Villafranca Velasco, AitorBock, Przemek J.Cheben, PavelCalvo Padilla, María LuisaSchmid, Jens H.Lapointe, JeanXu, Dan-XiaJanz, SiegfriedDelâge, André2023-06-202023-06-202012-06-070013-519410.1049/el.2012.0591https://hdl.handle.net/20.500.14352/44170© The Institution of Engineering and Technology 2012. Financial support from the Spanish Ministry of Science and Innovation is acknowledged under grant TEC2008-04105.The fabrication and experimental characterisation of a two-stage bandpass filter based on curved waveguide sidewall gratings is reported for the silicon-on-insulator platform. At each cascaded filtering stage, the spectral components of the input signal are dispersed by the diffraction grating formed in the sidewall of a silicon strip waveguide. Different wavelengths are focused onto different positions along the Rowland circle and the filter central wavelength is selected by a specific receiver waveguide. By using two consecutive filtering stages, both the filter passband profile and the stopband rejection ratio are substantially increased. The grating is apodised and chirped to ensure a constant effective index along the grating length to minimise phase distortions. Blazed geometry is used to maximise the diffraction efficiency to the - 1st order. The device was fabricated with electron beam lithography and reactive ion etching using a single etch step. A bandwidth of 6.2 nm was measured near 1590 nm for the fabricated filter, with a roll-off of 4 dB/nm at the passband edge, and a stopband rejection of 40 dB.engjournal articlehttp://dx.doi.org/10.1049/el.2012.0591http://www.theiet.org/open access535EngineeringElectricalElectronicÓptica (Física)2209.19 Óptica Física