An ultra-low frequency noise agile laser

We report on a fiber-stabilized agile laser with ultra-low frequency noise. The frequency noise power spectral density (PSD) is comparable to the one of an ultra-stable cavity stabilized laser at Fourier frequencies higher than 30 Hz. When it is chirped at a constant rate of ~ 40 MHz/s, the max non-linearity frequency error is about 50 Hz peak to peak over more than 600 MHz tuning range. When the laser is chirped, the Rayleigh backscattering (RBS) is a significant frequency noise source related to fiber length, chirping rate and the power imbalance of the interferometer arms. We analyze both theoretically and experimentally this effect and put forward the noise reduction techniques.