Loss assessment in random crystal polarity gallium phosphide microdisks grown on silicon.

III-V semiconductors grown on silicon recently appeared as a promising platform to decrease the cost of photonic components and circuits. For nonlinear optics, specific features of the III-V crystal arising from the growth on the nonpolar Si substrate and called antiphase domains (APDs) offer a unique way to engineer the second-order properties of the semiconductor compound. Here we demonstrate the fabrication of microdisk resonators at the interface between a gallium-phosphide layer and its silicon substrate. The analysis of the whispering gallery mode quality factors in the devices allows the quantitative assessment of losses induced by a controlled distribution of APDs in the GaP layer and demonstrates the relevance of such a platform for the development of polarity-engineered III-V nonlinear photonic devices on silicon.