Two-dimensional electronic coherence spectroscopy (ECS) is an important method to study the coupling between distinct optical modes of a material system. Such studies often involve excitation using a sequence of phased ultrashort laser pulses. In conventional approaches, the delays between pulse temporal envelopes must be precisely monitored or maintained. Here, we introduce a new experimental scheme for phase-selective nonlinear ECS, which combines acousto-optic phase modulation with ultrashort laser excitation to produce intensity modulated nonlinear fluorescence signals. We isolate specific nonlinear signal contributions by synchronous detection, with respect to appropriately constructed references. Our method effectively decouples the relative temporal phases from the pulse envelopes of a collinear train of four sequential pulses. We thus achieve a robust and high signal-to-noise scheme for phase-selective ECS to investigate the resonant nonlinear optical response of photoluminescent systems. We demonstrate the validity of our method using a model quantum three-level system-atomic Rb vapor. Moreover, we show how our measurements determine the resonant complex-valued third-order susceptibility.
We report two-color two-dimensional Fourier transform electronic spectroscopy obtained using an acousto-optic pulse-shaper in a pump-probe geometry. The two-color setup will facilitate the study of energy transfer between electronic transitions that are widely separated in energy. We demonstrate the method at visible wavelengths on the laser dye LDS750 in acetonitrile. We discuss phase-cycling and polarization schemes to optimize the signal-to-noise ratio in the pump-probe geometry. We also demonstrate that phase-cycling can be used to separate rephasing and nonrephasing signal components.
Two-dimensional decay associated spectra 2C2DES Two-color two-dimensional electronic spectroscopy 2DES Two-dimensional electronic spectroscopy 2DIR Two-dimensional infrared spectroscopy 2PE Two-pulse photon echo BBO Beta-barium borate BChl Bacteriochlorophyll BRC Bacterial reaction center CCD Charge-collecting device CGS Common ground state Chl Chlorophyll CP Cross-peak CS Charge separation DAS Decay associated spectra DMSO Dimethyl sulfoxide DO Diffractive optic DSP Digital signal processor EET Excitation energy transfer ESM Exponential series method ESA Excited state absorption xiv ESE Excited state emission ET Energy transfer FRET Fluorescence resonance energy transfer GSB Ground state bleach LHCII Light-harvesting complex II LN Liquid nitrogen LO Local oscillator NMR Nuclear magnetic resonance NOPA Non-collinear optical parametric amplifier OD Optical density PC Prism compressor PERY N,N'-bis (2,6-dimethylphenyl) perylene-3,4,9,10-tetracarboxylicdiimide Pheo Pheophytin PSI Photosystem I PSII Photosystem II RC D1D2-cyt.b559 reaction center complex SFG Sum frequency generation SHB Spectral hole burning SNR Signal-to-noise ratio SPM Self-phase modulation SVD Singular value decomposition TA Transient absorption TRF Time-resolved fluorescence ZAP-SPIDER Zero additional phase spectral interferometry for direct electric field reconstruction xv ABSTRACT Two-Dimensional Electronic Spectroscopy of the Photosystem II D1D2-cyt.b559
Studies of wave packet dynamics often involve phase-selective measurements of coherent optical signals generated from sequences of ultrashort laser pulses. In wave packet interferometry (WPI), the separation between the temporal envelopes of the pulses must be precisely monitored or maintained. Here we introduce a new (and easy to implement) experimental scheme for phase-selective measurements that combines acousto-optic phase modulation with ultrashort laser excitation to produce an intensity-modulated fluorescence signal. Synchronous detection, with respect to an appropriately constructed reference, allows the signal to be simultaneously measured at two phases differing by 90 degrees. Our method effectively decouples the relative temporal phase from the pulse envelopes of a collinear train of optical pulse pairs. We thus achieve a robust and high signal-to-noise scheme for WPI applications, such as quantum state reconstruction and electronic spectroscopy. The validity of the method is demonstrated, and state reconstruction is performed, on a model quantum system--atomic Rb vapor. Moreover, we show that our measurements recover the correct separation between the absorptive and dispersive contributions to the system susceptibility.
We develop the theoretical framework for calculating magnetic noise from conducting two-dimensional (2D) materials. We describe how local measurements of this noise can directly probe the wave-vector dependent transport properties of the material over a broad range of length scales, thus providing new insight into a range of correlated phenomena in 2D electronic systems. As an example , we demonstrate how transport in the hydrodynamic regime in an electronic system exhibits a unique signature in the magnetic noise profile that distinguishes it from diffusive and ballistic transport and how it can be used to measure the viscosity of the electronic fluid. We employ a Boltzmann approach in a two-time relaxation-time approximation to compute the conductivity of graphene and quantitatively illustrate these transport regimes and the experimental feasibility of observing them. Next, we discuss signatures of isolated impurities lodged inside the conducting 2D material. The noise near an impurity is found to be suppressed compared to the background by an amount that is directly proportional to the cross-section of electrons/holes scattering off of the impurity. We use these results to outline an experimental proposal to measure the temperature dependent level-shift and line-width of the resonance associated with an Anderson impurity.
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