Second- and third-order nonlinear optical properties of bis-chalcone derivatives

Bis-chalcone derivatives: 2,5-bis(benzylidene)-cyclopentanone (CP-DBA), 2,5-bis(4-methoxy-benzylidene)-cyclopentanone (CP-POME), 2,5-bis(4-isopropyl-benzylidene)-cyclopentanone (CP-ISO) and 2,5-bis(cinnamylidene)-cyclopentanone (CP-CAL) are synthesized by Claisen–Schmidt reaction and characterized using, FT-IR, 1H NMR, 13C NMR, and mass spectroscopic techniques. The second- and third-order nonlinear optical properties of these samples are studied using second harmonic generation and nanosecond open-aperture Z-scan methods. CP-POME has shown a very high second harmonic generation (SHG) efficiency (5.3 times that of urea). These molecules reveal a strong third-order nonlinear absorption (NLA) that is of optical limiting type, due to their peculiar D–π–A–π–D structure that leads to high polarization of the delocalized electron cloud. CP-CAL exhibits highest NLA activity with a β coefficient of 1 × 10−10 m/W. Through numerical simulations, the mechanism of NLA is found to be a two-photon absorption process in the case of all the samples.