Substrate-strain-induced tunability of dense wavelength-division multiplexing thin-film filters.

Classic dense wavelength-division multiplexing thin-film filters can be spectrally tuned through the substrate's strain. We analyze the theoretical shift of the design wavelength of a narrow-bandpass filter when uniform, uniaxial compressive stress is applied to the substrate, and we compare calculated sensitivity with experimental data. We measure the transmittance shape of a 200-GHz standard filter for several loading cases to quantify the increase of insertion losses.

Toward tunable thin-film filters for wavelength division multiplexing applications.

We provide a detailed analysis of the various problems connected with the development of tunable thin-film filters for wavelength-division multiplexing applications. We examine the relation between the change in layer thickness and the central wavelength shift for various configurations and point out the significance of the structure of the reflectors, the spacer thickness, and the location of the active layers. We describe and compare practical arrangements using either temperature or an electric field as the driving parameter.

Piezoelectric tantalum pentoxide studied for optical tunable applications.

Piezoelectric transparent thin films are of great interest for use in tunable filters. We present experimental results on Ta2O5 single layers coated on fused-silica substrates with an electron-beam deposition process. Above 450 degrees C, coatings change from an amorphous to a polycrystallized structure.