Optical cold damping of neutral nanoparticles near the ground state in an optical lattice

We propose and demonstrate purely optical feedback cooling of neutral nanoparticles in an optical lattice to an occupation number of 0.85 +/- 0.20. The cooling force is derived from the optical gradients of displaced optical lattices produced with two sidebands on the trapping laser. To achieve highly accurate position observations required for cooling near the ground state, we reduce the laser intensity noise to a relative power noise of 6x10(-8)/Hz in a frequency band of 30 kHz to 600 kHz. We establish a reproducible method for neutralizing nanoparticles at high vacuum via a combination of discharging and irradiating an ultraviolet light. Our results form an important basis for the investigation of quantum mechanical properties of ultracold nanoparticles and are also useful for precision measurements with neutral nanoparticles. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

In this study, we propose and demonstrate a purely optical feedback cooling method for neutral nanoparticles, achieving an occupation number of 0.85 +/- 0.20. The cooling force is derived from the optical gradients of displaced optical lattices produced with two sidebands on the trapping laser. We reduce the laser intensity noise and establish a method for neutralizing nanoparticles, providing a foundation for investigating the quantum mechanical properties of ultracold nanoparticles and precision measurements.