Optimizing the transmitter field of view of an alignment-free distributed-cavity laser incorporating cat-eye optics

To realize practical alignment-free distributed-cavity laser over a large dynamic range for adaptive laser wireless power transmission, experimental investigation was carried out based on an end-pumped Nd: GdVO₄ laser of cat-eye retroreflector. On the basis of compensating the spherical aberration and field curvature(FC) of the receiver, optimizing the laser working distance and field of view(FOV) of receiver, it was found that the out-of-focus of cat-eye retroreflector induced by FC of each lens at the transmitter was main factors for limiting FOV angle(off-axis tolerance at receiving end). FC of the transmitter was analyzed and calculated based on the Zemax software, aspherical lens with corrected FC was designed and fabricated to avoid the out-of-focus of the transmitter when the receiving end was off-axis, the purpose of improving the transmitter FOV was realized. Using the optimized design aspherical lens, the laser output power was over 50% of its maximum value at a long working distance of 5 m within transmitter FOV of 4.6° in the experiment. The result was enhanced significantly compared with that using the common spherical lens, but there was still a certain gap between the ideal designed value and the experimental results. It is considered that the optical aberration of the thermal lens of laser crystal is a key factor for further optimizing the FOV at the transmitter.