Yangyang Lu

Demonstration of directed XOR/XNOR logic gates using two cascaded microring resonators

We propose and demonstrate a directed optical logic circuit that can perform the XOR and XNOR logic operations consisting of two cascaded microring resonators, i.e., an upper waveguide and an under waveguide. No waveguide crossings exist in the circuit, which is very useful to improve the signal quality and reduce the insertion loss of the device. As proof of principle, XOR and XNOR logic operations with the speed of 10 kb/s are successfully demonstrated. In addition, numerical simulation results indicate that the length difference between the upper waveguide and the under waveguide can change the output spectrum characteristics of the device, which acts like a Mach-Zehnder interferometer (MZI).

Five-port optical router for photonic networks-on-chip

We experimentally demonstrate a spatially non-blocking five-port optical router, which is based on microring resonators tuned through the thermo-optic effect. The characteristics of the microring-resonator-based switching element are investigated to achieve balanced performances in its two output ports. The optical router is fabricated on the SOI platform using standard CMOS processing. The effective footprint of the device is about 440×660 μm2. The microring resonators have 3-dB bandwidths of larger than 0.31 nm (38 GHz), and extinction ratios of better than 21 dB for through ports and 16 dB for drop ports. Finally, 12.5 Gbps high-speed signal transmission experiments verify the routing functionality of the optical router.

Ultra-low-power carrier-depletion Mach-Zehnder silicon optical modulator

We demonstrate a 26 Gbit/s Mach-Zehnder silicon optical modulator. The doping concentration and profile are optimized, and a modulation efficiency with the figure of merit (VπL) of 1.28 V·cm is achieved. We design an 80-nm-wide intrinsic silicon gap between the p-type and n-type doped regions to reduce the capacitance of the diode and prevent the diode from working in a slow diffusion mode. Therefore, the modulator can be driven with a small differential voltage of 0.5 V with no bias. Without the elimination of the dissipated power of the series resistors and the reflected power of the electrical signal, the maximum power consumption is 3.8 mW.

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.

Proof of concept of directed OR/NOR and AND/NAND logic circuit consisting of two parallel microring resonators

We propose and demonstrate a directed OR/NOR and AND/NAND logic circuit consisting of two parallel microring resonators (MRRs). We use two electrical signals representing the two operands of the logical operation to modulate the two MRRs through the thermo-optic effect, respectively. The final operation results are represented by the output optical signals. Both OR/NOR and AND/NAND operations at 10 kbps are demonstrated.

Low-voltage, high-extinction-ratio, Mach-Zehnder silicon optical modulator for CMOS-compatible integration.

We demonstrate a carrier-depletion optical modulator with the driving voltage swing of 2 V and the extinction ratio of 12.79 dB at 12.5 Gbit/s. Even the driving voltage is reduced to 1 V, the the device still has an extinction ratio of 7.67 dB.

Electro-optic directed logic circuit based on microring resonators for XOR/XNOR operations

We report the implementation of the XOR and XNOR operations using an electro-optic directed logic circuit based on two cascaded silicon microring resonators (MRRs), which are both modulated through the plasma dispersion effect. PIN diodes are embedded around the MRRs to achieve the carrier-injection modulation. The inherent resonance wavelength mismatch between the two nominally identical MRRs caused by fabrication errors is compensated by two local microheaters above each MRR through the thermo-optic effect. Two electrical modulating signals applied to the MRRs represent the two operands of the two operations. Simultaneous bitwise XOR and XNOR operations at 100 Mbit/s are demonstrated.

Simultaneous implementation of XOR and XNOR operations using a directed logic circuit based on two microring resonators

We report the simultaneous implementation of the XOR and XNOR operations at two ports of a directed logic circuit based on two cascaded microring resonators (MRRs), which are both modulated through thermo-optic effect. Two electrical modulating signals applied to the MRRs represent the two operands of each logic operation. Simultaneous bitwise XOR and XNOR operations at 10 kbit/s are demonstrated in two different operating modes. We show that such a circuit can be readily realized using the plasma dispersion effect or the electric field effects, indicating its potential for high-speed operation. We further employ the scattering matrix method to analyze the spectral characteristics of the fabricated circuit, which can be regarded as a Mach-Zehnder interferometer (MZI) in whole. The two MRRs in the circuit act as wavelength-dependent splitting and combining units of the MZI. The degradation of the spectra observed in the experiment is found to be related to the length difference between the MZIs two arms. The evolution of the spectra with this length difference is presented.

Demonstration of a directed optical decoder using two cascaded microring resonators

We propose and demonstrate a directed optical decoder that can perform the decoding function from a two-bit electrical signal to a four-bit optical signal based on two cascaded microring resonators. We use two electrical signals regarded as a two-bit electrical signal to modulate the two microring resonators through the thermo-optic effect and four optical signals regarded as a four-bit optical signal appear at the output ports, respectively. The device operating at 10 kbps is demonstrated.

Integrated reconfigurable optical add-drop multiplexers based on cascaded microring resonators

We report on an eight-channel reconfigurable optical add-drop multiplexer based on cascaded microring resonators with a high tuning power consumption and a compact footprint. Microheaters are fabricated on top of the microring resonators and can be modulated using the thermo-optic effect to achieve the reconfigurable functionality of the device. We demonstrate the reconfigurable add-drop multiplexing functionality for channel spacings of 100 GHz and 50 GHz, with the centre wavelengths of the channels aligned to International Telecommunication Union grid specifications. The crosstalk for channel spacings of 100 GHz and 50 GHz are less than −22.5 dB and −15.5 dB, respectively. The average tuning efficiency is about 4.5 mW/nm, and the response speed is about 13.0 kHz.