Efficient phase-matched second-harmonic generation and sum-frequency mixing in urea

Halbout, J.‐M.; Blit, S.; Donaldson, William R.; Tang, C. L.

doi:10.1109/jqe.1979.1069900

Cited by 179 publications

(44 citation statements)

References 11 publications

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“…68 Urea is a uniaxial crystal, with only two unique refractive indices, and Sellmeier expansions have been reported for both unique directions, with excellent agreement obtained between these independent measurements. 69,70 Using the published Sellmeier coefficients from Halbout et al, 70 experimental refractive indices were extrapolated to zero frequency, and comparison is made with our x-ray fitted results and those from ab initio calculations by Reis et al 14 in Table III. The correspondence between the experimental refractive indices extrapolated to infinite wavelength and those obtained from the x-ray fitted wave function is quite remarkable, showing that not only has the polarizability changed significantly from the CPHF results but in a manner such that the experimental results have been almost quantitatively reproduced.…”

Section: B Ureamentioning

confidence: 92%

Effective molecular polarizabilities and crystal refractive indices estimated from x-ray diffraction data

Whitten

Jayatilaka

Spackman

2006

The Journal of Chemical Physics

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Articles you may be interested inAlthough it was proposed some time ago that ͑hyper͒polarizabilities might be estimated from the results of x-ray charge density refinements, early results were unconvincing. In this work we show that the one particle density obtained from the usual multipole refinement model does not contain sufficient information to determine these response properties and instead pursue the "constrained wave function" approach of fitting to x-ray structure factors. Simplified sum-over-states expressions are derived for determining the dipole polarizability from these wave functions, and these clearly show that the earlier work ignored important two-electron expectation values for the dipole polarizability, and two-and three-electron terms for ␤, etc. Correction factors for the simplified sum-over-states polarizability tensors from the constrained wave function are obtained by calibration against coupled Hartree-Fock ab initio results to yield in-crystal effective polarizability tensors. Results obtained for benzene, urea, and 2-methyl-4-nitroaniline demonstrate that the effective molecular polarizabilities clearly include the effects of intermolecular interactions and electron correlation, especially for urea where the effects on the polarizability are known to be quite large. We also carefully consider the way in which the linear bulk susceptibility, ͑1͒ , and refractive indices are determined from the x-ray fitted polarizabilities, employing three models based on a rigorous treatment of the local field. Incorrect results are obtained for the sort of molecules that are of interest in nonlinear optical applications if the molecules are approximated by single point dipoles. In contrast, the use of Lorentz-factor tensors averaged over several sites yields excellent results, with refractive indices obtained using this model in remarkably good agreement with optical measurements extrapolated to zero frequency.

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Section: B Ureamentioning

confidence: 92%

Effective molecular polarizabilities and crystal refractive indices estimated from x-ray diffraction data

Whitten

Jayatilaka

Spackman

2006

The Journal of Chemical Physics

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“…This sample provides ample TPEF signal throughout a broad range of wavelengths and exhibits sub-cellular features such as nuclei and cell membranes. 18,19 and were imaged to test the system in the SHG modality. Figure 5.…”

Section: Samplesmentioning

confidence: 99%

Adaptive nonlinear microscopy for whole tissue imaging

et al. 2013

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Nonlinear microscopy is capable of imaging biological tissue non-invasively with sub-cellular resolution in three dimensions. For efficient multiphoton signal generation, it is necessary to focus high power, ultra-fast laser pulses into a volume of femtolitres. Aberrations introduced either by the system's optical setup or the sample under investigation cause a broadening of the diffraction limited focal spot which leads to loss of image intensity and resolution. Adaptive optics provides a means to compensate for these aberrations and is capable of restoring resolution and signal strength when imaging at depth. We describe the use of a micro-electro-mechanical systems (MEMS) deformable membrane mirror in a multiphoton adaptive microscope. The aberration correction is determined in a wavefront sensorless approach by rapidly altering the mirror shape with a random search algorithm until the fluorescence or second harmonic signal intensity is improved. We demonstrate the benefits of wavefront correction in a wide-variety of samples, including urea crystals, convallaria and organotypic tissue cultures. We show how the optimization algorithm can be adjusted, for example by including a bleaching compensation, to allow the user to switch between different imaging modalities, producing a versatile approach to aberration correction.

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“…s (12)(13)(14), subscri pts 1 and 2 refer to the fundamental and second harmoni c fields and polarizations.…”

Section: Current Status Of Nonlinear Organic Materialsmentioning

confidence: 99%

Nonlinear Optical and Electro-optical Properties of Biopolymers

Kurtz¹,

Kozikowski²,

Wolfram³

1987

Springer Proceedings in Physics

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Efficient phase-matched second-harmonic generation and sum-frequency mixing in urea

Cited by 179 publications

References 11 publications

Effective molecular polarizabilities and crystal refractive indices estimated from x-ray diffraction data

Effective molecular polarizabilities and crystal refractive indices estimated from x-ray diffraction data

Adaptive nonlinear microscopy for whole tissue imaging

Nonlinear Optical and Electro-optical Properties of Biopolymers

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