Optical vortex beams carrying orbital angular momentum (OAM) have received great attention since the 1990s. In particular, OAM offers an additional degree of freedom, thus, enabling boosting of data transmission capacity in communication systems. One of the major challenges of OAM-based communication lies in multiplexing OAM via a kind of effective, compact, and flexible approach. Here, a novel approach to achieve the generation and combination of OAM beams by a pre-engineered reflective metasurface chip is demonstrated. Compared to traditional methods of OAM generation, this approach shows superiorities of broadband operating wavelength, high mode purity, flexible design, and compact size. Moreover, a free-space OAM multiplexing communication experiment based on the single metasurface is successfully carried out, performing 448 Gbit s −1 data transmission with four different topological charges of OAM and two polarizations by 28-GBaud QPSK signals. This work experimentally demonstrates promising applications of the metasurface in high-capacity optical communication systems.
Thin-film lithium-niobate-on-insulator (LNOI) is a very attractive
platform for optical interconnect and nonlinear optics. It is
essential to enable lithium niobate photonic integrated circuits with
low power consumption. Here we present an edge-coupling Mach–Zehnder
modulator on the platform with low fiber-chip coupling loss of
0.5 dB/facet, half-wave voltage
V
π
of 2.36 V, electro-optic (EO)
bandwidth of 60 GHz and an efficient thermal-optic phase shifter with
half-wave power of 6.24 mW. In addition, we experimentally demonstrate
single-lane 200 Gbit/s data transmission utilizing a discrete
multi-tone signal. The LNOI modulator demonstrated here shows great
potential in energy-efficient large-capacity optical
interconnects.
High-speed polarization management is highly desirable for many applications, such as remote sensing, telecommunication, and medical diagnosis. However, most of the approaches for polarization management rely on bulky optical components that are slow to respond, cumbersome to use, and sometimes with high drive voltages. Here, we overcome these limitations by harnessing photonic integrated circuits based on thin-film lithium niobate platform. We successfully realize a portfolio of thin-film lithium niobate devices for essential polarization management functionalities, including arbitrary polarization generation, fast polarization measurement, polarization scrambling, and automatic polarization control. The present devices feature ultra-fast control speeds, low drive voltages, low optical losses and compact footprints. Using these devices, we achieve high fidelity polarization generation with a polarization extinction ratio up to 41.9 dB and fast polarization scrambling with a scrambling rate up to 65 Mrad s−1, both of which are best results in integrated optics. We also demonstrate the endless polarization state tracking operation in our devices. The demonstrated devices unlock a drastically new level of performance and scales in polarization management devices, leading to a paradigm shift in polarization management.
Photonic integrated devices that emit vortex beam carrying orbital angular momentum are becoming key components for multiple applications. Here we propose and demonstrate a high-efficiency vortex beam emitter based on a silicon micro-ring resonator integrated with a metal mirror. Such a compact emitter is capable of generating vortex beams with a high efficiency and small divergence angle. Vector vortex beams of various topological charges are selectively generated by the emitter at different wavelengths with an emission efficiency of up to 37%.
8-OAM modes each carrying 10 wavelengths with 2.56-Tbit/s aggregated capacity and 10.24-bit/s/Hz spectral efficiency have been transmitted over 50-km specially designed ring-core fiber, using a compact OAM mode sorter and only modular 4×4 MIMO equalization.
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