Cascaded counter-propagating nonlinear interactions in highly-efficient sub-µm periodically poled crystals

Area of Science:

• Nonlinear optics
• Photonics
• Materials science

Background:

• Mirrorless optical parametric oscillators (MOPOs) leverage counter-propagating photons for intrinsic feedback, offering unique spectral and coherence properties.
• MOPOs have broad applications in spectroscopy and quantum communications.
• A key challenge is phase-matching counter-propagating waves in nonlinear materials.

Purpose of the Study:

• To develop a reliable fabrication technique for highly-efficient sub-micrometer periodically poled Rb-doped KTiOPO4.
• To demonstrate cascaded counter-propagating interactions in engineered nonlinear photonic structures.

Main Methods:

• Fabrication of sub-micrometer periodically poled Rb-doped KTiOPO4 using a domain-engineering technique.
• Experimental demonstration of cascaded counter-propagating nonlinear optical processes.

Main Results:

• Achieved highly-efficient sub-micrometer periodically poled Rb-doped KTiOPO4.
• Demonstrated the first cascaded counter-propagating interactions.
• Exceeded 60% pump depletion in the cascaded process, showcasing high efficiency.

Conclusions:

• The developed domain-engineering technique enables efficient fabrication of nonlinear photonic structures for MOPOs.
• This breakthrough facilitates previously unfeasible counter-propagating schemes and devices.
• The results pave the way for advanced optical parametric devices.