title: High-finesse cavity external optical feedback DFB laser with hertz relative linewidth.
abstract: We report hertz level relative linewidth distributed feedback diode lasers with external optical feedback from a high finesse F-P cavity, and demonstrate the efficient phase noise suppression and laser linewidth reduction of the optical feedback technique. The laser phase noise is dramatically suppressed throughout the measurement frequency range. Especially at the Fourier frequency of 17 kHz, approximately the linewidth of the F-P reference cavity, the laser phase noise is significantly suppressed by more than 92 dB. Above this Fourier frequency, the noise maintains a white phase noise plateau as low as -124.4 dBc/Hz. The laser's FWHM linewidth is reduced from 7 MHz to 4.4 Hz, and its instantaneous linewidth is 220 mHz in the Lorentzian fitting.
authors.affiliation: Division of Time and Frequency Metrology, National Institute of Metrology, 18 Beisanhuan East Road, Beijing 100013, China. zhaoyang@nim.ac.cn
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhao
authors.forename: Qiang
authors.initials: Q
authors.lastname: Wang
authors.forename: Fei
authors.initials: F
authors.lastname: Meng
authors.forename: Yige
authors.initials: Y
authors.lastname: Lin
authors.forename: Shaokai
authors.initials: S
authors.lastname: Wang
authors.forename: Ye
authors.initials: Y
authors.lastname: Li
authors.forename: Baike
authors.initials: B
authors.lastname: Lin
authors.forename: Shiying
authors.initials: S
authors.lastname: Cao
authors.forename: Jianping
authors.initials: J
authors.lastname: Cao
authors.forename: Zhanjun
authors.initials: Z
authors.lastname: Fang
authors.forename: Tianchu
authors.initials: T
authors.lastname: Li
authors.forename: Erjun
authors.initials: E
authors.lastname: Zang