Improving the beam quality factor (M2) by phase-only reshaping of structured light

Laser brightness is crucial in many optical processes, and is optimized by high power, high beam quality (low M2) beams. Here we show how to improve the laser beam quality factor (reducing the M2) of arbitrary structured light fields in a lossless manner using continuous phase-only elements, thus allowing for the increase in brightness by a simple linear optical transformation. We demonstrate the principle with four high M2 initial beams, converting each to a Gaussian (M2≈1) with a dramatic increase in brightness of >10×. This work puts a new (to the best of our knowledge) perspective on the old debate of improving laser beam quality with binary diffractive optics, while providing a practical approach to enhancing laser brightness for arbitrary input beams.