The paper presents an efficient approach to generating green light using thin-film lithium niobate (TFLN) waveguides with combined modal phase-matching (MPM) and quasi-phase-matching (QPM) techniques. By leveraging both techniques within a single waveguide, the researchers achieved second harmonic generation (SHG) and third harmonic generation (THG) for green light under continuous-wave (CW) pumping. The SHG occurs between fundamental transverse electric (TE) modes, while THG is phase-matched with the higher-order TE20 mode. The device demonstrated high normalized conversion efficiencies: 795%W−1cm−2 for SHG and 2,775%W−2cm−4 for THG, with SHG reaching milliwatt power levels and THG achieving microwatt power levels.
The study optimizes the waveguide geometry to achieve simultaneous phase matching for both SHG and THG using a single poling period, avoiding the complexity of multi-periodic poling. This compact design is beneficial for applications in quantum optics, bio-imaging, and advanced display technologies.
In addition to experimental results, theoretical analysis of nonlinear conversion processes was conducted, estimating the normalized conversion efficiencies and comparing them with experimental data. The device was fabricated using standard nanofabrication techniques, and the stability of the periodically poled regions was tested over time. The experimental setup demonstrated the generation of green light and verified the mode profiles for both SHG and THG.
This work demonstrates the potential of TFLN waveguides for efficient green-light generation with high conversion efficiency, providing a foundation for future nonlinear frequency conversion applications in integrated photonics.
OMeda (Shanghai Omedasemi Co.,Ltd) was founded in 2021 by 3 doctors with more than 10 years of experience in nanpfabrication. It currently has 15 employees and has rich experience in nanofabrication (coating, lithography, etching, two-photon printing, bonding) and other processes. We support nanofabrication of 4/6/8-inch wafers.
