Large nonlinear optical coefficients in pseudo-tetragonal BiFeO3 thin films

Abstract

Biaxial strain induces a phase transition from a pseudo-rhombohedral (R) to pseudo-tetragonal (T) phase in BiFeO3 (BFO) thin films. Using optical second harmonic generation, we measure the nonlinear optical dij coefficients at a fundamental wavelength of 1550 nm for R and T-BFO thin films. A large increase of the dij magnitudes is observed for T-BFO in comparison to R-BFO. The dij magnitudes for T-BFO were measured to be: |d33|=18.1±2.4, |d31|=60.8±8.1, and |d15|=47.0±4.2, and for R-BFO: |d33|=15.1±2.1, |d31|=8.5±1.2, |d15|=0.9±0.1, and |d22|=18.7±2.6 (pm/V). The strain-enhanced nonlinear optical properties of T-BFO thin films make them potentially useful for optical applications.

Nonlinear optical and magnetic properties of BiFeO3 harmonic nanoparticles

“…A fourth set (set 4) can also be obtained from ab initio simulation. 21 Although Haislmaier et al 22 correctly pointed out that the set 2 of d ij values does not account for absorption at 400 nm, this set, which was derived for 800 nm excitation, is the only one which allowed us to fit our experimental results as shown in 1 It can be noticed that only the relative d ij coefficients are involved in the fitting procedure. We thus find that the relative d ij values of set 2 correctly fit our experimental response.…”

“…48 Very few studies have focused on the BFO optical second harmonic properties but, recently, the relative values of the d ij tensor coefficients were determined at 1064 nm from single crystal measurements. 49 In another study, 22 a careful determination of the absolute d ij coefficients was performed at 1550 nm in the case of both rhombohedral and strain-induced tetragonal thin films. Experimental results were found to be consistent with ab initio calculations.…”

“…BFO belongs to space group R3c and the SHG tensor can be described with four nonzero independent components: d 22 , d 15 , d 31 , and d 33 . 48 Very few studies have focused on the BFO optical second harmonic properties but, recently, the relative values of the d ij tensor coefficients were determined at 1064 nm from single crystal measurements.…”

“…Currently in the literature, a few different sets of relative d ij values for BFO are present, as reported in Table SII. 45 The first set (set 1) was derived from BFO single crystal measurements 49 at 1064 nm, the second (set 2) 47 and third (set 3) 22 were obtained from BFO thin film measurements at 800 nm and 1550 nm, respectively. A fourth set (set 4) can also be obtained from ab initio simulation.…”

“…Being extensively studied for its magnetoelectric behavior, BFO also has attractive ferroelectric properties with high spontaneous polarization. 20 Moreover, recent studies give evidences of a very promising nonlinear optical efficiency, 21,22 which was found to be superior to the standard oxide materials previously introduced. Second, bulk BFO is antiferromagnetic but nanoparticles show weak ferromagnetism which was attributed to various possible causes: size effects, 23 extrinsic effects due to cFe 2 O 3 impurities, 24 or oxygen vacancies.…”