PhD Student, Australian National University
The development of highly-sensitive miniaturized sensors that allow real-time quantification of analytes is highly desirable in medical diagnostics, veterinary testing, food safety, and environmental monitoring.
Due to advance optical instrumentations and rapid detection capability, optical sensors have been widely using to analyze the chemical and molecular interactions. A number of optical sensing methods are available such as microring resonator based sensor, waveguide based sensor, optical fiber Bragg grating, Mach–Zender interferometers, Surface plasmon resonance (SPR), etc.
Compared to other optical sensing techniques, SPR sensor has been shown high-sensitive nature due to small change of sample refractive index. It also showed broad range of applications such as liquid detection, gas detection, biosensing, and medical diagnostics, including drug detection, biological analyte, and chemical detection. However, plasmonic sensor has some major disadvantages which prevent it to be commercialized widely.
Disadvantages of SPR sensors:
However, these problems can be solved using dielectric metasurface because it doesn’t have absorption loss. Also it shows narrow resonance peak due to change of analye refractive index as a result detection accuracy is high.
Besides, for the optical sensors, controlling light propagation is a key parameter to enhance the sensor performance. Metasurfaces have unique light trapping/controlling capabilities. Metasurfaces can be designed to control light characteristics including phase, amplitude, polarization and dispersion. Metasurfaces’ thickness are very thin; it can be considered almost negligible compared to the operating wavelength which results in the easy control of amplitude and phase of the incident light and enable sub-wavelength effect.
On the other hand, metasurface based sensor will reduce metal coating difficulties (existing problem of some sensing techniques such as SPR sensor) and fabrication complexity due to its planer surface structure. Moreover, metasurfaces exhibit the electric and magnetic properties, simultaneously and can be utilized to show double negative properties. As a result, it will find the potential applications in portable real-time chemical and biological sensing.
Abstract: Fano resonances are central features in the responses of many systems including atoms, molecules, and nanomaterials. They are consequences of interferences between two channels, most frequently associated to two system modes. In plasmonic materials, Fano interferences between optical modes have been shown, experimentally and theoretically, to induce narrow features in their scattering spectra. By investigating individual silver-gold heterodimers, we first experimentally demonstrate that Fano interference is also a key effect in the optical absorption of plasmonic nano-objects, in agreement with theoretical predictions. Conversely to previously investigated systems, the two interacting modes at the origin of absorptive Fano effect are mostly localized on either one or the other dimer component. Experimental results were obtained by selectively monitoring the optical absorption of one dimer component using a two-color nonlinear time-resolved technique. This also opens the way to full optical far-field non-contact investigations of charge or energy exchanges between nano-objects with a spatial resolution much smaller than the optical wavelength.
Pub.: 21 Sep '16, Pinned: 31 Aug '17