Utilizing a Diffractive Focus Beam Shaper to Enhance Pattern Uniformity and Process Throughput during Direct Laser Interference Patterning

Uniform periodic microstructure formation over large areas is generally challenging in Direct Laser Interference Patterning (DLIP) due to the Gaussian laser beam intensity distribution inherent to most commercial laser sources. In this work, a diffractive fundamental beam-mode shaper (FBS) element is implemented in a four-beam DLIP optical setup to generate a square-shaped top-hat intensity distribution in the interference volume. The interference patterns produced by a standard configuration and the developed setup are measured and compared. In particular, the impact of both laser intensity distributions on process throughput as well as fill-factor is investigated by measuring the resulting microstructure height with height error over the structured surface. It is demonstrated that by utilizing top-hat-shaped interference patterns, it is possible to produce on average 44.8% deeper structures with up to 60% higher homogeneity at the same throughput. Moreover, the presented approach allows the production of microstructures with comparable height and homogeneity compared to the Gaussian intensity distribution with increased throughput of 53%.

Improved Classification Models to Distinguish Natural from Anthropic Oil Slicks in the Gulf of Mexico: Seasonality and Radarsat-2 Beam Mode Effects under a Machine Learning Approach

Distinguishing between natural and anthropic oil slicks is a challenging task, especially in the Gulf of Mexico, where these events can be simultaneously observed and recognized as seeps or spills. In this study, a powerful data analysis provided by machine learning (ML) methods was employed to develop, test, and implement a classification model (CM) to distinguish an oil slick source (OSS) as natural or anthropic. A robust database containing 4916 validated oil samples, detected using synthetic aperture radar (SAR), was employed for this task. Six ML algorithms were evaluated, including artificial neural networks (ANN), random forest (RF), decision trees (DT), naive Bayes (NB), linear discriminant analysis (LDA), and logistic regression (LR). Using RF, the global CM achieved a maximum accuracy value of 73.15. An innovative approach evaluated how external factors, such as seasonality, satellite configurations, and the synergy between them, limit or improve OSS predictions. To accomplish this, specific classification models (SCMs) were derived from the global ones (CMs), tuning the best algorithms and parameters according to different scenarios. Median accuracies revealed winter and spring to be the best seasons and ScanSAR Narrow B (SCNB) as the best beam mode. The maximum median accuracy to distinguish seeps from spills was achieved in winter using SCNB (83.05). Among the tested algorithms, RF was the most robust, with a better performance in 81% of the investigated scenarios. The accuracy increment provided by the well-fitted models may minimize the confusion between seeps and spills. This represents a concrete contribution to reducing economic and geologic risks derived from exploration activities in offshore areas. Additionally, from an operational standpoint, specific models support specialists to select the best SAR products and seasons for new acquisitions, as well as to optimize performances according to the available data.

Analyzing the Treatment Delivery Accuracy of the uRT Treatment Planning System and uRT-Linac 506C by Use of AAPM TG 119 Test Cases

ObjectiveThe objective of this study was to investigate accuracy of the United Imaging Healthcare's uRT treatment planning system (uRT-TPS), by creating AAPM TG 119 test plans with respectively IMRT and VMAT techniques by homogeneous and heterogeneous phantom. Materials and MethodsThe plans were delivered to the homogeneous and heterogeneous phantom using the United Imaging Healthcare's uRT-Linac 506C. The overall dose calculation accuracy by uRT-TPS with Collapsed Cone Convolution (CC) and Monte Carlo (MC) algorithm was measured and analyzed by creating IMRT and VMAT plans for the 5 test geometries specified in TG 119, by using two kinds of beams FF photon beam and FFF photon beam. The point doses were measured with a Farmer type ion chamber and the fluences were measured with films respectively. Results The result of position accuracy was shown that the worst position accuracy is 0.36 mm and the repeated positioning accuracy of MLC field location was less than 0.25mm. The symmetry deviation of MLC was less than 0.08mm. In this study, the CLs of sMLC, dMLC and VMAT plans with FF photon beams were 2.74%, 2.12%, and 1.36% respectively. As for FFF photon beams, they were 3.76%, 2.14% and 2.90% respectively, whereas the counterpart CL specified in TG119 were 4.5% for the high dose regions and 4.7% for OAR regions. The CLs of Gamma Passing rates for sMLC, dMLC and VMAT plans were 4.59%, 5.35% and 2.15% for FF beam mode, and were 1.82%, 6.12% and 4.82% for FFF beam mode. For the heterogeneous phantom, the maximum deviation is 2.35% for CC and 2.63% for MC algorithm respectively.Conclusion Based on this analysis which were performed in accordance with the TG 119 recommendations, it is evident that the URT treatment planning system and URT-Linac 506C have commissioned IMRT and VMAT techniques with adequate accuracy. and all uRT_TPS treatment plans were recognized as clinically acceptable.

A Gaussian Beam Mode Analysis Method for 3-D Multi-Reflector Quasi-Optical Systems

3-D quasi-optical systems have a more comprehensive range of application scenarios, and their analysis and design are more complicated than those of 2-D systems. In this work, we improve Gaussian beam mode analysis (GBMA) to analyze 3-D multi-reflector systems. The expressions of co- and cross-polarization and their derivations are given and discussed in detail. Furthermore, several 3-D dual-reflector systems with different rotation angles are chosen as simulation examples to assess the validity and precision of 3-D GBMA compared with physical optics (PO) in the commercial software GRASP10. Furthermore, a 3-D double ellipsoidal reflector system with a π/2 rotation angle operating at 183 GHz is designed, manufactured, and tested. Measured results of the system demonstrate that it is in good agreement with the simulated results of 3-D GBMA and PO for both the co- and cross-polarization. By comparing the computing time performance of 3-D GBMA and PO in GRASP10, the high efficiency of 3-D GBMA is clarified. With 3-D GBMA, the field in 3-D quasi-optical systems can be calculated preciously and rapidly.