This PDF file contains the front matter associated with SPIE Proceedings Volume 8519, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

Radio Frequency (RF) Microelectromechanical System (MEMS) switches are becoming important building blocks for a variety of military and commercial applications including switch matrices, phase shifters, electronically scanned antennas, switched filters, Automatic Test Equipment, instrumentation, cell phones and smart antennas. Low power consumption, large ratio of off-impedance to on-impedance, extreme linearity, low mass, small volume and the ability to be integrated with other electronics makes MEMS switches an attractive alternative to other mechanical and solid-state switches for a variety of space applications. Radant MEMS, Inc. has developed an electrostatically actuated broadband ohmic microswitch that has applications from DC through the microwave region. Despite the extensive earth based testing, little is known about the performance and reliability of these devices in space environments. To help fill this void, we have irradiated our commercial-off-the-shelf SPST, DC to 40 GHz MEMS switches with gamma-rays as an initial step to assessing static impact on RF performance. Results of Co-60 gamma-ray irradiation of the MEMS switches at photon energies ≥ 1.0 MeV to a total dose of ~ 118 krad(Si) did not show a statistically significant post-irradiation change in measured broadband, RF insertion loss, insertion phase, return loss and isolation.

Photonic methods for electric field sensing have been demonstrated across the electromagnetic spectrum from near-DC to millimeter waves, and at field strengths from microvolts-per-meter to megavolts-per-meter. The advantages of the photonic approach include a high degree of electrical isolation, wide bandwidth, minimum perturbation of the incident field, and the ability to operate in harsh environments.

Aerospace applications of this technology span a wide range of frequencies and field strengths. They include, at the high-frequency/high-field end, measurement of high-power electromagnetic pulses, and at the low-frequency/low-field end, in-flight monitoring of electrophysiological signals. The demands of these applications continue to spur the development of novel materials and device structures to achieve increased sensitivity, wider bandwidth, and greater high-field measurement capability.

This paper will discuss several new directions in photonic electric field sensing technology for defense applications. The first is the use of crystal ion slicing to prepare high-quality, single-crystal electro-optic thin films on low-dielectricconstant, RF-friendly substrates. The second is the use of two-dimensional photonic crystal structures to enhance the electro-optic response through slow-light propagation effects. The third is the use of ferroelectric relaxor materials with extremely high electro-optic coefficients.

TetraVue is developing a MegaPixel-class 3D camera system that uniquely addresses autonomous spacecraft requirements for a situational awareness sensor during the planetary landing phase. TetraVue's system uses a novel approach to FLASH LIDAR which utilizes existing commercial off-the-shelf (COTS) focal plane arrays in a single aperture module. This makes the system flexible enough to adapt to different resolution requirements without reinventing the hardware architecture or develop new imaging sensors with custom readout circuitry. Since the system uses a nanosecond-class laser as an illumination source, similar to a strobe, the data is insensitive to any discernable cross-motion which make it ideally suitable for landing site selection during the horizontal coast phase.

Resistance to temperature and ionizing radiation of space optoelectronic devices can be improved through control of carrier kinetics in nanoscale systems. Recent results in the science and technology of self-assembled heteroepitaxial InAs quantum dot (QD) medium related to photonic applications are discussed. Focus is placed on management of carrier kinetics via nanoengineering of electronic spectrum and potential profiles in the QD ensemble using modeling and controlled fabrication of QDs with molecular beam epitaxy. Shape-engineered QD sheets embedded into GaAs quantum wells were found to withstand two orders of magnitude higher proton dose than QWs and to account for high luminescence efficiency and thermally stable laser diodes. Built-in charge in QDs is responsible for improvement of both near and mid-IR optical absorption, but also control photoelectron lifetime in the structures. The negatively charged QD medium was the first QD material that has recently shown credible improvement of solar cell efficiency. It has resulted from IR energy harvesting and suppressed fast electron capture processes. It is thus expected that QD InAs/GaAs photovoltaics will overcome the efficiency and lifespan of multi-junction solar cells. Potentials due to QD built-in charge are also responsible for improved photoelectron lifetime in QD infrared photodetectors. QD correlated clusters provide even higher collective potential barriers around clusters and constitute the novel approach to the optoelectronic materials combining manageable photoelectron lifetime, high mobility, and tunable localized and conducting states.

An all guided-wave multi-spectral laser source emitting watts to tens-of-watts of mid-infrared power would impact a broad range of airborne and space applications. As compared with a free-space solid-state laser source, a guided-wave design, composed of coupled lasing and nonlinear optical components, offers potential advantages in size, weight, efficiency, and mechanical robustness while retaining high beam quality for single-mode designs. New material options under development by the Materials and Manufacturing Directorate of the Air Force Research Laboratory (AFRL) enable new approaches to achieving such a source.

Polymer thin film based optoelectronic devices including solar cells appear attractive for space applications where lightweight, large size, low cost, and flexible shape are desirable. The photoelectric power conversion efficiencies of currently reported polymer solar cells are still relatively low (typically less than 8% under AM 1.5 and one Sun intensity) due to several losses, i.e., the ‘photon loss’ due to mismatch of materials energy gaps versus the sunlight photon energies, the ‘exciton loss’ and the ‘carrier loss’ due to poor solid state morphologies of existing polymeric donor/acceptor binary systems. Therefore, both molecular frontier orbitals (HOMOs, LUMOs) and phase morphologies need to be optimized to further enhance the efficiency. In this presentation, our recent efforts on frontier orbital and morphology engineering of conjugated polymer blocks and corresponding block copolymers will be reviewed. The HOMO/LUMO energy gaps of the new polymers were in a range of 1.5-2.0 eV which are attractive for solar cell applications. The terminal functional groups of donor and acceptor type conjugated blocks make them potentially ideal candidates for the development of donor/acceptor block copolymer supramolecular nanostructures for a variety of high efficiency optoelectronic applications. Dye sensitized triple system appear attractive for high efficiency optoelectronics due to reduction of charge recombination.

We review a model that was developed to take into account all possible microscopic cascading schemes in a single species system out to the fifth order using a self-consistent field approach. This model was designed to study the effects of boundaries in mesoscopic systems with constrained boundaries. These geometric constraints on the macroscopic structure show how the higher-ordered susceptibilities are manipulated by increasing the surface to volume ratio, while the microscopic structure influences the local field from all other molecules in the system. In addition to the review, we discuss methods of modeling real systems of molecules, where efforts are currently underway.

Previous studies on the radiation effects upon polymer and polymer-based photonic materials suggest that the radiation resistance of the material is heavily dependent on the choice of polymer-host and guest-chromophore. To date, the best results have been achieved with electro optic polymeric materials based on CLD1 doped in APC, which has resulted in improved performance at the device level upon gamma-ray irradiation at moderate doses. However, the physical mechanisms are yet not fully understood. In this paper, we introduce an all-optical (linear and nonlinear) characterization protocol that is aimed to elucidate the mechanisms of the radiation damage/enhancement of electro-optic polymeric materials. This protocol is used to quantify the damage/enhancement effects upon irradiation in terms of the relevant physical parameters on a collection of electro-optic polymeric thin film samples.

We contrast two numerical approaches that are used to optimize the intrinsic hyperpolarizability: potential optimization and sum-rule-constrained Monte Carlo simulations. Our aim is to resolve inconsistencies between the two. We show that while the first method accurately reflects the properties of real physical systems, the second requires exotic hamiltonians that obey sum rules but may not represent a physical reality. Under certain extreme conditions, the sum-rule-constrained approach leads to systems that may not be representable by any Schrodinger Equation in differential equation form.

Self healing of chromophores in a dye-doped polymer after photodegradation is a counterintuitive process based on the nearly universal observation that molecular damage is a thermodynamically irreversible process. We propose a new simple model of this phenomenon that takes into account all observations, including the effects of concentration, temperature, and bystander states. Critical to this model are correlations between chromophores, perhaps mediated by the polymer, which actively favors the undamaged species in analogy to Bose-Einstein condensation. We use this model to predict the behavior of decay and recovery experiments as measured with amplified spontaneous emission and absorption spectroscopy.

We observe that many different derivatives of anthraquinone chromophores doped in PMMA self heal after undergoing photodegradation. We are interested to know the mechanisms that are responsible for photodegradation and photorecovery, which are not yet fully understood. We used fluorescence and absorption spectroscopy as a probe of the photodegradation and recovery process while the temperature dependence is used to determine the energies of the species involved. We hypothesize that the host polymer mediates the formation of a quasi-stable state. In this scenario, once photo - damaged by intense pump laser, the molecules non radiatively decay into a tautomer state by intra molecule proton transfer, which subsequently leads to the formation of a damaged species - leading to decay of the fluorescence intensity. This hypothesis is consistent with our observation. The temperature dependent fluorescence decay and recovery studies give an insight about the different energy levels participating in optical excitation, decay and recovery. Comparing the experimental parameters such as decay and recovery rates of the fluorescence signal associated with the evolution of peaks in the fluorescence and absorbance spectrum helps us understand correlations between the efficiency of the recovery process and the structures of the dye molecules. Based on the temperature and the time-dependent observations of fluorescence and absorption, we validate qualitatively a new theoretical model which qualitatively takes into account the observed behavior and sheds light on the underlying mechanism. Preliminary measurements show good agreement with the theoretical model. More careful experiments and calculations are in process for further validation of the model.

We study the role of polymer-chromophore and chromophore-chromophore interactions in reversible photodegradation of Disperse Orange 11 dye-doped thin films using temperature dependent studies of amplified spontaneous emission for several dye concentrations. The temperature dependence of the process determines both the ground state energies of the species involved and the role of the polymer; and, the concentration dependence gives information about the role of dye-dye interactions. We find that the material is more resistant to photo-damage at higher dye concentrations. This data is used to validate a new model of the process.

One of the limiting factors of optical devices for space applications is photodamage from high intensity light and radiation. Dye doped polymers offer many advantages in device design but are susceptible to photodamage, especially due to high intensity UV radiation. Several organic dyes have been observed to self heal after photodegradation. We seek to understand the underlying mechanism with the goal of designing materials that are more robust to photodegradation. We test the hypothesis that photodegradation is due to charge injection into the polymer and healing due to recombination using photoconductivity and imaging measurements of disperse orange 11(DO11) doped into PMMA.

It has been shown that the chromophore disperse red 1 azobenzene (DR1) when doped into poly(methyl methacrylate) (PMMA) optical fiber can be used to make an optical cantilever in which an asymmetrically propagating beam at 633nm causes the fiber to bend. The fast response process is purported to be due to elongation of the material as molecules change between cis and trans isomers. In our work, UV light of 350nm will be used to investigate trans to cis somerization, which should induce contraction. Short fiber segments in a three-contactpoint geometry will be used to control the position and tilt of silver- or aluminum-coated coverslips that together with microscope glass slides as the substrate make optically-actuated beam-controlling mounts and Fabry-Perot interferometers. A Michelson interferometer is used to measure the length change of the fiber actuator. Azodye doped liquid crystal (LC) elastomers have been demonstrated to have a photomechanical effect that is at least ten times bigger than thermoplastic-based polymer fiber. However, the optical quality of thermoplastics are much better, enabling the cascading of devices in series. We will report on visible and UV laser-actuation of LC elastomer and polymer device structures using a quadrant photodetector to record the beam deflection caused by the shape change of the material, which will allow for dynamical measurements of the mechanisms. All measurements will be calibrated against a piezoelectric crystal actuator. Photomechanical devices provide an inexpensive but versatile, small-form factor, vibration free and high precision solution to optomechanics, sensing, positioning and other space applications.

Currently, there is considerable interest in developing technologies that will allow the use of high-energy photon measurements from celestial X-ray sources for deep space relative navigation. The impetus for this is to reduce operational costs in the number of envisioned space missions that will require spacecraft to have autonomous, or semiautonomous, navigation capabilities. For missions close to Earth, Global Navigation Satellite Systems (GNSS), such as the U.S. Global Positioning System (GPS), are readily available for use and provide high accuracy navigation solutions that can be used for autonomous vehicle operation. However, for missions far from Earth, currently only a few navigation options exist and most do not allow autonomous operation. While the radio telemetry based solutions with proven high performance such as NASA’s Deep Space Network (DSN) can be used for these class of missions, latencies associated with servicing a fleet of vehicles, such as a constellation of communication or science observation spacecraft, may not be compatible with autonomous operations which require timely updates of navigation solutions. Thus, new alternative solutions are sought with DSN-like accuracy. Because of their highly predictable pulsations, pulsars emitting X-radiation are ideal candidates for this task. These stars are ubiquitous celestial sources that can be used to provide time, attitude, range, and range-rate measurements — key parameters for navigation. Laboratory modeling of pulsar signals and operational aspects such as identifying pulsar-spacecraft geometry and performing cooperative observations with data communication are addressed in this paper. Algorithms and simulation tools that will enable designing and analyzing X-ray navigation concepts for a cis-lunar operational scenario are presented. In this situation, a space vehicle with a large-sized X-ray detector will work cooperatively with a number of smaller vehicles with smaller-sized detectors to generate a relative navigation solution between a reference and partner vehicle. The development of a compact X-ray detector system is pivotal to the eventual deployment of such navigation systems. Therefore, efforts to design a smallpackaged X-ray detector system along with the hardware, software and algorithm infrastructure required for testing and validating the system’s performance are described in this paper.

The potential of bio-dielectrics for space applications was explored using deoxyribonucleic acid (DNA)-based biopolymers. Un-doped DNA, as well as titanium dioxide (TiO₂) nanoparticle (rutile form)-doped DNA were processed and evaluated. Characterized parameters were temperature stability, resistivity, dielectric constant, dielectric loss and radiation tolerance. The dielectric constant and dielectric loss of un-doped DNA and TiO₂-doped DNA were measured for both pre- and post- exposure to approximately100 krad Gamma-ray radiation. There was little change in the dielectric constant and dielectric loss of the un-doped DNA sample with exposure to radiation. However, there was a significant reduction in the dielectric constant of the TiO₂-doped DNA sample.

Micro- and nano-processing are performed by using a high energy mode-locked femtosecond (fs) fiber laser. The laser beam has 1030 nm center wavelength, 750 fs pulse duration and up to 10 μJ pulse energy. Firstly, direct writing of optical waveguide inside glass materials is presented and a 3-D curved waveguide is demonstrated. Secondly, by taking advantages of fs laser deterministic damage threshold, micrometer and sub-micrometer features are obtained for surface ablation. Thirdly, fs UV (FHG, 258 nm) laser processing is investigated and nanometer features are obtained. Periodic structures in good order are also found and the patterns extend coherently over many overlapping laser pulses and scanning tracks. It has 100 nm period, 50 nm width and 50 nm depth. Such micro and nano processing method suggests a possible technique to produce nanogratings, microelectronics, or nanopatterned surfaces of micro-sensors for space optoelectronics.

We demonstrate a single-frequency gain-switched Ho-doped fiber laser based on heavily doped silicate glass fiber fabricated in house. A Q-switched Tm-doped fiber laser at 1.95μm was used to gain-switch the Ho-doped fiber laser via in-band pumping. Output power of the single-frequency gain-switched pulses has been amplified in a cladding-pumped Tm-Ho-codoped fiber amplifier with 1.2m active fiber pumped at 803nm. Two different nonlinear effects, i.e., modulation instability and stimulated Brillouin scattering, could be seen in the 10μm-core fiber amplifier when the peak power exceeds 3kW. The single-frequency gain-switched fiber laser was operated at 2.05μm, a popular laser wavelength for Doppler lidar application. This is the first demonstration of this kind of fiber laser.

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. Several laser and lidar components were sent by NASA Langley Research Center (LaRC) as a part of the MISSE 7 mission. The MISSE 7 module was transported to the international space station (ISS) via STS 129 mission that was launched on Nov 16, 2009. Later, the MISSE 7 module was brought back to the earth via the STS 134 that landed on June 1, 2011. The MISSE 7 module that was subjected to exposure in space environment for more than one and a half year included fiber laser, solid-state laser gain materials, detectors, and semiconductor laser diode. Performance testing of these components is now progressing. In this paper, the current progress on post-flight performance testing of a high-speed photodetector and a balanced receiver is discussed. Preliminary findings show that detector characteristics did not undergo any significant degradation.