Phase-mismatching effects in the internal second-harmonic generation in InGaAs quantum-well laser diodes

We have characterized the role of phase-mismatching in the spectral distrib ution of the internal second-harmonic generation (ISHG) in the CW operation of high-power InGaAs quantum-well laser diodes emitting at around 960 nm. The observed pairs of narrow blue-green peaks of ISHG have symmetrical spec tral positions with respect to the central peak of the pure second harmonic at similar to 480 nm, suggesting that their generation in the laser wavegu ide is most probably mediated by a mechanism of reciprocal cancellation of the respective phase-mismatch vectors. The relatively strong emission of th e ISHG radiation at the output mirror facet indicates that this second-orde r nonlinear optical process is enhanced by waveguiding in the laser active region.