Browsing by Author "Rajesh K.B"

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ENGINEERING AXIALLY POLARIZED SUB-WAVELENGTH SCALE FOCAL STRUCTURES USING ANNULAR WALSH FILTER
(SpringerLink, 2023) Umamageswari N; Thiruarul D; Lavanya M; William Charles J; Jaroszewicz; Rajesh K.B
Based on vector diffraction theory, the tight focusing properties of radially polarized Bessel Gaussian beam (BGB), phase modulated by annular Walsh function filters and focused by a high NA parabolic mirror system are studied numerically. The annular Walsh filter derived from the annular Walsh functions forms a complete set of orthogonal phase filters that takes values of either 0 or π phase corresponding to + 1 or −1 over the domain specified by the inner and outer radii of the annulus. Numerical results show that by properly modulating the annular obstruction of Walsh filter and pupil to beam ratio of the input BGB, one can generate many novel focal patterns such as three-dimensional multiple sub-wavelength scale focal spot segments, optical needle, axial flat top profile, etc. We expect that such three-dimensional chain of focal structures is useful for nano-lithography, particle trapping and transportation, as well as confocal and STED microscopy, microstructure fabrication and so on.
GENERATION OF 1D ARRAY OF FOCAL SEGMENTS USING SPIRALLY POLARIZED BEAM AND COMPLEX PHASE FILTER
(Elsevier, 2022-05) Senthilkumar M; Udhayakumar M; Lavanya M; Mahadevan G; Rajesh K.B; Jaroszewicz Z
A new approach for generating and tuning 1D array of sub wavelength scale electric and magnetic spot, hole, flattop and bubble profiled segments using tightly focused spirally polarized beam phase and amplitude modulated with suitable complex phase filter is proposed and investigated numerically using vector diffraction theory. Numerical result shows that by using a well optimized single Complex Phase Filter (CPF), one can generated and tune the geometry of the 1D chain of electric and magnetic field distribution from sub wavelength scale hole to spot and then to a chain of flattop profiled or bubble structure segments by properly tuning the spirallity of incident spirally polarized beam. These focal field distributions may find potential applications in laser direct writing and optical microscopy, as well as multiple-particle trapping, alignment, and acceleration along the optical axis.
GENERATION OF AXIAL MULTI FOCI PATTERN
(Research Square, 2022-10-14) Thiruarul D; William Charles J; Lavanya M; Rajesh K.B; Jaroszewicz Z
Axially splitted multi foci(AMF) are numerically generated by tight focusing of higher order cylindrical vector beam(HCVB) through an annular Walsh filter .Here we report that by properly manipulating the parameters of HCVB such as initial phase(φ0 ),topological charge (m), polarization rotation angle or azimuthal index (a) and suitably phase modulated with a Walsh function filter of fixed orders (n) and annular obstruction (ε),onecan generate axially polarized multiple spots,transversely polarized multiple holes,transversely polarized multi spots,axially and transversely polarized multi holes with extended central annular region.These distributions may be useful for multiple optical trapping and axial superresolution microscopy.
GENERATION OF AXIALLY SPLITTED ULTRA-LONG MULTIPLE OPTICAL NEEDLES/OPTICAL TUBES USING GENERALIZED CYLINDRICAL VECTOR BESSEL GAUSSIAN BEAM PHASE MODULATED BY ANNULAR WALSH FUNCTION FILTER
(SpringerLink, 2022-08-29) Thiruarul D; William Charles J; Lavanya M; Rajesh K.B; Jaroszewicz Z
Based on vector diffraction theory and annular Walsh function filter, axially splitted ultra-long multiple optical needles/optical tubes of electric as well as magnetic field distributions are numerically generated by generalized cylindrical vector Bessel Gaussian beam phase modulated by annular Walsh function filter. This multiple optical structures can be conveniently tailored by properly tuning the initial phase of the Cylindrical vector beam (CVB) and Walsh order of the annular Walsh function filter. Furthermore, the effect of energy flux density (Poynting vector) as well as Spin angular momentum(SAM) distribution in the focal region are theoretically analyzed. We expect that such an axially splitted focal systems could be applicable in optical trapping and manipulation of multiple particles, optical super resolution microscopy etc.
GENERATION OF MULTIPLE FOCAL PATTERN VIA PHASE MODULATED RADIAL AND AZIMUTHAL VARIANT VECTOR BEAM
(Springer, 2023-03-07) Thiruarul D; William Charles J; Lavanya M; Rajesh K.B; Jaroszewicz Z
The multiple focal patterns such as longitudinally/transversely polarized multiple focal spots/holes, longitudinally/transversely polarized annular dark multiple spots with petal shapes are in high demand for applications such as multiple optical trapping and manipulating, light-sheet fluorescence microscopy and optical lithography. This article numerically demonstrated the possibility of achieving the above task by subjecting phase modulation of radial and azimuthal variant vector beam through suitable annular Walsh function filter. Here it is demonstrated that the inherited self similarity properties of annular Walsh function and the flexibility of tuning the radial and azimuthal index of input beam is a state of art in landscaping multiple focal segment of desirable spatial and polarization distribution.
HIGH PERFORMANCE SPR BASED FIBER OPTIC SENSORS USING MXENE
(Chikkanna Govt. Arts College, Tiruppur, 2020-03-05) Balamurugeshwari A; Nivethitha P.V; Subanya S; Rajesh K.B
In the last few decades, Surface Plasmon Resonance based optical sensors has created a niche for itself in the field of bio, chemical and gas sensing applications due to their surprising superior characteristics such as its high sensitivity, reliability, real time sensing ability, compactness and flexibility. Recently a new family of 2d transition metal carbide/ nitride materials known as MXene has drawn increased attention due to their exceptional properties like excellent thermal stability, easily tunable structure, large interlying surface, high electrical conductivity and large surface area. A detailed analysis on the performance parameters of SPR based fiber optic sensors having a Four layer model - Core/metal/Mxene/Sensing medium is performed. Kretschmann configuration and the N layer matrix model has been employed for the performance study and a novel SPR sensor based on Au/Ag/Co/Ni with MXene layers is theoretically presented. The thickness of the metal layer, Mxene and the RI of the multi layers have been properly chosen. Enhanced sensitivity is observed in the MXene based Sensor compared to the bare metal based SPR sensor as well as the conventional metal film sensors. The other sensor parameters such as the Quality Factor, Detection Accuracy, Signal to Noise ratio has also shown desired values. Owing to their unique properties, MXene has demonstrated promising nature for various applications such as energy storage, chemical, photo and electrocatalyst, photothermal therapy, gas sensing etc.
SENSITIVITY ENHANCEMENT OF SURFACE PLASMON RESONANCE SENSOR USING HYBRID CONFIGURATION OF 2D MATERIALS OVER BIMETALLIC LAYER OF CU–NI
(Elsevier, 2020-05-15) AlaguVibisha G; Jeeban Kumar Nayak; Maheswari P; Priyadharsini N; Nisha A; Jaroszewicz Z; Rajesh K.B; Rajan Jha
This Theoretical study aims at improving the sensitivity of surface plasmon resonance biosensor under angular interrogation. We observed that the sensor configuration composed of bimetallic layer of Cu–Ni attached with 2D materials MoS2/WS2/MoSe2/WSe2/graphene enhanced the sensitivity of the sensor to a great extends. The thickness of the bimetallic layers and the number of layers of 2D materials are optimized to achieve maximum sensitivity. Numerical results shows that sensitivity as high as 480∘/RIU is achieved for the well optimized bimetallic configuration consist of 35 nm of Cu and 20 nm of Ni thickness for the analyte refractive indices ranging from 1.33–1.335. Up on functionalizing the metal layers with bimolecular recognizing 2D materials, we noted that configuration with 35 nm of Cu, 15 nm of Ni with monolayer of 2D material WS2 enhanced the sensitivity as high as 426∘/RIU. We expect that such a simple structure and promising results will lead the proposed sensor as a suitable and potential candidate for detecting biomolecules organic elements and other analytes.
SPR BASED BIO SENSORS USING BLACK PHOSPHORUS - A BOON TO BIOMEDICAL APPLICATIONS
(Chikkanna Govt. Arts College, Tiruppur, 2020-03-05) Deepapriya G.S; Nivethitha P.V; Subanya S; Rajesh K.B
The recent attention of plasmonic research has turned its focus towards the field of biomedical applications, due to the excitingly appreciable optical, electronic, chemical, thermal and mechanical properties of the 2D materials. Though these materials exhibited good sensing performance, there existed certain shortcomings like the lack of bandgap in graphene, low carrier mobility of TMDCs which hindered their usage in bio-sensing applications leading to the search for a new 2D material with desirable properties for improved sensor parameters. Black phosphorus (BP), an emerging two-dimensional (2D) material has appreciably unique physical, chemical, electronic and optical properties like direct band gap, smaller work function, high charge carrier mobility, better binding of molecules on sensor surface, high surface to volume ratio, above all its biodegradability and negligible toxicity in the biological environment which keeps it par from the other available 2D materials. This has aroused more and more research interest on the biomedical applications of BP. A detailed numerical analysis on the performance parameter of an optical fibre based SPR sensors with BP layers over spr active metals Au/Ag/Co/Ni/Cu have been studied. The parameters such as the thickness of the metal and the BP layer, its dielectric constants and refractive index of the sensing layer is properly chosen and sensitivity evaluation is performed in terms of its FWHM, Sensitivity, Quality Factor and Detection Accuracy. A noticeably high improvement is witnessed in Sensitivity and the other parameters due to the presence of the BP layers. The reason for the enhancement in sensitivity is due to the better binding of biomolecules. The attenuated total internal reflection method along with Krestchmann configuration has been employed for the evaluation of parameters. The effects of the metal structures considered and its thicknesses on the transmitted spectrum of the proposed sensor is analysed by transfer matrix method. The proposed configuration will surely be a promising candidate for high performance bio-sensing applications.
THEORETICAL STUDY ON SURFACE PLASMON RESONANCE BASED FIBER OPTIC SENSORS USING PLATINUM -TMDC BILAYERS
(VIT , Chennai, 2020-01-08) Subanya S; Rajesh K.B
A surface plasmon resonance based fiber optic sensor with Platinum (Pt) coated with Transition Metal Dichalcogenides (TMDCs) - Molybdenum disulfide (MoS2), Molybdenum diselenide (MoSe2), Tungsten disulfide (WS2) and Tungsten diselenide (WSe2) is theoretically studied and analyzed (taking a metal and a TMDC at a time). The attenuated total internal reflection method along with Krestchmann configuration has been used to analyze the performance of the sensor. The sensitivity of the sensor increases linearly with increase in refractive index of the sensing medium for all thickness of Co and Ni (from 20 nm to 60 nm) and for increase in the number of TMDC layer. SPR sensor with 60 nm Platinum and five layers of WS2 exhibits highest sensitivity of 4798.4 nm/RIU. The utilization of Pt instead of Noble metals like gold and silver improves the performance of the sensor. The proposed WS2 assisted sensor will surely be a promising candidate for high performance sensing applications.