Intrinsic polarity inversion in III-nitride waveguides for efficient nonlinear interactions.

III-nitrides provide a versatile platform for nonlinear photonics. In this work, we explore a new promising configuration - composite waveguides containing GaN and AlN layers with inverted polarity, i.e., having opposite signs of the χ(2) nonlinear coefficient. This configuration allows us to address the limiting problem of the mode overlap for nonlinear interactions. Our modelling predicts a significant improvement in the conversion efficiency. We confirm our theoretical prediction with the experimental demonstration of second harmonic generation with an efficiency of 4%W-1cm-2 using a simple ridge waveguide. This efficiency is an order of magnitude higher compared to the previously reported results for III-nitride waveguides. Further improvement, reaching a theoretical efficiency of 30%W-1cm-2, can be achieved by reducing propagation losses.

Low-loss GaN-on-insulator platform for integrated photonics.

III-Nitride semiconductors are promising materials for on-chip integrated photonics. They provide a wide transparency window from the ultra-violet to the infrared that can be exploited for second-order nonlinear conversions. Here we demonstrate a photonics platform based on epitaxial GaN-on-insulator on silicon. The transfer of the epi-material on SiO2 is achieved through wafer bonding. We show that quality factors up to 230 000 can be achieved with this platform at telecommunication wavelengths. Resonant second harmonic generation is demonstrated with a continuous wave conversion efficiency of 0.24%/W.

Up to 300†K lasing with GeSn-On-Insulator microdisk resonators.

GeSn alloys are the most promising direct band gap semiconductors to demonstrate full CMOS-compatible laser integration with a manufacturing from Group-IV materials. Here, we show that room temperature lasing, up to 300 K, can be obtained with GeSn. This is achieved in microdisk resonators fabricated on a GeSn-On-Insulator platform by combining strain engineering with a thick layer of high Sn content GeSn.

Phase-matched second harmonic generation with on-chip GaN-on-Si microdisks.

We demonstrate phase-matched second harmonic generation in gallium nitride on silicon microdisks. The microdisks are integrated with side-coupling bus waveguides in a two-dimensional photonic circuit. The second harmonic generation is excited with a continuous wave laser in the telecom band. By fabricating a series of microdisks with diameters varying by steps of 8 nm, we obtain a tuning of the whispering gallery mode resonances for the fundamental and harmonic waves. Phase matching is obtained when both resonances are matched with modes satisfying the conservation of orbital momentum, which leads to a pronounced enhancement of frequency conversion.

Near-infrared III-nitride-on-silicon nanophotonic platform with microdisk resonators.

We have developed a nanophotonic platform with microdisks using epitaxial III-nitride materials on silicon. The two-dimensional platform consists of suspended waveguides and mushroom-type microdisks as resonators side-coupled with a bus waveguide. Loaded quality factors up to 80000 have been obtained in the near-infrared spectral range for microdisk diameters between 8 and 15 µm. We analyze the dependence of the quality factors as a function of coupling efficiency. We have performed continuous-wave second harmonic generation experiments in resonance with the whispering gallery modes supported by the microdisks.