LiNbO3: A photovoltaic substrate for massive parallel manipulation and patterning of nano-objects

Abstract

The application of evanescent photovoltaic (PV) fields, generated by visible illumination of Fe:LiNbO 3 substrates, for parallel massive trapping and manipulation of micro-and nano-objects is critically reviewed. The technique has been often referred to as photovoltaic or photorefractive tweezers. The main advantage of the new method is that the involved electrophoretic and/or dielectrophoretic forces do not require any electrodes and large scale manipulation of nano-objects can be easily achieved using the patterning capabilities of light. The paper describes the experimental techniques for particle trapping and the main reported experimental results obtained with a variety of micro-and nano-particles (dielectric and conductive) and different illumination configurations (single beam, holographic geometry, and spatial light modulator projection). The report also pays attention to the physical basis of the method, namely, the coupling of the evanescent photorefractive fields to the dielectric response of the nano-particles. The role of a number of physical parameters such as the contrast and spatial periodicities of the illumination pattern or the particle deposition method is discussed. Moreover, the main properties of the obtained particle patterns in relation to potential applications are summarized, and first demonstrations reviewed. Finally, the PV method is discussed in comparison to other patterning strategies, such as those based on the pyroelectric response and the electric fields associated to domain poling of ferroelectric materials.

Recent Achievements on Photovoltaic Optoelectronic Tweezers Based on Lithium Niobate

“…The physical basis of PV tweezers for particle manipulation has been previously described in some detail [14,16]. Here, we will briefly summarize the main points.…”

“…It can reach very high values, up to 3 × 10 5 V/cm for LiNbO 3 :Fe [13,24,25]. This bulk field extends outside the crystal (evanescent fields) allowing particle manipulation by the corresponding electrical forces [14,16]. The evanescent PV fields can be calculated from the bulk fields through the boundary conditions at the sample surface and have been numerically simulated for periodic and arbitrary light illumination profiles [26].…”

“…Dielectric and metal particles have been successfully trapped using the PV method and arranged according to a variety of light-induced pattern and structures. Recently, an extensive review has been published which summarizes the main achievements in the field until 2015 [16]. A rapid progression has occurred during the last few years leading to new data and applications that still keep LiNbO 3 :Fe at the core of those new developments.…”

“…For PVT the acting fields are not the wave fields but the static electrical fields generated in the crystal by the exciting light without the need for using any electrodes. Hence, a main advantage of the photovoltaic tweezers over other optoelectronic techniques [16] is that the active electric fields are generated without electrodes enabling the fabrication of more flexible and less voluminous devices. In the PV method, the field distribution is controlled by the light profile similarly to the case of optical tweezers.…”

Pyroelectric Trapping and Arrangement of Nanoparticles in Lithium Niobate Opposite Domain Structures

“…In this case the use of light [4][5][6] or thermally-induced 7 electric fields generated in certain ferroelectrics have been recently proposed and successfully applied. However, these techniques are still young and new developments and applications are continuously arising 8,9 .…”