Etched cladding tunable fiber Bragg grating filters integrated with Si V-grooves

Abstract

We describe a novel electrically tunable fiber Bragg grating (FBG) filter with a chemically etched cladding and an evaporated metal coating on one side of the fiber. Wavelength tuning ranges up to 2.5 nm with efficiencies greater than 8.5 nm/watt have been demonstrated along with modulation bandwidths up to 14 Hz. We have also demonstrated tuning efficiencies over 200nm/Watt for 30micrometers diameter etched cladding devices tuned under moderate vacuum conditions. Such tunable FBG filters have potential applications in dense wavelength division multiplexing (DWDM), optical signal processing, or in wavelength tunable fiber lasers. In our paper we investigate the tuning efficiency and modulation bandwidth of etched cladding FBGs integrated with Silicon V-grooves that utilize temperature tuning of the filter. By passing an electrical current through a thin metal coating deposited onto an etched cladding FBG, the temperature of the grating can be controlled to tune the spectral characteristics of the FBG. Additionally, to simplify the fabrication process, we evaporate the metal coating onto the etched FBG from only one side. This radially asymmetric metal coating is simpler to fabricate, since it does not require any mechanical fixture to rotate the fiber during metal deposition. The etched cladding FBG is placed in a Si V-groove that serves the multiple functions of holding the FBG during etching and evaporation, and also provides a simple and compact means for scaling up to arrays of tunable FBGs.