A photonic lantern is studied which is formed by seven multimode fibers inserted into a pure silica capillary tube. The core of the tapered end has a uniform refractive index because the polymer claddings are removed before the fibers are inserted. Consequently,the light distribution is also uniform. Two theories describing a slowly varying waveguide and multimode coupling are used to analyze the photonic lantern. The transmission loss decreases as the length of the tapered part increases. For a device with a taper length of 3.4 cm,the loss is about 1.06 dB on average for light propagating through the taper from an inserted fiber to the tapered end and 0.99 dB in the reverse direction. For a device with a taper length of 0.7 cm,the two loss values are 2.63 dB and 2.53 dB,respectively. The results show that it is possible to achieve a uniform light distribution with the tapered end and a low-loss transmission in the device if parameters related to the lantern are reasonably defined.
Hai-Jiao YuQi YanZong-Jun HuangHe TianYu JiangYong-Jun LiuJian-Zhong ZhangWei-Min Sun
将5种不同折射率的液晶分别填入实芯光子晶体光纤的空气孔中,通过改变外场条件,研究其输出光谱的变化规律,并进行了理论模拟分析.结果表明:填充液晶后,输出光谱由全通变为多个波峰的带隙式;同时,液晶的折射率差值越大,其波峰位置越向长波长方向移动,且相对光强的对比度可以达到16 d B;温度由20°C上升到85°C时,波峰向短波长方向移动,最大调控范围可达41 nm;调节电压从0—250 V,输出光谱的相对光强变小,但波峰具有较好的稳定性;在室温下,波峰不随入射光偏振态的变化而变化.该液晶光子晶体光纤可应用于温控可调谐滤波器或电控衰减器.
We demonstrate a new kind of multi-core photonic liquid crystal fibers (PLCFs) which have six liquid crystal cores arrayed in the ring-type geometry and separated by the air holes. Through analyzing the structure of this kind of PLCFs, it can be found that they have the ability to resist the structure deformation. Due to the effective index of the liquid crystal can be adjusted by temperature and wavelength, the energy in the six liquid crystal cores is increased with the temperature increasing and wavelength decreasing. The effective index of the PLCFs is decreased, the effective fundamental mode area is increased and the dispersion properties are gently affected with the wavelength increasing and temperature decreasing.
In this Letter,a dye-doped cholesteric liquid crystal(DDCLC)-filled hollow glass microsphere is demonstrated to be a resonator with good temperature response.A diglycerol layer is used to wrap the DDCLCs microdroplet to keep it steady and control its orientation.The whispering gallery mode(WGM)lasing and photonic band gap(PBG)lasing caused by two different mechanisms were obtained under the pump of a pulsed laser,and the temperature response of these two kinds of lasing was studied.For the liquid crystal and chiral material used in this Letter,both the WGM lasing and the PBG lasing have a blue shift in wavelength with increasing temperature.
基于向列相液晶指向矢随施加电场作用发生变化的特性,结合几何光学和液晶理论提出了一种液晶透镜结构模型,研究了电极大小、隔垫物厚度等液晶透镜参数对液晶透镜焦距的影响.通过优化参数,得到结构简单、变焦范围较大的新型液晶透镜样品,在驱动电压0 V_(RMS)-250 V_(RMS)下可调的焦距范围为75-230 mm,达到155 mm.
