Direct Link between Microwave and Optical Frequencies with a 300 THz Femtosecond Laser Comb

Abstract

We demonstrate a great simplification in the long-standing problem of measuring optical frequencies in terms of the cesium primary standard. An air-silica microstructure optical fiber broadens the frequency comb of a femtosecond laser to span the optical octave from 1064 to 532 nm, enabling us to measure the 282 THz frequency of an iodine-stabilized Nd:YAG laser directly in terms of the microwave frequency that controls the comb spacing. Additional measurements of established optical frequencies at 633 and 778 nm using the same femtosecond comb confirm the accepted uncertainties for these standards.

Absolute frequency determination of molecular transition in the Doppler regime at kHz level of accuracy

“…An 88 Sr optical atomic lattice clock [12,13] served as a frequency reference in most of the performed measurements. The spectrometer was optically linked to the optical atomic clock via the OFC [14,15]. Such a reference has significant advantages over typically used radio frequency (RF) references in terms of stability and accuracy.…”

Femtosecond Optical Frequency Combs

“…In fact generating ω CE became possible only in 1999 by beating different harmonics (3.5th and 4th) of different components of the comb [12]. As this first demonstration involved considerable effort to generate the required harmonics, the task simplified dramatically with the availability of octave spanning frequency combs [13][14][15].…”

Atom interferometers and optical atomic clocks: New quantum sensors for fundamental physics experiments in space

“…The measurement of optical frequencies has recently been made practical by the development of the femtosecond-laser frequency-combs [5,6]. Combined with narrow linewidth lasers, this has made possible the first generation of optical atomic frequency standards and clocks, based on cold trapped neutral atoms, such as Sr or Yb, and ions, such as Sr + , Yb + , Al + , Hg + .…”