An Introduction to Nonlinear Integrated Photonics Devices: Nonlinear Effects and Materials

Abstract

The combination of integrated optics technologies with nonlinear photonics, which has led to the growth of nonlinear integrated photonics, has also opened the way to groundbreaking new devices and applications. Here we introduce the main physical processes involved in nonlinear photonics applications, and we discuss the fundaments of this research area, starting from traditional second-order and third-order phenomena and going to ultrafast phenomena. The applications, on the other hand, have been made possible by the availability of suitable materials, with high nonlinear coefficients, and/or by the design of guided-wave structures, which can enhance the material’s nonlinear properties. A summary of the most common nonlinear materials is presented, together with a discussion of the innovative ones. The discussion of fabrication processes and integration platforms is the subject of a companion article, also submitted for publication in this journal. There, several examples of nonlinear photonic integrated devices to be employed in optical communications, all-optical signal processing and computing, or quantum optics are shown, too. We aimed at offering a broad overview, even if, certainly, not exhaustive. We hope that the overall work could provide guidance for those who are newcomers to this field and some hints to the interested researchers for a more detailed investigation of the present and future development of this hot and rapidly growing field.

An Introduction to Nonlinear Integrated Photonics: Structures and Devices

“…As mentioned in the companion paper [ 62 ], numerous materials for integrated nonlinear optics have been investigated. Among them are Si and related materials, such as SiN, a-Si, and SiC; glasses, such as silica, high-index glass, and chalcogenide glasses; III–V semiconductors, in particular AlGaAs and lithium niobate (LN); and recently investigated materials, such as tantalum pentoxide (Ta 2 O 5 ) and vanadium dioxide (VO 2 ) [ 62 ] and references therein. Correspondingly, several material platforms have been developed to achieve the goal of a dense components’ integration.…”

“…Because of the relatively low strength of third-order nonlinearity, generation of Kerr combs requires small interaction volumes and high-Q resonators. For these reasons, small resonators are particularly suited to reach broadband comb generation with quite moderate pump power [ 62 ]. Advancements in the fabrication technology of optical micro-cavities may enable realizing ultra-fast and stable optical clocks and pulsed sources with extremely high repetition-rates in the form of compact and integrated devices.…”

“…Readers interested to delve into the main physical processes involved in nonlinear photonics applications and the most appealing materials are referred to a companion paper [ 62 ]. The focus here is to present some examples of nonlinear integrated photonic devices, with a brief overview of the types of optical integrated structures and the most common material fabrication platforms.…”

Editorial for the Special Issue on Micro/Nanophotonic Devices in Europe

“…The combination of integrated optics technologies with nonlinear photonics, which has led to the growth of nonlinear integrated photonics, has also opened the way for groundbreaking new devices and applications. In this Special Issue, two companion review papers, dedicated to nonlinear photonics and aimed at offering a broad overview, are proposed [2,3]. In the former, the main physical processes involved in nonlinear photonics applications are introduced, starting from traditional second-order and third-order phenomena and progressing to ultrafast ones (self-and cross-phase modulation, supercontinuum generation, and optical solitons).…”

Double-ring coupled structure for efficient sum-frequency generation of longwave mid-infrared signal

“…Optical nonlinearities have served as the fundamental building blocks for numerous applications in classical and quantum optics [1] [2] . While the development of mid-infrared (MIR) sources is progressing, the production of low-noise room temperature detectors remains to be challenging [3] .…”