2020/03/31 by Ray Secondo, Secondo, Ray, Jacob B. Khurgin +3 · 1 citation
Engineering · Physics and Astronomy · #Photonic and Optical Devices #Advanced Fiber Laser Technologies #Photorefractive and Nonlinear Optics
paper · pdf · doi:10.48550/arxiv.2004.00134
For decades, nonlinear optics has been used to control the frequency and\npropagation of light in unique ways enabling a wide range of applications such\nas ultrafast lasing, sub-wavelength imaging, and novel sensing methods. Through\nthis, a key thread of research in the field has always been the development of\nnew and improved nonlinear materials to empower these applications. Recently,\nepsilon-near-zero (ENZ) materials have emerged as a potential platform to\nenhanced nonlinear interactions, bolstered in large part due to the extreme\nrefractive index tuning (\Δn~ 0.1 - 1) of sub-micron thick films that has\nbeen demonstrated in literature. Despite this experimental success, the theory\nhas lagged and is needed to guide future experimental efforts. Here, we\nconstruct a theoretical framework for the intensity-dependent refractive index\nof the most popular ENZ materials, heavily doped semiconductors. We demonstrate\nthat the nonlinearity when excited below bandgap, is due to the modification of\nthe effective mass of the electron sea which produces a shift in the plasma\nfrequency. We discuss trends and trade-offs in the optimization of excitation\nconditions and material choice (such material loss, band structure, and index\ndispersion), and provide a figure of merit through which the performance of\nfuture materials may be evaluated. By illuminating the framework of the\nnonlinearity, we hope to propel future applications in this growing field.\n