Eric J. Lim

Infrared radiation generated by quasi‐phase‐matched difference‐frequency mixing in a periodically poled lithium niobate waveguide

We report quasi‐phase‐matched difference‐frequency generation of 2.1 μm radiation at room temperature using the d33 nonlinear coefficient in a periodically poled lithium niobate channel waveguide. A tunable Ti:Al2O3 laser (λ≊0.8 μm) and a Nd:YAG laser (λ=1.32 μm) were the pump and signal sources, respectively. With 160 mW of 0.81 μm and 1 mW of 1.32 μm radiation coupled into the waveguide, 1.8 μW of 2.1 μm radiation was generated, tunable over a 6 nm bandwidth. We also show that the annealed proton exchange process can change the shape of ferroelectric domains in lithium niobate.

Quasi-Phase-Matched Interactions In Lithium Niobate

Phase-matching nonlinear interactions by periodic variations in the nonlinear susceptibility, quasi-phase-matching, offers advantages in accessible tuning range and in choice of nonlinear coefficients over the conventional birefringent technique. Periodically reversed ferroelectric domains can be used to create monolithic structures with the necessary high-spatial-frequency variations in the nonlinear susceptibility. We present two techniques for the fabrication of periodically-poled lithium niobate crystals, and results for bulk and guided-wave second harmonic generation of blue and green light.

Noncritical phase matching for guided-wave frequency conversion

Inhomogeneities in waveguide dimensions are a serious problem for guided‐wave frequency conversion devices. We discuss waveguide designs that make the phase matching ‘‘noncritical’’ with respect to small changes in dimensions. Application of noncritical phase matching results in larger fabrication tolerances, facilitating the practical realization of nonlinear devices with long interaction lengths. We experimentally demonstrate the existence of a noncritical thickness in a lithium niobate waveguide, and analyze the dimensional tolerances for second‐harmonic generation in a polymer waveguide.

Quasi-phase-matched frequency conversion in lithium niobate and lithium tantalate waveguides

We discuss second harmonic generation of green and blue light in periodically-poled LiNbO3 and LiTaO3 waveguides, and difference frequency generation of infrared radiation in periodically-poled LiNbO3 waveguides.