Fig. 1. Schematic drawing of PCDR resonators.

Fig. 2. Coverage of the coherent output states for Δn1, Δn3=−0.001−+0.001, under different Q1 and c1. A potential QPSK constellation is shown in the top right case.

Fig. 3. Variation of the output amplitude under the condition Δθ1=−Δθ3 (a) for various levels of Δn=0, 0.0005, 0.001; and (b) for a phase shift Δθ1=−Δθ3=π, which gives the maximum real value of Eout. Note that the scale of the vertical axes in (a) and (b) are different.

Fig. 4. Coverage of coherent output states for Q1=30000 and Δn1, Δn3=−0.001−+0.001 (a) c1=0.46, (b) c1=0.47, (c) c1=0.48, and (d) c1=0.49. (e) Eout(Δθ,−Δθ) for different c1.

Fig. 5. Coverage of coherent output states for Q1=30000 and c1=0.45, for Δn1, Δn3=−δn−+δn. (a) δn=0.0005, (b) δn=0.001, (c) δn=0.0015, (d) δn=0.002. (e) The variation of the Eout(Δθmax,−Δθmax) with δn.

Fig. 6. Influence of the structure asymmetry in dual-racetrack resonators. The red and blue lines represent Eout(0,0) and Eout(Δθmax,−Δθmax) for δn=0.001, respectively, for an ideal structure whose parameters are the same as Fig. 5. The symbols represent the results for a structure (a) with 20% asymmetry in κ, and (b) with 20% asymmetry in the quality factor.