Omnidirectional color filters capitalizing on a nano-resonator of Ag-TiO2-Ag integrated with a phase compensating dielectric overlay

Abstract

We present a highly efficient omnidirectional color filter that takes advantage of an Ag-TiO2-Ag nano-resonator integrated with a phase-compensating TiO2 overlay. The dielectric overlay substantially improves the angular sensitivity by appropriately compensating for the phase pertaining to the structure and suppresses unwanted optical reflection so as to elevate the transmission efficiency. The filter is thoroughly designed, and it is analyzed in terms of its reflection, optical admittance, and phase shift, thereby highlighting the origin of the omnidirectional resonance leading to angle-invariant characteristics. The polarization dependence of the filter is explored, specifically with respect to the incident angle, by performing experiments as well as by providing the relevant theoretical explanation. We could succeed in demonstrating the omnidirectional resonance for the incident angles ranging to up to 70°, over which the center wavelength is shifted by below 3.5% and the peak transmission efficiency is slightly degraded from 69%. The proposed filters incorporate a simple multi-layered structure and are expected to be utilized as tri-color pixels for applications that include image sensors and display devices. These devices are expected to allow good scalability, not requiring complex lithographic processes.

P‐127: Angle Insensitive Flexible Color Filter Electrodes

“…[5] The optical admittance is important in the CFEs because the color filtering function of the CFEs is operated by the light interference, which is deeply correlated to the optical admittance. [5], [6] When light comes to the CFEs obliquely, the optical admittances of the CFEs are changed as Y/cosθ and Y·cosθ for TM and TE waves, respectively (θ is the angle of incidence, as shown in Figure 3). [5] By using the TM wave, the color of the CFEs barely changed regardless of the angle of incidence because the optical admittance for the TM wave is negligibly changed with different angles of incidence, and this can be proved by simple optical calculations.…”

Uniformly thick tri-color filters capitalizing on an etalon with a nanostructured cavity

“…Therefore, it was confirmed that the proposed uniformly thick filters resorting to an etalon-type filter are concretely advantageous with respect to the angle-tolerant spectral response. In order to further improve the performance of the proposed filters, a thick metallic film may be possibly applied in conjunction with an antireflection coating, so as to simultaneously reduce the spectral bandwidth and enhance the reduced peak transmission caused by the increased metal thickness [20]. We may cautiously attempt a configuration of cascaded etalons, thereby diminishing the bandwidth [19].…”

“…For the proposed tri-color filters, the achieved performance was evaluated in terms of the transmission spectra as well as the dependence on the polarization and the angle of incidence, with and without considering the dispersion characteristics of Al 2 O 3 and TiO 2 [20]. As plotted in Fig.…”

“…In particular, an etalon having a metal-dielectric-metal configuration is regarded as a prime candidate for color filters on account of its conspicuous characteristics where the spectral passband can be tailored by simply varying the thickness of the dielectric cavity. However, in order to build a suite of filters exhibiting different passbands on the same platform, we evidently need to adopt different cavity thicknesses via additional fabrication steps [17][18][19][20][21]. It is imperative in terms of practical applications that tri-color filters, encompassing red, green, and blue (RGB), are produced such that they have a uniform thickness.…”

“…[1][2][3][4][5][6][7][8][9][10]. Inspired by color filtering in nature, several schemes of nanostructures, such as subwavelength grating structures exhibiting plasmonic and/or guided-mode resonances and Fabry-Perot (FP) etalons, have been extensively studied [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. In particular, an etalon having a metal-dielectric-metal configuration is regarded as a prime candidate for color filters on account of its conspicuous characteristics where the spectral passband can be tailored by simply varying the thickness of the dielectric cavity.…”