We fabricate a 32 × 32 silicon photonics switch on a 300-mm silicon-on-insulator wafer by using our complementary metal-oxide-semiconductor pilot line equipped with an immersion ArF scanner and demonstrate an average fiber-to-fiber insertion loss of 10.8 dB with a standard deviation of 0.54 dB, and on-chip electric power consumption of 1.9 W. The insertion loss and the power consumption are approximately 1/60, and less than 1/4 of our previous results, respectively. These significant improvements are achieved by design and fabrication optimization of waveguides and intersections on the chip, and by employing a novel optical fiber connector based on extremely-high-Δ silica planarlightwave-circuit (PLC) technology. The minimum crosstalk was −26.6 dB at a wavelength of 1547 nm, and −20-dB crosstalk bandwidth was 3.5 nm. Furthermore, we demonstrate low-crosstalk bandwidth expansion by using output port exchanged element switches. We achieve a −20 dB crosstalk bandwidth of 14.2 nm, which is four-times wider than that of the conventional element switch based 32 × 32 switch.

A precise flip-chip bonding (FCB) technology for indium phosphide semiconductor optical amplifiers (InP-SOAs) on a silicon photonics platform within less than ±1-µm alignment accuracy was developed. For efficient optical coupling and a relaxed alignment tolerance, the mode field on both the InP-SOAs and the Si waveguides was expanded by spot-size converters (SSCs). On the InP-SOAs, width-tapered SSCs were used to obtain an isotropic mode-field having an approximately a 3-µm diameter. On the silicon photonics platform, dual-core SSCs were used to expand the same mode-field size of 3 µm as for the SSCs on SOAs. Using the FCB technology and the SSCs, an in-line optical amplification of 15 dB was achieved by in-line integrated SOAs with angled waveguides. The optical coupling losses were 7.7 dB, which included 5.1-dB excess losses by misalignment and a gap between InP-SOA and Si waveguides. A 4 × 4 Si switch with a hybrid-integrated 4-ch SOA array was fabricated, and achieved the first demonstration of a lossless Si switch.

Researchers experimentally demonstrate on-demand transfer of trapped photons on a photonic crystal chip for the first time.

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We fabricate and characterize a polarizationdiversity 32 × 32 silicon photonics switch by newly introducing SiN overpass waveguides onto our nonduplicate polarization-diversity path-independent insertion-loss switch. The SiN overpass waveguides are used to simplify the optical paths with a uniform path length between the edge couplers and the switch matrix and significantly reduce the number of waveguide intersections. The switch chip is fabricated using a 300-mm silicon-on-insulator wafer pilot line. The fabricated switch comprises more than 7,600 components, making this the largest ever complementary-metal-oxidesemiconductor-based silicon photonics circuit. The switch chip is electrically and optically packaged and evaluated for a sampled port connection with 32 paths, with an average on-chip loss of ∼35 dB and an average polarization-dependent loss of 3.2 dB where 75% of the measured paths exhibit a loss of less than 3 dB. The differential group delay is measured to be 1.7 ps. The performance can be further improved by optimizing the device design.

We experimentally demonstrate the lossless transmission of wavelength division multiplexing (WDM) signals through a silicon-photonics 4 × 4 switch with a flip-chip bonded 4-channel semiconductor optical amplifier (SOA). We first optimized the input power and gain of the SOA-integrated switch to obtain the optimum operation point in terms of the transmitted signal quality. We then performed simultaneous transmission of 8-ch, 32-Gbaud, SP 16-QAM WDM (800 Gb/s) signals through all the four paths of the switch. The effect of crosstalk on the switch was very small, and thus could not be observed. We also examined multistage (up to four stages) transmission of the signals with circulating configurations. We show that even for a 4-stage transmission, the bit error rate of the transmitted signal is below the 20% forward-error-correction limit. Finally, we discuss approaches to improve the optical signalto-noise ratio of the transmitted signals to enlarge the signal quality margin and increase the possible number of the cascading stages and/or WDM channels for wide applications.

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We review the research progress of strictly nonblocking optical switches based on silicon photonics. We have developed a switch chip fabrication process based on a complementary metal-oxide-semiconductor pilot line and optical and electrical packaging technologies. We demonstrated all-paths transmission and switching of up to 32 input ports × 32 output ports with an average fiber-to-fiber insertion loss of 10.8 dB. Furthermore, we demonstrated an operating bandwidth wider than 100 nm for −30 dB crosstalk with double-Mach-Zehnder element switches in an 8 × 8 switch. For polarization-insensitive operation, we adopted a polarization diversity scheme and fabricated an 8 × 8 switch with fiber-based polarization-beam-splitters and two switch chips. The 8 × 8 switch exhibited a polarization-dependent loss of less than 0.5 dB. Moreover, an on-chip polarization diversity 8 × 8 switch integrated with polarization splitter rotators and two switch matrices on a single chip demonstrated a differential group delay less than 1 ps. Based on current technologies, we discuss the prospects for further port count expansion and remaining challenges for commercial deployment.