Critical optical coupling between a GaAs disk and a nanowaveguide suspended on the chip

We report on an integrated GaAs disk/waveguide system. A millimeter-long waveguide is suspended and tapered on the chip over a length of 25 m to evanescently couple to high Q optical whispering gallery modes of a GaAs disk. The critical coupling regime is obtained both by varying the disk/guide gap distance and the width of the suspended nanoscale taper. Experimental results are in good agreement with predictions from coupled mode theory