Barcode-structured YAG:Ce/YAG:Ce,Mn ceramic phosphors for variable CCT and high CRI LED/LD lighting.

Ceramic phosphors are widely considered the next-generation phosphor material for white LED/LD lighting, and a wide spectrum is a key factor in improving the CRI of lighting sources. In this paper, a novel, to our knowledge, barcode-structured YAG:Ce/YAG:Ce,Mn ceramic phosphor was designed and fabricated. The lighting sources with the CRI value of 73.5 and 68.9 were obtained under the excitation of blue LEDs and blue LDs, respectively. Simultaneously, thanks to the effective supplementary emission from a red LD, the CRI of the ceramic-based lighting source reached 81.8 under blue LD excitation. Specifically, the microstructure and luminescent property of ceramic phosphors with different thicknesses and ion doping concentrations were systematically studied. Besides, by changing the blue power from 0.52 W to 2.60 W, the CCT of the laser lighting source with the encapsulation of optimized YAG:Ce/YAG:Ce,Mn ceramic phosphors ranged from 3928 K to 5895 K, while the CRI always maintained above 80. The above results indicate that barcode-structured Ce:YAG/Ce,MnYAG ceramic phosphor is a candidate to achieve a high CRI and ican be applied to various lighting occasions.

Laminated structural Al2O3/YAG:Ce composite ceramic phosphor with high front light emission for transmissive laser lighting.

The realization of high front light emission in laser lighting under transmissive modes is heavily constrained by low thermal stability and light extraction efficiency of color converter materials. Therefore, it is necessary to improve the heat dissipation capacity and light utilization efficiency of the color converter through appropriate microstructural adjustments. In this study, what we believe to be a novel laminated structure consisting of Al2O3 and YAG:Ce was designed and fabricated for transmissive laser lighting. Through this design, it was possible to change the phosphor emission angle, overcoming the limitations of total internal reflection and enabling maximal emission of yellow phosphor from the ceramic surface. This laminated structure enhanced the front light emission efficiency by 24.4% compared to composite ceramic phosphor. In addition, the thermal conduction area between the phosphor layer and the heat dissipation layer have been effectively enhanced. Ultimately, under a high-power density of 47.6 W/mm2, all ceramics showed no luminous saturation threshold. A high-brightness front light with a luminous flux of 651 lm, a luminous efficiency of 144 lm/W, a correlated color temperature of 6419 K and the operating temperature as low as 84.9 °C was obtained. These results suggest that laminated structural Al2O3/YAG:Ce composite ceramic is a promising candidate for transmissive mode laser lighting.

Highly efficient Ce: Lu(Mg,Al)2(Si,Al)3O12 phosphor ceramics for high-power white LEDs/LDs.

Lu3Al5O12: Ce3+ (LuAG: Ce3+) phosphor ceramics (PCs) with high quantum efficiency and excellent thermal stability are incredibly promising color converters for high-power white light emitting diodes (LEDs)/ laser diodes (LDs) lighting. However, the greenish emission of LuAG:Ce3+ PCs does not allow to reach white light emission upon pumping by a blue LED/ LD without an additional red luminescent material. In this work, a series of (Ce0.003Lu0.997)3(MgxAl1-2xSix)5O12 (LCMASG) (x = 0-0.15) PCs were fabricated by solid state reaction method. Impressively, the as-prepared PCs exhibited a distinct red-shift (513→538nm) and a 17% increase of the color index (CRI) of high-power white LED(58.4→70.4). Particularly, Ce: Lu(Mg, Al)2(Si, Al)3O12 PC with 15 at.% substitution concentration showed only 8% luminescent intensity loss at 150 °C and high internal quantum efficiency (IQE) of 82%, exhibiting desirable optical thermal stability. By combining with a 460 nm blue chip or a 455 nm laser source, white LED/LD devices based on the LCMASG PCs in a remote excitation mode were constructed. The optimized luminous efficiency of Ce: Lu(Mg, Al)2(Si, Al)3O12 PC with 15 at.% Mg2+/Si4+ doping up to 176.4 lm/W was obtained as the power density of the blue laser increased to 6.52 W/mm2. Also, a 4053K CCT of the warm white light emission was realized. Therefore, this work proves that the LCMASG PCs are promising to serve as color converters for high power LEDs/LDs lighting in the future.

Al2O3-YAG:Ce/YAG composite ceramic phosphor in a transmissive configuration for high-brightness laser-driven lighting.

High-power, high-brightness laser lighting promotes new requirements for light-conversion materials, such as high thermal conductivity, high saturation threshold and compact encapsulation. In this paper, we designed and fabricated a novel composite structure ceramic including a 1.0 × 1.0 mm2 Al2O3-YAG:Ce ceramic and a φ=16.0 mm transparent YAG ceramic for the transmissive configuration in laser lighting. When pumped by blue laser from 0∼60 W mm2, all the samples exhibited no luminous saturation phenomenon, and the 10.0 wt.%Al2O3-YAG:Ce/YAG composite ceramic with the thickness of 0.3 mm maintained white light with a luminous efficacy over 200 lm/W. Moreover, a maximal luminous flux over 1000 lm, a correlated color temperature (CCT) of 5471 K, and an operating temperature as low as 92.3 °C were obtained under the excitation power density as high as 60 W/mm2. The configuration that Al2O3-YAG:Ce encapsulated by YAG reflects an excellent optical and thermal properties by using transparent and highly thermally conductive YAG materials. These results indicate that Al2O3-YAG:Ce/ YAG composite ceramic phosphor is a promising candidate in transmissive configuration for automotive lighting and laser searchlight.

Qualitative and Quantitative Assessments of Apple Quality Using Vis Spectroscopy Combined with Improved Particle-Swarm-Optimized Neural Networks.

Exploring a cost-effective and high-accuracy optical detection method is of great significance in promoting fruit quality evaluation and grading sales. Apples are one of the most widely economic fruits, and a qualitative and quantitative assessment of apple quality based on soluble solid content (SSC) was investigated via visible (Vis) spectroscopy in this study. Six pretreatment methods and principal component analysis (PCA) were utilized to enhance the collected spectra. The qualitative assessment of apple SSC was performed using a back-propagation neural network (BPNN) combined with second-order derivative (SD) and Savitzky-Golay (SG) smoothing. The SD-SG-PCA-BPNN model's classification accuracy was 87.88%. To improve accuracy and convergence speed, a dynamic learning rate nonlinear decay (DLRND) strategy was coupled with the model. After that, particle swarm optimization (PSO) was employed to optimize the model. The classification accuracy was 100% for testing apples via the SD-SG-PCA-PSO-BPNN model combined with a Gaussian DLRND strategy. Then, quantitative assessments of apple SSC values were performed. The correlation coefficient (r) and root-square-mean error for prediction (RMSEP) in testing apples were 0.998 and 0.112 °Brix, surpassing a commercial fructose meter. The results demonstrate that Vis spectroscopy combined with the proposed synthetic model has significant value in qualitative and quantitative assessments of apple quality.

Optoacoustic classification of diabetes mellitus with the synthetic impacts via optimized neural networks.

A highly accurate classification of diabetes mellitus (DM) with the synthetic impacts of several variables is first studied via optoacoustic technology in this work. For this purpose, an optoacoustic measurement apparatus of blood glucose is built, and the optoacoustic signals and peak-peak values for 625 cases of in vitro rabbit blood are obtained. The results show that although the single impact of five variables are obtained, the precise classification of DM is limited because of the synthetic impacts. Based on clinical standards, different levels of blood glucose corresponding to hypoglycaemia, normal, slight diabetes, moderate diabetes and severe diabetes are employed. Then, a wavelet neural network (WNN) is utilized to establish a classification model of DM severity. The classification accuracy is 94.4 % for the testing blood samples. To enhance the classification accuracy, particle swarm optimization (PSO) and quantum-behaved particle swarm optimization (QPSO) are successively utilized to optimize WNN, and accuracy is enhanced to 98.4 % and 100 %, respectively. It is demonstrated from comparison between several algorithms that optoacoustic technology united with the QPSO-optimized WNN algorithm can achieve precise classification of DM with synthetic impacts.

Quantitative measurement of blood glucose influenced by multiple factors via photoacoustic technique combined with optimized wavelet neural networks.

In this work, the photoacoustic (PA) quantitative measurement of blood glucose concentration (BGC) influenced by multiple factors was firstly investigated. A set of PA detection system of blood glucose considering the comprehensive influence of five factors was established. The PA signals and peak-to-peak values (PPVs) of 625 rabbit whole blood were obtained under 625 influence combinations. Due to the accurate measurement of BGC limited by the overlap PA signals, wavelet neural network (WNN) was utilized to train the PPVs of blood glucose for 500 rabbit blood. The mean square error (MSE) of BGC for 125 testing blood was approximately 6.5782 mmol/L. To decrease the MSE, the parameters of WNN were optimized by particle swarm optimization (PSO), that is, PSO-WNN algorithm was employed. Under the optimal parameters, MSE of BGC was decreased to approximately 0.48005 mmol/L. To further improve the prediction accuracy of BGC, an improved nonlinear dynamic inertia weight (NDIW) strategy of PSO was proposed, and compared with other two kinds of dynamic inertia weight strategies. Under the optimal parameters, the MSE of BGC was decreased to approximately 0.2635 mmol/L. The comparison of nine algorithms demonstrate that the PA technique combined with PSO-WNN and the improved NDIW strategy is significant in the quantitative measurement of blood glucose influenced by multiple factors.