# Multilayer Bolometric Structures for Efficient Wideband Communication Signal Reception
## 3 Experimental Setup and Measurements; Results and Discussion
### Results and Discussion
At this point, the analogy with the splitting of levels in a double-well potential in quantum mechanics is worth mentioning. Despite the fact that in the situation considered below, there is no barrier structure (the real part of the dielectric permittivity for all layers, including the doped ones, turns out to be positive), an analogue of sub-barrier tunnelling is attenuation associated with signal absorption. In quantum mechanics, tunnelling determines the coupling of wells and, hence, the splitting of planes. In our case, the process of field penetration from the right to the left dielectric plate is responsible for the \"coupling\" in the heterostructure. This fact partially explains the difference in the formation of absorption zones when the order of the absorbing layers is changed. Figure 3: (**a**) Experimental (dots) and theoretical (curves) data on the absorbed GHz radiation normalized to the incident radiation flux measured at the output of the waveguide in the presence of a resonant structure (4) versus the linear signal frequency. (**b**) The field modulus distribution along the waveguide for the resonant frequency \(f=3.93\) GHz. The electric field strength is normalized to the amplitude of the incoming wave. Thus, the optimal configuration of periodic heterostructures for realizing efficient signal absorption is primarily determined by the characteristics of the incident radiation. For detecting a quasimonochromatic signal, it is reasonable to use a two-layer structure of type (3), where the absorption is concentrated in a single conducting layer. The multilayer structure can be used to detect broadband signals, but in this case, the doping levels of the conducting layers should be lower than in the case of a two-layer structure. This will ensure that a sufficient fraction of the signal penetrates into the layers far from the incident radiation, resulting in the formation of a wide absorption zone. It should be noted that due to the greater number of signal re-reflections from the conductive layers, the total fraction of absorbed signal may be smaller than in the two-layer structure. Figure 4: (**a**) Experimental and theoretical data of the absorbed GHz radiation normalized to the incident radiation flux measured at the output of the waveguide in the presence of the double resonant structure “semiconductor + single dielectric” versus the linear signal frequency. The resonant absorption peaks are split into two sub-peaks. The splitting of the peak with the position close to 6 GHz is not pronounced due to the appearance of the multimode waveguide regime. (**b**) The field modulus distribution along the waveguide for \(f=3.4\) GHz (the first sub-peak, green curve) and \(f=4.2\) GHz (the second sub-peak, blue curve). The electric field strength is normalized to the amplitude of the incoming wave. Our experimental and theoretical data have shown that using the proposed anti-reflection coating increases the signal absorption efficiency in the bolometer's conductive layer. Multilayer structures with finite thicknesses can work similarly on the nanometer scale as microscale heterostructures when the dielectric constant and thickness of the outside layer are tuned appropriately. Bolometers with a Josephson nanostructure integrated into the waveguide are used to detect radiation with record sensitivity at a frequency of several GHz [39; 40]. By covering such a structure with our anti-reflection coating, we can improve the efficiency of such a Josephson detector. The whole device can be made compactly, similarly to applying an anti-reflection coating for silicon optics at terahertz frequencies [56; 57; 58]. Our waveguide seamlessly fits into standard microwave setups for measurements involving superconducting resonators, qubits, and parametric amplifiers [59; 60]. In this configuration, the microwave generator is the source of microwave photons. At the same time, a vector network analyzer functions both as a generator and detector of the probe signal (see Figure 5a).