Stable operation of a laser diode directly coupled to a LiNbO3 chip using optical isolation by orthogonal polarization

Stable operation of a semiconductor laser diode butt coupled to a LiNbO3 strip waveguide has been demonstrated with a coupling efficiency of 11%. At 6% coupling efficiency the laser was in addition continuously tunable over several GHz without hopping in external cavity modes. The far end isolation was achieved by a waveguide polarization controller operated as compensator using the generalized quarter wave plate isolation principle. The experimental setup however showed strong sensitivity to mechanical vibrations primarily due to the unreduced front reflection. With a modified coupling arrangement however this on chip isolation principle could be used for the local oscillator isolation in an integrated optic heterodyne/homodyne receiver even for a hybrid device.