Absolute-frequency measurements with a stabilized near-infrared optical frequency 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 microm. 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/f crossover transition in 87Rb at 780 nm, and the methane v2 + 2v3 R(8) line at 1315 nm.

Precision spectroscopy using a partially stabilized frequency comb

“…This makes it possible to lock the repetition rate by adjusting the pump power [17]. When the repetition rate is locked and one of the comb modes is offset-locked to the Rb diode laser, the frequency comb is fully stabilized [24].…”

“…Simply anchoring one of the comb modes and then measuring the repetition rate and beat notes gives us the necessary information to determine the frequencies of all the other comb modes [24]. As we show below, for integration times on the order of 10 s, the frequency uncertainty is in the 10 kHz range.…”

Phase-locked, erbium-fiber-laser-based frequency comb in the near infrared

“…11 In another experiment the output of a mode-locked Cr:forsterite laser was broadened to nearly a full octave and stabilized to a hydrogen maser and the Ca optical standard. 12 The diff iculty with all these approaches is the requirement of a separate optical reference. Self-referenced detection of f 0 obviates this requirement, 2,4 and in this work we demonstrate an infrared comb for which both the repetition rate and the CEO frequency are phase locked to a stable rf signal.…”

Noise Measurement and Reduction in Mode-Locked Lasers: Fundamentals for Low-Noise Optical Frequency Combs

“…Since the carrier-envelope offset frequency of the laser is mainly influenced by power fluctuation of the pump laser, in the early years, in Ti:Sapphire femtosecond laser OFCs, an acousto-optic modulator was applied to modulate the pump power. To this end, carrierenvelope offset frequency could be phase-locked to radiofrequency references [10,[107][108][109]. Later, in the fiber femtosecond laser OFCs, pump current modulation was also applied to stabilize the carrier-envelope phase of the emitted pulse train [86,110].…”