Prof. Vellara Pillai Mahadevan Profile

Prof. Vellara Pillai Mahadevan

Professor/Department Head at Univ of Kerala

SPIE Involvement:

Author

Publications (26)

Proceedings Article | 8 October 2018 Presentation + Paper

Feasibility analysis of unique ID (UID) generation for personal authentication of valuable documents using dorsal hand vein pattern

Sajan Ambadiyil, Reema Jayarajan, V. P. Mahadevan Pillai, Radhakrishna Prabhu

Proceedings Volume 10802, 108020H (2018) https://doi.org/10.1117/12.2325346

KEYWORDS: Veins, Biometrics, Feature extraction, Imaging devices, Cameras, Biological research, Infrared imaging, Edge detection, Iris recognition, Image acquisition

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Proceedings Article | 5 October 2017 Paper

Banknote authentication using chaotic elements technology

Sajan Ambadiyil, Krishnendu P.S., V.P. Mahadevan Pillai , Radhakrishna Prabhu

Proceedings Volume 10441, 1044104 (2017) https://doi.org/10.1117/12.2278343

KEYWORDS: Ultraviolet radiation, Chemical elements, Feature extraction, Image registration, Image compression, Image filtering, Printing, Computer security, Image processing, Image encryption

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Proceedings Article | 24 October 2016 Presentation + Paper

Holographic interferometry for security and forensic applications

Sajan Ambadiyil, Sreelekshmi R. C., V. P. Mahadevan Pillai, Radhakrishna Prabhu

Proceedings Volume 9995, 999502 (2016) https://doi.org/10.1117/12.2242153

KEYWORDS: Holographic interferometry, Forensic science, Holograms, 3D image processing, 3D printing, Modulation, Holography, 3D modeling, Security technologies, 3D displays

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SPIE Journal Paper | 19 October 2016

Climate sensitivity characteristics of tropical cirrus clouds using lidar measurements

Gopinathan Nair Motty, Malladi Satyanarayana, Glory Jayeshlal, Vellara P. Pillai

JARS, Vol. 10, Issue 04, 046005, (October 2016) https://doi.org/10.1117/12.10.1117/1.JRS.10.046005

KEYWORDS: Clouds, LIDAR, Climatology, Mass attenuation coefficient, Satellites, Environmental sensing, Aerosols, Crystals, Optical properties, Geometrical optics

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Proceedings Article | 9 May 2016 Paper

Lidar investigations on the structure and microphysical properties of cirrus at a tropical station Gadanki (13.50 N and 79.20 E), India

Gloryselvan Jayeshlal, Malladi Satyanarayana, Gopinathan Nair Motty, Reji Dhaman, Vasudevannair Krishnakumar, Vellara P. Mahadevan Pillai

Proceedings Volume 9876, 98761U (2016) https://doi.org/10.1117/12.2222294

KEYWORDS: LIDAR, Clouds, Aerosols, Climatology, Earth's atmosphere, Lawrencium, Ocean optics, Atmospheric particles, Mass attenuation coefficient, Backscatter

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Proceedings Article | 9 May 2016 Paper

Lidar studies on climate sensitivity characteristics of tropical cirrus clouds

G. S. Motty, G. S. Jayeshlal, Malladi Satyanarayana, V. P. Mahadevan Pillai

Proceedings Volume 9876, 98761X (2016) https://doi.org/10.1117/12.2223301

KEYWORDS: Clouds, LIDAR, Mass attenuation coefficient, Climatology, Crystals, Satellites, Geometrical optics, Atmospheric particles, Optical properties, Space based lasers

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Proceedings Article | 5 May 2016 Paper

Investigation of tropical cirrus cloud properties using ground based lidar measurements

Reji Dhaman, Malladi Satyanarayana, V. Krishnakumar, V. P. Mahadevan Pillai, G. S. Jayeshlal, K. Raghunath, M. Venkat Ratnam

Proceedings Volume 9876, 98760P (2016) https://doi.org/10.1117/12.2222314

KEYWORDS: Clouds, LIDAR, Optical properties, Atmospheric optics, Scattering, Crystals, Scalable video coding, Lawrencium, Climatology

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Proceedings Article | 5 May 2016 Paper

Investigation on the monthly variation of cirrus optical properties over the Indian subcontinent using cloud-aerosol lidar and infrared pathfinder satellite observation (Calipso)

Reji Dhaman, Malladi Satyanarayana, G. Jayeshlal, V. Mahadevan Pillai, V. Krishnakumar

Proceedings Volume 9876, 98762O (2016) https://doi.org/10.1117/12.2223653

KEYWORDS: Clouds, LIDAR, Ocean optics, Optical properties, Aerosols, Atmospheric particles, Infrared radiation, Earth observing sensors, Satellites, Climatology

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Proceedings Article | 5 May 2015 Paper

Microstructure encryption and decryption techniques in optical variable and invariable devices in printed documents for security and forensic applications

Sajan Ambadiyil, Jayan K. G, Radhakrishna Prabhu, V. P. Mahadevan Pillai

Proceedings Volume 9506, 95060I (2015) https://doi.org/10.1117/12.2179635

KEYWORDS: Computer security, Ultraviolet radiation, Image processing, Forensic science, UV optics, Image encryption, Optical fibers, Image enhancement, Security printing, Glasses

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SPIE Journal Paper | 26 March 2014

Lidar investigations on the optical and dynamical properties of cirrus clouds in the upper troposphere and lower stratosphere regions at a tropical station, Gadanki, India (13.5°N, 79.2°E)

Vasudevannair Krishnakumar, Malladi Satyanarayana, Soman Radhakrishnan, Reji Dhaman, Glory Jayeshlal, Gopinathan Nair Motty, Vellara Mahadevan Pillai, Karnam Raghunath, Madineni Ratnam, Duggirala Rao, Pindlodi Sudhakar

JARS, Vol. 8, Issue 01, 083659, (March 2014) https://doi.org/10.1117/12.10.1117/1.JRS.8.083659

KEYWORDS: Clouds, LIDAR, Turbulence, Crystals, Lawrencium, Radar, Atmospheric optics, Aerosols, Mass attenuation coefficient, Multiple scattering

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SPIE Journal Paper | 1 January 2011

Investigations on the physical and optical properties of cirrus clouds and their relationship with ice nuclei concentration using LIDAR at Gadanki, India (13.5°N, 79.2°E)

Vasudevannair Krishnakumar, Malladi Satyanarayana, Soman Radhakrishnan, Reji Dhaman, Vellara Mahadevan Pillai, Karnam Raghunath, M. Venkat Ratnam, Duggirala Rao, Pindlodi Sudhakar

JARS, Vol. 5, Issue 1, 053567, (January 2011) https://doi.org/10.1117/12.10.1117/1.3662877

KEYWORDS: Clouds, LIDAR, Crystals, Optical properties, Lawrencium, Aerosols, Atmospheric optics, Backscatter, Analytical research, Signal attenuation

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SPIE Journal Paper | 1 November 2010

Optical properties of cirrus clouds at a tropical Indian station Gadanki, Tirupati (13.5°N, 79.2°E)

Soman Radhakrishnan, Malladi Satyanarayana, Vasudevannair Krishnakumar, Vellara Mahadevan Pillai, Karnam Reghunath, M. Venkat Ratnam, Duggirala Ramakrishna Rao

JARS, Vol. 4, Issue 01, 043559, (November 2010) https://doi.org/10.1117/12.10.1117/1.3525238

KEYWORDS: Clouds, Crystals, LIDAR, Backscatter, Lawrencium, Optical properties, Aerosols, Mass attenuation coefficient, Atmospheric particles, Atmospheric modeling

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SPIE Journal Paper | 1 January 2010

Laser radar characterization of atmospheric aerosols in the troposphere and stratosphere using range dependent lidar ratio

Satyanarayana Malladi, Radhakrishnan Radha, V. P. Mahadevan Pillai, Veerabuthiran Sangipillai, Presennakumar Bhargavan, Murty Vinjanampaty, Reghunath Karnam

JARS, Vol. 4, Issue 01, 043503, (January 2010) https://doi.org/10.1117/12.10.1117/1.3306573

KEYWORDS: LIDAR, Aerosols, Lawrencium, Mass attenuation coefficient, Atmospheric particles, Signal attenuation, Backscatter, Optical properties, Atmospheric modeling, Troposphere

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Proceedings Article | 29 December 2008 Paper

Influence of inland aerosol loading on the monsoon over Indian subcontinent

M. Satyanarayana, V. Krishnakumar, V. Mahadevan Pillai, S. Radhakrishnan, K. Raghunath

Proceedings Volume 7153, 715314 (2008) https://doi.org/10.1117/12.804935

KEYWORDS: Clouds, Aerosols, LIDAR, Atmospheric particles, Backscatter, Telescopes, Atmospheric monitoring, Atmospheric modeling, Optical properties, Mass attenuation coefficient

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Proceedings Article | 29 December 2008 Paper

Microphysical parameters of cirrus clouds using lidar at a tropical station, Gadanki, Tirupati (13.5 degrees N, 79.2 degrees E), India

M. Satyanarayana, S-R. Radhakrishnan, V. Krishnakumar, V. Mahadevan Pillai, K. Raghunath

Proceedings Volume 7153, 71530Y (2008) https://doi.org/10.1117/12.806390

KEYWORDS: Clouds, LIDAR, Aerosols, Atmospheric particles, Mass attenuation coefficient, Earth's atmosphere, Optical properties, Troposphere, Signal attenuation, Ocean optics

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Proceedings Article | 9 December 2008 Paper

On deriving the accurate aerosol extinction profiles in the troposphere and lower stratosphere using the range dependent scattering ratio

M. Satyanarayana, S. Radhakrishnan, V. Mahadevanpillai, V. Krishnakumar

Proceedings Volume 7153, 71530W (2008) https://doi.org/10.1117/12.804930

KEYWORDS: LIDAR, Aerosols, Scattering, Signal attenuation, Atmospheric modeling, Mass attenuation coefficient, Atmospheric particles, Backscatter, Climatology, Data modeling

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SPIE Journal Paper | 1 September 2008

A dual-wavelength narrow-linewidth laser system, with ultranarrow wavelength spacing, is proposed and demonstrated. The operation principle of the laser system is based on the pump-induced thermal effects of the Er-Yb-doped fiber distributed Bragg reflect

V. P. Sudeep Kumar, B. Unnikrishnan Nair, Vellara Mahadevan Pillai, V. Unnikrishnan Nayar

OE, Vol. 47, Issue 09, 094401, (September 2008) https://doi.org/10.1117/12.10.1117/1.2978950

KEYWORDS: Cladding, Refractive index, Thermal effects, Optical fibers, Absorption, Optical engineering, Wavelength tuning, Mechanically induced long-period fiber gratings, Fiber amplifiers, Optical amplifiers

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SPIE Journal Paper | 1 April 2008

High data rate laser transmitter based on a diode double end-pumped Nd:YAG laser with linearly polarized output for free space laser communication

S. K. Sudheer, S. Sivabalan, N. Venugopalan Pillai, V. P. Mahadevan Pillai, Zachariah Alex, V. Unnikrishnan Nayar, J. Raina

OE, Vol. 47, Issue 04, 044201, (April 2008) https://doi.org/10.1117/12.10.1117/1.2911714

KEYWORDS: Nd:YAG lasers, Diodes, Semiconductor lasers, Free space optical communications, Q switching, Temperature metrology, Crystals, Laser crystals, Transmitters, Optical engineering

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Proceedings Article | 13 March 2008 Paper

Processing of natural diamond using nanosecond and picosecond lasers: relative merits and demerits

S. K. Sudheer, Bharat Kakadia, V. P. Mahadevan Pillai, George Shafeev, Alexander Simakin

Proceedings Volume 6881, 68811G (2008) https://doi.org/10.1117/12.786994

KEYWORDS: Diamond, Nd:YAG lasers, Diodes, Laser processing, Lamps, Raman spectroscopy, Laser cutting, Pulsed laser operation, Scanning electron microscopy, Neodymium lasers

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SPIE Journal Paper | 1 October 2007

Characterization of a diode double-end pumped Nd:YVO₄ laser for high-bit-rate free-space and intersatellite communications

S. K. Sudheer, N. Venugopalan Pillai, V. P. Mahadevan Pillai, V. Unnikrishnan Nayar

OE, Vol. 46, Issue 10, 104201, (October 2007) https://doi.org/10.1117/12.10.1117/1.2790027

KEYWORDS: Q switching, Semiconductor lasers, Q switched lasers, Laser crystals, Diodes, Crystals, Pulsed laser operation, Nd:YAG lasers, Continuous wave operation, Free space optical communications

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SPIE Journal Paper | 1 July 2007

Errata: High-repetition-rate multiwavelength polarized air cooled solid-state laser source for light detection and ranging applications

Vellara Mahadevan Pillai, V. Unnikrishnan Nayar, S. K. Sudheer

OE, Vol. 46, Issue 07, 079801, (July 2007) https://doi.org/10.1117/12.10.1117/1.2768976

SPIE Journal Paper | 1 June 2007

High-repetition-rate multiwavelength polarized air cooled solid-state laser source for light detection and ranging applications

S. K. Sudheer, V. P. Mahadevan Pillai, V. Unnikrishnan Nayar

OE, Vol. 46, Issue 06, 064202, (June 2007) https://doi.org/10.1117/12.10.1117/1.2747637

KEYWORDS: Crystals, Nd:YAG lasers, Laser crystals, Thermal effects, LIDAR, Solid state lasers, Semiconductor lasers, Neodymium, Laser resonators, Laser scattering

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Proceedings Article | 12 December 2006 Paper

A high repetition rate multiwavelength polarized solid state laser source for long range lidar applications

S. Sudheer, V. P. Mahadevan Pillai, V. U. Nayar

Proceedings Volume 6409, 64091I (2006) https://doi.org/10.1117/12.697759

KEYWORDS: Diodes, Nd:YAG lasers, Laser crystals, Semiconductor lasers, Crystals, LIDAR, Neodymium, YAG lasers, Temperature metrology, Q switching

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Advances in Laser Technology and nonlinear Optical techniques can be effectively utilized for LIDAR applications in space and atmospheric sciences to achieve better flexibility and control of the available optical power. Using such devices, one can achieve highly accurate and resolved, measurement of the distribution for atmospheric scattering layers. In the present investigation a diode double end pumped high repetition rate, multi wavelength Nd:YAG laser is designed, fabricated and various laser beam parameters have been characterized for LIDAR applications. Nonlinear optical techniques have been employed to generate higher harmonics like 532nm, 355nm and 266nm for various spectral studies. The experimental setup mainly consists of two Fiber coupled pump laser diodes (Model FAP- 81-30C-800B, Coherent Inc, USA) with a maximum output power of 30Watt at a wavelength of 807-810nm at 30°C set temperature. A second harmonic LBO crystal cut for critical phase matching placed within the laser resonator is provided for converting a fraction of the fundamental beam to a second harmonic beam. A type II frequency tripling LBO nonlinear crystal (cut for critical phase matching) is also located inside the laser resonator. The third harmonic beam and the unconverted fundamental beam are then directed across a type I fourth harmonic LBO crystal cut for critical phase matching where a portion of the fundamental beam and a portion of the third harmonic beam are converted to a fourth harmonic frequency when both fundamental and third harmonic beams propagate through the frequency quadrupling crystal. The resulting beams which are the fundamental (1064nm), second harmonic (532nm), third harmonic (355nm) and fourth harmonic (266nm) are then directed to a fourth harmonic separator in which the fourth harmonic beam is separated from the fundamental beam. A maximum average power of 12W at 1064nm, 8W at 532nm, 5W at 355nm and 3W at 266nm have been measured at a repetition rate of 10KHz. A minimum pulse width of 25ns have been observed.

Proceedings Article | 8 December 2006 Paper

Determination of aerosol extinction coefficient profiles from LIDAR data using the optical depth solution method

John Aparna, S. K. Satheesh, V. P. Mahadevan Pillai

Proceedings Volume 6408, 64080Z (2006) https://doi.org/10.1117/12.697518

KEYWORDS: LIDAR, Aerosols, Mass attenuation coefficient, Atmospheric particles, Atmospheric optics, Signal attenuation, Scattering, Molecules, Light scattering, Absorption

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SPIE Journal Paper | 1 June 2006

Fractional thermal loading and effective stimulated-emission cross section of diode double-end-pumped Nd:YVO₄ crystal

S. K. Sudheer, V. P. Mahadevan Pillai, V. Unnikrishnan Nayar

OE, Vol. 45, Issue 06, 064201, (June 2006) https://doi.org/10.1117/12.10.1117/1.2212187

KEYWORDS: Crystals, Thermal effects, Laser crystals, Diodes, Semiconductor lasers, Resonators, Doping, Solid state lasers, Refractive index, Optical engineering

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SPIE Journal Paper | 1 April 2006

Micromachining of 316LVM stainless steel tubes using periodic acousto-optic modulation of pulsed Nd:YAG lasers for cardiovascular stent applications

S. Sudheer, V. P. Mahadevan Pillai, V. Unnikrishnan Nayar, Yavar Pothiawala, Devesh Kothwala, Dhiraj Kotadia

JM3, Vol. 5, Issue 02, 023010, (April 2006) https://doi.org/10.1117/12.10.1117/1.2201038

KEYWORDS: Laser cutting, Modulation, Acousto-optics, Nd:YAG lasers, Micromachining, Modulators, Scanning electron microscopy, Laser processing, Photomicroscopy, Biomedical optics

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Showing 5 of 26 publications

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