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Due to its absorption properties in atmosphere, the mid-infrared (mid-IR) region has gained interest for its potential to provide high data capacity in free-space optical (FSO) communications. Here, we experimentally demonstrate wavelength-division-multiplexing (WDM) and mode-division-multiplexing (MDM) in a ~0.5 m mid-IR FSO link. We multiplex three ~3.4 μm wavelengths (3.396 μm, 3.397 μm, and 3.398 μm) on a single polarization, with each wavelength carrying two orbital-angular-momentum (OAM) beams. As each beam carries 50-Gbit/s quadrature-phase-shift-keying data, a total capacity of 300 Gbit/s is achieved. The WDM channels are generated and detected in the near-IR (C-band). They are converted to mid-IR and converted back to C-band through the difference frequency generation nonlinear processes. We estimate that the system penalties at a bit error rate near the forward error correction threshold include the following: (i) the wavelength conversions induce ~2 dB optical signal-to-noise ratio (OSNR) penalty, (ii) WDM induces ~1 dB OSNR penalty, and (iii) MDM induces ~0.5 dB OSNR penalty. These results show the potential of using multiplexing to achieve a ~30X increase in data capacity for a mid-IR FSO link. A 300-Gbit/s free-space optical communication system is demonstrated in the mid-IR wavelength region by using both wavelength- and mode-division multiplexing.

Ruthenium (Ru) complexes are developed as latent emissive photosensitizers for cancer and pathogen photodiagnosis and therapy. Nevertheless, most existing Ru complexes are limited as photosensitizers in terms of short excitation and emission wavelengths. Herein, we present an emissive Ru(II) metallacycle (herein referred to as 1) that is excited by 808-nm laser and emits at a wavelength of ∼1,000 nm via coordinationdriven self-assembly. Metallacycle 1 exhibits good optical penetration (∼7 mm) and satisfactory reactive oxygen species production properties. Furthermore, 1 shows broadspectrum antibacterial activity (including against drug-resistant Escherichia coli) as well as low cytotoxicity to normal mammalian cells. In vivo studies reveal that 1 is employed in precise, second near-infrared biomedical window fluorescent imaging–guided, photo-triggered treatments in Staphylococcus aureus–infected mice models, with negligible side effects. This work thus broads the applications of supramolecular photosensitizers through the strategy of lengthening their wavelengths.

The growth of computing needs for artificial intelligence and machine learning is critically challenging data communications in today’s data-centre systems. Data movement, dominated by energy costs and limited ‘chip-escape’ bandwidth densities, is perhaps the singular factor determining the scalability of future systems. Using light to send information between compute nodes in such systems can dramatically increase the available bandwidth while simultaneously decreasing energy consumption. Through wavelength-division multiplexing with chip-based microresonator Kerr frequency combs, independent information channels can be encoded onto many distinct colours of light in the same optical fibre for massively parallel data transmission with low energy. Although previous high-bandwidth demonstrations have relied on benchtop equipment for filtering and modulating Kerr comb wavelength channels, data-centre interconnects require a compact on-chip form factor for these operations. Here we demonstrate a massively scalable chip-based silicon photonic data link using a Kerr comb source enabled by a new link architecture and experimentally show aggregate single-fibre data transmission of 512 Gb s−1 across 32 independent wavelength channels. The demonstrated architecture is fundamentally scalable to hundreds of wavelength channels, enabling massively parallel terabit-scale optical interconnects for future green hyperscale data centres.Researchers design and demonstrate a scalable yet compact chip-based link architecture that may enable terabit-scale optical interconnects for hyperscale data centres.

The use of optical interconnects has burgeoned as a promising technology that can address the limits of data transfer for future high-performance silicon chips. Recent pushes to enhance optical communication have focused on developing wavelength-division multiplexing technology, and new dimensions of data transfer will be paramount to fulfill the ever-growing need for speed. Here we demonstrate an integrated multi-dimensional communication scheme that combines wavelength- and mode- multiplexing on a silicon photonic circuit. Using foundry-compatible photonic inverse design and spectrally flattened microcombs, we demonstrate a 1.12-Tb/s natively error-free data transmission throughout a silicon nanophotonic waveguide. Furthermore, we implement inverse-designed surface-normal couplers to enable multimode optical transmission between separate silicon chips throughout a multimode-matched fibre. All the inverse-designed devices comply with the process design rules for standard silicon photonic foundries. Our approach is inherently scalable to a multiplicative enhancement over the state of the art silicon photonic transmitters. The authors demonstrate a multi-dimensional communication scheme that combines wavelength- and mode- multiplexing on photonic integrated circuits using foundry-compatible photonic inverse design and spectrally flattened microcombs

The first tunable fibre ring laser in the 1700 nm wavelength region has been developed. To achieve this fibre laser, a Tm3+–Tb3+-doped fibre is used as the active fibre, along with a tunable bandpass filter. A fibre ring laser that consisted of a 1.2/1.7 μm band wavelength division multiplexing coupler, a tunable bandpass filter, an active fibre and one 1.21 μm pump laser diode has been realised. A wide tuning wavelength band of 130.4 nm (from 1635.6 to 1766.0 nm) was achieved with a launched pump power of over ∼ 30 mW. The lasing threshold pump power at 1716 nm was ∼ 9 mW.

Data rates in optical fiber networks have increased exponentially over the past decades and core-networks are expected to operate in the peta-bit-per-second regime by 2030. As current single-mode fiber-based transmission systems are reaching their capacity limits, space-division multiplexing has been investigated as a means to increase the per-fiber capacity. Of all space-division multiplexing fibers proposed to date, multi-mode fibers have the highest spatial channel density, as signals traveling in orthogonal fiber modes share the same fiber-core. By combining a high mode-count multi-mode fiber with wideband wavelength-division multiplexing, we report a peta-bit-per-second class transmission demonstration in multi-mode fibers. This was enabled by combining three key technologies: a wideband optical comb-based transmitter to generate highly spectral efficient 64-quadrature-amplitude modulated signals between 1528 nm and 1610 nm wavelength, a broadband mode-multiplexer, based on multi-plane light conversion, and a 15-mode multi-mode fiber with optimized transmission characteristics for wideband operation. Space division multiplexing solutions are one way to increase future fiber information capacity. Here, the authors show peta-bit/s transmission in a standard-diameter, multimode fiber enabled by combining several practical multiplexing technologies.

Optical interconnects have been recognized as the most promising solution to accelerate data transmission in the artificial intelligence era. Benefiting from their cost-effectiveness, compact dimensions, and wavelength multiplexing capability, silicon microring resonator modulators emerge as a compelling and scalable means for optical modulation. However, the inherent trade-off between bandwidth and modulation efficiency hinders the device performance. Here we demonstrate a dense wavelength division multiplexing microring modulator array on a silicon chip with a full data rate of 1 Tb/s. By harnessing the two individual p-n junctions with an optimized Z-shape doping profile, the inherent trade-off of silicon depletion-mode modulators is greatly mitigated, allowing for higher-speed modulation with energy consumption of sub-ten fJ/bit. This state-of-the-art demonstration shows that all-silicon modulators can practically enable future 200 Gb/s/lane optical interconnects. The authors showcase a five-channel silicon microring modulator array with a total data rate in the terabit range. Each microring is equipped with two separate Z-shape junctions to overcome the bandwidth and modulation efficiency trade-off, providing a pathway for future 200 Gb/s/lane silicon optical interconnects.