Alin Marian Apetrei

Crystal structure under pressure of geometrically frustrated pyrochlores

We have studied by x-ray synchrotron diffraction under high pressure five pyrochlore compounds: Tb2Ti2O7 (up to 42 GPa), Tb2Sn2O7 and Tb2Mo2O7 (up to 35 GPa), Gd2Mo2O7 and (Tb0.8La0.2)2Mo2O7 (up to 10 GPa). At ambient pressure all compounds crystallize in the cubic symmetry group. This structure is stable for all compounds in the investigated pressure range. All three compounds having Mo as transition metal are described by the same equation of state, with the same bulk modulus B0 = 149. The bulk modulus is smaller in the Mo pyrochlores than in the Ti and Sn ones, in contrast with a priori expectations.

Light transmission in multiple or single subwavelength trefoil channels of microstructured fibers

We evaluate the trefoil channels present between the holes of microstructured fibers as a potential dense array of small waveguides. In channels with an inner radius of 330nm, calculations indicate possible propagation with a mode waist of ~350nm at lambda=670nm, near to the diffraction limit. Actual measurements have been performed on a 1-meter fiber section, with injection by a microlensed fiber and mapping of output by near-field scanning optical microscopy. They show that light can be output in individual channels or in several of them, depending on the injection. The observed waist is ~500nm, possibly due to experimental widening. Estimated propagation losses are <20dB/m. Since each channel occupies only 2microm2, this structure opens a way to dense parallel optical processing.

Investigation of magnetic fluctuations in Tb2Sn2O7 ordered spin ice by high-resolution energy-resolved neutron scattering

We have studied magnetically frustrated Tb

Realistic Reversible Magnetization Component in Preisach-Type Models

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A dense array of small coupled waveguides in fiber technology: trefoil channels of microstructured optical fibers

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Study of ferromagnetic–spin glass threshold in R2Mo2O7 by high-pressure neutron diffraction and µSR

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Intermodal interferences in a multimode highly asymmetric two-core microstructured optical fiber

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Two geometrically frustrated magnets studied by neutron diffraction

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Broadband integrated beam splitter using spatial adiabatic passage

by neutron diffraction and high resolution energy-resolved neutron scattering. At 0.1 K, we observe short range magnetic correlations with a typical scale of 4 \AA, close to the near neighbor distance between Tb

Anomalous angular dispersion in lithium niobate one-dimensional waveguide array in the near-infrared wavelength range

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