Racetrack Design Improves Hybrid Silicon Laser
Intel and UCSB have made major improvements to the hybrid AlGaInAs-silicon laser platform that was unveiled to the world last year.
The latest design features a "racetrack" shaped laser cavity that is entirely defined by silicon processing and now also includes on-chip photodetectors (Optics Express 15 2315).
The goal is to come up with an affordable toolkit that gives chip makers the fundamental building blocks needed to create high-speed photonic integrated circuits.
By using a monolithic strategy, the group hopes to move away from a dependence on the traditional wafer dicing and facet polishing approach.
"We wanted to show that our hybrid silicon waveguide can be used as an integration platform," explained Alexander Fang of UCSB s department of electrical and computer engineering. "By placing photodetectors on the output of the laser, we can test the chip without the cost of additional fabrication steps."
As well as tackling manufacturing issues, the team has been busy improving device performance. "Last year, the laser had a maximum operating temperature of 40°C and now it works at up to 65°C," revealed Fang. "The hope is to have silicon lasers that operate at 85°C and beyond to reduce the amount of power that is required for thermoelectric cooling."
To make the device, the UCSB team bonded an AlGaInAs quantum well structure to a low-loss silicon rib waveguide. The electrically-pumped evanescent laser emits up to 29 mW of optical power at a wavelength of 1590 nm.
Fang and his colleagues have also demonstrated a discrete amplifier based on the same waveguide structure, representing another step towards building practical transmitters and receivers on silicon (IEEE Photonics Technology Letters 19 230).
Critics of the hybrid laser approach may have concerns about the scalability of the group s wafer-bonding technique, but Fang remains upbeat: "We re in the process of studying the effects of moving to larger bonding areas on bonding quality and device performance," he commented. "From a device perspective, it could be feasible to see our technology in applications like board-to-board interconnects in five years or so."
James Tyrrell is News Editor of Optics & Laser Europe magazine and a contributor to optics.org.