2018/08/23 by Dalziel J. Wilson, Katharina Schneider, Simon Hoenl +3 · 2 citations
Physics and Astronomy · #physics.app-ph #physics.optics
paper · pdf · doi:10.1038/s41566-019-0537-9
published as Nature Photonics 14 (2020) 57 · 13 pages, 10 figures, 1 table; typos corrected, added/fixed references, modified title
arxiv created 2018/08/23 · arxiv updated 2020/01/07
Gallium phosphide (GaP) is an indirect bandgap semiconductor used widely in solid-state lighting. Despite numerous intriguing optical properties---including large χ(2) and χ(3) coefficients, a high refractive index (>3), and transparency from visible to long-infrared wavelengths (0.55-11 μm)---its application as an integrated photonics material has been little studied. Here we introduce GaP-on-insulator as a platform for nonlinear photonics, exploiting a direct wafer bonding approach to realize integrated waveguides with 1.2 dB/cm loss in the telecommunications C-band (on par with Si-on-insulator). High quality (Q> 105), grating-coupled ring resonators are fabricated and studied. Employing a modulation transfer approach, we obtain a direct experimental estimate of the nonlinear index of GaP at telecommunication wavelengths: n2=1.2(5)× 10-17 m2/W. We also observe Kerr frequency comb generation in resonators with engineered dispersion. Parametric threshold powers as low as 3 mW are realized, followed by broadband (>100 nm) frequency combs with sub-THz spacing, frequency-doubled combs and, in a separate device, efficient Raman lasing. These results signal the emergence of GaP-on-insulator as a novel platform for integrated nonlinear photonics.