Linear variable filter enabling an enhanced wavelength gradient based on shadow-mask sputtering

A linear variable filter (LVF) that improves the wavelength gradient is proposed, and a sample is manufactured using a radio frequency sputtering technique with the help of a vertical shadow mask, which simplifies the fabrication process. The LVF is based on a metal-dielectric-metal Fabry–Perot etalon, wherein the dielectric cavity is tapered in thickness along the device so that the resonance wavelength can be continuously tuned at various positions. The produced device shows a filtering range from 443 nm to 602 nm over a distance of 16 mm, which corresponds to a wavelength gradient of 10 nm/mm. The measured spectra exhibited, on average, a peak transmission of 39% and a spectral bandwidth of 46 nm.