Mark Stephen

• National Aeronautics and Space Administration

An ultra-compact, narrow-bandwidth, and high-density photonic integrated channelizer has been developed on a silicon nitride platform and demonstrated for parallel processing of wide band hyperspectral microwave spectra. This device is based on an updated generation of arrayed waveguide gratings (AWG) named serial-AWG (SAWG). The design consists of...

Performance of space-based optics could be greatly enhanced by using deployable origami-based arrays, which can offer a large aperture size relative to their stowed volume when compared to traditional technology, thus improving imaging quality. In this work, we select, develop, and adapt the origami flasher pattern to serve as the foundation for a...

Deployable origami-based arrays can offer many benefits for a wide variety of engineering applications. However, alignment in the deployed state is a primary challenge of these arrays; in optical systems, local (single panel) and global (entire array) misalignment can drastically reduce performance. The objective of this work is to compare the rela...

We present a comprehensive sensitivity analysis and geophysical retrieval product demonstration to assess the enhanced information content in atmospheric temperature and water vapor, harnessed in hyperspectral microwave measurements. A particular focus of this study is devoted to quantifying and comparing the impact on retrieval performance resulti...

Metalenses promise potential for a paradigm shift of conventional optical devices. However, the aperture sizes of metalenses are usually bound within hundreds of micrometers by the commonly used fabrication methods, limiting their usage on practical optical devices like telescopes. Here, for the first time, we demonstrate a high-efficiency, single-...

Design parameters of the origami flasher pattern can be modified to meet a variety of design objectives for deployable array applications. The focus of this paper is to improve understanding of design parameters, objectives, and trade offs of origami flasher pattern configurations. Emphasis is placed on finite-thickness flasher models that would en...

Metalenses, artificially engineered subwavelength nanostructures to focus light within ultrathin thickness, promise potential for a paradigm shift of conventional optical devices. However, the aperture sizes of metalenses are usually bound within hundreds of micrometers by the commonly-used scanning-based fabrication methods, limiting their usage o...

A monolithic indium phosphide photonic integrated circuit was designed and fabricated for remote active carbon dioxide sensing. Successful measurement of carbon dioxide in a laboratory setting under pulsed sampling was demonstrated.

A widely tunable 1030 nm gallium arsenide laser with an integrated semiconductor optical amplifier was demonstrated. Continuous tuning across 22.2 nm and up to 70 mW output power was achieved.

Two generations of indium phosphide photonic integrated circuits were fabricated, characterized, and their performance compared. Successful sampling of carbon dioxide was performed in a laboratory setting under continuous wave sampling.

At NASA Goddard Space Flight Center (GSFC), we have been developing spaceborne lidar instruments for space sciences. We have successfully flown several missions in the past based on mature diode pumped solid-state laser transmitters. In recent years we have been developing advanced laser technologies for applications such as laser spectroscopy, las...

An indium phosphide photonic integrated circuit (PIC) was demonstrated for integrated path differential absorption lidar of atmospheric carbon dioxide (CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). The PIC consists of two widely tunable sampled grating distributed Bragg reflector (SGDBR...

An active-passive integration technique for operation near a wavelength of 1030 nm has been developed on a gallium arsenide (GaAs) photonic integrated circuit platform. The technique leverages quantum wells (QWs) that are slightly offset vertically from the center of the waveguide, and selectively removed prior to upper cladding regrowth to form ac...

A dual laser indium phosphide photonic integrated circuit for remote sensing lidar was realized. A twentyfold improvement in the long-term frequency stability of the master laser was demonstrated using an on-chip phase modulator.

A novel indium phosphide Mach-Zehnder interferometer with directional couplers was realized to compensate residual amplitude modulation in integrated phase modulators. The change in transmission for π phase shift was reduced from 3.85 dB to 1.98 dB.

An active-passive integration platform on GaAs is demonstrated with Fabry Perot lasers exhibiting up to 240 mW total output power, 98.8% injection efficiency, and 3.44 cm ⁻¹ active loss for operation near 1030 nm.

Subsystem operation of a photonic integrated circuit for low size, weight, and power remote gas sensing was demonstrated. Precision lidar system specifications for laser tuning, photodiode bandwidth and pulse extinction ratio were satisfied. A twentyfold improvement in long-term laser frequency stability was achieved.

A photonic integrated channelizer is designed for hyperspectral and ultra-high band coverage remote sensing applications. The tunable delay lines maximize the transmission performance and the device demonstrates 4.5 GHz of optical bandwidth and channel separation. OSCIS codes : (250.5300) Photonic Integrated circuits; (280.4991) Passive remote sens...

At NASA Goddard Space Flight Center, we have been developing spaceborne lidar instruments for space sciences. We have successfully flown several missions in the past based on mature diode pumped solid-state laser transmitters. In recent years, we have been developing advanced laser technologies for applications such as laser spectroscopy, laser com...

A dual-laser indium phosphide photonic integrated circuit for precision spectroscopy lidar was designed and fabricated. A stabilization experiment demonstrated a twentyfold improvement in the long-term frequency stability of the master laser.

NASA-Goddard is developing a high-fidelity space-based remote sensor for atmospheric CO2. We report on a the instrument architecture and performance and the technology developments for a low earth orbiting instrument.

NASA Goddard Space Flight Center has been developing an integrated path differential absorption (IPDA) lidar instrument concept to measure the column concentrations of atmospheric carbon dioxide (CO2) from space. We will discuss the development effort of a space-qualified, single frequency, fiber-based master oscillator power amplifier with >450 µJ...

We present modeling and performance of a solid, fused silica, 3-mirror Fabry–Perot-type etalon. 3-mirror etalons have been known for decades to have superior theoretical performance but for the first time we demonstrate an etalon with sufficient quality to realize the benefits of the more complex design. 3-mirror etalons have better passband shape...

We demonstrate the first polarization-maintaining, very-large-mode-area, Er-doped fiber amplifier with ~1100 μm² effective area. The amplifier is core pumped by a Raman fiber laser and is used to generate single-frequency, one-microsecond, pulses with pulse energy of 541 μJ, peak power of 700 W, M² of 1.1, and polarization extinction > 20 dB. The a...

We present the results of a three-year operational-aging test of a specially designed prototype flight laser operating at 1064 nm, 10 kHz, 1ns, 15W average power and externally frequency-doubled. Fibertek designed and built the q-switched, 1064nm laser and this laser was in a sealed container of dry air pressurized to 1.3 atm. The external frequenc...

A cladding-pumped, LMA ErYb fiber-based, amplifier is presented for use in a LIDAR transmitter for remote sensing of atmospheric CO2 from space. The amplifier is optimized for high peak power, high efficiency, and narrow linewidth operation at 1572.3nm. Using highly reliable COTS components, the amplifier achieves 0.5kW peak power (440uJ pulse ener...

Atmospheric methane is the second most important greenhouse gas with 25 times the radiative forcing of carbon dioxide. We will present results from an airborne campaign using a lidar at 1.65µm using optical parametric generation.

We describe a Fabry-Perot etalon spectrometer with a novel light recirculation scheme to generate simultaneous parallel wavelength channels with no moving parts. We also present results from a 3-mirror solid Fabry-Perot.

We have advanced the science of space-based laser measurements using the spectral purity and frequency tuning of a fiber-amplified lasers performing active remote sensing of atmospheric CO2 column abundance and dry mixing ratio.

We describe a Fabry-Perot etalon spectrometer with a novel light recirculation scheme to generate simultaneous parallel wavelength channels with no moving parts. This design uses very simple optics to recirculate light reflected from near normal incidence from the etalon at successively higher angles of incidence. The spectrometer has the full reso...

NASA’s Goddard Space Flight Center (GSFC) is working on maturing the technology readiness of a laser transmitter designed for use in atmospheric CO2 remote-sensing. GSFC has been developing an airplane-based CO2 lidar instrument over several years to demonstrate the efficacy of the instrumentation and measurement technique and to link the science m...

A new solution for building high power, solid state lasers for space flight is to fabricate the whole laser resonator in a single (monolithic) structure or alternatively to build a contiguous diffusion bonded or welded structure. Monolithic lasers provide numerous advantages for space flight solid-state lasers by minimizing misalignment concerns. T...

In this paper we will review our progress on maturing the technology and improving the technical readiness of a fiber-based laser transmitter at 1.57 μm for use in atmospheric carbon dioxide (CO2) satellite remote-sensing.

In this paper, we present laser damage threshold testing performed on Un-Coated Fused Silica (SiO2) substrates after multiple laser pulse irradiation. We will outline our methods of testing and observation of laser damage. Using carefully prepared 1” optical flats with 0.25” thickness, we observe competition between laser damage on the surface and...

The effects of long-term exposure to high intensity 532 nm radiation on various dielectric-coated optics are studied. To investigate potential photodarkening effects on optical surfaces, an accelerated life test platform was constructed where optics were exposed to 532 nm radiation from a short-pulse, high repetition rate fiber amplifier at total d...

A laser diode module (LDM) space certification and qualification program was developed for NASA's Ice, Cloud and Land Elevation Satellite-2, ICESat-2 mission. The ICESat-2 laser transmitter is a high performance diode-pumped solid state laser that requires high reliability, high efficiency and high brightness fiber coupled LDMs, capable of supporti...

The design of space-flight hardware is typically required to be at a Technology Readiness Level (TRL) of 6 before the build of the actual flight hardware can begin. At the early design phase the "relevant environment" for TRL-6 is frequently not well defined. For the ICESat-2 laser relevant environment was defined as the qualification levels in GEV...

We report on an airborne demonstration of atmospheric oxygen optical depth measurements with an IPDA lidar using a fiber-based laser system and a photon counting detector. Accurate knowledge of atmospheric temperature and pressure is required for NASA’s Active Sensing of Emissions over Nights, Days, and Seasons (ASCENDS) space mission, and climate...

Fibertek has developed an environmentally hardened Technology Readiness Level-6 laser transmitter system for the NASA Ice, Cloud and land Elevation Satellite-2 (ICESat-2). The laser transmitter generates over 9 W of 532 nm output with a pulse repetition rate of 10kHz and a FWHM pulse width of < 1.5 ns with an expected lifetime of > 1 trillion shots...

We report an Er-doped, actively Q-switched, fiber laser, generating transform-limited pulses based on single-frequency fiber laser seeded ring cavity. The output pulse width can be tuned from hundreds of nanoseconds to several microseconds by changing the repetition rate or the open time of the electrical pulse trigger. This injection seeded, Q-swi...

Lasers designed for space-based applications must meet stringent performance requirements, but be robust enough to survive severe vibrational launch levels, and operate reliably on orbit for years with no maintenance. The transmitters that are currently in use in the CALIPSO mission and that are being designed for the ICESat-2 mission are good exam...

NASA is currently developing several Earth science laser missions that were recommended by the US National Research Council (NRC) Earth Science Decadal Report. The Ice Cloud and Land Elevation Satellite-2 (ICESat-2) will carry the Advanced Topographic Laser Altimeter System (ATLAS) is scheduled for launch in 2016. The Active Sensing of CO2 Emission...

We present current and near-term uses of high-power fiber lasers and amplifiers for NASA science and spacecraft applications. Fiber lasers and amplifiers offer numerous advantages for the deployment of instruments on exploration and science remote sensing satellites. Ground-based and airborne systems provide an evolutionary path to space and a mean...

We report on the atmospheric pressure measurements using a fiber-based laser system using the oxygen A-band at 765 nm. Remote measurements of atmospheric temperature and pressure are required for a number of scientific applications including greenhouse gas monitoring, weather prediction, and climate modeling.

At NASA's Goddard Space Flight Center we are developing next generation laser transmitters for future spaceflight, remote instruments including a micropulse altimeter for ice-sheet and sea ice monitoring, laser spectroscopic measurements of atmospheric CO2 and an imaging lidar for high resolution mapping of the Earth's surface. These laser transmit...

At NASA's Goddard Space Flight Center, we are developing the next generation laser transmitters for future remote sensing applications including a micropulse altimeter for ice-sheet monitoring, laser spectroscopic measurements and high resolution mapping of the Earth's surface as well as potential missions to other planets for trace gas measurement...

We report a monolithic specialized high stimulated Brillouin scattering (SBS) threshold fiber laser/amplifier in the C and L band based on highly co-doped phosphate glass fibers. This represents an important new development for coherent LIDAR and remote sensing applications. By using single mode polarization-maintaining large core highly Er/Yb codo...

We demonstrated up to 2 W average power, CW-pumped, passively- Q-switched, 1.5 ns monolithic microchip laser with single-longitudinal mode-operation. We discuss various design approaches to bring the average power to 10W and beyond.

We demonstrated up to 2 W average power, CW-pumped, passively-Q-switched, 1.5 ns monolithic MCL with single-longitudinal mode-operation. We discuss laser design issues to bring the average power to 5-10W and beyond.

We report on airborne atmospheric pressure measurements using new fiber-based laser technology and the oxygen A-band at 765 nm. Remote measurements of atmospheric temperature and pressure are required for a number of NASA Earth science missions and specifically for the Active Sensing of CO2 Emissions Over Nights, Days, and Seasons (ASCENDS) mission...

NASA Goddard Space Flight Center (GSFC) has been engaging in Earth and planetary science remote sensing instruments development for many years. The latest instrument was launched in 2008 to the moon providing the most detailed topographic map of the lunar surface to-date. NASA GSFC is preparing for several future missions, which for the first time...

We demonstrate a high-stimulated-Brillouin-scattering-threshold monolithic pulsed fiber laser in a master oscillator power amplifier configuration that can operate over the C band. In the power amplifier stage, we used a newly developed single-mode, polarization maintaining, and highly Er/Yb codoped phosphate fiber with a core diameter of 25 μm . A...

We have achieved a peak power of 1.2 kW for 105 ns pulses at 1530nm with transform-limited linewidth by using a single-mode 25μm-core phosphate fiber in the power amplifier stage of a monolithic MOPA system.

We have achieved a peak power of 1.2 kW for 105 ns pulses with transform-limited linewidth by using a SM 25 mu m core phosphate fiber in the power amplifier stage of a monolithic MOPA system. (C)2010 Optical Society of America

The objective of this effort is to develop more reliable, higher efficiency diode pumped Nd:YAG laser systems for space applications by leveraging technology investments from the DoD and other commercial industries. Our goal is to design, build, test and demonstrate the effectiveness of combining 885 nm laser pump diodes and the use of ceramic Nd:Y...

The first NASA Ice, Cloud and land Elevation Satellite (ICESat) was launched in January 2003 and placed into a nearpolar orbit whose primary mission was the global monitoring of the Earth's ice sheet mass balance. ICESat has accumulated over 1.8 B shots in space and provided a valuable dataset in the study of ice sheet dynamics over the past few ye...

A compact, passively q-switched, single mode laser has been developed for space based lidar applications. The Nd:YAG laser produces 50mJ pulse-energy at 100 Hz repetition rate in a near diffraction limited beam with more than 99.99% of the pulses in a single longitudinal mode. This laser was initially developed as a candidate for the ICESat-2 missi...

We report a monolithic high SBS-threshold pulsed fiber laser in MOPA for longer nanosecond pulses with transformlimited linewidth. By using a single mode polarization-maintaining large core 25 mum highly Er/Yb co-doped phosphate fiber in the power amplifier stage, we have achieved the highest peak power of 1.2 kW at 1530 nm for 105 ns pulses with t...

We report on the atmospheric pressure measurements using a fiber-based laser system using the oxygen A-band. Remote measurements of atmospheric temperature and pressure are required for a number of scientific applications including trace gas detection, weather prediction, and climate modeling. Recently there has been intense interest to provide acc...

In the recent past, NASA's space-borne laser missions have been dominated by low repetition rate (<100Hz), Q-switched Nd:YAG lasers pumped by quasi-continuous wave (QCW) 808 nm laser diode arrays (LDA). QCW LDA reliability data is limited and their mechanisms of failure is poorly understood. Our group has been working in gathering statistically sig...

NASA Goddard Space Flight Center (GSFC) has been engaging in Earth and planetary science instruments development for many years. With stunning topographic details of the Mars surface to Earth's surface maps and ice sheets dynamics of recent years, NASA GSFC has provided vast amount of scientific data products that gave detailed insights into Earth'...

The Lunar Orbiter Laser Altimeter (LOLA) is one of seven instruments aboard the Lunar Reconnaissance Orbiter (LRO) spacecraft with the objectives to determine the global topography of the lunar surface at high resolution, measure landing site slopes and search for polar ices in shadowed regions. The LOLA laser transmitter is a passively Q-switched...

We will present a description of a retrieval algorithm, which extracts the column-average CO2 volume-mixing ratio from atmospheric observations from our Laser Sounder. We will also present results from a direct comparison between a ground-based version of the laser sounder and the Boulder Atmospheric Observatory (BAO) Tower. The laser sounder was o...

Accurate measurements of tropospheric CO2 abundances with global-coverage and monthly temporal resolution are needed to quantify processes that regulate CO2 exchange with the land and oceans. To meet this need, the 2007 Decadal Survey for Earth Science by the US National Research Council recommended a laser-based CO2 measuring mission called ASCEND...

We report on the design and construction of an Oxygen spectroscopy laser sounding instrument designed to measure atmospheric pressure. The pressure sensing instrument (although useful for many applications) was designed as a calibration channel for a carbon dioxide instrument to meet the science requirements of NASA's ASCENDS Mission. The instrumen...

We report on the progress of an Oxygen spectroscopy laser sounding instrument designed as a calibration channel for a carbon dioxide (CO 2) laser sounding instrument. We have developed a pulsed, frequency-doubled, fiber laser transmitter for use in an oxygen instrument. The instrument concept uses the pressure broadening of spectroscopic lines of t...

The diode-laser array working group (DAWG) is a national-level consumer/provider forum for discussion of engineering and manufacturing issues which influence the reliability and survivability of high-power broad-area laser diode devices in space, with an emphasis on laser diode arrays (LDAs) for optical pumping of solid-state laser media. The goals...

We report progress in assessing the feasibility of a new satellite-based laser-sounding instrument to measure CO2 concentrations in the lower troposphere from space.

We report progress in assessing the feasibility of a new satellite-based laser-sounding instrument to measure CO 2 and other trace gas abundances in the lower troposphere from space.

Mounting concern regarding global warming and the increasing carbon dioxide (CO2) concentration has stimulated interest in the feasibility of measuring CO2 mixing ratios from space. Precise satellite observations with adequate spatial and temporal resolution would substantially increase our knowledge of the atmospheric CO2distribution and allow imp...

We present results of pulsed, narrowband amplification at 1540.6nm using a polarization maintaining, large mode area gain fiber co-doped with erbium and ytterbium. At a repetition rate of 55 kHz, 2.9 W of average 1540.6nm power were generated with a pulse duration of 136 ns, corresponding to an SBS free peak power of 360 W. The amplified signal was...

We report on the development of a fiber-based laser transmitter designed for active remote sensing spectroscopy. The transmitter uses a master oscillator power amplifier (MOPA) configuration with a distributed feedback diode-laser master oscillator and an erbium-doped fiber amplifier. The output from the MOPA is frequency-doubled with a periodicall...

The development and vacuum life-testing of a diode pumped Cr:Nd:YAG laser for space applications is presented. Furthermore results from long life-testing of 808-nm laser diode arrays in air and vacuum are discussed.

We developed a frequency-doubled, DFB-seeded EDFA. 8 Watts of frequency-doubled power was achieved in a single-frequency, wavelength tunable, power scalable laser transmitter used for spectroscopic remote sensing of the oxygen A-band.

We present the design of the Lunar Orbiter Laser Altimeter laser transmitter which consists of two oscillators on a single bench, each capable of providing one billion shots.

Accurate measurements of tropospheric CO2 abundances with global-coverage and monthly temporal resolution are needed to quantify processes that regulate CO2 exchange with the land and oceans. The NASA Orbiting Carbon Observatory (OCO) is a space mission focused on atmospheric CO2 for measuring total column CO2 and O2 by measuring the spectral absor...

NASA’s mission requirements for spaceborne laser diode arrays lead to a set of tests peculiar to space flight. The goal of these tests is to determine if vibration, radiation, or vacuum will impair the operation or lifetime of nominally 100 W quasicontinuous wave 808 nm laser diode arrays. To simulate the stresses expected during a mission, terrest...