Dr. Wilt Kao Profile

Dr. Wilt Kao

CTO at LongWave Photonics LLC

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Author

Publications (9)

Proceedings Article | 17 August 2024 Presentation

Compact terahertz spectrometer based on a metasurface

Wenye Ji, Jin Chang, Behnam Mirzaei, Marcel Ridder, Willem Jellema, Wilt Kao, Alan Lee, Jian Rong Gao, Paul Urbach, Aurèle J. Adam

Proceedings Volume PC13102, PC131020I (2024) https://doi.org/10.1117/12.3021392

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Proceedings Article | 16 August 2024 Presentation + Paper

Virtually Image Phased Array (VIPA): demonstration of the next generation direct detection spectrometer for velocity resolved spectroscopy in the far-infrared

Thomas Nikola, Bugao Zou, Gordon Stacey, Jake Connors, Nicholas Cothard, Alexander Kutyrev, Eric Mentzell, Karwan Rostem, Edward Wollack, Willem Jellema, Tsung-Yu Kao, Alan W. Lee

Proceedings Volume 13102, 131020F (2024) https://doi.org/10.1117/12.3020350

KEYWORDS: Cryostats, Quantum cascade lasers, Spectral resolution, Silicon, Reflectivity, Collimation, Spectroscopy, Mirrors, Parabolic mirrors, Dielectrics

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We have created and demonstrated a Virtually Imaged Phased Array (VIPA) device for velocity resolved spectroscopy in the far-IR and will present the first cryogenic (LHe) measurements of the spectral profile of a prototype VIPA at 115.7 µm. A VIPA is a compact spectral filter without moving parts that consists of a resonating cavity that generates angular dispersion due to constructive interference, and that can deliver an instantaneous spectrum with a resolving power of 100,000 or more. Coupled with superconducting direct detection detectors, the VIPA promises unsurpassed sensitivity at velocity resolutions > 3 km/s, making it a prime choice for spectroscopic instruments to observe e.g. protoplanetary disks to trace the gaseous building blocks out of which planets form. Due to their compactness and absence of moving parts, VIPAs are optimal for balloon and space-borne astronomical instruments like the NASA Pioneer Mission POEMM and the proposed NASA Probe Mission FIRSST. The prototype we have measured was made of a 3 × 5 × 1 cm block of high-purity float-zone silicon. The entrance and exit sides of the VIPA are highly parallel, and the entrance side was fully metallized (gold-coated) except for a narrow entrance slit resulting in a reflectivity of 100%, while the exit side was metallized with an inductive mesh resulting in a reflectivity of about 88%. The measurement was done using a custom testbed that included separate cryostats for a cryogenically cooled THz Quantum Cascade Laser (QCL) and the VIPA, as well as a warm pyroelectric detector. The QCL was tuned to a number of different frequencies near 2.59 THz and the detector was scanned along the dispersion direction. Our VIPA prototype achieved the designed resolving power of 15,000 and the spectral profile matched extremely well with the expectations from our simulations. We are now building a full testbed to straightforwardly measure and characterize VIPAs and other GHz/THz filters with resolving powers of order 100,000 using tuneable THz lasers.

Proceedings Article | 26 May 2016 Paper

Terahertz imaging with quantum cascade lasers

Alan Lee, Tsung-Yu Kao, Ian Zimmerman, Naoki Oda, Qing Hu

Proceedings Volume 9854, 98540R (2016) https://doi.org/10.1117/12.2224140

KEYWORDS: Quantum cascade lasers, Terahertz radiation, Sensors, Microbolometers, Imaging systems, Metals, Nondestructive evaluation, Silicon, Staring arrays, Interfaces

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Proceedings Article | 25 May 2016 Paper

THz QCLs for heterodyne receivers and wavelength modulation spectroscopy

Alan W. Lee, Tsung-Yu Kao, Ian Zimmerman, William T. Cole, Richard Thurston, Richard Saykally, Ningren Han, Qing Hu

Proceedings Volume 9836, 98362O (2016) https://doi.org/10.1117/12.2224158

KEYWORDS: Terahertz radiation, Quantum cascade lasers, Heterodyning, Receivers, Modulation, Sensors, Absorption, Signal detection, Spectroscopes, Microelectromechanical systems

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Proceedings Article | 23 July 2014 Paper

A 4.7THz heterodyne receiver for a balloon borne telescope

D. Hayton, J. Kloosterman, Y. Ren, T. Kao, J. Gao, T. Klapwijk, Q. Hu, C. Walker, J. Reno

Proceedings Volume 9153, 91531R (2014) https://doi.org/10.1117/12.2055790

KEYWORDS: Terahertz radiation, Receivers, Quantum cascade lasers, Heterodyning, Telescopes, Gas lasers, Stars, Oscillators, Temperature metrology, Spectroscopy

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Proceedings Article | 31 January 2014 Paper

Microstrip-antenna-coupled distributed feedback terahertz quantum-cascade lasers

Tsung-Yu Kao, Xiaowei Cai, Qing Hu, John Reno

Proceedings Volume 8993, 89930E (2014) https://doi.org/10.1117/12.2036604

KEYWORDS: Antennas, Terahertz radiation, Phase modulation, Quantum cascade lasers, Waveguides, Optical simulations, Finite element methods, Pulsed power, Scanning electron microscopy, Metals

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Proceedings Article | 23 February 2013 Paper

Terahertz quantum cascade laser based optical coherence tomography

Alan Lee, Tsung-Yu Kao, Qing Hu, John Reno

Proceedings Volume 8585, 858508 (2013) https://doi.org/10.1117/12.2001127

KEYWORDS: Quantum cascade lasers, Terahertz radiation, Interfaces, Mirrors, Optical coherence tomography, Tomography, Dielectrics, Antennas, Neodymium, Interferometers

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Proceedings Article | 24 September 2012 Paper

Stabilized HEB-QCL heterodyne spectrometer at super-terahertz

Y. Ren, D. Hayton, J. Hovenier, M. Cui, J. Gao, T. Klapwijk, S. Shi, T.-Y. Kao, Q. Hu, J. Reno

Proceedings Volume 8452, 845210 (2012) https://doi.org/10.1117/12.925651

KEYWORDS: Quantum cascade lasers, Spectroscopy, Terahertz radiation, Absorption, Heterodyning, Oscillators, Bolometers, Sensors, Actuators, Signal detection

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Proceedings Article | 15 July 2010 Paper

Heterodyne gas cell measurements at 2.9 THz using a quantum cascade laser as local oscillator

Y. Ren, J. R. Gao, J. N. Hovenier, R. Higgins, W. Zhang, A. Bell, B. Klein, T. Klapwijk, S. C. Shi, T.-Y. Kao, S. Kumar, Q. Hu, J. Reno

Proceedings Volume 7741, 774118 (2010) https://doi.org/10.1117/12.857658

KEYWORDS: Quantum cascade lasers, Terahertz radiation, Heterodyning, Receivers, Oscillators, Temperature metrology, Spectroscopy, Spectrometers, Astronomy, Spectroscopes

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Showing 5 of 9 publications

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