Research Journal

August 25th, 2005

Today I retook the data for temperatures 30°C to 25°C. Again I took pictures and tehn counted the pixels of each one. After putting them on the computer and getting the centroids, I converted them into wavelength changes and added them to the graph from the original data. Although the slope was alter slightly, the new data was relatively consistent with the other points.

August 24th, 2005

Today I looked at all the pictures taken yesterday and counted the pixels and their hieghts. Then I put all of this in a spreadsheet and got the centroid for them all. With this spreadsheet we were able to make a graph of the centroids vs. the temperature. We used the derivative formula to figure out the relationship between centroid and wavelength change and after I left Dr. Noe used that to change the graph from centroids to wavelength changes.

August 23rd, 2005

Today Dr. Noe told me that I wouldn't be able to get the change in wavelength from the way I took the data. He suggested that I take pictures of the peaks at different temperatures and find the centroid of them and compare the centroid to find out how much they moved. I started at 20°C and moved in small increments (between 1/2 to 1/3 of a degree) to 25°C and took pictures at each one while noting the voltage (which I then changed into temperature). Then I did the same thing starting at 30°C until 25°C. Although it is difficult to see a big change from one picture to another, the difference is very noticeable from the first to last picture.

Data Pictures

August 18th, 2005

This morning I changed the charts on the Project page into real charts. Thankfully I can copy the chart format off of other people's pages. Now they don't take up as much room and they are easier to read. I also added the data that I got yesterday; now the Data section doesn't look so empty.

August 17th, 2005

I continued getting data points today. I was skipping approx two degrees everytime I changed the temperature, because it was much easier to read the change when it was larger, but I doubled back to make sure that I landed on every temperature between 20 and 30°C, this is the range that the laser will go to. Now I have all 10 data points. Not 11 because I don't have 25° since I started there and I will measure the exact wavelength at that point in order to get the others. Once I get the wavelength at 25° (I can't use the other temperature I measured because it was at an arbitrary temperature) I will be able to work backwards to find the new wavelengths at the new temperatures.

August 16th, 2005

Today I wrote up my project so far online. It took me forever, mainly because I'm not to good at using the commands, but it's up to date.

My Project

August 15th, 2005

Today I took more data points. After taking two Dr. Noe pointed out that the volt meter I was using wasn't as accurate as others in the lab. After trying two other volt meters, which both read the same signal, is proved that the one I was using was showing a lower reading. I switched meters and then starting taking the data again. I adjusted the temperature back and forth between 25°C and 20°C and measured how far the spot moved.

August 12th, 2005

Today was the last day of Simons and of dorming. We had a laser show in the lab by setting up three different color lasers to bounce off of a speaker and onto the ceiling. As the music got faster the lasers moved around faster. We used liquid nitrogen to see (and take pictures) of the different lasers on the speaker. For lunch we ordered pizzas and eat them in the lab as we watched Death To Smoochy, very funny movie.

The electronic guys were able to fix the photo detector as well. Yesterday it stopped working and after taking it apart with Greg and Dr. Noe we thought it was because the voltage regulator stopped working. They were able to replace the regulators and now they're working again.

August 10th, 2005

Today I started taking data points by changing the temperature. After I had taken about five Dr. Noe pointed out that if I were to point the photo detector at the second order spot instead of the first the dispersion would be greater and the results would be more accurate. Because most calculus is lost on me Dr Noe helped me calculate the dispersion using derivatives and we found that dx / dλ = m / dcosθ Because of this if you increase 'm' the dispersion would increase. Increasing 'm' would also increase θ, therefore decreasing cosθ, which will also increase the dispersion. So tomorrow I'll change the photo detector to the second spot.

August 8th, 2005

Today I had a fight with the oscilloscope. I couldn't find the readings on it and couldn't figure out what was wrong. The majority of the day was spent fighting with it but eventually I found that if you shine the light onto a different area of the detector then the readings will be sharper. After playing around with that I found the ideal placement of the laser beam. Dr. Noe explained to me how if you can measure the separation of the pixels, which are static, then you can count the number of pixels moved when you change the temperature and calculate the movement using those measurements instead of remeasuring everytime.

August 5th, 2005

Today the REU students gave their talks because their program is over. In the morning we listened to Greg and Maaneli, and some others, and some people drifted back and forth between the lab and the talks all day. I began changing the temperature and observing the distance the spot moves. The readings were not consistant because when I changed the temperature 5 degrees in one direction it moved a different amount then when it was moved 5 degrees back to where it started.

August 4th, 2005

Today we had a tour of the LTC for the Simons kids. We started in the conference room explaining each of our projects and then moved into the center to show them our different setups. After a while they seemed to be watching more liquid nitrogen then optics because we were freezing different things and either trying to break it or watch it bounce.

August 3rd, 2005

I hooked up the ocsilloscope and the detector today. The detector is at the first shot away from the center and connects to the ocsilliscope that shows the position of the pixils. After a lot of trial and error with the ocsilloscope we were able to see the reading. At first the readings seemed to be moving in one direction regardless of which way the temperature was moved. We realized that the wires hanging from the detector were pulling it down so the detector was shifting on its own, which was creating the movement in one direction. After typing the wires in place on the table so that they couldn't pull, we were able to observe that when the temperature was changed the pixils could be seen moving in either direction and then measured by measuring how much you have to move the detector in order for the pixils to return to where they started before the temperature was changed.

July 29th, 2005

I finished the measurements with the violet laser on the graph paper today and then did the calculations to find "d" and then finally the wavelength of the violet laser. Then Dr. Cohen helped me open the laser and figure out how to change the temperature. Then we hooked it up to a volt meter and found out how to tell the temperature from the volt meter. After playing with it for a while (it was so much fun), I was able to learn more about how much to turn the screw for a certain change in temperature. Now I have find a way to get more resolution so that when I put the laser through the diffraction grading I can accuratly measure the minute change in wavelength as I change the temperature. Dr. Noe suggested reading about the Fabry-Perot Interferometer, which is something that Matt is working on and could create more resolution.

July 28th, 2005

Today I was using the HeNe laser on the table to find the "d" of the diffraction grating. After doing it twice I found that my answers were not close. Greg suggested that I put it all on something that would assure that they were parallel, so I put the laser, lens, diffraction grating and paper on something in the other room that allows the posts to be slid back the forth and allowed for very precise measurements. Once I put everything on that the measurements became much more constant. Then I used the HeNe laser and got an average measurement for "d" and then used that measurement and the violet laser to find its wavelength. I used a meter stick on the board to measure the spots, but when I was finished Dr. Noe pointed out that since the meter stick had a width, I was not getting an accurate measurement for "L". Back to the beginning, I attached graph paper to the board. Although it was more difficult to set up, because you had to make sure that the lines on the graph paper were exactly even with the lines of spots, at least the graph paper had a much smaller width. Since the violet laser was already on the set up I did those measurements first, although I couldn't do the calculations until I got "d" from the HeNe laser.

July 27th, 2005

Today there was a tour of the LTC for the REU students. We spent the morning cleaning up the lab. During the tour Greg and Maaneli explained their projects and then Dr. Noe showed them some other things, like the violet laser and the polarizers. After lunch Jose showed us around his lab. He explained about a lot of the big and expensive equipment he uses everyday, how it works, and what he uses it for. It was really interesting to see how his lab worked.

July 26th, 2005

Today we had our pizza lunch and a talk from Jose, who explained a computer program he had been working with. It's called FEM-LAB and he can use it to see displacement throughout a material. One example he showed us was heat dispersion. It showed different colors to signify the different amounts of dispersion. It was an interesting program that could take minutes to do what would otherwise take you much more time to figure out.

I continued to read about optical fibers. It's taking me a while to get through the chapter on it because I have to read very slowly to understand it all but I'm getting there. At the pizza lunch Dr. Metcalf said that someone in the astronomy department was going to create a spectrometer using an optical fiber and contect it to a telescope to be able to focus on the light coming from a single star. He said that the next time he spoke to him he would bring him by the LTC.

Dr. Noe and I were setting up the violet laser when we decided to see if we could see the spectra lines of a sudium light. The sodium spectrum includes two yellow lines extremely close together, often making it difficult to differenciate between the two. We put a slit infront of the light and stood across the room with a diffraction grading. After a while I still couldn't tell the two lines apart but Dr. Noe could. He took a picture and when it was brought up on the computer it was a lot easier to see. It was so cool being able to see the split between the two lines that you wouldn't normally be able to see.

Sodium Doublet

July 25th, 2005

Today I started learning about optical fibers. I read from a book that Dr. Noe had called Photonics and it explained all about different types of optical fibers from step-index to graded-index fibers. It also explained how the different types worked and at what angles the light needs to enter to be able to be guided through the core of the fiber. If I am going to be able to use an optical fiber when creating the spectrometer then I will have to position the fiber and the laser at the exact positions.

July 22th, 2005

Dr. Metcalf spoke to us today about electronics and diode lasers. He drew out an op-amp and explained the different paths and how to calculate the voltage in and out. I learned a lot about circuits that I had never understood. Then Dr. Metcalf spoke about diode lasers. He showed us some that he had and explained how small they were. We were looking at something very small but he explained that that was only the protection for the laser. The laser was to small to be seen, but protected by a lot of things.

July 20th, 2005

Today Dr. Noe talked to me about different ways I could take my project. He showed my different spectrometers and different things that could be done with them. He showed me how other students had created spectrometers and explained what they had used them for. One of the uses he explained was the ability to observe the change in wavelength when you changed the temperature. He told me that the violet laser that I've been working with has a feature that allows you to change the temperature, and explained how in a diode laser the relationship between temperature and wavelength is not steady, but instead can be graphed to look like steps. I really like this idea for a project but before I can do any of that I have to make a spectrometer first. Dr. Noe suggested a type of spectrometer that used a beam spliter, a lens, and a reflection grating to direct the light towards a detecter. With this I will be able detect the change in wavelength by how far the light moves on the detector.

July 19th, 2005

Dr.Metcalf talked to us today about clocks. He explained a great deal about how atomic clocks work and how we measure and define time. I tried to look up information about phototropic glasses, the ones that turn into sunglasses when you go outside, because that was one of the things brought up by Dr Noe and Dr Metcalf when discussing a project yesterday, I could only find a limited amount of info on how they work. Dr. Noe also pointed out then for my spectrometer I don't have to make the circle so tall, which would relieve the problem of it not staying in a perfect circle. Now I just have to fine a kind of platform that I can put it on so that it is at the same level as the laser, which I can't move any lower because of the post that it is on.

July 15th, 2005

I set up the circular paper with the laser and diffraction grating but was having trouble keeping it in the shape of a perfect circle. I kept the bottom in that shape by leaving the pie sheet in it but the top wasn't staying. I tried putting something under the pie sheet so that it could be more towards the top and hopefully hold the whole thing in place but I haven't found something yet that lets me do that while still being able to evenly rest the diffraction grating on the pie sheet.

I was looking up info on the Northern Lights. Besides really wanting to see them, they're really interesting to read about. As I'd been reading about spectrometry I was wondering what causes the different colors to be seen by different areas observing the Northern Lights. What I found was that the first color created is green, and that only takes 0.7 seconds, making green the most dominant color in most areas. Other colors take much more time, like red which takes about 100 seconds. Because of this the countries more north observe more green then other colors because they are more likely to see the immediate effects. It turns out that the difference in colors is only because of the different elements that can be found at different hieghts in the atmosphere. The atomic oxygen, which is mostly responsible for the greenish color, is the highest up, which is why green is created first. Lower down is the atmospheric nitrogen which creates blue and violet, followed by the nitrogen molecules that create red.

July 14th, 2005

Today I did a lot of arts and crafts with white paper, blue masking tape, and a pie crust dish when I made the paper into a large circle to use for the spectrometer. I had to make it tall enough so that the beam wouldn't be diffracted over it. I finally got the paper into a perfect, tall enough circle but if the paper is tall enough to have the spots projected on it then it is also too tall and blocks the laser from entering it. Now I have to cut a whole in the side of the paper to allow the laser to get in.

Nilus and Moon began to experiment with the laser and a fish bowl full of water. Eventually we were trying all different types of things with the water to see how the laser would react. We switched between red and green lasers, sometimes using both at once. We also added in Mango juice that Greg had brought from lunch. It made the water somewhat opaque, depending on how much was added. We observed what this did to the different lasers. It was fun just testing different things to see what would happen.

July 13th, 2005

Today we had our pizza lunch. There was a speaker who was from Germany and was doing work in x-rays. After lunch I tried to get more spots to measure from the diffraction grating. To make the spots closer together so that I'd have room to measure more of them I used a mirror to project them onto the wall on the table parallel to the laser. At first I couldn't understand why, when the diffraction grating was perpendicular between where the light was reflecting off the mirror and the center point on the wall, the points 1 and -1 weren't equally spaced from the center. Then Dr. Cohen pointed out the the mirror wasn't on a right angle. When I adjusted the mirror to that there was a right angle between the laser the mirror and the center dot, the points 1 and -1 became equal. Then I took that measurements of the points, going from -1 to 2 and approximated d, or the distance between the grooves. My results, while not identical to the results from the first test, were within the same range. I now have a better approximation of the measure of d.

July 12th,2005

I spent the morning reading up on spectrometers and how they work. This is because I'm going to try and make one with the laser and diffraction gratings I've been working with. There was a fire drill in the morning as well and we took that opportunity to use magnifying glasses to do an experiment on focal points. We used one magnifying glass to set fire to a black piece of paper. We then used a pair of reading glasses and found that they wouldn't converge to a single small point, the way the magnifying glass had. The reading glasses allowed us to see the image of the sky on the paper (this time white paper because it made it easier to see) including images of the clouds. After that we used two magnifying glasses to try and heat the paper faster. We found that the ideal placement of the magnifying glasses was right on top of each other. This cut the focal length in half and increased the intensity.

Because I didn't complete the measuring yesterday, I remeasured the diffraction of the violet beam with the diffraction grating. This time I placed the diffraction grating 11', or 3.3528 meters away from the wall the spots were being projected to. The first spot was 3' 7.53125", or 1.10569375 meters away from the center spot. After using the same equation from the tests with the 3d glasses, I found that the grooves in the diffraction grating were approx. 1.2899 micrometers apart. Unfortunately, this was not a very thorough test because I was only able to measure one spot. This was because, due to space limitations, I was unable to make more spots land on the flat wall, making them able to be measured consistently.

July 11th, 2005

Today we talked about the equation of a wave and how it can be used in a double slit experiment. We reviewed how to find the position of the diffraction spots in that experiment and then applied the equations to finding the intensity of the spots.We used the equation e^(i theta)= cos(theta)+ i sin (theta) for the line equations and then squared each line that makes a specific spot on the wall to get the intensity of it.

I started measuring with the violet laser and a different diffraction grating. I moved the grating close to the laser and projected the spots on the wall 10' 11.875" away.

July 8th, 2005

Today I went back to the 3d glasses but this time I used a violet laser. I went through the same process of measuring the dots and then, using the calculated distance between the grooves from the red laser, tried to calculate the wavelength of the violet laser. I got about 385 nm. Then I used the wavelength given on the laser, 404 nm and calculated the distance between the grooves again. This answer was within the same range as those from the red laser testing. However because I didn't measure as many points from the violet laser as I did from the red, the goodness/evilness was not as reliable, as it only had two points.

July 7th, 2005

Today I went back to the [x][x2] = k[x2] problem because Dr Metcalf said it wasn't possible to disprove it, because it was true. So I tried again to work it out but so far it still isn't working.

Dr Metcalf talked to us again, this time about waves. We discussed formulas for waves but mostly we discussed what a wave is and how it moves "information". Our conclusion was that we didn't know how it happens or even what moves.

I looked up diffraction gratings and the formulas for finding the distance between adjacent grooves on one, such as a cd. Then I used the 3d glasses and the red laser to see if I could measure the distance of the grooves in the glasses. I pointed the laser through the glasses and measured the distance between the dots that were projected on the wall. When I figured it all out my distance of grooves for each point, which ideally should have been the same, it had a goodness/evilness of 0.166 and the measure distance of grooves was about 0.00000481 meters, but unfortunatly I don't have the exact number to compare it to.

Goodness of Fit Graph

July 6th, 2005

Today we started by reviewing what we did yesterday. I attempted to continue the proof of [x][x2] = k[x2] but, with Dr. Noe's help, not only was it not proven, it was proven false. Through similar work, it was then realized that the division of Ey' by Ex' of light after it has been polarized is equal to the tangent of angle of the polarizer. After this Nilus and Moon showed us an experiment that they had done involving the distance a laser spot moved on the wall and the amount of times the screw on the mirror reflecting the laser to the wall was turned, in order to determine how many threads per inch were on the screw. This brought us to the tangent of if you move the mirror an angle of (x), then the increase of the angle reflected would be (2x).

July 5th, 2005

Today Dr. Metcalf spoke to us again, this time about matrices. He began by discussing things that commute. He decided that all numbers commute, but not all operations do. He explained this using different examples, such as walking out of a room and closing the door. You would not be able to do this in the reverse order. We added and multiplied the matrix and then he explained how you can use them to solve problems of polarized light. After that we all attempted to derive a matrix that can be used for a polarizer placed in any direction. After much writing and erasing, which continued over lunch, it was finally found. Then I tried to prove one of our homework problems from Dr. Metcalf, which was that if you pass light through one polarizer, and then pass it through another, it would be the same as if you had only passed it through the second polarizer and multiplied it by a constant. [x][x2] = k[x2] I'm still trying to prove that one.

After many calculations with numbers Dr. Noe showed us different tools and things that are used in the lab. He showed us different tools used to mount mirrors and balance lasers. He explained the different types of screws and screwdrivers used and the differences between the english and the metric tools. Then he showed us demonstrations with the laser, such as tightening a screw on the mirror reflecting a laser, and watching its reflection on the wall shift in different directions.

June 30th, 2005

Yay, I learned how to write on the computer! Well, somewhat, I'm still learning. Anyway, our morning consisted of a whole bunch of numbers. Dr. Metcalf talked to us about complex numbers, a subject that apparently can be used to explain a lot of other types of math, like trig. We went over everything from the basic of complex numbers, including the question 'What is a number?', to the more complex, including how to find the multiple roots of a number using a unit circle. Another topic related to complex numbers is that of polarizers. Dr. Metcalf showed us examples of different polarizers. He put them on top of each other and we discused the different angles of the two that would allow, or not allow, light to pass through it. Then he added a third. We saw and discussed the different angles that would allow the light to pass through these three polarizers. Then he explained how these angles could be determined also through the use of complex numbers. We continued to discuss the different purposes of complex numbers and how they can be used to simplify some equations, such as trig problems.

Lindsey Garay
Summer 2005
Laser Teaching Center