Abstract
We demonstrate a laser frequency stabilization technique for laser cooling of potassium atoms, based on saturated absorption spectroscopy in the C-Band optical telecommunication window, using ro-vibrational transitions of the acetylene molecule (12C2H2). We identified and characterized several molecular lines, which allow to address each of the potassium D2 (767 nm) and D1 (770 nm) cooling transitions, thanks to a high-power second harmonic generation (SHG) stage. We successfully used this laser system to cool the 41K isotope of potassium in a 2D-3D Magneto-Optical Traps setup.
Highlights
For laser cooling and trapping experiments, frequency stabilization of the laser system must be ensured, with a stability typically less than the natural linewidth of the transition. This is achieved via sub-Doppler saturated absorption spectroscopy, usually employing the same atomic transition used for laser cooling [1,2]
Solutions relying on telecom technologies and second harmonic generation (SHG) have been successfully tested in the case of rubidium, starting from a laser source at 1560 nm [9,10,11]
It is composed of two main parts: the first part is used to stabilize the frequency of a ultra-narrow line (UNL) laser diode (‘master’) on a Doppler-free signal using a acetylene molecular transition in a low-pressure spectroscopy cell
Summary
For laser cooling and trapping experiments, frequency stabilization of the laser system must be ensured, with a stability typically less than the natural linewidth of the transition (a few MHz for alkali atoms). A similar technique is implemented in our setup using a diode laser in the telecom domain, followed by amplification and SHG in a periodically-poled lithium niobate (PPLN) crystal This allows us to obtain a high laser power at the desired wavelength, close to the D2 cooling transitions at 766.701 nm [12]. Ultracold atom laser systems usually require complex amplitude and frequency light control sequences [13] To achieve such versatility, two SHG systems are usually developed: a powerful one is dedicated to the atomic laser cooling, and allows dynamic control of the cooling parameters, while a weaker, stationary one is devoted to the frequency locking only [8].
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