Polarization Control Of Selectively Filled Photonic Liquid Crystal Fibers

Long baseline stellar interferometry technology is one of the main means to achieve high spatial resolution astronomical observations.The long baseline stellar interferometer achieves image reconstruction by collecting phase and amplitude information from interference patterns of light signals from two or more telescopes.Long baseline stellar interference technology overcomes the diffraction limit resolution of a single telescope,achieving astronomical exploration at sub nanosecond angular resolution.It has played a huge role in studying planetary formation,understanding the basic physics of stars,and uncovering the structure of active galactic nuclei.In the era of ultra large telescopes,stellar interferometry technology still plays a crucial role in making groundbreaking discoveries in astronomical research.Optic fiber,as an important medium for optical signal transmission,has characteristics such as low transmission loss and flexible transmission paths.It plays a role in simplifying the interface between observation equipment and telescopes,achieving the separation of astronomical telescopes and observation equipment.When light waves propagate in optical fibers,their polarization state is easily affected,leading to unstable interference signals and reducing stripe visibility.Photonic liquid crystal fiber(PLCF),as a fiber that combines the structure and optical properties of photonic crystal fiber(PCF)and liquid crystal(LC),its addition makes PCF more convenient for controlling electromagnetic fields,temperature,pressure,stress,and other fields.LC not only has the optical properties of crystals,but also has the fluidity of liquids.LC molecules can be arranged according to certain rules within a certain temperature range.When LC is filled into PCF to form PLCF,the presence of LC can cause phase delay of light passing through PLCF.The electric field can deflect the directionality of LC molecules,and the size of the polarization angle is related to the size of the electric field.Therefore,polarization control can be achieved by changing the size of the electric field.Finite element simulation analysis was conducted on PLCF with different filling methods,and this performance was particularly evident at an incident light wavelength of1550 nm.As the number of filling turns increases,the phase modulation ability of PLCF slightly increases.The impact of filling the outer ring with two to five cycles of LC on the polarization control performance of PLCF was studied.It was found that filling the outer air hole with liquid crystal has very little effect on the polarization control performance of PLCF.Finite element simulation analysis was conducted on the polarization control of PLCF controlled by electric field with different incident light wavelengths and duty cycle.The difference in effective refractive index showed significant linearity in the infrared wavelength range of 1200-1600 nm,and the difference in effective refractive index increased with increasing wavelength.In addition,fully filled PLCF has a narrower wavelength range for guided modes compared to selectively filled PLCF.By changing the duty cycle,it was found that the larger d/(43),the greater the fluctuation of its effective refractive index value.When d/(43)is 0.7,0.8,and 0.9,no non guided light bands were found in the 400-1600 nm wavelength range.Comparing the curves with d/(43)values of 0.5 and 0.6,no guided modes were found in the range of 1100-1200 nm for d/(43)values of 0.5,while no guided modes were found in the range of 1325-1425 nm for d/(43)values of 0.6.Finally,different selective filling methods were compared and the coating filling method was chosen as the preparation method for PLCF.Successfully prepared selectively filled PLCF and utilized capillary phenomenon to fill the air pores of PLCF,filling LC into the air pores of PCF to form PLCF.Comparing the three cases of no PLCF,no power supply with PLCF,and power supply with PLCF,it is found that light will become elliptically polarized after passing through PLCF,and the property of elliptically polarized light will change with the change of voltage.When continuously changing the voltage,as the voltage increases,the change in transmitted light is relatively stable before 580 V,showing a downward trend from580 V to 880 V,reaching the lowest value at 880 V,and then showing an upward trend.The data curve can basically reflect the rotation of the deflection angle,and the change in light intensity can reflect the influence of electric field on the deflection angle of liquid crystals,indicating that it can be used for polarization modulation and compensation in stellar interferometers.