Atomic-Resolution Frequency Modulation

Toschihico Arimitsu, Masashi Ban, Fumiaki Shibata

Shunsuke Nakanishi, H. Ariki, Hiroshi Itoh +1 more

Frequency-modulation (FM) spectroscopy has been performed on the D(2) transitions of rubidium atoms with an AlGaAs diode laser at 780 nm. Doppler-broadened hyperfine-structure transitions of (85)Rb and (87)Rb were resolved with no residual amplitude-modulation-induced background signal by modulating the injection current of the laser diode at a low frequency (20-50 MHz) compared with the Doppler width. To obtain Doppler-free spectra, we combined FM spectroscopy with saturation spectroscopy. The results show that the FM spectroscopy technique is sensitive and should be useful for high-resolution spectroscopy, although the resolution was instrument limited and unusual double peaks were observed.

Lirong Wang, Jie Ma, Yanting Zhao +2 more

In the present paper, ultracold cesium atoms were obtained in magnetic optical trap using the laser cooling technology. The number of ultracold atoms is 10(7). The temperature of ultracold atoms is about 200 μK and the diameter of the ultracold atoms cloud is about 400 μm. The ultracold cesium molecules of excited states were formed using the photoassociation of ultracold atoms. The resolution of vib-rotational spectrum was studied under different scan rates of photossociation laser in the experiment. The resolution of vib-rotational spectrum becomes high when the scan rate of photossociation laser becomes slow. The cold atoms fluorescence was obtained using the high sensitive avalanche photo detector and the high resolution vib-rotational spectrum of ultracold cesium molecule in its first excited state of with dissociation limit long range state was obtained. The ultracold ground molecule was formed by controlled Raman photoassociation and the photoassociation laser must be locked to atom-molecular hyperfine transitions. The ultracold atoms photoassociation spectrum was modulated using ultra-low frequency. The first-order differential signal was optimized by changing modulation amplitude and modulation frequency. It provides a feedback signal to correct error of the laser. The laser frequency satisfies experimental requirement to form ultracold ground molecules using the controlled Raman photoassociation. This work is important for studies of ultracold atoms and molecules in confined space.

Masashi Ban, Toshihico Arimitsu

Philip H. Jones, H. E. Saunders-Singer, S. Bergamini +1 more

We have investigated the use of a moving or “Doppler” mirror to probe laser cooled atoms. The device uses the Doppler shift induced on reflection at a moving surface to modulate the frequency of a probing laser beam, with a modulation bandwidth and frequency resolution sufficient for the narrow spectral features typically encountered. We anticipate that the device could be a simple and cost-effective alternative to acousto-optic modulators for cold atom spectroscopy, and demonstrate its usefulness by performing stimulated optical Compton scattering on an optical molasses.

Chang-Hee Lee