Enhanced Nonlinear Harmonic Generation from ZnO-Based Multifractal Photonic Membranes

Structurally complex photonic media with non-periodic refractive index variations on the wavelength scale display a very rich physics driven by wave interference effects in the multiple scattering regime and display profound analogies to the mesoscopic transport of electrons in disordered metallic alloys and semiconductors. In the last two decades, the study of disorder-induced phenomena for optical waves has stimulated the growing field of “disordered photonics”, resulting in a wide range of applications to lasing, solar energy, speckle-based imaging and spectroscopy, and nonlinear optics. Recently, we designed and developed nano-perforated photonic membrane photonic structures with controlled multifractal geometry using silicon nitride (SiN) and we demonstrated experimentally distinctive optical resonances with enhanced light intensity distributed across extended device areas with characteristic multiscale intensity fluctuations.<br/>In this talk, we build on our previous results by presenting the design, fabrication, linear and nonlinear optical characterization of multifractal photonic membranes fabricated in optically nonlinear ZnO materials by magnetron sputtering deposition, electron beam lithography, and high-quality deep reactive ion etching. Using this approach in combination with the efficient localization landscape theory, we design and demonstrate multifractal photonic structures with enhanced harmonic generation efficiency driven by the excitation of multifractal modes. Finally, we perform third-harmonic imaging spectroscopy on the fabricated samples under different femtosecond pulsed excitation conditions and address the potential to achieve nonlinear instabilities of speckle patterns on a miniaturized optical chip.