Shrinkage of Cholesteric Liquid Crystalline Microcapsule as Omnidirectional Cavity to Suppress Optical Loss

Cholesteric liquid crystalline (CLC) emulsions are the easiest 3D omnidirectional laser resonators to fabricate. To exploit the full potential of CLC emulsions as distributed Bragg reflection (DBR) mode laser resonators, monodispersed water‐in‐CLC‐in‐water double emulsions (CLC microcapsules) have higher performance scalability than simple CLC droplets. If laser dyes are concentrated at the center of CLC microcapsules, emitted light from the dye is 3D confined. When water is squeezed from the inner phase of a CLC microcapsule comprising an aqueous laser dye solution by means of osmotic pressure difference from the outer phase, the DBR lasing threshold of the CLC microcapsule is reduced. The shrinkage of the inner droplet contributes not only the simple reduction of the cavity length but also the suppression of the optical loss to reduce the lasing threshold. The reduced optical loss is beneficial to realize various devices: optical manipulation, photonic cross communications, and biochemical, light, and temperature sensing. Their flexible photonic structures are suitable for emerging and future optical devices like wearable optical devices. The lasing threshold of cholesteric liquid crystalline microcapsules with an aqueous laser dye solution can be reduced by squeezing water from the inner droplet using osmosis. The reduction of the lasing threshold is attributed to the decrease of the optical loss, which can be also used to realize various quantum devices.