Abstract

One of the most efficient optical-to-terahertz converters is a thin (30-50 μm thick) layer of LiNbO₃ (LN) attached to a Si-prism outcoupler [1, 2]. A femtosecond laser pulse propagates in the LN layer as a guided mode and produces nonlinear polarization, which emits a Cherenkov cone of broadband terahertz radiation in the Si prism. The prism couples the radiation into free space. An inherent disadvantage of the converter is a dip in the generated terahertz spectrum (at ~1.4 THz for a 30-μm thick LN layer) that originates from the destructive interference of the terahertz waves emitted to the Si prism from the LN layer directly and after reflections from the layer boundaries. The presence of the dip can limit application possibilities of the converter, particularly for spectroscopic purposes.

© 2015 IEEE