Multispectral Narrowband Terahertz Source Based on RbAP Molecular Crystal and a Tunable Metamaterial Filter

This study explores a new type of terahertz-radiation source based on a molecular crystal of rubidium acid phthalate (RbAP) and a tunable metamaterial that functions as a filter. The high-quality oscillatory response of the RbAP crystal lattice in the terahertz frequency range enables the generation of narrowband terahertz radiation at multiple frequencies simultaneously, with high spectral brightness and peak power. Single femtosecond laser pulses excite the crystal. Switching between the generated spectral lines is achieved using a planar metamaterial, the absorption lines of which depend on the incident radiation polarization. The developed source allows for dynamic tuning of the emission spectral line, which makes it more versatile and efficient than conventional narrowband sources, such as quantum cascade lasers.