• Journals

Photoluminescence properties of B-γ CsSnI_3 films and α-CsSnBr_3 microstructures synthesized by chemical vapor deposition

In recent years, B-γ CsSnI_3 and α-CsSnBr_3 perovskites have been applied in various optoelectronic devices due to their favorable physical properties, such as high defect tolerance, low toxicity, and impressive thermal stability. In this dissertation, the photoluminescence properties of B-γ CsSnI_3 films and α-CsSnBr_3 microsquares and micropyramids synthesized by chemical vapor deposition are explored. There are two parts in this dissertation. The first part focuses on the properties of B-γ CsSnI_3 random laser. The near-infrared lasing emission from B-γ CsSnI_3 films is observed as excitation fluence is above 18 mJ/cm^2. Through lasing spectra measured in different detected directions, the B-γ CsSnI_3 laser is classified as a random laser. In the second part, the photoluminescence properties and the thermal photoluminescence quenching of α-CsSnBr_3 microsquares and micropyramids are studied. Under two-photon excitation (940 nm), whispering-gallery modes and amplified spontaneous emission are found in microsquares and micropyramids, respectively. These results confirm that α-CsSnBr_3 microsquares and micropyramids are high-quality optical microcavities. Temperature-dependent photoluminescence measurements reveal that thermal photoluminescence quenching occurs in both microsquares and micropyramids. The photoluminescence intensity of both microstructures decreases with increasing temperature. By the Arrhenius equation, the estimated activation energy of thermal assisted nonradiative recombination for both α-CsSnBr_3 microsquares and micropyramids is over 310 meV which is greater than that for CsPbBr_3 (246 meV). These results suggest that α-CsSnBr_3 has the favorable resistance of thermal photoluminescence quenching.

• Journals

Quantifying Photoinduced Carriers Transport in Exciton-Polariton Coupling of MoS_2 Monolayers y

Strong-coupling take place when the energy exchange rate exceeds both cavity dissipation rate and emitter scattering rate. Upon achieving a strong-coupling regime, a new hybrid eigenstate is formed because of the energy difference-induced splitting of two polaritonic states. With the development of nanoscale optics and the demand for nanoscale optical applications, two-dimensional MoS_2 monolayers are promising candidates for a single emitter. However, less study on charge transfer in the coupling system at room temperature. In this project, we investigate photo-induced carrier transfer in 1D plasmonic nanogrooves (NG) array-2D MoS_2 hybrid system with Kelvin probe force microscopy (KPFM) surface potential nanoimaging. Our findings are an important basis to develop metal-2D semiconductor heterodevices.

• Journals

Development of a high-throughput Nonlinear Optical Mesoscope for rapid fresh digital pathology of whole-mount specimens

In this research, we first explore the consequences of the Nyquist-Shannon sampling theorem in the context of a laser-scanning nonlinear optical microscope (NLOM). A concept of Nyquist-figure-of-merit is introduced, and an aliasing-free mesoscale NLOM with a field-of-view (FOV) of >1 mm^2 is constructed while simultaneously fulfilling the respective Nyquist-Shannon criterion to digitally retrieve an optical resolution of <500 nm. Addressing the concern of poor-contrast neuronal imaging, we next introduce a GPU-accelerated real-time technique called denoised contrast enhancement (DCE). Subsequently, we introduce a sectioning-free intraoperative margin assessment (IMA) technique called True-H&E Rapid Fresh digital- Pathology (the-RFP) which is 4 times faster than the gold standard frozen-section (FS) biopsy. The-RFP is compatible with traditional hematoxylin and eosin (H&E) dyes, and thus does not require additional training. In this study, we apply the-RFP technique to investigate high-grade glioma specimens. A clinical trial involving 50 normal and tumor-specific specimens reveals an accuracy of 100%.

• Journals

FPGA-based Quantitative Differential Phase Contrast Microscopy for Live Cell-imaging optimized by Deep Learning

Quantitative phase imaging is becoming an important tool for biomedical research. It's a challenging task to obtaining accurate quantitative structural information for thin and transparent biological objects. Isotropic Quantitative Differential Phase Contrast Microscopy is a newly label-free optical imaging method. A typical qDPC microscopic imaging requires an optical setup with electronically controlled dynamic illumination and a phase retrieval algorithm for image reconstruction. To reconstruct a single-phase image, multiple intensity measurements are acquired and post processed. Here, we propose acompact FPGA-based qDPC microscopy module with high speed image acquisition. In addition to the development of FPGA-based qDPC microscope module, we implemented supervised deep learning methods for the single axis qDPC microscopy. Our trained model has potential to be directly integrated in FPGA-based qDPC module for high speed biomedical imaging. We performed initial studies related to observing the biological changes in COVIDinfected cells through the qDPC system. Our results show quantitative phase imaging performs better in evaluating the cell conditions in comparison to conventional bright field microscopy, and provide new directions for virus infected cell biological research.

• Journals

Investigation of HfZrO_2 Ferroelectric Thin-Film-Transistor Based on InGaZnO Channel

In this work, ferroelectric thin-film transistors (FeTFT) with metal-ferroelectric-metal-insulator-semiconductor (MFMIS) stack structure are demonstrated by monolithic integration of indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs) with ferroelectric HfZrO_2 (HZO) capacitors. Two device configurations are investigated: one is the offset configuration - no overlapping between the IGZO TFT and HZO capacitor, and the other is the vertically-stacked configuration - the IGZO TFT and HZO capacitor are overlapped. Various ratios between the area of ferroelectric capacitor (A_(FE)) and metal-insulator-semiconductor area in TFT (A_(DE)) are used, We investigate dependence of the anti-clockwise hysteresis memory window (MW) induced by ferroeletricity and the area ratio A_(DE)/ A_(FE) ratio. In both configurations, as area ratio A_(DE)/ A_(FE) is larger than 1/4, gate sweeping voltage with same range mainly drops on the insulator in transistor due to voltage divider rule, indicating that the effective voltage across the ferroelectric layer is insufficient to induce polarization switching. However, as area ratio A_(DE)/ A_(FE) becomes smaller than 1/4, an anti-clockwise hysteresis MW induced by ferroeletricity appears. The smaller the area ratio A_(DE)/ A_(FE), the larger the hysteresis MW. When the area ratio A_(DE)/ A_(FE) reaches 1/12, large hysteresis MW of 4.3 V are achieved. Also, the hysteresis MW shows a strong dependence on the area ratio A_(DE)/ A_(FE) but little dependence on the device configuration. Next, we choose the device with the area ratio A_(DE)/ A_(FE) is 1/12, due to larger MW, to measure memory properties such as endurance and retention measurement. The device can be successfully operated by program and erase pulses. For endurance measurement, by tuning the measurement setup of pulse amplitude, pulse width and drain voltage, the device can be operated over 10^5 cycles and achieved about 10^5 drain current (I_(DS)) on/off current ratio, which shows a great potential for memory applications.

• Journals

Bidirectional Fiber-FSO-5G NR MMW/Sub-THz Convergent System

Over the years, with the increasing require for 5G mobile communications and multimedia services, the amount of data transmission between telecom operators and users has increased, prompting the development of wireless networks towards higher data rates, lower latency and greater connections. However, since millimeter wave (MMW) and Sub-terahertz (Sub-THz) cannot perform the long-distance wireless communication, broadband convergent system with higher transmission capacity and long-distance transmission are very important. Utilizing the characteristics of high transmission capacity and low transmission loss of free-space optical (FSO) communication, combined with fiber broadband and 5G, a system is constructed to achieve long-distance transmission with high data rate and decrease the amount of 5G NR MMW/Sub-THz base stations. In this paper, the "Bidirectional Fiber-FSO-5G NR MMW/Sub-THz Convergent System," with x- and y-polarizations 40 Gbps 100 GHz 5G NR Sub-THz signals in the downlink transport, and 10 Gbps 28 GHz/24 GHz 5G MMW signals in the uplink transport. Using a orthogonally/parallel polarized dual-carrier mechanism, injection locking with a DFB LD and a phase modulators to realize this system. By realizing the bidirectional Fiber-FSO-5G NR integrated, that downlink and uplink transmission data rate and performance have been significantly improved. Over the 20 km single mode fiber, 500 m FSO, and 1 m/4 m RF wireless transmission, can achieve great BER performance and clear eye diagram.

• Journals

【論文摘要】具備隱私保護特性顯示器之設計及利用液晶摻雜二色性染料製作非對稱穿透式智慧窗

本論文研究主題為提供隱私保護之液晶光電元件，全文共分為三部分，第一部分針對智慧窗進行研究，提出利用二色性染料摻雜液晶製作非對稱穿透式智慧窗，將二色性染料摻雜於液晶中，以LED燈泡搭配不同波段之窄頻濾波片組合為室內光源；室外參考光源D65乃為一寬頻光源，透過寬頻室外光源與窄頻室內光源經染料吸收後之穿透光譜差異，達到非對稱穿透式智慧窗之效果。因實驗上無法達成理想之非對稱效果，同時利用程式進行數值模擬，設計不同室內光源及染料吸收光譜，且將室內參考光源訂為6500K及3000K，室外參考光源訂為D65，用以優化智慧窗系統達成理想之非對稱效果。本論文第二及第三部分係為隱私保護顯示器之研究，並將其細分為兩方向，其一為利用線性偏振光特性製作資訊保護液晶顯示器；其二為利用圓偏振光特性製作資訊保護顯示器。第二部分透過輸入隱藏資訊至反射式空間光調制器（reflective liquid crystal SLM，簡稱RLC-SLM），使其提供二分之一波板之功能以調制入射RLC-SLM之線偏振光，顯示隱藏資訊與未顯示隱藏資訊部分之反射光偏振態將互相正交，輔以檢偏器即可見隱藏資訊。此外，將RLC-SLM置於偏光顯微鏡下觀察，推斷實驗上未使用檢偏器即可見隱藏資訊之問題為畫素間液晶排列不同導致。第三部分分為實驗及畫素設計兩者，實驗上利用寬頻四分之一波板薄膜將出射顯示器之線偏振光調制為圓偏振光，並透過由寬頻四分之一波板薄膜與線偏振片組合之圓偏振片達成隱私保護之效果。畫素設計的部分，將兩畫素合併為一複合畫素，於其上黏貼兩快軸軸向相互正交之寬頻四分之一波板薄膜，使奇數與偶數行畫素出射圓偏振光之旋性相反，透過調整點亮奇數或偶數行畫素，並搭配前述之圓偏振片，即可達成隱私保護顯示器之效果。

• Journals

【論文摘要】連續譜中基於準束縛態的高品質因子生物感測器

隨著科技日新月異的發展，元件的尺寸逐漸精細化，因此奈米科學的發展備受矚目。而在奈米光學的領域中，超穎材料（metamaterials）時常被拿出來討論及應用，超穎材料是人工合成的複合材料，它們的特性來自內部微觀結構，以人工調整晶格常數和原子間的相互作用，透過調整結構的大小，週期以及排列的方式等，來達成有天然材料所不具備的物理性質和特別的電磁波特性。近年來，連續光譜中的束縛態（Bound States in the Continuum, BIC）的概念受到了注目，而透過結構的對稱性被破壞時而形成Q-BIC（quasi-BIC, Q-BIC）模態在光譜上可以到十分窄頻的共振，這種擁有高品質因子（quality factor）的共振特徵非常適合應用於生物感測器上。本論文研究工作於近紅外波段的奈米元件，基於在玻璃基板上設計具有非對稱性的週期性奈米陣列，並探討樣品在不同的環境折射率下所產生的共振位移特性，成功實現高靈敏度的BIC感測器。此結構由兩個不對稱的非晶矽（Amorphous silicon，a-Si）長方柱所組成，通過矽基不對稱奈米棒對的設計，激發了Q-BIC模態，在近紅外中顯示出占主導地位的環形偶極子（TD）和電四極子（EQ）共振特徵，並在局部環境的折射量測到具有超高靈敏度變化。根據實驗結果我們成功量測到藉由打破結構對稱性所激發的Q-BIC模態，更透過旋塗的方式成功量測到結構在三種不同的環境折射率下的共振位移量，在結構高度為450nm的納米棒對的測量（模擬）靈敏度和品質因數達到608nm/RIU和46（612nm/RIU和85）。本文從模擬計算深入探討結構基於不同的旋轉角度，高度與壁直所產生的影響，並探討藉由模擬增加材料損耗k時不同旋轉角度下的頻譜差異，最後再透過奈米微影技術將模擬設計的模型實做出來。本論文研究之連續譜中基於準束縛態的高品質因子生物感測器利用介電材料之奈米結構在穿透光譜中有特徵共振，隨著環境折射率不同而位移，造成穿透光譜中特徵共振位移及環境折射率改變之特性，故可應用於偵測氣體與液體之生物感測，亦或者可以利用radiation continuum中的BIC作為完美濾波器。