*Article* **Efficient Design for Integrated Photonic Waveguides with Agile Dispersion**

**Zhaonian Wang, Jiangbing Du \*, Weihong Shen, Jiacheng Liu and Zuyuan He**

State Key Laboratory of Advanced Optical Communication Systems and Networks, Shanghai Jiao Tong University, Shanghai 200240, China; ee\_wzn@sjtu.edu.cn (Z.W.); shenweihong@sjtu.edu.cn (W.S.); jiacheng.liu@sjtu.edu.cn (J.L.); zuyuanhe@sjtu.edu.cn (Z.H.) **\***Correspondence:dujiangbing@sjtu.edu.cn

**Abstract:** Chromatic dispersion engineering of photonic waveguide is of grea<sup>t</sup> importance for Photonic Integrated Circuit in broad applications, including on-chip CD compensation, supercontinuum generation, Kerr-comb generation, micro resonator and mode-locked laser. Linear propagation behavior and nonlinear effects of the light wave can be manipulated by engineering CD, in order to manipulate the temporal shape and frequency spectrum. Therefore, agile shapes of dispersion profiles, including typically wideband flat dispersion, are highly desired among various applications. In this study, we demonstrate a novel method for agile dispersion engineering of integrated photonic waveguide. Based on a horizontal double-slot structure, we obtained agile dispersion shapes, including broadband low dispersion, constant dispersion and slope-maintained linear dispersion. The proposed inverse design method is objectively-motivated and automation-supported. Dispersion in the range of 0–1.5 ps/(nm·km) for 861-nm bandwidth has been achieved, which shows superior performance for broadband low dispersion. Numerical simulation of the Kerr frequency comb was carried out utilizing the obtained dispersion shapes and a comb spectrum for 1068-nm bandwidth with a 20-dB power variation was generated. Significant potential for integrated photonic design automation can be expected.

**Keywords:** dispersion engineering; slot waveguide; inverse design; deep neural network; optical frequency comb
