Technical Insight
AOI gains funds for 1550nm VCSELs (Fiber News)
Applied Optoelectronics Inc (AOI), a company that manufactures mid-infrared quantum cascade lasers, has raised $10 million in a second round of funding and introduced its first VCSEL products, which operate at 1550 nm. This places AOI among the few companies, including Bandwidth9 and Nortel s CoreTek division, which are commercializing devices at this wavelength. AOI s new single-mode VCSELs are based on an external cavity laser design, and target metro applications. According to the company, a planned expansion of its development activities and production capacity, primarily for packaging and testing, will help to meet demand for these devices, which it began shipping in prototype quantities last November. AOI received $7 million in first-round funding last year, and operates a vertically integrated 24 000 sq. ft manufacturing facility in Sugar Land, Texas (see Compound Semiconductor Dec 2000/Jan 2001, p23). "This is a tremendous vote of confidence in Applied Optoelectronics and our VCSEL technology from our investors," said Thompson Lin, president and CEO. "With this infusion of capital, we will be able to accelerate the development and manufacture of new long-wavelength laser products. By leveraging our extensive experience in MBE growth of semiconductor laser structures, we have created a product that is squarely targeted at the metropolitan area network with link distances of 80 km or less." VCSEL developments According to AOI s director of marketing, Stefan Murry, the company is developing several different 1550 nm VCSEL designs. The device currently being shipped is an optically-pumped external cavity VCSEL. The company manufactures the VCSEL structure and obtains the external cavity components from an outside source. Featuring a tuning range of 2530 nm, the VCSEL achieves an output power of 6 mW in CW mode. "We also plan to introduce a range of electrically-pumped monolithic 1550 nm devices with 1 mW output sometime towards the middle of next year," says Murry. "These will be 2.5 Gbit/s emitters, and will include single VCSEL devices, and tunable VCSELs." The new monolithic VCSELs will employ InP substrates and contain InGaAsP active regions grown using the company s MBE systems. "We are addressing two major areas that have been preventing the proliferation of VCSELs at longer wavelengths," says Murry. "For the monolithically-grown DBR mirror stacks, we have improved the reflectivity of the layers, which has enabled us to reduce the total thickness of these stacks. This allows more heat to be removed from the active region, which is an important factor at longer wavelengths due to temperature-dependent losses such as Auger recombination. We have also optimized the active region by employing materials with improved gain properties compared to existing systems. The result is higher gain and lower loss, which increases the VCSEL output power."
