Researchers at Fudan University in Shanghai, China, have developed the world's first all-silicon laser, using silicon nanocrystals with high optical gains.
The last piece of the puzzle
“The all-silicon laser is regarded as the Holy Grail in silicon photonics,” says research leader Professor Xiang Wu, calling his team´s all-silicon laser the last piece missing from the jigsaw of silicon photonics, since other monolithic photonic devices have already been technically achieved and commercially available. “Once the last piece of the jigsaw is provided, integrated silicon photonics will be truly accomplished, leading to a new revolution in information technology, which is similar to the case of integrated circuits and electronics happening, decades ago.”
What led to the breakthrough
The bottleneck that had prevented the realization of all-silicon lasers until now is the low optical gain of silicon nanomaterials, such as nanocrystals. “In our work, we firstly developed an approach to increase the density of silicon nanocrystals in the gain layer, in order to significantly enhance the light intensity,” Wu explains. “We then applied a unique approach of high-pressure surface passivation to the gain layer. After the passivation, the boosted optical gain of silicon nanocrystals became comparable to that of commonly used III-V lasing compounds, which laid a solid foundation for the development of all-silicon lasers.”
Thus, Wu, again calling the all-silicon laser the last missing piece of the jigsaw of integrated silicon photonics, stresses that his team´s work now solves the problem of how to monolithically grow a light source or a laser on silicon substrate for integrated silicon photonics.
A new revolution in information technology
Wu agrees, the pioneering achievement could mean the awaited paradigm shift in the advancement of integrated silicon photonics: “The full realization of integrated silicon photonics can provide better performance, with substantially reduced cost, triggering a new revolution of information technology around the world.”
All-silicon laser enables new kinds of applications
The silicon-based laser Wu and his colleagues have developed is compatible with existing fabrication techniques for microelectronics �" the key to achieving true integrated silicon photonics. “Unlike the III-V compound lasers, the silicon lasers do not suffer lattice mismatch, so in theory, it has the potential of becoming a better candidate for high-power lasers,” he says, adding that, besides, the high abundance and low cost of silicon can substantially reduce the fabrication cost. The applications of silicon lasers include data communication, lighting, imaging, display, bio and chemical sensing, etc.
The biggest challenge in developing the all-silicon laser, according to the professor, was to figure out how to increase the optical gain of silicon nanocrystals to a level comparable to that of commonly used III-V lasing compounds. Device design and fabrication were critical factors as well.
An outcome beyond the experts´ expectations
Wu admits even he was surprised at the remarkable outcome of this research work. “Combined with the DFB resonance cavity, the high-gain silicon nanocrystals showed clear laser behaviors, which was beyond our expectations,” he says. “We were thrilled that we successfully developed the world's first all-silicon laser after decades of effort.”
The next step
The first all-silicon laser the researchers at the University in China made was optically pumped. Their next target, Wu says, is to make an electrically pumped all-silicon laser that is more applicable to commercialization.
The research is detailed in the article “An all-silicon laser based on silicon nanocrystals with high optical gains,” recently published in Science Bulletin.
Written by Sandra Henderson, Research Editor, Novus Light Technologies Today
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