Signs of atoms!
One of the steps to making a Bose-Einstein condensate (BEC) is getting the atoms in the appropriate part of the chamber (the science cell) and taking a picture of them to see if they are there, how many, and how cold they are. After that, the process has to be optimised, where we try to get as many atoms in there as possible and also do some tricks to get the atoms as cold as possible before evaporation (the final step to BEC).
Today we reached the first milestone of that - we took some pictures of rubidium-87 atoms in the science cell! It's a shitty, unfocused shadow image. The imaging laser has a crappy linewidth* and the stabilising electronics are minimally functional, BUT we saw something :-D
The big circle is the imaging laser beam. The bright blob on the left is a cloud of atoms! This is done by "simply" shining some light on the atoms and looking for a shadow where some light is being absorbed by the atoms. We take one image with atoms and one of another pulse of light without any atoms and subtract them, because otherwise the shadow is too faint to see. Ignore the plots on the side and bottom. Probably not so exciting for most of you, but super exciting for me!
* Most people think of lasers as having just one wavelength, but in reality, lasers emit a small range of wavelengths (usually quite a bit less than a nanometer). This range of wavelengths is called the linewidth. When we are manipulating atoms with laser light, the linewidth needs to be as narrow as possible because we are trying to address energy levels in the atoms that correspond to a very specific wavelength. If our linewidth is too broad, only some of the laser light is interacting with the atoms in the intended manner.
Today we reached the first milestone of that - we took some pictures of rubidium-87 atoms in the science cell! It's a shitty, unfocused shadow image. The imaging laser has a crappy linewidth* and the stabilising electronics are minimally functional, BUT we saw something :-D
The big circle is the imaging laser beam. The bright blob on the left is a cloud of atoms! This is done by "simply" shining some light on the atoms and looking for a shadow where some light is being absorbed by the atoms. We take one image with atoms and one of another pulse of light without any atoms and subtract them, because otherwise the shadow is too faint to see. Ignore the plots on the side and bottom. Probably not so exciting for most of you, but super exciting for me!
* Most people think of lasers as having just one wavelength, but in reality, lasers emit a small range of wavelengths (usually quite a bit less than a nanometer). This range of wavelengths is called the linewidth. When we are manipulating atoms with laser light, the linewidth needs to be as narrow as possible because we are trying to address energy levels in the atoms that correspond to a very specific wavelength. If our linewidth is too broad, only some of the laser light is interacting with the atoms in the intended manner.