A system for biomolecule identification by terahertz sensing, an asymmetric triple split-rectangular (ATSR) metamaterial biosensor, and a method for biomolecule identification by terahertz sensing are presented. The asymmetric triple split-rectangular (ATSR) metamaterial biosensor includes three gap areas which highly confine an electric field. The biosensor includes an E-shaped structure facing an inverted E-shaped structure with gaps between the respective legs. Each leg has a specially designed extension on either side which increases the electric field. A terahertz laser interrogates an analyte upon the metamaterial structure with a plurality of frequencies. The amplitude difference is estimated by an amplitude difference referencing technique. The amplitude difference is matched to a database record to identify the biomolecule analyte. The asymmetric triple split-rectangular (ATSR) metamaterial biosensor in combination with the amplitude difference referencing technique detects the type of biomolecule with a high degree of accuracy and requires only small analyte samples with sub-micron thicknesses.