Fig. 1. Proposed 4-HEX MCR-PPIC. (a) 3D schematic view of the 4-HEX MCR-PPIC. (b) Edges and ports numbering of the 4-HEX MCR-PPIC. (c) Detailed view of the cell structure in the MCR-PPIC. (d) Cross-sectional view of the structure of the thermal phase shifter above the MZI’s spiral waveguides and micro-ring resonators. (e) Wire bonding microscope diagram of the fabricated chip. (f) Microscope diagram of the 4-HEX MCR-PPIC.

Fig. 2. Structure and principle schematics of subcomponents within the proposed MCR. (a) Structure and principle schematic of the MZI subcomponent within the MCR. (b) Structure schematic of the spiral waveguide used as interference arms. (c) Principle schematic of an add-drop micro-ring resonator. (d) Principle schematic of add-drop parallel double-ring resonators. (e) Structure schematic of the PDRR subcomponent within the MCR.

Fig. 3. Experimental results of configuring different photonic functions using MZI subcomponents. (a-i) Optical path configuration and (a-ii) the corresponding spectra of the configured BMZI. (b-i) Optical path configuration and (b-ii) the corresponding spectra with a tunable extinction ratio of the configured UMZIs with a distance difference of 4×BUL. (c-i) Optical path configuration and (c-ii) the corresponding spectra compared with 4×BUL of the configured UMZIs with a distance difference of 6×BUL. (d-i) Optical path configuration and (d-ii) the corresponding spectra with tunable extinction ratio of the configured all-pass ring resonator with a cavity length of 6×BUL. (e-i) Optical path configuration and (e-ii) the corresponding spectra with a tunable extinction ratio of the configured add-drop ring resonator with a cavity length of 6×BUL. (f-i) Optical path configuration and (f-ii) the corresponding spectra of the configured add-drop ring resonator with different cavity lengths. (g-i) Optical path configuration and (g-ii) the corresponding spectra of the configured series double-ring filter. (h-i) Optical path configuration and (h-ii) the corresponding spectra of the configured single-ring assisted MZI. (i-i) Optical path configuration and (i-ii) the corresponding spectra of the configured 4×4 optical routers. CS: cross state; BS: bar state; TC: tunable coupler; VA: vacant state; C/B: cross state or bar state, no intermediate states. PDRRs are omitted from the optical path.

Fig. 4. Experimental results of discrete time delay tuning using MZI subcomponents. (a) Spectral results and (b) corresponding delay results for discrete delay tuning by using a cascade of MZI subcomponents.

Fig. 5. Experimental results of configuring basic photonic functions using PDRR subcomponents. (a) Bandpass filter with a tunable passband bandwidth. (b) Flat-top bandpass filter with a tunable center wavelength. (c) Bandstop filter with a tunable stopband depth. (d) Bandstop filter with a reconfigurable stopband width. (e) Bandstop filter with a tunable center wavelength. (f) Fano line filter with a tunable spectral resolution. The variable s in the legend represents the spectral resolution. (g) Spectral results and (h) corresponding delay results for continuous delay tuning using the PDRR subcomponents. The insets in the spectra are schematic sketches of the corresponding optical paths. The ring resonators labeled in yellow in the insets are active. The legend in (a), (c), (e) illustrates the serial numbers of the micro-rings involved in the reconstruction.

Fig. 6. Experimental results of configuring a tunable WDM system using PDRR subcomponents. (a) Optical path configuration of the four-channel WDM system, with dashed lines indicating unused rings or waveguides. (b) WDM system channel scalability test. (c) WDM system channel spacing tunability test. (d) WDM system channel bandwidth tunability test. The z axis in (c), (d) characterizes the values of the voltages loaded on the different micro-rings. The color of the circles in each row of the array corresponds to the schematic in (a). Each column in the array contains two data separated by a slash, the former representing the voltage loaded on Ring-1 and the latter representing the voltage loaded on Ring-2.

Fig. 7. Experimental results of a multi-channel fractional-order time-domain differentiator using PDRR subcomponents. (a) Optical time-domain differentiation calculation experiment using Ring-I1. (b) Comparison of differentiation results with theoretical calculations. (c) Differentiator spectra and signal spectra before and after processing. (d) Optical time-domain differentiation calculation experiment using Ring-I2. (e) Comparison of differentiation results with theoretical calculations. (f) Differentiator spectra and signal spectra before and after processing.

Fig. 8. Experimental link diagram. (a) Spectral response test. (b) Group delay response test.

Fig. 9. Experimental characterization of the MCR as a tunable coupler. (a) Schematic of the MCR bar state optical path; (b) schematic of the MCR cross state optical path; (c) schematic of the MCR 3 dB splitting state optical path; (d) spectral results of different states of the MCR as a tunable coupler.

Fig. 10. Experimental characterization of the MCR as double ring resonators. (a) Schematic of the micro-ring optical path with the MZI in cross state, and the results when (b) tuning VMRR1, (c) tuning VMRR2. (d) Schematic of the micro-ring optical path with the MZI in bar state, and the results when (e) tuning VMRR1, (f) tuning VMRR2.

Fig. 11. Spectral results of tuning rings with the MZI in the 3 dB state. (a) Spectral results when untuned. (b) Non-FSR band spectra varying with heating power.