Tight focusing of laser beams in a λ/2-microcavity

Khoptyar, Dmitry; Gutbrod, Raphael; Chizhik, Anna M.; Enderlein, Jörg; Schleifenbaum, Frank; Steiner, M.; Meixner, Alfred J.

doi:10.1364/oe.16.009907

Cited by 28 publications

(16 citation statements)

References 18 publications

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“…The initial distribution p(θ, t = 0) right after excitation is defined by the polarization and intensity of the focused excitation light. These can be found by again expanding the electromagnetic field of the focused laser beam into a plane wave representation [9,10], and calculating the interaction of each plane wave with the cavity [11]. If one denotes the horizontal and vertical components of the excitation intensity at the position of the molecules by I and I ⊥ , respectively, then p(θ, t = 0) is given by…”

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

et al. 2012

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We investigate the impact of rotational diffusion on the electrodynamic coupling of fluorescent dye molecules (oscillating electric dipoles) to a tunable planar metallic nanocavity. Fast rotational diffusion of the molecules leads to a rapidly fluctuating mode density of the electromagnetic field along the molecules' dipole axis, which significantly changes their coupling to the field as compared to the opposite limit of fixed dipole orientation. We derive a theoretical treatment of the problem and present experimental results for rhodamine 6G molecules in cavities filled with low and high viscosity liquids. The derived theory and presented experimental method is a powerful tool for determining absolute quantum yield values of fluorescence. Introduction.-Fluorescing molecules located close to a metal surface (at sub-wavelength distance) or inside a metal nano-cavity, dramatically change their fluorescence emission properties such as fluorescence lifetime, fluorescence quantum yield, emission spectrum, or angular distribution of radiation [1][2][3][4]. This is due to the change local density of modes of the electromagnetic field caused by the presence of the metal surfaces [5]. Although a large amount of studies have dealt with the investigation of this effect, they all have considered fixed dipole orientations of the emitting molecules, so that each molecule exhibits a temporally constant mode density during its de-excitation from the excited to the ground state. However, when molecules are dissolved in a solvent such as water, their rotational diffusion leads to rapid changes of dipole orientation even on the time-scale of the average excited state lifetime. We will show here that this dramatically influences the coupling of the molecules to the local, strongly orientation-dependent density of modes and the resulting excited state lifetime. This is enormously important for applications of tunable nanocavities for fluorescence quantum yield measurements.

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

et al. 2012

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“…The calcula- tions showed that the observed molecule was close to the upper polymer interface (toward the oil) and had a nearly vertical orientation. Because of the special electric field configuration of the focused laser light inside the cavity [13], such dipoles are efficiently excited. The obtained values of spectral shift between À2 nm and À14 nm are common when observing single perylene emission spectra, and similar values have been reported before [14].…”

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Tuning the Fluorescence Emission Spectra of a Single Molecule with a Variable Optical Subwavelength Metal Microcavity

et al. 2009

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We present experimental and theoretical results on changing the fluorescence emission spectrum of a single molecule by embedding it within a tunable planar microcavity with subwavelength spacing. The cavity length is changed with nanometer precision by using a piezoelectric actuator. By varying its length, the local mode structure of the electromagnetic field is changed together with the radiative coupling of the emitting molecule to the field. Because mode structure and coupling are both frequency dependent, this leads to a renormalization of the emission spectrum of the molecule. We develop a theoretical model for these spectral changes and find excellent agreement between theoretical prediction and experimental results.

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“…Starting from the general theory of focusing a laser beam with a high numerical aperture optical system, 18,19 the field distribution of a RPDB inside a microresonator has recently been calculated and experimentally verified. 20,21 In short, the focused field intensity distribution of the RPDB is characterized by the in-plane components E x and E y and the longitudinal component E z of the incident laser beam and can be expressed as…”

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“…The functions L n,m,l characterize the in-plane and longitudinal components of the intracavity field. 20 On the basis of eq 1 and taking the actual optical parameters of the resonator and the microscope objective into account, we can visualize the intensity distribution between the cavity mirrors which is shown in Figure 2 for three representative L values. The in-plane field components have maximum intensity in the cavity center and vanish toward the metal mirrors.…”

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Three-Dimensional Orientation of Single Molecules in a Tunable Optical λ/2 Microresonator

et al. 2010

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A tightly focused radially polarized laser beam forms an unusual bimodal field distribution in an optical lambda/2-microresonator. We use a single-molecule dipole to probe the vector properties of this field distribution by tuning the resonator length with nanometer precision. Comparing calculated and experimental excitation patterns provides the three-dimensional orientation of the single-molecule dipole in the microresonator.

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Tight focusing of laser beams in a λ/2-microcavity

Cited by 28 publications

References 18 publications

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

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

Tuning the Fluorescence Emission Spectra of a Single Molecule with a Variable Optical Subwavelength Metal Microcavity

Three-Dimensional Orientation of Single Molecules in a Tunable Optical λ/2 Microresonator

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