Optica 5, 876–883 (2018)

Muhammad Rodlin Billah and co-workers from Germany have presented an efficient way to connect III–V light sources to passive silicon photonic circuits. Their approach, photonic wire-bonding, essentially relies on direct-write two-photon lithography to fabricate in situ three-dimensional freeform waveguides between optical chips for hybrid integration. Highly efficient coupling between indium phosphide -based horizontal-cavity surface-emitting lasers and photonic chips, through a three-dimensionally shaped photonic wire bond with a size of 2.0 μm × 1.4 μm, was achieved with coupling losses down to 0.4 dB. The bonds were fabricated from a commercially available negative-tone photoresist and can be adapted to the exact positions of the chips such that high-precision alignment of chips is not imperative, hence allowing automated processes for mass production.

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