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An all-dielectric tunable optical filter based on the thermo-optic effect

2004; Springer Science+Business Media; Volume: 6; Issue: 6 Linguagem: Inglês

10.1088/1464-4258/6/6/002

1741-3567

Dennis Hohlfeld, Hans Zappe,

Photorefractive and Nonlinear Optics

A MEMS based, thermally tunable optical filter, hybridly assembled with a fibre based input/output, is presented. The filter is based on a Fabry?Perot interferometer employing a silicon cavity and silicon based dielectric Bragg reflectors and is fabricated as a free-standing membrane. The filter membrane is fixed to the substrate through micromachined suspension arms, which act as a thermal isolation. Wavelength tuning is achieved through thermal modulation of the cavity's optical thickness using thin film resistors. The filter characteristics measured were a full width at half-maximum value (FWHM) of 1.19?nm at a wavelength of 1530?nm and a finesse exceeding?1000. The tuning efficiency of a single-cavity filter with Bragg mirrors based on silicon nitride and silicon dioxide was measured to be 51.9?pm?K?1. Measurements of static and transient electrothermal behaviour were performed on filter membranes, resulting in maximum temperatures of 700??C and thermal time constants of 5.14?ms. The assembly technique relied on the alignment of optical fibres with the filter array using a novel silicon optical bench approach.