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Zhu S.,Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications | Zhu S.,Jinan University | Wang C.,State Key Laboratory of Luminescence Materials and Devices | Li Z.,Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications | And 12 more authors.
Optics Letters | Year: 2016

We investigate the broadband anti-Stokes emission (BASE) from Yb 3+ -doped crystals with a laser diode (LD) pumping at 940 nm. Our experiment reveals that Yb 3+ -doped crystals with random cracks are able to generate bright BASE at room temperature and atmospheric pressure. By examining the various characteristics of the crystals and the emitted light, we supply a theory for interpreting the underlying physics for this variety of BASE. In particular, we take into consideration the effects of energy migration, avalanche process, and charge-transfer luminescence. This represents the first time, to the best of our knowledge, that BASE was obtained from Yb 3+ -doped bulk crystals with a high opticaloptical efficiency © 2016 Optical Society of America. Source


Zhu S.,Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications | Zhu S.,Jinan University | Zhou H.,Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications | Zhou H.,Jinan University | And 9 more authors.
Applied Optics | Year: 2016

An Nd:YAG?YAG?Cr 4+ :YAG?YAG composite crystal and an LBO crystal were used to generate a passively Q-switched frequency-doubling 473 nm blue laser for the first time, to the best of our knowledge. The result demonstrated that the slope efficiency of this system reaches 18%, which is the highest in all the passively Q-switched 473 nm laser systems reported, to the best of our knowledge. Under the pumped power of 8.64 W, the maximum average output power of 0.93 W was obtained with a pulsewidth of 78 ns, and the repetition rate of 18.5 kHz. © 2016 Optical Society of America. Source


Su K.,Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications | Su K.,Jinan University | Zhu S.,Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications | Zhu S.,Jinan University | And 13 more authors.
Optical Engineering | Year: 2016

The rapid and accurate classification of bee pollen grains is still a challenge. The purpose of this paper is to develop a method which could directly classify bee pollen grains based on fluorescence spectra. Bee pollen grain samples of six species were excited by a 409-nm laser diode source, and their fluorescence images were acquired by a hyperspectral microscopy imaging (HMI) system. One hundred pixels in the region of interest were randomly selected from each single bee pollen species. The fluorescence spectral information in all the selected pixels was stored in an n-dimensional hyperspectral data set, where n=37 for a total of 37 hyperspectral bands (465 to 645 nm). The hyperspectral data set was classified using a Fisher linear classifier. The performance of the Fisher linear classifier was measured by the leave-one-out cross-validation method, which yielded an overall accuracy of 89.2%. Finally, additional blinded samples were used to evaluate the established classification model, which demonstrated that bee pollen mixtures could be classified efficiently with the HMI system. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE). Source

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