Frequency reproducibility of an iodine-stabilized Nd:YAG laser at 532 nm

We have established an ensemble of iodine-stabilized Nd:YAG lasers to verify the frequency reproducibility of the laser. The stability, repeatability and several systematic shifts of the laser frequency are investigated by heterodyne beating of the lasers. The frequency dispersion of the ensemble of lasers is evaluated to be 0.5 kHz (corresponding to a relative frequency uncertainty of 8 × 10−13). The absolute frequency of one of the lasers (named as Y3) is measured to be 563 260 223 507 897(58) Hz using a femtosecond optical comb, when the laser was stabilized on the a10 component of the R(56)32-0 transition of 127I2 for a cold-finger temperature of −10 °C. This group of lasers, including one transportable laser, forms an ensemble of optical frequency standards, which serves for many applications such as international comparisons, optical frequency measurements, frequency calibration services and high-resolution spectroscopy.