Highly efficient second harmonic generation in hyperbolic metamaterial slot waveguides with large phase matching...

Area of Science:

• Photonics
• Metamaterials
• Nonlinear Optics

Background:

• Second harmonic generation (SHG) is crucial for frequency conversion in optics.
• Bridging mid-infrared (IR) and near-IR wavelengths presents a significant challenge for efficient SHG.
• Existing plasmonic structures often require larger footprints and higher power.

Purpose of the Study:

• To theoretically investigate highly efficient SHG in a coupled hyperbolic metamaterial waveguide.
• To achieve efficient frequency conversion between mid-IR and near-IR wavelengths.
• To explore the potential for chip-scale all-optical signal processing.

Main Methods:

• Utilizing a nonlinear-polymer-filled nanoscale slot within a coupled hyperbolic metamaterial waveguide.
• Engineering geometrical parameters to satisfy collinear phase matching for specific wavelengths (3,100 nm fundamental, 1,550 nm second harmonic).
• Analyzing field overlap and enhancement in the nonlinear region to maximize the nonlinear coupling coefficient.

Main Results:

• Achieved normalized conversion efficiency exceeding 6.37 × 10^5 W⁻¹cm⁻² at a low pumping power of 100 mW.
• Demonstrated efficient SHG in a compact device length of 2.19 µm.
• Showcased high phase matching tolerance, including low sensitivity to fabrication errors and a broad pump bandwidth.

Conclusions:

• The proposed metamaterial waveguide offers superior performance compared to plasmonic-based structures.
• This scheme effectively links mature near-IR technologies to the mid-IR regime.
• The device holds significant potential for integrated chip-scale all-optical signal processing applications.