Nonlinear optical components for all-optical probabilistic graphical model.

The probabilistic graphical models (PGMs) are tools that are used to compute probability distributions over large and complex interacting variables. They have applications in social networks, speech recognition, artificial intelligence, machine learning, and many more areas. Here, we present an all-optical implementation of a PGM through the sum-product message passing algorithm (SPMPA) governed by a wavelength multiplexing architecture.

Intramolecular vibrational coupling contribution to temperature dependence of vibrational mode frequencies.

High-frequency vibrational modes in molecules in solution are sensitive to temperature and shift either to lower or higher frequencies with the temperature increase. These frequency shifts are often attributed to specific interactions of the molecule and to the solvent polarization effect. We found that a substantial and often dominant contribution to sensitivity of vibrational high-frequency modes to temperature originates from anharmonic interactions with other modes in the molecule.

A method for determining small anharmonicity values from 2DIR spectra using thermally induced shifts of frequencies of high-frequency modes.

The off-diagonal anharmonicity for a pair of vibrational modes, determined as a shift of their combination level, Δ(12), can be linked to the molecular structure via modeling. The anharmonicity, Δ(12), also determines the amplitude and shape of the cross-peak between modes 1 and 2 measured using 2DIR spectroscopy. For large anharmonicities, the anharmonicity value can be readily obtained from the shape of the cross peak.