The BEC and its Implications for Laser Technology

[NeverAmI]

Bored and thought I would post this that I was researching. Some of you may have heard about the Bose Einstein Condensate before. Essentially it slows down a group of atoms, held in an electromagnetic 'dish,' to almost a standstill in a supercooled environment.

[ame="http://www.youtube.com/watch?v=fnqAwtorUTE"]YouTube- As cold as it gets[/ame]

There are primarily two different lasers that utilize the BEC, at least that I know of.

One is a Gamma Ray Laser which still uses traditional photon technology but the photons are created from particle/antiparticle annihilation, in this case being positronium consisting of a positron and an electron.

http://www.sciencedaily.com/releases/2010/05/100501013620.htm

"The eventual production of a positronium condensate could help us understand why the universe is made of matter and not antimatter or just pure energy," Cassidy said. "It could also one day help us measure the gravitational interaction of antimatter with matter. At present, nobody knows for sure if antimatter falls up or down."

The other is an atomic laser that uses the actual atoms to form a beam rather than photons, it is REALLY interesting to hear how much more gravity affects an atomic beam vs the traditional photon beam.

http://cua.mit.edu/ketterle_group/projects_1997/atomlaser_97/atomlaser_comm.html

Differences between an atom laser and an optical laser

• Photons can be created, but not atoms. The number of atoms in an atom laser is not amplified. What is amplified is the number of atoms in the ground state, while the number of atoms in other states decreases.
• Atoms interact with each other - that creates additional spreading of the output beam. Unlike light, a matter wave cannot travel far through air.
• Atoms are massive particles. They are therefore accelerated by gravity. A matter wave beam will fall like a beam of ordinary atoms.
• A Bose condensates occupies the lowest mode (ground state) of the system, whereas lasers usually operate on very high modes of the laser resonator.
• A Bose condensed system is in thermal equilibrium and characterized by extremely low temperature. In contrast, the optical laser operates in a non-equilibrium situation which can be characterized by a negative temperature (which means "hotter" than infinite temperature!). There is never any population inversion in evaporative cooling or Bose condensation.

I think one of the neatest things is that, in order to create a BEC regular photon lasers are used. The photon wave bursts help to slow the atoms down in the condensate.

 

[stopharian]

When I was in college, my desk in my architectural studio looked directly across a courtyard and onto the tower in the physics building where they created the first Bose Einstein Condensate. I always took a little pleasure in knowing that I was probably sitting there when they cranked that mother up and created what was at the time the coldest place in the world and perhaps even in the universe.

Man did they have fantastic dumpster diving. They had a machine shop right there that built all the pieces for those machines and all the architecture students would be down in the dumpster at night pulling out fascinating custom made pieces from these one of a kind machines. We probably all have cancer now.

 

[NeverAmI]

When I was in college, my desk in my architectural studio looked directly across a courtyard and onto the tower in the physics building where they created the first Bose Einstein Condensate. I always took a little pleasure in knowing that I was probably sitting there when they cranked that mother up and created what was at the time the coldest place in the world and perhaps even in the universe.

Wow that is so cool!

 

[whytiger]

I'm writing a book about vortex filaments. Some of it is on rotating BECs. Essentially, unlike in ordinary fluids where vortices can rotate at any speed, a vortex in a BEC can only rotate at speeds that are multiples of Plank's constant. So we have, in fact, quantum behavior that is visible to the naked eye (or at least a good microscope ). Here's a nice picture of quantized vortices in a rotating BEC:

And one with views from the top and sides:

 

[NeverAmI]

WOW that is really fascinating!

What type of atom was that observed with, rubidium? Do you know if it has been observed with any other type of atom?

 

[whytiger]

These are sodium atoms I think. This is a useful link.