Scientists demonstrate the world's first germanium laser

Researchers at MIT (Massachusetts Institute of Technology) have demonstrated the first laser built from germanium, the first works at room temperature that can produce wavelengths of light useful for optical communication.

Traditionally used lasers are made from gallium arsenide and other expensive materials that have to be attached to computing chips after each component has been separately manufactured. Unlike the materials typically used in lasers, germanium is easy to incorporate into existing processes for manufacturing silicon chips.

The result could be useful for high-speed optical data pathways within computers - so the scientists hope to apply this new technology to the world of processors and begin moving data and (maybe) performing calculations using light instead of electricity.

But more fundamentally, the researchers have shown that, contrary to prior belief; a class of materials called indirect-band-gap semiconductors can yield practical lasers.

As chips' computational capacity increases, they need higher-bandwidth connections to send data to memory.

But, conventional electrical connections will soon become impractical, because they'll require too much power to transport data at ever higher rates.

Transmitting data with lasers - devices that concentrate light into a narrow, powerful beam - could be much more power-efficient, but it requires a cheap way to integrate optical and electronic components on silicon chips.

Chip assembly is a painstaking process in which layers of different materials are deposited on a wafer of silicon, and patterns are etched into them.

Inserting a new material into this process is difficult: it has to be able to chemically bond to the layers above and below it, and depositing it must be possible at the temperatures and in the chemical environments suitable to the other materials.

The materials used in today's lasers, such as gallium arsenide, are "all tough fits," according to Tremont Miao, a marketing director at Massachusetts-based Analog Devices Semiconductor.

Integrating germanium into the manufacturing process, however, is something that almost all major chip manufacturers have already begun to do, since the addition of germanium increases the speed of silicon chips.

"The ability to grow germanium on silicon is a discovery of this group and the ability to control the strain of those germanium films on silicon is a discovery of this group," said Lionel Kimerling, the Thomas Lord Professor of Materials Science and Engineering, who leads the group.

"High-speed optical circuits like germanium in general. That's a good marriage and a good combination. So their laser research is very, very promising," said Miao.

Miao points out that the germanium lasers need to become more power-efficient before they're a practical source of light for optical communications systems.

MIT's primary germanium laser investigator was Jurgen Michel. Jifeng Liu was lead author of the paper, and Lionel Kimerling, Xiaochen Sun, and Rodolfo Camacho-Aguilera are coauthors.

Via - Cnet , DailyTech , Physorg

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