# Efficient single-pass third-harmonic generation at 520 nm for pumping doubly-resonant OPO

## TL;DR

This paper demonstrates an efficient single-pass third-harmonic generation process at 520 nm using PPKTP, enabling a tunable green laser suitable for pumping optical parametric oscillators and quantum optics applications.

## Contribution

It introduces a novel single-pass third-harmonic generation method at 520 nm with high efficiency, utilizing cascaded PPKTP and PPMgO:LN crystals, advancing laser source technology.

## Key findings

- Achieved ~545 mW 520 nm green laser output.
- Maximum doubling efficiency of 26.8%.
- Potential for quantum optics applications.

## Abstract

A ~545 mW single-frequency tunable 520 nm green laser has been demonstrated using a periodically-poled potassium titanyl phosphate (PPKTP) bulk crystal based on single-pass third-harmonic generation (THG) of a 1560 nm laser via single-pass second-harmonic generation (SHG) followed by single-pass sum-frequency generation (SFG). In single-pass SHG, two cascaded periodically-poled magnesium-oxide-doped lithium niobate (PPMgO:LN) crystals were used, and ~3.5 W 780.25 nm doubled laser output is produced, corresponding to maximum doubling efficiency of 26.8%. The system can provide a pump source (520 nm) for an optical parametric oscillator for two-color entangled continuous-variable optical field generation at 1560 and 780 nm and two-color local oscillators for homodyne detection.

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Source: https://tomesphere.com/paper/1702.06306