The performance of high-power fiber lasers has rapidly improved over the years. Consequently, high-power fiber lasers have become instrumental in the development of industrial processes and national defense technologies. Researchers are attempting to further improve the output power of high-power fiber lasers, but inefficient transmission methods are limiting their widespread application. Free-space transmission introduces complex spatial optical paths, resulting in insufficient flexibility and stability. Therefore, the demand for high-power laser transmission based on flexible fibers is increasing. Traditional solid silica fibers are available for such applications. However the damage threshold and material nonlinearity eventually affect them and thereby limit the increases of transmission power and length. Moreover, the severe material absorption in the mid-infrared band and the large Rayleigh scattering loss at short wavelengths of silica materials limit the laser transmission range.

Hollow-core anti-resonant fibers (HC-ARFs) provide novel solutions for flexible high-power laser transmission by guiding light through air, a vacuum, or a gas-filled hollow core. Compared with solid-core fibers, HC-ARFs inherently reduce the overlap between the optical field and glass structure by five orders of magnitude, which results in low optical nonlinearity and a higher damage threshold. Recently, numerous multilayer structures have emerged, based on the knowledge of light-guiding mechanisms, which rapidly decrease the losses of HC-ARFs. The unique properties of these innovatively structured HC-ARFs offer significant potential in terms of transmission distance, flexibility, and power-handling capacity. In terms of their transmission bands, HC-ARFs regulate the operational window by adjusting the silica wall thickness. HC-ARFs overcome the transmission bandwidth of silica materials and realize laser transmission from the UV band to the mid-infrared band.

The rapid development of HC-ARFs has attracted extensive attention from researchers in the field of high-power laser transmission, and a series of breakthroughs have been achieved. Owing to the high damage threshold and low nonlinearity of HC-ARFs, most research teams focus on the enhancement of transmission power. Currently, in terms of continuous-wave laser transmission, 3 kW high-power laser transmission over 110 m and 1 kW high-power laser transmission over 1 km have been achieved using HC-ARFs. In terms of nanosecond high-energy laser transmission, 30 mJ single pulse energy transmission has been achieved using HC-ARFs. In terms of ultra-short pulse laser transmission with peak power, 20 GW of peak power transmission has been achieved using HC-ARFs. The above achievements fully demonstrate the enormous potential of HC-ARFs in the field of high-power laser transmission.

The implementation of high-power laser transmission in special wavelength bands based on HC-ARFs is also an important direction for development. In the mid-infrared band, HC-ARFs have good physicochemical properties and low absorption losses. Currently, an HC-ARF can achieve up to 6 µm wavelength guidance. In terms of high-power laser transmission, our team has exceeded 20 W average power in the 3.1 µm band using HC-ARFs. In the ultraviolet bands, HC-ARFs overcome the limit of Rayleigh scattering loss to achieve low loss transmission. Our team realized high power ultrashort pulse laser transmission in the UV band using HC-ARFs, achieving a peak power of 5.3 MW.

HC-ARFs have the characteristics of low nonlinearity, low dispersion, a high damage threshold, and a controllable number of transmission modes. High-power laser transmission based on HC-ARFs has become a research hotspot. With the improvement of the structural design and fabrication processes for HC-ARFs, the transmission losses of multiple important laser bands are significantly reduced. Research reports on high-power laser transmission based on HC-ARFs continue to emerge, and high-power continuous laser and pulse laser transmission from the ultraviolet to mid-infrared bands has been achieved. However, there is still significant space for improvement, such as further improving transmission power and efficiency and exploring full fiber integrated transmission methods under high power, among others. With the in-depth research and resolution of related technical difficulties, high-power laser transmission technology based on HC-ARFs will become a new generation of transmission solutions and thereby promote the rapid development of related application fields.