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CNR vs readout power for a ROM disk sample with as the SR material; ROM pits of 75 nm long were read with 405 nm/0.85 NA optics and at the linear velocity of 5 m/s.
TEM microstuctures of thin film on a grooved disk due to cw laser irradiation of various powers at the readout conditions in Fig. 1.
CNR values measured at 0.5 mW during alternating writing (at 2.1 mW)/erasing (at 1.5 mW) cycle of a periodic recording pattern consisting of a mark and a space in a single track of a grooved disk sample with ; corresponds to 1050 nm at the linear velocity of 5 m/s. Also shown are rf waveforms taken from a written and an erased state, respectively. These results clearly indicate that the amorphous bands in Fig. 2 are due to melt quenching of the material.
Schematic illustrations of SR readout at above the melting power. (a) Classical case: a closed aperture consisting of a melt pool inside a crystalline background serves to produce an SR signal from the difference in optical constants between the two structural states: melt and crystal. (b) Present case: an amorphous band including a melt pool forms behind a moving laser spot wherein a nonlinear optical effect, similar in nature to but stronger than the one in the surrounding crystalline solid, is presumed to work for an enhanced SR signal; a portion of the amorphous band might be recrystallized as represented by a dashed line.
Variation in changes in transmittance , reflectance , and normalized absorption coefficient of the crystalline with pumping laser power. Note that the transmittance increases, reflectance decreases, and absorption decreases with increasing laser power, which, as in the red light case of a previous study (see Ref. 10), may be accounted for by a solid state, nonlinear optical effect, namely, thermally assisted saturable absorption.
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