Title : Extremely high sensitivity refractive index sensor based on prism-coupled multilayer hyperbolic metamaterial
Abstract:
Optical sensors are widely used for refractive index measurement in chemical, medical research, and food processing industries. Several methods have been developed for this purpose, including metal-based propagating surface plasmon resonance and localized surface plasmon and emerging plasmonic biosensors based on metamaterials. We propose a multilayered metal–dielectric hyperbolic metamaterial (HMM)-based prism coupled refractive index sensor in the near-infrared range. The HMM multilayer comprises 10 alternating films of gold (20 nm) and Teflon AF (700 nm). Benefiting from Teflon AF has a lower refractive index compared to most dielectric materials dielectric such as MgF2 or SiO2 or Al2O3, the bulk Bloch plasmon polaritons (BPPs) in HMM composed of Teflon AF and gold is more easily excited. The BPPs are propagating waves inside the multilayered HMM whereas they decay exponentially outside the structure and are extremely sensitive to the refractive index of the analyte medium within the penetration depth of the evanescent field. By exciting a BPP mode using a prism-coupling technique, the sensitivity of our device can reach 460,000 nm per refractive index unit (RIU) and the figure of merit (FOM) can be up to 1394 / RIU, which indicate that the proposed optical HMM sensor is more advanced and promising than conventional plasmonic sensors due to ultrasensitive performance and high FOM. Since the developed sensor device has a lithography-free configuration, it can easily be fabricated using conventional thin film physical vapor deposition techniques. Therefore, our method shows a great potential for developing cost-effective high-performance in biological or chemical sensing.
Audience take away:
- Generally, the excitation of bulk Bloch plasmon polaritons (BPP) modes in the near-infrared region using the attenuated total reflection (ATR) method is challenging because of the unavailability of high refractive index prisms for matching the momentum between incident light and the high modal index value. In our design, the multilayered metal-dielectric hyperbolic metamaterial (HMM) consists of gold and Teflon AF, leading to a relatively low modal index values of the BPP modes in HMM. To the best of our knowledge, this is the first demonstration of successful excitation BPP mode in multilayered HMM using a low refractive index prisms such as K9 glass.
- The sensitivity of our device can reach 460,000 nm per refractive index unit (RIU) and the figure of merit (FOM) can be up to 1394 / RIU, which indicate that the proposed optical HMM sensor is more advanced and promising than conventional plasmonic sensors due to ultrasensitive performance and high FOM. Therefore, our method shows a great potential for developing high-performance in biological or chemical sensing.
- Since the developed sensor device has a lithography-free configuration, it can easily be fabricated using conventional thin film physical vapor deposition techniques. The fabrication costs of our sensor can be dramatically reduced compared to those designs that rely on intense nanopatterning techniques.
- The proposed configuration is expected to important applications in bio-chemical sensors, integrated optics and optical sub-wavelength resolution imaging.
