Design and Fabrication of PolarizationIndependent MicroRing Resonators.pdf

CHIN.PHYS.LETT. Vol. 25, No. 4 (2008) 1333 Design and Fabrication of Polarization-Independent Micro-Ring Resonators GENG Min-Ming()∗∗ , JIA Lian-Xi(), ZHANG Lei(), LIU Yu-Liang(), YANG Lin(), LI Fang() Laboratory on Optoelectronic Systems, Institute of Semiconductors, Chinese Academy of Sciences, PO Box 912, Beijing 100083 (Received 7 November 2007) Origin of polarization sensitivity of photonic wire waveguides (PWWs) is analysed and the effective refractive indices of two different polarization states are calculated by the three-dimensional full-vector beam propagation method. We find that PWWs are polarization insensitive if the distribution of its refractive index is uniform and the cross section is square. An MRR based on such a polarization-insensitive PWW is fabricated on an 8-inch silicon-on-insulator wafer using 248-nm deep ultraviolet lithography and reactive ion etching. The quasi-TE mode is resonant at 1542.25 nm and 1558.90 nm, and the quasi-TM mode is resonant at 1542.12 nm and 1558.94 nm. The corresponding polarization shift is 0.13 nm at the shorter wavelength and 0.04 nm at the longer wavelength. Thus the fabricated device is polarization independent. The extinction ratio is larger than 10 dB. The 3 dB bandwidth is about 2.5 nm and the Qvalue is about 620 at 1558.90 nm. PACS: 42. 82. −m, 42. 79. −e, 42. 60. Da The ring resonator is a versatile device that The polarization sensitivity of the PWW is caused can be used to construct many optical devices, by its asymmetric structure and the asymmetric dis- such as switches,