Abstract
Photonic devices that can guide, transfer or modulate light are highly desired in electronics and integrated silicon photonics. Through the nonlinear processes taking place during ultrafast laser-material interaction, laser light can impart permanent refractive index change in the bulk of materials, and thus enables the fabrication of different optical elements inside the material. However, due to strong multi-photon absorption of Si resulting delocalization of the light by free carriers induced plasma defocusing, the subsurface Si modification with femtosecond laser was not realized so far [1, 2]. Here, we demonstrate optical waveguides written deep inside silicon with a 1.5-µm high repetition rate femtosecond laser. Due to pulse-to-pulse heat accumulation for high repetition rate laser, additional thermal lensing prevents delocalization of the light around focal point, allowing the modification. The laser with 2-µJ pulse energy, 350-fs pulse width, operating at 250 kHz focused in Si produces permanent modifications. The position of the focal point inside of the sample is accurately controlled with pump-probe imaging during processing. Optical waveguides of ~20-µm diameter, and up to 5.5-mm elongation are fabricated by translating the beam focal position along the optical axis. The waveguides are characterized with a 1.5-µm continuous-wave laser, through optical shadow-graphy (Fig. 1 a-b, e) and direct light coupling (Fig.1 c-d, f). The measured refractive index change obtained by quantitative shadow-graphy is ~6×10−4. The numerical aperture of the waveguide measured from decoupled light is 0.05.
© 2017 IEEE
PDF ArticleMore Like This
Ahmet Turnali, Onur Tokel, Denizhan Koray Kesim, Ghaith Makey, Parviz Elahi, and Fatih Ömer Ilday
CM_P_2 The European Conference on Lasers and Electro-Optics (CLEO/Europe) 2017
Maxime Chambonneau, Helena Kämmer, Gabor Matthäus, Kilian Pollok, Markus Blothe, Falko Langenhorst, and Stefan Nolte
cm_2_3 The European Conference on Lasers and Electro-Optics (CLEO/Europe) 2019
Namig Alasgarzade, Alessandro Alberucci, Markus Blothe, Maxime Chambonneau, Chandroth P. Jisha, and Stefan Nolte
STh4N.2 CLEO: Science and Innovations (CLEO:S&I) 2023