Optical limiting properties of surface functionalized nanodiamonds probed by the Z-scan method.

This work focuses on the optical limiting behavior of surface modified nanodiamonds (DNDs) namely, amino-terminated DNDs (DND-NH2) and hydrogen-terminated DNDs (DND-H). Their relevant nonlinear optical properties for optical limiting are compared to those of unfunctionalized DNDs. The optical limitation is characterized by means of nonlinear transmittance, Z-scan, and scattered intensity assessments when submitted to a nanosecond pulsed Nd:YAG laser operating at a wavelength of 532 nm. It is stated that the largest nonlinear attenuation is attributed to the DND-H system, whereas the exceedingly low threshold values for optical limiting for the DND-H and the DND-NH2 systems is attributed to their negative electron affinity character (NEA). Using Z-scan experiments, it is shown that nonlinear refraction combined with a significant nonlinear absorption predominates in the DND-H suspension, while the pure thermal origin of the nonlinear refractive index change is conjectured in the case of the DNDs. Besides, an amazing valley to peak profile was measured on DND - NH2indicating an unexpected positive sign of the nonlinear refraction coefficient. In addition, a stronger backscattered intensity signal is highlighted for the unfunctionalized DNDs through nonlinear scattering measurements.