Highly efficient frequency doubling with a doubly resonant monolithic total-internal-reflection ring resonator

Area of Science:

• Nonlinear optics
• Materials science
• Integrated photonics

Background:

• Second-harmonic generation (SHG) is crucial for frequency conversion in lasers.
• MgO:LiNbO(3) (magnesium oxide-doped lithium niobate) offers excellent nonlinear optical properties.
• Ring resonators enhance light-matter interaction for nonlinear processes.

Purpose of the Study:

• To demonstrate efficient doubly resonant second-harmonic generation (DR-SHG).
• To utilize a monolithic total-internal-reflection (TIR) MgO:LiNbO(3) ring resonator.
• To achieve high conversion efficiency with independent fundamental and harmonic wave coupling.

Main Methods:

• Fabrication of a coating-free monolithic TIR MgO:LiNbO(3) ring resonator.
• Maintaining resonance for both fundamental (1.06-microm) and harmonic waves via temperature and laser frequency control.
• Employing two calcite coupling prisms to frustrate TIR for independent input/output coupling.

Main Results:

• Successful demonstration of DR-SHG in the MgO:LiNbO(3) ring resonator.
• Achieved external conversion efficiencies exceeding 50%.
• Efficient operation at input fundamental powers above 5 mW.

Conclusions:

• Monolithic TIR MgO:LiNbO(3) ring resonators are effective for efficient DR-SHG.
• The demonstrated coupling scheme allows independent control of fundamental and harmonic waves.
• This approach offers a promising route for compact and efficient frequency conversion devices.