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NRL is developing new materials that transmit across wide wavelength ranges and will present recent results. MILTRAN is a new rugged optical ceramic that transmits visible through LWIR and is 3.5 times harder than ZnS and is well suited as an internal lens element. NRL-series moldable glasses transmit SWIR through LWIR and may be bonded to each other in an adhesive-free thermal process. NRL-200-series glasses transmit visible through MWIR and expand the glass map for multispectral lens designs. These new materials enable greater flexibility for designers of lenses for advanced defense applications and potentially reduce the size, weight and cost of next-generation optics.

Terpenes are naturally occurring compounds that are present throughout nature. Modern interest in terpenes and terpene analysis has grown significantly as the recreational and medicinal use of cannabis has expanded across the globe. Terpenes are the aromatic compounds that give cannabis its unique smell and flavor and are a critical aspect of the cannabis experience. They are built from repeating five carbon units called isoprene and their distinction as monoterpenes, sesquiterpenes, diterpenes, etc. is dependent on the number of isoprene units utilized in their biosynthesis. The objective of this chapter was to produce a broad overview of terpene analysis in cannabis. Several methodologies will be discussed in this chapter and it should provide a baseline for analyzing terpenes in cannabis flower and cannabis products as well as an overview of the role of gas chromatography in the cannabis laboratory.

The increase in domestic natural gas production has brought attention to the environmental impacts of persistent gas leakages. The desire to identify fugitive gas emission, specifically for methane, presents new sensing challenges within the production and distribution supply chain. A spectroscopic gas sensing solution would ideally combine a long optical path length for high sensitivity and distributed detection over large areas. Specialty micro-structured fiber with a hollow core can exhibit a relatively low attenuation at mid-infrared wavelengths where methane has strong absorption lines. Methane diffusion into the hollow core is enabled by machining side-holes along the fiber length through ultrafast laser drilling methods. The complete system provides hundreds of meters of optical path for routing along well pads and pipelines while being interrogated by a single laser and detector. This work will present transmission and methane detection capabilities of mid-infrared photonic crystal fibers. Side-hole drilling techniques for methane diffusion will be highlighted as a means to convert hollow-core fibers into applicable gas sensors.

A wide variety of optical sensors have been used for gas detection. Hollow core waveguides have shown particular usefulness due to the larger interaction volume of the optical signal with the gas species through direct absorption instead the lower interaction volume of evanescent field spectroscopy. In particular porous capillary tube waveguides (PCTW) have been of particular interest because of their very fast response time. One limitation, in particular, is the increased loss due to the nearly free space transmission through the hollow core. PCTWs have been successfully tested on a variety of gases and across a wide temperature range by our group previously. In this paper, we present the results for a fiber optic sensor structure which is composed of gold nanobridges. The gold nanobridges are formed by coating the inside of a microcapillary glass tube with gold. The glass tube is phase separated and one of the phases is removed by a leaching process. This leaves a three dimensionally interconnected porous phase and a three dimensionally interconnected glass phase which is coated with gold. The structure was analyzed for topology and chemistry using a scanning electron microscope. SEM micrographs of the microcapillary tubes both before and after phase separation were obtained. In addition, EDAX was used to confirm the presence of the gold coating on the samples after the leaching process. The porous gold film was found to be composed of approximately 100nm ligaments in an interconnected network and the glass had approximately 30nm pores around these ligaments. The process to produce these gold coated nanoporous elements is abbreviated here due to word count restriction for this abstract. Porous capillary tubes were produced from a phase separable glass composition. This type of glass produces 3-dimensionally interconnected phases through a compositional phase separation process induced by heat treatment. Porosity is created when the secondary phase or soluble phase is removed by immersion in a dilute acid solution that dissolves and leaches out the secondary phase. Capillary tubes to be plated were drawn with an inner diameter of 170-220 µm and an outer diameter range of 400-500 µm. Dimensions were selected to provide an adequate ID for plating and then the insertion of the lead-in and lead-out fibers. Drawn capillary tubes were plated using a commercially available electroless gold plating solution. Plating was accomplished after fibers were annealed to induce phase separation in order to minimize thermal changes to the gold film that the necessary heat treatment would cause. The inner diameter of the capillary tube was coated by flowing the plating solutions through the tubes. Plating was carried out per the manufacturer’s directions with the exception that the solutions were in a flowing state compared to the static application recommended. Plating occurred in a three step process with the first step being a sensitizing solution, then a brief rinse, followed by a combined mixture of an activated gold salt and a reducing agent. Flow rates of the plating solution ranged from 0.5 mL/min-2mL/min depending on tube ID. After plating, the tube and gold film was air dried followed by acid leaching of the secondary phase. Optical transmission spectra were characterized over the spectral range from 1520-1570 using a commercially available spectrometer which contained a swept laser interrogator. A Micron Optics Si-720 Component Testing System (CTS) and SMF-28 lead-in and lead-out fibers were used in the transmission testing. The apparatus constructed for the transmission tests consisted of the CTS unit with the swept laser being used as the light source connected to a SMF optical fiber as the lead-in fiber. A MMF was used for the lead out fiber to the oscilloscope which was attached to a photodetector for detection. The transmission spectrums were studied as a function of the microcapillary tubing length. By comparing the transmission spectrums of the microcapillaries before gold coating and after gold coating, it was shown that the gold coated microcapillaries had higher transmission than the uncoated for each length studied. The gold coated nanobridge enhanced fiber optic sensor system was tested in a gas cell using acetylene gas. Test concentrations ranging from 10% Acetylene down to 100ppm were obtained using a Sierra Instruments gas mixing system. From the optical spectrums measured, it was shown that the absorption peaks associated with the acetylene gas are clearly visible in the optical spectrums. The absorption peak strengths were in the range from 5-10dB depending upon which line in the acetylene absorption spectrum one is considering and what the gas concentration was. Figure 1

Dispenser cathodes operate under ultra high vacuum and high temperature conditions. Because of these harsh conditions the tungsten rhenium heater coil is surrounded by a ceramic potting material to maintain a uniform temperature profile. Many cathodes are scrapped due to cracking in the potting which could lead to thermal hot spots. This study explores alternative ceramic potting materials that pass the stringent requirements of high end cathodes including slight expansion upon sintering. Ternary aluminum nitride based ceramics were proposed with calcium oxide, yttria, and alumina as additions. The standard potting material used by Semicon Associates was also profiled. It was found that a ceramic with composition 70.5 wt% Al2O3, 23.5 wt% AlN, and 6 wt% CaO expanded 1.71 volume percent compared to 0.81 percent expansion of the standard potting. This new Al2O3/AlN/CaO material was measured to have a thermal conductivity of 3 W/mK at 1200oC and the standard potting to have 12 W/mK at 1200oC. All other compositions considered contracted significantly upon sintering, disqualifying each as a viable alternative potting material. This paper is the result of a student project performed by University of Kentucky MSE480 Senior Design class in coordination with the sponsor Semicon Associates of Lexington, KY.

A gas sensor to detect and localize leaks is being developed. Periodically perforated hollow core fiber and tunable diode laser spectroscopy in the mid-IR can provide robust ppm sensitivity with distributed detection for many gases.