A laser with a coherence length the size of the solar system

by Prof. Murray J. Holland (JILA and University of Colorado at Boulder (Boulder, Co, USA))

Friday 12 Jul 2013, 11:00 → 12:00 Europe/Rome

250 (INFN edificio C)

I will present a proposal for a new approach to lasers that promises to produce light of unprecedented spectral purity and coherence, some two orders of magnitude better than any system available today. The idea is based on superradiant emission, where an ensemble of atoms with an extremely narrow atomic transition forms a macroscopic dipole, and radiates collectively. This is quite unlike a typical laser where atoms act independently. The resulting light source is expected to have a spectral linewidth of just a few millihertz and could lead to more accurate and stable atomic clocks. Atomic clocks based on optical reference transitions have improved tremendously in recent years, giving clocks that tick $10^{15}$ times per second, and can have a fractional stability exceeding $10^{16}$. This new sharper light source aims to push the frontier even further, so that fundamental tests of physics, such as the time variation of constants and tests of gravity, might be possible.