4.05 kW monolithic fiber laser oscillator based on home-made large mode area fiber Bragg gratings

Abstract

With the increasing output power of the monolithic fiber laser oscillators, the stimulated Raman scattering (SRS) effect becomes one of the main limitations of power scaling. Employing fiber with a larger mode area is an effective technique to mitigate the SRS, but, for the monolithic fiber laser oscillators, the difficulty of the inscription of the high-reflection fiber Bragg gratings (FBGs) increases with the fiber mode area. In this work, we demonstrated a high-power monolithic fiber laser oscillator based on the home-made large mode area FBGs and ytterbium-doped fiber (YDF) with 25 μm core diameters. A maximum output power of 4.05 kW is achieved at the central wavelength of ∼1080 nm with a total 915 nm pump power of ∼6.7 kW. At the operation of 4.05 kW, the intensity of the Raman Stokes light is ∼25 dB below the signal laser, and the beam quality (M 2-factor) is ∼2.2. To the best of our knowledge, this is the first detailed report of the monolithic fiber laser oscillator with an output power beyond 4 kW.

Influence of fiber fusion on loss and beam quality in multi-mode injection conditions

“…In the simulation, the signal wavelength is selected to be 1064 nm, and the laser beam quality of the input fiber is limited to be between 1.3 and 1.4. According to the formulas (7) and ( 8), the M 2 value is directly related to the power ratio of each mode. For different sized fibers, the proportion of the fundamental mode will be different because of the different number of eigenmode.…”

“…With the advantages of high conversion efficiency, good beam quality, compactness and convenient heat management, fiber lasers are widely used in industrial and material processing [1][2][3]. Compared to the lasers with bulky spatial optical comp onents, fiber lasers with allfiber structure have outstanding structural advantages and have been rapidly developed in recent years [4][5][6][7][8][9]. With the increase of laser output power, the transverse mode instability (TMI) effect has gradually become a dominant limiting factor for power scaling.…”

Fabrication of high-power fiber Bragg grating in double-clad fiber by femtosecond laser plane-by-plane technology

“…Fiber Bragg grating (FBG) is an indispensable component of high-power fiber laser, which could be used as a cavity mirror. Currently, UV laser phase mask method has been demonstrated to fabricate high-power FBGs [1][2][3][4][5]. However, the process of hydrogen-loaded, removal and recoating would not only increase the fabrication time, but also degrade the mechanical strength of the obtained FBG, resulting in lower power of laser output.…”

The effect of population inversion saturation on the transverse mode instability threshold in high power fiber laser oscillators

“…To keep the increasing pace of the demand for their applications, people are removing the barriers to the power scaling of fiber laser systems. The power scaling of fiber amplifiers and oscillators has been faced with two major problems; transverse mode instability (TMI) 1 and stimulated Raman scattering (SRS) 2 , 3 . These destructive effects create serious constraints on the efficiency and beam quality of high-power fiber lasers in the last decade.…”