京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第19096号 / エネ博第320号 / 新制||エネ||65(附属図書館) / 32047 / 京都大学大学院エネルギー科学研究科エネルギー応用科学専攻 / (主査)教授 松田 一成, 教授 岸本 泰明, 教授 大垣 英明 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

<p>Thermal radiation, an omnipresent phenomenon characterized by electromagnetic wave emission from objects above absolute zero, has consistently intrigued scientific exploration throughout history and profoundly influences various technological applications. Traditionally, the primary utilization of thermal radiation has been limited to fields such as lighting, cooling, and energy harvesting. However, the true potential of thermal radiation extends far beyond these energy-oriented applications. Every object imprints a unique signature within its emitted thermal radiation. These signatures, distinguished by their wide-ranging spectral and polarimetric characteristics, represent a rich information source about the emitting objects. The goal of this dissertation is to offer novel prospective and platforms to expand our perception and utilization of the spectral and polarimetric attributes of thermal radiation. It seeks to augment the conventional understanding of thermal radiation as merely an energy source, underlining its immense potential as an information carrier.</p> <p>This dissertation explores the spectral and polarimetric features left within the thermal radiation and how these features can be manipulated. The research uncovers that the macroscopic spectral, spatial, and particularly spin properties of thermal radiation are intimately connected to the underlying symmetry of the microscopic emitters within a nanophotonic system. This close relationship between symmetry and thermal radiation introduces a universal strategy to gain thorough control over the spectral-polarimetric properties of thermal radiation. The control of these properties may spur pioneering developments in encoding information within thermal radiation.</p> <p>Furthermore, platforms to decode these spectral and polarimetric properties in thermal radiation are as pivotal as the encoding platforms. These decoding platforms allow us to uncover hidden messages within this invisible light and enable us to push the boundaries of fully passive and physics-aware machine perception. Nevertheless, contemporary methods for spectrum and polarization resolved detection of thermal radiation, especially in imaging form, are cumbersome, lacking robustness, and prohibitively expensive. Hence, this dissertation explores two fundamentally innovative spectral separation schemes: the nonlocal super-dispersion enabled by optically active crystals and the dispersive dichroism in 2D infrared metasurfaces. These methods present compact, cost-effective, and high-performance solutions for spectral-polarimetric thermal imaging, thereby enhancing its efficacy in diverse applications.</p>

Non-reciprocal wave transmission is a phenomenon witnessed in certain photonic devices when the wave propagation dynamics through the device along one direction differs greatly from the dynamics along the counter-propagating direction. Specifically, it refers to significant power transfer occurring in one direction, and greatly reduced power transfer in the opposite direction. The resulting effect is to isolate the directionality of wave propagation, allowing transmission to occur along one direction only. Given the popularity of photonic integrated circuits (PIC), in which all the optical components are fabricated on the same chip so that the entire optical system can be made more compact, it is desirable to have an easily integrated optical isolator. Common free-space optical isolator designs, which rely on the Faraday effect, are limited by the availability of suitable magnetic materials. This research proposes a novel integrated optical isolator based on an array of closely spaced, identical waveguides. Because of the nonlinear optical properties of the material, this device exploits the differing behaviors of such an array when illuminated with either a high power or a low power beam to achieve non-reciprocal wave transmission in the forwards and backwards directions, respectively. The switching can be controlled electro-optically via an integrated gain section which provides optical amplification before the input to the array. The design, fabrication, characterization and testing of this optical isolator are covered in this dissertation. We study the switching dynamics of this device and present its optimum operating conditions.

Conjugated polymers represent a class of semi-conducting materials with numerous applications in optoelectronic devices, including organic light-emitting diodes, field-effect transistors, and photovoltaics. Because of the numerous advantages of macromolecular systems, including solution processing and mechanical flexibility, conjugated polymers have become a burgeoning field of research with the hopes of producing cost-effective solution-based electronics. Importantly, optoelectronic device performance is heavily influenced by conjugated polymer backbone orientation and overall thin film morphology. As such, the processing conditions of these systems are important to the construction of high- performance optoelectronics. Polythiophenes are model conjugated polymers that have been studied extensively in halogenated organic solvents. However, the self- assembly of these systems from dilute solution to the solid state remains ambiguous for solvents with high dielectric constants. Here, two derivative compounds of poly(3-hexylthiophene) are correspondingly investigated in high dielectric solvents by way of ultraviolet-visible absorption and fluorescence spectroscopy, Fourier transform infrared spectroscopy, small-angle X-ray scattering, polarized optical microscopy, and four- point probe conductivity measurements. In dilute solutions, both systems are found to undergo self-assembly when exposed to various stimuli, including temperature, solvent composition, and side-chain characteristics. The kinetics of these transitions are investigated, and a model is put forth to explain contrasting self-assembly mechanisms. At higher concentrations, both systems form lyotropic liquid crystalline phases. Characteristics of the liquid crystalline phases are found to be heavily influenced by dilute solution self-assembly mechanisms and processing. Through the application of a mechanical shear force along still-wet liquid crystal films, alignment of the polythiophene long axis is attained. This morphological characteristic is found to carry over to the solid-state for both systems, and clear optoelectronic anisotropy of the thin films is observed. As such, these methodologies may provide a route to the production of environmentally friendly high-performance optoelectronic devices.

In recent years, there has been significant progress in the development of integrated photonic circuits (PICs). Matured fabrication and simulation techniques have enabled the development of novel devices and system architectures. Ideally, these newly developed technologies are put to test in the lab, both to verify that they perform as simulated and to demonstrate the viability of the technology. Testing the increasingly complex optical circuits brings various challenges. One of these challenges is the sensitivity to temperature changes of many optical circuits, especially micro ring and micro disk resonators (MRRs and MDRs). Due to the nature of these resonators, slight deviations in the material properties have a large impact on their resonant frequency. Despite this, their small footprint and wavelength selectivity makes them promising components for many future technologies, especially Dense Wavelength Division Multiplexed (DWDM) communication links. Multiple resonators cascaded on a single bus waveguide can operate on multiple wavelengths simultaneously with relatively few components and in a small combined area. Since every extra connection to a PIC has a footprint similar to that of a micro resonator, a packaging optimized thermal control scheme is needed to fully leverage all advantages of micro resonators. This work will focus on the thermal stabilization of cascaded micro resonators and how thermal control can be optimized to simplify the packaging of PIC prototypes. This simplification enables the demonstration of complex systems and more realistic scenarios for thermal control of both resonators and other circuits. It will first show how a number of PICs and their respective packages were built, keeping subsequent testing in mind. Then, it demonstrates automatic initialization of cascaded MRR and how stable operation, while undergoing large temperature swings, can be achieved using a minimum number of connections to the PIC. Next, it shows stable operation of an eight-wavelength receiver, operating uncooled at 16 Gb/s/?, over a record 75 °C. Finally, it presents how all the learned lessons are brought together to built a 2.5D integrated SiPh transceiver that is capable of transmitting 512 Gb/s bidirectionally. This transceiver can be plugged into Field Programmable Gate Arrays (FPGAs), which can then be used to implement accelerators for real computing problems, used as a PCIe bridge to a standard compute server, or both. The transceiver is also designed to work with many types of optical switches, allowing demonstrations of novel switching algorithms and network architectures. The contributions discussed in this thesis can assist in enabling future high bandwidth optical interfaces by optimizing the thermal control strategy and may be used at all stages of PIC design and packaging to facilitate the development of new technologies.

No description available.

Colonoscopy is a necessary procedure to diagnose diseases in the lower gastrointestinal tract. Nevertheless, there exists a risk of bleeding during the colonoscopy, caused by perforations, diverticuli, post-biopsy complications, and polyps, which could go undetected as the camera is only equipped on the tip of colonoscope. A soft sensor, capable of detecting blood and distinguishing it from other GI fluids, has been developed using optical fibers for blood detection and data transmission. However, the sensor’s numerous optical fibers make it harder for the surgeon to hold and maneuver the colonoscope. In addition, the fibers are fragile and sensitive to external forces. This makes the sensor’s fabrication difficult and signal interpretation less reliable. Presented in this thesis is a wireless soft blood sensor utilizing deformable polymeric materials and microelectronic technologies. Opto-electronic components and a microcontroller installed on the flexible PCB allow the sensors to sense blood, recognize fluid types, account for the external forces, comply to bending of colonoscope, and wirelessly transmit data. The wireless data transmission is implemented by a millimeter-scale transmitter-receiver module. A Lithium ion battery powers the sensor. Without optical fibers, multiple blood sensors can be installed along the length of colonoscope. Consequently, this increases efficiency and reliability of blood detection while remaining safe for patients without interruption on the clinical workflow. / 2027-05-31T00:00:00Z

Experimental investigations of the optical properties of GaN nanostructured light emitting diode (LED) arrays are presented. Microphotoluminescence spectroscopy with pulsed and continuous wave lasers was used to probe the carrier dynamics and emission mechanisms of nanorod LED arrays fabricated by a top down etching method. Results show a possible reduction in internal electric field as nanorod diameter decreases. Localisation effects were also observed, affecting the spectral shape of the nanorod emission. Under two-photon excitation, quantum dot-like sharp spectral peaks in the PL spectra are found to exist in abundance amongst all the nanorod samples. The optical properties of these localised states, which are shown to be associated with the nanorod free-surfaces, are characterised using non-linear and time resolved spectroscopy. An investigation into spatially resolved single nanorods was also carried out. Single nanorods were isolated, and characterised using pulsed lasers. The etching is shown to increase the carrier decay life-time at extended intervals over several hundred ns. The temporal evolution and excitation power density dependence of the quantum dot-like states are also presented for the first time. The long lived localised states are thought to arise from surface effects, in particular Fermi-surface pinning, causing localisation and spatial separation of carriers. Additional work on nano-pyramid array LEDs, with quantum wells on semi-polar surfaces is also presented. Optical properties using micro-photoluminescence are compared to cathodoluminescence studies. An uneven distribution of emission wavelengths across the pyramid facet is thought to lead to an emission mechanism involving carriers transferring between multiple spatially localised states. Finally, experimental techniques and fabrication methods for future work are documented in detail.

Visible-light optical wireless communications (OWC) is a potential technology that can help resolve the crowdedness of the radio-frequency bands, whilst conveniently exploiting energy-saving light-emitting diodes (LEDs) as transmitters for both illumination and communications. Since there usually are many LEDs in a lighting unit, OWC has a multi- input multi-output (MIMO) geometry which, thanks to its channel diversity, can offer wireless local networks at data-rates many times higher than possible with single-channel systems. In such systems, MIMO-detection methods to separate the different optical channels play an important role in improving the system performance by helping reduce cross-talk between channels. To measure the performance of a particular geometry for MIMO communications, a simulation study, reported in this thesis, found that, amongst the signal- independent metrics, the condition number may be used as a rough predictor of the performance, whilst the channel Signal-to-Interference-and-Noise Ratio (SINR) is the most appropriate for geometry assessment. Combined with the fact that the overall performance of a MIMO system is mostly dominated by its worst channel, this indicates that the most effective way to improve the system performance is to maximise the worst channel’s SINR. One of the possible solutions to improving the SINRs is to use holograms to steer the transmitter images such that their distributions over the photo-detectors reduce overlaps. As LEDs emit partially-coherent light, the beam steering has to be carried out with partially- coherent illumination. By using two lenses to parallelise and collect partially-coherent light before and after the hologram, respectively, the source and image intensity distributions, and the autocorrelation of the hologram can be related in a succinct mathematical relationship. This leads to the development of three computational algorithms based on the autocorrelation function to obtain a quantised hologram with the desired beam-steering capability. These algorithms have their cost functions and performance comparison done at the hologram plane instead of the image plane, which therefore takes less time than traditional image-based methods. Specifically, one of these algorithms is able to save significant time over both the other autocorrelation-based algorithms and the direct binary-search, by 33% and by 50% respectively. A simulation-based study and a corresponding experiment, both reported in this thesis, found that the one of the proposed algorithms had poor power efficiency, whilst the other two were both highly effective in generating digital holograms with precise and power-efficient beam-steering performance. Of these two algorithms, one had superior time performance and was likely the best of the three proposed autocorrelation-based algorithms for generating beam-steering holograms. MIMO-OWC simulation also demonstrated the capability of using beam-steering holograms to design the channel and improve the system performance. Combining reported findings, a strategy can be devised to optimise the throughput of an imaging MIMO-OWC system for a given transmitted power.

台灣發展光電產業近20年，已有舉世注目之成績。就在這同一階段，台灣創業投資產業也有超過新台幣1,700億元資金，投資於國內高科技產業中，其規模之大，全球排名第二，僅次於美國，此一成就是值得國人引以為傲的。 由於產業西進的風潮方興未艾，不久「新世代」的光電產業終將會繼電子產業，成為根留台灣的主流產業。未來兩岸分工、大陸本土廠商崛起、加上韓國廠商大幅投入，光電產業整體經營環境必然大不同於從前。相對之下，未來創業投資投資光電產業，有賴更明確之投資策略。 因此，本研究著重於研究過去光電產業與創投產業間的互動關係，蒐集並分析：（1）台灣創業投資公司投資光電產業所採之「一般策略」、（2）投資光電產業「成功」之關鍵性策略行為、（3）投資光電產業「失敗」之關鍵性策略行為；再綜合分析投資光電產業影響「成敗」之共通關鍵性策略。最後，總結分析「光電產業特性」與「影響投資光電產業成敗關鍵性策略」間之互動關係。 結尾，對未來光電產業發展趨勢加以推估，概略建議未來創投投資「新世代」台灣光電產業可採之關鍵性策略，期望對國內光電產業發展及創投未來投資台灣光電產業「成功」，能有所助益。 / There are almost 20 years for Taiwanese to develop optoelectronics industry. Its outcome is the annual production value will over 1 trillion NTDs in the coming year, and it is rated No. 3 in the world. During the same period, the venture capital was also under developed. Right now, there are over 240 venture capital management companies in Taiwan, and have invested over 170 billion NTDs in high technology industry, the investment scale is also highly ranked, No.2 in the world. It is interested to know the relationship between Taiwan optoelectronics industry and venture capital. This paper is concentrated on the the Taiwanese venture capital investment strategies on Taiwan optoelectronics industry. And to find out what is the KSFs ( Key Success Factors ) of venture capital investment strategies, also the KFFs ( Key Failure Factors). And to analysis the relationship between KSFs& KFFs, to find the real key factors cause investment success or fail . The development situation of Taiwan optoelectronics industry is also discussed during the analysis of the factors, in order to find out the relationship between Taiwan optoelectronics industry situations and venture capital investment strategies. Finally, to figure out what will be the future Taiwan optoelectronics industry looks like, and with the results from the above study to suggest what will be the best practices to do venture capital investment successfully in the coming years on Taiwan optoelectronics industry.