The spectral linewidth and intensity of narrowband terahertz pulses generated by photomixing with beating of nonlinearly chirped laser pulse pairs are studied. The direct relationship between the dispersion of the pump pulse stretcher and the chirp of the terahertz pulse is shown. Simple analytical expressions for the linewidth and intensity of the terahertz spectrum are obtained and their validity is confirmed by numerical simulations. Generation of narrowband terahertz pulses with minimal chirp is demonstrated.
We theoretically show that it is possible to generate chirp-free terahertz (THz) pulses with a chirped-pulse beating method by using an optical fiber as a pulse stretcher. Proper choices of the core radius and the dopant fraction of the core material of a step-index single-mode optical fiber eliminate the third-order spectral phase of the fiber, thus giving the pump laser pulse a purely linear chirp. We also show that even a standard commercial single-mode optical fiber can give THz pulses of lower chirp than the lower limit for a grating pair. We perform experiments to verify our theory.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.