Second Harmonic Generation in Thin Film II–VI Optical Waveguides

The absolute values and dispersion of the second harmonic generation (SHG) coefficient of the cubic wide‐gap II–VI semiconductors Zn Te, ZnSe, and ZnS are investigated within the spectral range from 1047 to 1321 nm. The fundamental beam is generated by a Nd:YLF laser and by a tunable KTP optical‐parametric oscillator (OPO) pumped by a ps‐Ti:sapphire laser system. The measured values of the SHG coefficient are significantly higher than in commercially used birefringent crystals as KDP or ADP. In a further step symmetric single crystalline ZnSe/ZnTe/ZnSe/GaAs(001) waveguides are grown by metalorganic vapour phase epitaxy (MOVPE). Using end‐fire coupling a strong phasematched signal of the 1170.5 nm fundamental wave is observed. Phase matching is achieved by coupling the TE 0 fundamental mode to the TM 2 second harmonic mode.