I'm trying to search for interesting articles that I can use as a start for my project. I want to start doing something as soon as possible, maybe even get a project proposal on friday. I'm using the search engines on the American journal of Physics site, as well as the more broad database search for the libraries at Stonybrook.
Tunneling leaky modes
Also known as tunneling modes or leaky modes, these optical fiber modes exist when a path of light does not totally internally reflect off the sides of the optical waveguide that it is partially encased in. Although these modes can exist for some time, they constantly scatter energy into the surrounding cladding and can cause other phenomena to occur. Leaky modes can leak into other optical fibers even with appropriate core-cladding interfaces and perfect optical fibers. Interestingly enough, geometric optics predict that the mode will be perfect, as it does exceed the critical angle. However, due to curvature of the core, energy is lost.
Blazed Diffraction Grating
Most diffraction gratings consist of lines that are parallel with each other, producing maximum that decrease as the absolute value of order increases. However, because the distance between diffraction maximum only depend on the net distance between diffraction gratings, its possible to have differently shaped diffraction gratings as long as the distance between the gratings remains the same. Using a special pattern that is similar to a sawthooth shape, its possbile to produce diffraction grating that accent a certain maximum. This can be applied to oblique lighting in microscopy by increasing the intensity of the offset maximum that replaces the 0th maximum. (?)
ATR Optical Modulator
An optical modulator is an apparatus that allows you to change the intensity of the intensity of a beam that goes through it. Although this concept is extremely simple, there many differnt ways to produce an optical modulator. For instance, you can make one using polarizers and mechanical changes. However, these modulaters have a poor range and poor response time. A good modulater would be able to change the intensity of a beam both ways very quickly without any overheating. There are also ways to do this using electrooptics and acustopics. you can take advantage of the evanscent wave and a mechanical micrometer to change the distance and the absorbance. The response of the optical modulater is not linear, however, and a certain conversion needs to be maintained, as well as a very fine adjustment of laser angle.
Bifringent prism polarizerUsing a Glan-Thomson prism its possible to seperate polarized light. It works by taking advantage of the bifringent properties of some materials to seperate the polarization. Then, by totally internally reflecting one of the beams away from the other, you can seperate the polarized light without having the prism absorb any light. This causes this type of polarizer to be more effective for high-energy lasers.
Optical fiber coupling in optical cables
In particular, I'm looking for a certain experiment that I remember reading about when I was doing research for my FTIR project. Due to the proximity of optical fibers in an optical cable, and the fact that optical fibers are emitting evanscent waves in all directions, even if sufficent cladding was placed between the optical fibers, there might possibly be the coupling of the various optical fibers. I'm wondering how to test this, as there are no square optic fibers, so the area for possible evanscent wave transmission will be a line where the two optic fibers touch. The advantage of attempting to test for FTIR through waveguides like this is that evanscent waves are produced along the entire waveguide, allowing for possibly better transmission. However, this also makes controlling how close the optical fibers are a challenge, as it would be easy to space out the mediums too far away, or too close so they optically bond and couple through conventional means. Wikipedia explicitly mentions single-mode fibers to be have this effect, but mention most of the evasncent wave is carried in the cladding.
Perhaps a dead end, but I'll look into it anyway.
I'm learning more about what exactly is modes in an optical fiber via exploration in boundary conditions, Maxwell's equations, Helmholtz equations, and other terms. I looked up the sizes of single mode optical fibers (3rd page)
Evanscent wave microscopy
We also had a meeting with Dr. Metcalf, Dr. Noe, and Dr. Cohen. I presented my FTIR project and metacalf gave me some things to think about. He asked me if I've ever heard of the setup where someone places an absorbing material in the path of the evanscent field. I said yes. He asked what is the smallest amount that is able to produce a noticable difference in intensity, which turns about to be a single atom. Using this technique, scientists can teep track of individual molecules, cells, and even interactions. (such as chemcial reactions, viral infenction) based on the frequencies of light emmitted.
here are some examples
There are plenty of interesting things that can be detected from particles absorbing the evanscent field.
Also, Carrie showed me an article about a evanscent wave coupled "whispering gallery" that she found while searching for her frequency doubling project. http://metrology.hut.fi/courses/s108-j/Nano2.pdf . From what I can tell, light is stuck inside a droplet, and flies around inside the droplet in a ring. I don't quite understand the connection that this has to an actual whispering gallery, but people use evanscent waves to pump energy into the waveguide. It has applications is microlasers and microdetectors.
However, there may be problems with getting the water droplet the correct size, as I think the beam path needs to be a intiger amount of wavelengths, or interference will occur. There also might be problems with the