 years ago, the laser had barely been invented, and was still in search of a problem. Nobody had yet had the idea…
drorzel | December 28, 2010It's the last week of the (calendar) year, which means it's a good time to recap the previous twelve months worth of scientific news. Typically, publications like Physics World will publish a list of top ten physics stories of 2010, but we're all Web 2.0 these days, so it seems more appropriate to put this to a poll:
What is the top physics story of 2010?survey software
I've used the Physics World list as a starting point, because you have to start somewhere. I added a few options to cover the possibility that they left something out, and, of course, you know where the comments are.
This poll…
drorzel | December 1, 2010I hadn't heard anything about Dance of the Photons: From Einstein to Quantum Teleportation before it turned up in my mailbox, courtesy of some kind publicist at Farrar, Straus, and Giroux, otherwise I would've been eagerly anticipating it. Anton Zeilinger is a name to conjure with in quantum optics, having built an impressive career out of doing laboratory demonstrations of weird quantum phenomena. He shared the Wolf Prize earlier this year with John Clauser and Alain Aspect, and the three of them are in a small set of people who probably ought to get a Nobel at some point in the near future…
drorzel | November 19, 2010Earlier this week, I talked about the technical requirements for taking a picture of an interference pattern from two independent lasers, and mentioned in passing that a 1967 experiment by Pfleegor and Mandel had already shown the interference effect. Their experiment was clever enough to deserve the ResearchBlogging Q&A treatment, though, so here we go:
OK, so why is this really old experiment worth talking about? What did they do? They demonstrated interference between two completely independent lasers, showing that when they overlapped the beams, the overlap region contained a pattern…
drorzel | November 15, 2010This is adapted from an answer to a question at the Physics Stack Exchange site. The questioner asked:
It seems that if the coherence length of a laser is big enough, it is possible to observe a (moving) interference picture by combining them. Is it true? How fast should photo-detectors be for observing of the interference of beams from two of the "best available" lasers?
This is a question about the itnerference of light waves, which is traditionally demonstrated via the famous "double slit" experiment, where a single laser is sent through a barrier with two narrow slits cut in it. The…
drorzel | September 3, 2010Over at Confused at a Higher Level, Melissa offers an alphabetical list of essential supplies for a condensed matter experimentalist at a small college. This is a fun idea for back-to-school time, so I'll steal it, and offer the following alphabetical list of essentials for Atomic, Molecular, and Optical physics at a small college, kind of a condensed version of the three part series I did a few weeks ago.
A is for Acousto-optic modulator This is a device that uses sound waves in a crystal to deflect light and shift its frequency. It's essential for rapid control of laser properties.
B is for…
drorzel | August 24, 2010Two papers in one post this time out. One of these was brought to my attention by Joerg Heber, the other I was reminded of when checking some information for last week's mathematical post on photons. They fit extremely well together though, and both relate to the photon correlation stuff I was talking about last week.
OK, what's the deal with these? These are two papers, one recent Optics Express paper from a week or so ago, the other a Nature article from a few years back. The Nature paper includes the graph you see at right, which is a really nice dataset demonstrating the Hanbury Brown and…
drorzel | August 18, 2010Most of the time, when we talk about seeing quantum effects from light, we talk about extremely weak beams-- looking at intensities where one photon more or less represents a significant change in the intensity of the light. Last week, though, Physics Buzz wrote up a paper that goes in the other direction: they suggest a limit on the maximum strength of a laser pulse due to quantum effects, specifically the creation of particle-antiparticle pairs.
This is a little unusual, in that most of the time when people talk about really intense lasers, they end up discussing them as an oscillating…
drorzel | August 13, 2010Some folks I used to work with at NIST have looked at cheap green laser pointers, and found a potential danger. Some of the dimmer-looking green lasers are not so dim in the infrared, and in one case emitted 10X the rated power in invisible light. This could be a potential eye hazard.
You can read their full report on the arxiv. It's got a nice description of how green laser pointers turn infrared light into visible light, which is really pretty awesome-- a guy I met at a conference once declared them the coolest invention ever, because it's "quantum optics in the palm of your hand." Better…
drorzel | August 12, 2010Following on yesterday's discussion of the vacuum hardware needed for cooling atoms, let's talk about the other main component of the apparatus: the optical system. The primary technique used for making cold atoms is laser cooling, and I'm sure it will come as no surprise that this requires lasers, and where there are lasers, there must also be optics.
There are lots of different types of lasers used for laser cooling experiments, but they all need to have certain properties: tunability, stability, and adequate power. Tunability is important because laser cooling requires light at exactly…
drorzel | July 9, 2010The big physics story at the moment is probably the new measurement of the size of the proton, which is reported in this Nature paper (which does not seem to be on the arxiv, alas). This is kind of a hybrid of nuclear and atomic physics, as it's a spectroscopic measurement of a quasi-atom involving an exotic particle produced in an accelerator. In a technical sense, it's a really impressive piece of work, and as a bonus, the result is surprising.
This is worth a little explanation, in the usual Q&A format.
So, what did they do to measure the size of a proton? Can you get rulers that small…
drorzel | June 22, 2010A press release from Harvard caught my eye last week, announcing results from Markus Greiner's group that were, according to the release, published in Science. The press release seems to have gotten the date wrong, though-- the article didn't appear in Science last week. It is, however, available on the arxiv, so you get the ResearchBlogging for the free version a few days before you can pay an exorbitant amount to read it in the journal.
The title of the paper is "Probing the Superfluid to Mott Insulator Transition at the Single Atom Level," which is kind of a lot of jargon. The key image is…