title: Long-term maintenance of the carrier-envelope phase coherence of a femtosecond laser.
abstract: The long-term carrier-envelope phase (CEP) coherence of a femtosecond laser with same pulse-to-pulse CEP value, obtained using the direct locking method, is demonstrated by employing a quasi-common-path interferometer (QPI). For the evaluation of the CEP stability, the phase noise properties of a femtosecond laser with the CEP stabilized using a QPI are compared with those obtained using a Mach-Zehnder f-2f interferometer, for which the phase power spectral density and the Allan deviation were calculated from the beat signals of the interferometers. With the improved CEP stability, the long-term CEP coherent signal with an accumulated phase noise well below 1 radian can be maintained for more than 56 hours, i.e., the CEP coherence is preserved without a phase cycle slip for more than 1.6 × 10(13) pulses at a repetition rate of 80 MHz. The relative stability is also estimated to be approximately 1.4 × 10(-22) at a central wavelength of 790 nm.
authors.affiliation: Dept of Physics and Coherent X-ray research Center, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea.
authors.forename: Eok Bong
authors.initials: EB
authors.lastname: Kim
authors.forename: Jae-Hwan
authors.initials: JH
authors.lastname: Lee
authors.forename: Won-Kyu
authors.initials: WK
authors.lastname: Lee
authors.forename: Tran Trung
authors.initials: TT
authors.lastname: Luu
authors.forename: Chang Hee
authors.initials: CH
authors.lastname: Nam
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005246:Feedback; D007368:Interferometry / Q000295:instrumentation*; D007834:Lasers