Observation of beating between blue and green light
Z. Y. Ou, Edward C. Gage, Brian E. Magill, L. Mandeļ · Optics Communications · 1988
We have observed beating between the blue (488 nm) and the green (514.5 nm) lines of an argon ion laser by use of a fourth order interference technique. The method involves the use of a Mach-Zehnder interferometer with photoelectric coincidence detection. The observed (approximately) 30 fs period of the beat note is far shorter than the time resolution of the detectors.