Modes of wide-aperture acousto-optic diffraction in a uniaxial birefringent crystal

The recent renaissance of the light microsope is fueled in part by technological advances in components on the periphery of the microscope, such as the laser as illumination source, electronic image recording (video), computer assisted image analysis and the biochemistry of fluorescent dyes for labeling specimens. After great progress in these peripheral parts, it seems timely to examine the optics itself and ask how progress in the periphery facilitates the use of new optical components and of new optical designs inside the microscope. Some results of this fruitful reflection are presented in this symposium.We have considered the polarized light microscope, and developed a design that replaces the traditional compensator, typically a birefringent crystal plate, with a precision universal compensator made of two liquid crystal variable retarders. A video camera and digital image processing system provide fast measurements of specimen anisotropy (retardance magnitude and azimuth) at ALL POINTS of the image forming the field of view. The images document fine structural and molecular organization within a thin optical section of the specimen.

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Laser Pulse Shortening via Zero-Dispersion Phase Matching of Parametric Raman Interactions in Crystals

Crystals ◽

10.3390/cryst11010019 ◽

2020 ◽

Vol 11 (1) ◽

pp. 19

Author(s):

Sergei N. Smetanin ◽

Michal Jelínek ◽

Dmitry P. Tereshchenko ◽

Mikhail N. Ershkov ◽

Václav Kubeček

Keyword(s):

Laser Pulse ◽

Short Pulse ◽

Matching Condition ◽

Phase Matching ◽

Dispersion Phase ◽

Birefringent Crystal ◽

Raman Lasers ◽

Birefringent Crystals ◽

Phase Matching Condition ◽

Ultra Short Pulse

We propose and study the conditions of zero-dispersion phase matching for parametric Raman interactions in birefringent crystals differing by anisotropy of zero-dispersion wavelength and allowing for the spectral tuning of the zero-dispersion phase-matching condition. We choose a highly birefringent crystal of calcite having a wide zero-dispersion anisotropy range for the demonstration of new effects of laser pulse shortening in parametric Raman lasers with spectrally tunable zero-dispersion phase matching. We demonstrate the anti-Stokes (1168 nm) and multi-Stokes (1629 nm) picosecond pulse shortening and self-separation of single 80-ps ultra-short pulse from the zero-dispersion phase-matched parametric Raman lasers that are based on the calcite crystal without using any electro-optical device.

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Elastic wave velocity and electrical conductivity in a brine-saturated rock and microstructure of pores

Earth Planets and Space ◽

10.1186/s40623-019-1112-9 ◽

2019 ◽

Vol 71 (1) ◽

Author(s):

Tohru Watanabe ◽

Miho Makimura ◽

Yohei Kaiwa ◽

Guillaume Desbois ◽

Kenta Yoshida ◽

...

Keyword(s):

Electrical Conductivity ◽

Elastic Wave ◽

Wave Velocity ◽

High Pressures ◽

Seismic Velocity ◽

Volume Fraction ◽

Elastic Wave Velocity ◽

Fluid Volume ◽

Sem Observation ◽

Wide Aperture

AbstractElastic wave velocity and electrical conductivity in a brine-saturated granitic rock were measured under confining pressures of up to 150 MPa and microstructure of pores was examined with SEM on ion-milled surfaces to understand the pores that govern electrical conduction at high pressures. The closure of cracks under pressure causes the increase in velocity and decrease in conductivity. Conductivity decreases steeply below 10 MPa and then gradually at higher pressures. Though cracks are mostly closed at the confining pressure of 150 MPa, brine must be still interconnected to show observed conductivity. SEM observation shows that some cracks have remarkable variation in aperture. The aperture varies from ~ 100 nm to ~ 3 μm along a crack. FIB–SEM observation suggests that wide aperture parts are interconnected in a crack. Both wide and narrow aperture parts work parallel as conduction paths at low pressures. At high pressures, narrow aperture parts are closed but wide aperture parts are still open to maintain conduction paths. The closure of narrow aperture parts leads to a steep decrease in conductivity, since narrow aperture parts dominate cracks. There should be cracks in various sizes in the crust: from grain boundaries to large faults. A crack must have a variation in aperture, and wide aperture parts must govern the conduction paths at depths. A simple tube model was employed to estimate the fluid volume fraction. The fluid volume fraction of 10−4–10−3 is estimated for the conductivity of 10−2 S/m. Conduction paths composed of wide aperture parts are consistent with observed moderate fluctuations (< 10%) in seismic velocity in the crust.

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