The study of optic wave propagating in the periodic waveguide structure

• Main Authors: Wang ChunMin, 王浚泯
• Other Authors: Lu RueiChang
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/52254164658166040413

碩士 === 國立宜蘭大學 === 電子工程學系碩士班 === 99 === In this master thesis, we study the optics wave propagating in the periodic waveguide structures, including the photonic crystal and periodic dielectric waveguide structure. For the photonic crystal structure, we can confine the optics wave within the bandgap frequency and then use the line defect structures to propagate the optics wave in it. The transmission power in the photonic crystal is much higher and more stabilizing than tradition waveguide. However, there could be some point defects in the photonic crystal with fabrication errors. Therefore, we investigate the transmission characteristic of the defect in the 90-degree bend structure. From the simulation results, we can found that when the point-defect is nearer the propagating path, the influence of the point-defect is more distinct and leads to the transmission power decreasing. With the distance between the propagating path and point-defect increases, the influence of the point-defect can be decreased. Moreover, the defects in line with the propagating path should be avoided. And, the defects in outer side of the corner bend hardly affect the transmission characteristic, but the defects in inner side do the contrary. Besides, we also found that when the point-defect is far from the propagating path more than three layers, the influence of the point-defect could be ignored. For the other structure, the periodic dielectric waveguides (PDWGs) are consisted of an one-dimension periodical dielectric rods, like a grating pattern, arranged along the propagating direction. In comparison, periodical dielectric waveguides (PDWGs) have the advantages of flexibility and compactness of the structure. The arbitrarily design of the PDWG can be made better than photonic crystal and tradition waveguide. When optics devices are implemented by using the PDWG structure, they can decrease the occupied areas on the chip. However, when we use the PDWG to connect the other devices, it could be exist an issue of mode mismatch in the connect interface. Therefore, we investigate and discuss the influence of the input width and the mode mismatch issue in the circle and square PDWG. From the simulation results, we found that when the dielectric rod radius decreases, the influence of the mode mismatch is more distinct. And we can improve the transmission power and reduce the radiation loss by adjusting the input waveguide width size to obtain the mode matching in the PDWG. Moreover, we suggest that radius of the period dielectric waveguide in PDWG structure should be kept above R = 0.25a otherwise the radiation loss could be increased. Besides, when the wavelength is more than ten times to the lattice constant, the periodic dielectric structure could be regard as the uniform medium. That is, the results of this paper can be used in all kinds of the PDWG shapes. Last, we use a hexangular circularity structure in PDWG structure to design various power splitters. This power splitter contain five types: the one branch splitter, the two branch splitter, the three branch splitter, the four branch splitter, and the five branch splitter. The operating principle in this structure is used by the wavelength interfered in hexangular circularity structure. With the wavelength interference of constructive or destructive interference, the output positions and powers are coordinated with the input optical frequencies. Furthermore, we can combine those optical power dividers, such as the one branch and the four branch, to form a wavelength splitter.