Direct Imaging of Multimode Interference in a Channel Waveguide
15 March 2003
Based on multimode interference imaging, couplers employing a wide multimode waveguiding region are commonly used to divide and combine light in photonic integrated circuits. Using a near-field scanning optical microscope in collection mode, multimode interference was directly observed in an annealed proton exchange LiNbO3 waveguide.
Periodic transitions from a single peaked Gaussian like intensity distribution to a doubled peaked intensity distribution are observed. Calculations of the intensity distributions based on the dimensions of the waveguide and the input mode agree with observed intensity distribution.