Quasi-periodic optical superlattice generates quasi-phase-matched third-harmonic signal

Quasi-periodic optical superlattice generates quasi-phase-matched third-harmonic signal

Quasi-periodic structure can be introduced into nonlinear optical materials such as lithium tantalate (LiTaO3) and used for quasi-phase-matching second-harmonic generation. Now researchers from the National Laboratory of Solid State Microstructures at Nanjing University and the Center for Advanced Studies in Science and Technology (both Nanjing, China) have shown how to couple second-harmonic generation and sum-frequency generation through quasi-phase-matching to directly produce a third harmonic with high efficiency through a coupled parametric process.

Efficient third-harmonic generation is conventionally achieved by a two-ste¥process that uses two nonlinear optical crystals--the first one for second-harmonic generation and the second for sum-frequency generation. This new result verifies that high-order harmonics can be generated in a quadric nonlinear medium by several quasi-phase-matching processes and, therefore, exhibit a possible important application of quasi-periodic structure materials in nonlinear optics.