Nonlinear refraction and nonlinear absorption measurements of CdTe nanoscale materials embedded in PMMA using ultrafast laser pulse

Experimental investigations have shown that CdTe semiconductor microcrystals possess large third-order susceptibilities and short response times at both resonant and non-resonant wavelengths (580 nm and 1064 nm). These excellent properties indicate their potential applications in nonlinear photonic devices. In this work, we measured the nonlinear refraction and nonlinear absorption coefficients of CdTe nanocrystals using Z-scan method at 800 nm. Application in optical limiting of the sample was also demonstrated. The samples used were made by ball milling process and then embedded in polymethylmethacrylate (PMMA). The two photon absorption (TPA) and nonlinear refraction were evaluated from the normalized transmittance with open aperture and with closed-aperture, respectively. Optical limiting studies were carried out as a function of input intensity at 800 nm. The input intensities were varied from 5 to 70 kW/cm2. The transmitted power was collected by a photo-detector through a 2-mm diameter aperture. We found that the transmitted power decreased significantly over the input intensity range of 10-20 kw/cm2.