Light can be trapped inside a cavity made by two mirrors, thus concentrating the light intensity and enhancing interactions between light and matter. Among the different applications of these photonic cavities, much attention is now focused on their ability to control the energy exchange between quantum emitters such as atoms, molecules, and quantum dots. Attempts to improve this exchange have been hampered by experimental difficulties in controlling the positions, orientations, and spectra of the emitter’s dipoles. In a recent paper published in Phys Rev X, we thoroughly characterize dipole-dipole energy transfer inside a photonic cavity and provide design rules for cavity-enhanced applications.
While previous research has focused on optical frequencies, microwave experiments allow us to measure energy transfer with a high degree of control over dipole orientation and position. We test our framework by investigating the energy transfer between two microwave antennas inside a photonic cavity and derive the conditions that enhance the transfer.
Our methodology bridges the gap between quantum electrodynamics and microwave engineering descriptions of dipole-dipole interactions. Beyond the conceptual interest, this approach provides a practical tool to quantitatively characterize photonic devices with an enhanced dipole-dipole interaction and can be readily applied to map energy transfer inside complex photonic systems at ultrahigh resolutions.
A wide range of single molecule fluorescence techniques involve the use of multi-color laser excitation, such as PIE-FRET, ALEX-FRET and FCCS. However, the influence of these various laser excitations is very often overlooked. What is the influence of the green laser on the red dyes photophysics? Adding more optical power to the sample could lead to less fluorescence photons?
In our latest article “Laser-induced fluorescence quenching of red fluorescent dyes with green excitation: avoiding artifacts in PIE-FRET and FCCS analysis”, we show that surprisingly the presence of green laser pulses can indeed quench the fluorescence of common red dyes Alexa Fluor 647 and Atto 647N. Quite surprisingly, this comes despite the fact that the green laser pulses are temporaly delayed by a time much greater than the fluorophore lifetime and that photobleaching conditions are avoided. More laser excitation but less fluorescence.
* we show how to avoid potential artifacts as both the fluorophore concentration and fluorescence brightness can be affected.
* we discuss the physical origin of this phenomenon via a long-lived dark state of the red dyes and photorefractive effects in the microscope objective.
* it provides a novel approach to check the alignment of the laser beams in the confocal microscope.
Also freely available on arXiv 1806.11364