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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on PrAgGe by Materials Project

PrAgGe crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Pr is bonded to six equivalent Ag and six equivalent Ge atoms to form a mixture of distorted face and edge-sharing PrAg6Ge6 cuboctahedra. There are three shorter (3.20 Å) and three longer (3.37 Å) Pr–Ag bond lengths. There are three shorter (3.12 Å) and three longer (3.46 Å) Pr–Ge bond lengths. Ag is bonded in a 9-coordinate geometry to six equivalent Pr and three equivalent Ge atoms. All Ag–Ge bond lengths are 2.68 Å. Ge is bonded in a 9-coordinate geometry to six equivalent Pr and three equivalent Ag atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1993

Spatiotemporal behavior and nonlinear dynamics in a phase conjugate resonator

The work described can be divided into two parts. The first part is an investigation of the transient behavior and stability property of a phase conjugate resonator (PCR) below threshold. The second part is an experimental and theoretical study of the PCR's spatiotemporal dynamics above threshold. The time-dependent coupled wave equations for four-wave mixing (FWM) in a photorefractive crystal, with two distinct interaction regions caused by feedback from an ordinary mirror, was used to model the transient dynamics of a PCR below threshold. The conditions for self-oscillation were determined and the solutions were used to define the PCR's transfer function and analyze its stability. Experimental results for the buildup and decay times confirmed qualitatively the predicted behavior. Experiments were carried out above threshold to study the spatiotemporal dynamics of the PCR as a function of Pragg detuning and the resonator's Fresnel number. The existence of optical vortices in the wavefront were identified by optical interferometry. It was possible to describe the transverse dynamics and the spatiotemporal instabilities by modeling the three-dimensional-coupled wave equations in photorefractive FWM using a truncated modal expansion approach.

Liu, Siuying Raymond↗