Fig. 2

Sb₂Se₃-based phase shifters in balanced (2 × 2 switch) and unbalanced MZI devices. a Layout of an unbalanced MZI with an optical microscope image of a 6 μm Sb₂Se₃ cell on a 10 μm-long microheater. b Experimental demonstration of four interferograms corresponding to each phase state permutation in the device shown in a. Crystallization was achieved using 6.2 V [3.2 V] and 1 ms pulses. Amorphization was achieved with 21 V [10.8 V] and 400 ns pulses. Extinction ratio over 35 dB is achieved between opposite states with a nearly complete π phase shift modulation. c Reversible switching over 125 full cycles between two intermediate Sb₂Se₃ states of the top-arm phase shifter in a balanced MZI. The plotted changes in transmission correspond to the difference between each arm’s intensity. d MZI 2 × 2 switch in the four different permutations: amorphous and crystalline states of each arm’s phase shifter with 6 μm Sb₂Se₃ cell for π/2 shift. Reversible switching is demonstrated for both cells. The Gaussian-like transmission curves result from the use of grating couplers