Cold and Hot Spots: From Inhibition to Enhancement by Nanoscale Phase Tuning of Optical Nanoantennas.

Nicola Palombo Blascetta,Niek F Van Hulst,Costanza Toninelli,Pietro Lombardi

doi:10.1021/acs.nanolett.0c02607

Nicola Palombo Blascetta, Niek F Van Hulst + Show 2 more

Open Access

https://doi.org/10.1021/acs.nanolett.0c02607

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Abstract

Optical nanoantennas are well-known for the confinement of light into nanoscale hot spots, suitable for emission enhancement and sensing applications. Here, we show how control of the antenna dimensions allows tuning the local optical phase, hence turning a hot spot into a cold spot. We manipulate the local intensity exploiting the interference between driving and scattered field. Using single molecules as local detectors, we experimentally show the creation of subwavelength pockets with full suppression of the driving field. Remarkably, together with the cold excitation spots, we observe inhibition of emission by the phase-tuned nanoantenna. The fluorescence lifetime of a molecule scanned in such volumes becomes longer, showing slow down of spontaneous decay. In conclusion, the spatial phase of a nanoantenna is a powerful knob to tune between enhancement and inhibition in a 3-dimensional subwavelength volume.

Highlights

Most works on enhancing the emitters’ radiative decay rate focus on minimizing the mode volume, tuning the resonance, and improving the resonator quality, achieving high Purcell factors in the range from 102 to 104 20,21
Turning from the excitation to the emission, we present the first inhibition of emission close to a plasmonic nanoantenna
The scattered phase changes depending on the relative position to the antenna. The creation of such localized phase patterns is relevant for the tailoring of both the local excitation field and the local density of states (LDOS) experienced by a local emitter

Summary

Introduction

Most works on enhancing the emitters’ radiative decay rate focus on minimizing the mode volume, tuning the resonance, and improving the resonator quality, achieving high Purcell factors in the range from 102 to 104 20,21. We tune the hot-spot out of phase, creating a nanoscale pocket with full suppression of the excitation field: a cold-spot[27].

Results

Conclusion