Second harmonic generator with an on-chip wavelength division demultiplexer

The second harmonic generation (SHG) technology based on quasi-phase matching in periodically poled lithium niobate (PPLN) has reached a high level of maturity. However, the generated second harmonic signal is often overwhelmed by pump light, making direct application challenging. In this paper, we have designed and fabricated, for the first time, to the best of our knowledge, an integrated second harmonic generation device with on-chip wavelength division demultiplexing (WDDM). The device achieves a second harmonic conversion efficiency of 1200% W^-1cm^-2 and provides approximately 20 dB attenuation in the telecom C-band near 1550 nm, while introducing about 4 dB insertion loss in the visible light near 775 nm, significantly improving the signal-to-noise ratio. The WDDM section employs a cascaded linearly tapered waveguide design, which offers broadband coupling efficiency. This result shows promise as a foundation for fully integrated quantum photonic chips.