Study On Slow Light Characteristics Based On Photonic Crystal Waveguide And OCT Resolution Measurement

Slow light technology has important applications in various fields such as optical buffer,optical communication and nonlinear optics.Among various slow light generation methods,the slow-light based on two-dimensional photonic crystal has characteristics of good operability,wide working frequency range,and easy integration with existing optical system.In this paper,a two-dimensional photonic crystal coupled cavity waveguide has been studied based on plane wave expansion method and finite-difference time-domain method.By changing the structural parameters of the waveguide,the slow-light characteristics of photonic crystals have been optimized.And a coupling method of photonic crystal waveguide with large bandwidth and low loss has also been presented.Then,to achieve a slow-light tunable delay,an all-fiber system based on the combination of four-wave mixing and dispersion in optical fiber has been studied.Finally,a system for measuring the resolution of OCT equipment has been designed and studied in this paper,which can be used to realize the convenient and accurate measurement of OCT equipment resolution parameters.The main contents of this paper are as follows:1.Based on the plane wave expansion method,a coupled cavity-type two-dimensional square lattice photonic crystal waveguide has been studied and optimized.When setting the normal dielectric column radius as r=0.30a,the coupled cavity waveguide exhibits a band gap of 0.139282?a/2?c.When the defective dielectric column spacing is n=2,and the radius of the defective dielectric column is r_d(28)0.20a,the delay-bandwidth product of the coupling cavity is maximal,with the minimum slow group velocity is 0.077307c and normalized delay-bandwidth product is 0.279.Corresponding to the center wavelength of 1550 nm,the bandwidth equals to33.40 nm.Considering the processing difficulty and performance,several coupling methods have been analyzed.Finally,it is concluded that adding the step coupling waveguide between the ridge waveguide and the slow waveguide has the best performance.2.Tunable slow-light delay based on the combination of four-wave mixing wavelength conversion and fiber dispersion has been studied in this paper.Firstly,high efficient four-wave mixing in dispersion flattened high nonlinear fiber is obtained.When fixing the wavelength of the signal at 1549.3 nm and decreasing the wavelength of the pump light from 1549.3 nm,a maximum conversion bandwidth of28.4 nm has been obtained experimentally.In this case,the wavelength of the higher frequency idler light is 1520.9 nm.Secondly,based on the maximum four-wave mixing wavelength conversion bandwidth,a maximum delay up to 12.1 ns has been achieved,and the time delay is tunable in the range of 0~6 ns.3.By analyzing the key parameters of OCT equipment,a set of miniaturized spatial resolution detection system for commercial OCT equipment has been designed.And large-scale commercial equipment is used to give a comparison experiment on measuring the same OCT equipment.The measured OCT axial and transverse resolutions are 6.9?m and 42.3?m respectively,which are similar to the measurement results of the commercial equipment.It means the miniaturization measurement system has a good reference,and it also has good performance in integration,operability and portability.