Generation of one-dimensional high-order Hermite-Gaussian laser beams with large mode volume br

Hermite-Gaussian (HG) beams have many important applications in the optical frontier, and the limitedoutput power of the high-purity HG beams is partly due to the small gain volume of the mode. The commonlyused off-axis end-pumped scheme offers a narrow gain volume whose diameter is about a hundred microns. Inthis work, a new method of generating the HG beams based on a slab resonator that has a large mode volume isproposed and experimentally demonstrated. According to the optical resonator theory, the intra-cavity modes inthickness and width direction of the slab resonator are restricted by inserting two size-adjustable apertures,respectively. The one-dimensional HG beam generation is mainly guaranteed by the size of the aperture alongthe thickness direction of the slab, which matches the diameter of the fundamental mode. The different orderone-dimensional HG beams are obtained by refined intra-cavity mode modulation. Since the higher-order modesare less sensitive to the misalignment of the cavity mirror than the lower-order modes, and the manipulation ofthe modes-loss at different orders is achieved by combining the tilt control of the coupled output mirror and thesize control of intra-cavity apertures. By adjusting the optical gain and loss in the resonant cavity, the singlemode wins the competition of laser modes. Therefore, high-purity one-dimensional HG beams with 0 to 9 orders(HG00 to HG09) are generated. The pump module is comprised of a two-dimensional laser diode array whichoffers face-pumping to the large surface of the slab, therefore the width of the mode volume is extended toseveral millimeters. By further incorporating the 100mm-level long slab, the total gain volume is much largerthan the counterpart in the off-axis pumping scheme. In this work, the output power of the highest order HG09mode increases up to 244 mW. Owing to the large gain volume and uniform gain distribution caused by theface-pumped slab, the purity of high order HG modes is quite good. The correlation coefficient between themeasured intensity distribution and the theoretical value is larger than 0.95. The beam quality factor isalso in good agreement with the theoretical one. Finally, a conversion from Hermite-Gaussian beams to thedonut-shaped Laguerre-Gaussian beams is realized by using an astigmatic mode converter. Hopefully, powerscaling of the HG beam output is also expected by employing cascaded slab amplifiers, and the approach in thispaper provides a novel solution for generation of high power HG beams