Intel Fires Up Silicon Laser
It's the most promising development yet from Intel's silicon photonics research, because the results are made to be mass-producible and cheap enough to use for chip-to-chip interconnect inside servers and even PCs. (See Intel Debuts Laser.)
"Someday" is still a ways off, though. "You'll hopefully see this technology in the early part of the next decade," said Mario Paniccia, director of Intel's Photonics Technology Lab, during a news conference this morning.
Intel developed the laser with Intel-funded help from the Optoelectronics Technology Center of the University of California at Santa Barbara , an institution housing some noteworthy optics research. UCSB professor and Calient Technologies Inc. founder John Bowers had a hand in the research and spoke at the news conference as well.
The results are being presented today at the Institute of Electrical and Electronics Engineers Inc. (IEEE) International Semiconductor Laser Conference in Hawaii. (Tough life for Bowers, going between Santa Barbara and Hawaii.)
Intel's goal is to produce optical components in silicon using complementary metal-oxide semiconductor (CMOS) processes -- the manufacturing processes that build the majority of the world's chips. CMOS optics would likely be cheaper than those made from materials such as indium phosphide (InP) and could eliminate the laser-alignment steps that add cost to some optical components.
The obsession with optical comes from the increased speeds that telecom and computing equipment will experience in years to come. Copper lines aren't likely to keep up with those speeds, but optics so far have been too expensive to consider using in PCs and servers.
Silicon photonics research is going on at universities worldwide and at a few startups, such as Luxtera Inc. , although Luxtera isn't working on CMOS lasers. (See Luxtera Launches Silicon Optics.)
Silicon can't generate light on its own -- not in any mass-producible way that works under normal conditions, anyway -- so Intel and UCSB use InP to get their laser started.
The InP portion generates the initial light. The silicon portion bounces the light back and forth in a waveguide that acts as a laser cavity. From there, the process is a lot like a normal laser: The light bounces back and forth in the cavity and eventually gets spat out as a laser beam.
This is not the same thing as using an InP laser to start the process, which of course would be cheating. The silicon portion contributes 97 percent of the light energy generated, Paniccia said, and it's the silicon that determines the laser's performance and could determine its wavelength as well.
Researchers have gotten the lasers to produce light of 1.8 milliwatts -- good enough for chip-to-chip optical interconnects -- from an input power of 65 milliamps; the plan is to get that threshold current down to about 20 mA. The lasers can operate at 40 degrees Celsius, and the researchers expect to push that to 70 degrees with the next round of devices.
"These are not record results. These are typical results we are getting out of these devices today," Bowers said.
The breakthrough here is that the chip is electrically pumped. Intel announced silicon lasers last year, but those had to be optically pumped -- that is, they had to sit aside a normal, non-silicon laser. Intel called the result a scientific breakthrough, but it didn't lend itself to mass production. (See Intel Claims Laser Breakthrough.)
Getting the electrically pumped chip to work was just part of the problem. Intel also wanted to bond the InP and silicon pieces in a way that could be done for hundreds of devices at a time (bonding them one laser at a time would be easy but wouldn't jibe with server/PC economics). That involved developing new techniques at UCSB, using "layers about 25 atoms thick" on the silicon and InP devices to bond them together, Bowers said.
(For chip geeks: That bonding is done at a wafer scale, meaning they slap the big wafers of CMOS and InP together before cutting them up into chips. One key to UCSB's bonding method is that it's based on tools similar to those in use today.)
Intel is being vague about applications for the hybrid optical chip, but it seems likely the technology will be aimed at servers and supercomputers. Paniccia and Bowers mentioned telecom possibilities several times during the news conference, however, and the hybrid device operates in the 1550nm wavelength range, which adheres to telecom standards. Fiber-to-the-home could be one area that finds the device useful, Paniccia said.
The device could be applied to optical amplifiers as well, and might have a role to play in biotech, he added.
Intel's other silicon photonics research is continuing, of course. The optically pumped laser announced last year is still in development and could have applications in areas like amplifiers, Paniccia said. Other pieces of the optical networking chain are making progress, too. Paniccia noted that Intel has gotten silicon-germanium photodetectors to work; they would be the on-chip counterparts to the silicon lasers. Separately, he said the company is "still aggressively pursuing" the silicon modulator announced two years ago. (See Intel's Modest Modulator .)
— Craig Matsumoto, Senior Editor, Light Reading