Passive Coherent Beam Combination of Four Yb-Doped Fiber Lasers in Two-Dimensional Distribution

Passive coherent combination of all-fiber multichannel pulsed laser based on optical feed-back ring cavity

“…the intensity pattern is stable and does not change in long-time observation. Fig.7 shows the output centre wavelength 1063.4nm at close loop, coherent output of multi-wave isn't observed as references [17] . The spatial configuration of references [21] has optical feed-back ring cavity with the highest output power , but the energy of central lode is only 18%.Compared to the report about CBC with optical feed-back ring cavity based on the spatial configuration of aperture filling [9][10][14][15][16][17][18][19][20][24][25][26][27] , the all-fiber configuration can realize coaxial coherent combination, and maintain near-diffraction-limited beam quality.…”

“…The original CBC of pulsed all-fiber laser has been reported based on Mach-Zehnder interferometer geometry as references [24,25], two pulsed fiber laser are combined at low output power, for output power 17.6mW and 94mW,and the references [25] has optical feedback ring cavity, however the pulses generate from mode-locked fiber laser with semiconductor saturable ab-sorber mirror (SESAM).Up to now most the report about CBC with optical feed-back ring cavity based on the spatial configuration of aperture filling [9][10][14][15][16][17][18][19][20][21][26][27] .The fill-factor, which is the ratio of the collimated beam waist diameter to the distance between adjacent beams, have important effect in the laser array. The fill-factor is always less than 1 for gauss distribution of the output pulsed fiber laser, so energy dissipation to side lode is inevitable and the beam quality of the coherently combined beam is thus degenerated [28] .…”

“…Passive CBC relies on self-phase locking via passive coupling mechanisms to combine lasers coherently, which has simple and stable configuration. There are many reports on passive phase-locked techniques such as self-Fourier laser cavity [9,10] ,self-organization mutual injection locking lasers mechanism in fiber laser arrays [11,12,13] and optical feed-back ring cavity [14][15][16][17][18][19][20][21] .The highest output power 1090W of passive coherent beam combination is obtained with optical feed-back ring cavity [21] .However, the research of CBC is mainly focus on CW fiber laser, CBC of pulsed fiber laser is more complicated owing to the difficulty of in-phase detection and controll [22,23] .…”

“…Coherent beam combination(CBC) and incoherent beam combination provide one of the feasible solutions for further power scaling [5] .CBC can be classified into two categories: active phasing [5,6,7,8] and passive phasing [9][10][11][12][13][14][15][16][17][18][19] . Active CBC phasing uses electronic feedback to control the phases of the array elements, which requires complicated phase detection and phase modulation for each element of the array.What's more,the narrow linewidth is essential provided by the seed source [6,7] .…”