Abstract:
Background Hermite-Gaussian (HG) beams are fundamental orthogonal solutions of stable optical resonators, and their efficient conversion to Laguerre-Gaussian (LG) vortex beams provides an effective way to generate high-order vortex light. However, the direct intracavity generation of LG beams commonly suffers from chiral superposition and poor controllability, which limits its practical applications.
Purpose This paper aims to propose a scheme to achieve high-order tunable HG and LG laser output with stable chiral control, so as to solve the chiral superposition problem of directly generated LG beams.
Methods An 808 nm fiber-coupled laser diode was used to pump the Nd:YVO4 crystal in a plano-concave resonator. The pitch and tilt angles of the input mirror were precisely adjusted to realize off-axis pumping. A π/2 astigmatic mode converter composed of a pair of cylindrical lenses was adopted for external-cavity mode conversion. The orbital angular momentum and chirality of LG beams were verified by a Mach-Zehnder interferometer.
Results Continuously tunable HG0,n (1–68th order) and HG1,n (1–46th order) modes were obtained. The HG modes were efficiently converted into LG0,1 to LG0,68 vortex beams. The chiral symmetry flipping of LG0,1/LG0,-1 and LG0,68/LG0,-68 was realized by reversely adjusting the input mirror angles.
Conclusions The proposed scheme combines the high-order tunability of HG modes and the chiral controllability of LG modes without intracavity chiral elements, providing a flexible and reliable technical approach for the practical application of high-order vortex lasers.
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