ABSTRACT
James S. Harris, Jr. Solid State and Photonics Lab, Stanford University, CISX 328, Stanford, CA 94305-4075, USA
Abstract. Dilute nitride GalnNAs and GalnNAsSb alloys grown on GaAs have quickly become excellent candidates for a variety of lower cost 1.21.6 pm lasers, optical amplifiers and high power Raman pump lasers that will be required for advanced communications systems. Two particularly critical devices are 1) vertical cavity surface emitting lasers (VCSELs) which must operate un-cooled at high data rates (>10Gbps), and 2) high power (>500mW) edge emitting lasers for Raman amplifier pumps. Despite the fact that these materials have been grown successfully, several challenges remain, including the limited solubility of N, phase segregation, non-radiative defects caused by the low growth temperature and ion damage from the N plasma source. The addition of Sb significantly improves the epitaxial growth and optical properties of the material at wavelengths greater than 1.3 pm. By adding Sb to the alloy, luminescence has been greatly enhanced between 1.3-1.6pm. This paper describes progress in overcoming some of the material challenges, particularly phase segregation and ion damage and progress in realizing record setting edge emitting lasers and the first VCSELs operating at 1.5 pm based on GalnNAsSb QWs grown by solid source MBE on GaAs. 1
1. Introduction In spite of the incredibly rapid growth and capacity of current optical communications networks, it should come as little surprise that they are now limited by the on/off ramps, the switching hubs from the main high speed/capacity backbone to the slow feeder lines to the final destination. This bottleneck on the information highway is now the focus of considerable effort to create truly high-speed metro (MAN) and local (LAN) area networks [1-3]. This is the driving force behind the development of low cost, 1.3-1.6 pm, directly modulated, un-cooled VCSELs because in contrast to the backbone, high-speed direct access will require hundreds of million lasers which must be low cost. Compared to current generation lasers, the cost will have to be reduced by at least 50X. While this might seem a very daunting challenge, first generation LANs based on low cost 850 nm GaAs VCSELs have demonstrated that they can meet the cost, reliability, speed and thermal requirements for such lasers, the only problem being that they operate at the
wrong wavelength and 10 Gbps transmission is only possible over about 50 m (NOTkm)\ [1-3]. Thus, longer wavelength lasers are absolutely essential to achieve useful transmission distances at this data rate. Despite sizeable efforts to realize low cost, long wavelength VCSELs, limitations in the previously used semiconductor alloy systems have made this an extremely difficult challenge.
