Low Cost, Low Power, Low Latency 1602 nm 100 Gbps NRZ Laser–EAM for a 7.2 Tbps Transmitter.

The need for higher speed supercomputing power at NASA is clear, and one of the many impairments to realizing an exaflop computer is the speed and latency of the data links that connect the processors and memory. Even with the advent of higher speed standards in Ethernet and Fibre Channel, the data throughput is crippled due to the need for non-binary encoding and error correction algorithms as a direct result of the limited bandwidth of the optical components. The induced latency and power consumption are acceptable in a data center environment but severely limits high performance computing. Efforts to increase the fundamental optical component bandwidth have not been successful in increasing to the point of achieving binary NRZ data transmission without error correction at 100Gbps. Binary NRZ is the most power and latency efficient means to transmit data in a super computing environment. A revolutionary optical component is needed to break the traditional paradigm. The laser and electro-absorptive modulator (laser-EAM) in this proposal represents many significant technical advancements including: (1) fundamental bandwidth in excess of 100GHz using direct band to band absorption, (2) very low power consumption (150fJ/bit), (3) operation over the entire environmental temperature range without a thermo-electric controller, (4) monolithic integration of the laser and EAM (5) potential to integrate a vertical outcoupler. The innovations that lead to these technical achievements are the design of a common active region for both the laser and EAM, and the use of enhanced coupling strength (ECS) gratings to provide wideband mirrors. This combination allows the laser emission to tune freely with temperature and the EAM absorption to track the laser. Further, the laser-EAM is realized in a single epitaxial growth, and the fabrication is completely monolithic. This provides a highly manufacturable and cost-effective solution to the optical component bandwidth problem. There is a significant limit in NASA computing at the HEC, and there is a clear need to upgrade the system capability and capacity as reported by the NASA High-End Computing Capability Project and The National Strategic Computing Initiative. A fundamental limit to supercomputing capability is data connectivity and latency. The proposed laser and electro-absorption modulator (Laser-EAM) enables 100Gbps data connectivity in traditional NRZ formats without error correction, thereby minimizing data latency. Further, the Laser-EAM operates over the data center environment without the need for temperature control, further reducing the power required to under 150fJ/bit. An Exaflop computer is expected in the near future, and it will require 1M data links running at 100Gbps to operate. The Laser-EAM provides fundamental technical advancement in the bandwidth and power consumption of optical data links. By arranging the Laser-EAMs in parallel, more than 1Tbps can be achieved on a single fiber optic cable which addresses another fundamental concern of supercomputing, cable management. The primary objective is to deliver Laser-EAMs capable of 100Gbps NRZ modulation to NASA and to optical transceiver manufacturers to incorporate into product. The major milestones in the device development include the final design of the Laser-EAM using a single epitaxial growth and homogeneous integration of the Enhanced Coupling Strength Gratings (ECSG). These two features differentiate the Laser-EAM from all other current technologies which require both multi-stage epitaxial growth to define the laser and modulator, or the heterogeneous integration of the laser and modulator (e.g. Silicon Photonics). The transfer of the Laser-EAM to a fully capable epitaxial and fabrication foundries identified in phase I is a major deliverable in this proposal. Through multiple design, growth and fabrication iterations the key manufacturing processes and tolerances will be mapped. To deliver optical transceivers requires a full ecosystem, and another objective is to work with integrates circuit makers to develop the appropriate Laser-EAM drivers.
Benefits: The primary application of the laser-EAM will be in connectivity of processors and memory banks in a high-performance computing environment. Modern computing is limited by the data latency of the links between the computing elements, and currently available high-speed optical components use non-binary data encoding and error correction algorithms to achieve the data bandwidth. The proposed laser-EAM resolves the optical component bandwidth limitation and will enable higher speed and lower power consumption in the data connections. The global network traffic continues to grow exponentially, and optical communications standards such as Ethernet and Fiber Channel need a clear path to 100Gbps serial data connectivity to support the demand. Current solutions are power inefficient and have high data latency. To enable an exaflop computer, which is expected in 2022, more than 1M links operating at 100Gbps are needed.