In this paper, a low loss and high polarization-maintaining single-mode hollow-core anti-resonant fiber (PM-HC-ARF) is designed. The elliptical core in the PM-HC-ARF is formed by strategically enlarging selected cladding air holes along the y-axis. Additionally, the variations in the wall thickness in both the x and y directions generate the distinct surface modes. By simultaneously employing an elliptical core and asymmetric core-wall thickness, we enhance the phase birefringence. Theoretical analysis results show that the proposed PM-HC-ARF achieves a transmission loss of 0.00082 dB/m at wavelength 1450 nm, along with a birefringence of 1.38 × 10⁻⁴; it demonstrates CL levels an order of magnitude below state-of-the-art polarization-maintaining HC-ARFs. Moreover, within the S+C+L+U communication bands, it achieves a bandwidth exceeding 380 nm (1420–1800 nm) while maintaining a birefringence of greater than 1.45 × 10⁻⁴. In particular, this PM-HC-ARF demonstrates a maximum higher-order mode extinction ratio of over 32,070; the single-mode transmission characteristics are excellent, along with exceptional bending resistance characteristics. When the bending radius exceeds 3 cm, the impacts on the loss and birefringence are negligible; this also demonstrates that the fiber structure shows good robustness when subjected to harsh environment interference. The proposed PM-HC-ARF is believed to have important applications in fiber optic gyroscopes, optical amplifiers, and hydrophones.

表面增强拉曼散射（SERS）技术可有效增强样品分子的拉曼信号，对生物分子检测具有较高的灵敏性，因此在生化方面有着许多潜在的应用.而将空芯微结构光纤与SERS技术相结合不仅能够远端实时、分布式地检测，同时还可以增加光场与待测物的有效作用面积，减少传统光纤探针无法避免的石英背景信号等问题.本文基于空芯微结构光纤进行SERS探针的制备及性能测试研究，利用真空物理溅射法在空芯光纤内镀纳米Ag膜，从而制备成SERS探针，通过实验检测不同浓度的罗丹明6G（R6G）酒精溶液的拉曼信号.结果表明，在探针的近端正面成功探测到了浓度低至10-9 mol/L的R6G拉曼信号，在探针的远端反面探测到的浓度可小于10-6 mol/L.该实验结果为研究高灵敏度的SERS探针提供了一种新的手段.

A surface plasmon resonance (SPR) sensor with two orthogonal open loops based on microstructured optical fibers (MOFs) is introduced. The interaction between core mode and surface plasmon polariton (SPP) mode produced by two different metal films is studied. Full vector finite element method is used to analyze the coupling and sensing characteristics. The results show that there are three loss peaks near the Au/Ag film, and multi-peak calibration is achieved. Because of the positive and negative sensitivity of the amplitude, the sensor has strong anti-interference capability when the external environment changes. The sensor can detect the refractive index between 1.37 and 1.40, and the working wavelength is between 1600 nm and 2400 nm. Because the sensor has some excellent characteristics, it can be used in biochemical sensing, environmental detection, and other related fields.

The 4f¹³5d–4f¹⁴ energy transition of Yb²⁺ ions can cover the whole white light wavelength, Yb²⁺-doped materials have thus been a hot research field. In order to obtain a white light source, many kinds of Yb²⁺-doped materials have been prepared. In this study, divalent Yb²⁺-doped silica fiber was fabricated using rod-in-tube technology. The fiber core of Yb²⁺-doped silica glass was prepared with high-temperature melting technology under vacuum conditions. The spectroscopic properties of the Yb²⁺-doped glass and fiber were studied. The experiments indicate that divalent Yb²⁺-doped glass has a high quantum efficiency and super-broadband fluorescence in the visible region with an excitation wavelength of 405 nm. In addition, the results suggest that Yb²⁺-doped fiber has a potential for application in visible fiber lasers and fiber amplification.

In this paper, a low loss and high polarization-maintaining single-mode hollow-core anti-resonant fiber (PM-HC-ARF) is designed. The elliptical core in the PM-HC-ARF is formed by strategically enlarging selected cladding air holes along the y-axis. Additionally, the variations in the wall thickness in both the x and y directions generate the distinct surface modes. We have effectively enhanced the birefringence performance of the fiber structure design by introducing the combined effect of the two. Theoretical analysis results show that the proposed PM-HC-ARF achieves a transmission loss of 0.82 dB/km at wavelength 1450 nm, along with a birefringence of 1.38 × 10-4, it demonstrates CL levels an order of magnitude below state-of-the-art polarization-maintaining HC-ARFs. Moreover, within the S+C+L+U communication bands, it achieves a bandwidth exceeding 380 nm(1420-1800nm) while maintaining a birefringence of greater than1.45 × 10-4. Especially, this PM-HC-ARF demonstrates a maximum higher-order mode extinction ratio of over 32,070, the single-mode transmission characteristics are excellent. along with exceptional bending resistance characteristic. When the bending radius exceeds 3 cm, the impacts on the loss and birefringence are negligible, this also demonstrates that the fiber structure shows good robustness when subjected to harsh environment interference. The proposed PM-HC-ARF is believed to have important applications in the fiber optic gyroscopes, optical amplifiers, and hydrophones.

We report on a single-stage, high-repetition photonic crystal fiber amplifier working at 1030 nm seeded by a femtosecond fiber laser, which generates an output with average power of 2.23 W at a repetition rate of 49.5 MHz and a 3 dB spectral width of 5 nm, corresponding to a pulse energy of 45.2 nJ. After amplification, the spectrum of the femtosecond laser is broadened. A home-made, ytterbium-doped, double-clad photonic crystal fiber fabricated by laser sintering technology combined with a solution doping method with a core diameter of only 24 μm is used as the power amplifier medium. The spectral characteristics as well as the suppression of amplified spontaneous emission are discussed in detail. Experiment confirms that the amplified spontaneous emission becomes negligible with increasing incident seed power and no obvious nonlinear effects arise in this experiment. These results can provide motivation for the application of ytterbium-doped photonic crystal fiber and can provide a potential application for the high-power, all-fiber laser in the future.