편광에 관계없이 매우 짧은 결합길이를 가지는 Double-Sided Deep-Ridge 도파관 구조 수직 방향성 결합기의 소멸비 향상

Abstract

We show that the extinction ratio is improved using slight asymmetry in two core refractive indices of polarization independent very short vertical directional couplers with the double-sided deep-ridge (DSDR) waveguide structure. The optimum asymmetry with the maximum extinction ratio and the tolerance of the refractive index of core with the extinction ratio larger than 30 dB increase as the thickness of inner cladding layer and the two cores decrease due to the increase of the coupling strength between the two cores. Also, the device length and the tolerance of the device length with the extinction ratio larger than 30 dB decrease as the thickness of the inner cladding layer and the two cores decrease due to the increase of the coupling strength between the two cores. We show that polarization independent vertical directional couplers with the DSDR waveguide structure with the device length less than 100 mm and the extinction ratio larger than 30 dB could be implemented.