Abstract
In this work we describe the spectral purity transfer between a 1156 nm ultrastable laser and a 1542 nm diode laser by means of an Er:fiber multibranch comb. By using both the master laser light at 1156 nm and its second-harmonic at 578 nm, together with the 1542 nm slave laser, we investigate the residual noise between the main comb output, the octave-spanning output, and a wavelength conversion module including non-linear fibers, second-harmonic generation crystal and amplifiers. With an ultimate stability of the system at the level of at 1 s and accuracy of , this configuration can sustain spectral transfer at the level required by the contemporary optical clocks with a simple and robust setup.
Highlights
In the last two decades, optical combs became a fundamental tool in experimental physics, finding applications beyond optical [1, 2] and microwave [3] frequency metrology
Spectral transfer to a telecom wavelength will enable us to disseminate the frequency of the Yb standard to a number of research facilities, using the phase-stabilized ∼2000 km optical fiber backbone we developed in Italy [24]
We implemented the transfer oscillator technique using an erbium-doped fiber (Er):fiber multibranch frequency comb. Having available both the master laser light at 1156 nm and its 578 nm second harmonic, we characterized the spectral transfer without using a second reference comb
Summary
In the last two decades, optical combs became a fundamental tool in experimental physics, finding applications beyond optical [1, 2] and microwave [3] frequency metrology. The optical comb enables such performances to be copied to any laser in the optical domain, with a simplification of the experimental setup This is especially relevant when several ultrastable lasers at different wavelengths are needed, where a single ultrastable cavity has to be realized. Spectral transfer to a telecom wavelength will enable us to disseminate the frequency of the Yb standard to a number of research facilities, using the phase-stabilized ∼2000 km optical fiber backbone we developed in Italy [24] This setup will be used to generate the clock laser for the Sr optical clock under development in our laboratories [25]. By using both the fundamental and frequency-doubled master laser we characterized the spectral transfer and the contribution of the separate comb branches without the need of a second, independent system This measurement approach, which uses a single comb to study the spectral purity transfer, is different from that presented in previous works. Multibranch configuration still offers adequate performances with a simple and robust system
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