Hybrid terahertz photonic integrated circuits based on Ge2Sb2Te5 phase change material atop of silicon waveguides

Optical Materials. 2025. Vol. 167. Article 117216.

Seliverstov S.V., Svaytodukh S. S., Kozhukhovsky A., Fudin D., Lazarenko P., Terekhov D., Prokhodtsov A., Nevzorov A., Kitsyuk E., Prikhodko A., Shurakov A., Kovalyuk V., Goltsman G.

The use of chalcogenide semiconductor compounds, in particular the Ge–Sb–Te (GST) material with phase memory, can significantly expand the capabilities of currently developed integrated terahertz (THz) photonic integrated circuits. In this paper we report on the measured value of the absorption contrast between amorphous and crystalline states of GST layer atop of silicon waveguide, which exceeds 10 dB in a frequency range of 126.5–145.5 GHz. The attenuation mechanism is associated with the absorption of THz radiation by free carriers, the concentration of which significantly depends on the phase state of the GST. For applications where frequency selectivity or routing is required, we have fabricated and studied a disk resonator. From the measured transmission spectrum of the THz disk resonator, the free spectral range of 3.7 GHz and the quality factor of 975 and the effective group refractive index were determined. The results obtained open up the possibility of wide use of the GST material in applications related to THz, including modulation, matrix-by-vector multiplication, fully optical signal routing, and neuromorphic circuits

Keywords: GST, Phase change materials, Terahertz photonics