Fano-resonance characteristics of nematic liquid crystal based all-dielectric metasurfaces

All-dielectric metasurface (ADMS) is transparent and has negligible losses due to lack of metal composite as in plasmonic metasurface. The ADMS can produce narrow Fano-resonance peak when incident with light. The light response can be dynamically control by regulating applied electric field across the nematic liquid crystal (NLC) integrated with ADMS. In this work, the Fano-resonance characteristics due to NLC integration with ADMS are studied. The NLC is integrated with ADMS as NLC-over-ADMS (scenario 1) and as ADMS-over-NLC (scenario 2). The resonance wavelength position 1568 nm of scenario 2 is red-shifted compared to 1552 nm of scenario 1 due to higher effective refractive index of scenario 2. Also, the field confinement among metasurface elements for scenario 2 is stronger than scenario 1, thus the produced Fano resonance linewidth (7 nm) is less and Q-factor (224) is high for scenario 2 compared to linewidth (12 nm) and Q-factor (129) for scenario 1. The modulation depth of Fano resonance is 87% for scenario 2 due to weak field coupling between ADMS and NLC compared to the modulation depth of Fano resonance is 99% for scenario 1 due to strong coupling between ADMS and NLC. These metasurface based devices find application as the bio-medical sensor, modulator, non-mechanical switching, tuning, colour displays etc., based on the desired values of performance parameters linewidth, Q-factor and modulation depth of Fano resonance. These metasurface structures can be fabricated by the standard lithography process.