Nonlinear optical properties of integrated GeSbS chalcogenide waveguides

In this paper, we report the experimental characterization of highly nonlinear GeSbS chalcogenide glass waveguides. We used a single-beam characterization protocol that accounts for the magnitude and sign of the real and imaginary parts of the third-order nonlinear susceptibility of integrated Ge23Sb7S70 （GeSbS） chalcogenide glass waveguides in the near-infrared wavdength range at λ = 1580 nm. We measured a waveguide nonlinear parameter of 7.0 4- 0.7 W-1 · m-1, which corresponds to a nonlinear refractive index of n2 =（0.93 ± 0.08） ×10-18 m2/W, comparable to that of silicon, but with an 80 times lower two-photon absorption coefficient βTPA = （0.010± 0.003） cm/GW, accompanied with linear propagation losses as low as 0.5 dB/cm. The outstanding linear and nonlinear properties of GeSbS, with a measured nonlinear figure of merit FOM TPA = 6.0 ± 1.4 at λ = 1580 nm, ultimately make it one of the most promising integrated platforms for the realization of nonlinear functionalities.

Supercontinuum generation in silicon photonics platforms

Nonlinear optics has not stopped evolving,offering opportunities to develop novel functionalities in photonics.Supercontinuum generation,a nonlinear optical phenomenon responsible for extreme spectral broadening,attracts the interest of researchers due to its high potential in many applications,including sensing,imaging,or optical communications.In particular,with the emergence of silicon photonics,integrated supercontinuum sources in silicon platforms have seen tremendous progress during the past decades.This article aims at giving an overview of supercontinuum generation in three main silicon-compatible photonics platforms,namely,silicon,silicon germanium,and silicon nitride,as well as the essential theoretical elements to understand this fascinating phenomenon.

Cavity-based photoconductive sources for real-time terahertz imaging

Optically driven photoconductive switches are one of the predominant sources currently used in terahertz im-aging systems.However,owing to their low average powers,only raster-based images can be taken,resulting in slow acquisition.In this work,we show that by placing a photoconductive switch within a cavity,we are able to generate absolute average THz powers of 181μW with the frequency of the THz emission centered at 1.5 THz-specifications ideally adapted to applications such as non-destructive imaging.The cavity is based on a metal-insulator-metal structure that permits an en hancement of the average power by almost 1 order of magnitude compared to a standard structure,while conserving a broadband spectral response.We demonstrate proof-of-principle real-time imaging using this source,with the broadband spectrum permitting to eliminate strong diffraction artifacts.