Spatial phase filtering based on the intensity-dependent refractive index of PbS nanocomposite film.

We demonstrate the use of stable films containing PbS nanocrystals as media for self-adaptive phase filtering in phase contrast imaging of transparent objects by a cost-effective exploitation of nonlinear optical refraction in a simple, all-optical, and self-adjusting 4f imaging system. The optical nonlinearity is characterized by z-scan technique using a continuous wave He-Ne laser as the excitation source. The mechanism of nonlinearity in this case is mainly due to the nonlocal thermo-optical interaction between the laser beam and the sample.

Nonlinear optical properties of free standing films of PbS quantum dots in the nonresonant femtosecond regime.

Devices based on optical technology for high speed communication networks require materials with large nonlinear optical response in the ultrafast regime. Nonlinear optical materials have also attracted wide attention as potential candidates for the protection of optical sensors and eyes while handling lasers. Optical limiters have a constant transmittance at low input influence and a decrease in transmittance at higher fluences and are based on a variety of mechanisms such as nonlinear refraction, nonlinear scattering, multiphoton absorption and free carrier absorption.

Two-photon-assisted excited state absorption in nanocomposite films of PbS stabilized in a synthetic glue matrix.

Strong nonlinear absorption is observed in nanocomposite films containing PbS nanocrystals of mean size of 3.3 nm stabilized in a commercial poly(vinyl acetate) glue by a novel and simple chemical route of synthesis. A significant blueshift of the optical absorption edge indicates strong quantum confinement.