Measurement of Vibrational Modes in SingleSiO2Nanoparticles Using a Tunable Metal Resonator with Optical Subwavelength Dimensions

Abstract

Using a tunable optical subwavelength microcavity, we demonstrate controlled modification of the vibronic relaxation dynamics in a single SiO(2) nanoparticle. By varying the distance between the cavity mirrors we change the electromagnetic field mode structure around a single nanoparticle and the radiative transition probability from the lowest vibronic level of the electronically excited state to the progression of phonon levels in the electronic ground state. We demonstrate redistribution of the photoluminescence spectrum between zero-phonon and phonon-assisted bands and modification of the excited state lifetime of the same individual SiO(2) particle measured at different cavity lengths. By comparing the experimental data with a theoretical model, we extract the quantum yield of a single SiO(2) nanoparticle.

Photoluminescence of a single quantum emitter in a strongly inhomogeneous chemical environment

“…However, our recently developed nanocavity-based method of QY determination measures only the cavity modulated radiative decay rate of an emitter, which makes it also applicable for such complex systems as SiO 2 NPs 28, 29 . Placing SiO 2 NPs between the metal mirrors of a nanocavity changes their emission behavior due to a cavity-modified electromagnetic field mode density 8,30,31 . Because the cavity changes only the radiative rate of the embedded emitters, measuring the modulation of the PL lifetime as a function of the cavity length allows for determining an absolute value of an emitters' QY 32 .…”

“…A typical example of an emitter that is chemically bound to a matrix is a luminescent centre in a SiO 2 nanoparticle (NP) 7,8 . It has been shown that the PL from SiO 2 structures in the visible spectral range arises from non-bridging oxygen centres [9][10][11] , neutral oxygen vacancies 11,12 , and hydrogen-related species 13 .…”

“…It has been shown that the PL from SiO 2 structures in the visible spectral range arises from non-bridging oxygen centres [9][10][11] , neutral oxygen vacancies 11,12 , and hydrogen-related species 13 . Measurements of single SiO 2 nanoparticle (NP) photoluminescence revealed a strong coupling between the electronic transition and collective vibrations in the SiO 2 network due to a relaxation mechanism involving charge transfer 7,8 . In particular, the PL spectra of a single SiO 2 NP exhibit, besides a narrow zero-phonon line, one or even two satellite peaks at the lower-energy end, which are related to the excitation of one or two longitudinal optical phonons in the particle.…”

Nanocavity‐Based Determination of Absolute Values of Photoluminescence Quantum Yields

“…[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. [23,24] An efficient way of changing the LDOS of the electromagnetic field is to embed an emitter into a plane-parallel optical resonator, [25][26][27][28][29][30] which allows for precise control of the LDOS by varying the cavity length. Moreover, this length can be precisely monitored by measuring the cavity's transmission spectrum, which eliminates potential systematic errors caused by mechanical instabilities of the system.…”

λ/2 Fabry Pérot micro-resonators in single molecule spectroscopy

“…Using a tuneable optical micro-resonator with subwavelength spacing, we demonstrate controlled modulation of the radiative transition rate of a single molecule, which is measured by monitoring its fluorescence lifetime [4]. By comparing the experimental data with a theoretical model, we extract both the pure radiative transition rate as well as the quantum yields of individual molecules.…”