Search

Optical absorbers have been a topic of intense research due to their importance in many applications. In particular, multi-band and perfect absorption features in a desired frequency range are essential in broadband applications. In this work, we numerically studied the absorption properties of subwavelength metallic gratings coated with a dielectric layer. Here, the structure is considered to be an integration between a resonant cavity and a subwavelength metallic grating. Two appropriately designed structures can exhibit multi-band absorption properties. In addition to the numerical simulation results, we elaborate on determining the appropriate structural parameters that yield the desired spectral absorption profile in the visible range. We also numerically identify critical coupling conditions for perfect absorption. [ABSTRACT FROM AUTHOR]

Optical absorbers have been a topic of intense research due to their importance in many applications. In particular, multi-band and perfect absorption features in a desired frequency range are essential in broadband applications. In this work, we numerically studied the absorption properties of subwavelength metallic gratings coated with a dielectric layer. Here, the structure is considered to be an integration between a resonant cavity and a subwavelength metallic grating. Two appropriately designed structures can exhibit multi-band absorption properties. In addition to the numerical simulation results, we elaborate on determining the appropriate structural parameters that yield the desired spectral absorption profile in the visible range. We also numerically identify critical coupling conditions for perfect absorption.

Abstract: Inverse polarization transmission of light, with the TE transmittance η TE largely exceeding the TM transmittance η TM, through subwavelength metallic gratings at certain wavelength in deep ultraviolet band is theoretically investigated. By using the Fourier modal method and the planar waveguide theory, we show that the light transmission involves both the surface plasmon and the low-loss waveguide modes. Strong coupling of the incident wave to surface plasmon polariton results in the minimum in TM transmittance, whereas the coupling to the low-loss mode leads to the TE transmittance maximum. The established physical mechanism is sufficient to explain the inverse polarizing phenomenon observed in aluminum grating at the wavelength of 193nm, which may lead to important applications such as effective and compact polarizer used in DUV lithography. [Copyright &y& Elsevier]

Abstract: A high performance sub-wavelength metallic grating coupled surface plasmon resonance (SWMGCSPR) sensor with metal and porous composite layer is proposed. Rigorous coupled-wave analysis (RCWA) is conducted to prove the design feasibility, characterize the sensor's performance and determine geometric parameters of the structure, which is also employed to compute the electromagnetic (EM) field distributions at the resonant wavelengths. Parameters of sensing platform are optimized to achieve the best performance of the SPR sensor. Obtained results reveal that the proposed structure can excite SPR with negative diffraction order of SWMG. Both wavelength and angular sensitivities are greatly enhanced because surface plasmon wave (SPW) exhibits a large penetration depth which will enlarge the distance of interactions between SP and analytes. The detection sensitivities and quality parameters are estimated to be 700nm/RIU and 509°/RIU with full width at half maximum (FWHM) less than 2.5nm using the same optimized structure. [Copyright &y& Elsevier]

Abstract: In this paper, we present the nanofabrication of a potentially coupled waveguide–surface plasmon resonance biosensor (CWSPRBs) by nanoimprint lithography. Subwavelength metallic gratings (SWMGs) with the pitches of 300 and 500nm were fabricated by direct imprinting on PMMA layer which subsequently covered with a layer of Au. The key issue in this device is the coupling of surface plasmon with waveguide modes, which has been carefully investigated by measuring the coupling induced enhancement of light transmission. Both our measurement and simulation results indicate that the resonant coupling does exist for both 300 and 500nm pitched gratings. This proves that the developed nanoimprint lithography is applicable for the CWSPRBs sensors which has significant advantages over traditional ones with a prism. [Copyright &y& Elsevier]