LASER MATERIAL (SPECTROSCOPY).
Abstract
MEASUREMENT OF LASER SHORT-TERM FREQUENCY FLUCTUATIONS: Detailed measurements have been made for the first time of the short-term frequency or phase fluctuations in stable single-frequency helium-neon lasers. These frequency fluctuations are the principal cause of the finite spectral width of laser oscillators. The fluctuations were measured by examining the beat notes between two essentially free-running lasers operating in a quiet stable environment. The average frequency of the beat was kept at a nominal 30 MHz center frequency by a slow AFC loop which did not affect the faster short-term fluctuations. Separate measurements were made of (a) the power spectral density of the 30 MHz beat note; (b) the mean-square accumulated phase jitter in the beat during intervals of varying length; and (c) the spectral density of the low-frequency output from a discriminator cented at 30 MHz. Results of the three separate measurement techniques were in good agreement, indicating a gaussian power spectral density for the laser oscillators, a mean-square phase jitter increasing quadratically with time, and a discriminator output spectrum varying as 1/f squared. The standard deviation of the gaussian laser spectrum was found to be sigma sub f is approx equal to 13 kHz, or a spectral purity better than three in 10 to the eleventh power. A full report on these measurements will appear in the IEEE Journal of Quantum Electronics in early 1967. Nd: YAG LASER SPECTRAL STUDIES: During the final period the amplitude fluctuations of the Nd:YAG laser were studied. These amplitude fluctuations, which were small compared to the steady-state level of the output power, were found to be of the form of damped sinusoids.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1967
- Accession Number
- AD0815954
Entities
People
- Anthony E. Siegman
Organizations
- Stanford University