A broadban-tunable photonic bandgap and thermally convertible laser with an ultra-low lasing threshold from a refilled chiral polymer template

This study demonstrates a broadband-tunable photonic bandgap (PBG) and thermally convertible laser with an ultra-low lasing threshold based on a gradient-pitched cholesteric liquid crystal (CLC) polymer template. The lowest energy threshold of the laser is 16 nJ per pulse under a pumped diameter of ca. 250 μm (i.e., 0.33 μJ per pulse per mm2), a value that is superior to those of other band-edge lasers based on most dye/quantum-dot-doped CLC systems. Owing to its multiple advantages, such as high stability, ultra-low lasing threshold, wide-band and linear spatial PBG-tunability, and lasing-mode convertibility, the CLC template device can be potentially used for photonics and display applications.