Author Affiliations
1State Key Laboratory for Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Zijingang Campus, Hangzhou 310058, China2International Research Center for Advanced Photonics, Zhejiang University, Haining 314499, Chinashow less
Fig. 1. Schematic configurations of the proposed calibration-free elementary 2×2 MZS. (a) Overview; (b) cross section of the phase-shifter; (c) TES-bend and the bent-ADC mode filter.
Fig. 2. (a) Local angle θ and the curvature radius R, and (b) the core width w as functions of the curve length L for the first half of the TES-bend.
Fig. 3. Simulation results for the designed 2×2 MZS. Calculated transmissions of the designed TES-bend (a) without and (b) with the bent-ADC mode filter, respectively. Insets, simulated light propagations when the TE0 and TE1 modes are launched, respectively. (c) Calculated transmissions of the MMI coupler connected with the TES-bends. Inset, simulated light propagation for the launched TE0 mode. (d) Calculated transmissions at the cross and bar ports of the designed MZS in the Off state.
Fig. 4. (a) Calculated total phase imbalance for the new MZS consisting of TES-bends as well as arm waveguides with different core widths of 1, 2, and 3 μm; here the mean width difference δw varies from 1 nm to 20 nm; the result for conventional MZSs with 450-nm-wide arm waveguides is also given; (b) the itemized phase imbalance as the core width wco varies. The results for the conventional MZS with 450-nm-wide S-bends are also included for comparison.
Fig. 5. (a) Optical microscope image of the fabricated 2×2 MZS; (b) measured transmissions at the cross/bar ports for the central wavelength when sweeping the heating power Q from 0 to 80 mW; (c) measured transmissions at the cross/bar ports of the present MZS operating at the Off/On (cross/bar) states (i.e., Q=0 and 34 mW, respectively); (d) summary of the measured phase imbalances for all the MZSs (Designs A, B, C, and D) from 11 chips in the same fabrication batch. Design A is with the TES-bends and 2-μm-wide phase-shifters; Design B is with the TES-bends and 1-μm-wide phase-shifters; Design C is with the conventional 0.45-μm-wide S-bends and 2-μm-wide phase-shifters; Design D is with the conventional 0.45-μm-wide S-bends/phase-shifters.
Fig. 6. (a) Optical microscope image, and (b)–(e) measured all-cross transmissions Tij at the output port Oj with the port Ii importing when i=1, 2, 3, and 4, respectively, with no calibration for all the six MZSs. (f)–(i) Measured all-bar transmissions Tij, where the signals launched from input ports I1, I2, I3, and I4 are routed to output ports O1, O2, O3, and O4, respectively.
Fig. 7. Synthesized eye-diagrams at port (a) O1, (b) O2, (c) O3, and (d) O4 of the present 4×4 MZS in the all-cross states. Here the bit rate is 30 Gb/s.
Fig. 8. Adiabatic taper with different shapes. (a) Structure. (b) Calculated excess loss for the TE0 mode. (c) Calculated mode excitation ratio to the TE1 mode. Here wco=2 μm and w1=0.9 μm.
Fig. 9. Simulated transmission spectra of the 2×2 MMI coupler, including the TE0 and TE1 modes at the cross and through ports.
Fig. 10. Calculated effective indices of the TE modes of 220-nm-thick silicon waveguides.
Fig. 11. (a), (b) Optical microscope images of TES-bend. (c) The measured transmissions for the testing structures with a number of TES-bends in cascade.
Fig. 12. Measured transmissions of the fabricated 4×4 MZS with Benes network in (a), (b) (10|00|00) state; (c), (d) (01|00|00) state; (e), (f) (00|10|00) state; (g), (h) (00|01|00) state; (i), (j) (00|00|10) state; (k), (l) (00|00|01) state.