Polarization control of long-wavelength vertical cavity surface emitting laser (VCSEL) fabricated by orientation-mismatched wafer bonding

This thesis explores fabrication and investigation of controlling polarization of light output of a long-wavelength VCSEL. The conventional VCSELs are fabricated on symmetric (001) crystal plane which does not have fundamental polarization selection rule. Unstable polarization of the VCSEL limits its use as a transmitter and application to other polarization-sensitive scheme.; In order to achieve a polarization-controlled VCSEL, we fabricated its active region on (113)B plane. The (113) and other planes of (11n ) family are asymmetric, which leads to asymmetric stress and anisotropic optical gain. A large dichroism such as anisotropic gain is expected to be most effective in stabilizing polarization.; The active region for 1.3-mum wavelength VCSEL was grown on (113)B InP substrate by metal-organic chemical vapor deposition (MOCVD). Since this plane is asymmetric, it is more difficult to grow on than (001) plane. The growth condition was optimized to low-migration condition in order to achieve flat surface morphology and good crystalline quality. We also observed that the doping efficiency of both n-type and p-type impurities was higher than that on (001) surface.; To complete the VCSEL, the active region on (113)B InP was integrated to (001) GaAs-based distributed Bragg reflectors (DBRs) by wafer bonding technique. Only by this technique, we can integrate such materials with different crystallographic orientations without degrading material qualities significantly. The VCSEL had maximum output power polarized at [332¯] axis, while minimum power was orthogonal at [1¯¯10] axis. An index-guiding mesa structure was fabricated in an asymmetric shape. Depending on its orientation of asymmetry, the index-guiding either enhanced or distracted the polarization originating from gain anisotropy. Statistical data showed that with appropriate index-guiding structure, the VCSEL polarization can be stabilized with high yield over a wide operation range. We also performed high-speed modulation on the VCSEL. The bit error rate (BER) was the same on 2 types of the measurement links with and without having a polarization-sensitive part. This result is a strong proof that the polarization of this VCSEL is stable under practical operation.