Dual-wavelength vortex beam with high stability in diode-pumped Yb:CaGdAlO4 Laser

TL;DR

This paper demonstrates a stable dual-wavelength vortex beam with high orbital angular momentum stability in a diode-pumped Yb:CaGdAlO4 laser, useful for advanced spectroscopy and interferometry applications.

Contribution

It introduces a method to generate a stable dual-wavelength vortex beam with high OAM stability in Yb:CALGO laser, controlled by pump power and off-axis loss.

Findings

Stable operation for over three hours.

Dual spectral peaks separated by 3.01 THz.

Potential for applications in Terahertz spectroscopy.

Abstract

We present a stable dual-wavelength vortex beam carrying orbital angular momentum (OAM) with two spectral peaks separated by a few terahertz in diode-pumped Yb:CaGdAlO4 (CALGO) laser. The dual-wavelength spectrum is controlled by the pump power and off-axis loss in laser resonator, arising from the broad emission bandwidth of Yb:CALGO. The OAM beam is obtained by a pair of cylindrical lens that serves as an {\pi}/2 convertor for the high-order Hermite-Gaussian modes. The stability is verifed that the 1 h OAM beam with two spectral peaks at 1046.1 nm and 1057.2 nm (3.01 THz interval) can steadily operate for more than three hours. It has great potential for scaling the application for OAM beams in Terahertz spectroscopy, high-resolution interferometry, and so on.