We report the current status of our ytterbium optical lattice clock at the NMIJ, AIST. After the first measurement of the
clock transition frequency and the estimation of the uncertainty, we have been improving our clock. For an increased
signal to noise ratio of the observed spectrum, we employed an atom number normalization scheme. We stabilized the
frequency of the lattice laser using a fiber-based optical frequency comb. We also stabilized the intensity of the lattice
We have developed a one-dimensional optical lattice clock with ultracold <sup>171</sup>Yb atoms. The absolute frequency of the
<sup>1</sup><i>S</i><sub>0</sub>(<i>F</i> = 1/2) - <sup>3</sup><i>P</i><sub>0</sub>(<i>F</i> = 1/2) clock transition in <sup>171</sup>Yb is determined to be 518 295 836 590 864(28) Hz with respect to the
SI second. Details of the experimental setups and atom trapping results are also described.
A phase-shifting interferometer (PSI) with equal phase steps, using a frequency-tunable diode laser and a Fabry-Perot cavity, is proposed for the Carre algorithm. The measurement accuracy of the Carre algorithm depends on the equality of the phase steps. Using the Fabry-Perot cavity as a highly stable optical frequency reference, a high degree of phase step equality can be realized in the PSI with an optical frequency shift. Our experimental scheme realizes an optical frequency step equality higher than 2.1×10<sup>-5</sup> and a measurement repeatability of λ/850.
An Rb-stabilized diode laser has been developed for use in a high-precision interferometer. The light source is a commercially available external-cavity tunable diode laser. The laser frequency is stabilized to a Doppler-free absorption line of Rb by the third-harmonic technique. The laser emits an output beam with a high power (more than 7 mW) and fast frequency modulation (10 kHz). The relative optical frequency uncertainty of 4.3×10–10 is achieved for a 0.01-s averaging time.
A simple rubidium stabilized diode laser has been developed for a gauge block interferometer. The laser light source is a commercially available external-cavity tunable diode laser (New Focus Inc.). Laser frequency stabilization is realized by the third-harmonic technique, where a fast frequency modulation (10 kHz) is applied on the current. The absolute laser frequency was calibrated by an absolute optical frequency measurement system using a femtosecond mode-locked laser. The relative uncertainty of the laser frequency reached 4.3×10<sup>-10</sup> for an averaging time of 0.01 s. The phase error in the interferometeric measurement due to the optical frequency modulation is theoretically indicated to be small enough to measure long gauge blocks of up to 1000 mm. Long gauge block measurement of up to 1000 mm was successfully demonstrated using the developed rubidium stabilized diode laser and the I<sub>2</sub>-stabilized offset locked He-Ne laser (633 nm).
An external cavity diode laser near 633 nm with Littrow configuration is constructed. With this laser and third order derivative technique, we have observed the iodine saturation absorption spectrum of P33 (6-3). The effect of different modulation width has been given.
In this paper, a preliminary result for an iodine frequency stabilized tunable diode lasers at 633 nm is reported. The frequency stability of the diode laser was 2 X 10<SUP>-11</SUP>, the tune ability was 10 nm and the line-width was 100 kHz. In addition, five groups of stronger hyperfine transitions of iodine molecule, which are available to be reference lines for diode laser frequency standard, beside the well-known transition R(127)11-5 at 633 nm region were observed by means of saturated absorption in the configuration of external iodine cell and their absolute frequencies were measured by a spectrum analyzer and a scanning Fabry-Perot cavity. The program for calculating the hyperfine structures and strength of transitions for rotational vibrational bands of iodine molecule was developed and the predictions for possible transitions around 633 nm including the transition strength are given.