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      Permanent link:
      https://www.ias.ac.in/article/fulltext/pram/079/03/0471-0481

    • Keywords

       

      Silicon; nanowires; femtosecond; ultrafast spectroscopy; nonlinear optical coefficients.

    • Abstract

       

      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).

    • Author Affiliations

       

      Sunil Kumar1 M Khorasaninejad2 M M Adachi2 K S Karim2 S S Saini2 A K Sood1

      1. Department of Physics and Centre for Ultrafast Laser Applications, Indian Institute of Science, Bangalore 560 012, India
      2. Department of Electrical and Computer Engineering, University of Waterloo, Canada N2L 3G1
    • Dates

       
  • Pramana – Journal of Physics | News

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