Manipulation of the resonance characteristics of random lasers from dye-doped polymer dispersed liquid crystals in capillary tubes

摘要

The resonance characteristics of random lasers from dye-doped polymer dispersed liquid crystals (DD-PDLCs) within capillary tubes were investigated. After adding a monomer (NOA65) into the liquid crystal mixtures, the emission spectra from the capillary tube revealed multiple emission spikes with narrow emission linewidth due to enhancement of the light scattering. Besides, the number of emission spikes, full width of the half maximum (FWHM), and lasing threshold from the DD-PDLCs were determined by the density and grain size of the polymer clusters within the PDLC mixtures through the alternation of the monomer concentration. Furthermore, the lasing performance of the DD-PDLCs in the capillary tube can be controlled by temperature. At low temperature, more emission spikes at long wavelengths were excited, and the laser revealed a relatively high Q-factor, accompanied with relatively low-threshold pump energy. It is because the increase in the birefringence of the liquid crystal molecules efficiently enhanced multiple recurrent light scattering.