Abstract

Direct second harmonic generation using a GaAIAs laser diode and KNbO₃ offers the possibility of efficient generation in the 400-450-nm spectral range. However, the SHG efficiency using laser diodes has been limited in the past by their relatively low available power output and/or poor spectral and beam quality. Recently, significant progress has been made in obtaining a diffraction- limited beam from a high-power laser diode array by injection locking.¹ A single-lobe far-field beam with 70-80 % of the output power contained in the diffraction-limited lobe has been demonstrated in a 500-mW gain-guided laser array.² The high electrical to optical conversion efficiency, high-power and diffraction-limited output characteristics of injection-locked arrays make them suitable sources for SHG. With 180 mW of cw array output coupled into a temperature tuned KNbO₃, 0.24 mW of 420- nm output was obtained. The a-cut 3- X 3.7- X 6- mm KNbO₃ crystal was mounted in a thermoelectrically temperature-controlled enclosure. A linearly polarized output of array at 842.5 nm was phase matched noncritically at -22.75°C with a measured halfwidth of temperature tuning range at 0. 5.°C. The results correspond to a 30-dB improvement over previously demonstated power in cw SHG using laser diode sources.³

© 1988 Optical Society of America