Researching On Filter And Sensing Characteristics Of Liquid Crystal Photonic Crystal Fiber Of Terahertz Wave

THz region that lies between the millimeter and infrared region have superior characteristics. The research of THz wave of in recent years become more and more hot, its application in the science research and daily life is much more than before, such as in the areas of THz space application, atmosphere science, security detection and so on. However,direct application of the terahertz wave is still relatively small, mainly because of its free-space propagation loss is large. The research and development of terahertz waveguide devices become the key to whether the THz can be widely used.Unlike conventional fiber, photonic crystal fiber has many periodic arrangement of air holes in cladding, this special structure makes photonic crystal fiber has many excellent properties. Photonic crystal fibers are proposed and studied for some time, if we do some research on it combining with the THz technology, it will open a new road to study the THz waveguide devices. Filled with liquid crystal in the air holes can change the structure of photonic crystal fiber parameters and broaden the research scope.this paper first study the optical properties of liquid crystals, then select 5CB liquid crystal as the material filled in PCF. And explores its characteristics of temperature and voltage.Studying the structural properties of photonic crystal fibers, summing up and sorting the current mainstream of some numerical analysis method. Selecting the finite element method as the paper choose. This method propose a rule of choosing parameters when studying two-dimensional photonic crystal fiber with a periodic structure.In this article, using the liquid crystal doped photonic crystal fiber to research THz wave filtering and sensing properties.In terms of tuned filter, using characteristics that liquid crystal refractive index is easy to control to put forward a kind of brand-new THz filter design, which is that filling the air holes with 5CB LC in the PCF, and then by controlling the liquid crystal birefringence to tune the band gap of photonic crystal fiber and change terahertz transmission frequency to achieve the purpose of tuning filter. Discussing the arrow model, which can predict the maximum loss points of bandgap photonic crystal fiber. The research on bandgap PCF switch and filter characteristics proves arrow model is correct. So, we can use the arrow model to design the structure of the PCF to achieve a specific band tunable filter.In the term of sensor, using the tunable characteristic of liquid crystal, this article study the temperature and electric sensing properties of bandgap PCF, and compare the different characteristics of effective refractive index, confinement loss and effective mode area.