Integration of an anti-resonant hollow-core fiber with a multimode Yb-doped fiber for high power near-diffraction-limited laser operation

Abstract

We proposed and demonstrated mode cleaning in a high-power fiber laser by integrating an anti-resonant hollow-core fiber (AR-HCF) into a multimode laser cavity of an ytterbium (Yb)-doped fiber (YDF). An in-house mode-matched AR-HCF was fusion-spliced to a commercial multimode LMA-YDF, ensuring efficient fundamental mode coupling. The AR-HCF inflicts a high propagation loss selectively on higher-order modes, facilitating fundamental mode operation. Thus, the AR-HCF works as an efficient spatial mode filter embedded in the multimode fiber laser cavity and reinforces preferential amplification of the fundamental mode. Beam quality factor enhancement was achieved from M2 = 2.09 to 1.39 at an output power of 57.7 W (pump-power limited). The beam quality can be further improved by refining the AR-HCF fabrication. The proposed technique has a great potential to be exploited in other multimode fiber laser cavities involving erbium- or thulium-doped fibers and obviates the need for complicated specialty active fiber designs. Compared with the commonly used fiber bending technique, our method can achieve an efficient higher-order mode suppression without inducing mode-field deterioration.

Flexible beam delivery of ultrafast laser through vacuum-pumped anti-resonant hollow-core fiber

“…The low transmission loss is the combined result of the control of capillary and inter-capillary spacing consistency during the fiber drawing process as shown in Figure 1C. Measured transmit loss is 0.11 dB/m at 1,030 nm, which is much higher than the theoretical value, despite this, it shows an improvement comparison with a similar-structure seven capillaries AR-HCF in the most recent published article [40]. It is worth mentioning that the measured Frontiers in Physics frontiersin.org transmission loss of HCFs is related fiber parameters such as core size, capillary diameter, and wall thickness; fiber drawing quality such as roughness; attenuation measurement methods such as fiber length, light source quality, etc.…”

Functional Fibers and Functional Fiber-Based Components for High-Power Lasers

“…AR-HCF is one of the most popular microstructure fibers according to the emerging results reported recently. High-power pulse delivery employing AR-HCFs has been a well-known topic, it appears that researchers are turning more and more attention to its CW delivery applications [371][372][373][374][375][376][377][378][379][380][381][382][383].…”

“…d Longitudinal and transverse perspectives of AR-HCF fusion spliced with gain fiber for high-power delivery; Reproduced with permission from Ref. [383], Copyright 2022, Optica. (© 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement).…”

“…Typically, the function of both the CT-FBGs and LP-FBGs is to convert the core-guided light at unwanted Raman 1st-Stokes wavelength to the cladding-light and then strip it out to suppress the SRS effect. The CT-FBG evolves from the predecessor of tilted FBG under the chirp modulation [385,386,[382][383][384][385][386][387][388][389][390], which is inscribed in large-mode-area fibers by using the side-writing technique with phase masks. Through the writing process, the phase mask rotates to generate a specific tilted angle, as shown in Fig.…”

The Research on Large-Mode-Area Anti-Bending, Polarization-Insensitive, and Non-Resonant Optical Fibers

“…ARF can be categorized into an all-solid-state and hollow-core [9][10][11][12][13]. All-solid-state ARF has relatively high requirements for material doping [14][15][16][17] and fabrication processes.…”