SAGAR KUMAR VERMA
@ph.iitr.ac.in
EDUCATION
Ph.D. in Photonics
RESEARCH, TEACHING, or OTHER INTERESTS
Atomic and Molecular Physics, and Optics, Biophysics, Sensory Systems, Surfaces and Interfaces
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Sagar Kumar Verma and Sachin Kumar Srivastava
Optica Publishing Group
Plasmonic metasurface absorbers are capable of absorbing the incident light at wavelengths corresponding to the excitation of Fano resonant modes. Absorption of the incident light is possible because of its confinement near the edges of the plasmonic nanostructure. Confinement of light takes place because of the coupling of superradiant and subradiant modes near the edges of the plasmonic metasurface. Superradiant and subradiant modes are excited for the oblique angle incidence of transverse magnetic (TM)-polarized light. The incidence of TM-polarized light supports the excitation of surface plasmon modes at the metal–dielectric interface. For the oblique angle incidence, surface plasmon modes couple with the incident light and generate the superradiant and subradiant modes near the plasmonic metasurface. We experimentally demonstrate the absorption of near-infrared light in the O and E optical communication band by a one-dimensional (1D) hybrid plasmonic metasurface. A low-cost, and flexible, 1D hybrid plasmonic metasurface absorber (HPMA) was obtained by extracting an Ag-coated, flexible, and 1D patterned polycarbonate layer from a digital versatile disc (DVD). The DVD consists of an Ag layer sandwiched between two 1D patterned polycarbonate layers. A large-area HPMA of 3cm2 in size was fabricated for optical characterization. Control experiments on the variation of the angle of incidence of light were performed to achieve the maximum light absorption of 79%. The effect of transverse electric (TE)- and TM-polarized light on the HPMA was studied. The effect of the thickness of the polymer layer on the HPMA, and per unit change of refractive index (RIU) of the analyte medium, were also investigated. HPMA supports refractive index sensing characteristics with a maximum sensitivity of 954 nm/RIU. Electric field profiles at different incidence angles were simulated using the finite element method on COMSOL Multiphysics software to explain the underlying physics of Fano resonance. HPMA can be used to develop cost-effective photonic devices such as sensors, spectral filters, photodetectors, heat-absorbing protective photonic covers, etc.
Mandeep Jangra, Sagar Kumar Verma, Sachin K. Srivastava, and Arnab Datta
Institute of Electrical and Electronics Engineers (IEEE)
An amplitude tunable frequency selective near infrared (854 nm) resonant-absorber on silicon (Si) has been demonstrated here. Tunability in absorbance was obtained by means of a box-resonator which comprises of 10 nm sputter deposited germanium-antimony-telluride (GST) film over a 418 nm wet-oxidized silicon dioxide (SiO2) layer grown on Si. Outer reflective surfaces of the resonator were deposited by thermal evaporation of aluminum, over which bias pads and cavity for light entrance and collection were patterned. Fabricated resonant-absorber demonstrated 159 ± 11 % change in absorbance due to thermally induced phase change in GST, which determines strength of cavity mode in thicker SiO2 layer
Sagar Kumar Verma and Sachin Kumar Srivastava
Institute of Electrical and Electronics Engineers (IEEE)
In this letter, we experimentally demonstrate the absorption of near -infrared light by a one-dimensional (1D) Fano resonant all-metal plasmonic metasurface (APM). The low cost, flexible and reusable APM was obtained by transferring the 1D patterned plasmonic nanostructure made of Al from a compact disk on a transparent scotch tape. Control experiments on the variation of angle of incidence of light were performed to achieve the maximum light absorption, followed by polarization, reusability, and refractive index (RI) dependent sensing performance of the APM absorber (APMA). Electric field profiles at different incidence angles were simulated using finite element method (FEM) to explain the interaction of light with the APMA. Absorption of light is possible because of its confinement at the sharp edges of plasmonic nanostructure due to the SP modes generated at the metal air interface. APMA supports RI sensing characteristics with a maximum sensitivity of 1216.85 nm/RIU. APMA can be used to develop cost effective photonic devices such as sensors, spectral filters, heat absorbing protective photonic covers, etc.
Sagar Kumar Verma and Sachin Kumar Srivastava
IOP Publishing
Abstract Simulation of an extra-ordinary optical transmission based self-referenced, flexible plasmonic metagrating has been reported. The metagrating was optimized to work as a refractive index (RI) sensor with high figure of merit (FOM) for near infra-red (NIR) communication band. The metagrating consists of two metal nanoslit arrays (MNSAs) in a manner that the open portion (groove) of the upper MNSA overlaps with the closed portion (pit) of the lower MNSA and vice versa. The metagrating structure was optimized to support dual plasmonic modes; one of them being sensing mode and the other, self-referenced. Transmission efficiency of 57%, the sensitivity of 1147 nm RIU−1, and FOM of 271/RIU were achieved for the analyte RI range 1.30–1.38. This design of metagrating possesses a stronger coupling of electromagnetic (EM) fields between the constituent MNSAs, which results in higher (almost double) transmission efficiency and FOM as compared to trivial MNSAs. Control simulations were performed to understand the role of various parameters on self-referencing operation, to evaluate the fabrication tolerances, and to estimate the performance at various ambient temperatures. The present study will be useful in development of flexible, low-cost, yet performance-enhanced metagrating sensors, which could easily be integrated on the tip of optical fibers working in the NIR communication window.
Sagar Kumar Verma and Sachin Kumar Srivastava
AIP Publishing
Extra-ordinary optical transmission (EOT) through subwavelength plasmonic nanoapertures is possible due to the funneling of light via surface plasmons (SPs) at the resonant wavelengths through the apertures. In this Letter, we experimentally demonstrate EOT through a plasmonic metagrating which does not have any open apertures. The plasmonic metagrating was fabricated by deposition of silver (Ag) on a one-dimensionally patterned flexible and transparent polydimethylsiloxane grating obtained via pattern imprinting and subsequent peeling off a commercially available blue ray disk. For normal incidence of transverse magnetic-polarized light on the top surface of plasmonic metagrating, transmission of light through it was obtained in the visible wavelength range of electromagnetic spectrum. Control experiments on variation of Ag film thickness were performed to attain optimal parameters for maximum transmission, followed by polarization and refractive index (RI) dependent performance of the plasmonic metagrating. Electric fields and Poynting vector profiles were simulated using a finite element method to explain the interaction of light with the plasmonic metagrating and the mechanism of plasmon mediated optical transmission. Such a large optical transmission is possible because the SP modes generated at metal–air interface penetrate through metagrating and couple with those supported by the metal–substrate interface. As a model application, RI sensing using the plasmonic metagrating was demonstrated. The present study shows that optical transmission is possible from apertureless structures and enriches literature with better understanding of EOT. Moreover, it opens avenues for development of flexible, cost-effective plasmonic metagratings for sensors, spectral filters, polarizers, etc.
Sagar Kumar Verma and Sachin K. Srivastava
Springer Science and Business Media LLC
Sagar Kumar Verma and Monojit Bag
Springer Singapore