Optical Frequency Synthesis From a Cryogenic Sapphire Oscillator Using a Fiber-Based Frequency Comb

• Published in: IEEE transactions on instrumentation and measurement 2007-04, Vol.56 (2), p.632-636, Article 632
• Main Authors: Watabe, K., Inaba, H., Okumura, K., Hong, F.-L., Hartnett, J.G., Locke, C.R., Santarelli, G., Yanagimachi, S., Minoshima, K., Ikegami, T., Onae, A., Ohshima, S., Matsumoto, H.
• Format: Article
• Language: English
• Subjects: Cryogenic sapphire resonator; Cryogenics; f requency synthesizer; Fiber lasers; fiber-based frequency comb; Frequency stability; Frequency synthesizers; Instrumentation; Laser mode locking; Laser stability; microwave oscillator; Microwave oscillators; Optical frequency; optical frequency synthesis; Optical resonators; Oscillations; Oscillators; Q factor; Rubidium; rubidium two-photon stabilized laser; Sapphire; Signal synthesis; Synthesis
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/TIM.2007.891073

The authors have demonstrated optical frequency synthesis using a fiber-based frequency comb system, referenced to an ultrastable microwave oscillator. The oscillator is based on a high Q-factor cryogenic sapphire resonator cooled with liquid helium. The 100-MHz signal synthesized from the 10.8-GHz oscillation frequency of the cryogenic sapphire oscillator (CSO) was used to stabilize the repetition frequency of the mode-locked fiber laser. When the synthesized optical frequency was compared with a rubidium two-photon stabilized laser at 778 nm, the measured fractional frequency stability was ~6 10 -14 tau -12 for the averaging times tau between 1 and 100 s, and the best frequency stability was 3.0 10 -15 for an averaging time of 1280 s