The CdSe quantum dots have been synthesized and their optical properties have been investigated at 775 nm. It was
found that both linear absorption and linear scattering were negligible in these colloidal cadmium selenide quantum dots
when the light intensity was weak. A strong light-induced scattering was observed when a strong 150 fs Ti:Sapphire
laser incident on the sample. The physical origins and the possible photonic applications of this phenomenon were
investigated.
Colloid CdSe quantum dots have been synthesized and their photonic application as a two-wave
mixing medium has been demonstrated. Large energy transfer from a strong pump beam to a weak
signal beam has been observed and possible application in group velocity manipulation has been
discussed.
Pump controllable nanosecond optical delay has been demonstrated using colloid CdSe quantum dots. The delay time
can be easily manipulated by a pump beam. The physical mechanism for the two-wave mixing based group velocity
manipulation has been investigated.
We give the analytical expressions of the nonlinear transmittance of materials through an aperture in the far field with finite aperture size. The result can be used under the conditions of and . Based on this equation, the nonlinear refractive index coefficients of some nanomaterials from both the closed I-scan and Z-scan measurements at 800 nm and 1064 nm were extracted, respectively. The obtained values from I-scan measurements are comparable with those from the Z-scan measurements. The nonlinear absorptions of these materials were also studied by fulfilling the open I-scan and Z-scan measurements. The advantages of I-scan technology were discussed.
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.
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