Second harmonic generator with an on-chip wavelength division demultiplexer

Area of Science:

• Photonics
• Quantum Optics
• Materials Science

Background:

• Second Harmonic Generation (SHG) using Periodically Poled Lithium Niobate (PPLN) is a mature technology.
• A key challenge in SHG is the strong residual pump light overwhelming the generated signal.
• This limits the direct application of SHG devices in various fields.

Purpose of the Study:

• To design and fabricate an integrated SHG device incorporating Wavelength Division Demultiplexing (WDDM).
• To overcome the limitation of pump light interference in SHG.
• To enhance the signal-to-noise ratio for visible light generation.

Main Methods:

• Fabrication of an integrated device combining SHG and WDDM functionalities.
• Utilizing a cascaded linearly tapered waveguide design for the WDDM section.
• Characterization of conversion efficiency, pump light attenuation, and insertion loss.

Main Results:

• Achieved a high second harmonic conversion efficiency of 1200% W⁻¹cm⁻².
• Demonstrated approximately 20 dB attenuation of the telecom C-band pump light (1550 nm).
• Reported a low insertion loss of about 4 dB for the visible light (775 nm).

Conclusions:

• The integrated SHG-WDDM device significantly improves the signal-to-noise ratio.
• The broadband coupling efficiency of the tapered waveguide WDDM is effective.
• This technology provides a promising foundation for fully integrated quantum photonic chips.