Mainz 2026 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 17: Photonics and Biophotonics I

Q 17.7: Talk

Tuesday, March 3, 2026, 12:30–12:45, P 3

Electric field-Induced second-harmonic generation in silicon-rich nitride — •Laurids Wardenberg, Krishna Koundinya Upadhyayula, and Jörg Schilling — Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Germany

Applying a DC electric field to PECVD-grown films of silicon-rich nitride enables a voltage-controllable second-order susceptibility, giving rise to electric field-induced second-harmonic generation (EFISH). From the quadratic scaling of the second-harmonic output with the applied field, both the field-dependent and field-free second-order susceptibilities are experimentally extracted, reaching values comparable to those of traditional nonlinear crystals. The associated third-order susceptibility is likewise obtained and shown to increase significantly with higher silicon content in the SiNx films.

To further boost the nonlinear response, a quasi-bound state in the continuum is excited by implementing an extended square 2D nanopillar array on a SiNx base layer. The resulting strong field confinement in this waveguide-like structure, combined with the field-free second-order nonlinearity, produces a pronounced enhancement of TM-polarized second-harmonic generation.

Finally, by applying a DC electric field parallel to the polarization of the pump in a similar resonant structure, the interaction between photonic resonances and the EFISH mechanism is demonstrated. Together, these results open the door to low-power, on-chip frequency-conversion applications using both second- and third-order nonlinearities of the CMOS-compatible silicon-rich nitride platform.

Keywords: Nonlinear optics; Second harmonic generation; Silicon nitride; Third-order nonlinearity; Photonic bound states in the continuum