Photovoltaic contribution to counter-propagating two-beam coupling in photorefractive lithium niobate

Self-pumped contra-directional two-beam coupling in a photorefractive material using beam propagation simulation

“…The reduction in TBC efficiency for smaller values of C pv in LiNb0 3 is contrary to the experimental observation reported in Ref. 7. According to Ref.…”

“…1, this condition affects both the amplitude and phase of the space-charge field. For photovoltaic fields less than the saturation field, the detrimental effect of a reduced grating phase shift is generally compensated by an enhancement of the space-charge field amplitude 5,7 . At very high photovoltaic fields (≥ saturation field) the grating phase shift progressively approaches the ideal 90° phase shift.…”

Understanding the optical and electrical properties of a new photorefractive potassium niobate crystal

“…Enhancement of photovoltaic field is known to increase the space-charge field, which strongly assists the formation of the grating required for TBC [15]. Without a significant contribution from the photovoltaic field, the space-charge field is predominantly diffusion driven as is the case of KNbO 3 :Fe.…”

“…The saturation field depends linearly on the trap density. An increase in trap density due to the incorporation of Ag into the material should increase the space-charge field [15], but because of the current lack of uniform materials, the standard TBC method for measuring the trap density is not feasible. However, given the degree of TBC enhancement in relation to the relatively small photovoltaic field, it is most likely that the improved beam coupling occurs through an enhancement of the trap density.…”

Photovoltaic Field-Induced Self-Phase Modulation of Light in Liquid Crystal Cells

“…LiNbO 3 :Fe is capable of producing a bulk electric field on the order of 140 kV=cm [1]. Upon illumination, an asymmetrical potential associated with this material causes photoionized electrons to move in a preferential direction.…”