Real-Index Guided Blue-Green Laser Diode with Small Beam Astigmatism Fabricated Using ZnO Buried Structure

Real index-guided blue-green lasers with a small beam astigmatism have been demonstrated. A ZnO buried layer with low refractive index and high resistivity was used to obtain the real index-guided structure. The ridge stripe was fabricated by electron cyclotron resonance plasma etching with Cl2/H2 discharge which realizes anisotropic etching. The beam astigmatism value for the ZnO buried ridge waveguide laser was measured to be less than 0.5 µm as a result of the real index-guiding effect, in contrast to 25 µm for the conventional gain-guided laser. A stable single lateral mode operation was also obtained at up to 18 mW for the real index-guided laser.