Four-layer optical waveguide device using isopropyl-4-acetylphenylurea (IAPU)

The new organic crystal isopropyl-4-acetylphenylurea (IAPU) was identified as a promising candidate for frequency doubling to the blue light region. The nonlinear optical d-coefficient, d₂₂ = 35 pm/V was obtained at 1064 nm by the Maker-fringe technique. The crystal's transmitting range is 380-1400 nm. Thin film of IAPU crystallize appropriately for waveguide applications. Thickness-noncritical phase-matching (TNCPM) in a four-layer waveguide structure using an IAPU crystal as a top cladding layer is proposed. Modal dispersion calculations for four-layer waveguides demonstrate the possibility of TNCPM from TE₀$+ω/ mode to TE₁$+2ω/ mode by adjusting the refractive indices of the two guiding layers, where the modal dispersion curves are intentionally designed to be tangent over a limited waveguide thickness. The TNCPM condition in an organic-inorganic hybrid four-layer waveguide structure is discussed as are its relaxation of tolerance requirements on waveguide fabrication.