Abstract
We study supercontinuum (SC) generation in graphene-covered nanowires based on a generic model that correctly accounts for the evolution of the photon number under Kerr and two-photon absorption processes, and the influence of graphene is treated within the framework of saturable photoexcited-carrier refraction. We discuss the role of the various effects on the generation of SC by a thorough analysis of short-pulse propagation in two different kinds of graphene-covered nanowires, one made of silicon nitride and the other made of silicon. Finally, we discuss the effect of stacking graphene layers as a means to enhance SC generation with pulse powers compatible with those in integrated optical devices.
Highlights
Supercontinuum (SC) generation is the subject of intense research in nonlinear optics [1,2,3,4], as it encounters applications in a vast number of areas in science and technology, such as in frequency combs [5, 6], spectroscopy, microscopy, and optical coherent tomography, among others [7].Silicon nanowires have often been studied for SC generation as they exhibit large nonlinear coefficients due to silicon’s large nonlinear refractive index (n2), two orders of magnitude larger than that of silica in the telecommunication band [8], and their small effective area (Aeff)
The large nonlinearity in silicon comes at the expense of two-photon absorption (TPA) [8] and free-carrier dispersion (FCD) and absorption (FCA) [10], phenomena that severely hinder the application of silicon nanowires in SC generation
In order to analyze the role of saturable photoexcited-carrier refraction (SPCR) in SC generation, we study the propagation of short pulses at λ0 = 1550 nm in two graphene-covered nanowires buried in a silica (SiO2) substrate
Summary
Silicon nanowires have often been studied for SC generation as they exhibit large nonlinear coefficients (γKerr) due to silicon’s large nonlinear refractive index (n2), two orders of magnitude larger than that of silica in the telecommunication band [8], and their small effective area (Aeff). Most importantly, they are compatible with CMOS fabrication [9] and have a wide transparency region in the near- and mid-infrared. The refractive index of SiN is ∼1.5 times smaller than that of silicon, leading to a reduced mode confinement, and its nonlinear refractive index is an order of magnitude smaller at telecom wavelengths [13]
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