Physics is Cool

Note: I posted a bunch of old notes that were originally on Facebook. So if you ever care to go back and check them out, they're in the process of appearing in the archives.

Most of you guys reading this know that I study physics. I just finished school 3 weeks ago and now do research at Mines. I decided I would write a post about the physics that I study because I think it's pretty cool stuff.

If you were to ask me what kind of physics I study, I would say, Integrated Optics. This means that I study really simple optical devices that are built into chips on a really small scale. There's a billion different optical devices that can be built and they have all kinds of applications. I'll just choose one of the devices our group works on to give you an idea of the stuff I work on. I've probably worked on upwards of 10 different devices though.

Optical devices manipulate light in different ways for some application. The physics I do is extremely applied, so I don't do that crazy, revolutionary physics that you hear about in the news. Some things that you can do with light are emitting, detecting, filtering, guiding, measure polarization, and more.

Some familiar examples of these processes: (Keep in mind that when I say light, I mean Electromagnetic Radiation which includes, X-rays, UV, Visible, Infrared, Radio Waves, etc.)

• Emitting: Light Bulbs, LEDs, Stars, Antennae, Cell Phones, etc.
• Detecting: Eyes, Cameras, Antennae, Cell Phones, X-rays at the dentist, Radios
• Filtering: 3D glasses (one eye mostly sees blue and the other eye mostly sees red)
• Guiding: Fiber Optics, Those cool lamps that send light through fibers
• Measure Polarization: Polarized Sunglasses, Camera Polarizer

So, our research group tries to do all these effects to build really small devices on micro chips (small=100nm-100microns). 70 microns is somewhere near the diameter of human hair.

One really good example of why these need to be so small is the Polarimeter project we're working on. A polarimeter can measure the polarization of light. You can have linear polarization, circular polarization, or elliptical polarization and the polarimeter can measure any of those and detect how elliptical the polarization is. If you've ever worn polarized sunglasses at a lake or river, then you know that the polarization of the light reflected off a surface tells you about the surface. Reflected light on the smooth, horizontal surface of water, is polarized in one direction and if you're wearing polarized sunglasses, standing straight up, you don't see the reflected light and you can see underwater better. If you rotate your head then you can start to see the reflected light and if you adjust your head so the reflected light is very low, then you have adjusted your polarizers so they are perpendicular to the surface. So by finding this spot, it gives you information about the angle of the water surface. The idea behind the polarimeter is to be able to do a similar measurement, giving the U.S. Army better information about the surface they are looking at.

So the Army wants this to be really small so they can make an entire array of polarimeters so each pixel in the digital camera can measure polarization. I don't know how many pixels they're planning on, but if we can make the polarimeter the size of the pixels on your computer then you can have an entire screen with really good resolution, where each pixel can measure polarization giving you a ton of new information that a regular old camera could not give you. That's why the device needs to be really small, so you can stack a bunch of them in an array to have many pixels.

The idea for a polarimeter is to filter out different kinds of polarizations of light in different ways to be able to measure what that polarization is. This actually isn't a project that I'm really working on, so I don't know that much about it. But it uses gratings etched in materials like Silicon, Silicon Dioxide, Silicon Nitride, Aluminum, etc. to couple different polarizations into a waveguide and sent out for detection. There are different shapes of gratings that filter out different polarizations so we can measure any polarization state. And all of this is built on a very small chip and I think the footprint for this entire device is under 100microns.

You now have some idea of the kind of things I work with. It's really interesting stuff and it's pretty exciting to be working on such advanced technologies. I'm very fortunate to get to work in this area of research because it is incredibly valuable.

This may have been a very boring post for some of you, but I don't care.

Song of the Day: Belated Promise Ring by Iron and Wine