Superradiant Laser BuiltCategory: Science & Technology
Posted: April 13, 2012 10:29AM
Lasers are used for a variety of things, from pointing to diagrams to accurately measuring time, but each use requires a special kind of laser. A laser pointer does not need to be the best of quality for what it does, but the lasers used in atomic clocks and other high-precision measurements need to be the very best. These are situations where the vibrations from a car driving outside the building can disrupt the measurement. Fortunately researchers at JILA, a joint institute of NIST and the University of Colorado Boulder, have created a superradiant laser which has the highest stability of any laser.
Modern laboratory lasers work by shining a light into a cloud of atoms between two mirrors. As the light bounces between the two mirrors, it hits and stimulates the atoms to release another photon, thereby increasing the amount of light in the cavity. Some of this light gets through the mirrors to produce the beam we have all seen. Those mirrors are a problem for the laser though. The smallest of vibrations can cause the mirrors to shift a very small amount, but still enough to throw off the frequency of the laser light. The new superradiant laser however does not require the mirrors as much as a regular laser.
In a traditional laser, the cloud of atoms all act separately, but in this superradiant laser, the atoms act as though they are one. Atoms release photons when they drop in energy levels, so in a regular laser, one atom releases one photon. In the superradiant laser the atoms will all drop together, so 10,000 photons can be released all at once. This means far fewer photons are needed to create the laser, so they do not need to be bouncing off the mirrors. With less dependence on the vibrating mirrors, the superradiant laser is only 1/10,000 as sensitive as a traditional laser.
The next step is for researchers to find what other atoms they can make a superradiant laser from, because the rubidium atoms used are not the best of all situations.