Broadband high-contrast visible optical switches based on a spin-crossover material

Visible optical switches embedding a spin-crossover thin film and exploiting the frustrated total internal reflection operation principle are studied and optimized numerically with a view to obtain broadband high-contrast devices. A practical implementation using uncoated SF11 prisms embedding a 1-µm-thick layer of iron-triazolyl-borate complex as the thermo-active phase-change material is shown to support p-polarized modulation with contrast in excess of 90% over a spectral bandwidth greater than 270 nm and over an angular acceptance bandwidth of 0.45°, surpassing the performance achievable with optically resonant devices.