Efficient blue light generation by frequency doubling and sum-frequency mixing of laser diodes in KnbO3

Abstract

Direct second-harmonic and sum-frequency generation (SHG, SFG) with near infrared semiconductor laser diodes (LDs) offers the possibility of robust, compact and reliable blue lasers. KNbO3 crystals are very attractive for frequency conversion of near infrared DLs into the blue spectral range due to its high nonlinear optical coefficients, its favourable noncritical phase-matching (PM) configurations, and the absence of any optical damage and gray tracking effects for cw blue power levels of up to 200 mW1. Efficient blue light generation at 430 nm and 490 nm by noncritical type I PM SHG with LDs in KNbO3 has been reported for single-pass2,3, resonant4,5, and waveguide configurations6. Other wavelengths in the 415 to 475 nm spectral range can be efficiently generated by making use of the nonlinear optical coefficient d32 of KNbO3 for noncritical type I PM SFG with commercially available single-mode AlGalnP, AlGaAs and InGaAs laser diodes.