0ptical Harmonic Generation in ZnS and Fe^<+++> Doped ZnS

概要

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The effect of energy levels on the second harmonic generation of light (SHG) has been one of the problems in nonlinear optics. Recently, Miller et al. have shown that no enhancement of SHG occurs in CdS as its band gap approaches the energy of the second harmonics (SH) of Nd^<+++> laser. We have examined a similar effect of SHG in ZnS (partly cubic) as a function of temperature using the ruby laser (RL) and the effect of impurity (Fe^<+++>) level whose energy (1.6eV) is near RL one (1.78eV). We also prcsent the results in CdS (hexagonal) and ADP for comparison. All measurements have been made by foussing the laser beam with f/2.9 lens. ZnS has the energy gap of about 3.7eV at room temperature, which approaches the energy of SH of RL (3.57eV) when temperature is raised to about 220℃ Experimental conditions and some resuits are listed in Table I. It is shown that ZnS (1) and ZnS (2) give the same result though the latter has about 2 orders of magnitude heavier doping. They give also 20 times larger output of SHG than CdS and ADP. These show that resonance effect in SHG exists for intrinsic absorption edge, but does not appreciably for Fe^<+++> level, because either the latter is off resonance to RL by 0.2eV or it is a recombination center and RL can not excite the valence electron to conduction band by two st s through Fe^<+++> level.
社団法人日本物理学会の論文
1964-06-05