Optical Bistability at the Absorption Edge of Semiconductors

Sergei E. Esipov

Hans Joachim Eichler, Andreas Haase, A. Kummrow +6 more

Ternary II-VI semiconductors, like CdSxSe1-x or ZnxCd1-xS, were prepared by thermal evaporation of binary semiconductors from a double source. The influence of substrate temperature during thin film deposition and of thermal annealing in argon atmosphere on absorption edge steepness is studied. A high absorption edge steepness is advantageous to achieve large resonant optical nonlinearities, like absorption bistability and electronic nonlinearities. The position of the absorption edge can be tuned by choosing a proper film composition. Thermally induced optical bistability is demonstrated. Electronic nonlinearities are investigated in ns- and ps-pump-probe experiments. Fast bleaching with < 60 ps relaxation time is observed at the absorption edge. The maximum bleaching coefficient for CdS0.69Se0.31 films is 1.4 cm/kW at (lambda) equals 587 nm for pumping with (lambda) equals 377 nm. Annealing the films showed no effect on the relaxation time, but the bleaching coefficient was increased by a factor of five.

Stanley Desmond Smith, Brian S. Wherrett

David A. B. Miller

H. E. Schmidt, H. Haug, S. W. Koch

The creation of an electron-hole plasma in a semiconductor leads to a large band-gap shrinkage which can be used to obtain absorptive optical bistability caused by discontinuous jumps between states of weak band-tail absorption and states of strong band-edge absorption. These effects are described by rate equations for the photons and the free carriers. For CdS the calculated hysteresis phenomena are similar to the experimental results.

Li Wei, Shaowen Song, You‐Nian Wang