Abstract
Laser with high spectral purity plays a crucial role in high-precision optical metrology and coherent communication. Thanks to the rapid development of laser frequency stabilization, the laser phase noise can be remarkably compensated, allowing its ultra-narrow linewidth subject to mostly quantum limit. Nevertheless, the accurate characterization of phase noise statistics and its linewidth of a highly coherent laser remains ambiguous and challenging. Here, we present an approach capable of revealing delay-time-resolved phase noise statistics of a coherent laser based on coherent optical time domain reflectometry (COTDR), in which distributed Rayleigh scattering along a delay fiber essentially allows a time-of-flight mapping of a heterodyne beating signal associated with delay-time-dependent phase information from a single laser source. Ultimately, this novel technique facilitates precise measurement of ultra-narrow laser linewidth by exploiting its delay-time-resolved phase jitter statistics of random fiber laser with pump lasers of various linewidths, confirmed with the analytical modeling and numerical simulations.
Highlights
Laser with high spectral purity plays a crucial role in high-precision optical metrology and coherent communication
Coherent laser sources with highly purity spectrum are at the heart of highprecision measuring science, including laser interferometer gravitational-wave observatory (LIGO)[1], optical atomic clock[2] and high-resolution spectroscopy[3]
We demonstrate a novel technique to reveal the phase jitter dynamics of a coherent laser by employing a coherent optical time domain reflectometry (COTDR), for the first time to the best of our knowledge, in which distributed Rayleigh scattering along a segment of delay fibre technically introducing a time-of-flight for the heterodyne beating note carrying a delay-time-resolved phase information of the laser under test
Summary
Laser with high spectral purity plays a crucial role in high-precision optical metrology and coherent communication. By launching a number of optical pulses and repeating Ns times beating note traces acquisition, the variance of the absolute phase jitter |Δτφ| at the delay time of τz could be statistically calculated as, σ′τ2|τ=τz = ∑jj==N1 s(|Δτφj| − 〈|Δτφj|〉 )2|τ=τz.
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