Linear and nonlinear optical properties of BiFeO₃

Using spectroscopic ellipsometry, the room temperature refractive index and absorption versus wavelength of the ferroelectric antiferromagnet bismuth ferrite, BiFe O3, are reported. The material has a direct band gap at 442 nm wavelength (2.81 eV). Using optical second harmonic generation, the nonlinear optical coefficients were determined to be d15 d22 =0.20±0.01, d31 d22 =0.35±0.02, d33 d22 =-11.4±0.20, and ∫ d22 ∫ =298.4±6.1 pmV at a fundamental wavelength of 800 nm.