21 March 2005 Photonics in silicon using mid-IR femtosecond pulses
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Integrated optics in silicon is interesting for various optoelectronic devices, since photonics and electronics could be realized together. However, to be compatible with the standard CMOS technology, optical waveguides which rely on structuring the silicon surface are inappropriate. An alternative solution is the direct structuring inside the bulk medium by using ultrashort laser pulses. In recent years true three-dimensional photonic structures have been fabricated inside crystals and various optical glasses with this technique. Here, we demonstrate the use of femtosecond laser pulses to directly inscribe optical waveguides into the bulk of crystalline silicon. Due to the bandgap of 1.1 eV of silicon, the 800 nm pulses of the typically used Ti:Sapphire lasers cannot penetrate into the silicon. Therefore, the wavelength was converted to 2.6 μm using an optical parametric amplifier and the pulses were then focused into the bulk silicon by a Schwarzschild reflective objective. This way the laser energy was deposited in the focal region by three-photon absorption. Waveguides have been produced by translating the sample at a constant velocity of 2 mm/min. The waveguides are single-mode at the telecommunication wavelengths of 1550 nm and 1300 nm. Propagation losses were found to be less than 1 dB/cm. This technique is inherently capable of generating three-dimensional structures below the surface of silicon and therefore offers the potential to have a common platform for photonics and electronics.
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Jonas Burghoff, Jonas Burghoff, Matthias Will, Matthias Will, Stefan Nolte, Stefan Nolte, Andreas Tunnermann, Andreas Tunnermann, Amir H. Nejadmalayeri, Amir H. Nejadmalayeri, Peter Robert Herman, Peter Robert Herman, } "Photonics in silicon using mid-IR femtosecond pulses", Proc. SPIE 5714, Commercial and Biomedical Applications of Ultrafast Lasers V, (21 March 2005); doi: 10.1117/12.594545; https://doi.org/10.1117/12.594545

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