New materials and process technologies for vertical cavity surface emitting lasers

Surface emitting (SE) lasers or vertical cavity SE lasers (VCSELs) are now considered to be utilized as devices in various optical systems such as networks, optical parallel interconnects, laser printers, and ultra-parallel optoelectronics. The author reviews the progress of VCSELs for a wide range of optical spectra based on GaInAsP, GaIn(N)As, GaAlAs, AlGaInP, ZnSe, GaN, and related compounds and discusses some new aspects. The materials for semiconductor lasers now cover most III-V compound alloys. The problems which should be seriously considered for making vertical cavity SE lasers are: (A) Highly reflective and transparent DBRs; (B) Minimization of optical losses; (C) Maximization of optical-field and gain overlap; (D) Electrode-formation to reduce the resistivity for high efficiency operation; and (E) Heat sinking for high temperature and high power operation. The present technical status of VCSELs is reviewed in various spectral regions (a) 1550 nm: The epitaxial bonding of GaInAsP-InP/GaAs-AlAs mirrors exhibit CW operation up to 64 /spl deg/C. Further development may be necessary to compete with edge emitters employing DFB and spotsize transformer (SST) structures. (b) 1300 nm: A buried structure is utilized together with a thermally conductive MgO/Si mirror demonstrating the first room temperature (RT) CW operation. The highest operation is up to 34 /spl deg/C.