Dependence of random lasing properties on the gain volume in dye doped nematic liquid crystals

In this paper, the dependence of random lasing properties on the gain volume in dye doped nematic liquid crystals was investigated. Because the pump beam was focused by a lens to excite the sample, we could change the distance Delta l between the focal point and the sample to vary the gain volume. When Delta l was large (for example 4 mm), a Fabry-Perot like lasing mode was observed from the emission spectra. Decreasing Delta l to around zero, the lasing changed into the random mode completely. And the transition process from the Fabry-Perot like mode to the random mode when decreasing Delta l was observed. The underlying mechanisms were suggested. The above observed pump volume dependent lasing properties could be used to realise the manipulation over the mode and threshold of random lasers.

Automated summary

This study investigates the dependence of random lasing properties on the gain volume in dye doped nematic liquid crystals. By changing the distance between the focal point and the sample, the transition process from Fabry-Perot like mode to random mode was observed, suggesting underlying mechanisms. These observed pump volume dependent lasing properties could be used to manipulate the mode and threshold of random lasers.