Three-photon-induced four-photon absorption and nonlinear refraction in ZnO quantum dots.
Three-photon-induced four-photon absorption via excited-state absorption and self-defocusing nonlinear refraction are reported for the first time, to our knowledge, in ZnO quantum dots with average sizes of 2.0+/-0.1 nm with 1064 nm radiation from a Q-switched Nd:YAG laser at a peak intensity of 2.5 GW/cm(2). By employing the three-level two-step model, the experimental results can be explained quite satisfactorily.
Chattopadhyay
M
M
1Department of Physics, National Institute of Technology, Durgapur 713209, India.
Kumbhakar
P
P
Tiwary
C S
CS
Mitra
A K
AK
Chatterjee
U
U
Kobayashi
T
T