The irresistible fantasy of man and machine being invisible has long been employed in fictional works, from the spaceships in star trek to harry potter’s magical clock. The advent of metamaterials is making the scientist think that they can actually make such materials. These are materials who properties cannot be seen in naturally occurring materials like negative refractive index, cloaking, wave modulations etc.. which are capable of unparalleled applications through proper engineering. In the other words, light consist of oscillating electric and magnetic fields perpendicular to each other, natural materials usually affect electric component whereas, metamaterials are capable of affecting the magnetic component also which could be responsible for anticipating wider applications possibility. Metamaterials are build from conventional microscopic materials like metals and dielectrics arranged in a periodic fashion. A precise shape, orientation, size, geometry, and arrangement fosters to create material properties which are unachievable in conventional materials. It has tremendous potential uses in various sensing schemes. Presently, applications of metamaterials could be seen in varied fields like physics, Engineering, optics, material science, and nanoscience.
Metamaterials have presently become an area of active research. In the work being presented the study is in the direction of sensing capability. To be precise, we have studied a metamaterial based thin film absorber which consists of a cross-shaped resonator and a ground plane. It displays sharp resonance peaks in the frequency spectrum which resulted in a high figure of merit (FoM) when employed in thin film sensing. The metamaterial structure is as shown. In our designed metamaterials, the unit cell periodicity was kept constant at px = py = 150 μm. The width of the cross-shaped resonator is taken to be w = 15 μm and the resonator length is taken to be L = 130 μm. The thickness of the ground and cross shaped resonator is t = 0.2 μm. In order to examine the sensing abilities of the designed metamaterial, the thickness of the spacer is varied from 2 μm to 18 μm, Followed by which, sensitivity, FWHM (full width half maximum) and hence FoM values are obtained. This structure was able to obtain an optimum Figure of Merit(FoM) of nearly 23 at a thickness of 5.5μm. The FoM is a quantity which determines the performance of a device, system or method in comparison to its alternatives. Higher the FoM value better the system it is. Design of the metamaterial and numerical studies are carried out using the commercially available numerical software, CST microwave studios. These kinds of perfect metamaterial absorber-based sensors can be effectively and efficiently used for sensing purposes in the fingerprint region of the electromagnetic spectrum with several organic, explosive, and bio-molecules that have a unique spectral signature at the terahertz frequencies. We are currently working on the experimental realization of the numerical outcomes. The author is Eppa Akhilesh Reddy under the guidance of Prof Dibakar Roy Chowdhury and was presented at OPTCT conference held at IIT-Roorkee march 2018.
Maidul Islam, S. Jagan Mohan Rao, Gagan Kumar, Bishnu P. Pal & Dibakar Roy Chowdhury,” Role of Resonance Modes onTerahertz Metamaterials basedThin Film Sensors”, Scientific Reports 7: 7355 DOI:10.1038/s41598-017-07720-9.
Longqing cong, Siyu Tan, Riad Yahiaoui, FengpingYan, Weili Zhang and Ranjan Singh; Experimental demonstration of ultrasensitive sensing with Terahertz metamaterials absorbers: A comparison with the metamaterials; Applied Physics Letters 106,031107(2015).