First approach to characterize tilts through multiple pistons in the classical Ronchi test.

In this work, it is shown how a tilt can be introduced into a segmented surface through several piston terms, by using the classical Ronchi test. We have developed tilt error simulations by adding multiple constant terms to each point on the sagitta surface of a segment using ray tracing. Thereby a comparison between simulated Ronchigrams for piston and tilt has been performed for two adjacent segments, so that it is possible to appreciate the tilt and piston effects on the shape of the patterns. As a result, we show the behavior of the central maximum of the fringes in the presence of tilt and/or piston. Additionally we present evidence of introducing tilting without changing the surface shape by adding multiple pistons, and a description of how to characterize both piston and tilt using the Ronchi test.

Ultrafast nonlinear optical response of photoconductive ZnO films with fluorine nanoparticles.

The absorptive and refractive third order nonlinear optical properties exhibited by a ZnO thin solid film with fluorine nanoparticles were studied with picosecond and femtosecond pulses using different techniques. We were able to evaluate the photoconductivity of the material and the quenching of the induced birefringence observed in the presence of two-photon absorption. The samples were prepared by a chemical spray deposition technique. In order to investigate the different contributions of the third order nonlinearities of the film, we analyzed the vectorial self-diffraction effect and the optical Kerr transmittance observed in the sample. A dominantly absorptive nonlinearity was measured at a 532 nm wavelength with 50 ps pulses, while nonlinear refraction was found to be negligible in this regime. On the other side, a pure electronic refractive third order nonlinearity without the contribution of nonlinear absorption was detected at 830 nm with 80 fs pulse duration. A quasi-instantaneous optical response and a strong enhancement in the ultrafast nonlinear refraction with the inhibition of the picosecond two-photon absorption mechanism were measured for the case of the femtosecond excitation.