Mode-division multiplexing (MDM) technology enables high-bandwidth data transmission using orthogonal waveguide modes to construct parallel data streams. However, few demonstrations have been realized for generating and supporting high-order modes, mainly due to the intrinsic large material group-velocity dispersion (GVD), which make it challenging to selectively couple different-order spatial modes. We show the feasibility of on-chip GVD engineering by introducing a gradient-index metamaterial structure, which enables a robust and fully scalable MDM process. We demonstrate a record-high-order MDM device that supports TE0–TE15 modes simultaneously. 40-GBaud 16-ary quadrature amplitude modulation signals encoded on 16 mode channels contribute to a 2.162 Tbit / s net data rate, which is the highest data rate ever reported for an on-chip single-wavelength transmission. Our method can effectively expand the number of channels provided by MDM technology and promote the emerging research fields with great demand for parallelism, such as high-capacity optical interconnects, high-dimensional quantum communications, and large-scale neural networks.integrated photonics metamaterial mode-division multiplexing subwavelength grating
2023, 5(5): 056008
Virtual reality (VR) and augmented reality (AR) have found widespread applications in education, engineering, healthcare, and entertainment. However, these near-eye displays are often bulky and heavy, and thus are not suitable for long-term wearing. Metalenses, with an ultra-thin formfactor, subwavelength modulation scale, and high modulation flexibility, are promising candidates to replace the conventional optics in AR display systems. In this work, we proposed and fabricated a novel reflective dielectric metalens-visor based on Pancharatnam-Berry phase with see-through capability. It achieves diffraction-limited focusing behavior for the reflected red light, while keeping a good transmission spectrum in the visible region. Hence, this single piece metalens-visor can perform the function of two integrated elements simultaneously: an eyepiece and an optical combiner, which in turn greatly reduces the weight and the size of an AR display. We have implemented a proof-of-concept AR display system employing the metalens-visor, and experimentally demonstrated color AR images with good image quality. This work reveals the great potential of multi-functional metasurface devices which enables optical integration in interdisciplinary applications including wearable displays, biological imaging, and aeronautic optical instruments.
On-chip optical communications are growingly aiming at multimode operation together with mode-division multiplexing to further increase the transmission capacity. Optical switches, which are capable of optical signals switching at the nodes, play a key role in optical networks. We demonstrate a 2 × 2 electro-optic Mach–Zehnder interferometer-based mode- and polarization-selective switch fabricated by standard complementary metal–oxide–semiconductor process. An electro optic tuner based on a PN-doped junction in one of the Mach–Zehnder interferometer arms enables dynamic switching in 11 ns. For all the channels, the overall insertion losses and inter-modal crosstalk values are below 9.03 and –15.86 dB at 1550 nm, respectively.
Journal of Semiconductors
2022, 43(2): 022301
With the rapid development of artificial intelligence and machine learning, brain-inspired neuromorphic photonics has emerged as an extremely attractive computing paradigm, promising orders-of-magnitude higher computing speed and energy efficiency compared to its electronic counterparts. Tremendous efforts have been devoted to photonic hardware implementations of mimicking the nonlinear neuron-like spiking response and the linear synapse-like weighting functionality. Here, we systematically characterize the spiking dynamics of a passive silicon microring neuron. The research of self-pulsation and excitability reveals that the silicon microring can function as an all-optical class II resonate-and-fire neuron. The typical refractory period has been successfully suppressed by configuring the pump power above the perturbation power, hence allowing the microring neuron to operate with a speed up to roughly sub-gigahertz. Additionally, temporal integration and controllable inhibition regimes are experimentally demonstrated for the first time, to the best of our knowledge. Our experimental verification is obtained with a commercial CMOS platform, hence offering great potential for large-scale neuromorphic photonics integration.
2022, 10(4): 04000939
Due to the indirect bandgap nature, the widely used silicon CMOS is very inefficient at light emitting. The integration of silicon lasers is deemed as the ‘Mount Everest’ for the full take-up of Si photonics. The major challenge has been the materials dissimilarity caused impaired device performance. We present a brief overview of the recent advances of integrated III–V laser on Si. We will then focus on the heterogeneous direct/adhesive bonding enabling methods and associated light coupling structures. A selected review of recent representative novel heterogeneously integrated Si lasers for emerging applications like spectroscopy, sensing, metrology and microwave photonics will be presented, including DFB laser array, ultra-dense comb lasers and nanolasers. Finally, the challenges and opportunities of heterogeneous integration approach are discussed.
Journal of Semiconductors
2019, 40(10): 101304
We propose and experimentally demonstrate an integrated silicon photonic scheme to generate multi-channel millimeter-wave (MMW) signals for 5G multi-user applications. The fabricated silicon photonic chip has a footprint of 1.1 × 2.1 mm2 and integrates 7 independent channels each having on-chip polarization control and heterodyne mixing functions. 7 channels of 4-Gb/s QPSK baseband signals are delivered via a 2-km multi-core fiber (MCF) and coupled into the chip with a local oscillator (LO) light. The polarization state of each signal light is automatically adjusted and aligned with that of the LO light, and then 7 channels of 28-GHz MMW carrying 4-Gb/s QPSK signals are generated by optical heterodyne beating. Automated polarization-control function of each channel is also demonstrated with ~7-ms tuning time and ~27-dB extinction ratio.
Journal of Semiconductors
2019, 40(5): 052301
We experimentally demonstrate high-efficiency and broadband four-wave mixing in a silicon-graphene strip waveguide. A four-wave mixing conversion efficiency of and a 3-dB conversion bandwidth of 35 nm are achieved in the silicon-graphene strip waveguide with an optimized light-graphene interaction length of 60 μm. The interaction length is controlled by a windowed area of silica layer on the silicon waveguide. Numerical simulations and experimental studies are carried out and show a nonlinear parameter as large as .Integrated optics devices Nonlinear optics, four-wave mixing Nonlinear optical materials
2018, 6(10): 10000965