Dr. Abul K. Azad Profile

Dr. Abul K. Azad

at Ctr for Integrated Nanotechnologies

SPIE Involvement:

Conference Program Committee | Author | Editor

Proceedings Article | 2 October 2024 Presentation

Broadband terahertz vector beam generated by twisted effective media-based Q-plate

Yun-Seok Choi, Prashant Padmanabhan, Abul Azad

Proceedings Volume PC13141, PC1314109 (2024) https://doi.org/10.1117/12.3027522

KEYWORDS: Terahertz radiation, Silicon, Refractive index, Polarization, Multilayers, Design, Beam propagation method

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Proceedings Article | 13 May 2019 Presentation + Paper

Observation of the circular photogalvanic effect in the Weyl semimetal TaAs using THz emission spectroscopy

N. Sirica, R. Tobey, L. X. Zhao, G. F. Chen, B. Xu, R. Yang, B. Shen, D. Yarotski, P. Bowlan, S. Trugman, J.-X. Zhu, Y. M. Dai, A. Azad, N. Ni, X. G. Qiu, A. Taylor, R. Prasankumar

Proceedings Volume 10983, 1098314 (2019) https://doi.org/10.1117/12.2520318

KEYWORDS: Terahertz radiation, Crystals, Polarization, Metalloids, Physics, Solar energy, Emission spectroscopy, Second-harmonic generation, Transient nonlinear optics, Mid-IR

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Proceedings Article | 14 May 2018 Presentation + Paper

Low temperature dielectric properties of ammonium nitrate in terahertz regime

Abdur Rahman, David Moore, Abul Azad

Proceedings Volume 10657, 1065714 (2018) https://doi.org/10.1117/12.2309619

KEYWORDS: Dielectrics, Terahertz radiation, Absorption, Magnesium, Terahertz spectroscopy, Composites, Refractive index, Particles, Temperature metrology, Spectroscopy

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Proceedings Article | 29 April 2016 Paper

Temperature dependent terahertz properties of energetic materials

Abul Azad, Von Whitley, Kathryn Brown, Towfiq Ahmed, Christian Sorensen, David Moore

Proceedings Volume 9856, 98560W (2016) https://doi.org/10.1117/12.2225528

KEYWORDS: Explosives, Temperature metrology, Absorption, Terahertz radiation, Explosives, Crystals, Dielectrics, Phonons, Solids, Refractive index, Molecules

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Proceedings Article | 13 May 2015 Paper

Tuning of terahertz metamaterials’ resonances via near field coupling

Abul Azad, Dibakar Roy Chowdhury, Hou-Tong Chen, Antoinette Taylor

Proceedings Volume 9483, 94830G (2015) https://doi.org/10.1117/12.2182969

KEYWORDS: Metamaterials, Terahertz radiation, Resonators, Near field, Ultrafast phenomena, Inductance, Silicon, Electromagnetism, Near field optics, Picosecond phenomena

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Proceedings Article | 13 May 2015 Paper

Insight into fiber Bragg sensor response at 100-MHz interrogation rates under various dynamic loading conditions

George Rodriguez, Marcelo Jaime, Chuck Mielke, Fedor Balakirev, Abul Azad, Richard Sandberg, Bruce Marshall, Brandon La Lone, Bryan Henson, Laura Smilowitz, Mark Marr-Lyon, Tom Sandoval

Proceedings Volume 9480, 948004 (2015) https://doi.org/10.1117/12.2086707

KEYWORDS: Fiber Bragg gratings, Sensors, Magnetism, Explosives, Clocks, Magnetostrictive materials, Temperature metrology, Oscilloscopes, Crystals, Dispersion

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Proceedings Article | 1 May 2012 Paper

Thermal and ultrafast optical tuning of ultrathin high-temperature superconducting terahertz metamaterials

Ranjan Singh, Jie Xiong, Dibakar Roy Chowdhury, Hao Yang, Abul Azad, Stuart Trugman, Q. X. Jia, Antoinette Taylor, Hou-Tong Chen

Proceedings Volume 8423, 84230Y (2012) https://doi.org/10.1117/12.922161

KEYWORDS: Metamaterials, Superconductors, Terahertz radiation, Ultrafast phenomena, Thermography, Temperature metrology, Technetium, Switching, Metals, Picosecond phenomena

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Proceedings Article | 21 February 2011 Paper

Ultrafast optical control of terahertz surface plasmons in subwavelength hole-arrays at room temperature

Abul Azad, Hou-Tong Chen, Antoinette Taylor, Weili Zhang, John O'Hara

Proceedings Volume 7937, 79370B (2011) https://doi.org/10.1117/12.873488

KEYWORDS: Terahertz radiation, Gallium arsenide, Surface plasmons, Silicon, Switching, Ultrafast phenomena, Dielectrics, Metals, Superlattices, Modulation

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Extraordinary optical transmission through subwavelength metallic hole-arrays has been an active research area since its first demonstration. The frequency selective resonance properties of subwavelength metallic hole arrays, generally known as surface plasmon polaritons, have potential use in functional plasmonic devices such as filters, modulators, switches, etc. Such plasmonic devices are also very promising for future terahertz applications. Ultrafast switching or modulation of the resonant behavior of the 2-D metallic arrays in terahertz frequencies is of particular interest for high speed communication and sensing applications. In this paper, we demonstrate ultrafast optical control of surface plasmon enhanced resonant terahertz transmission in two-dimensional subwavelength metallic hole arrays fabricated on gallium arsenide based substrates. Optically pumping the arrays creates a thin conductive layer in the substrate reducing the terahertz transmission amplitude of both the resonant mode and the direct transmission. Under low optical fluence, the terahertz transmission is more greatly affected by resonance damping than by propagation loss in the substrate. An ErAs:GaAs nanoisland superlattice substrate is shown to allow ultrafast control with a switching recovery time of ~10 ps. We also present resonant terahertz transmission in a hybrid plasmonic film comprised of an integrated array of subwavelength metallic islands and semiconductor hole arrays. Optically pumping the semiconductor hole arrays favors excitation of surface plasmon resonance. A large dynamic transition between a dipolar localized surface plasmon mode and a surface plasmon resonance near 0.8 THz is observed under near infrared optical excitation. The reversal in transmission amplitude from a stop-band to a pass-band and up to π/ 2 phase shift achieved in the hybrid plasmonic film make it promising in large dynamic phase modulation, optical changeover switching, and active terahertz plasmonics.

Proceedings Article | 23 February 2010 Paper

Metamaterial based devices for terahertz imaging

Xomalin Peralta, Michael Wanke, Igal Brener, Jerry Waldman, William Goodhue, J. Li, Abul Azad, Hou-Tong Chen, Antoinette Taylor, John O'Hara

Proceedings Volume 7562, 75620I (2010) https://doi.org/10.1117/12.846823

KEYWORDS: Terahertz radiation, Metamaterials, Polarization, Modulators, Attenuators, Quantum cascade lasers, Modulation, Wave plates, Millimeter wave imaging, Control systems

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Proceedings Article | 3 September 2009 Paper

Ultrafast carrier dynamics in semiconductor nanowires

R. Prasankumar, P. Upadhya, Q. Li, N. Smith, S. G. Choi, A. Azad, D. Talbayev, G. Wang, A. Fischer, J. Hollingsworth, S. Trugman, S. Picraux, A. Taylor

Proceedings Volume 7406, 74060E (2009) https://doi.org/10.1117/12.828022

KEYWORDS: Germanium, Semiconductors, Gallium nitride, Picosecond phenomena, Ultrafast laser spectroscopy, Carrier dynamics, Optical spectroscopy, Nanostructures, Ultrafast measurement systems, Nanowires

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Proceedings Article | 7 February 2009 Paper

Terahertz metamaterials

Hou-Tong Chen, John O'Hara, Abul Azad, Willie Padilla, Richard Averitt, Antoinette Taylor

Proceedings Volume 7214, 721417 (2009) https://doi.org/10.1117/12.812052

KEYWORDS: Terahertz radiation, Metamaterials, Modulation, Semiconductors, Picosecond phenomena, Silicon, Split ring resonators, Switching, Metals, Gallium arsenide

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