Broadband dispersive free, large, and ultrafast nonlinear material platforms for photonics

Xinxiang Niu,Xiaoyong Hu,Hong Yang,Cuicui Lu,Yan Sheng,Qihuang Gong

doi:10.1515/nanoph-2020-0420

Abstract

Abstract Broadband dispersion free, large and ultrafast nonlinear material platforms comprise the essential foundation for the study of nonlinear optics, integrated optics, intense field optical physics, and quantum optics. Despite substantial research efforts, such material platforms have not been established up to now because of intrinsic contradictions between large nonlinear optical coefficient, broad operating bandwidth, and ultrafast response time. In this work, a broadband dispersion free, large and ultrafast nonlinear material platform based on broadband epsilon-near-zero (ENZ) material is experimentally demonstrated, which is designed through a novel physical mechanism of combining structural dispersion and material dispersion. The broadband ENZ material is constructed of periodically nanostructured indium tin oxide (ITO) films, and the structure is designed with the help of theoretical predictions combined with algorithm optimization. Within the whole broad ENZ wavelength range (from 1300 to 1500 nm), a wavelength-independent and large average nonlinear refractive index of −4.85 × 10−11 cm2/W, which is enlarged by around 20 times than that of an unstructured ITO film at its single ENZ wavelength, and an ultrafast response speed at the scale of Tbit/s are experimentally reached simultaneously. This work not only provides a new approach for constructing nonlinear optical materials but also lays the material foundation for the application of nanophotonics.

Highlights

Nonlinear optical materials offer a platform for boosting the development of integrated optics, intense field optics, weak-light nonlinear optics, and quantum optics [1]
The fourth unit was a layer of pure air, i.e., the indium tin oxide (ITO) was removed completely
Looking beyond the fabricated sample, our proposed principle, i.e., effective medium theory (EMT) theory combined with genetic algorithm optimizations, is able to design the broadband ENZ response in different spectral range based on different structures and materials, indicating a broad applicability in material community

Summary

Introduction

Nonlinear optical materials offer a platform for boosting the development of integrated optics, intense field optics, weak-light nonlinear optics, and quantum optics [1]. Materials nonlinearity is expected to have the properties of broadband dispersion free, large, and ultrafast time response simultaneously [2]. Most of natural materials have a relatively weak nonlinear optical response when operating away from resonances or suffer from strong nonlinear dispersions when operating on resonances [3, 4]. While the multicomponent organic materials and metal-dielectric composite materials have been proposed with enhanced the third-order nonlinearity, these enhancements rely deeply on the electronic resonances of materials themselves and result in degradations of response time and nonlinear bandwidth for practical use [5,6,7,8,9,10,11,12]. X. Niu et al.: Broadband dispersive free, large, and ultrafast nonlinear material platforms bandwidth lie in the community of optical nonlinear materials and the practical utilizations are greatly impeded

Results

Discussion

Conclusion