Journal

Tuesday, July 2, 2002

Today was my first full-day at the Laser Teaching Center. I have begun to do more in-depth research of optics. I have been reading about applications of optics in quantum computing. It appears that my Linux skills are a little rusty, but it's coming back to me. I would like to pursue my interests of both optics and computer science if possible.

Wednesday, July 3, 2002

My readings on quantum computers led me to Gaussian modes. I began reading more about optics in general, wave equations (specifically of plane waves), and Gaussian modes. I have found some very interesting ideas in Gaussian modes including diffraction of lasers whose beams are Gaussian modes and treated as such. I found the single-slit experiment performed with a Gaussian beam. I am looking further into research on them which I will perhaps pursue. It seems that focusing Gaussian beams is one of the problems of dealing with ion-trap quantum computers.

Monday, July 8, 2002

Today, I began looking into a concept known as "anomolous dispersion," where light can travel at a speed greater than c. (The phase/group velocity can exceed c, but the front velocity cannot as Special Relativity forbids.) It seems that it is not uncommong for the index of refraction to be less than 1. The index of refraction, which is a function of frequency, can be less than 1 when the frequency is near the natural frequency of the medium. Because the phase velocity can exceed the group velocity, some readings suggest that the light could emerge from the medium before it enters the medium. I am thinking of doing an experiment dealing with this lack of causality.

Tuesday, July 9, 2002

I have been studying superluminal transmission and am trying to devise an experiment dealing with the causality of the events. I have also been reading about potential wells and the use of materials with a negative index of refraction in conjunction with one whose natural frequency is close to that of the light emitted through it. I have also been working on a computer simulation of a Gaussian beam.

Wednesday, July 10, 2002

It seems that superluminal light-transmission is a lie. I do not quite understand the specifics of everything that happens, but it seems to me that the group velocity could be made infinitely large and that this is no real break-through in modern physics. I am still researching the topic and specifically appreciated the refraction/dispersion section of The Feynman Lectures. The computer simulation is coming--slowly, but coming.

Thursday, July 11, 2002

After finishing reading Feynman's QED, I feel inspired--unfortunately, still without specific direction (though I do recommend the book). I have been reading more about potential wells and may continue to work with superluminal transmission as an idea.

Monday, July 15, 2002

I am looking further into studying anomalous dispersion. I may experiment with the critical angle of light coming from air into a substance where anomalous dispersion will occur, forcing the light to reflect. I have also found a method whereby it is possible to heat and cool alkali metal ionic compounds in order to create optical wavelength absorption, but I do not yet know if this will be enough for anomalous dispersion.

Wednesday, July 17, 2002

Today, we had a lecture on lasers from Sam Goldwasser, an expert in the field. He spoke about tweaking and using lasers and specifically LIDAR, which is similar to RADAR but in a different band. I have also been reading the Feynman Lecture Series and reading up on F-Centers. F-Centers are a defect in crystals that appear when negative ions fall out of the crystal and single electrons take their place. In doing so, the crystals take on a certain absorption frequency in the optical range due to the electrons in the lattice.

Thursday, July 18, 2002

I am continuing my research on F-Centers. I think that I am going to use NaCl, and I think I am going to test for a couple of effects: photoelectricity and anomalous dispersion. I have yet to see where that will take me. I now also have a better idea of how to create F-Centers; however, I am not sure that I will be able to. I am looking forward to beginning the experiment which should begin soon.

Friday, July 19, 2002

I have been reading about clusters of F-Centers and other such defects in crystals. All seem to arise from heating and rapid cooling ("quenching") of the solid. They all have different bands, however, in the optical range; they should all, therefore, give the crystals color. The color effects of the centers should be very interesting.

Monday, July 22, 2002

I think that I have arrived at a topic for a project (again). I want to work with nonlinear crystals and photoelectric plates. My conjecture is that by increasing the frequency of light (by using the crystals to create harmonics), the photocell will be more efficient. This may be able to be applied to solar panels.

Tuesday, July 23, 2002

I spoke to Dr. Metcalf about my idea. He explained that it would be nearly impossible to concentrate sunlight nearly enough for SHG (second-harmonic generation) to be efficient, but he did run through some very interesting statistics with me, showing that solar energy should be the most readily available and efficient source available. I have, since then, done some research on-line about solar energy and agree with Dr. Metcalf that there must be some underlying reason that we do not understand for solar energy not being used commercially (perhaps, it is just oil companies' control over many aspects of the economy, but somebody should have done it by now if it were possible).

Thursday, July 25, 2002

Today we listened to the REU students give lectures on their respective projects. They were very well-presented and thought-provoking. The talks were a great mix of mathematical theory with empirical data. I am still looking for a project. Now, I am looking at F-Centers again. I do not quite know where I am going at this point.

Friday, July 26, 2002

We discussed with the group our ideas for project. (We determined that I need more direction--who would have thought?) I've been reading papers about F-Centers and their real-life applications. I E-Mailed the authors of a paper that claimed that they saw applications of F-Centers in quantum computing and lasers. Unfortunately, it seems like most practical uses involve more exotic crystals than NaCl.

Tuesday, July 30, 2002

Today, we presented our projects (in progress) to the Simons Fellows. The Brown Bag Lunch was in the Laser Teaching Center. I wrote a webpage about F-Centers and presented on them. I am also thinking about working strictly with Photostimulated Luminsence or Thermoluminescence after I talked to Dr. Noe today. He was telling me how I could study an interesting phenomenon but that I should keep it simple enough to be easy to work with (as opposed to working with harmful X-rays). I think the project loses its glamour if it is reduced to either PSL/TL, but I am going to look further into it.

Wednesday, July 31, 2002

I sent an E-Mail to Dr. Noe this afternoon regarding F-Center imaging. We spoke about the possibilities of doing an experiment with X-Rays and imaging with F-Centers in something like NaCl. While looking around on the Internet, we came across an abstract about a researcher who had used Al₂O₃:C as an effective method of detecting both high frequency radiation and optical light. Dr. Noe tried to contact him earlier, and Dr. Akselrod is supposed to call him back later in the day.

Thursday, August 1, 2002

Dr. Akselrod contacted Dr. Noe this morning. Dr. Akselrod explained his work with Al₂O₃:C and explained that there is some controversy as to the mechanism by which the defects are created in the crystal (called corundum). After doing some reasearch, I found that the defects may be caused by F⁺-Centers (a single electron occupying an oxygen vacancy), F-Centers (two electrons occupying an oxygen vacancy), V-Centers (oxygen ions between aluminum ions), or even holes as opposed to electrons. This may be a good topic for research. It seems that corundum has many different absorption spectra due to different phenomena, including photo-stimulated luminescence (PSL), thermoluminescence (TL), and others.

Friday, August 2, 2002

We went on a trip to Brookhaven National Laboratories today. We saw the STAR detector and Tandem Van Der Graaf generators. At the STAR dectector, Dr. Gene Van Buren spoke to us. He offered for us to E-Mail him with questions about the STAR. The whole apparatus is an awesome site, an amazing testament to the progress of modern science. After that, I checked my E-Mail and heard from Dr. Philip Allen who said that he would speak to me about my project. Lastly, Dr. Noe ordered filters for my experiment, and Dr. Akselrod is sending a sample.

Tuesday, August 6, 2002

Yesterday, I spoke to Dr. Phil Allen about self-trapped excitons. He explained to me the mechanism of self-trapped excitons in NaCl. Additionally, he told me something very interesting: There is no valid Newtonian model of covalent bonding. I was very surprised at this, but he offered very good proof. I am very thankful that he took the time to speak to me. Today, the sample of Al₂O₃ came in. I cannot work with it yet as the filters have not yet come, but I will begin soon. I began using the oscilliscope with the Nd:YAG laser to get a feel for how it works.

Wednesday, August 7, 2002

I began measurements of the Nd:YAG laser. I have measured the frequency of the pulses of the laser (about 130 microseconds) and gotten an idea for how to basically set-up my experiment. The filters still have not come, and we are working on finding someone to irradiate the sample. Tina Shih came today to speak to us about her work. Her work with femtosecond pulsed lasers produced powers of terawatts! After her talk, I began working on my abstract which is due on Friday. I have a preliminary abstract (here), but it is by no means final. Obviously, I still need to put the results of the experiment. Hopefully, we will find someone to irradiate the sample so I can begin. I do not need the filter just yet as I can use the oscilloscope to measure the light after the pulses of the Nd:YAG laser.

Thursday, August 8, 2002

I re-measured the frequency of the Nd:YAG laser after realizing that I had made a mistake with my prveious measurements. The frequency of the laser is about 7 kHz and the period about 140 microseconds. I started attempting to irradiate my source with UV light; I may soon find someone to do X-Ray irradiation. Lastly, I have been working on my abstract which is due tomorrow. (EEP!) Oh yeah; I almost forgot. We also took pictures of my shirts (which apparently everyone finds humorous), and they've been posted here.

Friday, August 9, 2002

I re-set-up my apparatus. I now have the laser shining downward into the photodetector. This has done several things. Now, I do not have to place the tweezers in the line of the laser and worry about the instability/inaccuracy of its position. I have also eliminated a lot of the attenuation due to the crystal. Initially, I had measured an 11-fold attenuation due to the crystal. Now, however, the crystal does not even decrease the intensity two-fold (about 1.78). The crystal now lies on top of the photodetector. In a few minutes, I am supposed to go find out about using the X-Ray machine. Hopefully, then, I will be able to begin my trials on Monday. Lastly, I have found a relatively unexplored topic in POSL (pulsed optically-stimulated luminescence). I read a paper about the relationship between intensity of luminescence and dose-rate with respect to TL (thermoluminescence); it was predicted that the same would hold true for OSL (optically-stimulated luminescence), but it has not been proven. I would like to, therefore, test this with POSL.

Tuesday, August 13, 2002

After irradiating the crystal for a total of 4.5 hours (2.5 hours today and 2 separate one-hour intervals previously), it seems that the photodiode will not detect the blue light. The filter has been used, with no success, and I attempted to see the light between the pulses of the Nd:YAG laser. Other exciting events of the day include killing the second laser battery as well as spending a half-hour trying to find the crystal that I lost in the dark (but I found it!). I have just been working on my presentation for tomorrow. I have to present to the other students at the center. I learned how to use Xfig, and I drew a circuit diagram of the photodiode and voltmeter/oscilloscope (here).

Wednesday, August 14, 2002

This morning, all of the high-school students in the physics department and Owen, who missed the REU talks, spoke about their projects. The projects outside of optics were pretty interesting. One student studied the orbit of a photon around a black hole. Apparently, I spoke quickly (which really is not news to me), but I presented my project with current status. I've been playing around with xfig, gimp, latex (and related programs), and a bunch of other programs to work on my presentation. Linux has a great host of applications geared towards scientific presentations. With xfig, there is a library that allowed me to make my circuit diagrams (here and here), though apparently, the older and newer versions are slightly different as I had to change the images when I tried to use them on my computer. I also played with writing equations in LaTeX, using latex2html to convert them to png's/gif's, then gimp to crop the images (here). (My presentation is here.) Lastly, Dr. Noe gave me a photomultiplier tube (PMT) today to improve the precision of my work. Hopefully, this will yield results indicating a 410 nm emission.

Thursday, August 15, 2002

RESULTS!! At long last! The PMT tube worked beautifully. I have great results, posted here, along with images and graphs and all sorts of other eye candy.

Monday, August 19, 2002

Thus far, the results seem kind of erratic. I have tried grouping some of my results and have pretty close to a good logarithmic relationship; however, the dose-rate experimentation is yielding confusing results. I am continuing to work on it and will post results soon.

Well, maybe not so soon, but as it seems, OSL output does depend upon dose-rate as Chen's paper suggests. It's all in my paper.