Volatile organic solids, such as cyclododecane or menthol, have been employed as temporary reinforcement material during archaeological excavations. They are usually applied as melts and reinforcement is achieved once the melts solidify. Such solidification process can induce internal stress on the artifacts, which can be a big concern, especially to those very precious and fragile ones. However, information about such stress is still extremely limited at present. This paper proposes an experimental method based on resistance strain gauge technique to monitor the deformation induced by solidification of menthol melt. Bending tests are performed on very thin glass slides. The solidification process of menthol melt is well characterized by the development of mechanical strains. Then, menthol melts are applied to three kinds of simulated samples, i.e. glass, sandstone and rice paper, to investigate the mechanical response of preserved bodies upon solidification. It is found that menthol melt will generate certain amount expansion or contraction of the objects upon solidification. The stresses induced, evaluated according to obtained strains, are generally quite small, indicating that application of menthol as reinforcement material is safe in mechanics for cultural relics.

We investigate the spectral and amplification characteristics of Bi/Er co-doped fiber (BEDF) and Er-doped fiber (EDF), prepared by atomic layer deposition (ALD). BEDF features a noise figure (NF) below 5.2 dB, the bandwidth with NF less than 4 dB is approximately 23 nm (1560-1583 nm), and that with a gain exceeding 25 dB is approximately 42 nm (1525-1567 nm). The quantum conversion efficiency (QCE) of BEDF at 1550 nm is 72.1% at a pump power of 300 mW. The saturated output power of BEDF at 1550 nm is 21.4 dBm. Raman spectra indicate that the maximum phonon energy of BEDF is lower than that of EDF. The fluorescence lifetime of the BEDF is 11.64 ms, which is longer than that of the EDF. These results show that co-doping with Bi ions could increase the fluorescence lifetime of Er 3+ , reduce the NF, and improve the QCE and saturated output power. Therefore, this type of BEDF is a promising gain medium for optical amplifiers and lasers.

We report a novel PbS/Er co-doped silica fiber (PEDF) with improved spectral properties in O-band (1260-1360 nm). The results show that the gain of the PEDF exceeds 15 dB in the range of 1150-1360 nm. Compared to PbS-doped silica fiber, the PEDF has a gain improvement of 6.4-10.9 dB in O-band. In addition, the concentration of Pb and S in the PEDF core is significantly higher, and the size distribution of PbS nanoparticles is more concentrated in a narrow range. These factors may account for the enhanced gain characteristics of the PEDF. This work reveals the positive effect of co-doping Er 3+ ions on the gain characteristics of the PEDF in O-band, and suggests an important research direction for the design of broadband amplifiers and light sources for optical communication with zero dispersion. Index Terms-Broadband amplifiers, gain characteristics, PbS nanoparticles, PbS/Er co-doped silica fiber. I. INTRODUCTIONE XPANDING the bandwidth of optical fiber amplifiers and enhancing the gain characteristics can improve the efficacy of communication systems [1], [2]. Erbium-doped fiber amplifiers and other rare-earth-doped fiber amplifiers can achieve high gain in specific wavelength bands. However, the gain bandwidths are usually limited because of the inherent energy-level structure of rare earth (RE) ions [3], [4]. Bi-doped fiber amplifiers exhibit broadband luminescence and amplification. However, the nature of Bi active centers remains controversial and it is difficult to control during the fabrication process. Hence, it is crucial to identify new materials for improving the optical properties of actively doped fibers in the near-infrared band.Recently, nano-semiconductor materials with high quantum efficiency, bandgap tunability, and broad spectral properties have received widespread attention [5], [6]. Compared to other nano-semiconductors, those in the IV-VI group have significant Manuscript

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Volatile organic solids, such as cyclododecane or menthol, have been employed as temporary reinforcement material during archaeological excavations. They are usually applied as melts and reinforcement is achieved once the melts solidify. Such solidification process can induce internal stress on the artifacts, which can be a big concern, especially to those very precious and fragile ones. However, information about such stress is still extremely limited at present. This paper proposes an experimental method based on resistance strain gauge technique to monitor the deformation induced by solidification of menthol melt. Bending tests are performed on very thin glass slides. The solidification process of menthol melt is well characterized by the development of mechanical strains. Then, menthol melts are applied to three kinds of simulated samples, i.e. glass, sandstone and rice paper, to investigate the mechanical response of preserved bodies upon solidification. It is found that menthol melt will generate certain amount expansion or contraction of the objects upon solidification. The stresses induced, evaluated according to obtained strains, are generally quite small, indicating that application of menthol as reinforcement material is safe in mechanics for cultural relics.