Photogalvanic/pyroelectric power conversion and self-pulsing of electro-wetting of LC droplet on lithium niobate (LN)-crystal

Photogalvanic current and voltage photoinduced by CW laser illumination of Fe-doped LN reveals quasi-periodic pulsing due to microplasmas discharges. This transformation of constant external influence into periodic response is interesting as example of self-excited systems, resembling pulsations of biological systems. Microplasmas discharges are also interesting for applications in various fields, such as surface treatment, sterilization, water splitting. We analyze self-pulsing of photogalvanic current visualized by dynamic electrowetting in a simple LC-cell, formed by a nematic LC droplet placed on Fe-doped LN crystal. In modeling contributions from both photogalvanic (bulk photovoltaic) and pyroelectric (charging by heating-cooling) effect are included. The analysis of dynamic regime reveals that a current pulse (in microsecond range) has asymmetric shape with extremely sharp rise with longer decay time. Reflected interference patterned was modulated by the dynamic electro-wetting effect. For high light intensity power conversion efficiency is enhanced due to nonlinear photogalvanic effect and microplasmas discharges.