On-chip optical narrowband reflector based on antisymmetric Bragg grating

摘要

We propose an on-chip optical narrowband reflector (NBR) based on two cascaded Bragg gratings (BGs).A π phase shifted anti-symmetric Bragg grating (π-PS-ASBG) and a rear uniform Bragg grating (UBG),are in-line connected. The π-PS-ASBG provides a hybrid mode resonance between the even- and oddTE (TE_0 and TE_1) modes, while the UBG is used as a rear reflector to reflect the TE_0 mode thattransmitted from the π-PS-ASBG. The reflection bandwidth decreases when the coupling coefficientincreases, which is different from traditional UBG. The performances are theoretically studied via boththe rigorous three-dimensional finite-difference time-domain (3D-FDTD) method and multimodetransmission matrix method (MTMM). The calculated 3-dB bandwidth is 0.16 nm when the wholegrating length is 400 μm (π-PS-ASBG: 200 μm and UBG: 200 μm) and the coupling coefficients of theπ-PS-ASBG and rear UBG are 240cm~(-1) and 110cm~(-1), respectively. The proposed NBR can be applied inthe cases requiring narrow reflection such as narrow linewidth semiconductor lasers.