Probing ultrafast carrier dynamics, nonlinear absorption and refraction in core–shell silicon nanowires

Pramana

M Khorasaninejad¹  A K Sood1²  S S Saini¹  M M Adachi¹  Sunil Kumar²  K S Karim¹ 

[1] Department of Electrical and Computer Engineering, University of Waterloo, Canada N2L 3G1$$;Department of Physics and Centre for Ultrafast Laser Applications, Indian Institute of Science, Bangalore 560 012, India$$

关键词: Silicon;    nanowires;    femtosecond;    ultrafast spectroscopy;    nonlinear optical coefficients.;   

DOI  :  

学科分类：物理（综合）

来源: Indian Academy of Sciences

【 摘 要 】

We investigate the relaxation dynamics of photogenerated carriers in silicon nanowires consisting of a crystalline core and a surrounding amorphous shell, using femtosecond time resolved differential reflectivity and transmission spectroscopy at 3.15 eV and 1.57 eV photon energies. The complex behaviour of the differential transmission and reflectivity transients is the mixed contributions from the crystalline core and the amorphous silicon on the nanowire surface and the substrate where competing effects of state-filling and photoinduced absorption govern the carrier dynamics. Faster relaxation rates are observed on increasing the photogenerated carrier density. Independent experimental results on crystalline silicon-on-sapphire (SOS) help us in separating the contributions from the carrier dynamics in crystalline core and the amorphous regions in the nanowire samples. Further, single-beam z-scan nonlinear transmission experiments at 1.57 eV in both open- and close-aperture configurations yield two-photon absorption coefficient 𝛽 (∼3 cm/GW) and nonlinear refraction coefficient 𝛾 (−2.5 × 10−4 cm2 /GW).

【 授权许可】

Unknown