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FY 2007 Miniature Spherical Retroreflectors Final Report

Description: Miniature spherical retroreflectors, less than 8 millimeters in diameter, are currently being developed to enhance remote optical detection of nuclear proliferation activities. These retroreflecting spheres resemble small, sand-colored marbles that have the unique optical property of providing a strong reflection directly back to the source (i.e., retroreflecting) when illuminated with a laser. The addition of specific coatings, sensitive to specific chemicals or radioactive decay in the environment, can be applied to the surface of these retroreflectors to provide remote detection of nuclear proliferation activities. The presence of radioactive decay (e.g., alpha, gamma, neutron) or specific chemicals in the environment (e.g., TBP, acids) will change the optical properties of the spheres in a predictable fashion, thus indicating the presence or absence of the target materials. One possible scenario might employ an airborne infrared laser system (e.g., quantum-cascade lasers) to illuminate a section of ground littered with these retroreflective spheres. Depending on the coating and the presence of a specific chemical or radioisotope in the environment, the return signal would be modified in some predictable fashion because of fluorescence, frequency shifting, intensity attenuation/enhancement, or change in polarization. Research conducted in FY 2007 focused on developing novel optical fabrication processes and exploiting the unique material properties of chalcogenide infrared-transparent glass (germanium-arsenic-sulfur-tellurium compounds) to produce highly efficient retroreflectors. Pacific Northwest National Laboratory’s approach provides comparable performance to the ideal graded index sphere concept, developed by R. K. Luneburg in 1944 (Luneburg 1944), while greatly reducing the complexity in fabrication by utilizing chalcogenide glass materials and compression-molding processes.
Date: February 20, 2008
Creator: Anheier, Norman C.; Bernacki, Bruce E. & Krishnaswami, Kannan
Partner: UNT Libraries Government Documents Department

FY 2006 Miniature Spherical Retroreflectors Final Report

Description: Research done by the Infrared Photonics team at Pacific Northwest National Laboratory (PNNL) is focused on developing miniature spherical retroreflectors using the unique optical and material properties of chalcogenide glass to reduce both performance limiting spherical aberrations. The optimized optical performance will provide efficient signal retroreflection that enables a broad range of remote detection scenarios for mid-wave infrared (MWIR) and long-wave infrared (LWIR) sensing applications. Miniature spherical retroreflectors can be developed to aid in the detection of signatures of nuclear proliferation or other chemical vapor or radiation signatures. Miniature spherical retroreflectors are not only well suited to traditional LIDAR methods for chemical plume detection and identification, but could enable remote detection of difficult semi-volatile chemical materials or low level radiation sources.
Date: December 28, 2006
Creator: Anheier, Norman C.; Bernacki, Bruce E. & Krishnaswami, Kannan
Partner: UNT Libraries Government Documents Department

FY 2008 Miniature Spherical Retroreflectors – Final Report

Description: Through the duration of the NNSA Office of Nuclear Nonproliferation Research and Development (NA-22) Miniature Spherical Retroreflectors lifecycle project, our research team focused on developing solutions to the fabrication bottleneck that has inhibited development and deployment of wide-angle optically interrogated chemical and radiological remote sensing technology. Our team advanced the concept of step-index clad retroreflectors to approximate an optimized, but yet unrealized spherical gradient index design. An intensive numerical simulation effort was undertaken that resulted in optimized step-index optical designs for mid-infrared applications. Geometric optics ray trace modeling was performed to better understand the geometrical dependencies of the miniature spherical retroreflector application. We adopted and advanced the concept of optical cross section, a metric that provides relative performance comparisons between different retroreflector designs and our cross-section analysis demonstrated that our step-index design provided 90% of the range capacity of the ideal spherical index design.
Date: February 1, 2009
Creator: Anheier, Norman C.; Bernacki, Bruce E.; Klymyshyn, Nicholas A.; Krishnaswami, Kannan & Rodriguez, Carmen P.
Partner: UNT Libraries Government Documents Department

FY 2006 Infrared Photonics Final Report

Description: Research done by the Infrared Photonics team at Pacific Northwest National Laboratory (PNNL) is focused on developing miniaturized integrated optics and optical fiber processing methods for mid-wave infrared (MWIR) and long-wave infrared (LWIR) sensing applications by exploiting the unique optical and material properties of chalcogenide glass. PNNL has developed thin-film deposition capabilities, direct laser writing techniques, infrared photonic device demonstration, holographic optical element design and fabrication, photonic device modeling, and advanced optical metrology—all specific to chalcogenide glass. Chalcogenide infrared photonics provides a pathway to quantum cascade laser (QCL) transmitter miniaturization. The high output power, small size, and superb stability and modulation characteristics of QCLs make them amenable for integration as transmitters into ultra-sensitive, ultra-selective point sampling and remote short-range chemical sensors that are particularly useful for nuclear nonproliferation missions.
Date: December 28, 2006
Creator: Anheier, Norman C.; Allen, Paul J.; Bernacki, Bruce E.; Ho, Nicolas; Krishnaswami, Kannan; Qiao, Hong (Amy) et al.
Partner: UNT Libraries Government Documents Department

FY 2005 Infrared Photonics Final Report

Description: Research done by the Infrared Photonics team at Pacific Northwest National Laboratory (PNNL) is focused on developing miniaturized integrated optics for mid-wave infrared (MWIR) and long-wave infrared (LWIR) sensing applications by exploiting the unique optical and material properties of chalcogenide glass. PNNL has developed thin-film deposition capabilities, direct laser writing techniques, infrared photonic device demonstration, holographic optical element design and fabrication, photonic device modeling, and advanced optical metrology—all specific to chalcogenide glass. Chalcogenide infrared photonics provides a pathway to quantum cascade laser (QCL) transmitter miniaturization. QCLs provide a viable infrared laser source for a new class of laser transmitters capable of meeting the performance requirements for a variety of national security sensing applications. The high output power, small size, and superb stability and modulation characteristics of QCLs make them amenable for integration as transmitters into ultra-sensitive, ultra-selective point sampling and remote short-range chemical sensors that are particularly useful for nuclear nonproliferation missions. During FY 2005, PNNL’s Infrared Photonics research team made measurable progress exploiting the extraordinary optical and material properties of chalcogenide glass to develop miniaturized integrated optics for mid-wave infrared (MWIR) and long-wave infrared (LWIR) sensing applications. We investigated sulfur purification methods that will eventually lead to routine production of optical quality chalcogenide glass. We also discovered a glass degradation phenomenon and our investigation uncovered the underlying surface chemistry mechanism and developed mitigation actions. Key research was performed to understand and control the photomodification properties. This research was then used to demonstrate several essential infrared photonic devices, including LWIR single-mode waveguide devices and waveguide couplers. Optical metrology tools were also developed to characterize optical waveguide structures and LWIR optical components.
Date: December 1, 2005
Creator: Anheier, Norman C.; Allen, Paul J.; Ho, Nicolas; Krishnaswami, Kannan; Johnson, Bradley R.; Sundaram, S. K. et al.
Partner: UNT Libraries Government Documents Department

FY 2008 Infrared Photonics Final Report

Description: Through the duration of the NNSA Office of Nuclear Nonproliferation Research and development (NA-22) ITAS lifecycle project, the Infrared Photonics research has been focused on developing integrated quantum cascade (QC) laser technology to enable next-generation remote sensing designs. Our team developed the concept of the integrated QC laser transmitter and originated and promoted the vision of mid-infrared (3–12 μm) wavelength photonics. Sustained NA-22 project funding produced the QC laser transmitter that is now deployed in follow-on projects. Our team produced nationally recognized cutting-edge research in the area of infrared transparent chalcogenide photonics. Three technical staff were recruited from outside PNNL and hired to support this research. This project also supported student research at the national laboratory, including high school, undergraduate, and graduate students. This provided a derivative benefit to NA-22, PNNL, and the educational institutions through training and mentoring next-generation students in science and technology. The student support was also the catalyst to develop research collaborations with two universities that are internationally recognized for their chalcogenide glass research.
Date: December 1, 2008
Creator: Anheier, Norman C.; Bernacki, Bruce E.; Carlie, Nathan A.; Gervais, Kevin L.; Hatchell, Brian K.; Johnson, Bradley R. et al.
Partner: UNT Libraries Government Documents Department