Near field and cavity effects on coupling efficiency of one-dimensional metal grating for terahertz quantum well photodetectors

Abstract

The Modal Method is employed to simulate the coupling between the terahertz wave and onedimensional (1D) transmissive metal grating on the top of terahertz quantum well photodetectors (THzQWPs). Electrical field patterns and behaviors of 1D grating at different frequencies and device thicknesses are systematically studied. The results show that, the coupling efficiency is not only determined by the grating parameters, multiple reflections in the device and the subsequent multiple diffractions at the grating also play an important role. Different diffracted modes interact with each other, and near field effect caused by the evanescent waves are essential in evaluating the coupling efficiency especially when the frequencies are below the cutoff of the gratings. The optimization conditions of the performance of 1D metal grating coupled THzQWPs are also discussed.

Highly efficient metallic optical incouplers for quantum well infrared photodetectors

“…For QWIPs devices, the photocurrent is proportional to the averaged | E z | 2 across the whole QWs active region 39 . Therefore, in order to define the performance of the QWIPs based on specific architecture, commonly the couple efficiency η is defined as:…”

Strong Terahertz Absorption of Monolayer Graphene Embedded into a Microcavity

“…The propagation of diffractive modes in the multi-layer planar structure is treated with a recursive scattering matrix method. In the FEM-and the MM-based simulations, the dielectric constant of Au strips is calculated using the Drude model with the circular plasma frequency of 1.11 × 10 16 Hz and the free electron scattering rate of 8.33 × 10 13 Hz [39], and the dielectric constant of the two benzocyclobutene (BCB, Dow Chemical Company, Midland, MI, USA) layers is taken as a constant of 2.65-0.0008i in the whole considered frequency region [40]. frequency of 1.11 × 10 16 Hz and the free electron scattering rate of 8.33 × 10 13 Hz [39], and the dielectric constant of the two benzocyclobutene (BCB, Dow Chemical Company, Midland, MI, USA) layers is taken as a constant of 2.65-0.0008i in the whole considered frequency region [40].…”

“…The propagation of diffractive modes in the multi-layer planar structure is treated with a recursive scattering matrix method. In the FEM- and the MM-based simulations, the dielectric constant of Au strips is calculated using the Drude model with the circular plasma frequency of 1.11 × 10 16 Hz and the free electron scattering rate of 8.33 × 10 13 Hz [ 39 ], and the dielectric constant of the two benzocyclobutene (BCB, Dow Chemical Company, Midland, MI, USA) layers is taken as a constant of 2.65–0.0008 i in the whole considered frequency region [ 40 ].…”

Theoretical Investigation on Microcavity Coupler for Terahertz Quantum-Well Infrared Photodetectors

“…Au is used to construct the metal strip of grating and the bottom mirror. The permittivity of Au is described by the Drude model with the plasma angular frequency of 1.11×10 16 Hz and the scattering rate of 8.33×10 13 Hz [40]. The meshing parameters and the air thickness above the grating are verified to assure the accuracy of numerical results.…”