Near-field Terahertz Sensing of Hela cells and Pseudomonas Based on Monolithic Integrated Metamaterials with Spintronic Terahertz Emitter.

Label-free biosensor operating within the terahertz (THz) spectra have helped to unlock a myriad of potential terahertz applications, ranging from bio-material detection to point-of-care (PoC) diagnostics. However, the THz wave diffraction limit and the lack of emitter-integrated THz biosensor are hindering the proliferation of high resolution near-field label-free THz biosensing. Here, a monolithic THz emission biosensor is achieved for the first time by integrating asymmetric double-split ring resonator metamaterials with a ferromagnetic heterojunction spintronic THz emitter. This device exhibits an electromagnetically induced transparency window with resonance frequency of 1.02 THz and a spintronic THz radiation source with a bandwidth of 900 GHz, which are integrated on a fused silica substrate monolithically for the first time. It was observed that the resonance frequency experienced a redshift behavior along with increasing the concentration of Hela cells and Pseudomonas due to the strong interaction between the spintronic THz radiation and the biological samples on the metamaterials. The spatial frequency redshift resolution is ~ 0.01 THz with a pseudomonas concentration increase from ~ 0.5×104/mL to ~ 1×104/mL. The monolithic THz biosensor is also sensitive to the sample concentration distribution with 15.68 sensitivity under spatial resolution of 500 μm, which is determined by the infrared pump light diffraction limit. This THz emission biosensor shows great potential for high resolution near-field biosensing applications of trace biological samples.