Fig. 7: Commercial foundry-processed photonic integrated circuits featuring Mach-Zehnder Interferometers (MZI) with Type III microheater.

a Optical microscope images of two unbalanced MZIs and zoom-in to a single Type III microheater with embedded phase change material. b Illustration of an approximate cross-section (not in scale). c, d Zoom-in to the MZIs’ interferograms tracking the modulation at a minimum in transmission using (b) 30 nm thick Ge2Sb2Se4Te on a n-doped and (c) 30 nm thick Sb2Se3 on a p-doped Type III microheater.