Large-area mid-infrared broadband absorbers based on spiral ITO resulting from the combination of two different broadening absorption methods.

A large-area mid-infrared broadband absorber is proposed in this paper. The absorber is a spiral ITO structure grown on a hexagonal lattice arrangement of silicon nanopillars by using a glancing angle deposition method. The experimental results show that when the heights of the silicon nanopillars are 1.7 µm and the number of rotation depositions is n = 5, that is, the rotation angle is 150 degrees, the absorber absorbs more than 81% of electromagnetic waves in the 2.5-6 µm spectral range. In the atmospheric window of 3-5 µm, the integral absorption reaches 96%. The experimental results also show that the absorbing ability of the ITO structure in the mid-infrared atmospheric window is significantly stronger than that of the structure composed of silver under the same preparation conditions. The main reasons for the broadband absorption are that the spiral ITO structure has resonant absorption of electromagnetic waves with different wavelengths in the empty cavity regions with different sizes, and ITO has longer penetration depths than noble metals in the mid-infrared band, which brings about stronger broadband absorption. The combination of the two leads to a broadening of the total absorption spectrum. The higher heights of the silicon nanopillars enhance absorption further. Additionally, the loose spiral ITO distributions indicate lower mean plasma concentration and then increase penetration depths further, resulting in stronger light absorption. Such a large-area mid-infrared absorption structure with a simple preparation method has potential applications in mid-infrared cloaking and sensing.

A novel diagnostic method for pituitary adenoma based on magnetic resonance imaging using a convolutional neural network.

PURPOSE: This study was designed to develop a computer-aided diagnosis (CAD) system based on a convolutional neural network (CNN) to diagnose patients with pituitary tumors. METHODS: We included adult patients clinically diagnosed with pituitary adenoma (pituitary adenoma group), or adult individuals without pituitary adenoma (control group). After pre-processing, all the MRI data were randomly divided into training or testing datasets in a ratio of 8:2 to create or evaluate the CNN model. Multiple CNNs with the same structure were applied for different types of MR images respectively, and a comprehensive diagnosis was performed based on the classification results of different types of MR images using an equal-weighted majority voting strategy. Finally, we assessed the diagnostic performance of the CAD system by accuracy, sensitivity, specificity, positive predictive value, and F1 score. RESULTS: We enrolled 149 participants with 796 MR images and adopted the data augmentation technology to create 7960 new images. The proposed CAD method showed remarkable diagnostic performance with an overall accuracy of 91.02%, sensitivity of 92.27%, specificity of 75.70%, positive predictive value of 93.45%, and F1-score of 92.67% in separate MRI type. In the comprehensive diagnosis, the CAD achieved better performance with accuracy, sensitivity, and specificity of 96.97%, 94.44%, and 100%, respectively. CONCLUSION: The CAD system could accurately diagnose patients with pituitary tumors based on MR images. Further, we will improve this CAD system by augmenting the amount of dataset and evaluate its performance by external dataset.

L-shaped ITO structures fabricated by oblique angle deposition technique for mid-infrared circular dichroism.

This paper proposes a mid-infrared chiral structure, which consists of L-shaped indium tin oxide (ITO) films formed on self-assembled monolayer polystyrene microspheres in two orthogonal directions by oblique angle deposition technique. Experimental results demonstrate that the structure exhibit circular dichroism (CD) responses in the range of 2.5 - 4 µm. As the thickness difference of the ITO films in the two orthogonal directions increases, the CD response enhances. The reason is that the ITO films produce cross dipoles and their bigger differences in thickness bring to bigger phase differences in optical chirality. The experimental results also demonstrate that the CD signals are evidently stronger than those of the structure consisting of silver in the mid-infrared band. This work provides a new idea for the fabrication of mid-infrared chiral structures, which have potential applications in the polarization state control of mid-infrared lasers.