ABSTRACT
Based on pulsed DC sputter deposition of hydrogenated carbon, an absorber optical coating with maximized broadband infrared absorptance is reported. Enhanced broadband (2.5-20 µm) infrared absorptance (>90%) with reduced infrared reflection is achieved by combining a low-absorptance antireflective (hydrogenated carbon) overcoat with a broadband-absorptance carbon underlayer (nonhydrogenated). The infrared optical absorptance of sputter deposited carbon with incorporated hydrogen is reduced. As such, hydrogen flow optimization to minimize reflection loss, maximize broadband absorptance, and achieve stress balance is described. Application to complementary metal-oxide-semiconductor (CMOS) produced microelectromechanical systems (MEMS) thermopile device wafers is described. A 220% increase in thermopile output voltage is demonstrated, in agreement with modeled prediction.
ABSTRACT
This work presents the characterization of the optical and mechanical properties of thin films based on (T a 2 O 5)1-x (S i O 2)x mixed oxides deposited by microwave plasma assisted co-sputtering, including post-annealing treatments. The deposition of low mechanical loss materials (3×10-5) with a high refractive index (1.93) while maintaining low processing costs was achieved and the following trends were demonstrated: The energy band gap increased as the S i O 2 concentration was increased in the mixture, and the disorder constant decreased when the annealing temperatures increased. Annealing of the mixtures also showed positive effects to reduce the mechanical losses and the optical absorption. This demonstrates their potential as an alternative high-index material for optical coatings in gravitational wave detectors using a low-cost process.
ABSTRACT
Coating thermal noise (CTN) in amorphous coatings is a drawback hindering their application in precision experiments such as gravitational wave detectors (GWDs). Mirrors for GWDs are Bragg's reflectors consisting of a bilayer-based stack of high- and low-refractive-index materials showing high reflectivity and low CTN. In this paper, we report the characterization of morphological, structural, optical, and mechanical properties of high-index materials such as scandium sesquioxide and hafnium dioxide and a low-index material such as magnesium fluoride deposited by plasma ion-assisted electron beam evaporation. We also evaluate their properties under different annealing treatments and discuss their potential for GWDs.
ABSTRACT
Optical properties of low-temperature pulsed DC-sputter deposited ($ {\le} {70° {\rm C}}$≤70°C) hydrogenated carbon are presented. Increasing hydrogen incorporation into the sputter deposited carbon significantly decreases infrared optical absorption due to a decrease in deep absorptive states associated with dangling bonds. Hydrogen flow is optimized (hydrogen flow 3 sccm), achieving the best compromise between increased infrared transmittance and hardness for durable coating performance. Optical, environmental, and durability performance of pulsed DC-sputtered carbon incorporated in multilayer (a-C:H/Ge) infrared antireflective coatings indicates suitability as a durable infrared optical coating for commonly used infrared substrates, including temperature sensitive chalcogenide glass.
ABSTRACT
BACKGROUND: In this work we describe a breath emulator system, used to simulate temporal characteristics of exhaled carbon dioxide (CO2) concentration waveform versus time simulating how much CO2 is present at each phase of the human lung respiratory process. The system provides a method for testing capnometers incorporating fast response non-dispersive infrared (NDIR) CO2 gas sensing devices - in a clinical setting, capnography devices assess ventilation which is the CO2 movement in and out of the lungs. A mathematical model describing the waveform of the expired CO2 characteristic and influence of CO2 gas sensor noise factors and speed of response is presented and compared with measured and emulated data. OBJECTIVE: A range of emulated capnogram temporal waveforms indicative of normal and restricted respiratory function demonstrated. The system can provide controlled introduction of water vapour and/ or other gases, simulating the influence of water vapour in exhaled breath and presence of other gases in a clinical setting such as anaesthetic agents (eg N2O). This enables influence of water vapour and/ or other gases to be assessed and modelled in the performance of CO2 gas sensors incorporated into capnography systems. As such the breath emulator provides a means of controlled testing of capnometer CO2 gas sensors in a non-clinical setting, allowing device optimisation before use in a medical environment. METHODS: The breath emulator uses a unique combination of mass flow controllers, needle valves and a fast acting switchable pneumatic solenoid valve (FASV), used to controllably emulate exhaled CO2 temporal waveforms for normal and restricted respiratory function. Output data from the described emulator is compared with a mathematical model using a range of input parameters such as time constants associated with inhalation/ exhalation for different parts of the respiratory cycle and CO2 concentration levels. Sensor noise performance is modelled, taking into account input parameters such as sampling period, sensor temperature, sensing light throughput and pathlength. RESULTS: The system described here produces realistic human capnographic waveforms and has the capability to emulate various waveforms associated with chronic respiratory diseases and early stage detection of exacerbations. The system has the capability of diagnosing medical conditions through analysis of CO2 waveforms. Demonstrated in this work the emulator has been used to test NDIR gas sensor technology deployed in capnometer devices prior to formal clinical trialling.