Defects and impurities in colloidal Ga2O3 nanocrystals: new opportunities for photonics and lighting

Defects, both native and extrinsic, critically determine functional properties of metal oxides. Gallium oxide has recently gained significant attention for its promise in microelectronics, owing to the unique combination of conductivity and high breakdown voltage, and solid-state lighting, owing to the strong photoluminescence in the visible spectral region. These properties are associated with the presence of native defects that can form both donor and acceptor states in Ga2O3. Recently, Ga2O3 nanocrystal synthesis in solution and optical glasses has been developed, allowing for a range of new applications in photonics, lighting, and photocatalysis. This review focuses on the structure and properties of Ga2O3 nanocrystals with a particular emphasis on the electronic structure and interaction of defects in reduced dimensions and their role in the observed photoluminescence properties. In addition to native defects, the effect of selected external impurities, including lanthanide and aliovalent dopants, and alloying on the emission properties of Ga2O3 nanocrystals are also discussed.

Crack Forms Sensitivity-Based Prediction on Subsurface Cracks Depth in Ultrasonic-Vibration-Assisted Grinding of Optical Glasses

Subsurface cracks in ultrasonic-vibration-assisted grinding (UVAG) of optical glasses often exhibit diverse forms and proportions. Due to the variety of loads involved in crack formation and propagation, the crack forms and propagation depths have different sensitivities to each process parameter. Predicting the maximum subsurface cracks depth (MSSCD) by considering the varying effects of process parameters plays a key role in implementing effective control of the UVAG process. In this work, the subsurface crack forms and their proportions are investigated by conducting 40 sets of UVAG experiments. The varying effects of the grinding and ultrasonic parameters on the crack form proportions are unveiled by using grey relational analysis. The weighted least square support vector machine (WLS-SVM) prediction model for the MSSCD was developed. Twelve sets of UVAG experiments were carried out to validate the proposed model. The results show that arc-shaped cracks and bifurcated cracks account for 72.5% of all cracks, while ultrasonic vibration amplitude influences most of the proportions of arc-shaped and bifurcated cracks. Compared to other widely used prediction methods, the maximum and average relative prediction errors of the proposed model are 10.54% and 5.59%, respectively, which proves the high prediction accuracy of the model.

Features of meridional separable visual acuity changes in amblyopia treatment by accommodation training method in patients with astigmatism

Objective. To investigate the influence of the optic-reflex method of accommodation training on the indices of the meridional separable visual acuity in the treatment of children with amblyopia and astigmatism. Material and methods. 24 children aged 5 to 12 years with refractive amblyopia and direct hyperopic astigmatism were examined. Accommodation training was performed by defocusing the image with optical glasses of variable optical power. The course of treatment lasted 10 days. Results. In the group with meridional amblyopia, 2 different clusters were identified: in one of them, the indicators of separable visual acuity were higher in the horizontal meridian and in the other - in the vertical. After treatment, the number of eyes with the same meridional visual acuity increased. Simultaneously with the elimination of the meridional asymmetry of visual acuity, the number of eyes in the category of patients with visual acuity of 0.75-0.8 according to the Sivtsev table increased by 8.52%. Conclusion. In the standard of assessment of visual functions in patients with astigmatism and amblyopia, it is necessary to introduce methods for determining the meridional visual acuity. Evaluation of the effectiveness of treatment of meridional amblyopia should be carried out in homogeneous clusters, which take into account the coincidence or discrepancy of the directions of meridional asymmetries of visual acuity with refractive. Preliminary data on the effectiveness of treatment of amblyopia by the method of accommodation training allows us to consider it as a method of treatment of meridional amblyopia.

Method of Forming Microchannels on the Surface of a Glass Substrate

A method of forming arbitrarily shaped microchannels on substrates of brittle dielectric materials, such as optical glasses and optical crystals, is considered. This method makes it possible to ensure the identity of microchannel edges over the entire perimeter

Refractive Index Measurement of Glass with Arbitrary Shape Based on Brewster’s Law and a Focusing Probe Beam

The refractive index is one of the most important parameters of optical glasses and has a significant effect on optical properties. The measurement of optical glasses, especially for optical elements such as lenses, is urgently needed. However, several presented methods require the immersion of the sample in liquid and provide indirect measurements, while others require structural parameters as priori knowledge, which is complex and time-consuming. In this study, a Brewster-Law-based direct and simple measurement method for the refractive index of glasses with arbitrary shapes is proposed, and a laser beam is focused on the surface of the sample as a probe. The incident angle of the chief ray is close to the Brewster angle. The reflected light is collected by an array detector. The refractive index is calculated from the minimum intensity position obtained with image processing. Additionally, a symmetric measurement scheme is proposed to improve the accuracy. Using these methods, a prism and four spherical lens samples with different refractive indices or radii of curvature are tested and error analyses are carried out. Results indicate that the accuracy can reach 10−4.