After a kind introduction by one of the conference organizers, I presented the Monday afternoon plenary lecture at ICOOPMA 2010, an international meeting on optical materials and technologies. Budapest is a beautiful city rich in history and culture, but also the host to the horrors of World War II. The lecture hall, which was a large room in the lower level adjacent to a pool and reception area, could have been anywhere.
The gentle hum of the air conditioning system was barely perceptible, as it toiled to protect the room from the hot and muggy air that blanketed the city. My wife and I had traveled almost a full day to get to Budapest from Pullman, albeit in the relative comfort of business class, courtesy of a complimentary upgrade from Delta Airlines. The five star Intercontinental Continental Hotel provided a tad of luxury at a bargain price of $49 per night, thanks to Hotwire.com. But the purpose of my trip was to attend the meeting and to give my talk.
With 25 years of public speaking experience, I am pretty calm in front of crowd, but only when talking about physics. Ask me to say a few words at a wedding or a family event, and I am barely able to stammer out a few words before feeling sick. Physics provides the ultimate comfort. The enjoyment of presenting my work is akin to a parent bragging about the accomplishments of a child. But pride is not an accurate characterization of the feeling. It's more of a mutual admiration for the beauty and depth of how mother nature has written her story in the fabric of our universe. I am merely the story teller.
I derive great satisfaction in sharing insights with a couple hundred scientists, many of them strangers, but all having in common an appreciation of the beauty of the physical world, and the potential for new wonders that it offers.
``So as you can see, the Photomechanical Optical Device represents the 5 device classes, but using only optics rather than electronics..." My trance-like state was briefly interrupted by the rumble of distant thunder. I continued to present my talk with great excitement. A second bolt shook the building, the lights faltered, then the room went dark for an instant until the emergency backup power kicked in. The main transformer for one region of the city was fried, leaving a nonfunctional projector for the second half of my Power Point presentation.
I continued to speak, waving my hands, and making air drawings to get though the remaining part of my talk. While the lack of visuals undoubtedly detracted from the information that I tried to convey, it made my talk more memorable than if all had gone smoothly.
At the end, I fielded many questions and comments - a sign that people were listening and were interested in the topic. After the Q&A, the conference organizers presented me with a bottle of Chardonnay with a special label sporting my name and the conference's name and coordinates. I was also given a Rubik's cube, which I believe was invented by a Hungarian. After the event was over, several more people hung around to ask questions and make comments.
We hailed a cab back to the hotel, and prepared for our return trip, which commenced with a 3:00am wake-up call and a 4:00am shuttle to the airport. We ended up missing a connection that prolonged our travels over eight hours. In the end, I was satisfied with the trip - not because I could add another destination to my list of travels, but for the opportunity to share with others the work that I love. We will be landing in Seattle in an hour, and will make the 5-hour drive to Pullman, getting us home by about 3:00am. The stresses associated with the start of an academic year will be upon us when we awaken, but I am also looking forward to all the new results awaiting me in the minds and notebooks of my students and collaborators.
I can't wait to get home!
Showing posts with label Budapest. Show all posts
Showing posts with label Budapest. Show all posts
Wednesday, August 18, 2010
Thursday, August 12, 2010
Kicking Around New Ideas
For a couple months now, we have been struggling with calculations of the nonlinear-optical response of quantum wires. Our idea is to build up complex structures by connecting together pieces of straight wire segments. The problem is that the sum rules appear to have pathologies. But in reality, the problems lie in the way that we idealize the wire.
As I discussed in a previous post, the case of the quantum rotor is a specific example that had been treated rigorously by Stavros Fallieros. I had an idea of how to apply a similar argument to a straight section of wire. The upshot is that along a wire, the sum rules hold. The problem with an idealized one-dimensional wire is that the wave function is by definition confined to the wire, and therefore vanishes outside. By the Heisenberg uncertainty principle, a particle that is confined in that way must have an infinite transverse momentum, implying an infinite energy state.
If these infinite energy states are included, the sum rules are obeyed. I came up with a simple textbook approach that models transverse confinement with a Dirac delta function potential in the limit when the strength of the delta function is infinite. While I had not solved the full problem, I wrote up the concept in a file LaTeX where I wrote out the form of the solutions. Then, I passed the document along to my students for them to do the hard part: evaluating infinite sums of complicated expressions in the limit when various parameters are large and small. Since there are no loopholes in the way the sum rules are derived, I am confident that this approach will work.
The other day, after I emailed this file to the students, we had a spirited debate. They disagreed with my approach and gave all sorts of counterarguments to prove me wring. They constructed special cases that seemed airtight arguments against my approach. But slowly, they became convinced; not because I am the expert, but because my argument is sound. This is one of the most satisfying aspects of the community of science. In the end, reason wins. This time, I may have been vindicated, but I have made enough mistakes in the past to not be overly dejected when I am proven wrong. Being scientists requires us to admit error.
As an update to one of our papers that was initially rejected, in the process of responding to a substantive comment made by one of the reviewers, David Watkins found an intrinsic hyperpolarizability that exceeds unity - an impossibility, according to my theory. Though my theory has been tested over an over again using different computational techniques under a broad range of conditions, I panic when it appears that I might have missed something. David and I sent many emails back and forth on the topic, trying to understand if somehow the sum rules were being violated by the new case under study. To my delight, David found and fixed a couple of bugs in his code, which solved the problem. The results for this new case is now consistent with all our other calculations.
On another front, three students from my nonlinear optics class and I had finished a nice paper on cascading at the beginning of the summer. As I had reported in a previous post, just prior to submitting the paper, we had found a case where the fundamental limits were exceeded. Since then, we have tried all sorts of approaches to reconcile the problem, but to no avail. Nathan, the lead student on the project, believes that cascading is a way to beat the limits. However, based on general principles, I know the limits must hold. And it's not that I want my theory to be true, but, based on general arguments, the cascading results - which are a special case - must agree with the more general theory. If a specific case appears to violate the more general one, it is incumbent upon us to track down the source of the inconsistency. In other words, we have to specifically show how this case falls outside the realm of the theory. At this point, cascading seems to be formulated in a way that makes it a simple subset of the more general theory.
I have been writing much about theory, but our experimental work has been going well. Shiva has built a beautiful temperature-controlled chamber that will allow him to do experiments from temperatures well bellow ambient to over 100 C. Since the temperature-dependence of a measurement provides a window into the energetics of a process, we hope the new experiments will provide us with a clue as to the metastable species involved that usher self heal self healing of a molecule upon photodegradation. In parallel, I am trying to work out a general theory of self-healing based on our past observations. The real test of this theory will be its power to predict the behavior of new observations as better experiments push the envelope of our knowledge. As a sneak preview, the theory includes a recovery process that is akin to stimulated emission, but in the case of dye recovery, has to do with coupling between the guest molecules and phonons in the host polymer.
Prabodh, a new graduate student in our group is specializing in making a large variety of samples so that he can study how the dopant and polymer host affect the healing process. Ben is doing a a series of experiments to optically image the damaged areas to better pin down the population dynamics, and he is building a new experiment that will allow us to determine the absorption spectrum at each point in the damage region. The combination of new samples and new measurements will provide valuable complimentary data that will undoubtedly aid us in unraveling the puzzle of self healing.
Nathan is getting additional data on the photomechanical response that appears to be consistent with our models. While the results are giving us insights into the new class of liquid crystal elastomeric materials, our conclusions appear to be at odds with those of our collaborators, who supplied us with the samples. I am confident that we will eventually reach a consensus because the truth always bubbles to the top. Even if we are proven right, we most likely have only part of the answer. More interesting mysteries are undoubtedly lurking at the next layer of depth.
Xianjun is in the process of calculating the response of Photomechanical Optical Devices (PODs), with the goal of predicting how they will behave when acting in series. This is a highly nonlinear problem, with complex solutions. At this stage, we are still struggling with the relatively simple things, like the response of a single nonlinear etalon. More complex systems will require us to consider more subtle issues and to be clever in our approximations to solving the full problem. In parallel, Xianjun is starting experiments to burn Bgragg gratings in polymer optical fibers with the goal of making and characterizing PODs. Measurements will play an indispensable part in developing our numerical models.
I hve more to write, but our flight to Amsterdam is boarding. This long trip will eventually lead us to Budapest, where I am giving a plenary lecture on self healing and photo mechanical effects. I apologize for any typos that resulted from my haste, and will write about the meeting upon my return.
As I discussed in a previous post, the case of the quantum rotor is a specific example that had been treated rigorously by Stavros Fallieros. I had an idea of how to apply a similar argument to a straight section of wire. The upshot is that along a wire, the sum rules hold. The problem with an idealized one-dimensional wire is that the wave function is by definition confined to the wire, and therefore vanishes outside. By the Heisenberg uncertainty principle, a particle that is confined in that way must have an infinite transverse momentum, implying an infinite energy state.
If these infinite energy states are included, the sum rules are obeyed. I came up with a simple textbook approach that models transverse confinement with a Dirac delta function potential in the limit when the strength of the delta function is infinite. While I had not solved the full problem, I wrote up the concept in a file LaTeX where I wrote out the form of the solutions. Then, I passed the document along to my students for them to do the hard part: evaluating infinite sums of complicated expressions in the limit when various parameters are large and small. Since there are no loopholes in the way the sum rules are derived, I am confident that this approach will work.
The other day, after I emailed this file to the students, we had a spirited debate. They disagreed with my approach and gave all sorts of counterarguments to prove me wring. They constructed special cases that seemed airtight arguments against my approach. But slowly, they became convinced; not because I am the expert, but because my argument is sound. This is one of the most satisfying aspects of the community of science. In the end, reason wins. This time, I may have been vindicated, but I have made enough mistakes in the past to not be overly dejected when I am proven wrong. Being scientists requires us to admit error.
As an update to one of our papers that was initially rejected, in the process of responding to a substantive comment made by one of the reviewers, David Watkins found an intrinsic hyperpolarizability that exceeds unity - an impossibility, according to my theory. Though my theory has been tested over an over again using different computational techniques under a broad range of conditions, I panic when it appears that I might have missed something. David and I sent many emails back and forth on the topic, trying to understand if somehow the sum rules were being violated by the new case under study. To my delight, David found and fixed a couple of bugs in his code, which solved the problem. The results for this new case is now consistent with all our other calculations.
On another front, three students from my nonlinear optics class and I had finished a nice paper on cascading at the beginning of the summer. As I had reported in a previous post, just prior to submitting the paper, we had found a case where the fundamental limits were exceeded. Since then, we have tried all sorts of approaches to reconcile the problem, but to no avail. Nathan, the lead student on the project, believes that cascading is a way to beat the limits. However, based on general principles, I know the limits must hold. And it's not that I want my theory to be true, but, based on general arguments, the cascading results - which are a special case - must agree with the more general theory. If a specific case appears to violate the more general one, it is incumbent upon us to track down the source of the inconsistency. In other words, we have to specifically show how this case falls outside the realm of the theory. At this point, cascading seems to be formulated in a way that makes it a simple subset of the more general theory.
I have been writing much about theory, but our experimental work has been going well. Shiva has built a beautiful temperature-controlled chamber that will allow him to do experiments from temperatures well bellow ambient to over 100 C. Since the temperature-dependence of a measurement provides a window into the energetics of a process, we hope the new experiments will provide us with a clue as to the metastable species involved that usher self heal self healing of a molecule upon photodegradation. In parallel, I am trying to work out a general theory of self-healing based on our past observations. The real test of this theory will be its power to predict the behavior of new observations as better experiments push the envelope of our knowledge. As a sneak preview, the theory includes a recovery process that is akin to stimulated emission, but in the case of dye recovery, has to do with coupling between the guest molecules and phonons in the host polymer.
Prabodh, a new graduate student in our group is specializing in making a large variety of samples so that he can study how the dopant and polymer host affect the healing process. Ben is doing a a series of experiments to optically image the damaged areas to better pin down the population dynamics, and he is building a new experiment that will allow us to determine the absorption spectrum at each point in the damage region. The combination of new samples and new measurements will provide valuable complimentary data that will undoubtedly aid us in unraveling the puzzle of self healing.
Nathan is getting additional data on the photomechanical response that appears to be consistent with our models. While the results are giving us insights into the new class of liquid crystal elastomeric materials, our conclusions appear to be at odds with those of our collaborators, who supplied us with the samples. I am confident that we will eventually reach a consensus because the truth always bubbles to the top. Even if we are proven right, we most likely have only part of the answer. More interesting mysteries are undoubtedly lurking at the next layer of depth.
Xianjun is in the process of calculating the response of Photomechanical Optical Devices (PODs), with the goal of predicting how they will behave when acting in series. This is a highly nonlinear problem, with complex solutions. At this stage, we are still struggling with the relatively simple things, like the response of a single nonlinear etalon. More complex systems will require us to consider more subtle issues and to be clever in our approximations to solving the full problem. In parallel, Xianjun is starting experiments to burn Bgragg gratings in polymer optical fibers with the goal of making and characterizing PODs. Measurements will play an indispensable part in developing our numerical models.
I hve more to write, but our flight to Amsterdam is boarding. This long trip will eventually lead us to Budapest, where I am giving a plenary lecture on self healing and photo mechanical effects. I apologize for any typos that resulted from my haste, and will write about the meeting upon my return.
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