Coherent beam combining is a method to scale the peak and average power levels of laser systems beyond the limit of a single emitter system. This is achieved by stabilizing the relative optical phase ...of multiple lasers and combining them. We investigated the use of reinforcement learning (RL) and neural networks (NN) in this domain. Starting from a randomly initialized neural network, the system converged to a phase stabilization policy, which was comparable to a software implemented proportional-integral-derivative (PID) controller. Furthermore, we demonstrate the capability of neural networks to predict relative phase noise, which is one potential advantage of this method.
Coherent beam combining is a method for combining multiple emitters into one high power beam by means of relative phase stabilization. Usually, modulation or interferometric techniques are used to ...generate an error signal. This is relatively complicated and expensive. Especially in the case of tiled aperture combining the beam profile is usually monitored anyway. This beam profile should contain most of the information necessary for the stabilization as well but is usually not used because it is difficult to explicitly derive the correct actions from just the far-field image. Here we show that it is possible to derive a suitable control policy without any explicit modeling using deep reinforcement learning in a simulated environment.
We demonstrated an all-normal-dispersion nonlinear polarization rotation mode-locked Tm:ZBLAN fiber laser in the 2 μm wavelength band. All fibers in the experiment were ZBLAN fibers with normal ...dispersion in the wavelength band. An average power of 63 mW with a characteristic cat-ear shaped optical spectrum of an ANDi laser was obtained. The center wavelength and the spectral bandwidth were 1880 nm and ~80 nm, respectively. The repetition rate was 70.6 MHz and the corresponding pulse energy was 0.9 nJ. The pulse duration directly from the oscillator was 860 fs and it was compressed to 107 fs.
Collinear coherent combination of multiple single frequency fiber amplifiers is a promising approach to realize the high power laser sources required for 3rd generation gravitational wave detectors ...(GWD), as long as the stringent requirements on the beam quality and noise properties can be met. Here, we report the beam quality and noise properties of two coherently combined 10 W single frequency amplifiers with respect to the requirements of GWD. The combining efficiency was larger than 95% with 97% of the combined beam in the fundamental spatial mode. There was no significant noise increase compared to the fluctuations of the single amplifier.
Self-focusing is the ultimate power limit of single mode fiber amplifiers. As fiber technology is approaching this limit, ways to mitigate self-focusing are becoming more and more important. Here we ...show a theoretical analysis of this limitation in coupled multicore fibers. Significant scaling of the self-focusing limit is possible even for coupled multicore fibers if the out-of-phase mode is chosen. On the other hand the in-phase mode can - depending on the coupling strength - be prone to instabilities.
PDF
