Second-harmonic generation enabled by longitudinal electric-field components in photonic wire waveguides

Abstract

We investigate second-harmonic generation in III-V semiconductor wire waveguides aligned with a crystallographic axis. In this direction, because of the single nonzero tensor element coming from the zinc-blende symmetry of III-V semiconductors, only frequency conversion by mixing with the longitudinal components of the optical fields is allowed. We experimentally study the impact of the propagation direction on the conversion efficiency and confirm the role played by the longitudinal components through the excitation of an antisymmetric second-harmonic higher-order mode.

Influence of longitudinal mode components on second harmonic generation in III-V-on-insulator nanowires

“…In practice however, more complex nonlinear wave mixing can be expected because the optical modes in high index contrast waveguides display large longitudinal components. We recently experimentally demonstrated SHG enabled by longitudinal components in III-V wire waveguides [8]. Here we further investigate the impact of strong longitudinal components on SHG.…”

“…Nonlinear coupling in this case always involves a longitudinal mode component [8]. In both nonlinear coefficients involving the TM 30 and TE 01 modes shown in Fig.…”

“…Note that, Eq. (25) can be easily generalized to include the impact of propagation loss on the second harmonic generation efficiency [8].…”

“…where θ is the angle between the propagation direction z' and the z axis [8]. The zinc-blende crystalline arrangement of III-V crystals leads to a single nonzero tensor element ( χ (2) xyz = 2d 14 0).…”

“…While we focus on III-V semiconductor wire waveguides [6,7,16], we stress that our analysis can be easily adapted to other platforms. We consider indium gallium phosphide (InGaP) around 1550 nm as the guiding material [8,17]. InGaP displays a4 symmetry and exhibits very low nonlinear losses at telecom wavelengths in the C-band.…”