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Large-mode-area anti-resonant fibers (LMA ARF) with high beam quality have the potential to revolutionize mid-infrared high-power laser delivery by mitigating mode instabilities and nonlinear degradation. However, their tens-of-microns mode field diameters and small numerical aperture significantly increase the mode field mismatch and coupling complexity, respectively. In this work, an LMA all-solid anti-resonant fiber-microlens with a robust operation of high beam quality in the mid-infrared region was designed and prepared. It can significantly stabilize the efficiencies of coupling and transmission at a large radial offset. Consequently, this AS-ARF demonstrates substantial potential for advancing mid-infrared laser power delivery via fiber, ensuring exceptional beam quality throughout the process. [ABSTRACT FROM AUTHOR]

Erbium-doped glass microsphere laser systems hold significant promise in the applications of bio-medicine and optical fiber sensing. However, their development has been hindered by the relatively high laser pump threshold. In this study, we proposed a unique dual microsphere system where two microspheres are affixed to a single-mode fiber taper and achieved a remarkably low lasing threshold of 19 μW for single-mode laser emission at 1544 nm. This is in sharp contrast with the lasing threshold of 56 μW observed in single microspheres. Our findings represent a significant achievement in the development of low-threshold, compact infrared laser sources for emerging applications in photonics. [ABSTRACT FROM AUTHOR]

In order to address the 'capacity crisis' caused by the narrow bandwidth of the current C band and the demand for wide-spectrum sensing sources and tunable fiber lasers, a broadband luminescence covering the C + L bands using Er3+/Yb3+ co-doped fluorotellurite glass fiber is investigated in this paper. The optimal doping concentrations in the glass host were determined based on the intensity, lifetime, and full width at half maximum (FWHM) of the fluorescence centered at 1.5 µm, which were found to be 1.5 mol% Er2O3 and 3 mol% Yb2O3. We also systematically investigated this in terms of optical absorption spectra, absorption and emission cross-sections, gain coefficients, Judd–Ofelt parameters, and up-conversion fluorescence. The energy transfer (ET) mechanism between the high concentrations of Er3+ and Yb3+ was summarized. In addition, a step-indexed fiber was prepared based on these fluorotellurite glasses, and a wide bandwidth of ~112.5 nm (covering the C + L bands from 1505.1 to 1617.6 nm) at 3 dB for the amplified spontaneous emission (ASE) spectra has been observed at a fiber length of 0.57 m, which is the widest bandwidth among all the reports based on tellurite glass. Therefore, this kind of Er3+/Yb3+ co-doped fluorotellurite glass fiber has great potential for developing broadband C + L band amplifiers, ultra-wide fiber sources for sensing, and tunable fiber lasers. [ABSTRACT FROM AUTHOR]

Extinction ratio (ER) is one of the important parameters to characterize the polarization‐maintaining (PM) performance of the fiber. In this paper, we report the preparation and properties of a novel chalcogenide microstructure fiber with a high ER. We fabricate a preform using a peeled‐off extrusion method. The core and cladding material of the fiber are Ge9As23Se68 and Ge10As22Se68. The preform was drawn into a fiber with an average ER of −17.08 dB. The loss of the fiber is less than 2 dB over 5.20–8.55 μm, and the minimum loss of the fiber is 0.57 dB/m at 6.2 μm. Moreover, a flat mid‐infrared supercontinuum spectrum spanning from 1.53 to 12.50 μm is generated by pumping an 18‐cm‐long PM fiber for the first time. [ABSTRACT FROM AUTHOR]

Supercontinuum sources with high compactness are essential for applications such as optical sensing, airborne detection and communication systems. In the past decades, the adoption of bulky optical parametric amplifier to pump various chalcogenide glass waveguides are widely reported for on-chip mid-infrared supercontinuum generation, but this usually leads to a large volume of the whole system, and is not practical. Therefore, integrating advanced femtosecond fiber lasers with optical waveguides using nano-fabrication technology are highly desired. However, the scarcity of compact pump sources and the dispersion-matched high-nonlinearity waveguide in short wavelength regions have hindered the advancement of integrated supercontinuum source performances in the near and mid-infrared region. In this study, we demonstrate a broadband supercontinuum source from As 2 S 3 waveguide pumped by a compact dual-femtosecond solitons pulse source. The laser is completely fiber structured, and its wavelength can be readily tuned from 2 to 2.3 µm using Raman soliton self-frequency shift technology in a Tm 3+ -doped fiber amplifier. Furthermore, the As 2 S 3 waveguide is designed with controllable dispersion and high nonlinearity for a broadband supercontinuum generation. These results will advance the development of on-chip supercontinuum sources based on chalcogenide waveguides.

Nd 3+ -doped glasses are the most widely used laser gain media. However, Nd 3+ -doped non-silica microsphere lasers generally have lower quality (Q) factors due to the presence of non-radiative energy-loss impurities in traditional glass systems. In this work, we report the first, to the best of our knowledge, Nd 3+ -doped phosphate glass microsphere laser with the highest Q-factor of 1.54 × 10 6 among all Nd 3+ -doped non-silica glass microsphere lasers. Whispering gallery modes in the 1020-1120-nm band can be obtained for a typical microsphere with a diameter of 82.57 µm. When the pump power exceeds the threshold of 0.17 mW, single- and multi-mode microsphere lasing can be generated under 808-nm laser diode (LD) pumping. Typical Q-factors of the phosphate glass microspheres can reach 10 6 , which is at least an order of magnitude higher than those of other Nd 3+ -doped non-silica glass microsphere lasers. The Nd 3+ -doped phosphate glass microsphere laser reported in this work can be considered as an active optical/photonic device with low pump thresholds.

The complete removal of the impurities like Se-H in Se-based chalcogenide glasses has been challenging in the development of highly transparent chalcogenide glass fiber. In this paper, several purification methods, including dynamic distillation, static distillation, and combined distillation method, were adopted with an aim of purifying arsenic selenide glass with ultra-low content of the impurities. The experimental results demonstrated that the Se-H can be completely eliminated in the arsenic selenide glass host and fiber without the introduction of any chloride. We further explored the applications of such low loss and Se-H-free chalcogenide glass fiber in the mid-infrared. It was found that, using such a Se-H free fiber, a flattened supercontinuum spectrum above the -30 dB level from 1.2 to 13 µm was generated from the Se-H free fiber with a 5.5 µm laser pumping. The sensitivity was found to be improved 5.1 times for CO 2 gas in the 3 to 6 µm wavelength range.

Chalcogenide glass possesses outstanding advantages, such as supercontinuum generation, but its nonlinear applications were limited by large zero-dispersion wavelength (ZDW). Traditional suspended-core fibers can shift the ZDW to near IR with a tiny core size of less than 5 µm but a large evanescent wave loss exists in these fibers. In this paper, we prepared a novel suspended-core fiber (SCF) based on chalcohalide glasses for the first time via the extrusion method, in which the ZDW of the fundamental mode in the fiber with a core size of larger than 30 µm was successfully shifted to 2.6 µm. We also calculated confinement loss (CL) of propagation modes and fundamental mode energy ratio in the fiber. We found that the minimum CL ratio of the high order modes (LP 11 ) to the CL of the fundamental mode is 124, indicating that the single-mode operation condition is satisfied when the wavelength is more than 4.6 µm. The lowest transmission loss is 1.2 dB/m at 6.5 µm. An ultra-broad supercontinuum spectrum, covering from 1.6 to 12 µm was generated in this suspended-core fiber pumped by a 5 µm femtosecond laser. Such a wide SC in the chalcogenide SCF is due to the large core size. All these results demonstrate the potential to use the large core SCF in the application of a mid-IR laser.

We demonstrate a thulium-doped mode-locked fiber laser with ultra-broadband wavelength tunability for micro-strain sensing based on the multimode interference (MMI) effect in single-mode-multimode-single-mode (SMS) fiber configuration. The homemade SMS device with high performance is fusion spliced in the laser cavity, and the developed dispersion precisely managed the all-fiber structured mode-locked picosecond laser with a record-breaking wavelength tuning range from 1976 to 1916 nm while exerting axial strain on this SMS device. We experimentally explored the regularity between the strain and the central-wavelength shift of the mode-locked pulse, and for the first time to the best of the authors' knowledge, achieved the precise in-line axial strain measurement from 0 to 5385 µɛ by using the tunable ultrafast-laser-based sensor, and sensitivity is up to -11.5 pm/µɛ. With high compactness and durability, this sensor has advantages in real-time dynamic measurement over other passive devices, thus will undoubtedly find various application scenarios.