General Electric has designed an innovative x-ray photonic device that concentrates a polychromatic beam of diverging x-rays into a less divergent, parallel, or focused x-ray beam. The device consists of multiple, thin film multilayer stacks. X-rays incident on a given multilayer stack propagate within a high refractive index transmission layer while undergoing multiple total internal reflections from a novel, engineered multilayer containing materials of lower refractive index. Development of this device could lead to order-of-magnitude flux density increases, over a large broadband energy range from below 20 keV to above 300 keV. In this paper, we give an overview of the device and present GE’s progress towards fabricating prototype devices.
Fiber optic distributed temperature sensing based on Raman scattering of light in optical fibers has become a very attractive solution for distributed temperature sensing (DTS) applications. The Raman scattered signal is independent of strain within the fiber, enabling simple packaging solutions for fiber optic temperature sensors while simultaneously improving accuracy and robustness of temperature measurements due to the lack of strain-induced errors in these measurements. Furthermore, the Raman scattered signal increases in magnitude at higher fiber temperatures, resulting in an improved SNR for high temperature measurements. Most Raman DTS instruments and fiber sensors are designed for operation up to approximately 300˚C. We will present our work in demonstrating high temperature calibration of a Raman DTS system using both Ge doped and pure silica core multi-mode optical fiber. We will demonstrate the tradeoffs involved in using each type of fiber for high temperature measurements. In addition, we will describe the challenges of measuring large temperature ranges (0 – 600˚C) with a single DTS interrogator and will demonstrate the need to customize the interrogator electronics and detector response in order to achieve reliable and repeatable high temperature measurements across a wide temperature range.
Fiber optic cables have been successfully deployed in ocean floors for decades to enable trans-oceanic telecommunication. The impact of strain and moisture on optical fibers has been thoroughly studied in the past 30 years. Cable designs have been developed to minimize strain on the fibers and prevent water uptake. As a result, the failure rates of optical fibers in subsea telecommunication cables due to moisture and strain are negligible. However, the relatively recent use of fiber optic cables to monitor temperature, acoustics, and especially strain on subsea equipment adds new reliability challenges that need to be mitigated. This paper provides a brief overview of the design for reliability considerations of fiber optic cables for subsea asset condition monitoring (SACM). In particular, experimental results on fibers immersed in water under varying accelerated conditions of static stress and temperature are discussed. Based on the data, an assessment of the survivability of optical fibers in the subsea monitoring environment is presented.
Here we present our work towards the development of Nanoscale Optofluidic Sensor Arrays (NOSA), which is an optofluidic architecture for performing label free, highly parallel, detections of biomolecular interactions. The approach is based on the use of optically resonant devices whose resonant wavelength is shifted due to a local change in refractive index caused by a positive binding event between a surface bound molecule and it solution phase target. A special two stage micro-/nanofluidics architecture is used to first functionalize the devices and then to deliver the targets. Two variants of the NOSA will be presented here. The first approach utilizes a 1D resonant cavity in a 1D silicon-on-insulator (SOI) waveguide with a unique differential size functionalization approach. This approach allows binding events at one or at a combination of the many sensing sites which causes a unique shift in the output resonator spectrum. The latter approach consists of a SOI waveguide evanescently coupled to multiple 1-D photonic crystal resonators of different sizes along the length, each of which is functionalized with a different oligonucleotide probe. These devices have an extremely low limit of detection and are compatible with aqueous environments. The primary advantage of these devices over existing technology is that it combines the sensitivity (limit of detection) of nanosensor technology with the parallelism of the microarray type format. Our initial application is in the detection of viral RNA of Dengue virus.
In this work we explore the possibility of developing micro-/nano-fluidic devices which exploits the intense electromagnetic fields present in nanophotonic structures as the primary transport mechanism. This transport mechanism is based on exploiting the near-field optical gradients (which serve to confine particles through a Lorenz force) and concentrated optical energy (resulting in intense scattering and absorption forces for propulsion through photon momentum transfer) present in these devices to perform a series of particle handling operations including transport, concentration and separation. Nanophotonic transport offers unique properties which give it several advantages over traditional techniques including: favorable transport scaling laws, extremely strong velocity dependence on particle size, insensitivity to surface/solution conditions and indefinitely long interaction lengths. In this work we detail the theory behind photonic transport and outline in detail the major advantages. Some of our initial experimental results on transport in liquid core photonic crystal devices and developing numerical simulation techniques describing photonic transport in such devices.