Prof. Sridhar Krishnaswamy Profile

Prof. Sridhar Krishnaswamy

Professor of Mechanical Engineering at Northwestern Univ

SPIE Involvement:

Conference Program Committee | Author

Publications (75)

Proceedings Article | 9 May 2024 Presentation + Paper

Fiber-optic temperature sensor based on embedded rare-earth luminescent nanoparticles

Akhilesh Kumar Pathak, Sachin Kulkarni, Sridhar Krishnaswamy

Proceedings Volume 12951, 1295122 (2024) https://doi.org/10.1117/12.3010975

KEYWORDS: Temperature sensors, Nanoparticles, Sensors, Optical fibers, Temperature metrology, Fiber optics sensors, Fiber optics, Ytterbium, Single mode fibers, Femtosecond phenomena

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Proceedings Article | 9 May 2024 Presentation + Paper

Two-photon 3D printed active polymer ring resonators on the tip of optical fibers for temperature sensing

Akhilesh Kumar Pathak, Sachin Kulkarni, Sridhar Krishnaswamy

Proceedings Volume 12951, 1295121 (2024) https://doi.org/10.1117/12.3010972

KEYWORDS: Optical fibers, Nanoparticles, Optical resonators, Upconversion, Erbium, Ytterbium, Sensors, Mixtures, 3D printing

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Proceedings Article | 25 April 2023 Presentation + Paper

Multiscale multiphase 3D printing of photonic devices and sensors for system health monitoring

Abhishek Kottaram Amrithanath, Sridhar Krishnaswamy

Proceedings Volume 12488, 124880V (2023) https://doi.org/10.1117/12.2658502

KEYWORDS: Waveguides, 3D printing, Resonators, Polymers, Photonic devices, Erbium, Upconversion, Sensors, Nanoparticles, Photoresist materials

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Proceedings Article | 24 November 2021 Paper

3D printed lens on optical fiber tip for imaging applications

Long Han, Heming Wei, Zhangli Wu, Fufei Pang, Tingyun Wang, Sridhar Krishnaswamy

Proceedings Volume 12065, 120651P (2021) https://doi.org/10.1117/12.2605798

KEYWORDS: Optical fibers, Imaging systems, Lithography, Digital micromirror devices, 3D printing, Optics manufacturing, Multimode fibers

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Proceedings Article | 24 November 2021 Paper

High-sensitive FBG-based adaptive fiber laser acoustic sensing system

Zhe Gong, Heming Wei, Zhangli Wu, Fufei Pang, Tingyun Wang, Sridhar Krishnaswamy

Proceedings Volume 12065, 120652U (2021) https://doi.org/10.1117/12.2606754

KEYWORDS: Fiber Bragg gratings, Sensors, Signal detection, Fiber lasers, Sensing systems, Fiber optics sensors

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Proceedings Article | 10 October 2020 Presentation + Paper

Design of high-sensitive optical fiber acoustic sensor based on a photonic crystal fiber

Zhe Gong, Yuanyuan Meng, Heming Wei, Fufei Pang, Tingyun Wang, Sridhar Krishnaswamy

Proceedings Volume 11554, 115540Q (2020) https://doi.org/10.1117/12.2573133

KEYWORDS: Sensors, Optical fibers, Acoustics, Optical design, Photonic crystal fibers, Fiber optics sensors, Optical sensing, Ultrasonography, Scientific research, Nondestructive evaluation

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Proceedings Article | 1 April 2019 Paper

Femtosecond laser fabricated Fabry-Perot sensors on optical fiber tip for acoustic sensor

Heming Wei, Sridhar Krishnaswamy

Proceedings Volume 10972, 1097215 (2019) https://doi.org/10.1117/12.2514416

KEYWORDS: Sensors, Acoustics, Fiber lasers, Optical fibers, Fabry–Perot interferometers, Fiber optics sensors

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SPIE Journal Paper | 28 March 2019

Functionalized fiber-optic long-period grating with reduced cladding size for humidity sensing

Heming Wei, Chee Tan, Abhishek Amrithanath, Sridhar Krishnaswamy

OE, Vol. 58, Issue 03, 037105, (March 2019) https://doi.org/10.1117/12.10.1117/1.OE.58.3.037105

KEYWORDS: Cladding, Sensors, Humidity, Fiber optics sensors, Fiber optics, Refractive index, Temperature metrology, Corrosion, Thin films, Single mode fibers

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Proceedings Article | 27 March 2019 Paper

A novel special optical waveguide structure with magneto-optic nonreciprocal phase shift under transversely applied magnetic field

Dengwei Zhang, Liang Cui, Heming Wei, Abhishek Kottaram Amrithanath, Sridhar Krishnaswamy, Xiaowu Shu

Proceedings Volume 10970, 1097030 (2019) https://doi.org/10.1117/12.2522615

KEYWORDS: Waveguides, Magnetism, Phase shifts, Magnetic sensors, Magneto-optics, Refractive index, Polymers, Light wave propagation, Sensors, Wave propagation

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Proceedings Article | 7 March 2019 Paper

Direct laser writing of optical biosensor based on photonic Floquet topological insulator for protein detection

Abhishek Kottaram Amrithanath, Heming Wei, Sridhar Krishnaswamy

Proceedings Volume 10895, 108950Y (2019) https://doi.org/10.1117/12.2511158

KEYWORDS: Waveguides, Light wave propagation, Multiphoton lithography, Refractive index, Optical biosensors, Biomedical optics, Optical simulations, Device simulation, Biosensors, Biosensing

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Proceedings Article | 4 March 2019 Paper

Direct laser writing of smart polymer photonic devices for ultrasound detection

Heming Wei, Abhishek Amrithanath, Sridhar Krishnaswamy

Proceedings Volume 10922, 109220F (2019) https://doi.org/10.1117/12.2511226

KEYWORDS: Sensors, Waveguides, Signal detection, Polymers, Photonic devices, Ultrasonics, Multiphoton lithography

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Proceedings Article | 27 February 2019 Paper

Multi-wavelength erbium-doped fiber ring lasers based on an optical fiber tip interferometer

Heming Wei, Abhishek Amrithanath, Sridhar Krishnaswamy

Proceedings Volume 10914, 1091420 (2019) https://doi.org/10.1117/12.2511227

KEYWORDS: Fiber lasers, Optical fibers, Sensors, Tunable lasers, Fabry–Perot interferometry, Optical filters

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Proceedings Article | 27 March 2018 Presentation + Paper

High-frequency ultrasonic sensor arrays based on optical micro-ring resonators

Heming Wei, Abhishek Amrithanath, Sridhar Krishnaswamy

Proceedings Volume 10600, 1060003 (2018) https://doi.org/10.1117/12.2296273

KEYWORDS: Microrings, Sensors, Ultrasonics, Resonators, Waveguides, Polymeric sensors

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Proceedings Article | 27 March 2018 Presentation + Paper

Grating based high-frequency ultrasonic sensors

Heming Wei, Abhishek Amrithanath, Sridhar Krishnaswamy

Proceedings Volume 10598, 105982K (2018) https://doi.org/10.1117/12.2296335

KEYWORDS: Sensors, Ultrasonics, Fiber Bragg gratings, Waveguides, Signal detection, Structural health monitoring, Bragg gratings, Two photon polymerization

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Proceedings Article | 23 March 2018 Presentation + Paper

DNT detection using microspheres coated with NaYF4-Yb3+,Er3+-nanocrystals functionalized with PAA/PAH layers

Abhishek Kottaram Amrithanath, Heming Wei, Sridhar Krishnaswamy

Proceedings Volume 10597, 105970C (2018) https://doi.org/10.1117/12.2296465

KEYWORDS: Upconversion, Erbium, Resonators, Sensors, Silica, Ytterbium, Bioalcohols, Neptunium, Nanocrystals, Argon

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Proceedings Article | 12 April 2017 Paper

Direct laser writing of polymer micro-ring resonator ultrasonic sensors

Heming Wei, Sridhar Krishnaswamy

Proceedings Volume 10168, 1016830 (2017) https://doi.org/10.1117/12.2256364

KEYWORDS: Sensors, Ultrasonics, Microrings, Integrated optics, Optical lithography, Waveguides, Ultrasonography, Single mode fibers, Fiber lasers

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Proceedings Article | 5 April 2017 Presentation + Paper

Reflective SOA-based fiber Bragg grating ultrasonic sensing system with two wave mixing interferometric demodulation

Heming Wei, Sridhar Krishnaswamy

Proceedings Volume 10170, 1017027 (2017) https://doi.org/10.1117/12.2256362

KEYWORDS: Fiber Bragg gratings, Ultrasonics, Sensing systems, Two wave mixing, Semiconductor optical amplifiers, Interferometry, Sensors, Acoustic emission, Fiber lasers, Fiber optics sensors

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SPIE Journal Paper | 27 May 2016

Grapefruit photonic crystal fiber sensor for gas sensing application

Chuanyi Tao, Heming Wei, Yinian Zhu, Sridhar Krishnaswamy

OE, Vol. 55, Issue 05, 057103, (May 2016) https://doi.org/10.1117/12.10.1117/1.OE.55.5.057103

KEYWORDS: Sensors, Thin films, Cladding, Photonic crystal fibers, Gas sensors, Refractive index, Humidity, Thin film deposition, Optical engineering, Coating

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Proceedings Article | 16 April 2016 Paper

Photonic crystal fiber modal interferometer for explosives detection

Chuanyi Tao, Heming Wei, Sridhar Krishnaswamy

Proceedings Volume 9802, 98021K (2016) https://doi.org/10.1117/12.2218634

KEYWORDS: Sensors, Photonic crystal fibers, Interferometers, Explosives detection, Single mode fibers, Cladding, Coating, Spatial frequencies, Molecules

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Proceedings Article | 1 April 2016 Paper

Reflective SOA fiber cavity adaptive laser source for measuring dynamic strains

Heming Wei, Chuanyi Tao, Sridhar Krishnaswamy

Proceedings Volume 9805, 980526 (2016) https://doi.org/10.1117/12.2217699

KEYWORDS: Fiber Bragg gratings, Structural health monitoring, Intelligence systems, Michelson interferometers, Fiber lasers, Sensors, Signal detection, Ferroelectric materials, Optical fibers

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Proceedings Article | 1 April 2016 Paper

Photonic crystal fiber based chloride chemical sensors for corrosion monitoring

Heming Wei, Chuanyi Tao, Sridhar Krishnaswamy

Proceedings Volume 9805, 98052A (2016) https://doi.org/10.1117/12.2217700

KEYWORDS: Refractive index, Cladding, Water, Environmental monitoring

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Proceedings Article | 23 March 2015 Paper

Phase-shifted helical long-period grating-based temperature-insensitive optical fiber twist sensors

Ran Gao, Yinian Zhu, Sridhar Krishnaswamy, Jiang Yi

Proceedings Volume 9438, 94381D (2015) https://doi.org/10.1117/12.2084306

KEYWORDS: Phase shifts, Sensors, Temperature metrology, Optical fibers, Fiber optics sensors, Cladding, Polarization, Structured optical fibers, Fiber lasers, Thermal effects

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Proceedings Article | 2 June 2014 Paper

Fiber optic system for the real time detection, localization, and classification of damage in composite aircraft structures

Edgar Mendoza, John Prohaska, Connie Kempen, Yan Esterkin, Sunjian Sun, Sridhar Krishnaswamy

Proceedings Volume 9157, 91577E (2014) https://doi.org/10.1117/12.2064895

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Proceedings Article | 9 March 2014 Paper

Facile fabrication of uniaxial nanopatterns on shape memory polymer substrates using a complete bottom-up approach

Zhongbi Chen, Sridhar Krishnaswamy

Proceedings Volume 9058, 90580E (2014) https://doi.org/10.1117/12.2045755

KEYWORDS: Shape memory polymers, Nanolithography, Nanostructures, Lithography

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Proceedings Article | 19 April 2013 Paper

Tunable fiber ring laser absorption spectroscopic sensors for gas detection

Shijie Zheng, Yinian Zhu, Sridhar Krishnaswamy

Proceedings Volume 8692, 869213 (2013) https://doi.org/10.1117/12.2001325

KEYWORDS: Fiber lasers, Absorption, Tunable lasers, Sensors, Cladding, Silver, Gas sensors, Laser spectroscopy, Mirrors, Absorption spectroscopy

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Proceedings Article | 19 April 2013 Paper

Sensing platforms for structural health monitoring

Shijie Zheng, Gautam Naik, Zhongbi Chen, Yinian Zhu, Sridhar Krishnaswamy

Proceedings Volume 8692, 869203 (2013) https://doi.org/10.1117/12.2016792

KEYWORDS: Sensors, Fiber Bragg gratings, Humidity, Resistance, Cladding, Fiber optics sensors, Demodulation, Molecules, Graphene, Oxides

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Proceedings Article | 19 April 2013 Paper

Large-area graphene-based thin films using rapid reduction of graphene-oxide

Gautam Naik, Adarsh Kaniyoor, Sundara Ramaprabhu, Sridhar Krishnaswamy

Proceedings Volume 8692, 86921C (2013) https://doi.org/10.1117/12.2012198

KEYWORDS: Graphene, X-rays, Thin films, Oxides, Carbon, Spectroscopy, Atmospheric modeling, Oxygen, Sodium, Scanning electron microscopy

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Proceedings Article | 20 April 2012 Paper

Multiple scattering of Lamb waves by multiple corrosion pits in a plate

Brandon Strom, Sridhar Krishnaswamy, Jan Achenbach

Proceedings Volume 8348, 834813 (2012) https://doi.org/10.1117/12.915127

KEYWORDS: Corrosion, Scattering, Wave plates, Multiple scattering, Waveguides, Spherical lenses, Transducers, Wave propagation, Systems modeling, Visualization

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Proceedings Article | 20 April 2012 Paper

Dynamic fiber Bragg grating strain sensor using a wavelength-locked tunable fiber ring laser

Yinian Zhu, Sridhar Krishnaswamy

Proceedings Volume 8348, 83482H (2012) https://doi.org/10.1117/12.915014

KEYWORDS: Fiber Bragg gratings, Tunable lasers, Sensors, Fiber lasers, Sensing systems, Signal detection, Ferroelectric materials, Reflectivity, Resonators, Demodulation

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Proceedings Article | 5 April 2012 Paper

Temperature insensitive all-fiber accelerometer using a photonic crystal fiber long-period grating interferometer

Shijie Zheng, Yinian Zhu, Sridhar Krishnaswamy

Proceedings Volume 8347, 83470A (2012) https://doi.org/10.1117/12.915019

KEYWORDS: Cladding, Sensors, Head, Fiber Bragg gratings, Carbon dioxide lasers, Photonic crystal fibers, Refractive index, Silica, Interferometers, Fiber optics

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Proceedings Article | 30 March 2012 Paper

Nanofilm-coated photonic crystal fiber long-period gratings with modal transition for high chemical sensitivity and selectivity

Shijie Zheng, Yinian Zhu, Sridhar Krishnaswamy

Proceedings Volume 8346, 83460D (2012) https://doi.org/10.1117/12.915050

KEYWORDS: Cladding, Refractive index, Capillaries, Coating, Polymers, Water, Chemical analysis, Sensors, Liquids, Biological and chemical sensing

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Proceedings Article | 28 March 2012 Paper

Fabrication of sub-micron unidirectional patterns on SMP substrates

Zhongbi Chen, Sridhar Krishnaswamy

Proceedings Volume 8342, 83420Z (2012) https://doi.org/10.1117/12.915053

KEYWORDS: Computer programming, Aluminum, Thin films, Atomic force microscopy, Shape memory polymers, Thermal effects, Photomicroscopy, Metals, Optical lithography, Solar cells

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Proceedings Article | 18 April 2011 Paper

Nanofilm-coated long-period fiber grating humidity sensors for corrosion detection in structural health monitoring

Shijie Zheng, Yinian Zhu, Sridhar Krishnaswamy

Proceedings Volume 7983, 79831A (2011) https://doi.org/10.1117/12.880478

KEYWORDS: Refractive index, Coating, Sensors, Cladding, Humidity, Water, Optical fibers, Corrosion, Carbon dioxide lasers, Nanostructures

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Proceedings Article | 15 April 2011 Paper

Damage detection in FRP structures using fiber Bragg grating dynamic strain sensing systems

Yan Zhu, Yinian Zhu, Li Hui, Sridhar Krishnaswamy

Proceedings Volume 7982, 79820E (2011) https://doi.org/10.1117/12.880817

KEYWORDS: Fiber Bragg gratings, Sensors, Fiber reinforced polymers, Fiber optics sensors, Acoustic emission, Structural health monitoring, Interferometers, Michelson interferometers, Demodulation, Sensor networks

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Proceedings Article | 14 April 2011 Paper

Regularization of pattern formation in metal/SMP bi-layer structures

Zhongbi Chen, Yun Young Kim, Qiaojian Huang, Sridhar Krishnaswamy

Proceedings Volume 7981, 798131 (2011) https://doi.org/10.1117/12.880514

KEYWORDS: Thin films, Photomicroscopy, Computer programming, Thermal effects, Atomic force microscopy, Shape memory polymers, Sensors, Solar cells, Chromium, 3D image processing

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Proceedings Article | 1 April 2011 Paper

Scattering of the lowest Lamb wave modes by a corrosion pit

Brandon Strom, Su Hao, Sridhar Krishnaswamy, Jan Achenbach

Proceedings Volume 7984, 79841V (2011) https://doi.org/10.1117/12.880534

KEYWORDS: Corrosion, Wave plates, Scattering, Spherical lenses, Superposition, Optical spheres, Aerospace engineering, Wave propagation, Acoustics, Inverse problems

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Proceedings Article | 9 September 2010 Paper

Multipoint dynamically reconfigure adaptive distributed fiber optic acoustic emission sensor (FAESense) system for condition based maintenance

Edgar Mendoza, John Prohaska, Connie Kempen, Yan Esterkin, Sunjian Sun, Sridhar Krishnaswamy

Proceedings Volume 7653, 765343 (2010) https://doi.org/10.1117/12.868139

KEYWORDS: Sensors, Acoustic emission, Fiber Bragg gratings, Fiber optics sensors, Fiber optics, Demodulation, Signal detection, Photonic integrated circuits, Electronics, Adaptive optics

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Proceedings Article | 9 April 2010 Paper

Numerical investigation of cladding mode overlap of evanescent waves with air channels in index-guiding photonic crystal fiber long-period gratings

Shijie Zheng, Yinian Zhu, Sridhar Krishnaswamy

Proceedings Volume 7650, 76501Q (2010) https://doi.org/10.1117/12.847621

KEYWORDS: Cladding, Optical fibers, Photonic crystal fibers, Sensors, Waveguides, Refractive index, Structured optical fibers, Fiber Bragg gratings, Fiber optics, Polarization

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Proceedings Article | 9 April 2010 Paper

The influence of disbond defects on Lamb wave testing in GLARE composites

Qiaojian Huang, Brad Regez, Sridhar Krishnaswamy

Proceedings Volume 7650, 76502P (2010) https://doi.org/10.1117/12.847625

KEYWORDS: Composites, Signal detection, Thermography, Ferroelectric polymers, Transducers, Wave plates, Inspection, Waveguides, Imaging systems, Sensors

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Proceedings Article | 7 April 2010 Paper

Interrogation of a wavelength tunable fiber Bragg grating sensor based ring laser for dynamic strain monitoring

Oluwaseyi Balogun, Yinian Zhu, Sridhar Krishnaswamy

Proceedings Volume 7648, 764802 (2010) https://doi.org/10.1117/12.848979

KEYWORDS: Fiber lasers, Sensors, Fiber Bragg gratings, Demodulation, Ferroelectric materials, Laser applications, Laser systems engineering, Tunable lasers, Laser sources, Laser resonators

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SPIE Journal Paper | 1 March 2010 Open Access

Real-time full-field photoacoustic imaging using an ultrasonic camera

Oluwaseyi Balogun, Brad Regez, Hao Zhang, Sridhar Krishnaswamy

JBO, Vol. 15, Issue 02, 021318, (March 2010) https://doi.org/10.1117/12.10.1117/1.3420079

KEYWORDS: Imaging systems, Ultrasonics, Cameras, Tissue optics, Photoacoustic imaging, Transducers, Real time imaging, Spatial resolution, Tissues, Pulsed laser operation

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Proceedings Article | 10 April 2009 Paper

A fiber Bragg grating based tunable laser source for quasi-static and dynamic strain monitoring

Oluwaseyi Balogun, Sridhar Krishnaswamy

Proceedings Volume 7295, 72950I (2009) https://doi.org/10.1117/12.815651

KEYWORDS: Fiber Bragg gratings, Sensors, Laser sources, Tunable lasers, Interferometers, Laser resonators, Demodulation, Reflectivity, Fiber lasers, Michelson interferometers

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Proceedings Article | 9 April 2009 Paper

Ultrasonic camera automatic image depth and stitching modifications for monitoring aerospace composites

Brad Regez, Goutham Kirikera, Martin Tan Hwai Yuen, Sridhar Krishnaswamy, Bob Lasser

Proceedings Volume 7295, 72952H (2009) https://doi.org/10.1117/12.815891

KEYWORDS: Ultrasonics, Cameras, Imaging systems, Inspection, Composites, Computer programming, Ultrasonography, Multichannel imaging systems, Image processing, Aerospace engineering

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Proceedings Article | 10 April 2008 Paper

Optimal demodulation of wavelength shifts in fiber Bragg grating sensors using an adaptive two wave mixing photorefractive interferometer

Oluwaseyi Balogun, Goutham Kirikera, Sridhar Krishnaswamy

Proceedings Volume 6932, 69322K (2008) https://doi.org/10.1117/12.778013

KEYWORDS: Sensors, Fiber Bragg gratings, Demodulation, Interferometers, Two wave mixing, Crystals, Photodetectors, Ferroelectric materials, Signal to noise ratio, Beam splitters

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Proceedings Article | 19 May 2007 Paper

Continuous sensors for mode selective actuation and reception of waves for structural health monitoring of woven composite laminates

Goutham Kirikera, Gabriela Petculescu, Sridhar Krishnaswamy, Jan Achenbach

Proceedings Volume 6532, 65321H (2007) https://doi.org/10.1117/12.715235

KEYWORDS: Sensors, Electrodes, Composites, Wave propagation, Transducers, Structural health monitoring, Actuators, Sensor networks, Aluminum, Analog electronics

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Proceedings Article | 30 March 2006 Paper

Multiplexed adaptive two-wave mixing wavelength demodulation of fiber Bragg grating sensor for monitoring both dynamic and quasi-static drifts

Yi Qiao, Sridhar Krishnaswamy

Proceedings Volume 6167, 616708 (2006) https://doi.org/10.1117/12.658679

KEYWORDS: Sensors, Fiber Bragg gratings, Demodulation, Two wave mixing, Crystals, Multiplexing, Fiber optics sensors, Laser crystals, Electronics, Spectrum analysis

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Proceedings Article | 28 March 2006 Paper

A high-resolution real-time ultrasonic imaging system for NDI applications

Yi Zhou, Gabriela Petculescu, Igor Komsky, Sridhar Krishnaswamy

Proceedings Volume 6177, 617717 (2006) https://doi.org/10.1117/12.658785

KEYWORDS: Imaging systems, Ultrasonography, Ultrasonics, Composites, Transducers, Ferroelectric materials, Beam splitters, Cameras, Inspection, Polymers

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Proceedings Article | 16 May 2005 Paper

Adaptive two-wave mixing wavelength demodulation of fiber Bragg grating sensor for monitoring dynamic strains

Yi Qiao, Yi Zhou, Sridhar Krishnaswamy

Proceedings Volume 5758, (2005) https://doi.org/10.1117/12.598041

KEYWORDS: Sensors, Fiber Bragg gratings, Demodulation, Signal detection, Two wave mixing, Fiber optics sensors, Crystals, Interferometers, Multiplexing, Sensor networks

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Proceedings Article | 9 May 2005 Paper

An acoustic nonlinearity measurement technique with built-in couplant effect elimination

L. Sun, S. Kulkarni, B. Moran, S. Krishnaswamy, J. Achenbach

Proceedings Volume 5768, (2005) https://doi.org/10.1117/12.598058

KEYWORDS: Transducers, Acoustics, Aluminum, Ultrasonics, Harmonic generation, Signal attenuation, Signal generators, Ferroelectric materials, Error analysis, Sun

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Proceedings Article | 9 May 2005 Paper

Photoacoustic characterization of the mechanical properties of thin film materials

Feifei Zhang, Sridhar Krishnaswamy, Dong Fei, Douglas Rebinsky

Proceedings Volume 5766, (2005) https://doi.org/10.1117/12.598028

KEYWORDS: Thin films, Photoacoustic spectroscopy, Acoustics, Silicon, Silicon films, Femtosecond phenomena, Ultrasonics, Dispersion, Aluminum, Signal detection

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Proceedings Article | 9 May 2005 Paper

A scanning laser source and a microcantilever ultrasound receiver for detection of surface flaws in microdevices

Younghoon Sohn, Sridhar Krishnaswamy

Proceedings Volume 5768, (2005) https://doi.org/10.1117/12.598522

KEYWORDS: Ultrasonography, Near field, Receivers, Laser sintering, Silicon, Ultrasonics, Laser sources, Laser scattering, Scattering, Reactive ion etching

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In recent work at Northwestern University, we have shown that near-field scattering of ultrasound generated by a Scanning Laser Source (SLS) can be used to effectively identify surface flaws in macroscale structures. In past work, the laser ultrasound source was in the near-field of a scatterer and a piezoelectric detector was used to measure the ultrasound in the far field. It was observed that distinct variations are observed in the far-field signals as the SLS scans past surface-breaking flaws. These changes were attributed to the near-field scatterer redirecting parts of the ultrasonic beam (which might otherwise have gone into the bulk of the object) towards the far-field detector. We now propose an extension of the SLS approach to map defects in microdevices by bringing both the generator and the receiver to the near-field scattering region of the defects. For the purpose of near-field ultrasound measurement, the receiving transducer has to be made very small as well. To facilitate this, silicon microcantilever probes are fabricated and their acoustical characteristics are first investigated. Silicon cantilevers with tip and chip body are fabricated using isotropic reactive ion etching and anisotropic KOH etching. To characterize the free cantilever vibration, the chip body with the microcantilever is excited by an ultrasonic transducer and a Michelson interferometer is used to monitor the cantilever motion. The fundamental frequency of the microcantilever is measured and compared with analytically calculated fundamental frequency assuming the cross sections of the cantilevers are rectangular. Next, the performance of the fabricated microcantilevers as ultrasound detectors is investigated. The microcantilever is used essentially as a profilometer by contacting it to the specimen surface. Surface and bulk acoustic waves are generated with specific narrowband frequencies and the surface ultrasonic displacements are detected using the microcantilever probe. Next, broadband ultrasound is generated by a laser source and the resulting surface acoustic displacements are monitored using the microcantilever probe in the near-field of the source. Finally, both the laser-generated ultrasonic source and the microcantilever probe are used to monitor near-field scattering by a surface-breaking defect.

SPIE Journal Paper | 1 April 2003

Response of a fiber Bragg grating ultrasonic sensor

Pavel Fomitchov, Sridhar Krishnaswamy

OE, Vol. 42, Issue 04, (April 2003) https://doi.org/10.1117/12.10.1117/1.1556372

KEYWORDS: Fiber Bragg gratings, Sensors, Ultrasonics, Fiber optics sensors, Waveguides, Signal detection, Acoustics, Wave propagation, Modulation, Optical fibers

Proceedings Article | 23 October 2001 Paper

Characterization of thin film MEMS using photo-acoustic microscopy

Carmen Hernandez, Todd Murray, Sridhar Krishnaswamy

Proceedings Volume 4400, (2001) https://doi.org/10.1117/12.445606

KEYWORDS: Thin films, Silicon, Aluminum, Silicon films, Microelectromechanical systems, Ultrasonics, Acoustics, Microscopy, Acousto-optics, Adaptive optics

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Proceedings Article | 24 July 2001 Paper

Distributed photoacoustic system for cure monitoring of composites

Pavel Fomitchov, Yeong Kim, Alexei Kromine, Sridhar Krishnaswamy, Jan Achenbach, Isaac Daniel

Proceedings Volume 4335, (2001) https://doi.org/10.1117/12.434188

KEYWORDS: Ultrasonics, Composites, Sensors, Fiber lasers, Signal attenuation, Manufacturing, Fiber optics, Epoxies, Fiber optics sensors, Signal detection

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SPIE Journal Paper | 1 July 2001

Multiplexed interferometer for ultrasonic imaging applications

Todd Murray, Sridhar Krishnaswamy

OE, Vol. 40, Issue 07, (July 2001) https://doi.org/10.1117/12.10.1117/1.1385171

KEYWORDS: Interferometers, Signal detection, Multiplexing, Crystals, Phased array optics, Phased arrays, Laser crystals, Ultrasonics, Signal to noise ratio, Optical components

Proceedings Article | 31 August 2000 Paper

Fiberized laser ultrasonic source for process monitoring and biomedical applications

Pavel Fomitchov, Alexei Kromine, Sridhar Krishnaswamy, Jan Achenbach

Proceedings Volume 4074, (2000) https://doi.org/10.1117/12.397872

KEYWORDS: Ultrasonics, Glasses, Fiber lasers, Fiber optics, Head, Fiber optics sensors, Laser applications, Inspection, Ultrasonography, Sensors

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Proceedings Article | 31 August 2000 Paper

Applications of scanning laser source technique for detection of surface-breaking defects

Alexei Kromine, Pavel Fomitchov, Sridhar Krishnaswamy, Jan Achenbach

Proceedings Volume 4076, (2000) https://doi.org/10.1117/12.397958

KEYWORDS: Ultrasonics, Laser sintering, Signal detection, Defect detection, Ferroelectric materials, Laser sources, Signal attenuation, Ultrasonography, Inspection, Transducers

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SPIE Journal Paper | 1 July 2000

Extrinsic and intrinsic fiberoptic Sagnac ultrasound sensors

Pavel Fomitchov, Sridhar Krishnaswamy, Jan Achenbach

OE, Vol. 39, Issue 07, (July 2000) https://doi.org/10.1117/12.10.1117/1.602583

KEYWORDS: Ultrasonics, Signal detection, Ultrasonography, Sensors, Interferometers, Surface finishing, Photodetectors, Fiber optics, Speckle

Proceedings Article | 4 February 1999 Paper

Intrinsic fiber optic Sagnac ultrasound sensor for process monitoring in composite structures

Pavel Fomitchov, Sridhar Krishnaswamy, Jan Achenbach

Proceedings Volume 3589, (1999) https://doi.org/10.1117/12.339960

KEYWORDS: Sensors, Ultrasonics, Ultrasonography, Composites, Fiber optics sensors, Signal detection, Fiber optics, Signal attenuation, Epoxies, Transducers

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Proceedings Article | 20 March 1997 Paper

Laser-based ultrasonics for QNDE applications

Pavel Fomitchov, Lewis Wang, J. Scott Steckenrider, Sridhar Krishnaswamy, Jan Achenbach

Proceedings Volume 2921, (1997) https://doi.org/10.1117/12.269810

KEYWORDS: Ultrasonics, Optical fibers, Signal detection, Ultrasonography, Sagnac interferometers, Signal to noise ratio, Signal generators, Transducers, Ferroelectric materials, Interferometers

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Proceedings Article | 20 March 1997 Paper

Phase-shifting dynamic holographic interferometry using BSO photorefractive crystals

Bruno Pouet, Sridhar Krishnaswamy

Proceedings Volume 2921, (1997) https://doi.org/10.1117/12.269808

KEYWORDS: Crystals, Holograms, Holographic interferometry, Phase shifts, Holography, Signal to noise ratio, Interferometry, Diffraction, Scattering, Laser crystals

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Proceedings Article | 20 March 1997 Paper

Fourier processing of shearing interferometric fringe patterns

Hansuk Lee, Lewis Wang, Sridhar Krishnaswamy

Proceedings Volume 2921, (1997) https://doi.org/10.1117/12.269832

KEYWORDS: Fringe analysis, Prisms, Polymethylmethacrylate, Fourier transforms, Interferometry, Finite element methods, Collimation, Interferometers, Shearing interferometers, Phase measurement

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Proceedings Article | 17 July 1996 Paper

Real-time visualization of dynamic holographic interferometric images using photorefractive crystals

Bruno Pouet, Sridhar Krishnaswamy

Proceedings Volume 2860, (1996) https://doi.org/10.1117/12.276317

KEYWORDS: Crystals, Diffraction, Imaging systems, Holographic interferometry, Charge-coupled devices, Polarization, Two wave mixing, Holography, Laser crystals, Image quality

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Proceedings Article | 17 July 1996 Paper

Surface profile determination by additive-subtractive phase-modulated ESPI with Fourier analysis

Lewis Wang, Sridhar Krishnaswamy

Proceedings Volume 2860, (1996) https://doi.org/10.1117/12.276302

KEYWORDS: Fringe analysis, Speckle pattern, Fourier transforms, Mirrors, Speckle, CCD cameras, Modulation, Video, Bragg cells, Spherical lenses

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SPIE Journal Paper | 1 March 1996

Additive-subtractive speckle interferometry: extraction of phase data in noisy environments

Lewis Wang, Sridhar Krishnaswamy

OE, Vol. 35, Issue 03, (March 1996) https://doi.org/10.1117/12.10.1117/1.600649

KEYWORDS: Fringe analysis, Phase shifts, Speckle pattern, Speckle interferometry, Phase interferometry, Phase measurement, Interferometry, Image processing, Ferroelectric materials, Speckle

Proceedings Article | 18 August 1995 Paper

Laser ultrasound system with embedded fiber optic interferometric sensor

John Dorighi, Sridhar Krishnaswamy, Jan Achenbach

Proceedings Volume 2622, (1995) https://doi.org/10.1117/12.216818

KEYWORDS: Fiber optics sensors, Ultrasonography, Sensors, Fiber lasers, Signal detection, Epoxies, Transducers, Fiber optics, Interferometers, Acoustic emission

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Proceedings Article | 18 August 1995 Paper

Application of photorefractive crystals for holographic interferometry of vibrating diffuse specimens

Bruno Pouet, Sridhar Krishnaswamy

Proceedings Volume 2622, (1995) https://doi.org/10.1117/12.216849

KEYWORDS: Crystals, Signal to noise ratio, Diffraction, Polarization, Holograms, Holography, Diffraction gratings, Interferometers, Speckle, Holographic interferometry

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Proceedings Article | 23 June 1995 Paper

Additive-subtractive speckle interferometry: phase measurements in noisy conditions

Lewis Wang, Sridhar Krishnaswamy

Proceedings Volume 2545, (1995) https://doi.org/10.1117/12.212666

KEYWORDS: Fringe analysis, Phase shifts, Phase measurement, Speckle pattern, Speckle interferometry, Visibility, Interferometry, Speckle, Modulation, Bragg cells

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Proceedings Article | 20 April 1995 Paper

Embedded fiber optic ultrasonic sensors and generators

John Dorighi, Sridhar Krishnaswamy, Jan Achenbach

Proceedings Volume 2574, (1995) https://doi.org/10.1117/12.207765

KEYWORDS: Sensors, Fiber optics sensors, Ultrasonography, Ultrasonics, Laser stabilization, Fiber optics, Phase shifts, Fabry–Perot interferometers, Interferometers, Epoxies

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Proceedings Article | 10 December 1993 Paper

Electronic speckle techniques in noisy environments

Bruno Pouet, Sridhar Krishnaswamy

Proceedings Volume 2003, (1993) https://doi.org/10.1117/12.165485

KEYWORDS: Speckle, Phase shifts, Fringe analysis, Image processing, Phase modulation, Nondestructive evaluation, Interferometry, Modulation, Image acquisition, Phase shift keying

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Proceedings Article | 3 December 1993 Paper

Nondestructive testing of adhesively bonded structures using synchronized pressure stressing

Thomas Chatters, Bruno Pouet, Sridhar Krishnaswamy

Proceedings Volume 2001, (1993) https://doi.org/10.1117/12.163847

KEYWORDS: Speckle, Nondestructive evaluation, Speckle pattern, Phase modulation, Phase shift keying, Fringe analysis, Video, Modulation, Image processing, Inspection

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SPIE Journal Paper | 1 June 1993

Additive/subtractive decorrelated electronic speckle pattern interferometry

Bruno Pouet, Sridhar Krishnaswamy

OE, Vol. 32, Issue 06, (June 1993) https://doi.org/10.1117/12.10.1117/12.135841

KEYWORDS: Speckle, Speckle pattern, Fringe analysis, Image processing, Acoustics, Nondestructive evaluation, Interferometry, Video, CCD cameras, Charge-coupled devices

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Proceedings Article | 28 May 1993 Paper

ESPI with synchronized pressure stressing

Thomas Hale, Bruno Pouet, Sridhar Krishnaswamy

Proceedings Volume 1821, (1993) https://doi.org/10.1117/12.145561

KEYWORDS: Speckle, Speckle pattern, Image acquisition, Nondestructive evaluation, Video, CCD cameras, Aluminum, Image processing, Composites, Camera shutters

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Proceedings Article | 1 December 1991 Paper

Dynamic two-beam speckle interferometry

Mansour Ahmadshahi, Sridhar Krishnaswamy, Siavouche Nemat-Nasser

Proceedings Volume 1554, (1991) https://doi.org/10.1117/12.49505

KEYWORDS: Speckle, Speckle interferometry, Speckle pattern, Mechanics, High speed cameras, Image processing, Birefringence, Solids, Photography, Fringe analysis

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Proceedings Article | 1 December 1991 Paper

Crack-tip deformation field measurements using coherent gradient sensing

Hareesh Tippur, Sridhar Krishnaswamy, Ares Rosakis

Proceedings Volume 1554, (1991) https://doi.org/10.1117/12.49513

KEYWORDS: Solids, Wavefronts, Mechanics, Diffraction, Wave propagation, Reflection, Fringe analysis, Speckle, Birefringence, Polymethylmethacrylate

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Showing 5 of 75 publications

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Health Monitoring of Structural and Biological Systems XIX

17 March 2025 | Vancouver, Canada

Health Monitoring of Structural and Biological Systems XVIII

25 March 2024 | Long Beach, California, United States

Health Monitoring of Structural and Biological Systems XVII

13 March 2023 | Long Beach, California, United States

Health Monitoring of Structural and Biological Systems XVI

7 March 2022 | Long Beach, California, United States

Health Monitoring of Structural and Biological Systems XV

8 March 2021 | Online Only, California, United States

Health Monitoring of Structural and Biological Systems XIV

27 April 2020 | Online Only, California, United States

Health Monitoring of Structural and Biological Systems XIII

4 March 2019 | Denver, Colorado, United States

Health Monitoring of Structural and Biological Systems XII

5 March 2018 | Denver, Colorado, United States

Health Monitoring of Structural and Biological Systems XI

26 March 2017 | Portland, Oregon, United States

Health Monitoring of Structural and Biological Systems X

21 March 2016 | Las Vegas, Nevada, United States

Health Monitoring of Structural and Biological Systems IX

9 March 2015 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems VIII

10 March 2014 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems VII

11 March 2013 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems VI

12 March 2012 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems V

7 March 2011 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems IV

8 March 2010 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems III

9 March 2009 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems II

10 March 2008 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems

19 March 2007 | San Diego, California, United States

Health Monitoring and Smart NDE of Structural and Biological Systems V

27 February 2006 | San Diego, CA, United States

Health Monitoring and Smart Nondestructive Evaluation of Structural and Biological Systems IV

7 March 2005 | San Diego, CA, United States

Smart Nondestructive Evaluation and Health Monitoring of Structural and Biological Systems

3 March 2003 | San Diego, California, United States

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