Opto-mechanical analogue of Peierls transition

Abstract Peierls transition is associated with a metal-insulator transition due to a displacive distortion in a regular quasi one-dimensional ion array that increases the unit cell length, creating a band gap in the electronic band structure. Here, we introduce the opto-mechanical analogue of Peierls transition that occurs in diffraction grating waveguide couplers, operating at normal light incidence, with grating ridges being able to move along the waveguide surface. We analyze optical gradient forces acting on slightly displaced grating ridges, i.e. making double the grating period and enabling resonant excitation of waveguide modes at the wavelength of their Bragg reflection produced by an unperturbed grating, thus strongly influencing the light transmission. We identify the wavelength ranges, within which the optical forces move further grating ridges to certain positions, at which the net force along the waveguide plane becomes zero, resulting in the stable asymmetric grating and strongly suppressed light transmission. Possible realizations of this transition are discussed, including the potential realization of all-optical dynamic nanophotonic components based on grating configurations with mechanical restoring forces.