Highly efficient all-optical beam modulation utilizing thermo-optic effects.

Suspensions of plasmonic nanoparticles can diffract optical beams due to the combination of thermal lensing and self-phase modulation. Here, we demonstrate extremely efficient optical continuous wave (CW) beam switching across the visible range in optimized suspensions of 5-nm Au and Ag nanoparticles in non-polar solvents, such as hexane and decane. On-axis modulation of greater than 30 dB is achieved at incident beam intensities as low as 100 W/cm(2) with response times under 200 mu s, at initial solution transparency above 70%. No evidence of laser-induced degradation is observed for the highest intensities used. Numerical modeling of experimental data reveals thenuo-optic coefficients of up to -1.3 x 10(-3) /K, which. to our knowledge, is the highest observed to date in such nanoparticle suspensions. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement