Strong cavity coupling to molecular vibrations creates vibration-polaritons capable of modifying chemical reaction kinetics, product branching ratios, and charge transfer equilibria. However, the mechanisms impacting these molecular processes remain elusive. Furthermore, even basic elements determining the spectral properties of polaritons, such as selection rules, transition moments, and lifetimes are poorly understood. Here, we use two-dimensional infrared and filtered pump–probe spectroscopy to report clear spectroscopic signatures and relaxation dynamics of excited vibration-polaritons formed from the cavity-coupled NO band of nitroprusside. We apply an extended multi-level quantum Rabi model that predicts transition frequencies and strengths that agree well with our experiment. Notably, the polariton features decay ~3–4 times slower than the polariton dephasing time, indicating that they support incoherent population, a consequence of their partial matter character.

Saturable absorption, in which optical absorption decreases as the incident intensity increases, is commonly utilized in the visible and near-infrared for laser applications. In the mid-infrared, most vibrational transitions are too weak and optical fluences too low to achieve saturable absorption. In this work, we demonstrate saturable absorption in a narrow band centered at 1983 cm–1 in solution-phase W­(CO)6 with a readily accessible saturation fluence. Furthermore, in a system where coupling between the strongly absorbing vibrational mode of W­(CO)6 and an optical cavity gives rise to two polariton modes (i.e., the strong coupling regime), we demonstrate that saturation of the splitting between polariton peaks leads to a fluence-dependent cavity transmission with a saturation fluence that scales counterintuitively with the cavity length and molecular concentration.

<div> <div> <div> <p>Strong cavity coupling to molecular vibrations creates vibration-polaritons capable of modifying chemical reaction kinetics, product branching ratios, and charge transfer equilibria. However, the mechanisms impacting these molecular processes remain elusive. Furthermore, even basic elements determining the spectral properties of polaritons, such as selection rules, transition moments, and lifetimes, are poorly understood. Here, we use two-dimensional infrared and filtered pump–probe spectroscopy to report clear spectroscopic signatures and relaxation dynamics of excited vibration-polaritons formed from the cavity- coupled NO band of nitroprusside. We apply a multi-level quantum Rabi model that predicts transition frequencies and strengths that agree very well with our experiment. Notably, the polariton features decay ~3-4 times slower than the polariton dephasing time, indicating that they support incoherent population, a consequence of their partial matter character. Understanding the factors determining polariton population and dephasing lifetimes will impact polariton-modified energy transfer, photophysics, and chemistry. </p> </div> </div> </div>

Water adsorption experiments combined with vibrational and radiochemical analyses reveal significant differences in uptake of H2O over D2O, HDO, and HTO within metal organic nanotubes.

The Berreman effect, by which thin films of polar dielectric materials exhibit strong, narrow resonances near their longitudinal optic (LO) phonon frequency, results in strong material interactions with infrared radiation and offers tremendous potential for infrared nanophotonics. We report the first implementation of the LO-phonon-plasmon-coupling (LOPC) effect to actively tune the Berreman mode of a semiconductor thin film. Using time-resolved ultraviolet pump, infrared probe reflectance spectroscopy, we excite free carriers in a sub-infraredwavelength film of GaN and observe substantial shifts of the Berreman mode as a new, simple version of LOPC-based polariton tuning. We demonstrate resonance shifts (Δω) comparable to the resonance width (δω), realizing a respectable tuning figure of merit Δω/δω ≈ 0.7, and show that the shift can be modulated on a sub-nanosecond time scale. These results provide substantial promise for future ultrafast, wavelength-tunable infrared photonic devices and novel experimental designs for understanding phonon−polariton free-carrier interactions.

Hexagonal boron nitride (hBN) is a wide, indirect bandgap semiconductor that holds great promise for optoelectronic devices in the ultraviolet and midinfrared spectral regimes. The efficiency of optoelectronic devices is dominated by the dynamic behavior of photogenerated carriers. Here we report on the dynamics of photoexcited free carriers in exfoliated 10 B-enriched (99%) hBN at room temperature. Through implementation of ultrafast ultraviolet-pump−infrared-probe transient transmission spectroscopy, we identify two characteristic recombination rates. Initially, at high free carrier density, the pump fluence dependence is bimolecular with a characteristic rate constant of ∼2.0 × 10 −7 cm 3 /s. This is followed by an exponential recombination of the free carriers at a rate of ∼2.3 × 10 9 s −1 , which we assign to the influence of the impurities and defects in the lattice. These initial results offer insight into the radiative recombination processes for deep ultraviolet optoelectronic devices and toward realizing active control of mid-IR nanophotonic responses.

<div> <div> <div> <p>Strong cavity coupling to molecular vibrations creates vibration-polaritons capable of modifying chemical reaction kinetics, product branching ratios, and charge transfer equilibria. However, the mechanisms impacting these molecular processes remain elusive. Furthermore, even basic elements determining the spectral properties of polaritons, such as selection rules, transition moments, and lifetimes, are poorly understood. Here, we use two-dimensional infrared and filtered pump–probe spectroscopy to report clear spectroscopic signatures and relaxation dynamics of excited vibration-polaritons formed from the cavity- coupled NO band of nitroprusside. We apply a multi-level quantum Rabi model that predicts transition frequencies and strengths that agree very well with our experiment. Notably, the polariton features decay ~3-4 times slower than the polariton dephasing time, indicating that they support incoherent population, a consequence of their partial matter character. Understanding the factors determining polariton population and dephasing lifetimes will impact polariton-modified energy transfer, photophysics, and chemistry. </p> </div> </div> </div>

Enzyme function relies on the placement of chemistry defined by solvent and self-associative hydrogen bonding displayed by the protein backbone. Amyloids, long-range multi-peptide and -protein materials, can mimic enzyme functions...