Phase Matching via Plasmonic Modal Dispersion for Third Harmonic Generation. Issue 21 (5th June 2022)

• Record Type: Journal Article
• Authors: Wang, Zhe; Wang, Zhe; Kalathingal, Vijith; Ho, Yi Wei; Hoang, Thanh Xuan; Chu, Hong‐Son; Guo, Yongxin; Viana‐Gomes, José C.; Eda, Goki; Nijhuis, Christian A.
• Is Part Of: Advanced science. Volume 9:Issue 21(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-06-05
• Subjects: modal phase matching -- nonlinear polymers -- plasmonic modes -- plasmonic waveguides -- third‐harmonic generation -- two‐wire transmission lines; Science -- Periodicals; 505
• DOI: 10.1002/advs.202201180
• Languages: English
• ISSNs: 2198-3844

Abstract

Abstract: The overall effectiveness of nonlinear optical processes along extended nonlinear media highly depends on the fulfillment of the phase‐matching condition for pump and generated fields. This is traditionally accomplished by exploiting the birefringence of nonlinear crystals requiring long interaction lengths (cm‐scale). For nonbirefringent media and integrated photonic devices, modal phase matching can compensate the index mismatch. Here, the various interacting waves propagate in transverse modes with appropriate phase velocities, but they suffer from a low refractive index contrast and cm‐scale interaction lengths. This work harnesses modal phase matching for third‐harmonic generation (THG) in plasmonic waveguides using an organic polymer (poly[3‐hexylthiophene‐2, 5‐diyl]) as the nonlinear medium. One demonstrates experimentally an effective interaction area as small as ≈ 0.11 µm 2 and the phase‐matched modal dispersion results in THG efficiency as high as ≈ 10 –3 W ‐2 within an effective length scale of ≈ 4.3 µm. THG also shows a strong correlation with the polarization of the incident laser beam, corresponding to the excitation of the antisymmetric plasmonic modes, corroborating that plasmonic modal phase matching is achieved. This large reduction in device area of orders of magnitude is interesting for various applications where space is critical (e.g., device integration or on‐chip applications). Abstract : Plasmonic modal dispersion is exploited to fulfill the required phase matching condition for third‐harmonic generation in short (≈ 4.3 µm long) waveguides. In a two‐wire transmission line configuration, antisymmetric plasmonic gap modes mediate the nonlinear parametric process and the incident laser polarization dictates the third harmonic power, with excellent agreement between experiment and theory.