Broadband Second Harmonic Generation using Fixed-Period Periodically Poled Lithium Niobate

TL;DR

This paper demonstrates a practical method to achieve broadband second harmonic generation using standard periodically poled lithium niobate by angle tuning, significantly enhancing bandwidth without custom fabrication.

Contribution

It introduces a novel approach of using fixed-period PPLN with angle tuning to realize broadband SHG, avoiding complex aperiodic structures.

Findings

1. Achieved 1.6x increase in SHG bandwidth.

2. Demonstrated effective angle tuning over various incident angles.

3. Validated the practicality of using standard PPLN for broadband SHG.

Abstract

Periodically poled lithium niobate (PPLN) is a widely used nonlinear optical device for second harmonic generation (SHG). Despite its wide adoption in commercial systems, its bandwidth for SHG is fundamentally limited by the quasi-phase matching condition. This can be overcome by aperiodic or chirped PPLN structures; however, such devices are typically custom-fabricated and not readily available commercially. In this study, we investigate an alternative approach to achieving broadband SHG by using a standard PPLN crystal containing multiple fixed poling periods. Broadband operation is realized by angle tuning the crystal relative to input beam in free-space. The effect of angle tuning is examined over a range of incident angles, and an 1.6x enhancement in SHG bandwidth is demonstrated. These results suggest a practical and efficient strategy for broadband SHG using standard PPLN devices.