Laser Collimation of a Chromium Beam

Figure 1. (left) Image of atom beam with collimation off; (right) Image of atom beam with collimation on.

Having a well-collimated beam of atoms is essential for our laser-focused atomic deposition experiments. In addition, collimated atom beams are generally useful for such applications as collision studies and atomic clocks.

We have made an in-depth study [EPG Pub# 669] of the collimation of a Cr beam using sub-Doppler transverse laser cooling. In addition to obtaining a very high degree of collimation (50% of the beam is contained within 0.16 mrad), we have studied the behavior of the collimation as a function of laser power and detuning. These studies have taken us into a regime where there is significant excited state population in the atoms, and the laser cooling has not reached full steady-state. This regime is outside the range of applicability of most laser-cooling theories, which assume steady-state, low-excitation conditions. Such data stimulates further theoretical research into the behavior of laser cooling and challenges a number of long-held beliefs on the subject.

Figure 2. Beam collimation vs. light force potential depth for several detunings.

Laser Collimation of A Chromium Beam

Jabez J. McClelland - NIST
Robert J. Celotta - NIST

Robert Scholten - University of Melbourne
Rajeev Gupta

Mark Levenson
Mark Vangel

Online: July 1999
Last Updated: February 2008

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