The University of Glasgow research team recently released its latest results in Science Advanceds, launching the world's first single-chip integrated narrow-line width laser (MOIL-TISE), with a width of only 983 Hz, refreshing the performance record of semiconductor lasers.
As data centers continue to increase demand for data width, optical communication is rapidly pushing from 800G to 1.6T or even 3.2T. In high-speed coherent light transmission, laser light sources are one of the most critical components. Optical systems are like radio stations, and lasers are "electric frequency". If the frequency is not accurate or the flow is moving, the noise is heard; if the laser is not stable, the transmission data will also be distorted. Therefore, the width of the line directly determines the clarity and stability of the signal. Then why do we need to make the narrower the width of the wire? Because the narrower the line, the cleaner the signal will be. It will not only carry more information, but also transmit it farther and have a lower error rate.
The optical communication lasers commonly seen in the industry include DFB (dispersed ejection laser) and EML (electric absorption modulation laser), which are widely used in pluggable optical modules in data centers; higher-level ECL (external cavity laser) can compress kHz width and are used for long-distance coherent optical communication, but require large external cavity. Taking NVIDIA as an example, its GPU server is connected through InfiniBand high-speed interconnect technology with CPO (co-packaged optical) modules, and it still relies on DFB/EML or external laser source (ELS) and relies on DSP (digital signal processor) to correct messages. These technologies are mature, but the disadvantage is that the module is large in size and energy consumption, which not only increases heat dissipation difficulties, but also pushes up costs.
In contrast, the MOIL-TISE single chip laser proposed by the University of Glasgow has embarked on a new path. On the InP substrate, the research team integrated the laser cavity (TISE) with a micro-ring resonator (MRR) single wafer for the first time, achieving an Hz-level ultra-narrow line width, and condensed the stable function that originally required an external module to achieve in a single wafer laser structure of only 1000 μm × 0.4 μm, which is hundreds of times more detailed than the hair. This design allows the laser line to be directly compressed from MHz to 983 Hz, which is thousands of times stable than existing DFB/EML, and its performance is even close to high-level ECL, but it has a smaller size and a simpler process.
▲ MOIL-TISE single-chip laser structure diagram: central TISE cavity, stable light field, micro-ring resonator (MRR, semi-sodium 150 μm) recovers photons and implements light injection lock. (Source: Science Advanceds)
This technology is regarded as an important breakthrough in promoting optical communication and quantum applications. In the data center field, ultra-narrow-width laser energy makes 1.6T and 3.2T Coherent Optical Modules easier to land, reduce digital signal processing (DSP) computing burden and improves frequency efficiency; in quantum communication (QKD), it can support high-speed phase switching to create an incrackable quantum encryption system.
At present, this technology is still in the experimental stage and has not yet entered mass production, but because the process is compatible with the existing semiconductor processes, it will have the potential to be commercialized in the future. If it can be implemented smoothly, it will have the opportunity to replace the existing DFB/EML and some external cavity lasers, becoming the development trend of the new generation of optical modules and quantum encryption systems.
University of Glasgow reports single-chip laser system with 983Hz linewidth