染料掺杂液晶可调谐光纤荧光光源的研究

本文提出了染料掺杂液晶填充空心光纤构造荧光可调谐光源.基于染料分子能级结构理论分析B4400荧光光谱依赖温度的变化特性,采用脉宽8 ns,波长为532 nm YAG倍频脉冲激光器抽运,向列相液晶作基体,实验分析染料B4400掺杂液晶填充空心光纤荧光光谱选择性荧光放大规律及温度调谐特性.结果表明:通过控制染料浓度可控制荧光输出功率水平;当温度升高时,中心波长发生红移,中心波长调谐范围为590—605 nm;荧光谱宽呈单调展宽,调制范围为228—236 nm;染料掺杂液晶填充空心光纤荧光光源可实现一定范围内的温度调谐.

Tuning characteristics of fluorescent light source by dye-doped liquid crystal filled hollow fiber

The fluorescent fiber light source has been widely used in many areas, such as optical fiber communication and medical imaging, owing to its low cost and wide optical spectrum. The temperature-sensitive refractive index of liquid crystal makes it a suitable filling material used in the fluorescent light source. The existing work has investigated the filling of liquid crystal into the air holes in cladding of photonic crystal fiber. However, the photonic crystal fiber has the disadvantages of complicated craft and high cost. As is well known, the hollow fiber has the advantages of the easy preparation and low cost, but the filling of liquid crystal into the hollow fiber of fluorescent light source is rarely investigated. In this paper, we investigate that a tunable hollow fiber of fluorescent light source is filled with dye doped liquid crystals. The transmission characteristics of the fluorescent light source are theoretically analyzed. The variation in property of the B4400 fluorescent spectrum is numerically discussed with the dye molecule energy level structure theory. The numerical simulation results show that the relative refractive index is dependent on temperature. It first increases linearly with the increase of temperature and then exponentially increases rapidly till clearing point 61.9 C, finally decreases slowly to a saturated value. In order to find an optimum doping concentration, the doping-concentration-dependent fluorescence output intensity is analyzed by using the super continuum spectrum of YAG pump with a wavelength of 1064 nm. The fluorescence light intensities are amplified at three different selective dye doping concentrations, namely 0.2 wt%, 1 wt% and 2 wt% in the experiment, respectively. The highest output is obtained at the 1 wt% doping concentration, which verifies the selective fluorescence amplification property of the fluorescent source. It is also demonstrated that the transmission characteristics and the tunable range of the liquid crystal filled fluorescent light source can be adjusted by modulating the temperature in experiment. And the temperature-dependence of the fluorescence source is experimentally demonstrated by using the 1 wt% doping concentration dye-doped liquid crystal. Using a pulsed YAG pump with a wavelength of 532 nm, tunable characteristics of the fluorescent light source composed of a dye-doped liquid crystal filled hollow fiber, are studied and show that the central wavelength increases from 590 nm to 605 nm and the spectral width broadens from 228 nm to 236 nm with the increase of the temperature. The proposed fluorescent light source can be controlled by adjusting the temperature within limits. These findings will give a guidance for the practical applications of the dye doped liquid crystal based fluorescent light source, and offer a theoretical foundation for the further study of the liquid crystal filled fluorescent fiber light source.