Enhancement of ultrafast nonlinear optical response of silicon nanocrystals by boron-doping

Nonlinear optical responses of boron (B)-doped silicon nanocrystals (Si-ncs) embedded in borosilicate glass were studied by z-scan and optical Kerr gate methods under femtosecond excitation at 780 nm. The nonlinear refractive index (n(2)) and the two photon absorption coefficients (β) of B-doped Si-ncs were found to be 3 times enhanced, compared to those of intrinsic Si-ncs. The response time was faster than 100 fs even at 5 K. The origin of the large nonlinear optical response was discussed, based on the experimental data of n(2), electron spin resonance spectra, and linear absorption spectra.