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In the first part of the work presented, Rydberg atoms (diameter about 500nm) are trapped in one-dimensional optical lattices of 1064nm laser light. Amplitude modulation is used to drive microwave transitions between Rydberg levels. The quasi-free character of the Rydberg electron is crucial in this new type of spectroscopy. The advantages of lattice-modulation spectroscopy of Rydberg-atom transitions include small trap-induced shifts, micron-scale spatial addressability, and freedom from typical selection rules. I will explain the methodís background, which engages the A2 term, not the usual A \cdot p-term. Specifically, we probe nS1/2 to (n+k)S1/2 Rydberg transitions in rubidium, with k=1, 2 or 3 and several selected values of n. The transitions occur primarily at odd harmonics of the lattice modulation frequency; in current experiments the 1st, 3rd and 5th harmonic have been demonstrated successfully. The highest transition frequency
demonstrated to date is close to 100GHz. One of the transitions probed satisfies a "magic" condition, in which the trapping potentials of the lower and upper Rydberg states coupled by the modulated lattice have the same trapping potential; this is important in high-precision spectroscopy applications.
In the second part, I will present recent results on the trapping of nanoparticles (diameter about 200nm) in an optical lattice formed in aqueous solution. We have conducted demonstration experiments in which three-dimensional (3D) optical lattices are created within a narrow gap between two identical high-NA microscope objectives. Several thousands of nanoparticles are arranged into nearly defect-free crystals with high packing and number density. Bragg scattering of green laser light is observed, and its dependence on lattice geometry and laser polarization is studied. As a first application, the time-dependence of the Bragg scattering in switched lattices is measured. The time-dependence of the Debye-Waller factors extracted from the Bragg-peak intensities is in good quantitative agreement with Brownian-motion theory. The work may lead into applications in structure analysis of mesoscopic matter (bio-molecules, viruses, bacteria, etc.).
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