Probing the Radiative Transition of Single Molecules with a Tunable Microresonator

Abstract

Using a tunable optical microresonator with subwavelength spacing, we demonstrate controlled modulation of the radiative transition rate of a single molecule, which is measured by monitoring its fluorescence lifetime. Variation of the cavity length changes the local mode structure of the electromagnetic field, which modifies the radiative coupling of an emitting molecule to that field. By comparing the experimental data with a theoretical model, we extract both the pure radiative transition rate as well as the quantum yield of individual molecules. We observe a broad scattering of quantum yield values from molecule to molecule, which reflects the strong variation of the local interaction of the observed molecules with their host environment.

Determining the internal quantum efficiency of shallow-implanted nitrogen-vacancy defects in bulk diamond

“…To precisely control the separation between the dye molecules and the mirror, he used the Langmuir-Blodgett dipping technique to deposit a varying number of layers of fatty acid on a metal surface. The same scheme, but with a number of improvements and modifications, has been used to characterize different types of quantum emitters: single molecules [18][19][20], self-assembled [21,22] and colloidal [23] quantum dots, as well as NV defects in diamond nanocrystals [15]. In our work, we use an experimental approach that was first suggested in [19] and later modified for well calibrated measurements [15,23].…”

Nanocavity‐Based Determination of Absolute Values of Photoluminescence Quantum Yields

“…In recent years, several publications have dealt with the controlled modification of the radiative transition rate of an emitter by tuning the local density of states (LDOS) of the electromagnetic field at its position. We have recently employed such a tunable cavity to measure the QY of single molecules at fixed positions inside the resonator, [28] and for investigating the impact of rotational diffusion on the electrodynamic coupling of dipole emitters to the cavity modes. [16] This so-called Purcell effect has been measured for fluorophores placed between two gold nanoparticles, [17] close to a dielectric interface, [19,18] a metallic mirror, [20][21][22] or a sharp tip of a scanning probe microscope.…”

Electrodynamic Coupling of Electric Dipole Emitters to a Fluctuating Mode Density within a Nanocavity

“…Finally, the fluorescence decay curves were fitted with a multi-exponential decay model, from which the average excited state lifetime was calculated according to Eq. (15). Fig.…”

“…For the lifetime measurements, a droplet of a micromolar solution of rhodamine 6G molecules in water or glycerol was embedded between the cavity mirrors. The cavity length was determined by measuring the white light transmission spectrum [14,15] using a spectrograph (Andor SR 303i) and a CCD camera (Andor iXon DU897 BV), and by fitting the spectra with a standard Fresnel model of transmission through a stack of plan-parallel layers, where the cavity length (distance between silver mirrors) was the only free fit parameter.…”

“…1) and will always result in average lifetime values smaller then the freespace lifetime. Finally, it should be emphasized that the excellent agreement between theoretical model and experimental results offer the fascinating possibility to use lifetime measurements on dye solutions in tunable nanocavities for simple and direct determination of the fluorescence quantum yield, a quantity which is notoriously difficult to determine by other methods [15].…”