Design Optimization of Interdigitated Terahertz Metamaterial Sensors

Dr. Lei Cao1,2, Dr. Fanqi Meng2, Ms. Esra Özdemir2, Mr. Yannik Loth3, Ms. Merle Richter3, Dr. Anna Katharina Wigger3, Ms. Maira Pérez Sosa4, Dr. Alaa Jabbar Jumaah4, Prof. Shihab Al-Daffaie4, Prof. Peter Haring Bolívar3, Prof. Hartmut G Roskos2
1Huazhong University of Science and Technology, Wuhan, China. 2Johann Wolfgang Goethe-Universität, Frankfurt, Germany. 3University of Siegen, Siegen, Germany. 4Eindhoven University of Technology, Eindhoven, Netherlands


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.