title: Long-term optical phase locking between femtosecond Ti:sapphire and Cr:forsterite lasers.
abstract: Long-term optical phase-coherent two-color femtosecond pulses were generated by use of passively timing-synchronized Ti:sapphire and Cr:forsterite lasers. The relative carrier-envelope phase relation was fixed by an active feedback loop. The accumulated phase noise from 10 mHz to 1 MHz of the locked beat note was 0.43 rad, showing tight phase locking. The optical frequency fluctuation between two femtosecond combs was submillihertz, with a 1 s averaged counter measurement over 3400 s, leading to a long-term femtosecond frequency-comb connection.
authors.affiliation: National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568, Japan. y.kobayashi@aist.go.jp
authors.forename: Yohei
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Dai
authors.initials: D
authors.lastname: Yoshitomi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kakehata
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Takada
authors.forename: Kenji
authors.initials: K
authors.lastname: Torizuka