Dr. Stewart Wu Profile

Dr. Stewart Wu

at NASA Goddard Space Flight Ctr

SPIE Involvement:

Author

Publications (22)

Proceedings Article | 12 July 2023 Open Access

Open Access

Paper

Development of LISA laser system at NASA

Kenji Numata, Anthony Yu, Clifford Brambora, Jordan Camp, Molly Fahey, Ali Feizi, Kevin Heesh, Hua Jiao, Oleg Konoplev, Matthew Mullin, Scott Merritt, William Mamakos, Steve Marlow, Demetrios Poulios, Paula Pruessner, Michael Rodriguez, Aleksey Vasilyev, Stewart Wu, Xiaozhen Xu, Aaron Yevick

Proceedings Volume 12777, 1277738 (2023) https://doi.org/10.1117/12.2690342

KEYWORDS: Nanoimprint lithography, Design and modelling, Laminated object manufacturing, Space operations, Molybdenum, Laser development, Laser frequency, Laser optics, Semiconductor lasers, Laser systems engineering

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Proceedings Article | 23 April 2020 Presentation + Paper

Presentation + Paper

A new laser transmitter for methane and water vapor measurements at 1.65 µm

Haris Riris, Kenji Numata, Stewart Wu, Jes Sherman, Gordon Morrison, Henry Garrett, Milan Mashanovitch

Proceedings Volume 11410, 1141007 (2020) https://doi.org/10.1117/12.2558816

KEYWORDS: Methane, Optical parametric oscillators, Absorption, Mirrors, Photonics, Transmitters, Laser development, Laser optics, LIDAR

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Proceedings Article | 12 July 2019 Open Access

Open Access

Paper

The challenges of measuring methane from space with a lidar

H. Riris, K. Numata, S. Wu, M. Fahey, B. Gonzalez, X. Sun, J. Mao, M. Rodriguez

Proceedings Volume 11180, 1118027 (2019) https://doi.org/10.1117/12.2535998

KEYWORDS: LIDAR, Optical parametric oscillators, Absorption, Methane, Transmitters, Sensors, Er:YAG lasers, Fiber lasers, Laser applications, Aerospace engineering

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Proceedings Article | 20 February 2018 Presentation + Paper

Presentation + Paper

Fiber-based laser MOPA transmitter packaging for space environment

Mark Stephen, Anthony Yu, Jeffrey Chen, Kenji Numata, Stewart Wu, Brayler Gonzales, Lawrence Han, Molly Fahey, Michael Plants, Michael Rodriguez, Graham Allan, James Abshire, Jeffrey Nicholson, Anand Hariharan, William Mamakos, Brian Bean

Proceedings Volume 10513, 1051308 (2018) https://doi.org/10.1117/12.2290720

KEYWORDS: Fiber amplifiers, Optical amplifiers, Fiber lasers, Transmitters, Packaging, Pulsed laser operation, LIDAR

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Proceedings Article | 20 November 2017 Open Access

Open Access

Paper

LIDAR technology for measuring trace gases on Mars and Earth

H. Riris, J. Abshire, Allan Graham, William Hasselbrack, Mike Rodriguez, Xiaoli Sun, Clark Weaver, Jianping Mao, Randy Kawa, Steve Li, Kenji Numata, Stewart Wu

Proceedings Volume 10565, 105650G (2017) https://doi.org/10.1117/12.2309207

KEYWORDS: Methane, Carbon dioxide, Absorption, Mars, Carbon dioxide lasers, Oxygen, Gases, LIDAR, Clouds, Sensors

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Trace gases and their isotopic ratios in planetary atmospheres offer important but subtle clues as to the origins of a planet's atmosphere, hydrology, geology, and potential for biology. An orbiting laser remote sensing instrument is capable of measuring trace gases on a global scale with unprecedented accuracy, and higher spatial resolution that can be obtained by passive instruments.

For Earth we have developed laser technique for the remote measurement of the tropospheric CO2, O2, and CH4 concentrations from space. Our goal is to develop a space instrument and mission approach for active CO2 measurements. Our technique uses several on and off-line wavelengths tuned to the CO2 and O2 absorption lines. This exploits the atmospheric pressure broadening of the gas lines to weigh the measurement sensitivity to the atmospheric column below 5 km and maximizes sensitivity to CO2 changes in the boundary layer where variations caused by surface sources and sinks are largest. Simultaneous measurements of O2 column use a selected region in the Oxygen A-band. Laser altimetry and atmospheric backscatter can also be measured simultaneously, which permits determining the surface height and measurements made to thick cloud tops and through aerosol layers.

We use the same technique but with a different transmitter at 1.65 um to measure methane concentrations. Methane is also a very important trace gas on earth, and a stronger greenhouse gas than CO2 on a per molecule basis. Accurate, global observations are needed in order to better understand climate change and reduce the uncertainty in the carbon budget. Although carbon dioxide is currently the primary greenhouse gas of interest, methane can have a much larger impact on climate change. Methane levels have remained relatively constant over the last decade but recent observations in the Arctic have indicated that levels may be on the rise due to permafrost thawing. NASA’s Decadal Survey underscored the importance of Methane as a greenhouse gas and called for a mission to measure CO2, CO and CH4. Methane has absorptions in the mid-infrared (3.3 um) and the near infrared (1.65 um). The 3.3 um spectral region is ideal for planetary (Mars) Methane monitoring, but unfortunately is not suitable for earth monitoring since the Methane absorption lines are severely interfered with by water. The near infra-red overtones of Methane at 1.65 um are relatively free of interference from other atmospheric species and are suitable for Earth observations. The methane instrument uses Optical Parametric Generation (OPG) along with sensitive detectors to achieve the necessary sensitivity. Our instrument generates and detects tunable laser signals in the 3.3 or 1.65 um spectral regions with different detectors in order to measure methane on Earth or Mars. For Mars, the main interest in methane is its importance as a biogenic marker.

SPIE Journal Paper | 1 September 2017 Open Access

Open Access

Methane optical density measurements with an integrated path differential absorption lidar from an airborne platform

Haris Riris, Kenji Numata, Stewart Wu, Brayler Gonzalez, Michael Rodriguez, Stan Scott, Stephan Kawa, Jianping Mao

JARS, Vol. 11, Issue 03, 034001, (September 2017) https://doi.org/10.1117/12.10.1117/1.JRS.11.034001

KEYWORDS: LIDAR, Optical parametric oscillators, Absorption, Transmitters, Methane, Sensors, Absorbance, Optical testing, Clouds, Receivers

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Proceedings Article | 30 August 2017 Paper

Paper

New semiconductor laser technology for gas sensing applications in the 1650nm range

Gordon Morrison, Jes Sherman, Steven Estrella, Renan Moreira, Paul Leisher, Milan Mashanovitch, Mark Stephen, Kenji Numata, Stewart Wu, Haris Riris

Proceedings Volume 10406, 1040605 (2017) https://doi.org/10.1117/12.2275215

KEYWORDS: LIDAR, Semiconductor lasers, Laser applications, Tunable lasers, Methane, Carbon dioxide, Mid-IR, Pollution

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Proceedings Article | 5 May 2017 Presentation + Paper

Presentation + Paper

Methane measurements from space: technical challenges and solutions

Haris Riris, Kenji Numata, Stewart Wu, Brayler Gonzalez, Michael Rodriguez, Stephan Kawa, Jianping Mao

Proceedings Volume 10191, 1019104 (2017) https://doi.org/10.1117/12.2262516

KEYWORDS: Methane, Absorption, LIDAR, Carbon, Climate change, Laser applications, Spectroscopy, Optical parametric oscillators, Transmitters, Receivers, Sensors, Fiber lasers, Beam splitters, Airborne laser technology

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Proceedings Article | 1 September 2015 Paper

Paper

Fiber-based, trace-gas, laser transmitter technology development for space

Mark Stephen, Anthony Yu, Jeffrey Chen, Jeffrey Nicholson, Doruk Engin, Brian Mathason, Stewart Wu, Graham Allan, William Hasselbrack, Brayler Gonzales, Lawrence Han, Kenji Numata, Mark Storm, James Abshire

Proceedings Volume 9612, 96120B (2015) https://doi.org/10.1117/12.2191395

KEYWORDS: Transmitters, Optical amplifiers, Fiber amplifiers, Carbon dioxide lasers, Laser applications, Carbon dioxide, Laser development, Fiber lasers, Aerospace engineering, LIDAR

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Proceedings Article | 1 September 2015 Paper

Paper

Optical parametric technology for methane measurements

Martha Dawsey, Kenji Numata, Stewart Wu, Haris Riris

Proceedings Volume 9612, 961205 (2015) https://doi.org/10.1117/12.2191615

KEYWORDS: Methane, LIDAR, Optical parametric oscillators, Absorption, Sensors, Receivers, Pulsed laser operation, Gases, Carbon, Transmitters

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Proceedings Article | 20 February 2015 Paper

Paper

Space qualification of the optical filter assemblies for the ICESat-2/ATLAS instrument

E. Troupaki, Z. Denny, S. Wu, H. Bradshaw, K. Smith, J. Hults, L. Ramos-Izquierdo, W. Cook

Proceedings Volume 9346, 93460H (2015) https://doi.org/10.1117/12.2077839

KEYWORDS: Fabry–Perot interferometers, Optical filters, Optical fabrication, Transmittance, Temperature metrology, Beam splitters, Sensors, Diffractive optical elements, Optical testing, Receivers

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Proceedings Article | 24 October 2012 Paper

Paper

Airborne measurement of atmospheric methane concentration using pulsed lidar

Anand Ramanathan, Kenji Numata, Stewart Wu, Steven Li, Martha Dawsey, Jianping Mao, Stephan Kawa, Haris Riris

Proceedings Volume 8511, 85110E (2012) https://doi.org/10.1117/12.929990

KEYWORDS: Methane, LIDAR, Absorption, Carbon dioxide, Earth's atmosphere, Electronic support measures, Infrared radiation, Atmospheric optics, Climate change, Carbon

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SPIE Journal Paper | 12 September 2012

Ground demonstration of trace gas lidar based on optical parametric amplifier

Kenji Numata, Haris Riris, Steven Li, Stewart Wu, Stephan Kawa, Michael Krainak, James Abshire

JARS, Vol. 6, Issue 01, 063561, (September 2012) https://doi.org/10.1117/12.10.1117/1.JRS.6.063561

KEYWORDS: LIDAR, Carbon monoxide, Optical amplifiers, Crystals, Near infrared, Gases, Fiber amplifiers, Gas lasers, Absorption, Signal detection

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Proceedings Article | 14 May 2012 Paper

Paper

Ground and airborne methane measurements with an optical parametric amplifier

Kenji Numata, Haris Riris, Steve Li, Stewart Wu, Stephan Kawa, Martha Dawsey, Anand Ramanathan, Jianping Mao, Michael Krainak, James Abshire

Proceedings Volume 8379, 83790H (2012) https://doi.org/10.1117/12.918100

KEYWORDS: Methane, LIDAR, Optical amplifiers, Nonlinear crystals, Signal detection, Earth's atmosphere, Sensors, Optical testing, Atmospheric optics, Absorption

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Proceedings Article | 30 September 2011 Paper

Paper

Spaceflight laser development for future remote sensing applications

Anthony Yu, Michael Krainak, Mark Stephen, James Abshire, David Harding, Haris Riris, Steven Li, Jeffrey Chen, Graham Allan, Kenji Numata, Stewart Wu, Jordan Camp

Proceedings Volume 8182, 818204 (2011) https://doi.org/10.1117/12.898547

KEYWORDS: LIDAR, Carbon dioxide, Carbon dioxide lasers, Pulsed laser operation, Transmitters, Laser development, Laser applications, Laser systems engineering, Space telescopes, Absorption

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Proceedings Article | 17 September 2011 Paper

Paper

Spaceborne laser development for future remote sensing applications

Mark Stephen, Anthony Yu, Michael Krainak, James Abshire, David Harding, Haris Riris, Steven Li, Jeffrey Chen, Kenji Numata, Stewart Wu, Jordan Camp

Proceedings Volume 8154, 815406 (2011) https://doi.org/10.1117/12.896693

KEYWORDS: Carbon dioxide, Pulsed laser operation, LIDAR, Carbon dioxide lasers, Transmitters, Laser systems engineering, Remote sensing, Laser applications, Space telescopes, Sensors

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Proceedings Article | 14 September 2011 Paper

Paper

Development of optical parametric amplifier for lidar measurements of trace gases on Earth and Mars

Kenji Numata, Haris Riris, Steve Li, Stewart Wu, Stephan Kawa, Michael Krainak, James Abshire

Proceedings Volume 8159, 81590E (2011) https://doi.org/10.1117/12.896307

KEYWORDS: LIDAR, Gases, Carbon dioxide, Optical amplifiers, Near infrared, Mars, Crystals, Earth's atmosphere, Absorption, Sensors

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Proceedings Article | 20 August 2011 Paper

Paper

Lidar technology for measuring trace gases on Mars and Earth

Haris Riris, Kenji Numata, Steve Li, Stewart Wu, James Abshire, Graham Allan, William Hasselbrack, Mike Rodriguez, Jeffrey Chen, Stephen Kawa, Jianping Mao, Clark Weaver, Anthony Yu, Xiaoli Sun

Proceedings Volume 8192, 819203 (2011) https://doi.org/10.1117/12.900870

KEYWORDS: Methane, Gases, Mars, LIDAR, Absorption, Carbon dioxide, Earth's atmosphere, Spectrometers, Climate change, Signal detection

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Proceedings Article | 28 August 2010 Paper

Paper

Spaceborne laser transmitters for remote sensing applications

Anthony Yu, Steven Li, Mark Stephen, Anthony Martino, Jeffrey Chen, Michael Krainak, Stewart Wu, Haris Riris, James Abshire, David Harding, Graham Allan, Kenji Numata

Proceedings Volume 7808, 780817 (2010) https://doi.org/10.1117/12.861536

KEYWORDS: Transmitters, Pulsed laser operation, Remote sensing, Laser resonators, LIDAR, Carbon dioxide lasers, Carbon dioxide, Laser applications, Laser systems engineering, Semiconductor lasers

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Proceedings Article | 18 February 2010 Paper

Paper

Seeded nanosecond optical parametric generator for trace gas measurements

Kenji Numata, Steve Li, Haris Riris, Stewart Wu, Antonios Seas, Anthony Yu, Michael Krainak, James Abshire

Proceedings Volume 7582, 75820K (2010) https://doi.org/10.1117/12.843747

KEYWORDS: Carbon dioxide, Crystals, Absorption, Gases, Near infrared, Sensors, Nd:YAG lasers, LIDAR, Earth's atmosphere, Laser crystals

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Proceedings Article | 5 February 2008 Paper

Paper

Single-photon avalanche photodiode with improved structure using an innovative current bias scheme

Yonglin Gu, Fow-Sen Choa, Yan Feng, Xiucheng Wu, Stewart Wu, Bing Guan, Peter Su, Michael Krainak

Proceedings Volume 6890, 68900N (2008) https://doi.org/10.1117/12.764540

KEYWORDS: Avalanche photodetectors, Doping, Single photon, Indium gallium arsenide, Photon counting, Avalanche photodiodes, Absorption, Sensors, Photodetectors, Solids

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Proceedings Article | 7 May 2007 Paper

Paper

InGaAsP avalanche photodetectors for non-gated 1.06 um photon-counting receivers

Mark Itzler, Xudong Jiang, Rafael Ben-Michael, Krystyna Slomkowski, Michael Krainak, Stewart Wu, Xiaoli Sun

Proceedings Volume 6572, 65720G (2007) https://doi.org/10.1117/12.719471

KEYWORDS: Single photon, Absorption, Avalanche photodetectors, Sensors, Photon counting, Avalanche photodiodes, Receivers, Silicon, Ionization, Gallium

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Showing 5 of 22 publications

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