Birefringence compensation, improved fringe contrast and trimming in an integrated asymmetric Mach-Zehnder interferometer using mid-IR laser processing

Tuning of an asymmetric Mach-Zehnder interferometer using mid-IR laser radi ation is demonstrated. The device birefringence is compensated for by proce ssing at the surface above one of the arms with 10.6 mu m light from a CO2 laser. The spectral contrast of the component is improved from similar to 7 to similar to 12 dB for the TE and TM eigenstates, respectively to similar to 20 dB for both eigenstates by balancing the optical energy in each arm before the output coupler. (C) 2000 Elsevier Science B.V. All rights reserv ed.