Improved Generation of Terahertz Light Through Heterogenous Multi-Layered Organic Crystal Structures

Yellow organic crystals, like BNA, MNA and NMBA can be used to produce light in the terahertz (THz) frequency range via optical rectification of ultrafast laser pulses. When working with these organic crystals, one needs to consider that (1) they have a low damage threshold due to their low melting points and (2) reflection losses due to multiple interfaces reduces the efficiency of the THz output. In this work, we developed new multi-layer "sandwich' structures with these yellow crystals by (1) fusing them to sapphire plates to allow the crystal to withstand higher laser fluences and (2) using the liquid crystal MBBA as an index-matching fluid to reduce Fresnel losses and improve the THz output. We show that the sapphire plates increase the damage threshold of these yellow organic crystals by a factor of two or more. Additionally, we show that the THz light output efficiency significantly increases by using a multi-layered sandwich structure. For some yellow organic crystals, the sandwich structure increases the THz intensity by more than a factor of two. Funding: NSF-DMR 2104317