Single-pass, second harmonic generation of ultrafast, higher order vector vortex beams at blue

TL;DR

This paper demonstrates a novel single-pass method for second harmonic generation of ultrafast, high-order vector vortex beams in the blue spectrum, achieving high power and preserving beam quality.

Contribution

The study introduces a new experimental scheme for efficient, high-order vector vortex beam SHG in a single pass, applicable across the electromagnetic spectrum.

Findings

Generated vector vortex beams up to order lp=12 at 860 mW.

Frequency-doubled beams reached order lsh=24 with 20.5 mW power.

Achieved 2.4% SHG efficiency in a single pass.

Abstract

We report a novel experimental scheme for single-pass second harmonic generation (SHG) of vector vortex beam in the blue. Using an ultrafast Ti:Sapphire laser of pulse width ~17 fs and a set of spiral phase plates in polarization based Mach-Zehnder interferometer (MZI) we have generated vector vortex beams of order as high as lp = 12 at an average power of 860 mW. Given the space-variant polarization of the vector vortex beam, and the dependence of nonlinear frequency conversion processes on the polarization of the interacting beams, using two contiguous bismuth borate crystals with optic axis orthogonal to each other, we have frequency-doubled the near-IR vector vortex beam into visible vector vortex beams with order as high as lsh=24. The maximum output power of the vector vortex beam of order, lsh =2 is measured be as high as 20.5 mW at a single-pass SHG efficiency of 2.4 %. Controlling the temporal delay in the MZI, we have preserved the vector vortex nature of the beams at both pump and frequency-doubled beams at ultrafast timescales. The measurement on mode purity confirms the generation of high quality vector vortex beams at pump and SHG wavelengths. The generic experimental scheme can be used to generate vector vortex beams across the electromagnetic spectrum.