Imaging-free tilted-pulse-front-pumped lithium niobate source for high-energy terahertz pulse generation

A new, to the best of our knowledge, type of terahertz pulse source is introduced and demonstrated, employing a volume phase holographic grating in direct contact with a nonlinear material requiring a large pulse front tilt angle-e.g., lithium niobate or lithium tantalate-and another transmission grating, which pre-tilts the pump pulse front. The setup enables a significant reduction in the wedge angle (to <50% of conventional tilted-pulse-front-pumped setups) while eliminating the need for imaging optics. Consequently, significantly larger useful pump sizes and pump energies can be used, resulting in higher THz energy. In the absence of imaging, the pulse lengthening at the edges of the pump beam is strongly reduced, resulting in a substantial increase in the conversion efficiency (∼1.5×) in comparison to the conventional tilted-pulse-front setup.