We report a high-power broadband flat supercontinuum laser system based on a large-mode-area (LMA) low-loss fluorotellurite fiber cascaded with an LMA chalcogenide fiber. To effectively expand the coverage of the mid-infrared supercontinuum spectrum and enhance its flatness, a novel femtosecond Raman-soliton laser with high peak power is used as the pump source. When pumping the fluorotellurite fiber, a supercontinuum extended to 4.2 μm can be obtained, with an output power of 8.12 W. Subsequently, we further pumped an LMA As2S3 fiber. At the maximum input power, the output power of the supercontinuum can reach 2.6 W, with the spectral edge extending to 5.7 μm, a 10-dB bandwidth spanning 2–4.7 μm and favorable power stability retained. To the best of our knowledge, this is the first laser system that uses a fluorotellurite fiber as a transition fiber and further cascades the chalcogenide fiber to generate mid- and long-wave infrared supercontinuum, achieving the highest output power of a mid- to long-wave infrared supercontinuum laser generated in As2S3 fiber reported to date.

Transverse mode instability (TMI) is a primary limitation for power scaling in high-brightness fiber lasers. This paper reports observation of the TMI effect in the process of supercontinuum generation, and demonstrates a 993 W linearly polarized supercontinuum ranging from 800 to 2000 nm through an amplifier-based structure. To mitigate TMI, three strategies are implemented: repetition rate doubling to reduce peak power and mitigate the thermal loading; reducing the bending radius of the gain fiber to suppress higher-order modes; optimizing the polarization extinction ratio of the pre-amplifier. TMI-induced beam quality degradation and power-scaling limitation resemble those of conventional fiber lasers. In particular, burr-like spectral fluctuations in supercontinuum sources are observed upon the onset of TMI. This work deepens the understanding of TMI mechanisms in broadband laser systems and offers critical guidance for power scaling of high-power supercontinuum sources.

We present a compact and cost-effective mJ-level femtosecond laser system operating at a center wavelength of approximately 2.15 μm. An affordable two-stage ytterbium-doped yttrium aluminum garnet (Yb:YAG) chirped pulse amplifier provides more than 10 mJ, approximately 1.2 ps pulses at 1030 nm to pump a three-stage optical parametric chirped pulse amplifier (OPCPA) based on bismuth borate crystals and to drive the supercontinuum seed in the YAG crystal. The energy of the amplified pulses in the wavelength range of 1.95–2.4 μm reached 2.25 mJ with a pump-to-signal conversion efficiency of approximately 25% in the last OPCPA stage. These pulses were compressed to 38 fs in a pair of Suprasil 300 glass prisms.

We demonstrate an all-fiber high-power linearly polarized supercontinuum source with polarization-maintaining photonic crystal fibers (PM-PCFs) as the nonlinear medium. The source exhibits an average output power of 3.8 W with a flat spectrum from 480 nm to 2100 nm at the $-$10 dB level, except for the residual pump peak. The polarization extinction ratio (PER) is measured to be greater than 20 dB at selected sample wavelength points (532 nm, 1064 nm and 1550 nm) at the highest pump power level and greater than 20 dB at all wavelengths from 800 nm to 1500 nm at the low pump power level. We also experimentally study the spectral properties when the pump light propagates along different axes of the PM-PCF. The results show that propagating parallel to the slow axis enables a broader spectrum in the PM-PCF in this case, probably due to matching of the dispersion properties with the pump light, which is qualitatively in accordance with the numerical simulation. To our best knowledge, this is the first demonstration of a watt-level linearly polarized supercontinuum source generated from PM-PCFs in an all-fiber structure.