Developing terahertz sensors capable of highly sensitive detection of nanoscale thin films and a few biomolecules is a formidable task critical for realizing their full potential in scientific research and advanced applications. This study introduces a novel approach to optimize metamaterial sensors for the detection of minute quantities of dielectric materials.

The degree of frequency shift is contingent upon intrinsic properties such as electric field distribution, Q-factor, and mode volume of the bare cavity. Additionally, it depends on the overlap volume between the high-electric-field zone(s) and the analyte. Following the principles of simplified dielectric perturbation theory, we have designed interdigitated electric split-ring resonators (ID-eSRR) to markedly enhance detection sensitivity when compared to eSRRs lacking interdigitated fingers. The interdigitated structure of ID-eSRR redistributes the electric field, generating highly localized enhancements that amplify analyte interaction.

Furthermore, the periodic alteration of the inherent anti-phase electric field minimizes radiation loss, resulting in a higher Q-factor. Experimental tests with ID-eSRR sensors, operating at approximately 300 GHz, exhibit an impressive 33.5 GHz frequency shift upon depositing a 150 nm SiO2 layer as an analyte simulant. This represents a figure of merit (FOM) improvement exceeding 50 times compared to structures lacking interdigitated fingers. This meticulously planned design strategy presents a promising pathway for achieving highly sensitive detection of thin films and trace amounts of biomolecules, opening up new possibilities for cutting-edge research and applications in various fields.