Silicon cross-connect filters using microring resonator coupled multimode-interference-based waveguide crossings

Inverse design of multi-band and wideband waveguide crossings

Photonic integrated circuits for wideband and multi-band optical communications will need waveguide crossings that operate at all the wavelengths required by the system. In this Letter, we use the modified gradient decedent method to optimize the dual-wavelength band (DWB) crossings on both single- and double-level platforms. On the single-level platform, the simulation results show insertion losses (ILs) less than 0.07 and 0.11 dB for a crossing working at a DWB of 1.5-1.6 and 1.95-2.05 µm. ILs are less than 0.1 and 0.2 dB for a crossing operating in the DWB of 1.5-1.6 and 2.2-2.3 µm. On the double-layer platform, the simulated results show IL less than 0.08 dB across the wavelength range of 1.25-2.25 µm. We experimentally demonstrate the DWB crossing operating at 1.5-1.6 and 2.2-2.3 µm to have IL less than 0.3 and 0.4 dB and crosstalk of -28 and -26dB in the two bands, respectively.

Silicon Optical Modulator Using a Low-Loss Phase Shifter Based on a Multimode Interference Waveguide

We have developed a novel phase modulator, based on fin-type electrodes placed at self-imaging positions of a silicon multimode interference (MMI) waveguide, which allows reduced scattering losses and relaxes the fabrication tolerance. The measured propagation losses and spectral bandwidth are 0.7 dB and 33 nm, respectively, on a 987 μm-long phase shifter. Owing to the self-imaging effect in the MMI waveguide, the wave-front expansion to the electrode was counteracted, and therefore, the scattering loss caused by electrode fins was successfully mitigated. As a proof-of-concept for the MMI-based phase modulator applications, we performed optical modulation based on Mach–Zehnder interferometers (MZIs). The π shift current of the modulator was 1.5 mA.

8 x 8 wavelength router of optical network on chip

An integrated 8 x 8 wavelength router based on the micro-ring resonators using 2 x 2 multi-interference (MMI) crossing is demonstrated on silicon-on-insulator (SOI) technology, which is manufactured with microelectronics equipment. Experimental results show a free spectral range (FSR) about ~37 nm, an on/off contrast larger than 20 dB, an imbalance among the channels less than 2 dB, a crosstalk of channels smaller than -10 dB, a spacing between close channels about 3.6 ± 0.7 nm and an output efficiency of every channel smaller than 20 dB.

Reconfigurable SDM Switching Using Novel Silicon Photonic Integrated Circuit

Space division multiplexing using multicore fibers is becoming a more and more promising technology. In space-division multiplexing fiber network, the reconfigurable switch is one of the most critical components in network nodes. In this paper we for the first time demonstrate reconfigurable space-division multiplexing switching using silicon photonic integrated circuit, which is fabricated on a novel silicon-on-insulator platform with buried Al mirror. The silicon photonic integrated circuit is composed of a 7 × 7 switch and low loss grating coupler array based multicore fiber couplers. Thanks to the Al mirror, grating couplers with ultra-low coupling loss with optical multicore fibers is achieved. The lowest total insertion loss of the silicon integrated circuit is as low as 4.5 dB, with low crosstalk lower than −30 dB. Excellent performances in terms of low insertion loss and low crosstalk are obtained for the whole C-band. 1 Tb/s/core transmission over a 2-km 7-core fiber and space-division multiplexing switching is demonstrated successfully. Bit error rate performance below 10⁻⁹ is obtained for all spatial channels with low power penalty. The proposed design can be easily upgraded to reconfigurable optical add/drop multiplexer capable of switching several multicore fibers.

Tilted MMI crossings based on silicon wire waveguide

Waveguide crossings employing tilted MMI structures on silicon wire waveguide are proposed and demonstrated. Intersecting angle of the two MMI waveguides is optimized for low crosstalk. The optimization is carried out with input polarizations specified. On the fabricated MMI crossings, crosstalk lower than -38 dB in the C-band was experimentally confirmed. A novel polarization-insensitive crossing based on a diversity circuit was fabricated. Crosstalk lower than -30 dB in the C-band is demonstrated.

Demonstration of reconfigurable electro-optical logic with silicon photonic integrated circuits

We demonstrate a scalable and reconfigurable optical directed-logic architecture consisting of a regular array of integrated optical switches based on microring resonators. The switches are controlled by electrical input logic signals through embedded p-i-n junctions. The circuit can be reconfigured to perform any combinational logic operation by thermally tuning the operation modes of the switches. Here we show experimentally a directed logic circuit based on a 2×2 array of switches. The circuit is reconfigured to perform arbitrary two-input logic functions.

Optical interconnection networks for high-performance computing systems

Enabled by silicon photonic technology, optical interconnection networks have the potential to be a key disruptive technology in computing and communication industries. The enduring pursuit of performance gains in computing, combined with stringent power constraints, has fostered the ever-growing computational parallelism associated with chip multiprocessors, memory systems, high-performance computing systems and data centers. Sustaining these parallelism growths introduces unique challenges for on- and off-chip communications, shifting the focus toward novel and fundamentally different communication approaches. Chip-scale photonic interconnection networks, enabled by high-performance silicon photonic devices, offer unprecedented bandwidth scalability with reduced power consumption. We demonstrate that the silicon photonic platforms have already produced all the high-performance photonic devices required to realize these types of networks. Through extensive empirical characterization in much of our work, we demonstrate such feasibility of waveguides, modulators, switches and photodetectors. We also demonstrate systems that simultaneously combine many functionalities to achieve more complex building blocks. We propose novel silicon photonic devices, subsystems, network topologies and architectures to enable unprecedented performance of these photonic interconnection networks. Furthermore, the advantages of photonic interconnection networks extend far beyond the chip, offering advanced communication environments for memory systems, high-performance computing systems, and data centers.

Microring-resonator-based four-port optical router for photonic networks-on-chip

We design and fabricate a four-port optical router, which is composed of eight microring-resonator-based switching elements, four optical waveguides and six waveguide crossings. The extinction ratio is about 13 dB for the through port and larger than 30 dB for the drop port. The crosstalk of the measured optical links is less than -13 dB. The average tuning power consumption is about 10.37 mW and the tuning efficiency is 5.398 mW/nm. The routing functionality and optical signal integrity are verified by transmitting a 12.5 Gb/s PRBS optical signal.

Compact and low cross-talk silicon-on-insulator crossing using a periodic dielectric waveguide

We propose and experimentally demonstrate a compact, highly efficient, and negligible cross-talk silicon-on-insulator crossing using a periodic dielectric waveguide. The crossing occupies a footprint of less than 4 μm × 4 μm. Around 0.7 dB insertion loss and lower than -40 dB, cross talk was achieved experimentally over a broad wavelength range.

Fano-resonance-based Mach-Zehnder optical switch employing dual-bus coupled ring resonator as two-beam interferometer

A kind of Mach-Zehnder optical switch with a dual-bus coupled ring resonator as a two-beam interferometer is proposed and investigated. The analysis based on the transfer matrix method shows that a sharp asymmetric Fano line shape can be generated in the transmission spectra of such a configuration, which can be used to significantly reduce the phase change required for switching. Meanwhile, it can also be found that complete extinctions can be achieved in both switching states if the structural parameters are carefully chosen and the phase bias is properly set. Through tuning the phase difference between the arms of the Mach-Zehnder interferometer, complete extinction can be easily kept within a large range of the ring-bus coupling ratios in the OFF state. By properly modulating the phase change in the ring waveguide, the shift of the resonant frequency and the asymmetry of the transmission spectra can be controlled to finally enable optical switching with a high extinction ratio, even complete extinction, in the ON state. The switching functionality is verified by the finite-difference time-domain simulation.

Four-channel reconfigurable optical add-drop multiplexer based on photonic wire waveguide

We designed and fabricated a four-channel reconfigurable optical add-drop multiplexer based on silicon photonic wire waveguide controlled through thermo-optic effect. The effective footprint of the device is about 1000 x 500 microm(2). The minimum insertion loss is about 10.7 dB and the tuning bandwidth about 17 nm. The average tuning power efficiency is about 6.187 mW/nm and the tuning speed about 24.4 kHz. The thermo-optic polarization-rotation effect is firstly reported in this paper.

Optical 4x4 hitless slicon router for optical networks-on-chip (NoC)

We demonstrate here a spatially non-blocking optical 4x4 router with a footprint of 0.07 mm(2) for use in future integrated photonic interconnection networks. The device is dynamically switched using thermo-optically tuned silicon microring resonators with a wavelength shift to power ratio of 0.25nm/mW. The design can route four optical inputs to four outputs with individual bandwidths of up to 38.5 GHz. All tested configurations successfully routed a single-wavelength laser and provided a maximum extinction ratio larger than 20 dB.