Mode analysis and measurement of single-emitter blue diode lasers.

Recent developments in blue diode lasers have been hindered by the challenge of balancing high power with beam quality. Typically, high-power blue diode lasers exhibit low beam quality due to the output of multiple longitudinal and lateral modes. A promising solution to this problem is to control and shape the blue beam mode output from a single emitter. To achieve this, it is key to have full knowledge of the properties of the output mode under various conditions. In this paper, we explore the mode characteristics of an InGaN single-emitter laser diode that has a typical wavelength of 447 nm (wavelength range: 440-455 nm). We measure and analyze the near-field mode using the box model, finding that the near-field mode excited by the blue diode laser overlapped near the threshold current of 0.32 A. The p=2 order lateral mode of longitudinal mode groups 3 and 4 overlapped with the p=4 order mode of adjacent longitudinal mode groups. Through a Fourier transform of the near-field mode, we obtain the far-field mode and reveal a spatial law of mode distribution that is similar to the near-field mode. As the current is gradually increased and approaches the rated current of the laser diode, the near-field mode continuously has new longitudinal mode groups added to the long-wavelength side of the starting group. We observe an increase in the number of longitudinal mode groups and high-order lateral modes, leading to more mode overlaps. Additionally, we observe a gradual shift in the peak energy of the modes to the long-wavelength side. This study reveals the mode characteristics of broad-area blue diode lasers, providing crucial information to achieve high-quality laser beams in such systems.

Macular Morphologic and Microvascular Analysis in Pseudophakic Children with Previous Pediatric Cataract Using Optical Coherence Tomography Angiography.

INTRODUCTION: The macular morphologic and microvascular changes in children with pseudophakia after pediatric cataract surgery remain unknown. The aim of this study was to analyze macular morphologic and microvascular remodeling in children with pseudophakia after pediatric cataract surgery using optical coherence tomography angiography (OCTA). METHODS: Consecutive cases between December 1, 2018, and November 31, 2020 were recruited. Sixty-one participants (31 pseudophakic children and 30 healthy controls) met the inclusion criteria and were included for final analysis. OCTA was used to measure macular vascular density, the foveal avascular zone (FAZ), and macular thickness. The parameters were compared between pseudophakic and healthy eyes using binary logistic regression, with adjustment for the effect of refractive error, age, and axial length. RESULTS: Compared with normal eyes, a significantly reduced area of the FAZ (p = 0.042), increased superficial foveal vascular density (p = 0.033), and increased inner and outer foveal thickness (p = 0.034 and 0.029, respectively) were noted in pseudophakic eyes. The deep parafoveal vascular density was generally lower in eyes with cataracts (p ≤ 0.044). The inner foveal thickness was positively correlated with the superficial foveal vascular density (r = 0.889, p < 0.001) and negatively correlated with the area of the FAZ (r = -0.903, p < 0.001). The outer foveal thickness was positively correlated with the deep foveal vascular density (r = 0.399, p = 0.002). CONCLUSIONS: Morphological and microvascular remodeling in children with previous pediatric cataract indicates foveal underdevelopment. The underlying mechanism requires further investigation.

Dysfunctional Lens Index Serves as a Novel Surgery Decision-Maker for Age-Related Nuclear Cataracts.

Purpose: To study the correlations between subjective and objective cataract metrics with dysfunctional lens index. To investigate the potential of the DLI as a novel surgery decision-maker. Methods: In this prospective, cross-sectional study, we measured the dysfunctional lens index (DLI), Lens Opacities Classification System III nuclear opalescence (LOCS III NO) grading, preoperative corrected distance visual acuity (CDVA), objective scatter index (OSI) and Scheimpflug-based average lens density (ALD) in eyes with nuclear cataract. Eyes were classified as Surgical and Non-Surgical groups. Correlations among the DLI, OSI, ALD, LOCS III NO grading, and preoperative CDVA were analyzed. The receiver operating characteristic (ROC) curve analysis was performed for DLI, OSI, and CDVA to determine optimal cut-off values to separate between surgical and non-surgical cataracts. Results: The DLI showed the strongest correlation with the OSI (r= -0.712, P< .001), followed by LOCS III NO score (r= -0.661, P< .001), ALD (r= -0.596, P< .001) and preoperative CDVA (r= 0.563, P< .001). The area under ROC curves (AUCs) of the DLI, OSI and preoperative CDVA curve were 0.972, 0.912 and 0.844 (All P< .001), respectively. The DLI cut-off value of 5.7 implied higher levels of sensitivity (91.67%) and specificity (91.84%) than the OSI cut-off value of 2.9 and the CDVA cut-off value of 0.55 (sensitivity of 89.58% and 71.92%; specificity of 81.63% and 85.71%, respectively). Conclusion: The surgery criterion of DLI ≤ 5.7 behaved better than the surgery criterions of OSI ≥ 2.9 and preoperative CDVA ≤ 0.55 in discrimination between surgical and non-surgical nuclear cataracts.

Lens nuclear opacity quantitation with long-range swept-source optical coherence tomography: correlation to LOCS III and a Scheimpflug imaging-based grading system.

PURPOSE: To quantitate lens nuclear opacity using long-range swept-source optical coherence tomography (SS-OCT) images and to evaluate the correlation of this method to Lens Opacities Classification System III (LOCS III) and a Scheimpflug imaging-based grading system (Pentacam Nuclear Stage function; PNS). METHODS: This study enrolled 120 participants (120 eyes) with age-related nuclear cataracts. The best-corrected visual acuity (BCVA), LOCS III nuclear opalescence (NO) and nuclear colour (NC) were obtained. The nuclear density measured using PNS function (NDPNS) was recorded. Three successive series of long-range SS-OCT images were captured, and the nuclear region was analysed using ImageJ (NIH, Bethesda, Maryland, USA) to generate SS-OCT image-based nuclear density (NDSS-OCT). The repeatability of NDSS-OCT measurement was evaluated using within-subject coefficient of variation (CVw) and intraclass correlation coefficient (ICC). Correlations of NDSS-OCT with NO and NC, BCVA and NDPNS were analysed. According to the integrity of nucleus imaged by Pentacam, patients were divided into two groups, and the parameters were compared between groups. RESULTS: The CVw and ICC for NDSS-OCT measurement were 1.5 % and 0.994, respectively. The NDSS-OCT significantly correlated with NO (r=0.831), NC (r=0.873), BCVA (r=0.655) and NDPNS (r=0.891). The NDSS-OCT, NO and NC, and BCVA were significantly different between the two groups. CONCLUSION: Lens nuclear opacity quantitation using long-range SS-OCT images was repeatable and correlated well with LOCS III and PNS function. The Scheimpflug principle had a limitation in imaging dense nucleus. Long-range SS-OCT seems more promising for objectively and quantitatively assessing lens nuclear opacity.