arXiv subjects

J. Ballato

Publications and source records attributed to J. Ballato.

2 recordsLinked to original sources

arXiv2019

Low-loss silicon core fibre platform for broadband nonlinear photonics in the mid-infrared

Broadband mid-infrared light sources are highly desired for wide-ranging applications that span free-space communications to spectroscopy. In recent years, silicon has attracted great interest as a platform for nonlinear optical wavelength conversion in this region, owing to its low losses (linear and nonlinear) and high stability. However, most research in this area has made use of small core waveguides fabricated from the silicon-on-insulator platform, which suffer from high absorption losses of the silica cladding, limiting their ability to generate light beyond 3 $μ$m. Here we design and demonstrate a compact silicon core, silica clad waveguide platform that has low losses across the entire silicon transparency window. The waveguides are fabricated from a silicon core fibre that has been tapered to engineer the mode properties to ensure efficient nonlinear propagation in the core with minimal interaction of the mid-infrared light with the cladding. These waveguides exhibit many benefits of fibre platforms, such as high coupling efficiency and power handling capabilities, allowing for the generation of mid-infrared supercontinuum spectra with high brightness and coherence spanning almost two octaves (1.6-5.3 $μ$m).

physics.optics↗

arXiv2004

Frozen light in periodic stacks of anisotropic layers

We consider a plane electromagnetic wave incident on a periodic stack of dielectric layers. One of the alternating layers has an anisotropic refractive index with an oblique orientation of the principal axis relative to the normal to the layers. It was shown recently (A. Figotin and I. Vitebskiy, Phys. Rev. E68, 036609 2003) that an obliquely incident light, upon entering such a periodic stack, can be converted into an abnormal axially frozen mode with drastically enhanced amplitude and zero normal component of the group velocity. The stack reflectivity at this point can be very low, implying nearly total conversion of the incident light into the frozen mode with huge energy density, compared to that of the incident light. Supposedly, the frozen mode regime requires strong birefringence in the anisotropic layers - by an order of magnitude stronger than that available in common anisotropic dielectric materials. In this paper we show how to overcome the above problem by exploiting higher frequency bands of the photonic spectrum. We prove that a robust frozen mode regime at optical wavelengths can be realized in stacks composed of common anisotropic materials, such as YVO₄, LiNb, CaCO₃, and the like.

physics.optics↗