Enhancement of the Optical Quality of Microtraps for Single Atoms with HASO4 First Olga Nabirotchkine Imagine Optic, 18 rue Charles de Gaulle, 91400 Orsay, France [email protected] Introduction Over the past years, an interest in advanced optical trapping of atoms has arisen. From simple initial configurations such as crossed optical dipole traps, researchers’ needs have evolved towards more complex light fields such as two-dimensional arrays of microtraps. These configurations open appealing applications in quantum-information processing and quantum simulation for instance. In this report, we present the results of an experiment performed at Institut d’Optique Graduate School (CNRS, France), demonstrating the successful trapping of cold 87Rb atoms in reconfigurable 2D arrays of microtraps obtained with a spatial light modulator (SLM). The use of a HASO4 First, the wavefront sensor from Imagine Optic, proved to be essential to achieve high-quality optical microtraps. Enhancement of Optical Quality of Microtraps for Single Atoms with HASO4 First Application note imagine-optic.com July 2014 – Property of Imagine Optic

Experimental Setup Figure 1 shows the experimental setup used to generate an array of microtraps for single-atom trapping. To do so, a collimated trapping beam at 850 nm is sent on a SLM, which imprints a phase onto it. Then, this beam is focused in the focal plane of a highnumerical-aperture aspheric lens. A cloud of cold atoms is produced at 50 µK with a magneto-optical trap (MOT) to load the microtraps. The atoms are detected thanks to the measurement of their fluorescence at 780 nm. The trapping beam is transmitted via a second aspheric lens to a diagnostic CCD camera to image the trap array,...

Improvement of the trap arrays thanks to HASO4 First The HASO4 First is a wavefront sensor based on patented Shack-Hartmann technology, which performs absolute achromatic measurement of both phase and intensity independently, simultaneously and in real-time. The accuracy of the measurement is /150. Figure 3 (a) shows the wavefront measured after the vacuum chamber, for a flat phase applied to the SLM. One sees that the wavefront aberrations are 0.155  RMS. The SLM present in the setup can be used, in addition to the phase imprinting for the generation of trap arrays, to compensate for the aberrations...

These improvements need to be confirmed at the level of the atoms by measuring the essential characteristics of the trap, i.e. its depth and its frequency. Figure 6 shows the results of such a measurement, giving an improvement of 50 % in the trap depth and 30% for the trapping frequency. Acknowledgements We would like to thank Thierry Lahaye and Henning Labuhn from the Laboratoire Charles Fabry of the Institut d’Optique Graduate School (Palaiseau, France) for allowing us to present the results of their experiments. Literature F. Nogrette, H. Labuhn, S. Ravets, D. Barredo, L. Béguin, A. Vernier,...