Dense and transparent ceramic samples of a (Gd,Y)3Al2Ga3O12:Ce scintillator were obtained by using stereolithography-based Digital Light Processing (DLP) 3D printing for compacting, subsequent burnout, and pressureless sintering. The effects of stoichiometric deviations and green body compaction methods (uniaxial pressing versus DLP 3D printing) on the optical, luminescent, and scintillation properties of ceramics were analyzed. An excess of Y and Gd in the composition led to an increase in transmittance and to the acceleration of the scintillation kinetics. Moreover, transparent ceramics made ..read more

In this paper we present the principle of operation, fabrication and performance of a phosphorescent optical-fiber quasi-distributed sensor with contactless smartphone interrogation. An array of short strong corrugated long-period gratings (C-LPG) is used as a platform to spatially locate and to excite the phosphors whose time responses are temperature-dependent. The C-LPG array was fabricated using a pulsed CO2 laser. The quasi-distributed sensing array is excited by a UV LED and the normalized differential rise/decay time response measured by a smartphone is used as a measure of the temperat ..read more

We utilize a femtosecond laser-inscribed small-period long-period fiber grating (SP-LPFG) to induce a nonlinear polarization rotation (NPR) effect for mode-locking pulses in a normal dispersion erbium-doped fiber laser (EDFL). The SP-LPFG has a length of 2.5 mm and a period of 25 μm. At wavelengths of 1556 nm and 1561 nm, it exhibits polarization-dependent loss (PDL) values of 20 dB and 14.5 dB, respectively, sufficient to trigger the NPR mechanism. With the pump power increased to 500 mW, the laser achieves normal dispersion mode-locked pulses centered at 1575 nm in the L-band, with a ..read more

Photonics, Vol. 11, Pages 692: Experimental Investigation on the Dynamics Characteristics of a Two-State Quantum Dot Laser under Optical Feedback Photonics doi: 10.3390/photonics11080692 Authors: Yanfei Zheng Guang-Qiong Xia Xiaodong Lin Ruilin Fang Qingqing Wang Fengling Zhang Zheng-Mao Wu We experimentally investigate the dynamics characteristics of a two-state quantum dot laser (TSQDL) subject to optical feedback. Firstly, we inspect the impact of the temperature on the power-current characteristics of the ground state (GS) lasing and the excited state (ES) lasing in the TSQDL operating at ..read more

Photonics, Vol. 11, Pages 691: Unraveling the Dominant Size Effect in Polydisperse Solutions and Maximal Electric Field Enhancement of Gold Nanoparticles Photonics doi: 10.3390/photonics11080691 Authors: Quang Truong Pham Gia Long Ngo Chi Thanh Nguyen Isabelle Ledoux-Rak Ngoc Diep Lai In this study, we systematically investigate theoretically and experimentally the plasmonic effect and roles of big and small gold nanoparticles (Au NPs) within a mixed solution. The polydisperse solution was initially prepared by mixing small (10, 30 nm) Au NPs with larger ones (50, 80 nm), followed by measuring ..read more

Photonics, Vol. 11, Pages 687: Evaluation of Fluorescence Contrast for the Differentiation of Ex Vivo Tissue Slides from Collagen-Related Degenerative Skin Diseases Photonics doi: 10.3390/photonics11080687 Authors: Tsanislava Genova Petya Pavlova Lidia Zaharieva Petranka Troyanova Ivan Terziev Histopathological analysis is one of the primary pillars in clinical diagnostics. The efforts to implement optical techniques aim at alleviating the burden of delivering timely and accurate diagnoses. We have explored the potential application of unstained tissue slides’ autofluorescence to ..read more

Photonics, Vol. 11, Pages 688: A Segment-Based Algorithm for Grid Junction Corner Detection Used in Stereo Microscope Camera Calibration Photonics doi: 10.3390/photonics11080688 Authors: Junjie Liu Weiren Zhao Keming Li Jiahui Wang Shuangping Yi Huan Jiang Hui Zhang Corner detection is responsible for accurate camera calibration, which is an essential task for binocular three-dimensional (3D) reconstruction. In microscopic scenes, binocular 3D reconstruction has significant potential to achieve fast and accurate measurements. However, traditional corner detectors and calibration patterns (chec ..read more

Photonics, Vol. 11, Pages 690: Broadband Spin-Selective Wavefront Manipulations with Generalized Pancharatnam–Berry Phase Metasurface Photonics doi: 10.3390/photonics11080690 Authors: Shiming Gan Tianci Zhao Xiuzhuang Mei Tingting Zhang Zhiqi Wang Hongyu Gao Gensen Yang Jixiang Cai Fuzhong Bai Metasurfaces can flexibly manipulate electromagnetic waves by engineering subwavelength structures, which have attracted enormous attention in holography, cloaking, and functional multiplexing. For structures with n-fold (n > 2) rotational symmetry, they have been utilized to realize ..read more

Photonics, Vol. 11, Pages 689: Characterising Spatio-Temporal Coupling of Tightly Focused Femtosecond Laser Pulses in Micro-Structured Dispersive Materials Photonics doi: 10.3390/photonics11080689 Authors: Laura Ionel A 2D numerical model based on the finite-difference time-domain (FDTD) method had been developed to investigate the correspondence between the spatio-temporal aspects and intensity evolution of a focused laser beam after the propagation through micro-structured dispersive materials under the pulse duration variation in the few-cycle regime. In parallel with the laser field intens ..read more

Photonics, Vol. 11, Pages 684: Nonlinear Dynamics of Silicon-Based Epitaxial Quantum Dot Lasers under Optical Injection Photonics doi: 10.3390/photonics11080684 Authors: Ruilin Fang Guang-Qiong Xia Yan-Fei Zheng Qing-Qing Wang Zheng-Mao Wu For silicon-based epitaxial quantum dot lasers (QDLs), the mismatches of the lattice constants and the thermal expansion coefficients lead to the generation of threaded dislocations (TDs), which act as the non-radiative recombination centers through the Shockley–Read–Hall (SRH) recombination. Based on a three-level model including ..read more