Fig. 2: Silicon nitride heterogeneous photonics platform with a full set of passive and active building block components supporting submicrometre wavelengths.

a, Simplified wafer-scale process flow. Steps shown: (1) SiN deposition on a thermally oxidized Si substrate; (2) SiN waveguide patterning; (3) bonding of multiple III–V epitaxial structures; (4) substrate removal of the III–V epitaxy; (5) III–V processing, including multiple dry/wet etches to form the p–n junctions for active devices; (6) dielectric cladding deposition, via etches and metallization that complete the device fabrication. b, A photograph of a fully processed 4 inch wafer that contains thousands of devices. c, Scanning electron microscope images of (I) a SiN waveguide, (II) a waveguide coupler, (III) a III–V waveguide and electrical contacts for active components and (IV) an array of lasers and photodiodes connected by SiN waveguides. d, Envisioned schematic of a fully integrated atomic clock system fabricated on a single chip. e, Active and passive functionalities supported on the platform, with characteristic performance. Left to right: FP laser, a Fabry–Perot laser with integrated broadband mirrors that has less than 12 mA current threshold and more than 25 mW output power to a SiN waveguide; SOA, a semiconductor optical amplifier with maximum gain of 22 dB at 980 nm with 100 mA bias current (the 3 dB bandwidth of the gain at 100 mA spans over 20 nm); passive waveguide, SiN waveguides with sub-dB cm⁻¹ propagation loss in the 900–980 nm wavelength range (green shading indicates the standard error from cutback loss linear fit after averaging device loss over identical test structures from a single wafer); modulator, a Mach–Zehnder interferometer with phase modulators showing V_π = 2.4 V and a greater than 20 dB extinction ratio (ER); PD, a photodiode with a greater than 0.6 A W⁻¹ responsivity at 980 nm and nA-level dark current.