Efficient photoinduced second-harmonic generation in silicon nitride photonics

Silicon photonics lacks a second-order nonlinear optical (chi((2))) response in general, because the typical constituent materials are centrosymmetric and lack inversion symmetry, which prohibits chi((2)) nonlinear processes such as second-harmonic generation (SHG). Here, we realize high SHG efficiency in silicon photonics by combining a photoinduced effective chi((2)) nonlinearity with resonant enhancement and perfect phase matching. We show a conversion efficiency of (2,500 +/- 100)% W-1 that is two to four orders of magnitude larger than previous field-induced SHG works. In particular, our devices realize milliwatt-level SHG output powers with up to (22 +/- 1)% power conversion efficiency. This demonstration is a breakthrough in realizing efficient chi((2)) processes in silicon photonics, and paves the way for further integration of self-referenced frequency combs and optical frequency references.

Automated summary

The research demonstrates efficient second-harmonic generation in silicon photonics through a combination of effective chi((2)) nonlinearity, resonant enhancement, and perfect phase matching. The breakthrough shows significantly higher conversion efficiency and output power than previous works, paving the way for further integration of self-referenced frequency combs and optical frequency references in the field.