Fig. 5

Engineering microheater to achieve partial amorphization. a FEM heat transfer simulation of a microheater consisting of five 2 μm-wide ‘bridges’. The temperature profile along the waveguide is plotted for different pulse widths. b Colored SEM image of a fabricated device. c Partial amorphization of the bottom arm Sb₂Se₃ in an unbalanced MZI. 10.8 V pulses with varying widths between 800 ns and 1050 ns were employed to amorphize and 3.2 V for 1 ms to fully crystallize. The transmission is measured in the top output waveguide where a maximum of π/2 phase shift is observed, corresponding to the full amorphization of the three central ‘bridges’. Reversible switching is demonstrated over three cycles between the full crystalline state and the marked intermediate state (corresponding to a 900 ns pulse). d The same phase shifter with partial amorphization in a micro-ring resonator with continuous tuning of the resonance wavelength