Owing to the unique mechanism of photoelectron storage and release, long persistent phosphorescence, also called long persistent luminescence or long lasting afterglow/phosphorescence, plays a pivotal role in the areas of spectroscopy, photochemistry, photonics and materials science. In recent years, more research has focused on the manipulation of the morphology, operational wavebands and persistent duration of long persistent phosphors (LPPs). These desired achievements stimulated the growing interest in designing bio-labels, photocatalysts, optical sensors, detectors and photonic devices. In this review, we present multidisciplinary research on synthetic methods, afterglow mechanisms, characterization techniques, materials system, and applications of LPPs. First, we introduce the recent developments in LPPs for the synthesis of nanoparticles from the aspects of particle sizes, monodispersity and homogeneity based on the urgent application of bio-imaging. In the later sections, we present the possible mechanisms, which involve the variation of trap distribution during the trapping and de-trapping process, complicated photo-ionization reaction of trap site levels and impurity centers together with their corresponding migration kinetics of carriers. Meanwhile, we emphasize the characterization techniques of defects, used to qualitatively or quantitatively describe the types, concentrations and depths of the traps. This review article also highlights the recent advances in suggested LPPs materials with a focus on the LPPs' hosts and optically active centers as well as their control, tuning and intrinsic links. We further discuss the classification of LPPs based on the different emission and excitation wavebands from the ultraviolet to the near-infrared region along with an overview of the activation mode of afterglow. Afterwards, we provide an exhibition of new products towards diverse application fields, including solar energy utilization, bio-imaging, diagnosis, and photocatalysts. Finally, we summarize the current achievements, discuss the problems and provide suggestions for potential future directions in the aforementioned parts.

We show that permanent optical waveguides can be formed in various bulk glasses by photoinduced refractive index change with an ultrashort pulse laser. The waveguides were fabricated by focusing the laser beam through an microscope objective and translating the sample parallel to the axis of the laser beam. From the observations of intensity distributions in the output of guided light by a CCD camera, we demonstrated that permanent optical waveguides can be successfully formed in various glasses. In addition, from the analysis of a near-field pattern, it was confirmed that single mode waveguides of the graded index type can be formed by a writing technique using the ultrashort pulse laser.

Low-dimensional (LD) materials demonstrate intriguing optical properties, which lead to applications in diverse fields, such as photonics, biomedicine and energy. Due to modulation of electronic structure by the reduced structural dimensionality, LD versions of metal, semiconductor and topological insulators (TIs) at the same time bear distinct nonlinear optical (NLO) properties as compared with their bulk counterparts. Their interaction with short pulse laser excitation exhibits a strong nonlinear character manifested by NLO absorption, giving rise to optical limiting or saturated absorption associated with excited state absorption and Pauli blocking in different materials. In particular, the saturable absorption of these emerging LD materials including two-dimensional semiconductors as well as colloidal TI nanoparticles has recently been utilized for Q-switching and mode-locking ultra-short pulse generation across the visible, near infrared and middle infrared wavelength regions. Beside the large operation bandwidth, these ultrafast photonics applications are especially benefit from the high recovery rate as well as the facile processibility of these LD materials. The prominent NLO response of these LD materials have also provided new avenues for the development of novel NLO and photonics devices for all-optical control as well as optical circuits beyond ultrafast lasers.