This PDF file contains the front matter associated with SPIE Proceedings Volume 8164, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

In this paper, progress made so far in the performance testing of waveguide laser components sent by NASA Langley Research Center on MISSE 6 mission will be discussed. The objective of the Materials International Space Station Experiment (MISSE) is to study the performance of novel materials when subjected to the synergistic effects of the harsh space environment for several months. MISSE missions provide an opportunity for developing space qualifiable materials. The results of post-testing of several optical materials that were recently returned back after more than one year of exposure on the International Space Station (ISS) will be presented. The items were part of the MISSE 6 mission that was transported to the ISS via STS 123 on March 11, 2008 and returned to the Earth via STS 128 that was launched on August 2009. The materials experienced no visible damage during lengthy exposure in space. In the case of laser diode, a comparison of elemental analysis with pre-flight conditions will be presented. Furthermore, the optical components sent on MISSE 7 mission via STS-129 and later retrieved by STS-134 will be briefly discussed.

The Jupiter Europa Orbiter (JEO) is NASA's element of the joint Europa Jupiter System Mission (EJSM). Based on current trajectories, the spacecraft will spend a significant amount of time in the Jovian radiation belts. Therefore, research endeavors are underway to study the radiation effects on the various parts and components needed to implement the instruments. Data from these studies will be used for component selection and system design to ensure reliable operation throughout the mission duration. The radiation environment en route to Jupiter is nothing new for NASA designed systems, however, the long durations orbiting Jupiter and Europa present new challenges for radiation exposure. High-energy trapped electrons and protons at Jupiter dominate the expected radiation environment. Therefore, most of the initial component level radiation testing is being conducted with proton exposure. In this paper we will present in-situ monitoring of the optical transmission of various laser optical components during proton irradiation. Radiation induced optical attenuation of some components is less than would be expected, based on the authors experiences, and is attributed to the interaction of the protons with the materials. The results are an encouraging first step in screening these optical materials for spaceflight in a high radiation environment.

InGaAs avalanche photodiodes (APDs) fabricated from epitaxial material by etching detector mesas and encapsulating the etched mesas under bisbenzocyclobutene (BCB) resin were irradiated by Co-60 gamma-rays to assess their sensitivity to a total ionizing dose of 200 krad(Si). A low-excess-noise APD design with a multi-stage avalanche gain region was tested. Ninety-six identical 20-μm-diameter APDs were characterized to assess the response of the design to ionizing radiation. The APDs were not under bias during irradiation. Damage to the APDs was characterized by measuring the change in room temperature dark current following irradiation, at a reverse bias for which the average avalanche gain is M=10. No significant increase of dark current was observed following gamma irradiation: the average increase was 5% and the standard deviation for the measurement was 10%.

The natures of most radiation-induced point defects in amorphous silicon dioxide (a-SiO₂) are well known on the basis of 55 years of electron spin resonance (ESR) and optical studies of pure and doped silica in bulk, thin-film, and fiberoptic forms. The self-trapped holes (STHs), discovered only in 1989, appear to be responsible for most radiationinduced red/near-IR optical absorption in silica-based photonics. However, accelerated testing of a-SiO₂-based devices slated for space applications must take into account the highly supralinear dependence of the initial STH creation rate on ionizing dose rate...and the possibility to permanently reduce the created numbers of STHs by high-dose pre-irradiation.

To evaluate the thrust produced by photon pressure emitted from a 100 W class continuous-wave semiconductor laser, a torsion-balance precise thrust stand is designed and tested. Photon emission propulsion using semiconductor light sources attract interests as a possible candidate for deep-space propellant-less propulsion and attitude control system. However, the thrust produced by photon emission as large as several ten nanonewtons requires precise thrust stand. A resonant method is adopted to enhance the sensitivity of the biflier torsional-spring thrust stand. The torsional spring constant and the resonant of the stand is 1.245 × 10^-3 Nm/rad and 0.118 Hz, respectively. The experimental results showed good agreement with the theoretical estimation. The thrust efficiency for photon propulsion was also defined. A maximum thrust of 499 nN was produced by the laser with 208 W input power (75 W of optical output) corresponding to a thrust efficiency of 36.7%. The minimum detectable thrust of the stand was estimated to be 2.62 nN under oscillation at a frequency close to resonance.

An ultra-low repetition rate high energy 200 ns Er:Yb co-doped fiber laser has been developed by using a master oscillator power amplifier configuration at an eye-safe 1.53 μm wavelength . A modulated pump scheme was used to suppress ASE accumulation between pulse intervals. Combined with pulse shaping technology to mitigate pulse narrowing effect and SBS effect, a maximum of 480 μJ pulse energy was obtained. In the stable, long-term running mode, pulse energy up to 204 μJ, were obtained with pulse durations of 200 ns at Hz level.

Tunable resonant absorption by plasmons in the two-dimensional electron gas (2DEG) of grating-gated HEMTs is known for a variety of semiconductor systems, giving promise of chip-scale frequency-agile THz imaging spectrometers. We present our calculations of transmission spectra and resonant photoresponse due to plasmons in InPand graphene-based HEMTs at millimeter and THz wavelengths. Our experimental approach to measurement of electrical response is also described. Potential applications include man-portable or space-based spectral-sensing.

Mid-infrared fiber laser sources have attracted a lot of interest in space and defense applications. We review our latest developments of various fiber laser sources operating near 2μm based on Tm³⁺ and Ho³⁺ ions, which include singlefrequency CW laser sources, Q-switched laser sources, mode-locked laser sources. Potential applications of these fiber laser sources are also briefly discussed.

There is a great deal of interests and efforts in the area of femtosecond (fs) laser direct writing of transparent materials, which shows promise to be a powerful and flexible technique for rapid fabrication of photonic micro-device, such as gratings, waveguides and optical amplifiers. Waveguide properties depend critically on the sample material properties and writing laser characteristics. In this paper, we present results on the micro-fabrication of waveguide and photonic micro-devices using fs fiber laser direct writing technique. Single line writing of different types of glasses with respect to the focused laser beam at different pulse energies and writing speeds has been investigated at first. Then the waveguide properties were characterized in terms of their shapes and transmission. It was found that specific consideration of the pulse energy, repetition rate and writing speed should be taken into account in order to fabricate low loss positive index guiding waveguide devices in a specific type of glass. Furthermore, a coupler-like guiding structure in glasses has also been demonstrated. The modified regions in both waveguides were checked by scan electron microscope (SEM) to reveal possible cracks and non-refractive structural defects. This technique can be used to produce micro photonic devices and applied to fabricate a single glass chip 3D photonic devices.

A micro resonator quantum well intensity modulator for operation in the wavelength band around 1μm is described. High efficiency 90° bends are used to form the resonator and also provide optimal coupling to the external waveguide. The benefits are to reduce loss, to relax the lithography requirements and to provide more flexible contact designs to the modulator. The characteristics of modulator are analyzed using optical simulation tools and based on measured absorption parameters. The modulator operates with two distinctly different electrode configurations which are both based on the index change calculated using Kramers-Kronig relations. A model including parasitic is developed for HSPICE transient simulations and run in the AGILENT ADS environment. The performance parameters are determined to be an extinction ratio of 10.4dB, a bandwidth of 33GHz, and a dc power less than 1mW for device dimensions of 16×6μm².

An optical switching fabric based on resonant optoelectronic switches is presented. The elements are comprised of two optoelectronic thyristors which have their own switching characteristic. Simultaneous switching of 40Gbps baseband data along with mm-wave optical signals is shown in a 4x4 fabric. The possible unique capabilities and performance advantages of implementation with thyristor-based switches in the fabric are discussed.

For the past decade NASA programs have utilized the Diamond AVIM connector for optical fiber assemblies on space flight instrumentation. These connectors have been used in communications, sensing and LIDAR systems where repeatability and high performance are required. Recently Diamond has released a smaller form factor optical fiber connector called the "Mini-AVIM" which although more compact still includes the tight tolerances and the ratcheting feature of the heritage AVIM. NASA Goddard Space Flight Center Photonics Group in the Parts, Packaging and Assembly Technologies Office has been performing evaluations of this connector to determine how it compares to the performance of the AVIM connector and to assess its feasibility for harsh environmental applications. Vibration and thermal testing were performed on the Mini-AVIM with both multi-mode and single-mode optical fiber using insitu optical transmission monitoring. Random vibration testing was performed using typical launch condition profiles for most NASA missions but extended to 35 Grms, which is much higher than most requirements. Thermal testing was performed incrementally up to a range of -55°C to +125°C. The test results include both unjacketed fiber and cabled assembly evaluations. The data presented here indicate that the Mini-AVIM provides a viable option for small form factor applications that require a high performance optical fiber connector.

High power pulsed lasers are commonly deployed in harsh environments, like space flight and military missions, for a variety of systems such as LIDAR, optical communications over long distances, or optical firing of explosives. Fiber coupling of the laser pulse from the laser to where it is needed can often save size, reduce weight, and lead to a more robust and reliable system. Typical fiber optic termination procedures are not sufficient for injection of these high power laser pulses without catastrophic damage to the fiber endface. In the current study, we will review the causes of fiber damage during high power injection and discuss methods used to avoid these issues to permit fiber use with high reliability in these applications. A brief review of the design considerations for high peak power laser pulse injection will be presented to familiarize the audience with all the areas that need to be considered during the design phase. The majority of this paper focuses on the proper fiber polishing methods for high power use with an emphasis on laser polishing of the fibers. Results from recently build fibers will be shown to demonstrate the techniques.

The near-Earth space radiation environment includes energetic galactic cosmic rays (GCR), high intensity proton and electron belts, and the potential for solar particle events (SPE). These sources may penetrate shielding materials and deposit significant energy in sensitive electronic devices on board spacecraft and satellites. Material and design optimization methods may be used to reduce the exposure and extend the operational lifetime of individual components and systems. Since laboratory experiments are expensive and may not cover the range of particles and energies relevant for space applications, such optimization may be done computationally with efficient algorithms that include the various constraints placed on the component, system, or mission. In the present work, the web-based tool OLTARIS (On-Line Tool for the Assessment of Radiation in Space) is presented, and the applicability of the tool for rapidly analyzing exposure levels within either complicated shielding geometries or user-defined material slabs exposed to space radiation is demonstrated. An example approach for material optimization is also presented. Slabs of various advanced multifunctional materials are defined and exposed to several space radiation environments. The materials and thicknesses defining each layer in the slab are then systematically adjusted to arrive at an optimal slab configuration.

Although much of the early developments of organic and polymer-based materials were fueled by the research on space materials, most of the optoelectronic applications for usage in space or terrestrial adverse environments are still dominated by semiconductors. In this paper, we review past and present efforts to incorporate organic-based materials into photonic devices that are suitable for applications in space environments, and discuss what are the main challenges that materials based on organics must meet in order to become fully integrated into photonic devices that can operate in space and space-related environments.

The use of piezoelectric polymers has been proposed and investigated in different Space-related environments, for example, as ultra-light mirrors in space telescopes or as piezoelectric actuators. Even though some piezoelectric polymers have been shown to be as efficient as the more traditional piezoelectric crystals, no systematic exploration of the different molecular motives available for piezoelectricity has been performed, partly due to experimentally challenging conditions: new structures must be generated in enough quantity to be able to produce thin films, and with measurable piezoelectric response. Consequently, few structure-property relationships have been derived for the piezoelectric performance of polymer based materials. We show how, under certain conditions, the characterization of the second-order nonlinear molecular response through the Hyper-Rayleigh scattering technique, can be used as a screening technique for the optimization of the piezoelectric response of poled-doped materials. In contrast to the piezoelectric characterization, a Hyper-Rayleigh experiment can be performed with minimal amounts of chromophores (~mg) in solution, and is relatively quick. Therefore, we propose to use the Hyper-Rayleigh scattering technique as a screening tool for the search of optimized piezoelectric polymers.

In the present work we use the Monte Carlo method to study the nonlinear optical response classified by energy spacing of the system, aiming to understand certain unresolved questions including the gap between experimental values of the off-resonant hyperpolarizabilities of molecules and the fundamental limit. The results suggest an explanation for the origin of the factor of 20-30 gap between the best molecules and the fundamental limits and also confirm the validity of three-level ansatz, which states that when the first and second hyperpolarizabilities of a quantum system are at the limit, only three states contribute to the nonlinear response.

Conjugated polymers do not only attract great attention due to their suitability in organic transistors, light emitting diodes and solar cells, moreover, they posses unexpected record-high second-order nonlinear optical responses. Nonlinear optical polymers have been reported as attractive materials for space applications such as electro-optic modulation and optical power limiting. In this work, we report on a new approach for increased second-order nonlinear properties demonstrated in a series of poly(thiophene) derivatives and poly(phenanthrene)s.

An overview of recent fiber based component developments is presented that lead to robust all-fiber lasers and optical amplifiers. Critical issues impacting the integration of high power rare earth doped optical amplifiers are presented. The optical performance of key fiber components is reported with emphasis on temperature effects of a monolithically integrated multi-Watt, single mode, Polarization Maintaining (PM), Ytterbium (Yb) doped double clad optical amplifier. Performance of an all-fiber optical amplifier design that integrates two fiber coupled laser diode pumps and one PM Yb double clad feed through fiber directly in to a combiner is reported.

We report an all fiber-based single-frequency Q-switched 2 μm pulsed laser based on highly Tm-doped germanate fiber by using a piezo to induce stress in fiber laser cavity. The pulse width of this Q-switched fiber laser can be tuned from 10's ns to sub-μs. The repetition rate can be tuned from 100 Hz to 100's kHz. The average power is ~ mW-level, peak power wattlevel, and pulse energy 30-75 nJ without any amplifier. Moreover, this transform-limited fiber laser pulses has been scaled up to 220 μJ by using a newly developed SM PM highly Tm-doped germanate fiber 25/250μm for transform-limited 80 ns pulses at repetition rate 20 kHz. This narrow linewidth high energy MOPA-based pulsed fiber laser can be used for LIDAR and laser remote sensing.

Laser quality, polycrystalline oxide fibers offer significant advantages over state-of-the-art silica fiber for high energy lasers. Advanced ceramic processing technology, along with a novel powder production process, has potential to produce oxide fibers with an outstanding optical quality for use in the fiber laser applications. The production of contaminant-free green fibers with a high packing density, as well as uniform packing distribution, is a key factor in obtaining laserquality fibers. High quality green fibers are dependent on the powder quality combined with the appropriate slurry formulation. These two fundamental technologies were successfully developed at UES, and used to produce Yb-doped yttrium aluminum garnet (YAG) fibers with high optical quality, high chemical purity, and suitable core diameters down to 20-30 microns.

The development of the first fully integrated 4-channel fiber optic gyroscope "optical engine" is presented. The optical engine integrates the equivalent of more than 24 discrete optical components into a hybrid chip with a size of 67x11x3 mm. After the optical engine is spliced to fiber sensor coils, the performance of the gyroscope has been benchmarked to be equivalent to the performance of a navigation grade gyroscope fabricated with discrete components.

Much work has been conducted and published in the area of radiation hardening of electronics. These efforts have yielded an array of techniques and design protocols for mitigating radiation effects in hardware. However, in the field of MEMS sensor systems, radiation can impact not only the support structure but the MEMS structure itself. In this work, a new multiple degree-of-freedom MEMS inertial sensor called MARS (MEMS Annular Rotating Sensor) has been subjected to Co⁶⁰ gamma-ray irradiation and results analyzed for total dose effects. Pre- and post-radiation tests reveal that the sensor's accelerometer noise performance is enhanced by the exposure. Quantitatively, noise levels improved after radiation by roughly 40% in the X and Y axes and 75% in the Z axes. Additionally, any effects of radiation on sensor offset were not discernable.

We present our efforts on development of high performance low noise, long-wave infrared (LWIR) and multicolor detectors based on the InAs/GaSb strained layer material (SLS) material system. The LWIR SLS detector with PbIbN architecture showed improved performance over the conventional PIN design due to unipolar current blocking layers. At 77K and V_b=-0.25V, a responsivity of 1.8 A/W, dark current density of 1.2 mA/cm², quantum efficiency of 23% and shot noise limited detectivity (D*) of 8.7×10¹⁰ Jones (λ_c = 10.8 μm) has been observed. Dual band response was registered with 50% cut-off wavelengths of 5μm and 10μm from an SLS detector with the pBp design. The responsivity equal to 1.6 A/W (at λ = 5 μm and V_b = +0.4 V) and 1.8 A/W (at λ = 9 μm and V_b = -0.7 V) for MWIR and LWIR absorbers was achieved with corresponding values of specific detectivity 5 x 10¹¹ Jones and 2.6 x 10¹⁰ Jones, respectively. The maximum values of quantum efficiency were estimated to 41% (MWIR) and 25% (LWIR) at V_b = +0.4V and V_b = -0.7V. Moreover, the diffusion-limited behavior of dark current at higher temperatures was observed for the MWIR absorber for pBp detector. Finally, three-color response was registered from three contact device with nBn architecture for SWIR and MWIR and heterojunction PIbN architecture for LWIR detection (NbNbiP). At 77K, the cut-off wavelength for SWIR, MWIR and LWIR regions have been observed as 3.0 μm, 4.7 μm, and 10.1 μm respectively. At the same temperature, D* of 1.4 × 10¹⁰ Jones, 1.8 × 10¹⁰ Jones and 1.5 × 10⁹ Jones for SWIR, MWIR and LWIR signals has been observed.