Research On All-Optical Buffering Capability And Dynamic Modulation Based On Photonic Crystal Slow Light

All-optical buffer have been considered as a key component for all-optical communications since network throughput, packet loss rate, channel competition of network node, all require optical buffer. And it is essential to completely break the "electronic bottleneck" in the optical communication systems. However, the existing optical buffer schemes are difficult to realize in practical application. Therefore, the research on novel optical buffer is of great importance. Compared with other slow light technologies, photonic crystal slow light has significant advantages and considerable potential for optical buffering application. This thesis studied the buffer performance of photonic crystal slow-light waveguides. The main results in this thesis are as follows:Firstly, the buffer capability and dynamic modulation in line-defect photonic crystal slab waveguides are studied. In the proposed structure, we obtain the negligible dispersion bandwidth for the requirement of optical buffers ranging from 2.8nm to 13.8nm and the corresponding constant group velocity ranging from c/38 to c/105. In addition, the center wavelength shift, delay time and storage capacity increase almost linearly as the applied voltage rising. And the modulation sensitivities are about 0.386nm/V, 0.8ps/V and 0.37bit/V, respectively. In practical buffering application, the dynamic modulation characteristics can be utilized to the slow light frequency selection in multiple wavelength system, the manipulation of storing and releasing slow light pulses with given frequency, and the tuning of delay time and storage capacity.Secondly, the buffering capability and limitations in low dispersion photonic crystal waveguide with elliptical air holes are investigated. The results show that adjusting the major and minor axes can bring low group velocity and low dispersion properties. Moreover, the group velocity and the negligible-dispersion bandwidth can be balanced by tuning the position and the hole size of the first row appropriately. In the proposed structure, we obtained the constant group velocity ranging from c/41 to c/256 and the corresponding negligible-dispersion bandwidth ranging from 1.23nm to 8.1nm, which satisfy the requirement of optical buffers. In addition, the maximum buffer capacity, the maximum data rate and delay time can reach as high as 262bit,515Gb/s and 255.4ps in the proposed structureⅡ, respectively.Finally, the buffer performances and dynamic modulation in photonic crystal coupled-cavity waveguide are systemically studied. The slow light and buffer performances of PC-CCW are optimized by adjusting the cavity spacing and the hole size around the cavity. In the optimized structure, the group velocity is below 2.713×10-4c. The corresponding delay time, buffer capacity and Q factor can reach as high as 12.286ns,68.5bit and 3525, respectively. Furthermore, when the applied voltage increases, the buffer capacity and bit length are unchanged while the wavelength shift and delay time decrease almost linearly. And the modulation sensitivities are about 3.726nm/mV and 0.875ns/mV, respectively. The Q factor also decreases accordingly when the applied voltage increases.In summary, these results provide important theoretical basis for realizing of optical buffer based on photonic crystal slow light in all-optical network.