This Small Business Innovation Research (SBIR) Phase I project proposes to use a novel design and fabrication approach that will bring Vertical Cavity Surface Emitting Lasers (VCSELs) out of their current niche applications and will open the way to their widespread use where currently edge emitting lasers are utilized. These VCSELs can be designed over a broad range of wavelengths covering near-infrared and approaching mid infrared (800nm to 2,500nm). The narrow linewidth and stable linear polarization of these VCSELs make them suitable for use in spectroscopy, communications and solid state laser pumping. What makes this possible is substrate flexibility combined with a special High Contrast Grating (HCG) mirror used for single-mode linearly polarized output. High efficiency and high output power are achieved by very low electrical resistance and efficient heat sinking. The first prototype will have an emission wavelength of 1550nm with the goal of offering a more compact and lower cost alternative to DFB lasers in long-haul fiber optics.
The broader impact/commercial potential of this project extends to the fields of fiber communication, spectroscopy, and high power solid state lasers. Next generation VCSELs to be developed in this project will have the single mode and narrow linewidth of a Distributed Feedback (DFB) laser and the beam quality and low cost of a VCSEL at any near infrared wavelength. Of particular interest in communication systems are the reduction of cost per bit, and power consumption per bit of transmitted data. Implementing the proposed VCSELs in fiber optic transceivers results in reduced cost and reduced power consumption over existing edge emitter based solutions. Reducing power consumption in turn leads to miniaturization and high density assembly, which further reduces the cost. Particularly challenging requirements for long wavelength VCSELs to meet are high optical output power and narrow linewidth. The proposed approach makes possible for these VCSELs to meet both of these requirements and to become an attractive candidate not only for fiber communications, but also for use as pump sources for high power solid state lasers. Furthermore, the lack of wavelength constraints makes these devices ideal as sources for overtone spectroscopy in the near infrared.
Vertical-Cavity Surface-Emitting Lasers (VCSEL) where available, would be generally preferred to conventional edge emitting distributed feedback (DFB) lasers because of their superior beam quality, their on-wafer testability, and their lower fabrication cost. These reasons once combined with advances in fabrication technology that this project supported, make the VCSEL competitive with Distributed Feedback Lasers and contribute to the continuing growth of the VCSEL market. The market is currently driven primarily by demand in the computer optical mouse, and fiber optic transceivers used in short distance optical links, typically in IT and telecommunications applications. We are building the next generation VCSELs that are single mode, high power, and substrate independent. These characteristics will enable VCSELs to break out of their current niche market into broader applications in communications and instrumentation. Their substrate independence will make it possible to process them on silicon and other materials suitable for the final application. In Phase I, we completed all the originally planned tasks including the following: We successfully demonstrated "substrate independent" VCSELs by transferring the epitaxial material to another substrate prior to processing. To the extent of our knowledge this has never been done before. We successfully processed both sides of an entire epitaxial film. We designed next generation substrate-independent, high beam-quality VCSELs to be fabricated in a potential follow on program. We will present an invited paper titled "Advanced Substrate-Independent VCSELs" at the IEEE Photonics Society Summer Topicals conference in July 2013 based on this NSF supported work.
