This PDF file contains the front matter associated with SPIE Proceedings Volume 6713, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

We have investigated an optical signal processor using electro-optic polymer waveguides at 1.55 μm. As a result of recent polymer development many new optical devices are becoming available such as optical filters, modulators, switches, multiplexers, etc. It would be useful to have a single optical device, which is reconfigurable, to implement all of these optical devices functions. We call such a device an 'Optical Signal Processor', which will play a similar role as digital signal processors in electrical circuits. We have realized such an optical device using optical-delay-line circuits. Since optical-delay-line circuits are based on the multiple interference of coherent light and can be integrated with enough complexity, they have been utilized for purposes of optical processing such as optical filters. However, the guiding waveguides that were used are passive and the only mechanism used to reconfigure their functions has been thermal. This is slow and cannot be used for high speed applications such as optical modulators and optical packet switches. On the other hand, electro-optic polymers have a very high electro-optic coefficient with a good velocity match between the electrical and optical signals which makes them ideal for efficient, high speed, devices. Therefore, we have investigated delay line optical signal processor circuits using the electro-optic polymer waveguides. These structures are complex enough to generate arbitrary functions and fast enough to obtain high data rates. Using these optical signal processors, we have investigated interesting applications including arbitrary waveform generators.

The results of three independently strategies for the optimizations of electro-optic organic chromophores is presented. The first strategy to enhance the nonlinear optical response, applied at the molecular level, is the extension of the conjugation path in a ionic chromophore. The second strategy, applied at the supramolecular level, is the bottom-up nano-engineering of an inclusion complex of the ionic chromophore in an amylose helix. The third strategy, also applied a the molecular level, is to use a modulated conjugation path between donor and acceptor in order to localize eigenfunctions on different parts of the molecule. The first hyperpolarizability of the different series of compounds has been experimentally determined by frequency-resolved femtosecond hyper-Rayleigh scattering. The effects of the three different enhancement strategies are analyzed and interepreted in terms of the quantum limits.

Semiconducting polymers are a rapidly advancing class of optoelectronic materials. They give efficient light emission under optical or electrical stimulation, and offer promise as compact, lightweight and simple to fabricate lasers. The development of such active polymer components complements developments in polymer fibre and planar lightwave circuits opening new directions in polymer integrated optics. In this article progress towards making compact practical polymer lasers is described. The potential for polymer lasers to operate in the space radiation environment is also discussed.

Recent studies have indicated that polymers integrated with nanoparticles and nanostructures have a high potential for increasing the space radiation resistance and hardening of photonic and electronic components. Discussed within this paper are recent data which support the premise that certain nanotechnology may improve the radiation resistance of organics, polymers, biopolymers and hybrid polymer-inorganic materials and devices to ionizing and displacement radiations. These materials are also being investigated for their ability to provide protective radiation shielding to a wide spectrum of radionuclide and galactic cosmic ray emissions such as alpha particles, protons, electrons, gamma-rays, beta rays, x-rays and neutrons. The appeal for advancing nanotechnology based materials and devices in many cases centers on the rapid development of hardened, economical and lightweight technologies that surpass the performance of current photonic, biotronic and microelectronic device and material technologies.

When certain molecules are doped into polymers, they are photo-chemically more stable to photodegradation than the same molecule in liquid solution or crystalline form. Furthermore, such composite materials are also found to self heal after photo-damage when they are stored in the dark. Repeated laser cycling of these dye-doped polymers make them more immune to future photodegradation. In parallel, it has been observed that electrooptic devices made with poled dye-doped polymers become more robust upon irradiation by gamma-rays. In the present work, we combine both gamma radiation and laser cycling and find that the synergism between the two processes may result in more robust materials.

Hybrid sol-gel/polymer electro-optic modulators with horizontal taper structure have been designed and fabricated. Optical transition between sol-gel passive waveguides and electro-optic polymer waveguides via horizontal tapers has been realized in the electro-optic modulators. With 1cm interaction length these hybrid electro-optic modulators have been measured to have a half-wave voltage of 8.91 V (dual drive 4.45 V), an extinction ration of 21.2dB and an optical insertion loss of 11.8 dB.

In this work, we describe a technique for positioning the passband and monitoring the slowing factor of Moiré gratings written into PMMA-DR1 waveguides during fabrication. Slow light structures made with material platforms such as silicon must fabricated before their actual slowing properties can be measured. In our dye doped polymer waveguides, the slowing can be decided beforehand and the fabrication controlled to achieve the desired performance figure. The resulting group velocity slowing in the composite waveguide can be controlled by varying the index contrast of the grating. In dye-doped polymer materials we use, the index contrast can be changed using the process of irreversible photobleaching. Our technique uses a broadband source to monitor the reflectance spectrum of the grating and the delay of the structure is determined from this measurement. The theory behind the technique is reviewed and results are presented for a Moiré grating written into waveguides fabricated in the dye-doped polymer material system, PMMA-DR1.

Under the high energy irradiation, the charges (even little) of molecules of polymer can cause the physical and chemical characteristics evident changes of polymer. The physics and chemical mechanisms which are responsible for radiation induced loss was analyzed. The radiation damage of polymethylmethacrylate (PMMA), Polystyrene PS and polycarbonate (PC) optical fiber under γ-ray irradiation was researched experimentally. The visible light transmission of the POF under different irradiation dose was measured. The results indicated that the radiation damage of three kinds of POF was wavelength-dependent. Under lower dose below 1KGy, the transmission rate decreased identical in the whole visible light range. When the irradiation dose exceeded 5KGy, the transmission rate reduced obviously, and the recovery indicated that the visible light transmission rate of the POF in the range of 400nm to 500nm comparing with 600nm to 800nm, decreased seriously under the irradiation dose exceeded 5kGy. The transmission rate of both PMMA and PC have an evident peak value at the range 550nm-650m, and that of PS has a wide band at the range 500-700nm. We also measured the recovery of three kinds of POF under different irradiation dose by measuring several times the POF after stopping irradiating.

Satellite and space-based applications of photonic devices and systems require operational reliability in the harsh environment of space for extended periods of time. This in turn requires every component of the systems and their packaging to meet space qualifications. Acousto- and electro-optical devices form the major components of many current space based optical systems, which is the focus of this paper. The major space qualification issues are related to: mechanical stability, thermal effects and operation of the devices in the naturally occurring space radiation environment. This paper will discuss acousto- and electro-optic materials and devices with respect to their stability against mechanical vibrations, thermal cycling in operating and non-operating conditions and device responses to space ionizing and displacement radiation effects. Selection of suitable materials and packaging to meet space qualification criteria will also be discussed. Finally, a general roadmap for production and testing of acousto- and electro-optic devices will be discussed.

NASA Langley Research Center is involved in the development of photonic devices and systems for space exploration missions. Photonic technologies of particular interest are those that can be utilized for in-space communication, remote sensing, guidance navigation and control, lunar descent and landing, and rendezvous and docking. NASA Langley has recently established a class-100 clean-room which serves as a Photonics Fabrication Facility for development of prototype optoelectronic devices for aerospace applications. In this paper we discuss our design, fabrication, and testing of novel active pixels, deformable mirrors, and liquid crystal spatial light modulators. Successful implementation of these intelligent optical devices and systems in space, requires careful consideration of temperature and space radiation effects in inorganic and electronic materials. Applications including high bandwidth inertial reference units, lightweight, high precision star trackers for guidance, navigation, and control, deformable mirrors, wavefront sensing, and beam steering technologies are discussed. In addition, experimental results are presented which characterize their performance in space exploration systems

Advanced photonic devices and systems typically include electronic components for signal transduction, signal processing, and actuation. Mature and stable silicon microfabrication technologies offer a generous menu of options for building application-specific integrated circuits (ASICs) for reasonable dollar costs. An ASIC device can compress complex electronic functions into a single silicon chip, greatly reducing the size and mass of the electronic portion of the system. We discuss the use of mature-technology silicon ASICs for electronic interface to cutting-edge-technology optical sensors and actuators, including considerations of how the space environment impacts the ASIC design, and noting the interesting fact that consideration of silicon area is nearly irrelevant to the present-day economics of low-volume ASIC fabrication.

Spectrally tunable liquid crystal filters provide numerous advantages and several challenges in space applications. We discuss the tradeoffs in design elements for tunable liquid crystal birefringent filters with the special considerations required for space exploration applications. In this paper we present a summary of our development of tunable filters for NASA space exploration. In particular we discuss the application of tunable liquid crystals in guidance navigation and control in space exploration programs. In conclusion, the current state of the art of several NASA LaRC assembled filters is presented and their performance compared to the predicted spectra using our PolarTools modeling software.

A quantum dot longwave infrared photodetector with vertically integrated optical amplifier structure is presented. The optical gain of ~ 15dB can be achieved. Such integrated QDIP and optical amplifier structure is promising to improve the sensitivity of IR sensing and imaging systems.

A printable high-speed flexible electronics based on ultrapure carbon nanotube (CNT) solution is reported. The carrier transport layer of the CNT-flexible electronics is formed at room temperature by dispensing a tiny droplet of an electronic-grade CNT solution that does not contain any surfactant. This CNT-TFT exhibited a high modulation speed of 312 MHz and a large current-carrying capacity beyond 20 mA. The carrier transport layer of the CNT-flexible electronics also show a high transparency of over 90% in the longwave infrared (LWIR) region. Such IR-transparent electronics are of great importance for a great variety of applications including IR-transparent smart-skins, IR-invisible antennas, and embedded IR-sensing, imaging and communications. The ink-jet printing compatible process would enable mass production of large-area electronic circuits on virtually any desired flexible substrate at low cost and high throughput.

In this paper, we report the realization of a low-density vertically aligned carbon nanotube (VA-CNT) array and show that it can have an ultra-low total reflectance due to its nanoscale surface roughness and low index of refraction as recently predicted by theories. Our VA-CNT arrays have a total reflectance R=0.1%, which is 60%-80% lower than the previously reported lowest value, making it the best candidate for an ideal, all-angle, all-wavelength optical absorber.

Traditionally, the broadband amplified spontaneous emission (ASE) source is considered to be used as the light source for the fiber Bragg grating (FBG) sensing technology. However, this kind of light source has some disadvantages − the huge volume and the high power consumption. These shortages will hamper the development of FBG sensing technology in some kind of applications such as unattended sensor and space environment. In this paper, the authors will present a new approach, the usage of the light emitted diode (LED) as the light source. The LED source is very compact, easy to integrate, and significantly reduced the cost and power consumption. But the light density of LED is so weak that the useful signal is almost buried by noise. A solution proposed by our group is to enhance SNR by digital signal processing (DSP) technology, including high frequency modulation, phase-lock amplifier, encoding on LED and decoding on the synchronistic detection. The experimental results show our effort could significantly increases the signal noise ratio (SNR) and make FBG sensor practical on application.

We report Quantum Dot Infrared Detectors (QDIP) where light coupling to the self assembled quantum dots is achieved through plasmons occurring at the metal-semiconductor interface. The detector structure consists of an asymmetric InAs/InGaAs/GaAs dots-in-a-well (DWELL) structure and a thick layer of GaAs sandwiched between two highly doped n-GaAs contact layers, grown on a semi-insulating GaAs substrate. The aperture of the detector is covered with a thin metallic layer which along with the dielectric layer confines light in the vertical direction. Sub-wavelength two-dimensional periodic patterns etched in the metallic layer covering the aperture of the detector and the active region creates a micro-cavity that concentrate light in the active region leading to intersubband transitions between states in the dot and the ones in the well. The sidewalls of the detector were also covered with metal to ensure that there is no leakage of light into the active region other than through the metal covered aperture. An enhanced spectral response when compared to the normal DWELL detector is obtained despite the absence of any aperture in the detector. The spectral response measurements show that the Long Wave InfraRed (LWIR) region is enhanced when compared to the Mid Wave InfraRed (MWIR) region. This may be due to coupling of light into the active region by plasmons that are excited at the metal-semiconductor interface. The patterned metal-dielectric layers act as an optical resonator thereby enhancing the coupling efficiency of light into the active region at the specified frequency. The concept of plasmon-assisted coupling is in principle technology agnostic and can be easily integrated into present day infrared sensors.

In the past year, a unique capability has been created by NASA Goddard Space Flight Center (GSFC) in support of Lunar Exploration. The photonics group along with support from the Mechanical Systems Division, developed a seven fiber array assembly using a custom Diamond AVIM PM connector for space flight applications. This technology enabled the Laser Ranging Application for the LRO to be possible. Laser pulses at 532 nm will be transmitted from the earth to the LRO stationed at the moon and used to make distance assessments. The pulses will be collected with the Laser Ranging telescope and focused into the array assemblies. The array assemblies span down a boom, through gimbals and across the space craft to the instrument the Lunar Orbiter Laser Altimeter (LOLA). Through use of a LOLA detector the distance between the LRO and the Earth will be calculated simultaneously while LOLA is mapping the surface of the moon. The seven fiber array assemblies were designed in partnership with W.L. Gore, Diamond Switzerland, and GSFC, manufactured by the Photonics Group at NASA Goddard Space Flight Center (GSFC) and tested for environmental effects there as well. Presented here are the requirements validation testing and results used to insure that these unique assemblies would function adequately during the Laser Ranging 14-month mission. The data and results include in-situ monitoring of the optical assemblies during cold gimbal motion life-testing, radiation, vibration and thermal testing.

The deployment of optical fibers in adverse radiation environments, such as those encountered in a low-Earth-orbit space setting, makes critical the development of an understanding of the effect of large accumulated ionizing-radiation doses on optical components and systems. In particular, gamma radiation is known to considerably affect the performance of optical components by inducing absorbing centers in the materials. Such radiation is present both as primary background radiation and as secondary radiation induced by proton collisions with space-craft material. This paper examines the effects of gamma radiation on erbium-, ytterbium-, and Yb/Er co-doped optical fibers by exposing a suite of such fibers to radiation from a Co-60 source over long periods of time while monitoring the temporal and spectral decrease in transmittance of a reference signal. For same total doses, results show increased photodarkening in erbium-doped fibers relative to ytterbium-doped fibers, as well as significant radiation resistance of the co-doped fibers over wavelengths of 1.0 - 1.6 microns. All three types of fibers were seen to exhibit dose-rate dependences.

A novel multi-mode 5-fiber array assembly was developed, manufactured, characterized and then qualified for the Lunar Orbiter Laser Altimeter (LOLA). LOLA is a science data gathering instrument used for lunar topographical mapping located aboard the Lunar Reconnaissance Orbiter (LRO) mission. This LRO mission is scheduled for launch sometime in late 2008. The fiber portion of the array assembly was comprised of step index 200/220μm multi-mode optical fiber with a numerical aperture of 0.22. Construction consisted of five fibers inside of a single polarization maintaining (PM) Diamond AVIM connector. The PM construction allows for a unique capability allowing the array side to be "clocked" to a desired angle of degree. The array side "fans-out" to five individual standard Diamond AVIM connectors. In turn, each of the individual standard AVIM connectors is then connected to five separate detectors. The qualification test plan was designed to best replicate the aging process during launch and long term space flight environmental exposure. The characterization data presented here includes results from: vibration testing, thermal performance characterization, and radiation testing.

This paper is the first in a series of publications to investigate the use of commercial-off-the-shelf (COTS) components for space flight fiber laser transmitter systems and LIDAR (laser imaging detection and ranging) detection systems. In the current study, a hermetically sealed COTS LiNbO₃ optical modulator is characterized for space flight applications. The modulator investigated was part of the family of "High-Extinction Ratio Modulators" with part number MXPE-LN from Photline Technologies in Besancon, France. Device performance was monitored during exposure to a Cobalt⁶⁰ gamma-ray source. Results from the testing show little change in device operation for a total accumulated dose of 52 krad.

The Frequency Doubler (FDR) is a component of the External Metrology subsystem on NASA's Space Interferometry Mission, performing second harmonic generation using quasi-phasematched PPLN waveguides pigtailed with polarization maintaining fiber. The need for harmonic generation on SIM is explained. Packaging and results of performance and space-qualification testing of the FDR are described.

JPL is developing an innovative compact, low mass, Electro-Optic Imaging Fourier Transform Spectrometer (E-O IFTS) for hyperspectral imaging applications. The spectral region of this spectrometer will be 1 − 2.5 μm (1000 − 4000 cm^-1) to allow high-resolution, high-speed hyperspectral imaging applications. The specific applications for NASA's missions will focus on the measurement of a large number of different atmospheric gases simultaneously in the same airmass. Due to the use of a combination of birefringent phase retarders and multiple achromatic phase switches to achieve phase delay, this spectrometer is capable of hyperspectral measurements similar to that of the conventional Fourier transform spectrometer but without any moving parts. In this paper, the principle of operations, system architecture and recent experimental progress will be presented.

We present Single Event Upset (SEU) testing of a parallel fiber optic transceiver designed for communicating data using commercial Fibre Channel and GbE protocols at data rates up to 2.5 Gbps per channel (on eight parallel channels). This transceiver was developed for aircraft applications, such as the Joint Strike Fighter (JSF), Raptor and F/A-18 aircraft, that deploy fiber optic networks using multi-mode fiber operating at 850 nm wavelength. However, this transceiver may also have applications in space environments. This paper describes the underlying transceiver component technology, which utilizes complementary metal-oxide semiconductor (CMOS) silicon-onsapphire circuitry and GaAs VCSEL and PIN devices. We also present results of SEU testing of this transceiver using heavy ions at Brookhaven National Labs.