THz-to-Optical Conversion in Wireless Communications Using an Ultra-Broadband Plasmonic Modulator (1812.04121v1)

Abstract: Future wireless communication networks have to handle data rates of tens or even hundreds of Gbit/s per link, requiring carrier frequencies in the unallocated terahertz (THz) spectrum. In this context, seamless integration of THz links into existing fiber-optic infrastructures is of great importance to complement the inherent portability and flexibility advantages of wireless networks by the reliable and virtually unlimited capacity of optical transmission systems. On the technological level, this requires novel device and signal processing concepts for direct conversion of data streams between the THz and the optical domains. Here, we report on the first demonstration of a THz link that is seamlessly integrated into a fiber-optic network using direct terahertz-to-optical (T/O) conversion at the wireless receiver. We exploit an ultra-broadband silicon-plasmonic modulator having a 3 dB bandwidth in excess of 0.36 THz for T/O conversion of a 50 Gbit/s data stream that is transmitted on a 0.2885 THz carrier over a 16 m-long wireless link. Optical-to-terahertz (O/T) conversion at the wireless transmitter relies on photomixing in a uni-travelling-carrier photodiode.

THz-to-Optical Conversion in Wireless Communications Using an Ultra-Broadband Plasmonic Modulator

This paper presents an advanced approach to solving unique challenges associated with integrating terahertz (THz) wireless communication links into existing fiber-optic networks by deploying an ultra-broadband plasmonic modulator for direct THz-to-optical (T/O) conversion. While previous efforts have demonstrated optical-to-THz (O/T) conversion at the transmitter end, this paper marks a significant step forward by implementing direct T/O conversion at the receiver end, thus enabling seamless integration into photonic systems without intermediary down-conversion.

The experiment demonstrates the viability of this method by achieving data transmission rates of 50 Gbit/s over a distance of 16 meters under a carrier frequency of 0.2885 THz. This is facilitated by a plasmonic-organic hybrid (POH) modulator that features a remarkable 3 dB bandwidth exceeding 0.36 THz. Detailed experimental setups reveal that the modulator’s compact footprint and efficient THz-to-optical signal modulation provide robust functionality suitable for high-density photonic integration.

Several strong numerical results are discernible from the paper: the POH plasmonic modulator maintains a flat frequency response up to at least 0.36 THz, indicating no discernible limitations within the tested bandwidth. Furthermore, bit error ratios (BERs) for QPSK signals maintain acceptable performance levels under forward error correction thresholds, even as data rates peak at 50 Gbit/s. These outcomes confirm the modulators' capability to significantly enhance THz-to-optical conversion, outstripping current lithium niobate modulators constrained by bandwidth and device size.

Theoretical implications of this work emphasize the potential to advance THz communication systems by co-integrating ultra-broadband modulators with silicon photonic platforms. The ability to perform direct conversion significantly reduces complexity at the antenna site, encouraging scalability to numerous geographically distributed THz links and cellular networks. Such integration can lead to improvements in data traffic management, providing relief to capacity bottlenecks in wireless communication infrastructures.

Practically, the findings suggest potential for substantial developments in the area of wireless network architectures. As demand for high-speed data continues to soar, especially beyond terahertz frequencies, these modulators might play crucial roles in facilitating efficient data exchange between wireless and optical systems without expansive infrastructure overhauls.

Looking forward, developments in AI combined with advanced material science may further enhance the efficiency and performance of plasmonic modulators. Future implementations could result in lower costs and energy consumption alongside significant performance boosts, providing a pathway towards integrating the upcoming generation of wireless technology with extant optical systems globally. Such advancements will facilitate wide-ranging applications—from high-density urban environments to remote connections, drastically evolving traditional communication paradigms.

In conclusion, the direct T/O conversion approach proposed in this paper offers a promising advancement in seamlessly bridging THz and optical communication domains, unlocking new opportunities for high-performance data transmission and network flexibility, ushering enhanced scalability and resilience into future communication infrastructures.