Highly scalable femtosecond coherent beam combining demonstrated with 19 fibers

Abstract

Coherent beam combining in the femtosecond regime of a record number of 19 fibers is demonstrated. The interferometric phase measurement technique, particularly well suited to phase-lock a very large number of fibers, is successfully demonstrated in the femtosecond regime. A servo loop is implemented to control piezoelectric fiber stretchers for both phase and delay variation compensation. The residual phase errors are below λ/60 rms. Nearly 50% of the total energy is contained in the far-field central lobe. After compression, we obtain a combined pulse width of 300 fs identical to the master oscillator pulse width.

10.4 kW coherently combined ultrafast fiber laser

“…Fiber lasers are well suited for CBC due to their reproducible and simple setup. Numerous techniques for CBC of fiber amplifiers have been demonstrated, such as tiled-aperture combining based on diffraction [8] and filled-aperture combining using diffractive optical elements [9], dielectric polarization [10], and intensity beam splitters [11]. For Gaussian beams, filled-aperture combining is more efficient and hence preferred over tiled-aperture combining at theoretical maximum efficiencies of 100% and 68% [12].…”

Phase measurement of a segmented wave front using PISton and TILt interferometry (PISTIL)

“…Taking into account the metrological results presented in Table 1, we estimate that PISTIL interferometer has reached a sufficient maturity to be tested on XCAN demonstrator [20,21]. This laser system is based on the coherent combination of several tens of femtosecond laser beams produced through a network of amplifying optical fibers.…”

Towards Ultimate High-Power Scaling: Coherent Beam Combining of Fiber Lasers

“…It is reported that the combining efficiency of multiple Gaussian laser beams via tiled aperture geometry at the ideal case is theoretically limited to 76% [145]. The highest achieved efficiency for CBC of pulsed lasers has been reported as 50% by a coherent combination of 19 femtosecond lasers with residual phase errors lower than λ/60 RMS [146]. In the CW regime, the efficiency of 58% has been achieved by CBC of eight CW fiber amplifiers with a total output power of 4 kW [147].…”

“…achieved efficiency for CBC of pulsed lasers has been reported as 50% by a coherent combination of 19 femtosecond lasers with residual phase errors lower than λ∕60 RMS [146]. In the CW regime, the efficiency of 58% has been achieved by CBC of eight CW fiber amplifiers with a total output power of 4 kW [147].…”