Angled flip-chip integration of VCSELs on silicon photonic integrated circuits

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Caut, Alexander
Jahed, Mehdi
Goyvaerts, Jeroen
Rensing, Marc
Karlsson, Magnus
Larsson, Anders
Roelkens, Gunther
Baets, Roel
O'Brien, Peter
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Institute of Electrical and Electronics Engineers (IEEE)
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An investigation of angled flip-chip integration of a singlemode 850 nm vertical-cavity surface-emitting laser (VCSEL) on a silicon nitride photonic integrated circuit (PIC) is presented. Using numerical FDTD simulations, we consider the conditions under which the VCSEL can be integrated at an angle over a grating coupler with high coupling efficiency and low optical feedback. With both coupling efficiency and feedback decreasing with increasing angle, there is a trade-off. With co-directional coupling, first-order diffraction loss sets in at a critical angle, which further reduces the coupling efficiency. No such critical angle exists for contra-directional coupling. We also experimentally demonstrate angled flip-chip integration of GaAs-based 850 nm single transverse and polarization mode VCSELs over grating couplers on a silicon-nitride PIC. At the output grating coupler, light is either collected by an optical fiber or converted to a photocurrent using a flip-chip integrated GaAs-based photodetector. The latter forms an on-PIC optical link. We measured an insertion loss of 21.9, 17.6 and 20.1 dB with a singlemode fiber, multimode fiber and photodetector over the output grating coupler, respectively.
Coupling efficiency , Couplings , Diffraction , Diffraction gratings , Flip-chip integration , Gratings , Optical feedback , Optical waveguides , Silicon-nitride photonic integrated circuit , Vertical cavity surface emitting lasers
Caut, A., Jahed, M., Goyvaerts, J., Rensing, M., Karlsson, M., Larsson, A., Roelkens, G., Baets, R. and O'Brien, P. (2022) 'Angled flip-chip integration of VCSELs on silicon photonic integrated circuits', Journal of Lightwave Technology. doi: 10.1109/JLT.2022.3172781
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