Polarization independent tunable narrow-band 1.55 μm grating filter in photorefractive iron doped indium phosphide

Tunable selective optical filters are key components for wavelength division multiplexing (WDM) communications. Such optical filters can be used for demultiplexing and FSK-to-ASK (frequency-shift keying to amplitude-shift keying) conversion. A grating filter is a selective coupler which partially or totally extracts the selected channel wavelength and transmits the others. The tunability of such a filter is generally obtained via the piezoelectric effect or by the temperature control. The photorefractive (PR) effect allows dynamic index change. The response time depends on the material and on the intensity of the control light. In this paper, we report a tunable narrow-band optical reflective drop filter operating at 1.55 μm in bulk iron doped indium phosphide (InP:Fe)