Second harmonic generation in potassium niobate thin films

Green light produced by second harmonic generation has been observed in an epitaxial orthorhombic KNbO3 thin film planar waveguide produced by ion-beam sputter deposition on a (100)-oriented MgO single crystal substrate. A Nd:YLF laser beam, with a wavelength of 1.053 μm and ∼80 ps, 100 MHz pulses under mode-locked operation, was coupled into the waveguide using a rutile prism, and a green light streak 3–4 mm long was seen in the guide. The TM0 mode of the input beam was phase matched to the TE1 mode of the second harmonic for a film thickness of 2300 Å. Second harmonic generation was also observed in a nonwaveguided configuration on thicker (4600–6500 Å) films on both MgO and KTaO3 substrates.