Journal
OPTICS EXPRESS
Volume 18, Issue 25, Pages 25896-25905Publisher
OPTICAL SOC AMER
DOI: 10.1364/OE.18.025896
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Funding
- National Science Council of the Republic of China, Taiwan [NSC 97-2112-M-040-001-MY2, NSC 97-2112-M-006-013-MY3]
- Advanced Optoelectronic Technology Center, National Cheng Kung University under Ministry of Education
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This study investigates, for the first time, an all-optically controllable random laser based on a dye-doped liquid crystal (DDLC) cell added with a photoisomerizable dye. Experimental results indicate that the lasing intensity of this random laser can be all-optically controlled to decrease and increase sequentially with a two-step exposure of one UV and then one green beam. All-optically reversible controllability of the random lasing emission is attributed to the isothermal nematic(N)-> isotropic(I) and I -> N phase transitions for LCs due to the UV-beam-induced trans -> cis and green-beam-induced cis -> trans back isomerizations of the photoisomerizable dye, respectively. The former and the latter can decrease and increase the spatial fluctuations of the order and thus of the dielectric tensor of LCs, respectively, subsequently increasing and decreasing the diffusion constant (or transport mean free path), respectively, and thus decaying and rising the scattering strength for the fluorescence photons in their recurrent multi-scattering process, respectively. The consequent decrease and increase of the lasing intensity for the random laser and thus the rise and descent of its energy threshold are generated, respectively. (c) 2010 Optical Society of America
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