Holographic surface gratings in iron-doped lithium niobate

Abstract

Surface gratings associated with holographic volume gratings in photorefractive crystals of iron-doped lithium niobate have been studied using diffraction of a reflected probe beam and high-resolution phase-shifted interferometric profilometry. Both techniques show that the surface gratings exist in the form of periodical corrugations of the same period as that of the volume grating. The maximum amplitude of the periodical surface relief measured by both techniques is close to 6.5 nm. We also demonstrated that the periodical electric forces on the surface were capable of assembling polystyrene microspheres along the fringes of the grating. Large amplitude of the periodic electric field (1.6×104 V/cm) is associated with the photogalvanic effect.

Recent Achievements on Photovoltaic Optoelectronic Tweezers Based on Lithium Niobate

“…The first works on PVT reported their ability to trap and pattern micrometric particle [33,34] and it is in this subject where the field has reached a greater maturity. First experiments demonstrated the manipulation of dielectric and metallic micro-and nanoparticles using x-or y-cut lithium niobate crystals, i.e., substrates with the polar axis parallel to the surface [17,34].…”

Optoelectronic tweezers under arbitrary illumination patterns: theoretical simulations and comparison to experiment

“…The procedure does not require electrodes and it is usually called photovoltaic or, more generally, optoelectronic tweezers. The number of experimental works showing the capabilities of optoelectronic tweezers has been rapidly increasing in the last few years [4][5][6][7][9][10][11][12]. Different dielectric and metallic nanoparticles, neutral or charged, have been used to generate the particle patterns showing the universality of the method.…”

“…An emergent methodology of this type [4][5][6][7] uses light-induced space charge fields generated in photorefractive materials by inhomogeneous illumination [8]. The space charge fields responsible for particle trapping are particularly large in PR crystals exhibiting a large photovoltaic effect such as Fe:LiNb03.…”

Photovoltaic tweezers an emergent tool for applications in nano and bio-technology

“…A number of different approaches have been proposed and explored including conventional optical tweezers or electrokinetical methods. In the last years a new optoelectric technique for particle manipulation, the so called photovoltaic (PV) tweezers (or photorefractive tweezers), has been proposed and demonstrated [1][2][3]. It relies in the bulk photovoltaic effect (PVE) [4], a singular phenomenon which appears in some crystalline ferroelectric materials (doped LiNbO 3 clearly highlighting) when properly doped (mainly with Fe).…”