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, $BiFeO3$⁠, are reported. The material has a direct band gap at $442nm$ wavelength $(2.81eV)$⁠. 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 $∣d22∣=298.4±6.1pm∕V$ at a fundamental wavelength of $800nm$⁠.