arXiv subjects

Rajadurai Chandrasekar

Publications and source records attributed to Rajadurai Chandrasekar.

8 recordsLinked to original sources

arXiv2026

Large-Area Patternable Solar-Powered Bistable Organic Crystalline Film for Nonlinear Optical Communication

Reversible control of crystal symmetry offers a powerful route to programmable optical functionality. However, achieving solid-state bistability between centrosymmetric and non-centrosymmetric crystalline phases remains a formidable challenge; examples of materials that enable stable switching of second-order nonlinear optical (NLO) responses are exceptionally rare. Here we report a solar-powered, symmetry-bistable organic material based on the photoisomerizable molecule (E/Z)-2-(4-(4-bromophenyl)thiazol-2-yl)-3-(4- (dimethylamino)phenyl)acrylonitrile (E/Z-BTDPA). The crystallizable E- and Z-isomers adopt distinct molecular packing arrangements that reversibly toggle between these states, controlling second-order NLO activity. The E-form exhibits strong second-harmonic generation (SHG), whereas the Z-form is SHG-inactive and displays twophoton luminescence. This bistable behavior is retained in flexible thin films, where sunlight-driven photoisomerization enables reversible photoswitching of the second-order electric susceptibility (\c{hi} 2), large-area optical patterning, and real-time NLO communication via waveform generation and text-string transcription at telecommunication wavelengths. This sustainable strategy bypasses rigid inorganic architectures, establishing photoinduced symmetry bistability as a scalable paradigm for all-optical computing and advanced communication networks.

physics.optics↗

arXiv2025

Unveiling Mechanical Motions in Non-linear Optical Organic Micro Ring Resonators

This work demonstrates the multifaceted dynamic motion and three-dimensional (3D) spatial manipulation of organic micro ring resonators (MRRs). The MRRs are fabricated via surface-tension-assisted self-assembly of 2,2'-((1E,1'E)-hydrazine-1,2-diylidenebis(methaneylylidene))bis(3,5-dibromophenol) (HDBP), exhibiting nonlinear optical (NLO) emission and frequency comb-type whispering gallery modes. Interestingly, the MRRs are micromechanically reconfigurable into various strained architectures, including lifting, transferring, vertical standing, axial spinning, and wheel-like rolling, using an atomic force microscopy cantilever tip. The MRRs retained their photonic traits throughout these dynamic motions, underscoring their mechanical robustness. Notably, the demonstration of axial spinning and rolling locomotion extends the manipulation capabilities beyond two-dimensional control, enabling complete 3D spatial control. These results establish a foundational platform for next-generation NLO mechanophotonic systems, where reconfigurable smart and soft photonic elements can be dynamically controlled with high spatial precision.

physics.optics↗

arXiv2025

Organic Crystal Active Waveguide as an All-Angle Signal Receiver and Transmission Platform for Visible Light Communication

Organic crystal waveguides, known for excellent light-guiding and photonic versatility, present a promising alternative to conventional optical media in visible light communication (VLC) systems. In a novel approach, the high photoluminescence quantum yield organic crystal 2,2dash-((1E,1Edash)-hydrazine-1,2-diylidenebis(methaneylylidene))diphenol (SAA) is used as an optical waveguide medium for real-time data communication in the visible range, employing a microcontroller unit with on off keying modulation. Leveraging its spectral properties, the SAA crystal demonstrates dual active and passive waveguiding capabilities for signal modulation. Error-free signal detection is achieved thanks to the smooth, defect-free surface morphology of the crystal. The relationship between incident angle and light intensity reveals stable fluorescence under narrow angle excitation, positioning the crystal as an all-angle signal receiver that surpasses conventional optical fibers. A real time data transfer setup is demonstrated, enabling direct transmission from a serial interface and accurate reconstruction of grayscale images. This represents the first implementation of a fully organic crystal-based VLC platform, integrating wavelength conversion, omnidirectional waveguiding, and real time signal processing. The results establish a foundation for compact, efficient, and integrable photonic communication technologies.

physics.optics↗

arXiv2025

Precision Thermo-Welding of Polymer Microspheres into Periodically Organized, Hybrid, Mechanically Rollable Coupled-Resonator Optical Waveguides

Polymer microspherical resonators that trap light are crucial structures for on-chip and on-board integration in nanophotonic applications. Using advanced micromanipulation and thermo-welding methods, we successfully create welded polystyrene-based coupled-resonator optical waveguides (CROWs) with customized lengths, shapes, and optical characteristics. Through the thermal fusion of blue, green, and red fluorophore-doped polystyrene microspheres, multi-fluorescent cohesive units are created from dimeric to henicosameric periodic arrangements. Detailed micro-spectroscopy studies reveal CROWs' capability to support optical whispering-gallery modes. The periodic arrangements of different fluorophore-doped resonators within the CROW facilitate efficient guided transmission of light via both active and passive mechanisms in opposite directions. The welded structures exhibit mechanically driven rolling motion, confirming their integration as cohesive units. These findings highlight the versatility and performance of thermo-welded polymer microsphere-based waveguides, paving the way for scalable, low-cost photonic devices in sensing, modulation, and light guiding, emphasizing their role in future integrated photonics.

physics.optics↗

arXiv2025

Hierarchical Serpentine-like Organic Crystal Optical Waveguides for Artificial Neural Networks

Optical components and circuits that deal with multiple signal generation and processing are quintessential for artificial neural networks. Herein, we present a proof-of-concept four-layered organic optical artificial neural network (ANN)-like architecture, constructed from flexible organic crystals of (E)-1-(((5-methylpyridin-2-yl)imino)methyl)naphthalene-2-ol (MPyIN), employing an atomic force microscopy cantilever tip-based mechanical micromanipulation technique. Initially, the strategic selection of four MPyIN crystal active waveguides of varying lengths, mechanically bending them into serpentine-like forms, followed by their hierarchical integration, creates neuron-like, four-layered interconnected optical waveguides with six optical synapses. The synapses in the ANN-like architecture enable parallel transmissions of passive optical signals via evanescent coupling across multiple paths through various layers of the serpentine-shaped optical waveguides. Notably, the feedforward mechanism allows the synapses to multiply and split the optical signal generated at any input into four diverging signals with varying magnitudes. Here, certain outputs deliver a mixed signal (passive and active) due to diverging and converging optical transmission paths. This hierarchical, ANN-like tiny architecture paves the way for the development of smart optical neural networks utilizing multiple emissive and phase-changing organic crystals.

physics.optics↗

arXiv2024

Mechanophotonics: Pseudo-plastic Organic Crystal as a Fermat Spiral Optical Waveguide

An unprecedented organic Fermat spiral optical waveguide (FSOW) self transducing green fluorescence is fabricated using a pseudo-plastic (E)-1-(((5-bromopyridin-2-yl)imino)methyl)naphthalene-2-ol crystal. A 1.618-millimeter-long crystal is initially bent into a hairpin-like bent waveguide. Later, a meticulous mechanophotonic strategy is employed to sculpt the hairpin-like bent waveguide into the Fermat spiral geometry, covering a compact area of 330x238 um2. The optical signal in FSOW survives two sharp 180-degree turns to produce optical output. The remarkably low bending-induced optical loss in FSOW can be ascribed to the smooth-defect-free surface morphology of the crystal. The development of such versatile optical components capable of transducing light through sharp bends is pivotal for realizing large-scale all-organic photonic circuits.

physics.optics↗

arXiv2024

Powering Monolithic and Hybrid Organic Optical Waveguides via Integrated Focused Micro-LEDs for Sustainable Photonic Circuits

In the domain of mechanophotonics, achieving real-time applicability of organic crystals in visible light communication (VLC) technologies necessitates affordable light-emitting diodes (LEDs) as sources of light to run photonic devices through sustainable methods. Here in, we demonstrate an efficient strategy to excite (Z)-3-(3',5'-bis(trifluoromethyl)-[1,1'-biphenyl]-4-yl)-2-(4-methoxyphenyl) acrylonitrile (CF3OMe), 9,10-bis(phenylethynyl)anthracene (BPEA) and 2,2'-((1E,1'E)-hydrazine-1,2-diylidenebis(methaneylylidene))diphenol (SAA) flexible crystal waveguides utilizing UV LED source and transduce respective blue, orange and yellow fluorescence signals. The capability of the focused LED lies in its ability to (i) energize mechanically bent crystals at an angle of 180°, (ii) evanescently excite the FL of a SAA waveguide using the FL of CF3OMe waveguide through energy transfer, and (iii) excite and split different signals in a 2X2 hybrid directional coupler based on SSA-BPEA crystals. These demonstrations underscore the practicality of the proposed technique for sustainable applications in photonic systems related to VLC.

physics.optics↗

arXiv2022

Micromanufacturing of geometrically- and dimensionally-precise molecular single-crystal photonic micro-resonators via focused ion beam milling

Highly reproducible manufacturing of organic optical crystals with well-defined geometry and dimension is important to realize industrially relevant all-organic microelectronic and nanophotonic components, and photonic integrated circuits. Here, we demonstrate programmed shape and size alteration of perylene crystal resonators into disk and rectangular geometries using focused-ion beam milling technique. Due to highly reproducible nature of the employed technique, the fabricated smaller sized disk and rectangular crystal resonators displaying shape and size dependent optical modes are suitable for commercial nanophotonic applications.

physics.optics↗