Design of retrodiffraction gratings for polarization-insensitive and polarization-sensitive characteristics by using the Taguchi method

Abstract

We present the design of retrodiffraction gratings that utilize total internal reflection (TIR) in a lamellar configuration to achieve high performance for both TE and TM polarized light and polarization-sensitive performance for gratings behaving as polarizer filters; the design was based on rigorous coupled wave analysis (RCWA) and the Taguchi method. The components can thus be fabricated from a single dielectric material and do not have to be coated with a metallic or dielectric film layer to enhance the reflectance. The effects of the structural and optical parameters of lamellar gratings were investigated, and the TIR gratings in a lamellar configuration were structurally and optically optimized in terms of the signal-to-noise ratio (S/N) and a statistical analysis of variance (ANOVA) of the refractive index, grating period, filling factor, and grating depth as control factors and the estimated efficiency by RCWA as a noise factor. For more accurate robustness, a two-step optimization process was used for each purpose. For TIR gratings designed to perform similarly for TE and TM incident polarization, the -1st-order efficiencies were estimated to be up to 92.0% and 88.5% for TE and TM polarization, respectively. Also, for the TIR gratings designed to achieve polarization-sensitive performance when behaving as a polarizer filters, the -1st-order diffraction efficiencies for TE and TM polarization were estimated to be up to 95.5% and 2.7%, respectively. From these analysis results, it was confirmed that the Taguchi method shows feasibility for an optimization approach to a technique for designing optical devices.

Total Internal Reflection-Based High Efficiency Grating Design for a Metal-Free Polarizing Filter Applications Using Hybrid Optimization Procedure

“…Based on the analysis results of / ratio and ANOVA of each parameter, the Taguchi method narrows down all sets of admissible space Ω to the quasi-admissible space Ψ, which provides the narrowed-down search region for GA. The three-level standard orthogonal arrays, 18 , were employed [4]. This two-step procedure allows saving the computation time to find the global minimum.…”

“…The pitch parameter was set from (1), and filling factor and depth were set in the whole space, Ω = { ( , , ) | 0.330 < [ m] < 0.534, 0.1 < < 0.9, 0.1 < [ m] < 1.0}. The effective set of parameters was coarsely optimized by the Taguchi method [4]. Based on the analysis results of / ratio and ANOVA of each parameter, set of the design parameters, (0.435, 0.5, 0.85), was obtained, and then, the narrowed-down quasi-admissible space Ψ = { ( , , ) | 0.4 < [ m] < 0.5, 0.3 < < 0.6, 0.8 < [ m] < 1.0} was subdivided for GA, respectively.…”

“…Diffraction gratings play an important role in many optical applications, including optical telecommunications components, spectroscopy, and the chirped pulse amplification (CPA) for a high power laser system [1][2][3][4]. Especially, diffraction gratings utilizing total internal reflection (TIR) within a metal-free groove are an environmentally friendly integrated optical element expected to achieve a high performance at a specific retrodiffracted order [1][2][3][4].…”

“…Especially, diffraction gratings utilizing total internal reflection (TIR) within a metal-free groove are an environmentally friendly integrated optical element expected to achieve a high performance at a specific retrodiffracted order [1][2][3][4]. Absorption of the incident light at the metallic surface diminishes diffraction efficiency (DE) to 75-95%, depending on the material and wavelength of the incident light, which can result in the severe damages on the grating facets because this absorbed energy turns into heat [3].…”

“…However, there was little work on the optimization of the TIR-based gratings. Lee et al demonstrated the parametric optimization to grating structures using the Taguchi method [4]. This approach provided the design concept for the TIR gratings but did not reach the global minimum, which means that its performance is still in short when it takes TIR into consideration.…”