BITS Faculty Publications

Permanent URI for this communityhttp://localhost:4000/handle/123456789/1867

Browse

Now showing 1 - 20 of 44

Aluminum as a competitive plasmonic material for the entire electromagnetic spectrum: A review
(Elsevier, 2024-11) Arora, Pankaj
With plasmonics taking the lead in most sensing applications, research has geared towards alternative, cost-effective materials that can strive for large-scale production along with CMOS compatibility. Aluminum (Al) is among those competitive plasmonic metal films that have seen unprecedented research in recent years. The ability to exhibit appreciable plasmonic response in the entire electromagnetic spectrum has been reported along with improved performance sensing parameters. This review article covers different aspects of Al-based nanostructures, nano-films, and nano-particles in different wavelength regimes, displaying efficient plasmonic sensing for myriad purposes. A comprehensive review is conducted to explore the diverse and exciting possibilities emerging from Al-based tunable plasmons at the metal-dielectric interface. Al has already entered many applications, from on-chip plasmonic integration to point-of-care diagnosis. Thus, the application of Al in wide applications (heath, fluorescence, image-filtering techniques, and many more) is discussed here, along with the corresponding limitations and future scope associated with them.
Aluminum-Based Engineered Plasmonic Nanostructures for the Enhanced Refractive Index and Thickness Sensing in Ultraviolet-Visible-Near Infrared Spectral Range
(Electromagnetics Academy, 2019-03) Arora, Pankaj
We engineer Aluminum (Al) based periodic plasmonic nanostructures for enhanced refractive index and thickness sensing, which offer to access complete ultraviolet-visible-near infrared spectral range for surface plasmon resonance sensors. Al-based periodic nanostructures on top of a thin homogeneous Al metal coated on a BK-7 glass substrate were designed by systematic variation of geometrical parameters using Rigorous Coupled Wave Analysis and finite elements full wave solver. The shift in surface plasmon mode excited on the nanostructure-analyte interface was used to measure the variation in refractive index, and the number of waveguide modes with the increase in the thickness of the analyte was used to capture the variation in thickness of the analyte. The proposed nanostructures of period 400 nm and an aspect ratio of 0.1 offered a sensitivity of 400 nm/RIU and full width at half maximum of 18 nm resulting in a figure of merit of 22. These Al-based plasmonic nanostructures have potential to be used as refractive index and thickness sensor due to a high figure of merit, high localization of the field, and very low aspect ratio that is needed to maintain laminar flow of analyte.
Analysis of engineered aluminum-based plasmonic devices decorated with graphene/2D nanomaterials for enhanced biosensing applications in the near-infrared region
(IEEE, 2021) Arora, Pankaj
The dynamics of light-matter interaction between metal-analyte interfaces can be studied by the surface plasmon resonance phenomenon. Among the plasmonic metals, Aluminum (Al) has become quite a popular choice because of its ability to access a wider spectral range as well as better compatibility with optoelectronic devices. However, the study of Al as a plasmonic material has been almost completely confined to its periodic nanostructures/nanoclusters [1] , and there are limited reports of Al being used as a plasmonic metal in the standard Kretschmann configuration in the near-infrared region. Therefore, the proposed work reports the modified Kretschmann configuration with Al as a plasmonic metal for Surface Plasmon (SP) excitation to capture the minute changes in the refractive index of the analyte. The present work has also employed the advantages of Graphene (Gr) in context to increased interactions with biomolecules since Gr has emerged as an attractive alternative to be used as a biomolecular recognition element to functionalize the metal layer. Along with it, silicon is used as a high-index dielectric which enhances the sensitivity to produce accurate detection results. An optimized number of stacks of Silicon-Gr sheets are utilized for bio-sensing applications after negotiating the trade-off between important parameters like sensitivity and Figure of Merit (FOM) as shown in Fig. 1(a) . To demonstrate a bio-sensing application in the communication band, varying concentrations of the Leptospira bacterium in the form of different refractive indices are analyzed among the infected rodents and the sensitivity (S) and FOM were found to be 200°/RIU and 95.23 RIU -1 respectively at the wavelength of 1550 nm which are much better than the previously reported results in the literature.
CLEO Dispersion engineering with plasmonic nanostructures for enhanced surface plasmon resonance sensing
(CLEO, 2018) Arora, Pankaj
We experimentally demonstrate plasmonic resonance narrowing via dispersion engineering using plasmonic nanogratings placed on top of thin metal coated prism. The enhancement in Q factor, combined with strong field localization is attractive for sensing applications.
CLEO Observation of plasmonic enhanced EIT and velocity selective optical pumping measurements with atomic vapor
(CLEO, 2018) Arora, Pankaj
We demonstrate theoretically and experimentally for the first time nanoscale plasmonic enhanced electromagnetically induced transparency and velocity selective optical pumping effects in miniaturized integrated quantum plasmonic device for D2 transitions in rubidium with V-type system.
Colorimetric sensing using Fourier plane imaging of surface plasmons
(OSA Open Access, 2015-06) Arora, Pankaj
Surface Plasmons (SPs) propagating at a metal-dielectric interface are highly sensitive to minute changes in the near-field refractive index and thickness of surrounding medium. Moreover, coupling of incident light to the SPs at normal incidences and inherent filtering nature of plasmonic nanostructures resulting in color selective reflection and transmission can be used for applications in SP imaging sensing [1]. Recently, fluorescence coupled leakage radiation microscopy has gained importance wherein, the information pertaining to SPs is radiated out through the substrate and imaged [2]. However, this approach requires fluorescent tagging of analytes to be used in a sensing experiment, that may not be desirable in certain cases. A different approach to image sub-wavelength thick analytes without fluorescent tagging is by using colorimetry, wherein different refractive index films/regions appear as distinctly different colors in an ordinary microscope. In this work, we demonstrated a dark field SP imaging technique by fabrication of engineered 1D and 2D plasmonic substrates and microscopy configuration for real and Fourier plane (FP) imaging to capture surface changes at sub-wavelength thickness. The substrates were designed by sandwiching a thin layer of homogeneous metal between the patterned metal and glass substrate to convert the signature of SPs from transmission dips to transmission peaks [3]. The engineered fabricated substrates were placed in between two crossed polarizers (θP = 45° and θA = 135°) to diminish direct 0th order transmission and capture bright SPs emission against a dark background in real and FP images using a bright field optical microscope. In this specific configuration (θP = 45° and θA = 135°) of cross axis polarizer-analyzer, when the polarizer was at 45° with respect to grating vector, both Transverse Electric (TE) and Transverse Magnetic (TM) could excite SPs equally. The strong coupling between these modes induced a relative phase shift between TE and TM components which led to a polarization rotation of transmitted light by 90° [3].
Cooperative coupling of hot alkali vapors to surface plasmon: Towards room temperature quantum plasmonics with atomic media
(IEEE, 2018) Arora, Pankaj
We demonstrate cooperative coupling between hot vapors and surface plasmons with three-fold Purcell factor enhancement. Our result can be regarded as a major step in the quest for room temperature quantum plasmonics with atomic media.
Dark field imaging in a bright field microscope using tailored polarization of Spoof Surface Plasmons
(OSA Open Access, 2014) Arora, Pankaj
We experimentally image the hybrid mode Spoof Surface Plasmons in real and Fourier plane and utilize the differential phase retardation to convert a bright field microscope to dark field transmission plasmonic polarization microscope in visible wavelengths at normal incidence using 2D periodic metal pillars.
Demonstration of Dichroic Atomic Vapor Laser Lock in Micro Fabricated Vapor Cell Using Light Induced Atomic Desorption
(IEEE, 2019) Arora, Pankaj
We demonstrate Dichroic Atomic Vapor Laser Lock (DAVLL) using light induced atomic desorption in micro fabricated vapor cell. We have stabilized a 780 nm laser with a precision better than 400 kHz without heating.
Demonstration of On-Chip Thermocouple Photodetector in Infrared Regime through Field Enhancement by Plasmonic Nano Focusing
(OSA Open Access, 2018) Arora, Pankaj
On-chip thermocouple photodetector is realized for near infrared regime. Conversion of electromagnetic field to heat was performed through plasmonic mode which leads to joule heating at the metal. The responsivity of the device is 32±1mV/W.
Design and Analysis of Aluminum-Silicon-Graphene Based Plasmonic Device for Biosensing Applications in the Optical Communication Band
(Springer, 2021-01) Arora, Pankaj
This work utilizes the modified Attenuated Total Reflection (ATR) configuration, to detect minute refractive index changes near the sensing surface. In the proposed ATR configuration, the presence of the graphene layer increases the interaction with bio-analyte by adsorbing the biomolecules and the presence of a thin silicon layer helps to enhance the sensitivity of the proposed device. The use of aluminum as the plasmonic metal serves an economical value as well as compatibility with the optoelectronic devices. All the geometrical parameters of the layers over the base index prism are engineered for maximum sensitivity and narrow linewidth in the optical communication band using the transfer matrix method. The stacking of silicon-graphene layers over the thin metal-coated glass prism leads to the maximum sensitivity of 200°/RIU and figure of merit of 95.23 RIU−1 at the wavelength of 1550 nm. To demonstrate the proposed device as a bio-sensor, rodent urine is considered as the analyte under test to detect the changes in the varying concentration of Leptospira bacterium. The proposed plasmonic device opens a new window for the detection of biomolecular interactions in the optical communication band.
Design and comparative analysis of aluminum-BiFeO3-based plasmonic device in the near-infrared region
(Springer, 2024-05) Arora, Pankaj
In this work, a nano-plasmonic device based on Aluminum with BiFeO3 (BFO), as a multiferroic oxide with remarkable dielectric properties, is engineered using the transfer matrix method for implementation in an optical communication band for sensing applications. A comparative study is performed between different dielectric materials (e.g., BFO, Silicon, and Indium Phosphide), and the highest Figure of Merit (FOM) is achieved for the surface plasmon resonance sensor with BFO as the intermediate layer. To further increase the binding efficiency of the biomolecules with the sensing surface, a monolayer of 2D nanomaterial, namely Molybdenum disulfide, Graphene, MXene, and Fluorinated Graphene (FG), is added to the surface of the plasmonic device. After a rigorous analysis, FG is found to have the highest FOM of 334°/RIU and sensitivity of 125°/RIU. In summary, our work reveals potential applications for the proposed nano-plasmonic device based on Al-BFO configuration as a new type of supporting material with a monolayer of FG for enhancing biosensing activity.
Design and comparative analysis of aluminum-MoS2 based plasmonic devices with enhanced sensitivity and Figure of Merit for biosensing applications in the near-infrared region
(Elsevier, 2021-02) Arora, Pankaj
Aluminum (Al)-Molybdenum Disulfide (MoS2) based plasmonic structures act as excellent biosensors when exploited in the near-infrared region. While Al is economical as well as compatible with the optoelectronic devices, MoS2 is an emerging 2D nanomaterial with the promise of initiating better plasmonic activity. Based on Kretschmann's arrangement, we have explored angular interrogation over four different combinations of heterostructures with Al as the plasmonic metal layer, at a wavelength of 1550 nm. After studying the effect of Al thickness on the conventional configuration, the intermediate layers between the metal layer and the analyte were optimized. Inclusion of graphene along with MoS2 results in better interaction with the sensing medium. The effect of including silicon is also studied for sensitivity enhancement. In addition, a comparative analysis of sensor performances of the proposed devices is presented taking into account the two important parameters i.e. sensitivity as well as the Figure of Merit (FOM). Among the optimized multi-layered MoS2 based configurations, a maximum sensitivity of about 141°/RIU is obtained along with FOM of about 335.13 RIU−1. Finally, the single-stranded DNA sensing on the proposed devices shows that the structures can be used as a highly sensitive refractive index biosensor for bio-medical applications.
Dispersion engineering with plasmonic nanostructures for enhanced surface plasmon resonance sensing
(IEEE, 2018) Arora, Pankaj
We experimentally demonstrate plasmonic resonance narrowing via dispersion engineering using plasmonic nanogratings placed on top of thin metal coated prism. The enhancement in Q factor, combined with strong field localization is attractive for sensing applications.
Efficient Hyperfine Optical Pumping of RB Atoms in Miniaturized Vapor Cells
(IEEE, 2019) Arora, Pankaj
We demonstrate the positive role of buffer gas in achieving highly efficient hyperfine-structure based optical pumping of Rubidium atoms in miniaturized vapor cells. At a pressure of 40 Torr, pumping efficiency of 85% is achieved.
Efficient optical pumping of alkaline atoms for evanescent fields at dielectric-vapor interfaces
(OSA Open Access, 2019) Arora, Pankaj
We experimentally demonstrate hyperfine optical pumping of rubidium atoms probed by an evanescent electromagnetic field at a dielectric-vapor interface. This light-atom interaction at the nanoscale is investigated using a right angle prism integrated with a vapor cell and excited by evanescent wave under total internal reflection. An efficient hyperfine optical pumping, leading to almost complete suppression of absorption on the probed evanescent signal, is observed when a pump laser beam is sent at normal incidence to the interface. In contrast, when the pump and probe beams are co-propagating in the integrated prism-vapor cell, no clear evidence of optical pumping is observed. The experimental results are supported by a detailed model based on the optical Bloch equation of a four atomic-level structure, which also includes a treatment of transit relaxation and wall collision with relaxation rates that were obtained directly from the thermal velocities of the atoms and the penetration depth of the evanescent wave. The obtained highly efficient optical pumping at the nanoscale is regarded as an important step in the quest for applications such as optical switching, magnetometry, and quantum memory.
Engineering dielectric and metallic metasurfaces for sensing applications in the near-infrared region
(SPIE, 2024) Grover, Nitika; Arora, Pankaj
Dielectric and metallic metasurfaces are proposed to demonstrate the sensing applications in the near-infrared region under normal incidence light. The geometrical parameters of the proposed metasurfaces are designed using Rigorous coupled analysis under wavelength interrogation, and the results are verified using Comsol Multiphysics software. A layer of 2D nanomaterial (MoS2) is considered to increase the adsorption on the sensing surface. Aluminum-based metallic metasurfaces offer a sensitivity of 1100nm/RIU with a figure of merit of 250 RIU-1. The proposed metasurfaces are further used for the detection of cancer cells in human blood, and a red shift in the wavelength spectra is observed due to the increase in the refractive index.
Fourier plane colorimetric sensing using broadband imaging of surface plasmons and application to biosensing
(AIP, 2015-12) Arora, Pankaj
We demonstrate an optical technique for refractive index and thickness sensing of sub-wavelength-thick dielectric analytes. The technique utilizes the broadband, multimode, directional leakage radiation arising from the excitation of hybrid mode surface plasmons (SP) on low aspect ratio periodic plasmonic substrates with period ≈λ. The approach requires relaxed fabrication tolerances compared to extra ordinary transmission-based sensing techniques, wherein minor shifts in the fabricated dimensions result in a very large change from the designed resonant wavelength. We show that refractive index perturbations due to about 10-nm-thick dielectric can be captured optically by the usage of carefully designed plasmonic substrates, a halogen lamp source, free-space optical components, polarizers, and a low-end, consumer-grade charge coupled device camera. The plasmonic substrates were designed for converting the signature of hybrid mode SP excitation into a transmission peak by utilizing a thin homogeneous metal layer sandwiched between the periodic plasmonic structures and the substrate. The resonance is highly sensitive to the refractive index and thickness of the analyte superstrate. The excitation of hybrid mode SP results in a polarization rotation of 90° of the leaked radiation at resonant wavelength. In order to eliminate the problem of image registration (i.e., placing the same feature in the same pixel of the image, for comparison before and after a change in refractive index) for sensing, we perform the color analysis in the Fourier plane. The change in color of the bright emitted spot with highest momentum, corresponding to the leakage of fundamental SP mode, was used to measure the changes in refractive index, whereas the number and color of spots of lower momenta, corresponding to higher-order Fabry Perot modes, was used to measure the variation in thickness. We further show that the Fourier plane analysis can also be used to sense the index of thicker dielectrics, where real plane image analysis may fail to sense index perturbations, simply due to superposition of different modes in the real plane images of such substrates. Control experiments and analysis revealed a refractive index resolution of 10–5 RIU. The results were correlated with simulations to establish the physical origin of the change in the fundamental mode and higher-order modes due to the refractive index and thickness of analyte. As a demonstration of an application and to test the limits of sensing, the substrates were used to image the surface functionalization using 2-nm-thick 11-mercaptoundecanoic acid and immobilization of 7-nm-thick mouse anti-human IgG antibody. In biological systems, where a priori knowledge about a process step is available, where accurate chemical composition testing is not necessary or possible, the presented method could be used to study the surface changes using a label-free sensing mechanism.
Graphene decorated aluminum-nanostructure based plasmonic device with enhanced sensitivity and figure of merit using both wavelength and angle interrogation
(Elsevier, 2022-07) Arora, Pankaj
In this work, we have proposed graphene decorated Aluminum (Al) nanostructure-based plasmonic device for sensing in the near-infrared region where the same engineered plasmonic device can be used under both angle as well as wavelength interrogation with high sensitivity and Figure of Merit (FOM) simultaneously. A detailed analysis using rigorous coupled-wave analysis is carried out to prove the feasibility of the proposed plasmonic device with the same designed parameters to operate in two interrogation modes, which is impossible in conventional prism configuration. The performance parameters, sensitivity, and FOM are found to be 1000 nm/RIU and 333.33RIU−1 during wavelength interrogation and 119º/RIU and 318.91RIU−1 for the angle interrogation respectively. Finally, the biosensing application is carried out by demonstrating the glucose concentration detection in the urine samples. The proposed Al-based plasmonic device decorated with graphene layer has the advantages of being cost-effective and possessing real-time sensing capability, paving the way for biomedical applications in the near-infrared region.
Highly efficient optical pumping of Rb atoms for evanescent fields at dielectric-vapor interfaces
(IEEE, 2019) Arora, Pankaj
Optical prism integrated with a vapor cell and excited by evanescent wave under total internal reflection is used to study nanoscale light-atom interactions and to demonstrate efficient optical pumping of rubidium at a dielectric-vapor interface