This paper presents a detailed comparison between the long wave infrared (LWIR) transmission performances of binary, silicon based, structurally complementary pillar and groove type antireflective gratings that can be used for wafer level vacuum packaging (WLVP) of uncooled microbolometer detectors. Both pillar and groove type gratings are designed with various topological configurations changing in various period sizes (Λ) from 1.0 μm to 2.0 μm, various heights/depths (h) from 0.8 μm to 1.8 μm, and various pillar/groove width-to-period (w/Λ) ratios from 0.6 to 1.0. The transmission performance of gratings is simulated with a hybrid simulation technique based on the modification of the reflection term within the Fresnel transmission equation, which combines both numerical and analytical approaches in a unique way for the first time in literature. Simulation results are experimentally verified with 19 different fabricated structures where a spectral agreement is achieved with an absolute root-mean-square (RMS) error less than 5.4% within the subwavelength (SW) regime, proving the effectiveness of the proposed hybrid technique. These results show first time in the literature that both pillar and groove type silicon based gratings present similar spectral IR transmission characteristics, and they are also structurally complementary when optimum configurations are employed to maximize the transmission.

This paper presents a detailed analysis examining the absorption performance of a metal-dielectric slab with subwavelength size periodic perforations exploiting quarter-wave impedance matching (QWIM) technique within long wave infrared (LWIR) regime (8-12µm). Integration of perforations to a simple stack with various period sizes and perforated area ratios are examined through theory, simulation, and measurements that are in great agreement. Advantages of perforated absorbers for thermal detectors are discussed in maximizing optical absorption and reducing thermal-mass point of view. Introducing perforation in umbrella type absorbers is mainly employed for reducing the thermal-mass while maintaining the high absorption performance. Within the scope, it is experimentally shown that a perforation ratio (width/period) of 50% with square holes for the umbrella layer is possible without degrading the maximum LWIR absorption performance of 96% when the sheet resistance of Rs=400Ω/□ is employed for the absorbing metal layer, which is close to free space impedance of 377Ω/□. Nevertheless, this ratio can be increased up to 77% by depositing a thicker absorber metal with smaller sheet resistance, such as Rs=100Ω/□ while still maintaining an average absorption performance of 93%, which are all predicted numerically by simulations and physically explained through effective medium approach (EMA).

In this paper, an efficient method for the analysis of electromagnetic scattering/radiation from the obstacles nearby electrically large array antennas, with nonuniform excitation, is proposed. The approach is based on the combination of a ray field representation of electrically large arrays and a DFT (discrete fourier transform) based representation of array current distribution. Proposed method is applied to a 2D problem: radiation of a linear array of 2N+1 infinitely long current elements with tapered current distribution in the presence of an infinitely long PEC (perfect electric conductor) cylinder. Accuracy and efficiency of the method is discussed by numerical examples

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