| dc.description.abstract | Silicon waveguides are fabricated on insulators of silicon wafers that have been widely used in integrated photonic circuits. Various components such as photonic crystal resonators have been realized. In optical quantum computing, qubits are defined by the polarization state of light. Therefore, the polarization rotators are necessary to be used to control the state of qubits or to form logic gates.
In this study, we propose a novel photonic-crystal structure on SOI waveguides. The photonic crystal structure is shifted to the center of the waveguide to form a reflective polarization convertor. A resonant cavity is designed in the polarization convertor. The transmission and the reflection and the cavity modes are investigated. Three methods, Finite-Difference Time-Domain, Finite-Element Method, Eigenmode expansion method are adopted.
The rotation of polarization is demonstrated in the photonic crystal structure with shifted circular air holes. The rotation of the polarization depends on the diameter, the shift, the number of the air holes. With a cavity in the structure, the cavity modes can be observed in the transmission and the reflection spectra. The polarization state of the transmission and reflection of the devices can be designed by varying the diameter, the shift, the number of the air holes.
The photonic crystal structure with shifted rectangular holes is also investigated. The reflectivity close to 100% could be achieved for the photonic crystal structure with 100 shifted rectangular holes. A cavity is positioned in the structure to study the transmission and the reflection spectra as well as the cavity modes. The results show that the photonic crystal structure with shifted rectangular air holes can be used to form the transmissive and the reflective filters with a rotation of polarization. The wavelength of the cavity mode and the transmissive and reflective filter can be tuned by modifying the cavity length. By varying the number of etched rectangular air holes , the duty cycle, the width and the depth of the etched rectangular air holes, the polarization of the output light can be adjusted to a specific state.
In this study, the waveguide is designed in silicon. The photonic crystal structure with shifted air holes can also be designed in other active materials to design a laser with specific polarization state. | en_US |