Circumvention of noise contributions in fiber laser based frequency combs

TOPTICA Photonics AG, Gräfelfing, Bavaria, Germany
Optics Express (Impact Factor: 3.49). 08/2005; 13(15):5662-8. DOI: 10.1364/OPEX.13.005662
Source: PubMed


We investigate the performance of an Er:fiber laser based femtosecond frequency comb for precision metrological applications. Instead of an active stabilization of the comb, the fluctuations of the carrier-envelope offset phase, the repetition phase, and the phase of the beat from a comb line with an optical reference are synchronously detected. We show that these fluctuations can be effectively eliminated by exploiting their known correlation. In our experimental scheme, we utilize two identically constructed frequency combs for the measurement of the fluctuations, rejecting the influence of a shared optical reference. From measuring a white frequency noise level, we demonstrate that a fractional frequency instability better than 1.4 x 10(-14) for 1 s averaging time can be achieved in frequency metrology applications using the Er:fiber based frequency comb.

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Available from: Armin Zach, Jun 15, 2015
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    • "This exploits the correlations in phase that exist between the radio frequency (RF) beat note of an optical reference with a comb line, and both the comb repetition rate and CEO frequency. Previous studies of comb stability and systematic uncertainty using the transfer oscillator scheme have been presented [4] [10] [22] [23]; however the work reported here significantly improves upon previously reported systematic uncertainties. "
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    ABSTRACT: Results are presented from a series of comparisons between two independent femtosecond frequency comb systems at NPL, which were carried out in order to assess their systematic uncertainty. Simultaneous measurements with the two systems demonstrate agreement at the level of 5 x $10^{-18}$ when measuring an optical frequency against a common microwave reference. When simultaneously measuring the ratio of two optical frequencies, agreement at the 3 x $10^{-21}$ level is observed. The results represent the highest reported level of agreement to date between Ti:sapphire and Er-doped femtosecond combs. The limitations of the combs when operating in these two different manners are discussed, including traceability to the SI second, which can be achieved with an uncertainty below 1 x $10^{-16}$. The technical details presented underpin recent absolute frequency measurements of the $^{88}$Sr$^+$ and $^{171}$Yb$^+$ optical clock transitions at NPL, as well as a frequency ratio measurement between the two optical clock transitions in $^{171}$Yb$^+$.
    Metrologia 08/2014; 52(1). DOI:10.1088/0026-1394/52/1/62 · 2.04 Impact Factor
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    • "1(a)]. Here, we are interested in the scaling of the phase noise away from the optical lock point at 657 nm (that is, from an imposed fixed point Benkler et al. (2005) of the comb). At the lock point, we measure ∆f 0 within a small bandwidth about 657 nm and then compare it with ∆f 0 measured at another spectral region [Fig. "
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    ABSTRACT: Stabilized optical frequency combs (OFC) can have remarkable levels of coherence across their broad spectral bandwidth. We study the scaling of the optical noise across hundreds of nanometers of optical spectra. We measure the residual phase noise between two OFC's (having offset frequencies $f^{(1)}_0 $ and $f^{(2)}_0$) referenced to a common cavity-stabilized narrow linewidth CW laser. Their relative offset frequency $ \Delta f_0 = f^{(2)}_0 - f^{(1)}_0 $, which appears across their entire spectra, provides a convenient measure of the phase noise. By comparing $\Delta f_0$ at different spectral regions, we demonstrate that the observed scaling of the residual phase noise is in very good agreement with the noise predicted from the standard frequency comb equation.
    Optics Communications 01/2014; 320. DOI:10.1016/j.optcom.2014.01.030 · 1.45 Impact Factor
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    • "Control of femtosecond frequency comb is also a key technology for coherent addition of independent lasers. Recently details of comb noise were studied, and narrow comb lines were realized by improving the feedback bandwidth in Er-fiber laser oscillators [1] [2] [3] [4]. However, the origin of relatively broad linewidth of carrier-envelope offset frequency (f ceo ) in a fiber laser is not fully understood yet because of complicated correlation of mode spacing and f ceo move in a cavity. "
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    ABSTRACT: Dynamics of laser mode of femtosecond Er-fiber lasers were investigated by using a beat signal between two mode-locked lasers. The beat linewidth was controlled to 8 mHz.
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