Photorefractive properties of Fe, Zn co-doped near stoichiometric LiNbO3 crystals at moderate intensities (0.5–6 W/cm2)

Iron and zinc co-doped near stoichiometric lithium niobate (SLN:Fe,Zn) single crystals were grown by the top seeded solution growth technique from Li-rich flux. The Raman scattering analysis confirmed the near stoichiometric composition (Li/Nb∼0.98) whereas the birefringence interferometry revealed the optical homogeneity to be better than 5.2×10−5/mm for the grown crystals. Two beam coupling measurements showed the writing time constant to be 26–3.6 s measured in the intensity range 0.5–6 W/cm2. The slow and fast erasure time constants as obtained from bi-exponential fit are ∼22–4 and ∼200–24 s, respectively. Interestingly, the fast eraser time is found to be nearly the same as the writing time. The improvement in photorefractive sensitivity (∼0.16 cm/J) has been observed. The light induced changes in the refractive index (Δn∼5.8×10−5) are found to be in agreement with the estimated value. The intensity dependent photoconductivity estimated from the two beam coupling experiment is found to vary from 1.12×10–11 Ω−1 m−1 to 6.20×10−11 Ω−1 m−1 due to primary defects and from 1.24×10−12 Ω−1 m−1 to 1.04×10−11 Ω−1 m−1 due to secondary defects.

► Single crystals of Fe and Zn co-doped near stoichiometric lithium niobate are grown. ► Optical homogeneity issue is discussed. ► Photorefractive studies are carried out at moderate intensity (0.5–6.0 W/cm2). ► Improvement in response time and sensitivity is observed. ► Photoconductivity as evaluated by the holographic technique is in agreement with the literature value.