Optical properties change due to the displacive transition of MnTe and its application to phase-change optical switches

Abstract The objective of our research is to develop optical switches utilizing the phase transition of manganese telluride (MnTe). Initially, we investigated the fundamental optical properties of MnTe by measuring the complex refractive index spectra of α - and β -MnTe thin films. Notably, the imaginary component of the refractive index exhibited a shift of approximately 1 eV toward higher energy due to the phase transition from the α -phase to the β -phase. First-principles calculations indicated that this shift results from an increase in the band gap, mainly attributed to a reduction in the interatomic distance between manganese (Mn) and tellurium (Te). Furthermore, we conducted physical simulations of light propagation in two optical switch models—the Mach–Zehnder type and the ring resonator type—incorporating MnTe thin films. Both models demonstrated effective ON–OFF operation with extinction ratios ranging from 16 to 17 dB, facilitated by the phase transition of MnTe.