Surface-plasmon-based dispersive detection and spectroscopy of ultracold atoms

The paper reports on the optical detection and spectroscopy of ultracold atoms near a gold surface. A probe light field is used to excite surface plasmon polaritons. The refractive index of the atomic gas shifts the plasmon resonance and changes the reflected light power. Thus, the sensitivity of the detection is plasmonically enhanced. Absorption of photons from the evanescent wave is avoided by detuning the laser from atomic resonance which makes the detection scheme potentially nondestructive. The spectrum of the signal is determined by a Fano resonance. We show that atoms can be detected nondestructively with single atom resolution for typical parameters in cold atom experiments. Thus, the method is suitable for quantum nondemolition measurements of matter wave amplitudes. Experimentally, we measure a technically limited sensitivity of 30 atoms and extend the detection scheme to dispersively image the atom cloud near the surface.

Automated summary

This paper presents optical detection and spectroscopy of ultracold atoms near a gold surface, using a probe light field to excite surface plasmon polaritons. By shifting the plasmon resonance due to the refractive index of the atomic gas, the sensitivity of detection is enhanced. The nondestructive detection of atoms with single atom resolution is achieved by detuning the laser from atomic resonance, making it suitable for quantum nondemolition measurements of matter wave amplitudes.