Abstract
This study elucidates for the first time an all-optically controllable random laser in a dye-doped polymer-dispersed liquid crystal (DDPDLC) with nano-sized LC droplets. Experimental results demonstrate that the lasing intensity of the random laser can be controlled to decrease by increasing irradiation time/intensity of one green beam, and increase by increasing the irradiation time of one red beam. The all-optical controllability of the random laser is attributed to the green (red)-beaminduced isothermal nematic-->isotropic (isotropic-->nematic) phase transition in LC droplets by trans-->cis (cis-->trans back) isomerization of azo dyes. This isomerization may decrease (increase) the difference between the refractive indices of the LC droplets and the polymer, thereby increasing (decreasing) the diffusion constant (or transport mean free path), subsequently decreasing the scattering strength and, thus, random lasing intensity.
Highlights
Random lasers have attracted considerable attention over the last decade due to their interesting fundamentals and potential applications in photonics and bio-medicine [1,2,3,4,5,6]
Experimental results demonstrate that the lasing intensity of the random laser can be controlled to decrease by increasing irradiation time/intensity of one green beam, and increase by increasing the irradiation time of one red beam
Valuable applications for such an all-optically controllable random laser can be found in integrated photonics
Summary
Random lasers have attracted considerable attention over the last decade due to their interesting fundamentals and potential applications in photonics and bio-medicine [1,2,3,4,5,6]. Experimental results demonstrate that the obtained random lasing intensity can be controlled to decrease with increasing the irradiation time/intensity of one green beam, and increased by increasing the irradiation time of one red beam This all-optical controllability of random lasing can be attributed to the green-beam-induced isothermal nematic→isotropic (N→I) phase transition and red-beam-induced isothermal isotropic→nematic (I→N) phase transition in LC droplets by trans→cis and cis→trans back isomerizations of azo dyes, respectively. The former (latter) mechanism can decrease (increase) the difference between the refractive indices of the LC droplets and the polymer, thereby increasing (decreasing) the diffusion constant (or transport mean free path), which causes the decrease (increase) of scattering strength and, random lasing intensity
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