Active optical lattice filters with nanophotonic four-port couplers

The first demonstration of an active optical lattice filter with nanophotonic 4-port couplers is reported. The experiments are in good agreement with a z-transform based filter theory. The filter response may be tuned by adjusting the gains of the active optical element of the filter, herein realized with semiconductor optical amplifiers. A key to the compact realization, and the device´s operation, is the use of novel four port nanophotonic couplers based on frustrated total internal reflectance.