Design of non-polarization angle-tuned narrowband thin film filter

Design and feasibility of thermally tuned thin film filters for NG-PON2 system applications

“…Epoxy [11] Si [12,13] a-Si-H [6], [14] a-Ge [10], [12], [15] a-Si x N y -H [6], [16] These aims were pursued by using the following design methodology. Providing sufficient contrast between high (H) and low (L) layer refractive indices is essential for narrow bandwidth TFF design and high maximum spectral isolation.…”

“…Such is the case with D1 compared to D2. Additionally, deviation from normal incidence leads to the transmission peak shift towards shorter wavelengths and may introduce considerable PDL due to the central wavelength separation [15]. These design aspects will be addressed in the following section, as they showcase the importance of scenario specific trade-off in TFF material selection.…”

“…Cost and complexity aspects associated with large-volume manufacturing of mechanically tuned TFFs is another potentially deleterious factor. Additionally, polarization dependent loss (PDL) is typically an issue in angle tuned TFFs [15], and may significantly affect the overall system Thermo-optical tunability is an alternative approach, however, the following requirements ought to be accounted for: i) spectral tuning of at least 300 GHz (for 4 channels NG-PON2 use case); ii) tuning time compliant with NG-PON2 standards for thermally actuated devices -class 3 (from 25 ms to 1 s); and iii) targeting energy efficiency. Typically, thermally actuated devices underperform in terms of energy efficiency when compared with electrostatically driven ones.…”