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We report a novel technique for highly stable transfer of a frequency comb over long optical fiber link. Phase fluctuation along the fiber link, which is mainly induced by physical vibration and temperature fluctuations, is automatically compensated by the self-adapted wavelength shifting. Without phase-locking loop or any tunable parts, stable radio frequency is transferred over 2 km fiber link, with time jitter suppression ratio larger than 110. [ABSTRACT FROM PUBLISHER]

Absolute measurements of spectral lines of Ar+ ions using collinear and anticollinear geometries were performed. To provide a precise reference for the laser wavelength, iodine saturation spectroscopy was applied. The precision of this reference is effected by observing the beat node between the spectroscopy laser and the corresponding mode of a femtosecond laser frequency comb. Laser-induced fluorescence allowed to perform precision frequency measurements of an Ar+ transition in collinear and anticollinear geometries simultaneously; then an exact relativistic formula for the absolute transition frequency V0 = VcVa was used. In this geometry the influence of ion source instabilities due to pressure and anode voltage fluctuations was minimized. The result is v0 = 485,573,619.7(3) MHz, which corresponds to Δv/v = 6*10-10. This represents an improvement of two orders of magnitude over the previous NIST published value. [ABSTRACT FROM AUTHOR]

A highly efficient technique to generate broadband cascaded four-wave mixing (FWM) products is proposed. It consists of launching two or three strong pump waves near the zero-dispersion wavelength of very short (of order of few meters) optical fibers. Depending on the application, the fiber dispersion and nonlinear properties, as well as the pump wavelengths should be properly chosen in order to obtain the required bandwidth, uniformity and separation of the frequency comb. Experimental results present bandwidths of 300nm, spaced by 6.5nm, and more than 200 FWM products spanning over 170nm at ITU-T grid specification. [ABSTRACT FROM AUTHOR]

Ultracold atoms and molecules provide ideal stages for precision tests of fundamental physics. With microkelvin neutral strontium atoms confined in an optical lattice, we have achieved a fractional resolution of 4 × 10-15 on the 1S0 - 3P0 doubly-forbidden 87Sr clock transition at 698 nm. The overall systematic uncertainty of the clock is evaluated below the 10-15 level. The ultrahigh spectral resolution permits resolving the nuclear spin states of the clock transition at small magnetic fields, leading to measurements of the 3P0 magnetic moment and metastable lifetime. In addition, photoassociation spectroscopy performed on the narrow 1S0 - 3P1 transition of 88Sr shows promise for efficient optical tuning of the ground state scattering length and production of ultracold ground-state molecules. Lattice-confined Sr2 molecules are suitable for constraining the time-variation of electron-proton mass ratio. In a separate experiment, cold, ground state polar molecules produced from Stark decelerators have enabled an order of magnitude improvement in measurement precision of ground-state, Λ-doublet microwave transitions in the OH molecule. Comparing the laboratory results to those from OH megamasers in interstellar space will allow a sensitivity of 10-6 for measuring the potential time variation of the fundamental fine structure constant Δα/α over 1010 years. These results have also led to improved understandings in the molecular structure. The study of the low magnetic field behavior of OH in its 2Π3/2 ro-vibronic ground state precisely determines a differential Landé g-factor between opposite parity components of the Λ-doublet. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

We demonstrated two femtosecond Ti:sapphire comb laser pumped by a continuous-wave 532 nm light which is generated from a frequency doubling 1064 nm ytterbium fiber laser. To make the system small, we develop HS-CTSDL being the frequency standard. [ABSTRACT FROM PUBLISHER]

Generation of wideband frequency combs using single continuous-wave laser seed is described. The efficiency and noise suppression is achieved by specialized parametric mixer design. Performance limits of new parametric mixer technology are discussed. [ABSTRACT FROM PUBLISHER]

In the present experiment the 5S-5D two-photon transitions in 85Rb and 87Rb atoms as a result of the interaction of the femtosecond frequency comb with atomic levels of both rubidium isotopes are investigated. The main problem in studying of two-photon transitions is in optimization of the excitation efficiency of the desired state. There are two general cases: those transition with an intermediate resonance those in which the pulse spectrum is far detuned from an intermediate resonance. In order to investigate the dependence of the two-photon fluorescence signal as a result of interaction of the frequency comb with perturbed energy-level pattern an external magnetic field was applied. [ABSTRACT FROM AUTHOR]

This paper describes the ongoing work on measuring the variable spacing between two electrodes in the next-generation NIST calculable capacitor. The spacing measurement is based on a high finesse Fabry-Perot interferometer system where displacements are inferred from optical frequency measurements. Using a frequency comb referenced to an atomic clock as an optical frequency standard, we achieve a fractional uncertainty of δν/ν ∼ 2·10−11 at 2 seconds. This corresponds to a stabilization of the spacing at the picometer level. [ABSTRACT FROM PUBLISHER]