High-harmonic generation in submicron-thick chirped periodically poled thin-film lithium niobate

Lingzhi Peng; Xiaoni Li; Liqiang Liu; Yuanyuan Liu; Yuanyuan Zhao; Xuanming Duan; Lihong Hong; Zhiyuan Li

doi:10.1364/PRJ.558257

Photonics Research, Volume. 13, Issue 7, 1917(2025)

High-harmonic generation in submicron-thick chirped periodically poled thin-film lithium niobate

Lingzhi Peng¹, Xiaoni Li¹, Liqiang Liu¹, Yuanyuan Liu¹, Yuanyuan Zhao², Xuanming Duan², Lihong Hong^1,3,4、*, and Zhiyuan Li^1,5、*

Author Affiliations

¹School of Physics and Optoelectronics, South China University of Technology, Guangzhou 510641, China

²Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Institute of Photonics Technology, Jinan University, Guangzhou 511443, China

³State Key Laboratory of Ultra-intense Laser Science and Technology and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China

⁴e-mail: honglihong@siom.ac.cn

⁵e-mail: phzyli@scut.edu.cn

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Figures & Tables(6)

Fig. 1. (a) Schematic of broadband SHG, THG, and HHG via a pumped femtosecond pulse laser under the influence of cascaded χ(2) nonlinear up-conversion and χ(3) SPM. (b) Schematic of phase matching for SHG, THG, and HHG through QPM. β1 and βi represent the wave vectors of the FW and the ith harmonic, respectively. (c) Schematic of the TFLN waveguide structure used for HHG, with a thickness of 600 nm. (d) Optical microscope image of the poled TFLN surface after hydrofluoric acid etching. The green areas represent the reversed domains. (e) Variation of the TFLN poling period with propagation distance. (f) and (g) Calculated distributions of the deff as a function of the RLVs for the designed CPP-TFLN waveguide, along with the phase-mismatch curves for each HG during χ(2) nonlinear up-conversion.

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Fig. 2. HHG in the CPP-TFLN waveguide. (a) Schematic of the experimental setup for HHG. HWP, half-wave plate; POL, polarizer. (b) Photograph of the light pattern at the end of the TFLN waveguide. (c) Spectral broadening of the pump laser pulse as it propagates through the TFLN waveguide. (d) Broadband 2nd–8th HG in the TFLN waveguide with a pump energy of 1.2 μJ and a central wavelength of 2100 nm via cascaded χ(2) nonlinear frequency up-conversion and χ(3) SPM. (e) and (f) Simulation results of the output spectra. The red curve indicates the initial pump pulse.

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Fig. 3. Output harmonic spectrum in the unpoled TFLN waveguide with a pump energy of 1.2 μJ.

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Fig. 4. (a) Output spectra of the TFLN waveguide at varying pump energies. (b) Output spectra at a pump energy of 0.4 μJ for different pump center wavelengths. Note that each spectrum has been normalized to its maximum value.

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Fig. 5. (a) Variation of the poling period of waveguide B along the propagation direction. (b) The phase-mismatch curves for each HG during the χ(2) nonlinear up-conversion processes. (c) and (d) The phase-mismatch curves for 4th–6th HG during the χ(3) FWM processes. (e) Schematic diagram of QPM-THG where individual phase matching conditions for SHG or SFG are not satisfied. The gray arrows indicate phase mismatching. (f) The phase-mismatch curves for the direct 4th–6th HG processes. (g) Output spectrum of the TFLN waveguide with a pump energy of 1.2 μJ and a central wavelength of 2100 nm.

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Table 1. Wave Vector Mismatch (Δβ) for Different χ(2) Nonlinear Up-Conversion Processes Contributing to Each HG^a

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Table 1. Wave Vector Mismatch (Δβ) for Different χ(2) Nonlinear Up-Conversion Processes Contributing to Each HG^a

HHG	Phase Mismatching in Three-Wave Mixing Processes
2nd HG	$Δ β_{1} = β_{2} - 2 β_{1}$
3rd HG	$Δ β_{2} = β_{3} - β_{2} - β_{1}$
4th HG	$Δ β_{3} = β_{4} - β_{3} - β_{1}$ , $Δ β_{4} = β_{4} - 2 β_{2}$
5th HG	$Δ β_{5} = β_{5} - β_{4} - β_{1}$ , $Δ β_{6} = β_{5} - β_{3} - β_{2}$
6th HG	$Δ β_{7} = β_{6} - β_{5} - β_{1}$ , $Δ β_{8} = β_{6} - β_{4} - β_{2}$ , $Δ β_{9} = β_{6} - 2 β_{3}$
7th HG	$Δ β_{10} = β_{7} - β_{6} - β_{1}$ , $Δ β_{11} = β_{7} - β_{5} - β_{2}$ , $Δ β_{12} = β_{7} - β_{4} - β_{3}$
8th HG	$Δ β_{13} = β_{8} - β_{7} - β_{1}$ , $Δ β_{14} = β_{8} - β_{6} - β_{2}$ , $Δ β_{15} = β_{8} - β_{5} - β_{3}$ , $Δ β_{16} = β_{8} - 2 β_{4}$

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Lingzhi Peng, Xiaoni Li, Liqiang Liu, Yuanyuan Liu, Yuanyuan Zhao, Xuanming Duan, Lihong Hong, Zhiyuan Li, "High-harmonic generation in submicron-thick chirped periodically poled thin-film lithium niobate," Photonics Res. 13, 1917 (2025)

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Paper Information

Category: Nonlinear Optics

Received: Feb. 6, 2025

Accepted: Apr. 23, 2025

Published Online: Jul. 1, 2025

The Author Email: Lihong Hong (honglihong@siom.ac.cn), Zhiyuan Li (phzyli@scut.edu.cn)

DOI:10.1364/PRJ.558257

CSTR:32188.14.PRJ.558257

Topics

laser devices and laser physics

Lasers and Laser Optics

Laser physics

laser manufacturing

Instrumentation, Measurement and Metrology

Table 1. Wave Vector Mismatch (Δβ) for Different χ(2) Nonlinear Up-Conversion Processes Contributing to Each HGa

Table 1. Wave Vector Mismatch (Δβ) for Different χ(2) Nonlinear Up-Conversion Processes Contributing to Each HGa

Table 1. Wave Vector Mismatch (Δβ) for Different χ(2) Nonlinear Up-Conversion Processes Contributing to Each HG^a

Table 1. Wave Vector Mismatch (Δβ) for Different χ(2) Nonlinear Up-Conversion Processes Contributing to Each HG^a