Optical–optical double-resonance dual-comb spectroscopy with pump-intensity modulation

We apply an intensity-modulation technique to dual-comb spectroscopy to improve its detection sensitivity. The scheme is demonstrated via Doppler-free optical–optical double-resonance spectroscopy of Rb by modulating the intensity of a pump laser with frequencies set at rates 3 times lower and 50,000 times higher than the difference in the repetition rates of the two frequency combs. The signal-to-noise ratios are enhanced by 3 and 6 times for slow and fast modulations, respectively, compared to those of conventional dual-comb spectroscopy without any intensity modulation. The technique is widely applicable to pump-probe spectroscopy with dual-comb spectroscopy and provides high detection sensitivity

Doppler-free dual-comb spectroscopy of Rb using optical-optical double resonance technique

We present a Doppler-free high-resolution dual-comb spectroscopy technique in which a dual-comb system is employed to perform optical-optical double-resonance (OODR) spectroscopy. In our experimental study, Doppler-free high-resolution and high-frequency-accuracy broadband measurements were realized using the proposed OODR dual-comb spectroscopic technique, which does not require high-power-per-mode frequency combs. We observed fully resolved hyperfine spectra of 5P3/2 - 4D5/2, 4D3/2 transitions of Rb at 1530 nm and precisely determined the absolute frequencies of the transitions, with an uncertainty of less than 1 MHz. The variations of the OODR spectral line shapes due to power broadening and alignment and the effects of polarization on the dual-comb OODR spectra were also analyzed. This study provides a widely applicable technique for Doppler-free dual-comb spectroscopy of various gaseous species

Comparison of Independent Optical Frequency Measurements Using a Portable Iodine-Stabilized Nd:YAG Laser

A comparison of two independent absolute optical frequency measurements has been carried out between the National Metrology Institute of Japan/National Institute of Advanced Industrial Science and Technology (NMIJ/AIST), Tsukuba, Japan and the JILA (formerly the Joint Institute for Laboratory Astrophysics), Boulder, CO, using a portable iodine-stabilized Nd:YAG laser. The agreement between the two absolute measurements is better than the measurement uncertainty of 6.7×10-13 that can be attributed to the reproducibility limitations of the portable laser. This comparison is used to confirm the measured absolute frequency of an iodine-stabilized Nd:YAG laser at NMIJ/AIST (Y3), which is reported to the Consultative Committee for Length (CCL) for the determination of the absolute frequency value of iodine-stabilized Nd:YAG lasers

Fiber-comb-stabilized light source at 556 nm for magneto-optical trapping of ytterbium

A frequency-stabilized light source emitting at 556 nm is realized by frequency-doubling a 1112-nm laser, which is phase-locked to a fiber-based optical frequency comb. The 1112-nm laser is either an ytterbium (Yb)-doped distributed feedback fiber laser or a master-slave laser system that uses an external cavity diode laser as a master laser. We have achieved the continuous frequency stabilization of the light source over a five-day period. With the light source, we have completed the second-stage magneto-optical trapping (MOT) of Yb atoms using the 1S0 - 3P1 intercombination transition. The temperature of the ultracold atoms in the MOT was 40 uK when measured using the time-of-flight method, and this is sufficient for loading the atoms into an optical lattice. The fiber-based frequency comb is shown to be a useful tool for controlling the laser frequency in cold-atom experiments.Comment: 18 pages, 6 figures, submitted to and accepted by J. Opt. Soc. Am. B (ID 125081