Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review Letters

Fluorescence of Oriented Molecules in a Microcavity

Michael D. Barnes, C-Y. Kung, William Barclay Whitten, J. Michael Ramsey, S. Arnold, Stephen Holler

Published May 20, 1996• 86 citations
Publisher

Abstract

Fluorescence decay rate modification has been observed for molecules in liquid microspheres (3.5 to 25 \ensuremath{\mu}m in diameter) where the molecular position and transition moment orientation are well defined. For small sizes ( $<6$ \ensuremath{\mu}m), the decay rates scale roughly as ${r}^{\ensuremath{-}1}$ and agree quantitatively with semiclassical calculations. For larger sizes ( $>15$ \ensuremath{\mu}m) where the cavity storage time and fluorescence lifetime are roughly equal, an anomalous decrease in the decay rate of $\ensuremath{\approx}30%$ is observed which is interpreted as a consequence of intermediate molecule-cavity coupling.

DOI
10.1103/physrevlett.76.3931

Related papers

Fluorescence lifetimes of Oriented Molecules in Microdroplets

Michael D. Barnes, N. Lermer, William Barclay Whitten +2 more

Over the last several years there has been considerable interest in the properties of atomic resonance fluorescence in an optical cavity with a primary dimension comparable to the relevant transition wavelength.1 In particular, there has been great interest in the realization of strong atom-cavity coupling2 and the suppression of spontaneous emission into "free-space" modes. However, an important but poorly understood issue relevant to low- or zero-threshold condensed phase optical devices is the nonradiative coupling of the emitting species to a thermal bath. Unlike experiments involving dilute atomic beams where the transition is well defined and broadening is negligible, coupling to a thermal bath induces spectral broadening which is usually much larger than the cavity resonance width and may often exceed the cavity mode spacing. Interesting examples of such systems are solvated dyes whose condensed phase dynamics are well known and characterized. To date, several studies have been made on fluorescence properties of solvated dyes in microcavities,3,4,5 however additional complexities such as spatial and orientational averaging have obscured to some extent the connection between radiative and nonradiative processes in such systems. We discuss the observation of spontaneous emission rate modification (both enhancement and apparent suppression) for molecular species in a microcavity where both the molecular position and transition moment orientation are well defined.6 These experiments serve as an interesting test case of molecule-cavity systems in which the emitting species is nonradiatively coupled to a thermal bath.

Quantum Optoelectronics•Jan 1, 1997•0 citations

Detection of Single Molecules in Microcavities

N. Lermer, Michael D. Barnes, C-Y. Kung +2 more

A significant limitation in the detection and spectroscopy of individual dye molecules in liquid room temperature samples is the loss of fluorescence signal through chromophore photobleaching. Although often considered a fundamental restriction on sensitivity, it has been shown that the probability per excitation cycle of photobleaching may be reduced by enhancing the spontaneous emission rate of the chromophore located inside a microdroplet, which acts as a optical cavity. Studies of glycerol microdroplets containing R6G dye molecules, and levitated in a three-dimensional electrodynamic trap, have demonstrated a significant enhancement of both the fluorescence decay rate [1] and the total fluorescence yield [2] of the chromophore. Modification of the emission rate is greatest for molecules located near the surface of small (< 10 μm) microdroplets, where the influence of the droplet cavity modes of the droplet is most significant. To exploit this surface sensitivity, surfactant forms of rhodamine dyes were recently studied [3]. Fluorescence emission of the dye molecules, constrained to the droplet surface and with fixed transition moments perpendicular to the surface normal, were shown to be significantly enhanced at small droplet sizes. Additionally, at larger droplet sizes corresponding to higher droplet Q’s, preferential emission into the cavity modes was observed, however the detection of fluorescence photons was delayed by the storage time of the cavity, which may be on the same order as the fluorescence lifetime. These measurements, performed on relatively concentrated dye solutions, suggest that microcavity effects may be exploited to greatly enhance single molecule detection sensitivity in glycerol microdroplets. Furthermore, the large cavity storage time of the high-Q droplets opens the possibility for re-excitation of the molecule following emission into the droplet resonance, and subsequent stimulated emission, that is, single-molecule lasing.

Laser Applications to Chemical, Security and Environmental Analysis•Jan 1, 1998•0 citations

Quantum theory of microcavity-modified fluorescence decay rate under a strong coupling condition

Ying Wu

In this article, we propose a simple approach to deal with the fluorescence of a quasi-three-level system in $\ensuremath{\Lambda}$ configuration in which one of the ``levels'' is actually a band with possibly a large width. By solving this quasi-three-level molecule model, we obtain an analytical expression for the microcavity-modified fluorescence decay rate suitable for arbitrary cavities with any geometrical shape under a strong coupling condition. Applying the general result to a microsphere, we express explicitly the fluorescence decay rate's dependence on the cavity radius, emission linewidth, and the quantities characterizing the involved cavity modes, and find it in remarkable agreement with the recent fluorescence experiment by Barnes et al. [Phys. Rev. Lett. 76, 3931 (1996)]. In addition we briefly discuss the suitability of the approach for other microcavity-modified optical processes such as lasing and Raman scattering.

Physical Review A•Feb 11, 2000•48 citations

Cavity-enhanced spontaneous emission rates for rhodamine 6-G in levitated microdroplets

Michael D. Barnes, William Barclay Whitten, J. Michael Ramsey +1 more

Fluorescence decay kinetics of Rhodamine 6-G molecules in levitated glycerol microdroplets (4--20 microns in diameter) have been investigated to determine the effects of spherical cavity resonances on spontaneous emission rates. For droplet diameters greater than 10 microns, the fluorescence lifetime is essentially the same as in bulk glycerol. As the droplet diameter is decreased below 10 microns, bi-exponential decay behavior is observed with a slow component whose rate is similar to bulk glycerol, and a fast component whose rate is as much as a factor of 10 larger than the bulk decay rate. This fast component is attributed to cavity enhancement of the spontaneous emission rate and, within the weak coupling approximation, a value for the homogeneous linewidth at room temperature can be estimated from the fluorescence lifetime data.

•Jan 1, 1992•1 citation

Detection of single molecules in microspheres

Michael D. Barnes, William Barclay Whitten, J. Michael Ramsey +2 more

We have investigated the use of micron-sized liquid droplets as sample medium to detect single fluorescent molecules in solution. The use of microdroplets (5 - 15 micrometers diameter) offers several powerful advantages over single-molecule detection schemes involving measurements on bulk liquids where the probe volume is defined by the laser beam. In addition, cavity-quantum electrodynamical (QED) effects have been observed which influence both spontaneous emission rates and fluorescence yields of dye molecules in these microspheres.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•May 18, 1993•3 citations

Controlling the optical properties of single molecules by optical confinement in a tunable microcavity

Raphael Gutbrod, Alexey I. Chizhik, Anna M. Chizhik +4 more

Optical microcavities are structures which confine light to a small region in the range of one wavelength. The radiation of a quantum emitter is coupled to cavity resonances which leads to an optical confinement of the broadband fluorescence. A practical design for this single-mode microcavity is formed by two silver mirrors enclosing a transparent dielectric medium with single quantum emitters. Steiner et al. have shown that the fluorescence spectra and decay lifetimes of single molecules in this Fabry-Perot type microcavity are strongly dependent on the resonator length.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 1, 2009•1 citation
Fluorescence decay rate modification has been observed for molecules in liquid microspheres (3.5 to 25 \ensuremath{\mu}m in diameter) where the molecular position and transition moment orientation are well defined. For small sizes ( <6<6<6 \ensuremath{\mu}m), the decay rates scale roughly as r\ensuremath−1{r}^{\ensuremath{-}1}r\ensuremath−1 and agree quantitatively with semiclassical calculations. For larger sizes ( >15>15>15 \ensuremath{\mu}m) where the cavity storage time and fluorescence lifetime are roughly equal, an anomalous decrease in the decay rate of \ensuremath≈30\ensuremath{\approx}30%\ensuremath≈30 is observed which is interpreted as a consequence of intermediate molecule-cavity coupling.
Over the last several years there has been considerable interest in the properties of atomic resonance fluorescence in an optical cavity with a primary dimension comparable to the relevant transition wavelength.1 In particular, there has been great interest in the realization of strong atom-cavity coupling2 and the suppression of spontaneous emission into "free-space" modes. However, an important but poorly understood issue relevant to low- or zero-threshold condensed phase optical devices is the nonradiative coupling of the emitting species to a thermal bath. Unlike experiments involving dilute atomic beams where the transition is well defined and broadening is negligible, coupling to a thermal bath induces spectral broadening which is usually much larger than the cavity resonance width and may often exceed the cavity mode spacing. Interesting examples of such systems are solvated dyes whose condensed phase dynamics are well known and characterized. To date, several studies have been made on fluorescence properties of solvated dyes in microcavities,3,4,5 however additional complexities such as spatial and orientational averaging have obscured to some extent the connection between radiative and nonradiative processes in such systems. We discuss the observation of spontaneous emission rate modification (both enhancement and apparent suppression) for molecular species in a microcavity where both the molecular position and transition moment orientation are well defined.6 These experiments serve as an interesting test case of molecule-cavity systems in which the emitting species is nonradiatively coupled to a thermal bath.
A significant limitation in the detection and spectroscopy of individual dye molecules in liquid room temperature samples is the loss of fluorescence signal through chromophore photobleaching. Although often considered a fundamental restriction on sensitivity, it has been shown that the probability per excitation cycle of photobleaching may be reduced by enhancing the spontaneous emission rate of the chromophore located inside a microdroplet, which acts as a optical cavity. Studies of glycerol microdroplets containing R6G dye molecules, and levitated in a three-dimensional electrodynamic trap, have demonstrated a significant enhancement of both the fluorescence decay rate [1] and the total fluorescence yield [2] of the chromophore. Modification of the emission rate is greatest for molecules located near the surface of small (< 10 μm) microdroplets, where the influence of the droplet cavity modes of the droplet is most significant. To exploit this surface sensitivity, surfactant forms of rhodamine dyes were recently studied [3]. Fluorescence emission of the dye molecules, constrained to the droplet surface and with fixed transition moments perpendicular to the surface normal, were shown to be significantly enhanced at small droplet sizes. Additionally, at larger droplet sizes corresponding to higher droplet Q’s, preferential emission into the cavity modes was observed, however the detection of fluorescence photons was delayed by the storage time of the cavity, which may be on the same order as the fluorescence lifetime. These measurements, performed on relatively concentrated dye solutions, suggest that microcavity effects may be exploited to greatly enhance single molecule detection sensitivity in glycerol microdroplets. Furthermore, the large cavity storage time of the high-Q droplets opens the possibility for re-excitation of the molecule following emission into the droplet resonance, and subsequent stimulated emission, that is, single-molecule lasing.
In this article, we propose a simple approach to deal with the fluorescence of a quasi-three-level system in $\ensuremath{\Lambda}$ configuration in which one of the ``levels'' is actually a band with possibly a large width. By solving this quasi-three-level molecule model, we obtain an analytical expression for the microcavity-modified fluorescence decay rate suitable for arbitrary cavities with any geometrical shape under a strong coupling condition. Applying the general result to a microsphere, we express explicitly the fluorescence decay rate's dependence on the cavity radius, emission linewidth, and the quantities characterizing the involved cavity modes, and find it in remarkable agreement with the recent fluorescence experiment by Barnes et al. [Phys. Rev. Lett. 76, 3931 (1996)]. In addition we briefly discuss the suitability of the approach for other microcavity-modified optical processes such as lasing and Raman scattering.
Fluorescence decay kinetics of Rhodamine 6-G molecules in levitated glycerol microdroplets (4--20 microns in diameter) have been investigated to determine the effects of spherical cavity resonances on spontaneous emission rates. For droplet diameters greater than 10 microns, the fluorescence lifetime is essentially the same as in bulk glycerol. As the droplet diameter is decreased below 10 microns, bi-exponential decay behavior is observed with a slow component whose rate is similar to bulk glycerol, and a fast component whose rate is as much as a factor of 10 larger than the bulk decay rate. This fast component is attributed to cavity enhancement of the spontaneous emission rate and, within the weak coupling approximation, a value for the homogeneous linewidth at room temperature can be estimated from the fluorescence lifetime data.
We have investigated the use of micron-sized liquid droplets as sample medium to detect single fluorescent molecules in solution. The use of microdroplets (5 - 15 micrometers diameter) offers several powerful advantages over single-molecule detection schemes involving measurements on bulk liquids where the probe volume is defined by the laser beam. In addition, cavity-quantum electrodynamical (QED) effects have been observed which influence both spontaneous emission rates and fluorescence yields of dye molecules in these microspheres.
Optical microcavities are structures which confine light to a small region in the range of one wavelength. The radiation of a quantum emitter is coupled to cavity resonances which leads to an optical confinement of the broadband fluorescence. A practical design for this single-mode microcavity is formed by two silver mirrors enclosing a transparent dielectric medium with single quantum emitters. Steiner et al. have shown that the fluorescence spectra and decay lifetimes of single molecules in this Fabry-Perot type microcavity are strongly dependent on the resonator length.