Three-dimensional imaging of chemical bond orientation in liquid crystals by coherent anti- Stokes Raman scattering microscopy

Saar, Brian G.; Park, Heung‐Shik; Xie, Xin; Lavrentovich, Oleg D.

doi:10.1364/oe.15.013585

Cited by 34 publications

(28 citation statements)

References 20 publications

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“…With improved signal-to-noise ratio and a more robust optical model, a fully 3D director profile reconstruction will be possible. Comparing ONT with other imaging techniques such as coherent anti-Stokes Raman scattering 20,21 and fluorescence confocal polarizing microscopy 22,23 , ONT's strength lies in its ultrahigh resolution within ∼500 nm of the surface, the non-necessity of doping the sample with a dye and the ability to study high-birefringence materials. Of course, ONT has two potential drawbacks: it requires a free upper surface and the fibre can be invasive, depending on the material being studied.…”

Section: Lettersmentioning

confidence: 99%

Optical nanotomography of anisotropic fluids

et al. 2008

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The physical properties of anisotropic fluids can be manipulated on very short length scales of 100 nm or less by appropriate treatment of the confining substrate(s) 1,2 . This facilitates the use of ordered fluids in a variety of scientific endeavours and applications. Although future advances will require a complete understanding of their structure at the nanoscale level, high-resolution three-dimensional optical imaging of the fluid's molecular orientation profile is beyond the reach of extant techniques 3 . Here, we report a powerful imaging approach based on the collection of transmitted light in the far field that is emitted from a light source with a subwavelength aperture. We acquire high-resolution images by raster-scanning, at multiple heights, an optical fibre immersed inside a thin layer of anisotropic fluid, thereby facilitating the visualization of the fluid's structure with a resolvable volume ∼1/500 of that attainable by current methods. This novel technique offers the intriguing possibility of three-dimensional nanoscale reconstruction of a variety of soft materials, here the first direct visualization and measurement of the liquid-crystal molecular orientation relaxation length.The idea of using a subwavelength metal-coated fibre aperture to investigate a surface with high resolution was proposed initially by Synge 4 ; this has evolved into the technique of near-field optical microscopy 5 for two-dimensional (2D) imaging. Here, we present an entirely new imaging approach that involves the use of polarized light, emitted from a tapered optical fibre immersed in an anisotropic medium, in the far field to investigate molecular orientation in three dimensions at nanoscale levels. As there are no significant scattering sources due to dielectric inhomogeneities, the near-field light does not scatter in the customary manner, but instead decays exponentially with distance and is not detected downstream. Instead, the light that reaches the detector from the fibre aperture consists of small-wave-vector Fourier components, and is retarded by a phase δ as it propagates through the continuous birefringent fluid medium. By carrying out in-plane (xy) scans inside the sample at a series of heights z i above the surface, we obtain intensity matrix slices, from which we extract information about the fluid's local optical properties. The initial image (i = 1) is acquired by raster-scanning the fibre at height z 1 = h 1 (Fig.

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Section: Lettersmentioning

confidence: 99%

Optical nanotomography of anisotropic fluids

et al. 2008

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Section: Methodsmentioning

confidence: 99%

“…Coherent anti-Stokes Raman scattering (CARS) microscopy provides excellent sensitivity, high spatial resolution and inherent chemical specificity, enabling the characterization of chemical species or biological components noninvasively, within complex heterogeneous system in material science [1,2] and biology. [3] Due to the coherent addition of both resonant and nonresonant background (NRB) contributions, vibrational resonances in CARS spectra show apparent frequency shifts and differences in relative peak amplitude compared to the spontaneous Raman spectra.…”

Section: Introductionmentioning

confidence: 99%

Fast extraction of resonant vibrational response from CARS spectra with arbitrary nonresonant background

Liu

Lee

Cicerone

2009

J Raman Spectroscopy

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We describe a new, robust method of numerically extracting equivalent Raman spectra from coherent anti-Stokes Raman scattering (CARS) spectra. The extraction procedure requires no a priori information regarding the vibrational resonances or the shape of the nonresonant background (NRB). The method we present here is robust to situations where the NRB is not spectrally flat, and is accurate over a wide range of signal-to-background ratios. This simple and quick computation method, which relies primarily on a small number of fast Fourier transforms, could reasonably be used in conjunction with spectral imaging, where millions of spectra must be analyzed.

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“…1(c)]. Using such methods, high molecular organization has been evidenced in water molecules between phospholipid layers [11], CN bonds of liquid crystals [12,13], CH bonds of polyglucan chains in cellulose [14], and in various symmetry modes of zeolite crystals [15]. Monitoring the CH 2 vibrational stretching bond in lipids has shown considerable level of information on lipid order within artificial multilayers [16,17], where the measured modulation was used to retrieve quantitative information on sub-diffraction molecular orientational order behaviors, in particular, its mean orientation and angular distribution shape [17].…”

Section: Introductionmentioning

confidence: 99%

High-speed polarization-resolved coherent Raman scattering imaging

Hofer¹,

Balla²,

Brasselet³

2017

Optica

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Polarization-resolved coherent Raman scattering (polar-CRS) provides rich information on molecular orientational organization, with the strong advantages of being a label-free and chemically specific imaging method. Its implementation, however, strongly reduces the imaging acquisition rate, due to limits imposed by polarization tuning. Here we demonstrate fast-polar-CRS imaging based on combined electro-optic polarization and acousto-optic amplitude modulations, applicable to both stimulated Raman scattering and coherent anti-Stokes Raman scattering imaging. The proposed scheme adds polarization information without compromising the capacities of regular CRS intensity imaging; increases the speed of orientational imaging by two orders of magnitude as compared with previous approaches; and does not require post-processing analyses. We show that this method permits sub-second time-scale imaging of lipid order packing and local lipid membrane deformations in artificial lipid multilayers, but also in red blood cell ghosts, demonstrating its high sensitivity down to a single lipid bilayer membrane.

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Three-dimensional imaging of chemical bond orientation in liquid crystals by coherent anti- Stokes Raman scattering microscopy

Cited by 34 publications

References 20 publications

Optical nanotomography of anisotropic fluids

Optical nanotomography of anisotropic fluids

Fast extraction of resonant vibrational response from CARS spectra with arbitrary nonresonant background

High-speed polarization-resolved coherent Raman scattering imaging

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