Absolute-frequency measurements with a stabilized near-infrared opticalfrequency comb from a Cr:forsterite laser

Abstract

A frequency comb is generated with a chromium-doped forsterite femtosecond laser, spectrally broadened in a dispersion-shifted highly nonlinear fiber, and stabilized. The resultant evenly spaced comb of frequencies ranges from 1.1 to beyond 1.8,um. The frequency comb was referenced simultaneously to the National Institute of Standards and Technology's optical frequency standard based on neutral calcium and to a hydrogen maser that is calibrated by a cesium atomic fountain clock. With this comb we measured two frequency references in the telecommunications band: one half of the frequency of the d/{ crossover transition in 87Rb at 780 nm, and the methane 7)2 + 27)3 R(8) line at 1315 nm.