Lin Yun, Ye Yong, Fang Ziliang, Chen Bingyu, Zhang Haoran, Yang Tiefeng, Wei Yuming, Jin Yunxia, Kong Fanyu, Peng Gangding, Cao Hongchao, Guan Heyuan, Lu Huihui
Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Jinan University, Guangzhou 510632, China.
Laboratory of Information Optics and Opto-Electronic Technology, Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, Shanghai 201800, China.
Nanophotonics. 2024 Mar 13;13(13):2335-2348. doi: 10.1515/nanoph-2023-0886. eCollection 2024 May.
Nonlinear optics has generated a wide range of applications in the fields of optical communications, biomedicine, and materials science, with nonlinear conversion efficiency serving as a vital metric for its progress. However, the weak nonlinear response of materials, high optical loss, and inhomogeneous distribution of the light field hamper the improvement of the conversion efficiency. We present a composite grating waveguide structure integrated into a Bragg reflector platform. This design achieves high Q in the spectral range by exploiting the unique properties exhibited by the bound states in the Bloch surface wave-enhanced continuum, and efficient second-harmonic generation by close-field amplification with the optical field tightly localized in a nonlinear material. By manipulating the symmetry of the grating, a precise tune over the near field within a designated wavelength range can be achieved. Specifically, we select a photonic crystal configuration supporting surface waves, employing TE polarization conditions and an asymmetry factor of -0.1 between the composite gratings. This configuration resonates at a fundamental wavelength of 783.5 nm, exhibiting an impressive -factor of 10. Notably, at an incident light intensity of 1.33 GW/cm, we achieve a normalized electric field strength of up to 940 at the fundamental frequency and a second-harmonic conversion efficiency of up to 6 × 10, significantly amplifying the second-harmonic response. The proposed configuration in this investigation has the potential to be integrated into the field of nonlinear optics for sensing frequency conversion applications.
非线性光学在光通信、生物医学和材料科学等领域产生了广泛的应用，非线性转换效率是其发展的一个重要指标。然而，材料的弱非线性响应、高光学损耗以及光场的不均匀分布阻碍了转换效率的提高。我们提出了一种集成在布拉格反射器平台上的复合光栅波导结构。这种设计通过利用布洛赫表面波增强连续体中的束缚态所表现出的独特特性，在光谱范围内实现了高Q值，并通过将光场紧密局域在非线性材料中的近场放大实现了高效的二次谐波产生。通过操纵光栅的对称性，可以在指定波长范围内对近场进行精确调谐。具体而言，我们选择了一种支持表面波的光子晶体配置，采用TE偏振条件，复合光栅之间的不对称因子为-0.1。这种配置在783.5 nm的基波波长处发生共振，表现出令人印象深刻的品质因数10。值得注意的是，在1.33 GW/cm的入射光强度下，我们在基频处实现了高达940的归一化电场强度和高达6×10的二次谐波转换效率，显著放大了二次谐波响应。本研究中提出的配置有可能集成到非线性光学领域用于传感频率转换应用。
