Wide tunable lasing in photoresponsive chiral liquid crystal emulsion

Abstract

A new tunable laser based on a photoresponsive chiral liquid crystal emulsion is reported. Such a laser can be reversibly photo-tuned in a wide spectral range of 112 nm (566–678 nm), and it simultaneously possesses stable emission performance and quasi-continuous tunability. Typically, unlike the conventional liquid crystal laser, the proposed laser can be fabricated by simply coating the material on a single substrate, which will simplify the production process and broaden the application of liquid crystal laser. In addition, the mechanisms of tunability are explored on a molecular scale. The studies reveal that the molecular conformation transition of a photosensitive chiral switch during isomerization leads to changes in not only the molecular geometry and the direction of dipole moment, but also the molecular interactions and the miscibility of the materials. These changes cause the rearrangement of liquid crystals, thus rendering the variation of helical twisted power and achieving tuning on the photonic band-edge of the chiral liquid crystal, consequently forming a photo-tunable laser.