Alright, I don't know why I am even bothering to post on my blog now that I've let it lay dormant for over 6 months. Crazy. If anybody was meandering over here to laugh and pity my rantings and ravings I am sure they have not done so for a long time. Nobody will read this besides my wife probably (that's right Alex, I just called you a nobody ;) ).


Anyway, with this post I am going to do something that I have meant to do with this blog since its inception: use it to share at least a little of my research. For those who don't know I am working on a Ph.D. dissertation in Physics. My project consist of building a matter-wave interferometer based on calcium, and hopefully will expand to a dual-species apparatus using both calcium and strontium. Let me explain.


Interferometers do exactly what the name implies: they interfere things. Specifically, they interfere waves. At its most basic this is no different then taking a smooth body of water, creating a wave, and then watching as the wave bounces off of a wall back on itself with the troughs and peaks adding and subtracting as they pass through each other. To interfere waves in the best way, you need what is called a coherent source. This means that all the waves of a certain frequency are in phase with each other over a long enough distance, i.e. all the troughs and peaks at a certain frequency look like a sine wave when put together. In the case of light, normal ambient light (whether natural or electric) is not coherent, while laser light is coherent. While you can in fact make a simple enough interferometer with white decoherent light, an interferometer based on laser light becomes a powerful tool for precision metrology (the science of measureing things precisely). In fact, laser interferometers comprise some of the best detectors being used and built to look for gravity waves.



Now, you may recall from some introductory science class Einstein, the photo-electic effect, and the "wave particle duality of light". Meaning that in some instances we can observe light behaving like a particle while in others light seems to behave like a wave. Some time later a bright young man named de Broglie realized that maybe mass or matter has a duality as well. Maybe sometimes atoms act like waves while most of the time acting like a particle. It turns out that not only was he right, but if you can produce atoms with wave functions that are coherent (like the photons in laser light) then you can mix them in an interferometer. That is my project: to create a device which coherently interferes the waves associated with calcium atoms and then use it to measure and test cool stuff. Despite the extreme difficulty of this project and the frustration of experimental physics, I love doing this. Along the way I have developed the world's quietest, most diverse, diode laser current driver as well as a small catalog of lab standard scientific instruments that we use to run our experiments. And that is just the tip of the ice berg.


After years of building and developing I am actually getting close to turning the damn thing on. Bellow are some pictures I took of the inside of the vacuum chamber as I was assembling the interferometer. I'll try to explain to you what happens as best I can.

This picture shows where light first enters the vacuum chamber. The laser light that we use to manipulate the calcium's wave function gets focused by a lens down to the pinhole on the left of the picture. This has the effect of making the light look nice spatially which makes a difference to the atoms. The second optic recolimates the light after the pinhole and a mirror then sends the laser over to the rest of the interferometer.


The pinhole and lens setup is on the far right of this picture. The light goes from there over to the mirror at the top left of the picture, which sends it a beamsplitter (that big rectangular block of glass just below the mirror). At the bottom righ of the picture are two skimmers. An oven that you can't see off the right side of the picture heats up calcium which starts to flow toward the left of the picture. The skimmers catch a part of the calcium and collimate it into a well defined beam of atoms about 1 mm in diameter. The big things in the lower left are the first of several large coils of wire which create a magnetic field to help align the electronic states of our atoms.
Here you can see the main body of the interferometer. The light is split up by the beamsplitter and then directed through the interferometer by precision prisms so that it crosses the atom beam 4 times. The atoms pass through the center of the magnetic coils. I worked extremely hard so that all the laser beams lies within the same plane to a fraction of a millimeter and the prisms helped me to ensure that the beams cross the atoms at right angles to within 50 micro radians. The lens at the lower left marks the end of the interferometer. At this point blue laser light is passed into the chamber to make the calcium atoms flouresce. The lens collimates that flourescence and sends it through a window in the top of the chamber. This constitutes the signal from the interferometer.

A closeup of the lens that captures the blue flourescence from the atoms. The chamber is now sealed and under vacuum (the pressure inside the chamber is currently hovering around 8x10^-8 Torr... no, there is not enough air for you to breath in there). I am currently working on the laser systems that run the interferometer and will update you on them shortly I hope.