High power mid-infrared supercontinuum (SC) laser sources are important for a wide range of applications in sensing, spectroscopy, imaging, defense, and security. Despite recent advances on high power mid-infrared SC laser sources using fluoride fibers, the lack of mid-infrared fibers with good chemical and thermal stability remains a significant technological challenge. Here we show that all solid fluorotellurite fibers we developed can be used as the nonlinear media for constructing 10-W-level mid-infrared SC laser sources. All solid fluorotellurite fibers are fabricated by using a rod-in-tube method. The core and cladding materials are ${\mathrm{TeO}}_2\text{-}{\mathrm{BaF}}_2\text{-}{\mathrm{Y}}_2{\mathrm{O}}_3$ and ${\mathrm{TeO}}_2$ modified fluoroaluminate glasses with good water resistance and high transition temperature ($\sim 424°\mathrm{C}$). By using a 60 cm long fluorotellurite fiber with a core diameter of 6.8 μm as the nonlinear medium and a high power 1980 nm femtosecond fiber laser as the pump source, we obtain 10.4 W SC generation from 947 to 3934 nm in the fiber for a pump power of $\sim 15.9\mathrm{W}$, and the corresponding optical-to-optical conversion efficiency is about 65%. The spectral broadening is caused by self-phase modulation, soliton fission, soliton self-frequency shift, and dispersive wave generation. Our results show that all solid fluorotellurite fiber can be used for constructing high power mid-infrared SC laser sources for real applications.

We demonstrated a passively mode-locked erbium-doped fiber laser by using gold nanorods as a saturable absorber. The gold nanorods (GNRs) were mixed with sodium carboxymethylcellulose (NaCMC) to form GNRs-NaCMC films. By inserting one of the GNRs-NaCMC films into an EDFL cavity pumped by a 980 nm laser diode, stable passively mode-locking was achieved with a threshold pump power of ∼54 mW, and 12 ps pulses at 1561 nm with a repetition rate of 34.7 MHz and a maximum average power of ∼2.05 mW were obtained for a pump power of ∼62 mW.

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Heavily erbium-doped low-hydroxyl fluorotellurite glasses with molar compositions of (85.7−x)TeO₂ + xBaF₂ + 4.8Na₂CO₃ + 9.5Er₂O₃ (x = 38.1, 28.6, 19) were fabricated. The maximum doping concentration of erbium ions was up to 19 mol % by introducing BaF₂ into the tellurite glass system. Under 980 nm excitation, intense emissions around 2.7 μm from the ⁴I_11/2 → ⁴I_13/2 transition of Er³⁺ ions were observed in these glasses. The efficient mid-infrared emission can be attributed to the existence of cross relaxation (CR) ⁴I_13/2 → ⁴I_15/2 (Er³⁺): ⁴I_13/2 → ⁴I_9/2 (Er³⁺) caused by high erbium concentration, low hydroxyl content, and low phonon energy. The stimulated emission cross section at 2.7 μm of 47.6TeO₂ + 38.1BaF₂ + 4.8Na₂CO₃ + 9.5Er₂O₃ glass was calculated as 1.94 × 10⁻²⁰ cm². Our results indicate that it is a promising gain medium for 2.7 μm lasers.

Holmium (${\mathrm{Ho}}^{3+}$)-doped fluorotellurite microstructured fibers based on ${\mathrm{TeO}}_2–{\mathrm{BaF}}_2–{\mathrm{Y}}_2{\mathrm{O}}_3$ glasses are fabricated by using a rod-in-tube method. By using a 1.992 μm fiber laser as the pump source, lasing at 2.077 μm is obtained from a 27 cm long ${\mathrm{Ho}}^{3+}$-doped fluorotellurite microstructured fiber. The maximum unsaturated power is about 161 mW and the corresponding slope efficiency is up to 67.4%. The influence of fiber length on lasing at 2.1 μm is also investigated. Our results show that ${\mathrm{Ho}}^{3+}$-doped fluorotellurite microstructured fibers are promising gain media for 2.1 μm laser applications.

NaYF₄:Er³⁺,Yb³⁺,Ce³⁺ nanocrystals (NCs) were synthesized by using a solvothermal approach. Under the excitation of a 980 nm laser, the 1.53 μm emission band of Er³⁺ ions in the NCs was enhanced by 6 times after codoping Ce³⁺ ions owing to the efficient energy transfer between Ce³⁺ and Er³⁺: ⁴I_11/2 (Er^{3 +}) + ²F_5/2 (Ce³⁺) → ⁴I_13/2 (Er³⁺) + ²F_7/2 (Ce³⁺). By dispersing the NaYF₄:Er³⁺,Yb³⁺,Ce³⁺ NCs into SU-8 2005 polymer matrix, we constructed Er³⁺-doped polymer-based optical waveguide amplifiers (EDPOWAs) and measured their performances. The measured optical gain of the EDPOWA doped with NaYF₄: Er³⁺,Yb³⁺,Ce³⁺ NCs was enhanced by ~2dB in comparison with that doped with NaYF₄:Er³⁺,Yb³⁺ NCs. These results showed that NaYF₄:Er³⁺,Yb³⁺,Ce³⁺ NCs are promising candidates for building high gain EDPOWAs.