Improved Fluorescence and Gain Characteristics of Er-Doped Optical Fiber with PbS Nanomaterials Co-Doping.

Er-doped optical fiber (EDF) with ultra-broad gain bandwidth is urgently needed given the rapid advancement of optical communication. However, the weak crystal field of the host silica glass severely restricts the bandwidth of traditional EDF at 1.5 µm. In this study, we theoretically explored the introduction of PbS nanomaterials in the silica network assisted with the non-bridging oxygen. This can significantly increase the crystal field strength of Er3+ ions in the local structure, leading to their energy level splitting and expanding the fluorescence bandwidth. Additionally, the PbS/Er co-doped optical fiber (PEDF) with improved fluorescence and gain characteristics was fabricated using modified chemical vapor deposition combined with the atomic layer deposition technique. The presence of PbS nanomaterials in the fiber core region, which had an average size of 4 nm, causes the 4I13/2 energy level of Er3+ ions to divide, increasing the fluorescence bandwidth from 32 to 39 nm. Notably, the gain bandwidth of PEDF greater than 20 dB increased by approximately 12 nm compared to that of EDF. The obtained PEDF would play an important role in the optical fiber amplifier and laser applications.

Flexible Scintillation Silica Fiber with Engineered Nanocrystals for Remote Real-Time X-ray Detection.

Scintillation fibers based on rare-earth ion-doped crystal materials have attracted significant attention for applications in a wide range of areas from security to healthcare. However, the scintillation performance of crystal fibers is severely limited owing to the complex preparation process. Here, we report a modified preparation process of the transparent Ce/Tb co-doped yttrium pyrosilicate (YPS) nanocrystal silica fiber for the first time, which was fabricated by the CO2 laser-heated method assisted with optimal thermal annealing. An YPS nanocrystal phase with an average size of approximately 38 nm is obtained by controlling the diffusion concentration of SiO2 in the fiber core region. Both Ce3+ and Tb3+ ions were successfully embedded into YPS nanocrystals, which enhanced the energy transfer with an efficiency of 59.87% between the dopants as well as brighter green light emission. Furthermore, the X-ray-excited remote radioluminescence response of the obtained YPS nanocrystal fiber with a length of 20 m was approximately 1 order of magnitude larger than that of the precursor fiber, while the dose rate response exhibited excellent linearity. It is believed that the novel transparent YPS nanocrystal-doped silica optical fibers, combined with their excellent fluorescent properties, could be promising candidates for scintillators, fiber lasers, and phosphors.

Tapered fiber radiation sensor based on Ce/Tb:YAG crystals for remote γ-ray dosimetry.

A novel tapered fiber-optic radiation sensor (TFRS) based on cerium (Ce) and terbium (Tb) co-doped YAG scintillation crystals is demonstrated for the first time. Using the CO2 laser-heated method, a Ce/Tb:YAG crystal is well embedded into silica glass cladding without any cracks. The scintillation light emitted from the YAG scintillation crystal can be directly coupled into the derived silica optical fiber by the tapered region. The loss of the derived optical fiber is 0.14 dB/cm, which is one order of magnitude lower than the 1.59 dB/cm of the YAG crystal in the TFRS. Subsequently, strong photo- and radio-luminescence of Tb3+ (5D4→7F5) ions in TFRS are achieved under ultraviolet light and high-energy ray excitation, respectively. In particular, a prominent remote radiation response of the TFRS is presented under excitation by γ-rays through fusion splicing with multimode optical fibers. The response is approximately four times larger than that of a plastic scintillation fiber (BCF-12) sensor. Furthermore, the results possess high stability as well as a good linearity between the radiation dose rate and the response intensity. The TFRS in combination with an all-silica fiber system is a promising candidate for remote radiation detection.

Ultra-wideband and flat-gain optical properties of the PbS quantum dots-doped silica fiber.

We investigate the microstructural characteristics and optical properties of PbS quantum dots-doped silica fiber (PQDF), prepared by atomic layer deposition (ALD) doping technique. The fiber exhibits ultra-wideband luminescence and flat-gain with 3 dB bandwidth of 300 nm. The on-off gain and net gain can reach to 7.1-15.0 dB and 6.0-9.2 dB at 1050-1350 nm, respectively. The results of high-resolution transmission electron microscopy (HRTEM) further reveal the effects of PbS QDs doping in PQDF. The broadband luminescence spectrum originating from three active centers (1086, 1179, and 1304 nm), can be attributed to the dimension effect of PbS QDs (3.7, 4.0, and 4.3 nm, respectively). Moreover, the calculation results indicate that the multi-sized PbS QDs concentrated at 3.65-4.45 nm make the 3 dB gain bandwidth increase, which is six times wider than that of traditional erbium-doped fiber (EDF). Therefore, this type of PQDF is a promising gain medium for optical amplifiers and broadband light sources.