Specific property analysis of thin-film semiconductors for effective optical logical operations.

摘要

In this thesis, a straightforward laser modulation concept is discussed which has the potential to be employed in similar ways as microelectromechanical systems (MEMS) in optical switching. The concept is realized by crossing two laser lines in a semiconducting thin-film on a glass or flexible polymer substrate, i.e., by switching one of the beams, one achieves a clearly resolved (up to 30%) modulation of the other beam. In case of thin-film GaAs, response times in the picosecond range are possible, whereas ZnTe and CdS exhibits relatively slow but more resolved modulation. Both the transmission and reflection modes of the modulation under different conditions such as various intensities and laser energies were investigated. The experiments were carried out in steady state with continuous wave lasers and time resolved mode with short laser pulses in the order of nanoseconds. Furthermore, electro-optic hybridization possibilities of the modulation concept were also investigated, utilizing thin-film semiconductor as an active optical element. All the experiments have been carried out at ambient conditions with moderate laser powers on the order of 10 mW. Additional experiments were carried out with the intention to relate the concept to photo induced reversible macroscopic property changes in the material such as reflection coefficient and refractive index variations. Reflection spectra of the materials were measured with and without the influence of additional laser illumination. A clear reflectance change was observed in all of the material with a pronounced difference near its band gap.