Monolithic chalcogenide-on-silicon platform for passive and active integrated photonic devices at the 2 μ m waveband

Extending silicon photonic integrated circuits toward the 2 μm and longer mid-infrared spectral ranges requires photonic platforms that simultaneously provide strong optical confinement, fabrication tolerance, and active-device compatibility. Here, we demonstrate a monolithic chalcogenide-on-silicon strip-loaded platform that integrates a 400-nm-thick Ge25Sb10Se65 layer on a standard 220-nm silicon-on-insulator substrate. The chalcogenide overlayer enhances mode confinement at extended wavelengths while retaining the underlying silicon layer intact for carrier-injection-based modulation. Using this platform, we demonstrate grating couplers with a coupling loss of −4.98 dB and one-dimensional photonic crystal nanobeam resonators with loaded quality factors exceeding 2.6 × 104 near the 2 μm band. Active device is further realized by integrating the chalcogenide strip-loaded waveguide with a PIN-doped silicon layer, where carrier injection induces refractive-index change in silicon. The modulator achieves a DC extinction ratio of 7.61 dB with a 400 mV voltage swing and an average switching time of 3.98 ns. These results demonstrate that monolithic chalcogenide-on-SOI integration can combine fabrication-tolerant passive photonic structures with silicon-based active modulation, offering a scalable route toward extended-wavelength and mid-infrared integrated photonics.