An overview of the work recently conducted by our group on the development and applications of photovoltaic tweezers is presented. It includes the analysis of the physical basis of the method and the main achievements in its experimental implementation. Particular attention will be paid to the main potential applications and first demonstrations of its use in nano- and bio-technology. Specifically: i) fabrication of metallic nanoestructures for plasmonic applications, ii) development of diffractive components, iii) manipulation and patterning (1D and 2D) of various types of bio-objects (spores or pollen…) and iv) effects of PV fields of LiNbO<sub>3</sub> in tumour cells.
The optical damage behaviour of different LiNbO<sub>3</sub> optical waveguides has been experimentally studied by measuring the intensity output of a single beam as a function of the intensity input. Parallel measurements of photovoltaic currents have been carried out as a function of the input intensity and they have been correlated with the optical damage data. The following LiNbO<sub>3</sub> guides have been studied and compared: proton exchanged (PE) belonging to the phases alpha, beta<sub>1</sub>, beta<sub>2</sub> and reverse proton exchanged (RPE), and Zn in-diffused waveguides. The greatest intensity thresholds for optical damage, about 2x10<sup>3</sup> times greater than that of the substrate, have been obtained in RPE guides (they support ordinary polarization and have similar nonlinear optic activity as the substrate) and beta<sub>2</sub> guides which support extraordinary polarization (they have no nonlinear optic activity). On the other hand, the lowest photovoltaic currents have been measured in beta<sub>1,2</sub>-phases. As a function of the light intensity, the photovoltaic current exhibits a superlinear behaviour, strong in alpha-phase and weaker in Zn in-diffused and RPE guides. The results for optical damage are discussed in connection with those of photovoltaic currents, paying particular attention to the main mechanisms involved.