Highly Efficient Narrowband Terahertz Generation in PPLN Driven by a Two-Line Laser Source

We demonstrate record efficiencies of nonlinear optical-to-terahertz conversion near 1% for narrowband terahertz generation. This is achieved by strongly-cascaded difference frequency generation in periodically-poled LiNbO
3
crystals using a novel multi-mJ laser source with two narrow spectral lines of tunable separation and pulse duration.