Nonlinear directional coupler in periodically poled lithium niobate

Area of Science:

• Nonlinear optics
• Waveguide optics
• Quantum optics

Background:

• Cascaded nonlinearity in quasi-phase-matched second-harmonic generation is a key phenomenon for all-optical switching.
• Optimizing nonlinear wave propagation in coupled waveguides is crucial for efficient all-optical devices.

Purpose of the Study:

• To investigate nonlinear wave propagation in coupled waveguides.
• To optimize cascaded nonlinearity for efficient all-optical switching.
• To demonstrate high-contrast, ultrafast all-optical switching at low power.

Main Methods:

• Experimental investigation of nonlinear wave propagation.
• Utilizing quasi-phase-matched second-harmonic generation with cascaded nonlinearity.
• Designing a specific wave-vector-mismatch distribution along the propagation axis.

Main Results:

• Optimized cascading for low fundamental depletion was achieved.
• High-contrast, ultrafast all-optical switching was successfully observed.
• Switching powers as low as tens of watts were demonstrated.

Conclusions:

• The proposed method effectively optimizes nonlinear wave propagation for all-optical switching.
• Low fundamental depletion and low switching powers are achievable with this technique.
• This research contributes to the development of efficient all-optical switching devices.