Photonic radio frequency channelizers based on Kerr optical micro-combs

We review recent work on broadband RF channelizers based on integrated optical frequency Kerr micro-combs combined with passive micro-ring resonator filters,with microcombs having channel spacings of 200 and 49 GHz.This approach to realizing RF channelizers offers reduced complexity,size,and potential cost for a wide range of applications to microwave signal detection.

Orthogonally polarized RF optical single sideband generation with integrated ring resonators

We review recent work on narrowband orthogonally polarized optical RF single sideband generators as well as dualchannel equalization,both based on high-Q integrated ring resonators.The devices operate in the optical telecommunications C-band and enable RF operation over a range of either fixed or thermally tuneable frequencies.They operate via TE/TM mode birefringence in the resonator.We achieve a very large dynamic tuning range of over 55 dB for both the optical carrier-to-sideband ratio and the dual-channel RF equalization for both the fixed and tunable devices.

Non-blocking 2×2 switching unit based on nested silicon microring resonators with high extinction ratios and low crosstalks

In this paper,we propose and demonstrate a2 9 2 optical Benes switching unit based on two nested silicon microring resonators(MRRs)monolithically integrated on a silicon-on-insulator(SOI)wafer.High extinction ratios(ERs)of about 44.7/38.0 dB and low crosstalk values of about-37.5/-45.2 dB at cross/bar states are obtained with the fabricated device.The operation principle is theoretically studied and the switching function is verified by system demonstration experiments with 10 and12.5 Gb/s non-return-to-zero(NRZ)signals.The switching speed on the order of gigahertz based on free carrier effect in silicon is also experimentally demonstrated.

Photonic microwave true time delays for phased array antennas using a 49 GHz FSR integrated optical micro-comb source[Invited]

We demonstrate significantly improved performance of a microwave true time delay line based on an integrated optical frequency comb source. The broadband micro-comb(over 100 nm wide) features a record low free spectral range(FSR) of 49 GHz, resulting in an unprecedented record high channel number(81 over the C band)—the highest number of channels for an integrated comb source used for microwave signal processing. We theoretically analyze the performance of a phased array antenna and show that this large channel count results in a high angular resolution and wide beam-steering tunable range. This demonstrates the feasibility of our approach as a competitive solution toward implementing integrated photonic true time delays in radar and communications systems.

Compact on-chip 1×2 wavelength selective switch based on silicon microring resonator with nested pairs of subrings

We propose and experimentally demonstrate compact on-chip 1×2 wavelength selective switches(WSSs) based on silicon microring resonators(MRRs) with nested pairs of subrings(NPSs). Owing to the resonance splitting induced by the inner NPSs, the proposed devices are capable of performing selective channel routing at certain resonance wavelengths of the outer MRRs. System demonstration of dynamic channel routing using fabricated devices with one and two NPSs is carried out for 10 Gb∕s non-return-to-zero signal. The experimental results verify the effectiveness of the fabricated devices as compact on-chip WSSs.

Compact all-optical differential-equation solver based on silicon microring resonator

We propose and numerically demonstrate an ultrafast real-time ordinary differential equation （ODE） computing unit in optical field based on a silicon microring resonator, operating in the critical coupling region as an optical temporal differentiator. As basic building blocks of a signal processing system, a subtractor and a splitter are included in the proposed structure. This scheme is featured with high speed, compact size and integration on a siliconon-insulator （SOl） wafer. The size of this computing unit is only 35 μm × 45 μm. In this paper, the performance of the proposed structure is theoretically studied and analyzed by numerical simulations.

Improving the Stability of theMultiple-Relaxation-Time Lattice Boltzmann Method by a Viscosity Counteracting Approach

Numerical instability may occur when simulating high Reynolds number flows by the lattice Boltzmann method(LBM).The multiple-relaxation-time(MRT)model of the LBM can improve the accuracy and stability,but is still subject to numerical instability when simulating flows with large single-grid Reynolds number(Reynolds number/grid number).The viscosity counteracting approach proposed recently is a method of enhancing the stability of the LBM.However,its effectiveness was only verified in the single-relaxation-time model of the LBM(SRT-LBM).This paper aims to propose the viscosity counteracting approach for the multiple-relaxationtime model(MRT-LBM)and analyze its numerical characteristics.The verification is conducted by simulating some benchmark cases:the two-dimensional(2D)lid-driven cavity flow,Poiseuille flow,Taylor-Green vortex flow and Couette flow,and threedimensional(3D)rectangular jet.Qualitative and Quantitative comparisons show that the viscosity counteracting approach for the MRT-LBMhas better accuracy and stability than that for the SRT-LBM.

Integrated optical parametric amplifiers in silicon nitride waveguides incorporated with 2D graphene oxide films

Optical parametric amplification(OPA)represents a powerful solution to achieve broadband amplification in wavelength ranges beyond the scope of conventional gain media,for generating high-power optical pulses,optical microcombs,entangled photon pairs and a wide range of other applications.Here,we demonstrate optical parametric amplifiers based on silicon nitride(Si3N4)waveguides integrated with two-dimensional(2D)layered graphene oxide(GO)films.We achieve precise control over the thickness,length,and position of the GO films using a transfer-free,layer-by-layer coating method combined with accurate window opening in the chip cladding using photolithography.Detailed OPA measurements with a pulsed pump for the fabricated devices with different GO film thicknesses and lengths show a maximum parametric gain of~24.0 dB,representing a~12.2 dB improvement relative to the device without GO.We perform a theoretical analysis of the device performance,achieving good agreement with experiment and showing that there is substantial room for further improvement.This work represents the first demonstration of integrating 2D materials on chips to enhance the OPA performance,providing a new way of achieving high performance photonic integrated OPA by incorporating 2D materials.