Second harmonic generation in selenium-metal structures

The article examines the processes of second harmonic generation (SHG) when selenium-metal (Cu) film structures are illuminated by femtosecond radiation (180 fs, 80 MHz) at wavelength 800 - 1000 nm. Selenium-copper structures were obtained by successive thermal evaporation of selenium and copper onto the glass substrate in vacuum. Microanalysis of the film composition was performed to determine amount of copper in thin films. The as-evaporated selenium-copper structures were crystallised by annealing in inert atmosphere at temperature 85°C. Just evaporated as well as annealed thin films were explored. The experiment was performed by confocal microscope [1] where the femtosecond radiation from laser was injected. A photosensitivity of structures in question was then determined as functions of intensity and wavelength of the incident radiation [2]. Second harmonic intensity dependence on thickness of Cu layer was also observed. We found out that adding small amount of Cu increases reflected SH intensity.