Portable I/sub 2/-stabilized Nd:YAG laser for international comparisons

Abstract

We have established a compact and transportable I 2 -stabilized Nd:YAG laser for international comparisons of laser frequency. The root Allan variance of the portable laser has reached 3 9 10 14 when the integration time is longer than 200 s. The results of an international comparison between the National Research Laboratory of Metrology (NRLM), Tsukuba, Japan and the JILA (formerly the Joint Institute for Laboratory Astrophysics), Boulder, CO, USA show that the frequency difference of the portable laser NRLM-Y1 and the JILA laser JILA-W ( NRLM-Y1JILA-W ) was 2 5 kHz, when the cold-finger temperatures of NRLM-Y1 and JILA-W were kept at 10 C and 15 C, respectively. The averaged frequency offset between two NRLM lasers ( NRLM-Y1 NRLM-Y2 ) was 1 1 kHz. A frequency variation of about 1.2 kHz was found for the frequency offset between two NRLM lasers, after NRLM-Y1 was taken for a round trip to Sydney for a comparison organized by the National Measurement Laboratory, (NML), Australia.Index Terms-International comparison, laser frequency stabilization, molecular iodine, Nd:YAG laser, optical frequency standard.

Comparison of independent optical frequency measurements using a portable iodine-stabilized nd:yag laser

“…In the case of iodine-stabilized He-Ne lasers, the frequency uncertainty of a group of lasers was obtained to be 12 kHz [11]. During previous international comparisons of iodine-stabilized Nd:YAG lasers [12], we also observed similar frequency offsets of a few kHz. From a metrological point of view, it is always important to confirm such differences, using a different method if possible.…”

“…One of the four NMIJ lasers (NMIJ-Y1) is a compact iodine-stabilized Nd:YAG laser which is suitable to be transported to other laboratories for international frequency comparisons [12]. This laser was transported to JILA in August 2001 for a round-trip intercomparison for the purpose of establishing a direct link of independent absolute optical frequency measurements in the two institutes.…”

An absolute optical frequency reference for space

“…Optical frequency references based on Doppler-free spectroscopy of molecular iodine near 532nm are a well-proven technology developed in several laboratories for many years, also in compact setups [5,6,7,8,9]. Development for applications in space is ongoing, resulting in compact and ruggedized setups [1,2,3,10,11].…”

A high-performance iodine-based frequency reference for space applications

“…They use either frequency modulation spectroscopy (FMS) [1], [2] or modulation transfer spectroscopy (MTS) [3], [4], [5], [6], and are also developed in compact setups [7], [8], [9], [10], [11]. State-ofthe-art setups reach noise levels of 2 · 10 −14 at an integration time of 1 s and below 3 · 10 −15 at integration times between 100 s and 1000 s using an 80 cm long iodine cell in singlepass configuration in combination with a frequency-doubled Nd:YAG laser [12], [13] (also cf.…”