Abstract-Broadband and polarization insensitive design of terahertz absorber with high-index contrast grating on SOI chip

Sheenu Jindal, 

Mukesh Kumar

http://link.springer.com/article/10.1007/s11082-014-0026-9

Simple design of a broadband terahertz absorber consisting of a high-index contrast grating (HCG) on a silicon-on-insulator chip is proposed. Large absorption (98.4 %) over a wavelength range of 66–84 μmis obtained for normal incidence with large fabrication tolerance (14μmgrating period tolerance for grating height of2.6μm). The absorption remains high (∼98 %) for wide range of angle of incidence from0∘(normal incidence) to60∘. The bandwidth of high absorption (∼98 %) is also large i.e.40μmover a wide range of angle of incidence from0∘to60∘. The proposed broadband terahertz absorber also exhibits the design flexibility for the realization of polarization insensitivity with respect to the incident light of arbitrary polarizations. The proposed structure is easy-to-fabricate with a large fabrication tolerance which may provide a desirable broadband absorption for practical applications in terahertz devices. The proposed absorber is designed using rigorous coupled wave analysis and the results are in good agreement (with a maximum difference of 0.6 % in absorption) with those obtained with finite difference time domain method. The proposed characteristics of the device arise from the wavelength scalability and broadband nature of the HCG.