Germanium Plasmon Enhanced Resonators for Label-Free Terahertz Protein Sensing

A Terahertz protein sensing concept based on subwavelength Ge resonators is presented. Ge bowtie resonators, compatible with CMOS fabrication technology, have been designed and characterized with a resonance frequency of 0.5 THz and calculated local intensity enhancement of 10.000. Selective biofunctionalization of Ge resonators on Si wafer was achieved in one step using lipoic acid-HaloTag ligand (LA-HTL) for biofunctionalization and passivation. The results lay the foundation for future investigation of protein tertiary structure and the dynamics of protein hydration shell in response to protein conformation changes.