Polarization selective ultra-broadband wavelength conversion in silicon nitride waveguides

Abstract

We experimentally demonstrate broadband degenerate continuous-wave four-wave mixing in long silicon nitride (Si3N4) waveguides for operation both in the telecommunication L-band and the thulium band near 2 µm by leveraging polarization dependence of the waveguide dispersion. Broadband conversion is typically demonstrated in short milimeter long waveguides as the bandwidth is linked to the interaction length. This makes it challenging to simultaneously push bandwidth and efficiency, imposing stringent constraints on dispersion engineering. In this work, we show conversion bandwidths larger than 150 nm in the L-band when pumping in the transverse magnetic (TM) mode and larger than 120 nm at 2 µm when using transverse electric excitation, despite the use of 0.5 m long waveguides. In addition, we also show how extreme polarization selectivity can be leveraged in a single waveguide to enable switchable distant phase-matching based on higher-order dispersion. Relying on this approach, we demonstrate the selective conversion of light from the telecom band to the O-band for TM polarization or to the mid-infrared light up to 2.5 µm in TE. Our experiments are in excellent agreement with simulations, showing the high potential of the platform for broadband and distant conversion beyond the telecom band.

Generalized Coherent Photogalvanic Effect in Coherently Seeded Waveguides

“…Particularly, Si 3 N 4 with its large transparency window, low losses, high third-order susceptibility (𝜒 (3) ), high refractive index, and mature nanofabrication process is very appealing. It is exploited for several linear [25] and nonlinear applications, such as four-wave mixing, [26,27] third-harmonic generation (THG), [28] supercontinuum, [29] and Kerr comb [30] generation using 𝜒 (3) nonlinearity. AOP now allows to add 𝜒 (2) processes, such as SHG, difference-frequency generation, [31] and spontaneous parametric down-conversion, [32] to the already impressive nonlinear toolbox of Si 3 N 4 .…”

Coherent Photogalvanic Effect for Second-Order Nonlinear Photonics

“…Particularly, stoichiometric silicon nitride (Si 3 N 4 ) with its large transparency window, low losses, high third-order susceptibility (χ (3) ), high refractive index and mature nanofabrication process is very appealing. It is exploited for several linear [25] and nonlinear applications, such as four-wave mixing [26,27], third-harmonic generation (THG) [28], supercontinuum [29] and Kerr comb [30] generation using χ (3) nonlinearity. AOP now allows to add χ (2) processes, such as SHG, differencefrequency generation [31] and spontaneous parametric down-conversion [32], to the already impressive nonlinear toolbox of Si 3 N 4 .…”