Coherent Beam Combining (CBC) can scale the overall output power while maintaining high beam quality. In recent years, this technique has also been employed to generate the high-power Optical Vortex Beam (OVB). In this work, we designed a coherent phased array, and an Optical Vortex Beam Array (OVBA) was generated via the CBC technique. Numerical simulation was studied, and an experimental setup was set up. The results showed that the OVBA could be generated in the far field. Meanwhile, the phase detection results indicated that the OVBA included several phase singularities. This work can present a new idea for manipulating the high power structured optical fields.
In this paper, an innovation coherent beam combining (CBC) architecture to generate the structured light beams array was proposed and experimented. The simulation and experimental results reveal that the optical vortex beams array (OVBA) with multi-modes can be generated effectively in the far field. The OVBA is composed of multiple sub-OVB in the intensity distribution. Furthermore, the number of OVBs can be modulated by changing the fill factor of the laser array in the near field. In particular, the performance of a OVBA copier was observed, which may deepen the understanding of creating the structured light fields by CBC technique. The experiment results were in excellent agreement with the simulation results. This work could provide valuable and practical reference on generation and manipulation of high power structured light beams
In this letter, a two-stage phase control technique is proposed to increase the control bandwidth of the target-in-the-loop (TIL) system. In this technique, the first stage phase control is enabled by LiNbO3 phase modulator to compensate the phase noises in the fiber amplifiers, and the second stage phase control is enabled by the liquid crystal (LC) to compensate the phase noises induced by the atmospheric turbulence. We built a TIL coherent beam combining system with 3-channel coherent fiber lasers over a 40 m atmospheric propagation path. In our experiment, the stochastic parallel gradient descent (SPGD) algorithm was employed for phase control. When the phase control system was in the close loop, the performance of laser beam projection was significantly improved, and the phase locking bandwidth for transmitter side phase distortions reached 1 kHz. This method can be used for applications such as energy transmission and free-space optical communication.
In this paper, a two-stage phase control method was proposed to increase the control bandwidth of the target-in-the-loop coherent beam combining (CBC) system. Firstly, the principle of the target-in-the-loop CBC system based on two-stage phase control was introduced. In order to verify the feasibility of two-stage phase control technology, then a 7-channel fiber laser array beam combining system was established. The experimental research showed that when the phase noise in the fibers and on the transmission path from the collimators was controlled by two phase controllers respectively, the laser array coherently combined in the far field stably. The power in bucket was 11.4% in the close-loop, which was 70.1% of the theoretical value. The normalized mean voltage detected by the photoelectric detector increased from 0.107 to 0.648, with an increase of 6.1 times. This experiment initially verified the feasibility of the two-stage phase control method, which will be helpful for the control bandwidth increasing in the target-in-the-loop CBC system.
We proposed a design of coherent fiber-optics-array collimator (CFAC) which is mainly composed of a single unitary collimating lens and prism. The CFAC system can be regarded as a “sub-aperture” of the whole fibers array in the tiledaperture scheme to expand combining channels efficiently due to its simple and compact structure. Then, we setup an experiment to verify the feasibility of the CFAC system with seven fiber lasers arranged in two dimensions and the CBC in 1064nm wavelength using single-frequency dithering algorithm is successfully achieved. By careful calculation, the residual errors among the laser beams are suppressed below λ/20 through an active-piston-phase control.
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