Trans-Reflective Color Filters Based on a Phase Compensated Etalon Enabling Adjustable Color Saturation

Trans-reflective color filters, which take advantage of a phase compensated etalon (silver-titania-silver-titania) based nano-resonator, have been demonstrated to feature a variable spectral bandwidth at a constant resonant wavelength. Such adjustment of the bandwidth is presumed to translate into flexible control of the color saturation for the transmissive and reflective output colors produced by the filters. The thickness of the metallic mirror is primarily altered to tailor the bandwidth, which however entails a phase shift associated with the etalon. As a result, the resonant wavelength is inevitably displaced. In order to mitigate this issue, we attempted to compensate for the induced phase shift by introducing a dielectric functional layer on top of the etalon. The phase compensation mediated by the functional layer was meticulously investigated in terms of the thickness of the metallic mirror, from the perspective of the resonance condition. The proposed color filters were capable of providing additive colors of blue, green, and red for the transmission mode while exhibiting subtractive colors of yellow, magenta, and cyan for the reflection mode. The corresponding color saturation was estimated to be efficiently adjusted both in transmission and reflection.