Electro-optic prism-pair setup for efficient high bandwidth isochronous CEP phase shift or group delay generation

Abstract

We report the experimental demonstration of an electro-optic prism pair pure carrier-envelope phase (CEP) shifter at low voltage (shift of 1rad for a voltage of 90V, applied to a crystal of 5mm aperture). Validating our mathematical model, the experiments prove that this set-up which uses two rubidium titanyl phosphate (RTP) crystals, can be used either as an efficient high bandwidth CEP shifter without modifying the group delay of an ultrashort pulse (isochronous CEP shifter) or alternatively as a group delay generator with quasi-constant CEP (Pure Group Delay generator). These two configurations which correspond to specific geometries are characterized by spectral interferometry with a 800nm mode-locked Ti:sapphire laser. The results are in very good agreement with the model. In the pure group delay mode, a group delay of 2.3fs is obtained at 1000V/cm without significant CEP shift. In the isochronous mode, a shift of 5.5rad at 1000V/cm is generated without significant delay. The applied voltage is also lowered by a factor of nearly three in this configuration, compared to the case of an RTP rectangular slab of the same total length.