Dependence of the optical limiting behavior on the medium position and the beam-waist radius in the refractive optical limiters

We study numerically the optical limiting properties of the refractive optical limiting devices based on the self-focusing and defocusing phenomena, and examine the effects of the installation position of the nonlinear media and the waist size of the incident Gaussian beam on the operating performances of the refractive optical limiters. Our results show that the optical limiting curves of the refractive optical limiters assume a vibrating decaying waveform. The optical limiting threshold and the clamped output value of the optical limiters are dependant on the installation position of the sample and the convergence of the incident Gaussian beam to a great extent. When the sample position is given, the smaller the beam-waist radius, the better the optical limiting performance. When the waist radius of the incident light keeps constant, an optimum location of the nonlinear sample can be found in the system. With the fluctuation of the waist size, however, the optimum location changes within a small range. For a self-focusing (self-defocusing) optical limiter, the optimum optical limiting effect can be obtained when the nonlinear medium is positioned at a certain location within half a Rayleigh range in the left (right) side of the focal plane.