A Finite Element Mesh Regrouping Strategy-Based Hybrid Light Transport Model for Enhancing the Efficiency and Accuracy of XLCT

X-ray luminescence computed tomography (XLCT) is an emerging hybrid imaging modality in optical molecular imaging, which has attracted more attention and has been widely studied. In XLCT, the accuracy and operational efficiency of an optical transmission model play a decisive role in the rapid and accurate reconstruction of light sources. For simulation of optical transmission characteristics in XLCT, considering the limitations of the diffusion equation (DE) and the time and memory costs of simplified spherical harmonic approximation equation (SPN), a hybrid light transport model needs to be built. DE and SPN models are first-order and higher-order approximations of RTE, respectively. Due to the discontinuity of the regions using the DE and SPN models and the inconsistencies of the system matrix dimensions constructed by the two models in the solving process, the system matrix construction of a hybrid light transmission model is a problem to be solved. We provided a new finite element mesh regrouping strategy-based hybrid light transport model for XLCT. Firstly, based on the finite element mesh regrouping strategy, two separate meshes can be obtained. Thus, for DE and SPN models, the system matrixes and source weight matrixes can be calculated separately in two respective mesh systems. Meanwhile, some parallel computation strategy can be combined with finite element mesh regrouping strategy to further save the system matrix calculation time. Then, the two system matrixes with different dimensions were coupled though repeated nodes were processed according to the hybrid boundary conditions, the two meshes were combined into a regrouping mesh, and the hybrid optical transmission model was established. In addition, the proposed method can reduce the computational memory consumption than the previously proposed hybrid light transport model achieving good balance between computational accuracy and efficiency. The forward numerical simulation results showed that the proposed method had better transmission accuracy and achieved a balance between efficiency and accuracy. The reverse simulation results showed that the proposed method had superior location accuracy, morphological recovery capability, and image contrast capability in source reconstruction. In-vivo experiments verified the practicability and effectiveness of the proposed method.

TEMPERATURE DEPENDENCE OF OPTICAL TRANSMISSION OF GERMANIUM SINGLE CRYSTALS

Проведены исследования оптического пропускания в диапазоне длин волн 2 - 14 мкм монокристаллов германия, легированных донорными и акцепторными примесями (удельное сопротивление германия 1 - 3 Ом⋅см), в интервале температур от 86 К до 523 К. Рассчитаны значения коэффициентов ослабления α для исследуемых кристаллов; минимальные значения коэффициентов ослабления (0,0015 - 0,0231 см) в интервале температур от 86 К до 323 К характерны для монокристаллов германия, легированных сурьмой, в диапазоне 2 - 11 мкм. Исследования показали, что низкие значения α и коэффициента пропускания на длине волны 3,39 мкм для кристаллов Ge: Sb и Ge: Bi позволяют применять эти низкоомные кристаллы германия для газовых гелий-неоновых лазеров при температурах от 86 К до 323 К. Исследованы температурные изменения геометрии поверхности кристалла на наноразмерном уровне. Показано, что нагрев кристаллического германия приводит к увеличению диффузного отражения излучения от поверхности. Сделан вывод о возможности использования низкоомных кристаллов германия, легированных сурьмой, в качестве элементов инфракрасной оптики в интервале температур 86 - 373 К. In this work, we investigated optical transmission in the wavelength range of 2-14 μm of low-resistance germanium crystals (1 - 3 Ω⋅cm) doped with donor and acceptor impurities in the temperature range from 86 K to 523 K. The values of the attenuation coefficients for investigated crystals are obtained. Minimum attenuation coefficients α of 0,0015 - 00231 cm in the temperature range from 86 K to 323 K are characteristic for germanium single crystals doped with antimony in the range 2,1-11 μm. Studies have shown that the low values of α and the transmittance at a wavelength of 3,39 pm for Ge: Bi and Ge: Sb crystals make it possible to use these low-resistance germanium crystals for gas helium-neon lasers at temperatures from 86 K to 323 K. The temperature changes in the geometry of the crystal surface are investigated at the nanoscale level. It is shown that heating crystalline germanium leads to an increase in the diffuse reflection of radiation from the surface. The possibility of using the low-resistance germanium crystals doped with antimony as elements of infrared optics in the temperature range 86 - 373 K has been demonstrated.

Data Augmentation Algorithm Based on Generative Antagonism Networks (GAN) Model for Optical Transmission Networks (OTN)

OTN (Optical Transmission Networks) is one of the mainstream infrastructures over the ground-transmission networks, with the characteristics of large bandwidth, low delay, and high reliability. To ensure a stable working of OTN, it is necessary to preform high-level accurate functions of data traffic analysis, alarm prediction, and fault location. However, there is a serious problem for the implementation of these functions, caused by the shortage of available data but a rather-large amount of dirty data existed in OTN. In the view of current pretreatment, the extracted amount of effective data is very less, not enough to support machine learning. To solve this problem, this paper proposes a data augmentation algorithm based on deep learning. Specifically, Data Augmentation for Optical Transmission Networks under Multi-condition constraint (MVOTNDA) is designed based on GAN Mode with the demonstration of variable-length data augmentation method. Experimental results show that MVOTNDA has better performances than the traditional data augmentation algorithms.

Recent Progress in the Correlative Structured Illumination Microscopy

The super-resolution imaging technique of structured illumination microscopy (SIM) enables the mixing of high-frequency information into the optical transmission domain via light-source modulation, thus breaking the optical diffraction limit. Correlative SIM, which combines other techniques with SIM, offers more versatility or higher imaging resolution than traditional SIM. In this review, we first briefly introduce the imaging mechanism and development trends of conventional SIM. Then, the principles and recent developments of correlative SIM techniques are reviewed. Finally, the future development directions of SIM and its correlative microscopies are presented.

Growing of bulk β-(Al x Ga1-x )2O3 crystals from the melt by Czochralski method and investigation of their structural and optical properties

Bulk (Al x Ga1-x )2O3 crystals with an Al fraction x in the range from 0.0 to 0.23 were successfully grown by the Czochralski method. An increase in the band gap from 4.7 eV to 5.1 eV with the rise of the Al content was demonstrated by analyzing optical transmission spectra. The crystal quality of the obtained samples was controlled by X-ray diffractometry. The appearance of crystal`s mosaic blockness was found for the Al fraction x above 0.05.

Extraordinary optical transmission from a thin microcavity by macroscopic quantum effect

The macroscopic quantum effect is revealed to elaborate the extraordinary optical transmission (EOT) from a subwavelength thin microcavity based on the uncertainty property of the transmitted electromagnetic fields after the aperture. A critical radius is found in the thin microcavity under a certain incident electromagnetic wavelength. With the aperture radius varying, the transmitted field can be divided into three regimes: I. the macroscopic quantum regime when the aperture radius is less than the critical radius, in which the field edge effect occurs and EOT phenomenon is perfectly manifested; II. The wave-particle duality regime in the vicinity of the critical radius, in which the edge effect and diffraction phenomenon exist simultaneously; III. The wave regime when the aperture radius is greater than the critical radius, in which the near-field diffraction emerges. In addition, the influences of incident wavelength and microcavity thickness on EOT are also investigated. Our research have potential applications in advanced optical devices, such as light switch and optical manipulations.