Bound electronic and free carrier nonlinearities in Silicon nanocrystals at 1550nm.
We present a detailed investigation of the different processes responsible for the optical nonlinearities of silicon nanocrystals at 1550 nm. Through z-scan measurements, the bound-electronic and excited carrier contributions to the nonlinear refraction were measured in presence of two-photon absorption. A study of the nonlinear response at different excitation powers has permitted to determine the change in the refractive index per unit of photo-excited carrier density sigma(r) and the value of the real bound-electronic nonlinear refraction n(2be) as a function of the nanocrystals size. Moreover at high excitation power, a saturation of the nonlinear absorption was observed due to band-filling effects.
Spano
R
R
Nanoscience Laboratory, Dipartimento di Fisica, Università di Trento, Via Sommarive 14, I-38050 Povo-Trento,Italy. spano@science.unitn.it
Daldosso
N
N
Cazzanelli
M
M
Ferraioli
L
L
Tartara
L
L
Yu
J
J
Degiorgio
V
V
Giordana
E
E
Fedeli
J M
JM
Pavesi
L
L