Harnessing second-order optical nonlinearities at interfaces in multilayer silicon-oxy-nitride waveguides

Abstract

We demonstrate multi-layer silicon-oxy-nitride (SiON) waveguides as a platform for broadband tunable phase-matching of second-order nonlinear interactions arising at material interfaces. Second-harmonic generation (SHG) is measured with a 2 ps pulsed pump of 1515-1535 nm wavelength, where 6 nW power is generated by an average pump power of 30 mW in a 0.92 mm long device. The wavelength acceptance bandwidth of the SHG is as broad as 20 nm due to the low material dispersion of SiON waveguides. The waveguide structure provides a viable method for utilizing second order nonlinearity for light generation and manipulation in silicon photonic circuits. V

Second‐Order Optical Nonlinearity in Silicon Waveguides: Inhomogeneous Stress and Interfaces

“…From the presented results, we conclude that the reason for its increased SH-intensity has to lie within the SiN x layer or the SiN x /Si interface. [ 19 ] Furthermore, a SH signal was generated in PECVD silicon nitride ring resonators, [ 15 ] where the nonlinearity was attributed to the interface between the silicon nitride and the silicon oxide. Previous studies on second-order nonlinearity in silicon nitride reported the observation of a strong SHG from PECVD silicon nitride fi lms grown on fused silicon oxide substrate, [ 16 ] where the nonlinearity was assigned to a SiN x bulk origin.…”

“…[2][3][4] However, since silicon exhibits a strong twophoton absorption in the near infrared, the effi ciency of these processes is limited. [15][16][17][18][19] In view of this, the different The lack of a dipolar second-order susceptibility (χ (2) ) in silicon due to the centrosymmetry of its diamond lattice usually inhibits effi cient second-order nonlinear optical processes in the silicon bulk. [5][6][7][8] This lead to efforts to deform the silicon lattice deliberately using inhomogeneous strain, e.g., through a deposition of a stressing layer.…”

On-chip frequency comb generation at visible wavelengths via simultaneous second- and third-order optical nonlinearities

“…The recent demonstrations of both Si 3 N 4 and silicon as second-order nonlinear (χ (2) ) materials [15][16][17][18][19][20][21][22][23] has expanded the range of possible applications for this CMOS-compatible platform. The symmetrybreaking in these otherwise-centrosymmetric materials has been attributed to 1) high levels of strain in the waveguide material [15], 2) surface effects from waveguide-cladding interfaces, which removes the bulk symmetry of the amorphous film [17][18][19][20], and 3) embedded silicon defects or nanoclusters [21,22]. The χ (2) coefficient has been estimated to be as high as 5.9 pm/V in Si 3 N 4 [22], and 190 pm/V in silicon [23].…”

Second harmonic generation from Ge doped SiO2 (Gex(SiO2)1−x) thin films grown by sputtering

“…This result is similar to those previously reported for thin films belonging to the C 1v symmetry group and implies the breakdown of the inversion symmetry in the z-axis. 12,25,29 The maximum value of d 33 is 8.2 pm/V at 11.2 at. %.…”