Beam Profile Deformation of Fs-laser Pulses During Electro-Optic Scanning with KTN Crystals

A few years ago, electro-optic high-speed scanning (> 10,000 rad/s) at high deflection angles (> +/- 100 mrad) has been demonstrated successfully using KTa 1-x Nbx O 3 (KTN) as crystal material. KTN scanners were commercially available shortly after. Presented experiments with KTN scanners show that beam profile deformation occurs, at which the degree of deformation is dependent mainly on the deflection angle mid- point position, the deflection angle amplitude and the laser pulse fluence, the latter being crucial for ultrashort laser pulses. Analysis of physical models of KTN scanners and comparison to experimental results point out that trapped space charges are the main reason for deflection and the observed dependencies.