| Summary: | The experimental detail of a random lasing action from dye-doped nematic liquid crystals (LCs) inside single-core capillaries with a core diameter below 50 μm was investigated. The resonant characteristics, including the number of emission spikes, the full width at half maximum (FWHM), and the estimated Q-factor, were shown to depend on the core diameter of a capillary. In contrast with a capillary with a larger core diameter and having various emission spikes, only three emission spikes were excited from a capillary with a 10-μm core diameter, owing to the smaller effective area of the pump beam. However, the decrease in the amplitude of emission spikes and the broadening of the linewidth accompanying the higher lasing threshold from a capillary with a 50-μm core diameter are attributed to the decrease in the pump fluence and the increase in the scattering loss, respectively. In this paper, a random laser (RL) with the shortest FWHM emission peak of about 0.47 nm and the highest Q-factor of about 1268 was generated from the capillary with a 20-μm core diameter. By means of temperature adjustment, the emission spectra of the RL that is related to the birefringence and alignment ordering of the LC molecules inside a capillary with a 20-μm core diameter can be effectively altered. Our experiments show that the RL, revealing adjustable output emission spectra, can be a promising device in using remote sensing applications.
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