Design of beam homogenizing device at receiving end for laser wireless power transmission

In the laser wireless power transmission, the ununiform distribution of laser light intensity and the mismatching of laser spot and photovoltaic cells shape will lead to the decrease of photoelectric conversion efficiency, local over temperature, and the damage of photovoltaic cells under extreme conditions. A laser receiver was designed based on the distributed homogenization method. Firstly, the light shaping diffuser was used to homogenize the beam in each sub-region of the photovoltaic cells, and then the optical tube was used for the second homogenization and beam shaping. For 1 cm×1 cm photovoltaic cells, the influence of the diffuse-angle of the laser shaping diffuser and the height of the optical tube on the beam homogenization effect was analyzed. The coupling efficiency η_c of the optimized laser receiver was more than 95%, and the light intensity nonuniformity Δ was less than 0.05. In addition, the laser receiver was not sensitive to the laser incident angle. When the incident angle was 20°, the coupling efficiency η_c was more than 80%. A laser wireless power transmission system based on 3×3 photovoltaic cells chip array was built. After using the designed laser receiver, the light intensity nonuniformity was reduced from 0.34 to 0.12, and the conversion efficiency of photovoltaic cell was improved by 65%. Compared with normal incidence of laser, the change of conversion efficiency was less than 20% when the laser incident angle was 18°. The results show that the laser receiver can effectively improve the light intensity uniformity at the receiver and the photoelectric conversion efficiency of the system. Meanwhile the laser receiver is insensitive to the laser incident angle. So the optical receiver can play an important role in laser wireless power transmission.