Abstract
We report on a fiber-stabilized agile laser with ultra-low frequency noise. The frequency noise power spectral density is comparable to that of an ultra-stable cavity stabilized laser at Fourier frequencies higher than 30 Hz. When it is chirped at a constant rate of approximately 40 MHz/s, the max non-linearity frequency error is about 50 Hz peak-to-peak over more than 600 MHz tuning range. The Rayleigh backscattering is found to be a significant frequency noise source dependent on fiber length, chirping rate and the power imbalance of the interferometer arms. We analyze this effect both theoretically and experimentally and put forward techniques to reduce this noise contribution.
Highlights
Simultaneous achievement of low frequency noise operation and precise, fast and linear tunability is a challenge for laser technology
We analyze the noise sources and fundamental limits of the method, in particular the impact of the Rayleigh backscattering (RBS), which constitutes the present limit of our system
Control of the laser frequency is realized by using the piezoelectric transducer (PZT) stretcher port of the commercial fiber laser for slow corrections on large range, and AOM0 for fast corrections
Summary
Simultaneous achievement of low frequency noise operation and precise, fast and linear tunability is a challenge for laser technology. Lasers with sub-hertz line-width and fractional frequency instability around 10−15 for 0.1 s to 10 s averaging time are currently realized by locking onto an ultra-stable Fabry-Perot cavity using the Pound-Drever-Hall method [8,9,10,11]. This method requires fine alignment of free space optical components, tight polarization adjustment and spatial mode matching. We analyze the noise sources and fundamental limits of the method, in particular the impact of the Rayleigh backscattering (RBS), which constitutes the present limit of our system
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