Optical clockwork with an offset-free difference-frequency comb: accuracy of sum- and difference-frequency generation.

We demonstrate a simple optical clockwork mechanism based on the broadened frequency comb of a femtosecond laser and on difference-frequency generation (DFG) in a nonlinear crystal. The DFG comb possesses a vanishing carrier envelope offset frequency that permits the construction of a simple and thus potentially more stable optical clockwork. In addition it offers the possibility of extending the frequency comb into the infrared spectral region. The overall accuracy and stability of the DFG comb relative to the initial frequency comb were measured to be 6.6 x 10(-21) and 10(-18) tau(-1), respectively, where tau is the averaging time in seconds. Assuming that sum- and difference-frequency generation are independent processes, our measurements suggest a <10(-20) accuracy for them.

[1]  H R Telle,et al.  Absolute frequency measurement of the 435.5-nm (171)Yb+-clock transition with a Kerr-lens mode-locked femtosecond laser. , 2001, Optics letters.

[2]  A. Pugh.  The art of electronics. 2nd edn: By Paul Horowitz and Winfield Hill. Pp. 1125. Cambridge University Presss. 1989. £29.95, US$49.50 , 1990 .

[3]  A. Stentz,et al.  Visible continuum generation in air–silica microstructure optical fibers with anomalous dispersion at 800 nm , 2000 .

[4]  E. A. Curtis,et al.  An Optical Clock Based on a Single Trapped 199Hg+ Ion , 2001, Science.

[5]  Theodor W. Hänsch,et al.  Measuring the frequency of light with mode-locked lasers , 1999 .

[6]  Alfred Leitenstorfer,et al.  Amplified femtosecond pulses from an Er:fiber system: Nonlinear pulse shortening and selfreferencing detection of the carrier-envelope phase evolution. , 2003, Optics express.

[7]  Reichert,et al.  Phase coherent vacuum-ultraviolet to radio frequency comparison with a mode-locked laser , 2000, Physical review letters.

[8]  David J Jones,et al.  Phase stabilization of an octave-spanning Ti:sapphire laser. , 2003, Optics letters.

[9]  Lennart Robertsson,et al.  Femtosecond-laser-based optical clockwork with instability, 2002, Optics letters.

[10]  Takao Fuji,et al.  Controlling the carrier-envelope phase of ultrashort light pulses with optical parametric amplifiers. , 2002, Physical review letters.

[11]  Harald Schnatz,et al.  Ultraprecise measurement of optical frequency ratios. , 2002, Physical review letters.

[12]  Knight,et al.  Optical frequency synthesizer for precision spectroscopy , 2000, Physical review letters.

[13]  H. Haus,et al.  Group velocity of solitons. , 2001, Optics letters.

[14]  Hall,et al.  Direct link between microwave and optical frequencies with a 300 THz femtosecond laser comb , 2000, Physical review letters.

[15]  D. M. Atkin,et al.  All-silica single-mode optical fiber with photonic crystal cladding. , 1996, Optics letters.

[16]  D. Meschede,et al.  How accurate is optical second-harmonic generation? , 1995, Optics letters.