Second harmonic generation is an efficient way to create coherent radiation at wavelengths that are not accessible with standard laser sources. In this work the authors demonstrate second harmonic generation from 1550 to 775 nm in a polymer photonic integrated circuit via the hybrid integration of a periodically poled lithium niobate crystal. The bulk crystal is inserted in an on-chip free-space section between two waveguide coupled GRIN lenses. Fiber to fiber conversion efficiencies were 0.03%/W for a continu-ous wave laser source and 100%/W for a femtosecond laser source. Furthermore, third and fourth harmonic light at 517 and 388 nm was observed.

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