Gallium phosphide-on-silicon dioxide photonic devices

TL;DR

This paper demonstrates a scalable process for fabricating gallium phosphide photonic devices on silicon dioxide, achieving high-quality optical components suitable for telecommunications and visible light applications.

Contribution

First successful fabrication of GaP-on-insulator photonic devices using wafer bonding and etching techniques, enabling scalable production of high-performance photonic circuits.

Findings

Peak grating coupler efficiency of 4.8 dB

Optical quality factors up to 17000 achieved

Observation of second- and third-harmonic generation

Abstract

The development of integrated photonic circuits utilizing gallium phosphide requires a robust, scalable process for fabrication of GaP-on-insulator devices. Here we present the first GaP photonic devices on SiO$_2$. The process exploits direct wafer bonding of a GaP/Al$_x$Ga$_{1-x}$P/GaP heterostructure onto a SiO$_2$-on-Si wafer followed by removal of the GaP substrate and the Al$_x$Ga$_{1-x}$P stop layer. Photonic devices such as grating couplers, waveguides, and ring resonators are patterned by inductively coupled-plasma reactive-ion etching in the top GaP device layer. The peak coupling efficiency of the fabricated grating couplers is as high as 4.8 dB. Optical quality factors of 17000 as well as second- and third-harmonic generation are observed with the ring resonators. Because the large bandgap of GaP provides for low two-photon absorption at telecommunication wavelengths, the high-yield fabrication of GaP-on-insulator photonic devices enabled by this work is especially interesting for applications in nanophotonics, where high quality factors or low mode volumes can produce high electric field intensities. The large bandgap also enables integrated photonic devices operating at visible wavelengths.