Non-linear optical anomalies near the phase transitions in polysiloxane chromophore incorporated within an oligoetheracrylate photopolymer matrix

Abstract

The photoinduced optical second-harmonic generation (PISHG) in polysiloxane (PX) chromophore incorporated within an oligoetheracrylate photopolymer matrix was investigated as a function of temperature within the 4.2–300 K temperature range. The addition of PX chromophore leads to an enhancement of the local non-centrosymmetric charge density distribution determining optical second-harmonic generation. Two maxima of the PISHG signals were observed at temperatures of ~ = 20 and 126 K. The DSC data give the positions of the maxima at 36 and 132 K. This temperature discrepancy may be a consequence of different contributions of the electron–vibration sub-system to the observed phase transformations. An explanation of the observed temperature anomalies is given within a quantum chemical approach.