Electronically controlled wavelength-tunable transmission filter based on metal grating incorporating polymer-dispersed liquid crystal

A novel narrow-band tunable transmission filter based on a sub-wavelength metallic grating incorporating polymer-dispersed liquid crystal (PDLC) with a tunable range of 47.2 nm is demonstrated. The transmission peak wavelength can be tuned from 1524.9 to 1572.1 nm when the refractive index of the PDLC layer is varied by different applying voltages. More than 95% transmission efficiency can be achieved at the resonant wavelength, while the -3 dB bandwidth is about 1.6 nm. In addition, the resonant wavelength of the filter varies in a linear fashion with regard to the refractive index of the PDLC layer. Hence, a desired resonant wavelength can be selected easily by controlling the applied voltage.