Designing chirped aperiodically poled structures for high-energy single-cycle terahertz generation

Abstract

We introduce a collinear scheme for the highly efficient generation of broadband single or few-cycle high-power terahertz (THz) pulses using optical rectification. For this purpose, two concepts are introduced and thoroughly analyzed. The first concept is the generation of chirped broadband terahertz pulses using chirped aperiodically poled electro-optic crystals. The second concept involves the compression of the terahertz pulses extracted from the aperiodically poled structure using a chirped mirror. An illustrative design employing cryogenically cooled aperiodically poled lithium niobate crystals and the appropriate chirped mirrors is presented. It is shown that the presented design allows the optical pulse to be re-used in subsequent generation stages, resulting in optical-to-THz conversion efficiencies in excess of 5% for terahertz radiation centered around ∼0.3 THz. Analytic solutions and numerical calculations are presented. In order to design a crystal with the optimum conversion efficiency, we take advantage of binary optimization techniques. This work paves the way for the generation of broadband terahertz radiation with several mJ of pulse energy using large-area aperiodically poled structures.