Fig. 1. Fabrication and characterization of the suspended phase shifter. (a) Post process for phase shifter’s suspension. (b) The SEM image of a cross-sectional view of a fabricated suspended phase shifter. (c) Normalized optical transmission against the heating power when employing a suspended or a normal phase shifter within the MZI. (d) The numerical and experimental curves of tuning efficiency of suspended and normal phase shifters. (e) The temporal optical response curve of a suspended or a normal phase shifter to square-wave voltage signals. (f) Phase errors induced by thermal crosstalk in both normal and suspended phase shifters.

Fig. 2. (a) Schematic diagram of the a 6-mode linear photonic processor using Clements’ architecture. (b) Microscope image of the 6-mode interferometer with suspended phase shifters.

Fig. 3. Calibration and characterization of the device. (a) The experimental testing setup (TLS, tunable laser; FPC, fiber polarization controller; DUT, device under test; PM, power meter; FPGA, field programmable gate array; DAC, digital-to-analog converter). (b) Detailed view of the device under test on a coupling stage. (c) Transmittance spectrum of the calibrated device. (d) Statistics of the half-wave consumption of the internal phase shifters. (e) Statistics of the extinction ratio of all the MZIs. (f) Prediction of insertion loss and power consumption with increasing scale for our device.

Fig. 4. Experimental 6-mode linear transformation. (a) Measured matrices for all integer powers of 6D cyclic transformations (X-gates). (b) Theoretical and measured transmission matrices of arbitrary 6D unitary transformations SU(6)1 and SU(6)2.

Fig. 5. (a) Schematic of the lateral layout of phase shifters. (b) Phase shifters with a dense lateral arrangement. (c) Phase shifters with a reasonable lateral spacing.

Fig. 6. Schematic diagram of matrix decomposition for a rectangular interferometer. (a) Correspondence of the 2D unit matrices with the basic unit blocks and the order of their multiplication. (b) Connection of external phase shifters in slices.

Fig. 7. Calibration flow of the external phase shifters for our SISO testing strategy.

Fig. 8. Configuration for the integer powers of cyclic transformation (X-gate).

Table 1. Overview of MZI-Based Photonic Processors Working around 1550 nm