We have performed single-shot time-resolved reflectivity measurements of the photo-reversible phase transition between k-and b-phases of Ti 3 O 5 nanoparticles at room temperature. These phase transitions are induced using nanosecond and millisecond laser pulses and are revealed by Raman spectroscopy. Upon nanosecond pulsed excitation, the k-to b-phase transition is detected in about 900 ns, whereas the b-to k-phase transition is noticed in less than 20 ns. The k-to b-phase transition induced by quasi continuous wave laser happens on the millisecond time scale. We propose a scenario that accounts very well for the observed phenomena.

We report on the observation of an efficient coherent up-conversion via third harmonic generation (THG) in Rb 0.94 Mn[Fe(CN) 6 ] 0.98 .0.3H 2 O material. Our THG measurements at fundamental wavelengths ranging from 1200 to 2400 nm show that, in this spectral range, the THG signal overcomes the signal generated by frequency doubling. This demonstrates that this material possesses significant third-order nonlinear optical (NLO) responses. Its effective χ (3) value is at least two orders of magnitude greater than α-Quartz. We also demonstrate that this material exhibits a broad thermal hysteresis loop around room temperature, which makes it possible to simultaneously photo-commute its linear and thirdorder nonlinear optical properties.

Second-harmonic and terahertz generation is performed in the Rb 0.94 Mn[Fe(CN) 6 ] 0.98 ·0.3H 2 O Prussian-blue analogue. Second-harmonic generation experiments are carried out between 1100 and 1700 nm and within the hysteresis loop of this compound. In the low-and high-temperature phases, our measurements indicate that the effective second-order nonlinear component (2) of this material is small, compared with α-quartz. However, in the high-temperature phase and

. Using density functional theory calculations, we were able to retrieve and to visualize these vibrations in both highspin and low-spin states. In both compounds, Raman spectra