High-Power 2–4.8 μ m Supercontinuum Laser Generation in Precisely Tapered Fluorotellurite Fiber

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 TeO2-BaF2-Y2O3 and TeO2 modified fluoroaluminate glasses with good water resistance and high transition temperature (∼424°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 ∼15.9 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.

Ultra-broadband supercontinuum (SC) lasers covering the mid-infrared (MIR) region have significant applications in trace substance detection, national defense, and biomedical fields. Currently, high-power SC spanning 2–5 μm is still dominated by traditional fluoride (InF3) fibers. Although tellurite fibers, with their excellent chemical and thermal stability, have demonstrated significantly higher power scalability compared to other MIR fibers, their spectral broadening capabilities in the 4–5 μm region remain largely unexplored. Here, we demonstrate a >10 W ultra-broadband flat SC spanning the 1.8–5.1 μm spectral range in a fluorotellurite fiber using a cascaded soliton self-frequency shifting technique. The fluorotellurite fiber is precisely tapered to reconstruct dispersion and nonlinearity, which facilitates the evolution of the pre-stage Raman soliton into higher-order solitons, thereby enabling a new round of “rapid relay fission.” At a low pump power of 7.5 W, we also achieved a high-power (0.5 W) Raman soliton (60 fs) at 4.3 μm. These results, for the first time, to our knowledge, demonstrate that tapered fluorotellurite fibers can be used for high-power femtosecond pulse generation beyond 4 μm and high-power SC generation beyond 5 μm, establishing them as an exceptional nonlinear medium for the development of high-power MIR fiber lasers in the 4–5 μm spectral region.

In this Letter, we report an ultraflat high-power supercontinuum (SC) based on a low-loss short-length fluorotellurite fiber. A novel high-peak power dual-Raman soliton femtosecond laser is used as a pump source, which effectively extends the mid-infrared SC spectral range and enhances the flatness of the SC. Finally, we obtained a 10.4 W SC laser source with a spectral range from 1.8 to 4.2 µm in a 34 µm fluorotellurite fiber; the 5 dB bandwidth of the source completely covers 1.9-4.05 µm. To the best of our knowledge, this is the first report of a high-power SC generated in a fluorotellurite fiber with a flat spectral edge of >4 µm. This result highlights the fluorotellurite fiber's spectral broadening capabilities under high-power conditions, demonstrating performance on par with that of ZBLAN fibers.

We demonstrate mid-infrared ultraflat broadband supercontinuum (SC) generation in a 40 cm long tapered fluorotellurite fiber pumped by a Raman soliton source. By tapering the end of the large-core-diameter fluorotellurite fiber, the dispersion is regulated and the nonlinear effect is enhanced, which effectively extends the mid-infrared SC spectral range and increases the spectral flatness. Finally, we obtained an SC light source with a spectral range from 1.8 to 4.7 μm; the 10 dB bandwidth of the source completely covers 1.88–4.22 μm, which has the farthest flat spectral edge in fluorotellurite fibers. The output power of the SC laser is about 1.04 W, and the power ratio of those above 3 μm in the spectrum to the total SC is ~24%. The optical-to-optical conversion efficiency is about 75%. Our results show that tapering of fluorotellurite fiber is an effective method to further extend and flatten the mid-infrared SC.

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Broadband supercontinuum laser sources in the mid-infrared region have attracted enormous interest and found significant applications in spectroscopy, imaging, sensing, defense, and security. Despite recent advances in mid-infrared supercontinuum laser sources using infrared fibers, the average power of those laser sources is limited to 10-watt-level, and further power scaling to over 50 W (or hundred-watt-level) remains a significant technological challenge. Here, we report an over 50 W all-fiber mid-infrared supercontinuum laser source with a spectral range from 1220 to 3740 nm, by using low loss (<0.1 dB/m) fluorotellurite fibers we developed as the nonlinear medium and a tilted fusion splicing method for reducing the reflection from the fluorotellurite-silica fiber joint. Furthermore, the scalability of all-fiber mid-infrared supercontinuum laser sources using fluorotellurite fibers is analyzed by considering thermal effects and optical damage, which verifies its potential of power scaling to hundred-watt-level. Our results pave the way for realizing all-fiber hundred-watt-level mid-infrared lasers for real applications.

We report on an intracavity configuration for supercontinuum generation in a Q-switched Yb fiber laser. The supercontinuum laser includes a section of microstructured fiber within the Q-switched laser cavity. With 380 mW of pump power, the supercontinuum laser can emit broadband pulses of 6 microJ energy and 10 ns temporal width, at repetition rates from few hertz up to 2 kHz. The supercontinuum spectrum spans over a wavelength range in excess of 1.4 microm.

A 3-5 µm mid-infrared (MIR) laser has a wide range of applications in biological tissue ablation, remote spectral fingerprint recognition, and directional infrared countermeasures. However, the performance of conventional MIR lasers has long been hindered by restricted wavelength radiation, spectral power efficiency, and system stability. Here, a highly efficient, compact, and stable MIR light source is reported, which is directly generated from a supercontinuum (SC) laser with a long wavelength edge of 4.2 µm in a 7 µm core diameter fluorotellurite fiber. Based on the integration of a high-peak-power pump light source and a small-core-diameter nonlinear medium, efficient nonlinear frequency conversion from traditional near-infrared laser to mid-infrared laser has been achieved, resulting in a significantly enhanced MIR spectrum of 3.7 µm, exceeding the pump peak of 2 µm by more than 12 dB. The pump conversion efficiency is 50.8%, with 94.3% of the spectral power distributed above 2.4 µm and 71.4% above 3 µm. This study has opened up a feasible avenue for obtaining high-efficiency mid-infrared band lasers that meet practical application needs.

An all-fiber supercontinuum laser source with a piece of highly nonlinear fiber inserted into a mode-locked fiber laser is experimentally demonstrated. This laser achieves mode-locking based on the Mamyshev mechanism and realizes supercontinuum generation spanning from 1330 nm to 2030 nm directly. Mode-locking based on the Mamyshev mechanism can be obtained easily, and the influence of the parameters of the laser cavity on the supercontinuum laser source is investigated. This supercontinuum laser source has a simple structure, and no amplifier stages are required. It demonstrates intracavity supercontinuum generation in mode-locked fiber laser based on the Mamyshev mechanism and exploits its operation further.

We demonstrated 10.4 W mid-infrared supercontinuum laser source, and ultrabroadband supercontinuum generation from 600 nm to 5.2 μm in newly-developed all-solid fluorotellurite fibers.