Low Cost Lasers for the Next Generation Internet using High Contrast Subwavelength Optics
Here we present a new technology aimed at providing high speed internet and telecommunications at a very low cost, both in dollars and energy. The building block for this is vertical cavity surface emitting lasers (VCSELs) which can be manufactured for just a few pennies and are the lasers with the lowest energy requirements available today. The problem with existing low cost VCSELs is that their wavelength (typically 850 nm) is too short for long distance transmission (>200 meters). The optimal wavelength for long distance optical transmission is 1.55 µm, which travels the longest distance in an optical fiber. While people have been able to fabricate VCSELs operating 1.55 µm previously, this came with some exotic processes that made them much more expensive than their 850 nm cousins.
Using the new enabling technology of high contrast gratings, ultra thin, highly reflective mirrors made up of nanometer-scale semiconductor bars, we have been able to fabricate 1.55 µm VCSELs using a simple and low cost process. The initial results are promising – the devices already meet many of the requirements needed for telecommunications applications. The areas of temperature stability and high speed modulation are still under research, but meeting the needed specifications appears attainable. These VCSELs may enable low cost but high speed internet connections, helping to expand the availability of internet access and ushering in the next generation of internet applications.