Subhertz-linewidth infrared frequency source with a long-term instability below 5 × 10−15

Raupach, S. M. F.; Legero, Thomas; Grebing, Christian; Hagemann, Ch.; Keßler, T.; Koczwara, A.; Lipphardt, B.; Misera, Mattias; Schnatz, H.; Grosche, G.; Sterr, U.

doi:10.1007/s00340-012-5280-6

Cited by 4 publications

(1 citation statement)

References 28 publications

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“…The laser linewidth is < 10 Hz and the relative frequency drift is <e-15/s [23]. On the long-term, the laser is frequency-stabilized to a hydrogen maser (HM INRIM ) by using a fiber frequency comb, as already proposed by other groups [24]; our setup is based on a digital phase-locked loop and uses a dead-time free phase/frequency counter to detect the beat note between the ultrastable laser and the closest comb mode; the counter is operated in the so-called lambda mode to sufficiently reject HM INRIM high-frequency noise. The beat note is then phase-stabilized via software to a fixed value by applying a correction to an acousto-optic modulator.…”

Section: The Experimentsmentioning

confidence: 98%

A coherent fiber link for very long baseline interferometry

Clivati

Costanzo

Frittelli

et al. 2015

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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We realize a coherent fiber link for application in very long baseline interferometry (VLBI) for radio astronomy and geodesy. A 550-km optical fiber connects the Italian National Metrological Institute (INRIM) to a radio telescope in Italy and is used for the primary Cs fountain clock stability and accuracy dissemination. We use an ultrastable laser frequency- referenced to the primary standard as a transfer oscillator; at the radio telescope, an RF signal is generated from the laser by using an optical frequency comb. This scheme now provides the traceability of the local maser to the SI second, realized by the Cs fountain at the 1.7 × 10(-16) accuracy. The fiber link never limits the experiment and is robust enough to sustain radio astronomical campaigns. This experiment opens the possibility of replacing the local hydrogen masers at the VLBI sites with optically-synthesized RF signals. This could improve VLBI resolution by providing more accurate and stable frequency references and, in perspective, by enabling common- clock VLBI based on a network of telescopes connected by fiber links.

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Section: The Experimentsmentioning

confidence: 98%

A coherent fiber link for very long baseline interferometry

Clivati

Costanzo

Frittelli

et al. 2015

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Long-term digital frequency-stabilized laser source for large-scale passive laser gyroscopes

Zhang

Liu

et al. 2020

Review of Scientific Instruments

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We report on the development of a digitally controlled long-term frequency stabilized ultrastable laser source, which serves as an injection laser to stabilize the perimeter of a 3 m × 3 m heterolithic passive resonant gyroscope. We operate the gyroscope at two different cavity modes to reduce back-scattering coupling disturbance for gyroscope locking. This scheme increases the requirement for the injection laser frequency stability since we are using the wavelength of the laser as the length standard for the heterolithic gyroscope structure. The laser source is digitally locked to an ultrastable high-finesse Fabry-Perot cavity and a femtosecond optical frequency comb referenced to an active hydrogen maser simultaneously. The fractional frequency stability of the locked laser is better than 1.2 × 10−14 for averaging times from 0.1 s to 10 000 s. The short-term frequency stability is limited by the stability of the Fabry-Perot cavity, and the long-term frequency stability is limited by the stability of the frequency comb. The digital locking system enables the laser to run autonomously for weeks and can quickly relock itself within seconds to ensure continuous running of the gyroscope. The digital frequency stabilization technique can also fulfill the requirements of space gravitational waves detection and the next generation space gravity recovery mission.

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