Widely Tunable Lasing in a Colloidal Crystal Gel Film Permanently Stabilized by an Ionic Liquid

Widely tunable laser action by low threshold optical excitation can be realized by a colloidal crystal gel (CC‐G) film permanently stabilized by a non‐volatile ionic liquid. The CC‐G film consists of a non‐close‐packed structure of microparticles immobilized in a polymer gel. Optical excitation with green light gives rise to a single and very narrow laser emission with red color. The single laser emission peak can be tuned in a wide wavelength range by applying mechanical stress.