Interference effects in the sum frequency generation spectra of thin organic films. II: Applications to different thin-film systems

Tong, Yujin; Zhao, Yanbao; Li, Na; Ma, Yunsheng; Osawa, Masatoshi; Davies, Paul B.; Ye, Shen

doi:10.1063/1.3428673

Cited by 26 publications

(7 citation statements)

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“…As we will show in the following, one experimental technique that can overcome these challenges is the laser based technique of The Journal of Chemical Physics ARTICLE scitation.org/journal/jcp phase-sensitive sum frequency generation spectroscopy (PS-SFG). SFG spectroscopy is typically applied to study interfaces; [7][8][9][10][11][12][13][14][15] however, in case that the bulk of a sample lacks centrosymmetry both can be probed, its surface and the bulk. 16,17 Like all second order nonlinear spectroscopic techniques, the generated (SFG) signal carries detailed information on the symmetry of the sample.…”

Section: Introductionmentioning

confidence: 99%

Quantitative determination of the nonlinear bulk and surface response from alpha-quartz using phase sensitive SFG spectroscopy

et al. 2019

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We investigate the nonlinear optical response of alpha-quartz with phase-sensitive vibrational sum frequency generation (SFG) spectroscopy. Phase and amplitude of the generated sum frequency signal are determined by a complex interplay between signal contributions from the surface and the bulk of the crystal with the experimental geometry, in particular, the quartz azimuth. By combining anisotropy measurements with spectral-and phase resolution in our SFG experiment, we study this interplay and show that we can quantitatively isolate and characterize the contributions from the surface and bulk of the crystal. The obtained optical constants in combination with the presented mathematical framework fully describe the nonlinear response and allow for a precise determination of the phase of the overall SFG signal of quartz for any experimental geometry. This knowledge is of particular relevance because quartz is commonly used as a reference in phase sensitive SFG experiments. In such studies, the surface contribution is typically neglected and a constant value for the phase of the sum frequency response is assumed. Our study shows that this assumption is not generally accurate by revealing the considerable impact that the surface contribution can have on the overall response of the crystal.

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Section: Introductionmentioning

confidence: 99%

Quantitative determination of the nonlinear bulk and surface response from alpha-quartz using phase sensitive SFG spectroscopy

et al. 2019

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“…This kind of thin-film model can be experimentally reproduced by using deuterated LB multilayers to verify the validity of the calculations and this will be reported in the following paper. 46 In Secs. III B and III C, we first elucidate the thickness dependence of the L factors for the two interfaces ͑buried and free interfaces, Figs.…”

Section: A Model Descriptionmentioning

confidence: 99%

“…The substantial extension of the present model system to other systems including the influence of different experimental parameters, such as the incident beam geometry ͑copropagating and counterpropagating͒, substrate ͑metal and dielectric materials͒, and thin-film structures, on the SFG spectra are discussed in the following paper. 46 In the present study, the incident laser beam angles for the visible and IR beams are set at 65°and 50°, respectively. Changing these angles will affect the L factors and consequently affect the simulated spectral features at different film thicknesses.…”

Section: E Extension To Other Model Systemsmentioning

confidence: 99%

“…This paper focuses on the modeling, calculation, and resulting theoretical spectral features, while a detailed comparison of the simulated and actual experimental spectra for different thin-film systems are presented in a subsequent paper. 46 The source codes for the model calculation are available from the authors on request. We anticipate that this will aid the understanding and further application of SFG spectroscopy to thin-layer system.…”

Section: Introductionmentioning

confidence: 99%

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Interference effects in the sum frequency generation spectra of thin organic films. I. Theoretical modeling and simulation

Davies

2010

The Journal of Chemical Physics

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A general theoretical calculation is described for predicting the interference effect in the sum frequency generation ͑SFG͒ spectra from a model thin-film system as a function of film thickness. The calculations were carried out for a three-layer thin film consisting of an organic monolayer, a dielectric thin film of variable thickness, and a gold substrate. This system comprises two sources of SFG, namely, a resonant contribution from the monolayer/dielectric film interface and a nonresonant contribution from the dielectric film/gold interface. The calculation shows that both the spectral intensity and the shape of the SFG spectra vary significantly with the thickness of the dielectric layer due to interference effects in the thin film. The intensity changes at a particular frequency were explained in terms of the changes in the local field factors ͑L factors͒ as a function of the dielectric film thickness. The L factor for each beam changes periodically with the thickness of the dielectric film. However, the combined L factor for the three beams shows complicated thickness dependent features and no clear periodicity was found. On the other hand, if the susceptibilities of both the resonant and nonresonant terms are fixed, changes in the spectral shape will be mainly due to changes in the phase differences between the two terms with the film thickness. The interference behavior also depends strongly on the polarization combinations of the sum frequency, visible, and infrared beams. A general method is provided for predicting changes in the spectral shapes at different film thicknesses by taking into account the relative intensities and phases of the SFG signals from the two interfaces. The model calculation provides important insights for understanding the nonlinear optical responses from any thin-film system and is an essential tool for quantitatively revealing the nonlinear susceptibilities, which are directly related to the actual structure of the interfacial molecules from the observed SFG spectra after quantitative removal of the L factors.

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“…The normalized interferogram, J (t IR ), contains the desired spectroscopic information. Equation10 shows that there are three contributions to the measured intensity: the LO intensity, which is independent of t IR and is the first term, the signal from the sample, which slowly varies with t IR and the third term that describes the interference. Theamplitude of the interference signal scales with the square root of the LO intensity and can consequently be increased by raising I LO .…”

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confidence: 99%

Detecting weak signals from interfaces by high accuracy phase-resolved SFG spectroscopy

Thämer

Campen

Wolf

2018

Phys. Chem. Chem. Phys.

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Much work over the last 25 years has demonstrated that the interface-specific, alloptical technique, vibrational sum frequency generation (v-SFG) spectroscopy, is often uniquely capable of characterizing the structure and dynamics of interfacial species. The desired information in such a measurement is the complex second order susceptibility which gives rise to the nonlinear response from interfacial molecules. The ability to detect molecular species yielding only small contributions to the susceptibility is meanwhile limited by the precision by which the spectral phase and amplitude can be determined.In this study we describe a new spectrometer design that offers unprecedented phase and amplitude accuracy while significantly improving the sensitivity of the technique.Combining a full collinear beam geometry with a technique enabling the simultaneous measurement of the complex sample and reference spectrum, uncertainties in the reference phase and amplitude are shown to be greatly reduced. Furthermore, we show that using balanced detection, the signal to noise ratio can be increased by one order of magnitude. The capabilities of the spectrometer are demonstrated by the isolation of a small isotropic surface signal from the bulk dominated nonlinear optical response 1 arXiv:1808.04255v1 [physics.optics] 13 Aug 2018 of z-cut quartz. The achieved precision of our spectrometer enables measurements not currently feasible in v-SFG spectroscopy.

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Interference effects in the sum frequency generation spectra of thin organic films. II: Applications to different thin-film systems

Cited by 26 publications

References 43 publications

Quantitative determination of the nonlinear bulk and surface response from alpha-quartz using phase sensitive SFG spectroscopy

Quantitative determination of the nonlinear bulk and surface response from alpha-quartz using phase sensitive SFG spectroscopy

Interference effects in the sum frequency generation spectra of thin organic films. I. Theoretical modeling and simulation

Detecting weak signals from interfaces by high accuracy phase-resolved SFG spectroscopy

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