Transient enhancement of photorefractive gratings in lead germanate by homogeneous pyroelectric fields

During holographic recording in pure (Pb5Ge3O11) and doped [(Pb1-xBax)(5)Ge 3O11] lead germanate crystals, the diffraction efficiency is transiently en hanced at the initial stage. The enhancement is studied as a function of wr iting-beam intensity and of dark delay time between two successive recordin g processes and with open- or short-circuited crystal surfaces. Homogeneous pyroelectric fields that arise from heating of the crystals by cw illumina tion are revealed to be the main mechanism for diffraction efficiency enhan cement. The combined effect of pyroelectric fields and charge compensation is analyzed and used for the explanation of the observed phenomena. (C) 199 9 Optical Society of America [S0740-3224(99)00103-4] OCIS code: 160.5320.