Prof. Varun Raghunathan Profile

Prof. Varun Raghunathan

at Indian Institute of Science Bengaluru

SPIE Involvement:

Author

Publications (32)

Proceedings Article | 13 March 2024 Presentation + Paper

Fiber-based higher dimensional quantum key distribution implementation using time-bin qudits

Gokul A., Harinee Natarajan, Varun Raghunathan

Proceedings Volume 12911, 129110C (2024) https://doi.org/10.1117/12.3002155

KEYWORDS: Sensors, Quantum protocols, Quantum key distribution, Quantum encoding, Quantum systems, Quantum experiments, Pulse signals, Quantum numbers, Quantum detection, Quantum hardware

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Proceedings Article | 13 March 2024 Presentation + Paper

Experimental demonstration of resonant third-harmonic generation using quasi-BIC resonances in silicon elliptical dimer metasurfaces with nanodisk couplers

Urmila Bag, Lal Krishna A. S., Jyothsna K. M., Varun Raghunathan

Proceedings Volume 12897, 1289703 (2024) https://doi.org/10.1117/12.3002169

KEYWORDS: Third harmonic generation, Nonlinear optics

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Proceedings Article | 8 March 2024 Presentation + Paper

Demonstration of gigabits-per-second two-user NOMA using laser-based indoor optical wireless communication

Sathisha Ramachandrapura Nagaraju, Faheem Ahmad, Varun Raghunathan

Proceedings Volume 12894, 128940J (2024) https://doi.org/10.1117/12.3002196

KEYWORDS: Receivers, Visible light communication, Simulations, Transmitters, Wireless communications, Laser optics, MATLAB, Forward error correction, Orthogonal frequency division multiplexing, Modulation

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Proceedings Article | 8 March 2024 Presentation + Paper

Enhanced sum frequency generation using vertically stacked Mie resonators

Rabindra Biswas, Felix Vennberg, Ajith Padyana Ravishankar, Srinivasan Anand, Varun Raghunathan

Proceedings Volume 12884, 128840D (2024) https://doi.org/10.1117/12.3002407

KEYWORDS: Sum frequency generation, Resonators, Emission wavelengths, Gallium arsenide, Optical resonators, Electric fields, Signal detection, Nonlinear optics, Near field optics, Microresonators

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Proceedings Article | 17 March 2023 Presentation + Paper

Chiral harmonic generation studies from partially etched amorphous silicon nanodisk arrays

Jayanta Kumar Deka, Jyothsna K.M., Rabindra Biswas, Varun Raghunathan

Proceedings Volume 12423, 124230A (2023) https://doi.org/10.1117/12.2650517

KEYWORDS: Second harmonic generation, Polarization, Amorphous silicon, Signal detection, Harmonic generation, Nonlinear optics, Silicon, Scanning electron microscopy, Polarized light

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Proceedings Article | 17 March 2023 Presentation + Paper

Enhanced four wave mixing from MoS2 disks supporting higher-order anapole resonance

Rabindra Biswas, Asish Prosad, Lal Krishna, Varun Raghunathan

Proceedings Volume 12423, 1242308 (2023) https://doi.org/10.1117/12.2650009

KEYWORDS: Molybdenum, Resonators, Resonance enhancement, Four wave mixing, Electric fields, Scattering, Optical resonators, Simulations, Second harmonic generation

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Proceedings Article | 15 March 2023 Presentation + Paper

Reconfigurable multi-beam steering using segmented spatial light modulator for indoor optical wireless communication

Faheem Ahmad, Varun Raghunathan

Proceedings Volume 12429, 124290U (2023) https://doi.org/10.1117/12.2650412

KEYWORDS: Beam steering, Spatial light modulators, Diffraction, Blazed gratings, Diffraction gratings, Wireless communications, Aberration correction, Spatial resolution, Beam diameter, Visible light communication

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Proceedings Article | 15 March 2023 Presentation + Paper

Hybrid LED-laser transmitter for colour-tunable gigabit-per-second class indoor visible light communication

Faheem Ahmad, Varun Raghunathan

Proceedings Volume 12429, 124290Z (2023) https://doi.org/10.1117/12.2651054

KEYWORDS: Visible light communication, Transmitters, Light sources and illumination, Light emitting diodes, Receivers, Blue lasers, Beam divergence, Diffusers, Color, Signal intensity

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Proceedings Article | 8 March 2023 Presentation + Paper

Comparison of high speed quantum random number generators based on ASE-ASE and ASE-LASER beating

Shreyam Maity, Asish Prosad, Harinee Natarajan, Varun Raghunathan

Proceedings Volume 12446, 1244610 (2023) https://doi.org/10.1117/12.2649916

KEYWORDS: Quantum random number generation, Analog to digital converters, Quantum beats, Quantum numbers, Bandpass filters, Tunable filters, Signal detection, Optical filters, Clocks, Background noise

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Proceedings Article | 27 May 2022 Presentation + Paper

Focal field engineered infrared-sensitive third-order sum frequency generation microscopy

Jyothsna Konkada Manattayil, Lal Krishna A. S., Hyunmin Kim, Varun Raghunathan

Proceedings Volume 12144, 121440K (2022) https://doi.org/10.1117/12.2621764

KEYWORDS: Microscopy, Sum-frequency generation, Polarization, Infrared imaging

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Proceedings Article | 5 March 2022 Presentation + Paper

Enhanced second harmonic generation from vertically stacked multilayer gallium selenide separated by low-index PMMA spacer layer

Rabindra Biswas, Asish Prosad, Lal Krishna A.S., Sruti Menon, Varun Raghunathan

Proceedings Volume 12003, 1200307 (2022) https://doi.org/10.1117/12.2609737

KEYWORDS: Second-harmonic generation, Gases, Polymethylmethacrylate, Image enhancement, Harmonic generation, Gallium, Silicon, Optimization (mathematics), Nonlinear optics, Wave propagation

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Proceedings Article | 5 March 2022 Presentation + Paper

Quasi-BIC resonances in amorphous germanium zero contrast gratings with dual asymmetric step profile for mid infrared frequency up-conversion

Lal Krishna A.S., Jyothsna K. M., Asish Prosad, Rabindra Biswas, Sruti Menon, Varun Raghunathan

Proceedings Volume 12011, 1201104 (2022) https://doi.org/10.1117/12.2609838

KEYWORDS: Mid-IR, Etching, Germanium, FT-IR spectroscopy, Photons, Visible radiation, Signal processing, Objectives, Sum-frequency generation, Reflectivity

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Proceedings Article | 5 March 2022 Presentation + Paper

Enhanced third harmonic generation in layered guided mode resonant structures using pupil engineered conical excitation

Sruti Menon, Jyothsna K. M., Rabindra Biswas, Asish Prosad, A.S. Lal Krishna, Varun Raghunathan

Proceedings Volume 12011, 1201105 (2022) https://doi.org/10.1117/12.2609869

KEYWORDS: Amorphous silicon, Silicon, Harmonic generation, Optical simulations, Gaussian beams, Resonance enhancement

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Proceedings Article | 4 March 2022 Presentation + Paper

Lighting fixture compatible NIR laser-based 16QAM-OFDM modulated visible light communication

Faheem Ahmad, Sathisha Ramachandrapura Nagaraju, Jyothsna K. M. , Varun Raghunathan

Proceedings Volume 12027, 120270V (2022) https://doi.org/10.1117/12.2609498

KEYWORDS: Near infrared, Light emitting diodes, Transmitters, Receivers, Diffusers, Semiconductor lasers, Modulation, Orthogonal frequency division multiplexing, Signal to noise ratio, Visible radiation

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Proceedings Article | 5 March 2021 Poster + Presentation + Paper

Design of variable link length indoor visible light communication system using focus tunable liquid lens

Faheem Ahmad, Varun Raghunathan

Proceedings Volume 11711, 117110M (2021) https://doi.org/10.1117/12.2578589

KEYWORDS: Telecommunications, Liquid lenses, Liquids, Visible radiation, Transmitters, Receivers, Optical communications, Lens design, Optical components

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Proceedings Article | 5 March 2021 Presentation + Paper

Silicon nitride based medium contrast gratings for generating longitudinally polarized resonant fields

Sruti Menon, Jyothsna K. M., Varun Raghunathan

Proceedings Volume 11695, 116951P (2021) https://doi.org/10.1117/12.2578214

KEYWORDS: Silicon, Spectroscopy, Polarization, Optical design, Objectives, Luminescence, Etching

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Proceedings Article | 5 March 2021 Presentation + Paper

Harmonic generation from 2D materials coupled to resonant metasurfaces

Varun Raghunathan, Jayanta Deka, Lal Krishna, Sruti Menon, Jyothsna K.M., Rabindra Biswas

Proceedings Volume 11688, 116880K (2021) https://doi.org/10.1117/12.2578039

KEYWORDS: Harmonic generation, Dielectric polarization, Second-harmonic generation, Silicon, Diffraction, Nonlinear optics, Gallium, Dielectrics, Chemical vapor deposition

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Proceedings Article | 1 April 2020 Presentation + Paper

Silicon-on-insulator based high-index contrast gratings for resonant enhancement of second harmonic generation from two-dimensional material

Jayanta Deka, Medha Dandu, Lal Krishna A. S., Sruti Menon, Jyothsna K. M., Kausik Majumdar, Varun Raghunathan

Proceedings Volume 11344, 113441Y (2020) https://doi.org/10.1117/12.2555800

KEYWORDS: Nonlinear metamaterials, Silicon, Second-harmonic generation, Harmonic generation, Resonance enhancement, Near field optics, Light sources, Integrated optics, Etching, Diffraction

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Proceedings Article | 1 April 2020 Presentation + Paper

Silicon nitride based guided mode resonance structures for enhancement of nonlinear optical effects

Sruti Menon, Asish Prosad, Rabindra Biswas, Varun Raghunathan

Proceedings Volume 11345, 113451J (2020) https://doi.org/10.1117/12.2554525

KEYWORDS: Silicon, Amorphous silicon, Coating, Resonance enhancement, Silica, Etching, Optical design, Dielectrics, Polarization, Nanostructures

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Proceedings Article | 2 March 2020 Paper

Lens design-based optimization of path loss in a high data-rate indoor visible light communication link

Faheem Ahmad, Sathisha Ramachandrapura Nagaraju, Jyothsna K. M., Rabindra Biswas, Varun Raghunathan

Proceedings Volume 11272, 1127218 (2020) https://doi.org/10.1117/12.2545939

KEYWORDS: Transmitters, Receivers, Telecommunications, Semiconductor lasers, Lens design, Visible radiation, Modulation, Light emitting diodes, Optical communications, Sensors

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In this paper, lens design-based optimization of the optical system for a blue laser diode downconverted with remote phosphor based indoor visible light communication link is studied using optical raytracing and experimentally characterized for illumination/ communication performance. Data modulated 450nm blue laser-diode is used to excite a remote-phosphor to down-convert the blue spectrum to white which is transmitted over a direct line-of-sight free-space link and detected using an amplified p-i-n detector. The combination of transmit and receive lenses are optimized in Zemax ray-tracing software with the objective of minimizing the path loss or maximizing the light collection efficiency within the detector area when placed at different transmitter-to-receiver separation distance. It is found that contrary to the typical 1/d² dependence typically used in VLC system models, the path loss can be minimized at the required link distance by choosing the lens to phosphor and p-i-n detector distance at the transmitter and receiver side respectively. At the optimized location, the VLC link is experimentally characterized by transmitting digital data at a maximum rate of 700 Mbps and bit error rates (BER) obtained is much below 10^-3 . BER versus distance is also found to follow the inverse relation of the path-loss versus distance indicating that the optimized lens positions help in achieving improved data through-put due to minimization of the path losses. Optical spectra and color content measurements indicate that the optimized lens positioning results in enhanced blue content at the receive side due to efficient collection of the data modulated blue components at the expense of the green and red components of the down-converted white light. Further improvements to this link can be achieved by simultaneously optimizing performance at multiple wavelengths spanning blue, green and red wavelengths or using lower color temperature phosphors to improve illumination performance, albeit at the expense of some deterioration to the communication performance.

Proceedings Article | 25 February 2020 Paper

Silicon nitride waveguide platform for on-chip spectroscopy at visible and NIR wavelengths

Sushma Gali, Varun Raghunathan, Shankar Kumar Selvaraja

Proceedings Volume 11283, 112831I (2020) https://doi.org/10.1117/12.2545808

KEYWORDS: Waveguides, Raman spectroscopy, Spectroscopy, Silicon, Visible radiation, Low pressure chemical vapor deposition, Plasma enhanced chemical vapor deposition, Raman scattering, Near infrared

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Proceedings Article | 18 February 2020 Presentation + Paper

Layer-dependent third-harmonic generation in multi-layer SnSe2

Rabindra Biswas, Medha Dandu, Keshav Kumar Jha, Sruti Menon, Jyothsna K. M., Kaushik Majumdar, Varun Raghunathan

Proceedings Volume 11282, 112820R (2020) https://doi.org/10.1117/12.2544799

KEYWORDS: Microscopy, Harmonic generation, Second-harmonic generation, Signal detection, Atomic force microscopy, Third-harmonic generation, Tin, Absorption, Nonlinear optics, Optical microscopy

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Proceedings Article | 22 July 2019 Paper

A spatiotemporal analysis using second harmonic generation reveals enhancement of type I collagen polymerization by dermatan sulfate glycosaminoglycans

Keshav Kumar Jha, Purba Sarkar, Rabindra Biswas, Ramray Bhat, Varun Raghunathan

Proceedings Volume 11076, 110761G (2019) https://doi.org/10.1117/12.2526896

KEYWORDS: Collagen, Polymerization, Second-harmonic generation, Harmonic generation, Microscopy, Image enhancement, Image filtering, Proteins, Polymers, Cancer

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Proceedings Article | 4 March 2019 Presentation + Paper

Silicon-nitride-based medium-contrast gratings for resonant fluorescence enhancement in the visible wavelength range

Sruti Menon, Lal Krishna A. S., M. V. N. Surendra Gupta, Ameen E., Bala Pesala, Varun Raghunathan

Proceedings Volume 10928, 1092818 (2019) https://doi.org/10.1117/12.2508778

KEYWORDS: Silicon, Luminescence, Polarization, Refractive index, Rhodamine B, Optical design, Diffraction, Resonance enhancement

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Proceedings Article | 21 May 2018 Paper

Single- and multidimensional integrated optic photon sources for quantum communication

Rohit Ramakrishnan, Varun Raghunathan, Srinivas Talabattula

Proceedings Volume 10674, 106741J (2018) https://doi.org/10.1117/12.2307428

KEYWORDS: Quantum communications, Silicon, Four wave mixing, Quantum information processing, Integrated optics, Silicon photonics, Nonlinear optics

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Proceedings Article | 21 February 2018 Paper

High contrast grating based intrinsic fluorescence enhancing substrates for water contamination detection

M. V. N. Surendra Gupta, Ameen E., Sruti Menon, Lal Krishna A. S., Varun Raghunathan, Bala Pesala

Proceedings Volume 10542, 1054214 (2018) https://doi.org/10.1117/12.2289741

KEYWORDS: Luminescence, Water contamination, Industrial chemicals, Finite-difference time-domain method, Bacteria

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Proceedings Article | 8 February 2007 Paper

Si/Ge platform for lasers, amplifiers, and nonlinear optical devices based on the Raman effect

Ricardo Claps, Dimitrios Dimitropoulos, Varun Raghunathan, Sasan Fathpour, Bahram Jalali, Bernard Jusserand

Proceedings Volume 6485, 648510 (2007) https://doi.org/10.1117/12.699524

KEYWORDS: Silicon, Phonons, Raman scattering, Germanium, Scattering, Raman spectroscopy, Superlattices, Stereolithography, Acoustics, Optical amplifiers

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Proceedings Article | 25 October 2005 Paper

Silicon Raman amplifiers lasers and their applications

Bahram Jalali, Ozdal Boyraz, Varun Raghunathan, Dimitri Dimitropoulos, Prakash Koonath

Proceedings Volume 6014, 601402 (2005) https://doi.org/10.1117/12.630907

KEYWORDS: Silicon, Raman spectroscopy, Waveguides, Semiconductor lasers, Optical amplifiers, Raman scattering, Mid-IR, Laser applications, Continuous wave operation, Photonics

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Proceedings Article | 27 August 2005 Paper

Optical continuum generation on a silicon chip

Bahram Jalali, Ozdal Boyraz, Prakash Koonath, Varun Raghunathan, Tejaswi Indukuri, Dimitri Dimitropoulos

Proceedings Volume 5931, 59310Q (2005) https://doi.org/10.1117/12.622619

KEYWORDS: Waveguides, Silicon, Phase shifts, Absorption, Scanning probe microscopy, Raman scattering, Resonators, Kerr effect, Optical filters, Optical amplifiers

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Proceedings Article | 7 July 2005 Open Access

Silicon Raman laser, amplifier, and wavelength converter

Bahram Jalali, Ozdal Boyraz, Dimitri Dimitropoulos, Varun Raghunathan

Proceedings Volume 5840, (2005) https://doi.org/10.1117/12.608446

KEYWORDS: Silicon, Raman spectroscopy, Waveguides, Semiconductor lasers, Raman scattering, Phonons, Optical amplifiers, Fiber lasers, Modulation, Scattering

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Proceedings Article | 7 March 2005 Paper

Scaling laws of nonlinear silicon nanophotonics

Bahram Jalali, Ozdal Boyraz, Dimitri Dimitropoulos, Varun Raghunathan

Proceedings Volume 5730, (2005) https://doi.org/10.1117/12.590831

KEYWORDS: Waveguides, Silicon, Phase shifts, Raman spectroscopy, Interfaces, Absorption, Kerr effect, Switching, Raman scattering, Electronics

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Proceedings Article | 18 August 2004 Paper

Wavelength conversion using parametric Raman scattering in silicon microstructures

Bahram Jalali, Varun Raghunathan, Ricardo Claps, Dimitrios Dimitropoulos

Proceedings Volume 5451, (2004) https://doi.org/10.1117/12.549917

KEYWORDS: Waveguides, Silicon, Raman spectroscopy, Signal to noise ratio, Signal attenuation, Raman scattering, Dispersion, Absorption, Birefringence, Phase matching

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Showing 5 of 32 publications

Conference Committee Involvement (3)

AI and Optical Data Sciences III

24 January 2022 | San Francisco, California, United States

AI and Optical Data Sciences II

6 March 2021 | Online Only, California, United States

AI and Optical Data Sciences

4 February 2020 | San Francisco, California, United States

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