Size-dependent off-resonant nonlinear optical properties of gold nanoparticles and demonstration of efficient optical limiting

There are different possibilities for the applications of gold nanoparticles in various areas of optoelectronics. Here we report the nonlinear optical studies of chemically prepared gold nanoparticle suspensions using femtosecond pulses. The nonlinear refractive indices, nonlinear absorption coefficients, and saturated intensities of the nanoparticles of different sizes are measured at the wavelengths of 400 and 800 nm. We also demonstrate the optical limiting of 800 nm, 60 fs pulses during propagation through these suspensions. The competition of saturable and reverse saturable absorption in the case of 400 nm radiation is analyzed. The intensity-dependent transformation from saturable absorption to reverse saturable absorption indicates that these gold nanoparticles can be useful for eye protection, pulse shaping and passive mode locking.

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