This Small Business Innovation Research (SBIR) Phase II project will demonstrate significantly improved output power, temperature range of operation, and reliability of red VCSELs. Commercialization of red VCSEL technology has been plagued by the limited temperature range and output power of the devices and unknown reliability characteristics. The Phase I project demonstrated the 1) feasibility of improving output power and temperature range through a number of techniques, 2) that the fundamental limit of the temperature range is at least as high as 125°C, and 3) dramatically improved reliability. The Phase II approach proposed here breaks away from traditional models for fabricating VCSELs and consists of a variety of growth and fabrication methods allowing us to provide a high thermal conductivity path from the active region to the package. The goals and expected technical results are to demonstrate > 0.5mW single mode, and >1mW multi-mode useful output power at 670nm at 85°C, and the same power output power objectives for 655nm at 65°C on a reproducible basis. This project will also demonstrate greater than 10,000 hours device lifetime at 85°C continuous operation. Project activities consist of design, wafer growth and fabrication, performance testing, and reliability testing.
To date, the only commercially available VCSELs have been at 780nm to 850nm, due to the substantial materials challenges at other wavelengths. This proposed effort is applicable to a variety of VCSEL wavelengths (similar thermal issues exist at 1310nm to 1550nm), as well as other optoelectronic devices. Commercially, a significant enhancement in red VCSEL performance can enable the migration of plastic fiber based home and auto networks to higher data rates, faster and higher quality laser printing, longer distance and more precise motion control sensing, new types of portable or wearable medical sensing, and improved robustness and cost of radiography equipment. The success of this project not only creates a significant business opportunity for a red VCSEL supplier, but also enhances the competitiveness of customers by making available a valuable new technology. The reduction in power consumption and improvement in medical technology costs address particularly important societal issues.
The goal of this grant was to develop red VCSEL technology that would address substantial commerical opportunities. VCSELs are a type of semiconductor laser that combines the performance advantages of lasers with the manufacturing advantages of LEDs. Infra-red VCSELs have been available for some time and have been widely applied to fiber optic data communication applications such as Local Area Networks and Storage Area Networks. However, reliable red VCSELs have not been commercially available, but have benefits to other applications such as medical and industrial sensors and consumer electronics. The grant addresses the red VCSEL design issues including operation over a wider temperature range, higher output power, higher speed and longer lifetimes. We also developed the technology for a consumer targeted plastic optical fiber data link which was built upon the red VCSEL technology, and which would allow us to capture greater value in the marketplace. During the course of the project, we were able to improve the output power of an individual VCSEL by a factor of 4, and an array by a factor of 10. The temperature range of operation was increased to 80 degrees Celcuis. In the lifetime of the device, we identified a problem that severely limited the lifetime of the devices operated in a humid environment. We also identified a solution and demonstrated its effectiveness in improving the lifetime. We demonstrated a communication link based upon plastic optical fiber operating up to 10 Gigabits per second that has a size that makes it suitable for insertion into consumer based equipment such as laptops or tablet computers. Customers are now applying our VCSELs in a variety of ways. As a result of the improved technology, our VCSELs facilitate lower power, lower cost gene sequencing equipment, lower power medical and dental imaging equipment, high accuracy medical sensors that measure the oxygen content in blood and tissue, higher resolution industrial sensors, and laptops and tablets with improved display and camera capabilities and improved processor speeds.
