Fig. 1: Experimental geometry and sample images.

a Schematic illustration of beveled LN slab with thickness d. Pump light is incident at the bevel angle θ_bev with respect to the bevel normal and refracts into the crystal at “bounce” angle θ_bnc. Buildup distance for THz generation is denoted as L. b Diagram of experimental geometry. The LN slab is oriented with the optic axis (c-axis) parallel to the beveled edge. The c-polarized pump pulse is fixed on the bevel and the THz field is sampled at multiple distances from the bevel. After passing through the sample the probe pulse is sent through a quarter wave plate (QWP) and a polarizing beamsplitter (PBS), and then measured on balanced photodiodes (PDs). c SEM images of beveled edge of LN slab at two different scales. The slab is viewed from the top down (the y-direction as defined in (b)). The light gray region shows the beveled edge and the dark gray region below it shows the face of the LN slab