Passive Q-switch modulators of plastic dye sheets ( Kodak 9850 cellulose acetate dye sheets), lithium fluoride crystals containing F 2 -color center ( LiF: F 2 -), chromium doped yttrium aluminum garnet crystals ( Cr 4+ :YAG), ionic color filter glass ( Schott RG1000 color filter glass) and the single crystal semiconductor wafers ( GaAs, Fe doped InP, Zn doped InP, S doped InP, etc.) have been investigated in our research. Especially in use those of the single crystal semiconductor wafer saturable absorbers, give us idea of developing the semiconductor substrate microchip lasers.