Efficient photo-induced second harmonic generation in silicon nitride photonics

Area of Science:

• Photonics
• Nonlinear Optics
• Materials Science

Background:

• Silicon photonics typically lacks second-order nonlinear optical (χ(2)) response due to the centrosymmetric nature of constituent materials.
• This lack of inversion symmetry prohibits nonlinear processes like second harmonic generation (SHG).

Purpose of the Study:

• To achieve record-high SHG efficiency in silicon photonics.
• To overcome the inherent limitations of centrosymmetric silicon for nonlinear optical applications.

Main Methods:

• Employing a photo-induced effective nonlinear (χ(2)) susceptibility.
• Utilizing resonant enhancement and perfect phase-matching techniques.
• Fabricating silicon photonic devices capable of efficient SHG.

Main Results:

• Demonstrated a record conversion efficiency of (2,500 ± 100) %/W for SHG.
• Achieved milliwatt-level SHG output powers with up to (22 ± 1)% power conversion efficiency.
• Exceeded previous field-induced SHG efficiencies by 2 to 4 orders of magnitude.

Conclusions:

• This work represents a major breakthrough in realizing efficient nonlinear optical (χ(2)) processes in silicon photonics.
• The demonstrated high SHG efficiency paves the way for integrating self-referenced frequency combs and optical frequency references.
• Enables new possibilities for advanced functional photonic devices based on silicon.