Collisional Dephasing and the Reduction of Laser Phase-Noise to Amplitude-Noise Conversion in a Resonant Atomic Vapor
Abstract
When resonant laser light passes through a vapor, the laser's intrinsic phase fluctuations induce random variations in the atomic coherence, which, in turn, give rise to fluctuations in the medium's absorption cross section. Hence, laser phase modulation noise (PM) is converted to transmitted laser intensity (i.e., amplitude) modulation noise (AM). Here, we consider the influence of collisional dephasing on the PM-to-AM conversion process. Specifically, we measure the relative intensity noise of a diode laser beam, resonant with the Rb D1 transition at 794.7 nm, after it has passed through a Rb(sup 87)/N2 vapor as a function of nitrogen number density. Our results demonstrate that when collisional dephasing is very rapid, the spectral density of cross-section fluctuations is reduced, so that there is a significant decrease in the efficiency of PM-to-AM conversion at low Fourier frequencies. These results imply that, in general, when laser PM-to-AM conversion is the dominant noise process, pressure broadening can actually increase spectroscopic sensitivity.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 10, 2002
- Accession Number
- ADA404534
Entities
People
- J. G. Coffer
- James C. Camparo
- Miles Anderson
Organizations
- The Aerospace Corporation