Terahertz biosensing based on bi-layer metamaterial absorbers toward ultra-high sensitivity and simple fabrication

Abstract

Metamaterial absorbers have proven their ability to sense in the terahertz domain. However, the sensitivity is always limited by the poor spatial overlap between the analyte and the localized enhanced electromagnetic field. Here, we try to tackle this challenge by utilizing an absorber with a bilayer cross-shaped plate-hole structure to ingeniously excite hot-spots covering the analyte. As a result, the sensitivity is significantly improved, theoretically about 7 and 18 times higher than that of the conventional cross-shaped absorber and its complementary cross-shaped absorber, respectively. We then experimentally demonstrate its ability to quantitatively detect biotin with a sensitivity of 153 GHz/μM, higher than that of previously reported biotin sensors. Additionally, the polarization-independent nanostructure decreases the design and fabrication complexity and maintains high reflection at a wide range of incident angles over ±50°. These findings open up opportunities for metamaterial absorbers to realize ultrasensitive biosensing in the fingerprint region of the terahertz regime.

Temperature Tunable Narrow-Band Terahertz Metasurface Absorber Based on InSb Micro-Cylinder Arrays for Enhanced Sensing Application

“…In order to further reveal the narrowband perfect absorption properties, the FWHM (full-width at half maximum) and Q-factor of the proposed MSA have been also calculated and analyzed. The FWHM bandwidth of the resonance absorption peak is only about 0.0157 THz, and the Q-factor of the proposed MSA is about 120.9, which is obviously superior to the previous designs [5], [20]- [22]. Hence, it can be reasonably believed that the proposed MSA exhibiting such sharp resonance absorption peak possesses great application potential in high sensitivity sensing field owing to the ultra-narrow FWHM and high Q-factor [19]- [25].…”

“…According to the fitting result, it is evident that the resonance frequency of the proposed MSA decrease almost linearly with the increasing RI of the surrounding analyte since the fitting solid line comes through all the resonance frequency points. Furthermore, it can be also clarified that the bulk RI sensitivity S RI is about 960 GHz/RIU which is obviously superior to previous designed sensors operated in THz region [5], [20]- [22]. Since the frequency FWHM of the proposed MSA structure surrounded by air is about 15.8 GHz, the corresponding FOM RI could be calculated to be about 60.76 according to the definition mentioned above.…”

“…The S RI has been defined as the resonance absorption frequency shift ( f ) caused by a minor RI change ( n) of the surrounding analyte. Thus, the RI sensitivity can be expressed as S RI = f / n, whose unit is always accepted as the shift frequency per refractive index unit (GHz / RIU) [20]- [22]. Besides, another key indicator FOM RI could be considered as the quotient acquired from the S RI divided by the FWHM of resonance absorption peak frequency, which can be expressed as FOM RI = S RI / FWHM [11].…”

Spatiotemporal Terahertz Metasurfaces for Ultrafast All‐Optical Switching with Electric‐Triggered Bistability

“…The terahertz (THz) spectral region with the photon frequency presenting between 0.1 and 10 THz is the last enigmatic electromagnetic radiation, [ 1–5 ] which favors their utilization in the fields of next‐generation data communication, [ 6–8 ] nondestructive sensing, [ 9,10 ] security screening, [ 11,12 ] and biomedical sciences. [ 13–16 ] Fueled by the rapidly increasing demands for enormous advanced system‐level applications, the ability of THz signal processing is of vital importance. Unfortunately, the scarcity of available naturally existing materials makes this research direction seriously hindered by the conventional photonic and electric devices.…”

All-Metal Terahertz Metamaterial Biosensor for Protein Detection

“…Metamaterials sensitive to the surrounding environment, especially those composed of subwavelength metal structures [24][25][26], have been widely used to detect various biomolecules. The combination of terahertz waves and metamaterials provides a new detection method for the biomedical molecules, which cannot only achieve label-free detection, but also refresh the resolution limit of existing sensors.…”