Metamaterials are the sub-wavelength arrays of the composite structure made of metallic and/or dielectric materials. The metal-dielectric structure provides a significant enhancement in the field but has a high loss, low Q-Factor and poor spectral contrast in the visible and infrared frequencies. To overcome these problems, all-dielectric metamaterials structures are the better alternative which offers negligible losses due to their low absorption and hence they have narrow resonance peak and high spectral contrast. When all-dielectric metamaterial with specific geometry (asymmetric oscillators) interacts with the electromagnetic field in visible and infrared (IR) wavelength range, the interaction produces the Fano-Resonance. The Fano resonance depends on the shape and size of the metasurface structure and the refractive index of the surrounding. The Fano-resonance based on all-dielectric metamaterials can be used as a refractive index sensor for biomedical sensing and optical modulation in telecommunication. All-dielectric metamaterials based on Fano resonance can be utilized to have a high Figure-of-merit (FoM) refractive index sensor device. In this work, we are proposing a Fano resonance-based refractive index (RI) sensor which has a high FoM of the order of 2465.
In this paper, we proposed and theoretically simulated the tunable all-dielectric metasurface by varying the bisecting angular gap. The Fano-resonance position for the proposed silicon-on-silica structure shows the blue-shift with an increase in the angular gap. We have also observed the steep rise in the linewidth (FWHM) due to the increase in the angular gap. Such designs of the metasurfaces can provide a customized solution for various applications like modulator, filter, biochemical sensors.
In this paper, we have proposed and numerically investigated an all-dielectric metasurface consisting of a 2-dimensional periodic array of convex facing silicon asymmetric split arcs on the silica substrate. Due to split asymmetric arcs configuration, the structure exhibits Fano resonance at the wavelength of 967 nm. The maximum achieved quality factor (Q-Factor) and the spectral contrast ratio of the Fano resonance are 213.4 and 99.91%, respectively. The proposed metasurface can be used as a refractive index sensor as the resonance wavelength is linearly dependent on the refractive index of the surrounding. With the increase in the refractive index, the resonance wavelength shows the red-shift. We found that the wavelength shift per refractive index unit (RIU) is 250 nm/RIU and the figure of merit of this sensor is 50.
A simple but novel technique for eliminating depolarization loss resulting from thermally induced stress
birefringence of a flash lamp-pumped free running Nd:YAG laser is reported here. The output characteristics of
the beam with minimum depolarization loss have been systematically investigated by testing various resonator
configuration, pump repetition rate and pump power for a Nd:YAG rod of 4mm diameter and 65mm length. It is
shown that, by a tilted Glan-Taylor polarizer inside a stable cavity optimally reduces depolarization loss upto