Three transducers for one photodetector: essays for optical communications

Dissertation presented to obtain the PhD degree in Electrical and Computer Engineering - ElectronicsOptical processing devices based on a- SiC:H multilayer architectures are expected to become reconfigurable to perform WDM optoelectronic logic functions and provide as well complex photonic functions such as signal amplification and switching. This thesis, entitled ”Three Transducers for One Photodetector: essays for optical communications”, reports the main work areas to design, control, validate and evaluate the research of a voltage-controllable wavelength selective optical switching based on shifting between positive and negative electrically bias and a photodetector, which enables the filtering function with the detector itself and has the potential to be rapidly optically biasing tuned: System Architecture – In this work area it is defined the basic requirements of the device: light-to-dark sensitivity, colour recognition, selective optical and electrical output response, amplification and opto-electronic conversion to transmit, receive, and/or process intelligence(data).The output multiplexed signals should have a strong nonlinear dependence on the light absorption profile, i.e., on the incident light wavelength, bit rate and intensity under unbalanced light generation of carriers. Experimental Design – This test activities work area allows the evaluation of the results. Multiple monochromatic pulsed communication channels were transmitted together, each one with a specific bit sequence. The combined optical signal was analyzed by reading out, under different applied voltages and optical bias, the generated photocurrent across the device. Depending on the wavelength of the external background and irradiation side, it acts either as a short- or a long- pass band filter or as a band-stop filter Optoelectronic Algorithm Interface – To help improve our understanding of the output multiplexed signal, computer models of monolithic photodetectors are developed. Following control theoretic methods we derive state-space representation and an equivalent circuit optoelectronic simulator. We validate each model and calibrate the spectral gain model by background–probe experiments and truth tables lookup that perform 8-to-1 multiplexer (MUX) and 1-to-8 demultiplexer (DEMUX) functions. Applications – The purpose of this work area is to present a new optical logic architecture that offers considerable improvements in reconfigurability. Tunable WDM converters based on amorphous SiC multilayer photonic active filters are used to build blocks to perform standard digital system operations. The transducers combine the simultaneous demultiplexing operation with the photodetection and self amplification. They are optimized for provide the high-sensitivity needed for low-light applications, such as medicine, lighting, sensing and measurement, and manufacturing. The migration to next generation packet based networks can be much easier and smoother than previously thought, using the emerging a-Si solutions and its integration with plastic optical fiber. It will push the limits of functionality, cost/performance and integration level

Reconfigurable photonic logic architecture

The amorphous silicon photo-sensor studied in this thesis, is a double pin structure (p(a-SiC:H)-i’(a-SiC:H)-n(a-SiC:H)-p(a-SiC:H)-i(a-Si:H)-n(a-Si:H)) sandwiched between two transparent contacts deposited over transparent glass thus with the possibility of illumination on both sides, responding to wave-lengths from the ultra-violet, visible to the near infrared range. The frontal il-lumination surface, glass side, is used for light signal inputs. Both surfaces are used for optical bias, which changes the dynamic characteristics of the photo-sensor resulting in different outputs for the same input. Experimental studies were made with the photo-sensor to evaluate its applicability in multiplexing and demultiplexing several data communication channels. The digital light sig-nal was defined to implement simple logical operations like the NOT, AND, OR, and complex like the XOR, MAJ, full-adder and memory effect. A pro-grammable pattern emission system was built and also those for the validation and recovery of the obtained signals. This photo-sensor has applications in op-tical communications with several wavelengths, as a wavelength detector and to execute directly logical operations over digital light input signals

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 40)

Abstracts are provided for 181 patents and patent applications entered into the NASA scientific and technical information system during the period July 1991 through December 1991. Each entry consists of a citation, an abstract, and in most cases, a key illustration selected from the patent or patent application

Space station common module network topology and hardware development

Conceptual space station common module power management and distribution (SSM/PMAD) network layouts and detailed network evaluations were developed. Individual pieces of hardware to be developed for the SSM/PMAD test bed were identified. A technology assessment was developed to identify pieces of equipment requiring development effort. Equipment lists were developed from the previously selected network schematics. Additionally, functional requirements for the network equipment as well as other requirements which affected the suitability of specific items for use on the Space Station Program were identified. Assembly requirements were derived based on the SSM/PMAD developed requirements and on the selected SSM/PMAD network concepts. Basic requirements and simplified design block diagrams are included. DC remote power controllers were successfully integrated into the DC Marshall Space Flight Center breadboard. Two DC remote power controller (RPC) boards experienced mechanical failure of UES 706 stud-mounted diodes during mechanical installation of the boards into the system. These broken diodes caused input to output shorting of the RPC's. The UES 706 diodes were replaced on these RPC's which eliminated the problem. The DC RPC's as existing in the present breadboard configuration do not provide ground fault protection because the RPC was designed to only switch the hot side current. If ground fault protection were to be implemented, it would be necessary to design the system so the RPC switched both the hot and the return sides of power

Space Radiation and Impact on Instrumentation Technologies

Understanding the interactions of the Sun, Earth and other natural and man-made objects in the solar system with the space radiation environment is crucial for improving activities of humans on Earth and in space. An important component of understanding these interactions is their effects on the instrumentation required in the exploration of air and space. NASA's Glenn Research Center (GRC) fills the role of developing supporting technologies to enable improved instruments for space science missions, as well as improved instruments for aeronautics and ground-based applications. In this review, the space radiation environment and its effects are outlined, as well the impact it has on instrumentation and the technology that GRC is developing to improve performance for space science

Solar Photovoltaic IV Curve Tracer

The Solar Photovoltaic Current-Voltage (IV) Curve Tracer, sponsored by Cal Poly Professor Dale Dolan, characterizes solar array current vs. voltage curves for any given temperature and irradiance. The curve tracer is battery powered, and functions autonomously across loading conditions from short circuit to open load on any sub-450-watt solar array. The curve tracer supports separate data logging modes for both single cells and single modules to maximize data accuracy for each. For testing full strings of solar panels, up to 10 IV curves may be stored in persistent EEPROM memory. Stored data may be recalled later for output to a personal computer in comma separated value format. This completed project is designed to teach Cal Poly students about the operation and continued maintenance of any solar array operating within the previously outlined specs during related coursework. This project will allow students to observe the optimal operating point of solar arrays at any temperature, illuminance, and load to identify problems due to mismatch, shading, soiling, and other functional errors. In a laboratory setting, extreme conditions may be tested and characterized to ensure a panel provides enough power and functions at all expected limits The completed project could successfully characterize IV curves for single cells, record temperature, store 10 data sets, and output data in .csv format to a personal computer, in conjunction with working LCD and button interfaces. The irradiance sensor chosen was unfortunately not compatible with the chosen microcontroller, and Covid distancing gave little chance to test the device on full panels during the design stages. When the final project was tested on a full panel, it was not put in the correct mode for the high panel voltage, and the microcontroller was shorted. Future improvements would include overvoltage protection and a professionally manufactured PCB and chassis

Structurally integrated luminescence based oxygen sensors with Organic LED/ oxygen sensitive dye and PECVD grown thin film photodetectors

There have been increasing efforts for the development of compact and miniaturized oxygen sensor for various applications including multianalyte sensor and sensors with a reliable and accurate monitoring of oxygen concentration in controlled environments requiring measurements under low oxygen concentration. This work has been devoted to the development of structurally integrated luminescence quenching based sensors, the structure comprising of Organic Light Emitting Diode (OLED) as excitation source, oxygen sensitive dyes as the sensing element and PECVD based thin film photodiodes for detection. The whole structure can also be extended towards the development on flexible substrates.;The developed sensor is less cumbersome and bulky and easy to use compared to the existing sensors. The commonly used Clark electrode for measuring dissolved oxygen suffers from interference from the ambient, requires frequent maintenance and electrolyte change, and also consumes oxygen during the measurement resulting in a little inaccurate measurement and hence restricts the resolution of the sensor. In addition the whole set-up is very bulky, which further motivates the development of these luminescence-based sensors. Another advantage of these luminescence-based sensors is the ease of tunability of sensitivity for different oxygen levels merely by changing the sensor dye.;This work has been devoted mainly to the development of appropriate thin film, low temperature grown thin film photodiodes optimized for best possible performance of the whole sensor configuration. In addition the three component integration issues were solved by overcoming all the challenges due to electromagnetic noise generated by the OLED, interfering with the photodiode response and hence limiting the sensitivity.;Amorphous silicon/silicon germanium and nanocrystalline silicon thin films were characterized for better performance in photodiodes. The sensitivity spectrums of the photodiodes were engineered to have maximum sensitivity around 640nm and minimum around 535nm, which is the peak emission wavelength of OLED. This process development resulted in enhanced immunity of the photodiode to the background resulting in enhanced sensitivity.;Two types of detection modes were used: intensity monitoring and PL lifetime monitoring mode. In the intensity mode, the reduction of the PL intensity in presence of oxygen due to quenching effects was monitored. The oxygen sensitive film partially absorbs the OLED light at 535 nm and then it emits at around 640 nm. Two filters were used, one bandpass on top of OLED to reduce the background tail emission followed by the sensor film and then a longpass filter to stop any unabsorbed OLED light. Sensor dyes films were either platinum or palladium based (PtOEP or PdOEP) respectively. A lock-in amplifier was used, to reduce the noise during detection and hence enhancing the sensitivity. But the major challenges were the OLED tail extending to 650nm, which was solved by coumarene doping of the Alq3 based OLED resulting in narrower spectrum.;The photoluminescence lifetime of the sensor dye film also changes with higher oxygen concentration and thus provides an alternate method of oxygen monitoring. For the PL lifetime based technique, the OLED was pulsed and it was off during the measurement. This resulted in the possibility of elimination of the filters and hence further minimizing and simplifying the sensor configuration. At this point the frequency response of the photodetectors becomes very important and their response time becomes the major issue. Proper impedance matching of the detecting circuit is critical for fast operation of the photodetectors. The boron diffusion during growth was observed to dominantly affect the frequency response, which was partially solved by using nip structure instead of pin structure photodiode. Using nanocrystalline and development of quantum dot photodetectors with amorphous layer grain boundary passivation further improved the response speed. Absolute quantum efficiencies were improved for the detectors. The thin film photodiodes were grown using PECVD, using both ECR (Electron Cyclotron Resonance) and VHF (Very High Frequency) PECVD techniques