Geiss, R.R.GeissSaravi, S.S.SaraviSergeyev, A.A.SergeyevDiziain, S.S.DiziainSetzpfandt, F.F.SetzpfandtSchrempel, FrankFrankSchrempelGrange, R.R.GrangeKley, Ernst-BernhardtErnst-BernhardtKleyTünnermann, AndreasAndreasTünnermannPertsch, ThomasThomasPertsch2022-03-052022-03-052015https://publica.fraunhofer.de/handle/publica/24114410.1364/OL.40.002715Nanoscale waveguides are basic building blocks of integrated optical devices. Especially, waveguides made from nonlinear optical materials, such as lithium niobate, allow access to a broad range of applications using second-order nonlinear frequency conversion processes. Based on a lithium niobate on insulator substrate, millimeter-long nanoscale waveguides were fabricated with widths as small as 200 nm. The fabrication was done by means of potassium hydroxide-assisted ion-beam-enhanced etching. The waveguides were optically characterized in the near infrared wavelength range showing phase-matched second-harmonic generation.en535journal article