Abstract

We have improved the design of the rf sigma meter¹ to allow substantial narrowing of the linewidth of a commercial dye laser. The rf sigma meter design uses a dual Mach-Zehnder type interferometer with two optical frequencies produced from a single laser separated by some rf offset. Two photodiodes measure rf beat signals corresponding to the two different optical delay paths in the interferometer. The phase of these two photodiode outputs (modulo 2π) is linearly related to the reciprocal of the laser wavelength (modulo c/ΔL), known as sigma.²

© 1990 Optical Society of America