By integrating a free-standing cadmium sulfide (CdS) nanowire onto a silicon nitride (SiN) photonic chip, we demonstrate a highly compact on-chip single-mode CdS nanowire laser. The mode selection is realized using a Mach-Zehnder interferometer (MZI) structure. When the pumping intensity exceeds the lasing threshold of 4.9 kW/cm², on-chip single-mode lasing at ~518.9 nm is achieved with a linewidth of 0.1 nm and a side-mode suppression ratio of up to a factor of 20 (13 dB). The output of the nanowire laser is channelled into an on-chip SiN waveguide with high efficiency (up to 58%) by evanescent coupling, and the directional coupling ratio between the two output ports can be varied from 90 to 10% by predesigning the coupling length of the SiN waveguide. Our results open new opportunities for both nanowire photonic devices and on-chip light sources and may pave the way towards a new category of hybrid nanolasers for chip-integrated applications.

Most current Data Center Interconnects (DCI) use intensity modulation direct detection (IMDD) configurations due to their low complexity and cost. However, significant scaling challenges allow coherent solutions to become contenders in these short reach applications. We present an O-band coherent optical fiber transmission system based on Quantum Dot—Mode Locked Lasers (QD-MLLs) using two independent free-running comb lasers, one each for the carrier and the Local Oscillator (LO). Using a comb-to-comb configuration, we demonstrate a 10 km single mode fiber, O-band, coherent, heterodyne, 12.1 Tbps system operating at 0.47 Tbps/λ using 26 λs. We used fewer comb lines (26 λs), faster symbol rate (56 GBaud) and higher constellation cardinality (32 QAM) relative to the highest capacity C-band systems reported to date. Through design, analysis, and experimentation, we quantify the optimum comb line spacing for this use case. We compare potential configurations for increasing data center interconnect capacities whilst reducing power consumption, complexity, and cost.

As internet traffic demand continues to increase, high-speed electro-optic modulators and high-bandwidth RF components are needed to stretch intensity modulation direct detection (IMDD) systems to their limits. In this study, we experimentally demonstrate the transmission performance using the next generation of digital-to-analog converters (DAC) and high-bandwidth thin-film lithium niobate (TFLN) modulators. In the C-band, we transmit 172 Gbaud PAM6 and 180 Gbaud PAM8 over 120 m of SSMF under the 6.7% overhead hard-decision forward error correction (HD-FEC) and the 20% overhead soft-decision (SD)-FEC thresholds, which respectively correspond to net 400 and 450 Gbps. We also demonstrate the first transmission of net 400 Gbps over 10 km in the O-band (1310 nm) using 172 Gbaud probabilistically shaped (PS)-PAM8 under the 20% SD-FEC BER threshold. Our results indicate that the TFLN platform has the potential to support even higher data rates with the development of high-bandwidth RF components.

With the exponential growth of internet traffic, driven by the increasing number of connected devices and data-intensive applications, there is an urgent need to address the surging demand for higher capacity in datacenter communications. This paper proposes using O-band single-carrier coherent transmission to achieve 1.6 Tbps for intra-datacenter reach (2-10 km), leveraging the advancements in next-generation DACs and the TFLN platform. To support our proposal, we assess experimentally the gain of employing 256 GSa/s interleaved DACs compared to the current state-of-the-art 128 GSa/s DACs. Additionally, we explore the feasibility of utilizing cost-effective DFB lasers in these short-reach systems. Using the 128 GSa/s DAC and DFB lasers, we transmit 120 Gbaud DP-64QAM over 10 km of SSMF under the 20% overhead SD-FEC threshold, featuring a net rate of 1.2 Tbps. Switching to 256 GSa/s DAC, we achieve net 1.6 Tbps transmission over 10 km with 167 Gbaud DP-64QAM below the 25% SD-FEC BER threshold. We observe that the power penalty of using DFB lasers compared to ECLs is less than 1 dB. Furthermore, this study includes a comprehensive analysis of the power consumption envelope for various candidate configurations targeting 1.6 Tbps operation. The comparison reveals the competitiveness of the O-band single-carrier coherent solution, attributed to its simpler architecture and the inherent features of the TFLN platform. The analysis highlights the potential of the proposed solution as a power-efficient and high-performance option for meeting the demanding requirements of 1.6 Tbps Ethernet.

The escalating datacenter traffic emphasizes the need for high-performance, cost-effective, and energy-efficient optical transceivers. We demonstrate barium titanate (BTO) electro-optic Mach-Zehnder modulators (MZMs) integrated on the silicon photonic platform, surpassing all-silicon counterparts in key metrics: modulation efficiency (VπL = 4.8 Vmm), loss (∼2 dB), and static tuning power (∼100 μW), while maintaining CMOS compatibility. Employing BTO MZMs, we showcase, for the first time, short-reach intensity-modulation and direct-detection (IMDD) transmissions beyond 200 Gbps/λ. In the C-band, over 500 m of standard single-mode fiber (SSMF), we have achieved: (a) a 122 Gbaud PCS-PAM-8 (net 300 Gbps) below the 20% overhead soft-decision forward error correction (SD-FEC) BER threshold of 2.4 × 10 ^-2 , and (b) a 106 Gbaud PAM-4 (net 200 Gbps) below the 6.7% overhead hard-decision (HD) FEC threshold of 3.8 × 10 ^-3 , with a remarkably 9-fJ/bit electrical power dissipation. In the O-band, we transmit (a) a net 200 Gbps over 10-km SSMF below the 5.8% overhead KP4-FEC BER threshold across wavelengths from 1301 nm to 1321 nm, and (b) a net 250 Gbps over 2-km SSMF below the HD-FEC BER threshold ranging from 1291 nm to 1321 nm. Our research highlights BTO MZMs as potent, power-efficient solutions for next-gen transmitters beyond 200 Gbps/λ for intra- and inter-datacenter applications.