Second harmonic generation in selenium-metal structures

Results of second harmonic (SH) generation in amorphous and crystalline selenium films and selenium-metal (Ga, Zn, In, Sb, Bi) sandwich structures induced by titan-sapphire femtosecond laser (wavelength λ – 690–1040 nm) are presented. It is found that the highest intensity of SH is provided by fundamental wave at wavelength 1000 nm and it reaches maximum in approximately 100 s. The intensity of transmitted SH depends on film thickness while that of reflected does not. The highest SH intensities in selenium-metal structures are provided by Se–Ga and Se–Zn films. A possible mechanism for central symmetry breaking in amorphous films also is proposed.