photo conductivity
1.The dark-conductivity and photo-conductivity achieved for the poly-Si films are～10~(-4)Scm~(-1) and～10~(-3)Scm~(-1), respectively.
2.Particularly, Cr4+-doped crystals as passive Q-switch (saturable absorber ) have got extensive attention, such as Cr4+:YAG，Cr4+:GSGG，Cr4+:Mg2SiO4 and Cr4+:YSO, which have the advantages of wild absorption band, good saturable absorption, long restored time, good photo-chemical stability, no fading, good thermal conductivity and high damage threshold.
