Periodic Reporting for period 1 - Pandora (Orientation-Patterned Gallium Phosphide for Integrated Nonlinear Photonics)
Periodo di rendicontazione: 2023-06-01 al 2025-11-30
Nonlinear optics is a thriving research field with numerous practical applications in advanced laser sources, all-optical frequency conversion, optical computing, generation of entangled pairs and quantum cryptography, supercontinuum and terahertz-radiation generation. Traditionally reserved to bulk, tabletop optical systems increasing drive in the photonics community to scale these applications to fit on a chip. The main bottleneck in the convergence of nonlinear optics and integrated photonics is that the volume of nonlinear crystals needs to be reduced by at least a factor 7.
Achieving such a volume reduction requires a major scientific breakthrough. The PANDORA project tackles this issue with the following combination: (a) a material with a high nonlinear figure of merit – gallium phosphide (GaP); (b) apply orientation patterning to engineer and exalt the intrinsic nonlinear properties of GaP; (c) shape the resulting crystal – OP-GaP – into guiding structures that allow ultimate compactness.
The cornerstone of the project is a recent result obtained by the PI and his team, showing that OP-GaP waveguides have the potential to outperform all existing nonlinear crystals with a form factor compatible with photonic integration. The PANDORA project proposes to build upon this result and draw out the full potential of OP-GaP as a single material platform for integrated nonlinear optics.
Achieving such a volume reduction requires a major scientific breakthrough. The PANDORA project tackles this issue with the following combination: (a) a material with a high nonlinear figure of merit – gallium phosphide (GaP); (b) apply orientation patterning to engineer and exalt the intrinsic nonlinear properties of GaP; (c) shape the resulting crystal – OP-GaP – into guiding structures that allow ultimate compactness.
The cornerstone of the project is a recent result obtained by the PI and his team, showing that OP-GaP waveguides have the potential to outperform all existing nonlinear crystals with a form factor compatible with photonic integration. The PANDORA project proposes to build upon this result and draw out the full potential of OP-GaP as a single material platform for integrated nonlinear optics.
During the initial two-year period of the project, the work was focused on improving each step in the fabrication process of OP-GaP non-linear waveguides. More specifically we identified multiple sources of optical losses related to the bonding and several of the etching steps. With the addition of several cleanroom engineers we tackled each of the specific issues. We improved the initial fabrication step of the GaP on GaAs to reduce the interface roughness, drastically reduced the number of particles that lead to decoding, added surface preparation steps that ensure fewer scattering centres at the interface, and optimized waveguide etching to reduce scattering on the waveguide sidewalls. Furthermore, we started exploiting the potential of e-beam lithography to produce OP-GaP seeds with a linearly varying period length, introducing chirp and ultimately producing waveguides for the conversion and/or generation of frequency combs - a tool necessary for chemical, biological and environmental sensing. We also used our platform opened our platform to a partner lab to try out an alternative approach to orientation patterning (TOP-GaP) that yielded interesting results.
The conversion efficiency of OP-GaP waveguides over the period has doubled to a current high of 400%W/cm2, which is the current record for orientation patterned III-V semiconductors.