@inproceedings{3137743,
    title = "Waferbonded active/passive vertically coupled microring lasers",
    author = "Hamacher, M. and Heidrich, H. and Troppenz, U. and Syvridis, D. and and Alexandropoulos, D. and Mikroulis, S. and Kapsalis, A. and Tee, C. W. and and Williams, K. and Dragoi, V. and Alexe, M. and Cristea, D. and Kusko, and M.",
    year = "2008",
    publisher = "SPIE - INT SOC OPTICAL ENGINEERING",
    booktitle = "INTEGRATED OPTICS: DEVICES, MATERIALS, AND TECHNOLOGIES XII",
    doi = "10.1117/12.762507",
    keywords = "InP; photonic integration; vertical coupler; wafer bonding; ring laser",
    abstract = "We summarize the results of a European Project entitled WAPITI
(Waferbonding and Active Passive Integration Technology and
Implementation) dealing with the fabrication and investigation of
active/passive vertically coupled ring resonators, wafer bonded on GaAs,
and based on full wafer technology. The concept allows for the
integration of an active ring laser vertically coupled to a transparent
bus waveguide. All necessary layers are grown in a single epitaxial run
so that the critical coupling gap can be precisely controlled with the
high degree of accuracy of epitaxial growth.
One key challenge of the project was to establish a reliable wafer
bonding technique using BCB as an intermediate layer. In intensive tests
we investigated and quantified the effect of unavoidable shrinkage of
the BCB on the overall device performance. Results on cw-operation, low
threshold currents of about 8 mA, high side-mode suppression ratios in
the range of 40 dB and large signal modulation bandwidths of up to 5 GHz
for a radius of 40 pin shows the viability of the integration process."
}