The fabrication of flexible hybrid electronics involves depositing ink onto a substrate using micro-dispensing techniques, including direct ink write processes. In most cases, the ink comprises solvents, binders, and nanoparticle material. To achieve the desired printed film characteristics, the deposited ink must be treated to evaporate the solvents and binders and melt, or sinter, the nanoparticles to form a continuous film. Laser sintering is a method for achieving this process for flexible hybrid electronic production. An incident laser beam is directed onto the printed film’s surface to sinter the particles rather than alternative thermal processes. The laser sintering parameters vary with the ink film composition, substrate, and film thickness. This study uses different laser systems, film compositions, and substrates to achieve the optimal laser sintering parameters for the desired application. The inks studied include silver, doped barium titanate, and silver-palladium on glass, polyimide, and alumina substrates. This work aims to develop sintering parameters for flexible hybrid electronics fabrication on the International Space Station.
Laser sources in the mid-infrared (mid-IR) region are of great interest for use in military defense and scientific applications. Recent advancements in mid-IR fiber technology using materials such as ZBLAN and chalcogenide optical fibers open the potential to create novel mid-IR all-fiber lasers. A typical laser cavity design consists of a set of mirrors separated by the gain material. One technique for creating an all-fiber laser cavity is to create two fiber Bragg gratings (FBG) separated by a length of the fiber. Direct writing using femtosecond laser has shown to create a stable Fiber Bragg Grating that will survive under harsh environments. However, a detailed understanding of how mid-IR fiber’s refractive index (RI) varies with laser parameters is currently not well studied. In our work, we will present how the RI of ZrF4-BaF4- LaF3-AlF3-NaF (ZBLAN) and chalcogenide-based mid-IR fibers changes based on the laser power.
Concentrating Solar Power (CSP) generation is an attractive option for low-emission power generation; however, the high costs of thermal storage associated with concentrating solar create a large barrier for their use and adaptation into modern life. Lowering their operation costs, while maintaining high thermal storage and transfer performance is essential. Solid particle-based heat exchange systems can reduce CSP cost but are often less efficient. Efforts to increase their performance have led to use of binary size particle mixes. Presented is an optical-based thermal analysis technique used to measure near-wall thermal conductivity of particle beds essential in determining their heat exchanger efficiency. Modulated Photothermal Radiometry is used to make dynamic temperature measurements, allowing for the extraction of the most relevant thermal properties like thermal conductivity, specific heat, and effusivity. The system uses a modulated laser source causing a damped periodic heat flux, resulting in a frequency and thermal property dependent surface temperature, of which is measured using radiometry. Lock-In techniques are used to extrapolate the amplitude of the signal. Plotting the amplitude against the root angular frequency allows for effusivity measurement by ratio to a known sample. Using specific heat measurements from literature and density measurements, the thermal conductivity of the particle mixes can be calculated. The simplicity of MPTR to probe through the depth of the bed is ideal for use in CSP for dynamic thermal performance monitoring.
We experimentally demonstrate a reflective long period grating based temperature sensor with a temperature sensitivity coefficient of 0.046 nm/°C in the range between 23°C and 200°C. Compared to traditional metal coating methods, such as evaporation, we used a cost-effective brush coating method to coat silver on both the end facet and a 60cm long tail end of the fiber beyond a long period grating (LPG) to realize a reflection mode LPG. The measured optical spectrum of the fabricated reflective LPG completely mimics the transmitted spectrum with reduced intensity. This cost-effective method for coating metal will pave the way for inexpensive LPG and other optical fiber sensor manufacturing and widespread utilization.
A novel and cost-effective technique to coat a fiber optic long period grating (LPG) sensor with silver paste to realize a reflection mode operation is presented here. LPGs have higher sensitivity compared to fiber Bragg grating (FBG) and are typically used as a transmission sensor. Recently, reflective LPG structures have been realized by coating the end of the LPG fiber with metal, but they have limitations as the fabrication process to coat the fiber with metal is either expensive or complex. In our work, we show a novel inexpensive technique to coat long lengths (60 cm or longer) of LPG with silver. The fabricated reflective LPG mimics the transmitted spectrum with improved selectivity. This simple coating method can be applied for other optical fiber sensors; such as metal embedded sensors for monitoring parameters at such critical locations not accessible to ordinary sensors.
N. Tîmneanu, B. Iwan, J. Andreasson, M. Bergh, M. Seibert, C. Bostedt, S. Schorb, H. Thomas, D. Rupp, T. Gorkhover, M. Adolph, T. Möller, A. Helal, K. Hoffmann, N. Kandadai, J. Keto, T. Ditmire
Understanding the ultrafast dynamics of matter under extreme conditions is relevant for structural studies and plasma physics with X-ray lasers. We used the pulses from free-electron lasers (FLASH in Hamburg and LCLS in Stanford) to trigger X-ray induced explosions in atomic atoms (Xe) and molecular clusters (CH4 and CD4). The explosion dynamics depends on cluster size and the intensity of the X-ray pulse, and a transition from Coulomb explosion to hydrodynamic expansion is expected with increasing size and increasing pulse intensity. In methane clusters experiments at FLASH, the time-of-flight spectrometry shows the appearance of molecular adducts which are the result of molecular recombination between ions and molecules. The recombination depends on the cluster size and the expansion mechanism and becomes significant in larger clusters. In Xenon cluster experiments at the LCLS, measurements of the ion charge states in clusters suggest a formation of Xe nanoplasma which expands hydrodynamically. The dominance of low charge states of Xe is due to three-body recombination processes involving electron and Xe ions, and it depends on the X-ray intensity and nanoplasma formation.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.