Work

Spiral-chirped nonlinear photonics enabling broadband orbital angular momentum second harmonic generation

Year: 2025

Type: article

Abstract: We demonstrate a nonlinear frequency conversion strategy that transforms a Gaussian fundamental beam (carrying no orbital angular momentum, OAM) into a second-harmonic (SH) vortex wave with engineered OAM across an ultrabroad bandwidth. By implementing spiral-chirped quasi-phase-matching (QPM) in a femtosecond-laser-poled Sr 0.61 Ba 0.39 Nb 2 O 6 (SBN) crystal, our system simultaneously imposes an azimuthal phase modulation to generate OAM in the SH wave and a longitudinal period chirp to achieve spectral broadening. This dual modulation converts collimated Gaussian beams (1200–1300 nm) into OAM-entrained SH vortices, exhibiting a spectral acceptance bandwidth significantly surpassing conventional helical-phase-matched systems while maintaining stable efficiency. This controllable second-harmonic OAM generation method opens new possibilities for applications including tunable structured light sources, high-capacity optical imaging using OAM multiplexing, and quantum light generation with tailored spectral properties, pushing forward the field of nonlinear optics that combines spectral and spatial control.

Source: Optics Express

DOI: 10.1364/oe.565198

Authors: Chen Yu, Tianxiang Xu, Ruwei Zhao, Shan Liu, Yan Sheng

Institution: Australian National University

Language: English

Topic: Orbital Angular Momentum in Optics

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,270

Funders: National Natural Science Foundation of China, Australian Research Council, K. C. Wong Magna Fund in Ningbo University, Natural Science Foundation of Zhejiang Province