NASA is working with US industry and academia to develop Photonic Integrated Circuits (PICs) for: (1) Sensors (2) Analog RF applications (3) Computing and free space communications. The PICs provide reduced size, weight, and power that is critical for space-based systems. We describe recent breakthrough 3D monolithic integration of photonic structures, particularly high-speed graphene-silicon devices on CMOS electronics to create CMOS-compatible highbandwidth transceivers for ultra-low power Terabit-scale optical communications. An integrated graphene electro-optic modulator has been demonstrated with a bandwidth of 30 GHz. Graphene microring modulators are especially attractive for dense wavelength division multiplexed (DWDM) systems. For space-based optical communication and ranging we have demonstrated generating a variable number of channels from a single laser using breadboard components, using a single-sideband carrier-suppressed (SSBCS) modulator driven by an externally-supplied RF tone (arbitrary RF frequency), a tunable optical bandpass filter, and an optical amplifier which are placed in a loop. We developed a Return--to-Zero (RZ) Differential Phase Shift Keying (DPSK) laser transmitter PIC using an InP technology platform that includes a tunable laser, a Semiconductor Optical Amplifier (SOA), high-speed Mach-Zehnder Modulator (MZM), and an electroabsorption (EAM) modulator. A Silicon Nitride (SiN) platform integrated photonic circuit suitable for a spectrally pure chip-scale tunable opto-electronic RF oscillator (OEO) that can operate as a flywheel in high precision optical clock modules, as well as radio astronomy, spectroscopy, and local oscillator in radar and communications systems is needed. We have demonstrated a low noise optical frequency combs generation from a small OEO prototypes containing very low loss (~1 dB) waveguide couplers of various shapes and sizes integrated with an ultrahigh-Q MgF2 resonators. An innovative miniaturized lab-on-a-chip device is being developed to directly monitor astronaut health during missions using ~3 drops of body fluid sample like blood, urine, and potentially other body fluids like saliva, sweat or tears. The first-generation system comprises a miniaturized biosensor based on PICs (including Vertical Cavity Surface Emitting Laser – VCSEL, photodetector and optical filters and biochemical assay that generates a fluorescent optical signal change in response to the target analyte.
We report on the cause and corrective actions of three amplifier crystal fractures in the space-qualified laser systems used in NASA Goddard Space Flight Center’s (GSFC) Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2). The ICESat-2 lasers each contain three end-pumped Nd:YVOO4 amplifier stages. The crystals are clamped between two gold plated copper heat spreaders with an indium foil thermal interface material, and the crystal fractures occurred after multiple years of storage and over a year of operational run-time. The primary contributors are high compressive loading of the NdYVO<sub>4</sub> crystals at the beginning of life, a time dependent crystal stress caused by an intermetallic reaction of the gold plating and indium, and slow crack growth resulting in a reduction in crystal strength over time. An updated crystal mounting scheme was designed, analyzed, fabricated and tested. Thee fracture slab failure analysis, finite-element modeling and corrective actions are presented.
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 frequency doubler was in a clean room at a normal air pressure. The goal of the experiment was to measure degradation modes at 1064 and 532 nm separately. The external frequency doubler consisted of a Lithium triborate, LiB<sub>3</sub>O<sub>5</sub>, non-critically phase-matched crystal. After some 1064 nm light was diverted for diagnostics, 13.7W of fundamental power was available to pump the doubling crystal. Between 8.5W and 10W of 532nm power was generated, depending on the level of stress and degradation. The test consisted of two stages, the first at 0.3 J/cm<sup>2</sup> for almost 1 year, corresponding to expected operational conditions, and the second at 0.93 J/cm<sup>2</sup> for the remainder of the experiment, corresponding to accelerated optical stress testing. We observed no degradation at the first stress-level and linear degradation at the second stress-level. The linear degradation was linked to doubler crystal output surface changes from laser-assisted contamination. We estimate the expected lifetime for the flight laser at 532 nm using fluence as the stress parameter. This work was done for NASA’s Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) LIDAR at Goddard Space Flight Center in Greenbelt, MD with the goal of 1 trillion shots lifetime.
The Advanced Topographic Laser Altimeter System (ATLAS) will be the only instrument on the Ice, Cloud, and Land
Elevation Satellite -2 (ICESat-2). ICESat-2 is the 2nd-generation of the orbiting laser altimeter ICESat, which will
continue polar ice topography measurements with improved precision laser-ranging techniques. In contrast to the
original ICESat design, ICESat-2 will use a micro-pulse, multi-beam approach that provides dense cross-track sampling
to help scientists determine a surface's slope with each pass of the satellite. The ATLAS laser will emit visible, green
laser pulses at a wavelength of 532 nm and a rate of 10 kHz and will be split into 6 beams. A set of six identical,
thermally tuned optical filter assemblies (OFA) will be used to remove background solar radiation from the collected
signal while transmitting the laser light to the detectors. A seventh assembly will be used to monitor the laser center
wavelength during the mission. In this paper, we present the design and optical performance measurements of the
ATLAS OFA in air and in vacuum prior to their integration on the ATLAS instrument.
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:YAG for future flight missions. The significant reduction in thermal loading on the gain medium by the use of 885 nm pump lasers will improve system efficiency.
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 years. NASA is planning a follow-on mission ICESat-2 to be launched tentatively in 2015. In this paper we will
discuss the development effort of the laser transmitters for the ICESat-2 mission.
Over the last two decades NASA Goddard Space Flight Center (GSFC) has developed several laser systems for space
application. The aging behavior of a laser system varies depending on the complexity of the system and the technologies
used. One limitation of reliability models trying to predict system performance has been the lack of test data. Extended
testing is an effective way to determine the reliability, and long term stability of laser systems. In this paper the results
from extended testing of two laser system are presented. One system has been operating for over two and a half billion
shots in air while the second system has accumulated half a billion shots while operating in a vacuum environment.
NASA's space-borne laser missions have been dominated by low repetition rate (<100Hz) Q-switched laser systems,
which use Nd:YAG laser crystals, and are pumped by quasi-continuous wave (QCW) 808 nm laser diode arrays (LDAs).
The diode group at NASA Goddard Space Flight Center (GSFC) has been responsible for the screening and qualification
of LDAs for several missions. The main goal has been to identify LDAs that can withstand the harsh space environment,
and minimize risks associated with LDA degradation or failure. This paper presents a summary of recent research
activities, and describes the results from extended testing of multiple LDAs in air and vacuum environments.
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
crossed-Porro resonator. All components used in the laser have space flight heritage. The
flight laser bench houses two oscillators (a primary and a cold spare) that are designed to
operate sequentially during the mission. If the primary laser can no longer provide
adequate scientific data products, the secondary laser will be turned on. The baseline
mission calls for LOLA (and LRO) to spend about one year studying the Moon. Since
LOLA operates at 28 Hz, the laser system needs to produce approximately one billion
pulses during the primary one year mission. To validate that the LOLA laser design is
capable of meeting this requirement, the LOLA Engineering Model (EM) laser has been
subjected to extended operation testing in vacuum. In this paper we will summarize the
longevity validation test effort of the LOLA EM laser.
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 significant data on these devices and have developed testing strategies to achieve mission success in a cost-effective manner. In this paper, we present our approach for qualifying the LDAs for the Lunar Orbiter Laser Altimeter (LOLA) instrument scheduled to launch aboard the Lunar Reconnaissance Orbiter (LRO) mission. We describe our strategy to mitigate risk due to LDA failure given cost and schedule constraints. The results from extended testing of multiple LDAs in air and in vacuum are also presented.
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's and planetary sciences. In this paper we will review the past and present of space-qualified laser programs at
GSFC and offer insights into future laser based science instrumentations.
NASA is conducting a series of component-level tests, to better understand the reliability and the effects of a spacebased
environment on the operation of diode-pumped, solid-state lasers by simulating the unique and harsh environment
of launch, vacuum and radiation exposure of a typical mission.
We report on our continuing work on high-power, laser-diode arrays (LDA) which are used as an energy source for
several proposed and currently flying diode-pumped solid-state lasers missions (ICESAT, MESSENGER and LRO.)
The laser-diode arrays are a critical component which can determine the reliability of the whole laser system. NASA
needs reliability and performance data for these components to minimize the risks for space-based laser programs.
We are concentrating on laser diode arrays emitting at 808 nm and operating quasi-cw with peak powers of ~100 watts
per bar at 100 amps. The laser diode arrays are operated with a duty cycle from 0.6% to 2% and current pulses from 50
to 100 amps peak. We studied the effects of power cycling and temperature cycling on the performance of the diode
arrays. We also conducted vacuum test as well as vibration and radiation tests. The laser diode arrays have
accumulated more then 5.0 billion pulses during some of these tests and continue to operate within specifications.
NASA's requirements for high reliability, high performance satellite laser instruments have driven the investigation of many critical components; specifically, 808 nm laser diode array (LDA) pump devices. Performance and comprehensive characterization data of Quasi-CW, High-power, laser diode arrays is presented.