Using diode lasers for atomic physics

Carl Wieman

There has been considerable activity recently on cooling and trapping atoms using laser light. This work raises expectations that laser manipulation of atoms will be an important new tool for atomic physics. However, up to now, almost all the work has been on sodium atoms using light from dye lasers. The expense and complication of a narrowband dye laser system is a considerable limitation on the possible uses of this tool. In response to this we have been exploring the use of inexpensive diode lasers for the manipulation of atoms. We have found that diode lasers work very well for this purpose and even have some advantages over dye lasers in addition to cost and ease of use. We previously reported using light from diode lasers to stop a beam of atomic cesium. Here we discuss our more recent work using diode lasers to produce extremely cold cesium vapor via optical molasses cooling and the demonstration of a new type of optical trap. This is a purely optical spontaneous force trap which uses spatially inhomogeneous optical pumping to circumvent the optical Earnshaw theorem.

Richard N. Watts, Carl Wieman

Zijie Liu, Xiaolei Guan, Xiaomin Qin +7 more

The study of atomic physics has been greatly influenced by the development of high-stability diode lasers whose output corresponds to the atomic transition. Recently, an atomic filter laser “Faraday laser” shines on stage, owing to its great robustness to the fluctuation of the diode parameters and potentially higher tolerance to vibration. However, cost reduction and portability require the Faraday laser to have a more compact structure. Here, we report on the development of a promising atomic filter laser—a “Voigt laser”—using a Voigt anomalous dispersion optical filter (VADOF) as the frequency-selective element, which has a structural advantage in miniaturization. The influencing factors toward the VADOF are investigated in detail to produce a parameter set for the best performance of a Voigt laser. In this case, the Voigt laser has great robustness to the fluctuation in the diode current and temperature, where the wavelength fluctuation is ±0.5 pm with the variation of the diode parameters (diode current: 73–150 mA and diode temperature: 12–30 °C). In addition, the wavelength of the Voigt laser fluctuates about ± 0.5 pm for 48-h free-running operation and shows excellent reproducibility without manual adjustment. The laser system developed here provides a stable and reliable laser source for substantially improving existing technologies such as the atomic clock, electromagnetically induced transparency, and laser cooling of atoms.

Tilman Esslinger, Immanuel Bloch

A. Ruschhaupt, Juan Gonzalo Muga

We present a generalized two-level scheme for an ``atom diode,'' namely, a laser device that lets a two-level ground-state atom pass in one direction, say from left to right, but not in the opposite direction. The laser field is composed of two lateral state-selective mirror regions and a central pumping region. We demonstrate the robustness of the scheme and propose a physical realization. It is shown that the inclusion of a counterintuitive laser field blocking the excited atoms on the left side of the device is essential for a perfect diode effect. The reason for this, the diodic behavior, and the robustness may be understood with an adiabatic approximation. The conditions to break down the approximation, which imply also the diode failure, are analyzed.

Richard N. Watts, Carl Wieman