Impedance Matching of THz Plasmonic Antennas

Terahertz Antenna Impedance Matched to a Graphene Photodetector

“…The second resonance frequency for both dipole and patch occur at 610 and 625 GHz, respectively, merging with the first antenna resonance, although it is possible to tune the second resonance frequency by changing the complex impedance of the graphene load. 25 FEM simulations were conducted in parallel to confirm the equivalent circuit model. The absorbed power density in the BLG is computed (Figure 2b) at a wide frequency range where we extract the antenna enhancement factor at the nanogap.…”

“…The coupling capacitors C C represent the capacitive coupling between the antenna’s arm and the BLG and are modeled as an additional sheet inductor. The source of the two circuits is defined by the open-circuit voltage source V A , which is equal to the projection of the incident field intensity E 0 in V/m to the length of the antenna L A ( V A = E 0 × L A ). From the equivalent circuit in Figure c, we define an expression of the field enhancement at the nanogap | E g a p | 2 / | E 0 false| 2 = true( l normalA d normalg normala normalp true) 2 false| Z normalg normala normalp Z normalg normala normalp + Z normalA false| 2 , where the enhancement is proportional to 1/ d 2 .…”

“…This is shown in Figure a,b where the maximum gap field intensity is correlated to the maximum input resistance. The second resonance frequency for both dipole and patch occur at 610 and 625 GHz, respectively, merging with the first antenna resonance, although it is possible to tune the second resonance frequency by changing the complex impedance of the graphene load . FEM simulations were conducted in parallel to confirm the equivalent circuit model.…”

“…Design and Simulations. To optimize the impedance matching for f = 600 GHz, we build a lumped element model 25 to calculate the input impedance of the THz antenna and estimate the maximum absorbed power in the BLG based on finite element method (FEM) simulations. The model presented in Figure 1c resembles the shape of the real dipole antenna.…”

“…Increasing the T e gradient through enhanced optical absorption can locally augment heat absorption in the BLG . This enhancement was facilitated by integrating sub-wavelength nanogap confinement and boosting the near-field light–matter interaction, previously demonstrated to elevate responsivity. ,− Notably, double-struckR is inversely proportional to the thermal conductance ( G th ); thus, a low G th is critical for high sensitivity in THz detection. While epitaxial single-layer graphene (SLG) has shown G th ≃ 10 4 W/K·m 2 at 6K, significantly lower than SLG on SiO 2 , our quasi-free-standing BLG could potentially exhibit similar or even lower G th .…”