Investigations into High Energy THz and Ultra-broadband IR Radiation from Organic Salt Crystal Emitters

Abstract

The importance of THz radiation has been significantly increased over the recent decades due to the developing laser- and THz-science. There are plenty of planned and realized applications of THz radiation used in several fields including industry, security and defense, medicine and scientific research such as control over matter or electron acceleration. THz source development is the base of these studies and aims to gain the ability to create simple, easily available sources with high level of control over their parameters. Source development is still an ongoing, intensely developing part of THz science. Organic salt crystals (OSC)s is group of crystals consist of organic compounds and some of them own extremely high nonlinear properties (e.g. DAST 490±90 pm/V at 1535 nm). They can be used for both THz generation via optical rectification and THz detection via electro-optic effect. The most well-known OSC types are the DAST, DSTMS, OH1, HMQ-TMS and BNA crystals. Although some of their properties are similar, they possess different characteristics. Their typical size is a couple of mm with few hundred μm thickness. They are strongly birefringent crystals, thus collinear phase matching for THz generation is possible over different IR wavelengths. They have several strong THz absorption peaks due to their complex molecule structure. The generated THz spectrum usually covers the range starting from 0.1 THz up to 3 THz or 5 THz but 15 THz has been also demonstrated. The generated THz pulse energies are usually in the tens of μJ range as well an outstanding 0.9 mJ has been also reported. The typical conversion efficiencies are around 1-3% at certain pump wavelengths and pump intensities.