Observation of the photorefractive effect in a polymer

We report the first observation of the photorefractive effect in a polymeric material, the electro-optic polymer bisphenol-A-diglycidylether 4-nitro-1,2-phenylenediamine made photoconductive by doping with the hole-transport agent diethylamino-benzaldehyde diphenylhydrazone. The gratings formed exhibit dynamic writing and erasure, strong electric-field dependence, polarization anisotropy, and estimated space-charge fields up to 26 kV/cm at an applied field of 126 kV/cm. Application of similar concepts should provide a broad new class of easily fabricated photorefractive materials

Interferometry of a Single Nanoparticle Using the Gouy Phase of a Focused Laser Beam

We provide a quantitative explanation of the mechanism of the far-field intensity modulation induced by a nanoparticle in a focused Gaussian laser beam, as was demonstrated in several recent direct detection studies. Most approaches take advantage of interference between the incident light and the scattered light from a nanoparticle to facilitate a linear dependence of the signal on the nanoparticle volume. The phase relation between the incoming field and the scattered field by the nanoparticle is elucidated by the concept of Gouy phase. This phase relation is used to analyze the far-field signal-to-noise ratio as a function of exact nanoparticle position with respect to the beam focus. The calculation suggests that a purely dispersive nanoparticle should be displaced from the Gaussian beam focus to generate a far-field intensity change

Single-molecule trapping and spectroscopy reveals photophysical heterogeneity of phycobilisomes quenched by Orange Carotenoid Protein

Upon photoactivation the Orange Carotenoid Protein (OCP) binds to the phycobilisome and prevents damage by thermally dissipating excess energy. Here authors use an Anti-Brownian ELectrokinetic trap to determine the photophysics of single OCP-quenched phycobilisomes and observe two distinct OCP-quenched states with either one or two OCPs bound

Strongly focused light beams interacting with single atoms in free space

We construct 3-D solutions of Maxwell's equations that describe Gaussian light beams focused by a strong lens. We investigate the interaction of such beams with single atoms in free space and the interplay between angular and quantum properties of the scattered radiation. We compare the exact results with those obtained with paraxial light beams and from a standard input-output formalism. We put our results in the context of quantum information processing with single atoms.Comment: 9 pages, 9 figure

Single-molecule identification of quenched and unquenched states of LHCII

In photosynthetic light harvesting, absorbed sunlight is converted to electron flow with near-unity quantum efficiency under low light conditions. Under high light conditions, plants avoid damage to their molecular machinery by activating a set of photoprotective mechanisms to harmlessly dissipate excess energy as heat. To investigate these mechanisms, we study the primary antenna complex in green plants, light-harvesting complex II (LHCII), at the single-complex level. We use a single-molecule technique, the Anti-Brownian Electrokinetic trap, which enables simultaneous measurements of fluorescence intensity, lifetime, and spectra in solution. With this approach, including the first measurements of fluorescence lifetime on single LHCII complexes, we access the intrinsic conformational dynamics. In addition to an unquenched state, we identify two partially quenched states of LHCII. Our results suggest that there are at least two distinct quenching sites with different molecular compositions, meaning multiple dissipative pathways in LHCII. Furthermore, one of the quenched conformations significantly increases in relative population under environmental conditions mimicking high light.This material is based on work supported in part by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under Award Number DE-FG02-07ER15892 (to W.E.M) and by the Dutch organization for scientific research (NWO-ALW) via a Vici grant (to R.C.). R.v.G. and T.P.J.K. were supported by the Netherlands Organization for Sciences, Council of Chemical Sciences (NWO-CW) via a TOP-grant (700.58.305). R.v.G. was further supported by an Advanced Investigator grant from the European Research Council (no. 267333, PHOTPROT) and by the EU FP7 project PAPETS (GA 323901). R.v.G. gratefully acknowledges his Academy Professor grant from the Royal Netherlands Academy of Arts and Sciences (KNAW). T.P.J.K. was further supported by University of Pretoria’s Research Development Programme (grant no. A0W679). The authors would like to acknowledge the following fellowships: a Postdoctoral Fellowship from the Center for Molecular Analysis and Design at Stanford University (to G.S.S.-C.); a Kenneth and Nina Tai Stanford Graduate Fellowship (to H.-Y.Y.); and a Long Term Fellowship from EMBO (to M.G.).http://pubs.acs.org/journal/jpclcdhb2017Physic

Single-molecule identification of quenched and unquenched states of LHCII

In photosynthetic light harvesting, absorbed sunlight is converted to electron flow with near-unity quantum efficiency under low light conditions. Under high light conditions, plants avoid damage to their molecular machinery by activating a set of photoprotective mechanisms to harmlessly dissipate excess energy as heat. To investigate these mechanisms, we study the primary antenna complex in green plants, light-harvesting complex II (LHCII), at the single-complex level. We use a single-molecule technique, the Anti-Brownian Electrokinetic trap, which enables simultaneous measurements of fluorescence intensity, lifetime, and spectra in solution. With this approach, including the first measurements of fluorescence lifetime on single LHCII complexes, we access the intrinsic conformational dynamics. In addition to an unquenched state, we identify two partially quenched states of LHCII. Our results suggest that there are at least two distinct quenching sites with different molecular compositions, meaning multiple dissipative pathways in LHCII. Furthermore, one of the quenched conformations significantly increases in relative population under environmental conditions mimicking high light.This material is based on work supported in part by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under Award Number DE-FG02-07ER15892 (to W.E.M) and by the Dutch organization for scientific research (NWO-ALW) via a Vici grant (to R.C.). R.v.G. and T.P.J.K. were supported by the Netherlands Organization for Sciences, Council of Chemical Sciences (NWO-CW) via a TOP-grant (700.58.305). R.v.G. was further supported by an Advanced Investigator grant from the European Research Council (no. 267333, PHOTPROT) and by the EU FP7 project PAPETS (GA 323901). R.v.G. gratefully acknowledges his Academy Professor grant from the Royal Netherlands Academy of Arts and Sciences (KNAW). T.P.J.K. was further supported by University of Pretoria’s Research Development Programme (grant no. A0W679). The authors would like to acknowledge the following fellowships: a Postdoctoral Fellowship from the Center for Molecular Analysis and Design at Stanford University (to G.S.S.-C.); a Kenneth and Nina Tai Stanford Graduate Fellowship (to H.-Y.Y.); and a Long Term Fellowship from EMBO (to M.G.).http://pubs.acs.org/journal/jpclcdhb2017Physic

Photon Statistics; Nonlinear Spectroscopy of Single Quantum Systems

A unified description of multitime correlation functions, nonlinear response functions, and quantum measurements is developed using a common generating function which allows a direct comparison of their information content. A general formal expression for photon counting statistics from single quantum objects is derived in terms of Liouville space correlation functions of the material system by making a single assumption that spontaneous emission is described by a master equation