An Omnidirectional Polarization Detector Based on a Metamaterial Absorber

The theory, design, simulation, fabrication, and performance of an omnidirectional polarization detector (PD) with two resonances located in the X and Ka ranges based on a metamaterial absorber (MMA) are presented in this paper. The sandwich structure of PD is composed of 0.1 μm periodic “I” shaped patches on the metasurface, a dielectric of 200 μm FR-4 on the interlayer, and a 0.3 μm copper film on the substrate. PD absorptivity is first used to reflect and describe the polarization of the incident wave. The numerical results, derived from the standard full wave finite integration technology (FIT) of CST 2015, indicates that the designed PD shows polarization sensitivity at all incidence angles. The effects on absorptivity produced by the incidence angles, polarization angles, and materials are investigated. The amplitude of absorptivity change caused by polarization reaches 99.802%. A laser ablation process is adopted to prepare the designed PD on a FR-4 board coated with copper on the double plane with a thickness that was 1/93 and 1/48 of wavelength at a resonance frequency of 16.055 GHz and 30.9 GHz, respectively. The sample test results verify the designed PD excellent detectability on the polarization of the incident waves. The proposed PD, which greatly enriches the applications of metamaterials in bolometers, thermal images, stealth materials, microstructure measurements, and electromagnetic devices, is easy to mass produce and market because of its strong detectability, ultrathin thickness, effective cost, and convenient process.


Introduction
Polarization is one of the significant characteristics of electromagnetic waves that plays a vital role in many domains, such as polarization imaging, confidential communications, heterodyne detection, titers, navigation, and quantum computers. However, the lack of convenient PD with high-performance limits the exploitation of polarization. Polarization analyzers based on conventional polarization detection methods, which include polarization interferometry or modulation detection [1,2], four probes distribution detection [3], and polarization amplitude detection [4], are difficult to adopt because of their complicated mechanical structure, and immense data processing. Electric vector, Jones vector, Stokes vector, and Poincare sphere, which are intricate and elusive, are usually adopted to describe the polarization of the incident waves [5,6]. Tong et al. attempted to utilize the polarization of electromagnetic waves to detect the gravitational waves [7]. The Laser Interferometer photomemory, bolometers, thermal imaging, microstructure measurements) because of its strong detectability, ultrathin thickness, low cost, and convenient manufacturing process.

Theoretical Analysis and Structure Design
When electromagnetic waves (such as light) traverse a metamaterial, the resonance of the electric and magnetic fields can activate the electrons in atoms or molecules. As a result, the transmission properties will be changed as the material consumes the energy of the electromagnetic waves. Natural materials comprise microatoms whose polarization and magnetization characteristics determine the material electromagnetic response. Complex permittivity ε pωq " ε 1`i ε 2 and complex permeability µ pωq " µ 1`i µ 2 are adopted to describe the acuteness degree of motion. ε 1 is a parameter that describes the degree of polarization, whereas µ 1 describes the degree of magnetization. ε 11 and µ 11 are the basic characterization parameters that describe the electromagnetic losses in a medium.
Electromagnetic waves with low frequency, that incide on the metasurface of the designed PD, will excite the electrons over a wide range and make the electrons absorb the most energy. The small induced currents in the corner of the "I" patches lead to a large R(ω). The movement range of electrons will gradually become smaller, and the induced currents in the corner will gradually become larger with the increase of the incident waves' frequency. When the frequency of the incident waves reaches a certain value, electrons in the two sides of "I" patches fleetly move back and forth with the actuation of electric field vector of the incidence waves. Then, the induced currents reach the maximum value. The incident electromagnetic waves are absolutely coupled into the dielectric layer at resonance points, and R(ω) approaches zero. When the incident wave frequency rises continually, the movement range of electrons will become smaller, the strong induced currents will be divided into several segments, so R(ω) will begin to increase. The metasurface of the proposed PD can serve as a frequency selective surface (FSS) with a band pass filter function.
For a sandwich structured PD that contains the metasurface, a dielectric layer, and a metal substrate, A pωq " 1´R pωq´T pωq " 1´|S 11 | 2´| S 21 | 2 can be applied to calculate the absorptivity. R pωq " |S 11 | 2 is reflectivity and T pωq " |S 21 | 2 is transmittivity. Precise control of n(ω) and the PD input impedance Z(ω) is necessary for realizing a high absorptivity. Electromagnetic metamaterials are prime candidates for this task because they can be designed to couple to electric and magnetic components of incident waves. This enables precise tuning of the complex, and frequency-dependent ε(ω) and µ(ω). The index n(ω) and the PD impedance Z(ω), which are determined by the metamaterial parameters and electromagnetic properties of the incoming waves, are preliminarily expressed as n pωq " a µ pωq ε pωq and Z pωq " a µ pωq {ε pωq, respectively. R(ω), which can by calculated from the formulation (1), is controlled by the incidence angle θ, the matching degree of Z(ω) and Z 0 .
rpRe tZ pωqu´Z 0 cosθqs 2`r Im tZ pωqus 2 rpRe tZ pωqu`Z 0 cosθqs 2`r Im tZ pωqus 2 where Z 0 " a µ 0 {ε 0 " 337 Ω is a constant that denotes the wave impedance of free space [25]. The effect of the surface resistance of the FSS and dielectric characteristics on the input impedance of the metamaterial is discussed by means of a circuital model. Z(ω) can be equivalent to a parallel connection between dielectric impedance Z d pΩq and FSS impedance Z f ss pΩq according to Equation (2): The expression of Z d with TE and TM polarization at oblique incidence well reads with the relation (3): where Z TE d0 " pωµµ 0 q {β, Z TM d0 " β{ pωµµ 0 q are the characteristic impedances of the dielectric for TE and TM polarization [26] 1´sin 2 pθq is the propagation constant and k t = k 0 sin(θ) is the transverse wavenumber. θ represents the incidence angle with respect to the vertical incidence. The real and the imaginary part of Z d can be well calculated from Equations (4) and (5), respectively: where h d represents the dielectric thickness. After some mathematical and analytical manipulations with the help of [27], Im{Z d } with TE and TM polarization at oblique incidence can be well approximated by the following relations: The formulas (6) and (7) show that the reactance of Im TE {Z d } is almost unchanged with the θ. However, the increase of θ leads to a decrease of Im TM {Z d }. The adoption of the dielectric with a higher ε 1 would increase the sensitivity of θ, however, a defective absorption would be obtained for very oblique incidence such as θ = 80˝. The perfect absorption with higher θ for TE polarization is instead more difficult to reach.
Z fss , which stands for the impedance of the lossy FSS, can be represented through a series RLC circuit, and it can be extracted from the following formulas: where p is the length of periodic array, l 1 and l 2 stand for the structure dimensions of a "I" patch. Z fss , as previously remarked in (8), is composed by three loss terms, an ohmic resistor, R o , a dielectric resistor, R d , and X [28]. The shape and size of FSS decide the values of L and C. It is shown that resonators with high capacitive elements, keeping ε unchanged, need a dielectric with higher losses to achieve perfect absorption, but they lead to the maximization of the full width at half maximum (FWHM). It is shown that the optimum value of Z fss is affected both by h d , ε, and, shape and size of resonator in FSS. The FSS with a small resonator filling factor are characterized by high ohmic losses due to high surface currents. A patch type configuration allows minimizing the ohmic losses and maximizing the dielectric ones, but as already pointed out, it requires a high tangent loss of the dielectric or an adequately thin dielectric to obtain strong resonance and perfect absorption. The adoption of abundant lumped resistors for introducing ohmic losses in the metasurface leads to complex and expensive structures because of the cost of high frequency resistors and complexity of the conventional soldering. An attractive alternative is printing the periodic metal patterns with a proper surface resistance. Synthesizing the above analysis, the input impedance can be expressed in detail as follows: where R = R 0 + R d . After some analytical manipulations [29], the real and the imaginary part of the input impedance Zω can be derived as the following formulas: The increase of the loss components in the dielectric causes a reduction of Re{Zω}. A reduced loss leads to the Re{Zω} being higher than the free space impedance while a too lossy dielectric would reduce the absorptivity since Re{Zω} becomes smaller than the free impedance. A moderate red shift of resonance frequency will occur with the increase of h d that leads to the increase of the dielectric inductance.
Reflectivity becomes zero when the PD reaches perfect impedance-matched (Z(ω) = Z 0 ), which can be achieved by designing appropriate microstructures and arrangements. The incident electromagnetic wave is absolutely coupled into the dielectric layer at resonance points. The middle dielectric layer is responsible for consuming electromagnetic energy. Positive transfer coefficient S 21 was determined to be dependent on the complex index of refraction n(ω) = n 1 + in 11 and the thickness of dielectric h d as relation (15): where k = ω/c and c is the speed of light in vacuum. Thus, transmissivity T(ω) = |S 21 | 2 = e´2 n 11 kh . The combined dielectric and magnetic losses in the system are characterized by n 11 and h. Therefore, when n 11 or h approaches infinity, T(ω) approaches zero [30]. The metal base guarantees that the incident wave does not cross the substrate when the thickness of metal substrate is greater than skin depth which results in transmittivity T pωq " |S 21 | 2 " 0 [31]. The arrangement and single resonator are depicted in Figure 1. The electric fields, which are parallel to the direction of the "I" shaped patch, oscillate the electrons bounded in an infinitely long straight wire and generate induced currents on the metasurface. Therefore, a portion of the incident waves' energy can be consumed by the oscillating electrons while the surplus energy penetrates the metasurface and diffuses continually. When the plane, where the wire is located, is rotated by 90 degrees while keeping the electromagnetic properties of the incident waves unchanged, absorption and consumption will decline dramatically. A full wave electromagnetic (EM) simulation is performed based on the standard finite integration technology (FIT) in CST Microwave Studio 2015. Periodic boundary conditions are used in the x and y directions, and the excitation source is a Floquet port with diverse incidence angles and polarizations. The project parameters are presented in Table 1. Thus, absorptivity can be calculated by utilizing the equation A pωq " 1´R pωq´T pωq " 1´|S 11 | 2´| S 21 | 2 .

Simulation Analysis
We first explored the connection between incident wave polarization and absorptivity with various incidence angles. The simulated results are shown in Figures 2-7. Figure 2 indicates that the transverse electromagnetic (TEM) waves with vertical incidence generate an absorptivity of 0.94679 at 36.9 GHz, which is the strongest resonance point. When the angle of incidence remains the same (θ = 0°), and the polarizing angle increases in 45° steps (φ = 0°, 45°, 90°), Figure 2 shows that the increased polarization angle of the transverse electric (TE) waves causes a decline of absorptivity peak in the high band and the appearance of an absorptivity peak at 16.055 GHz, which is located in the low band. In other words, the absorptivity peak is directly proportional to the polarization angle of the TE waves in the low band, whereas the proportion reverses in the high band. Figure 3 reveals the inverse of the proportional relationship between the absorptivity peak and the polarization angle when the incidence waves become transverse magnetic (TM) waves. The elaborative comparison of the two illustrations reveals that there is no shift of resonance points when the polarization state of the incidence waves changes. Figures 4 and 5 show that when the incidence angle is increased to 40° (θ = 40°), the proportionality relationship between the absorptivity peak and the polarization angle remains the same in both the high band and the low band for all polarization states. The comparison of Figures 4 and 2 reveals that the absorptivity peaks decline in the resonance points, except for the case of θ = 40°, φ = 0°. The contrast of Figures 5 and 3 shows that the decreased absorptivity peaks increase. In the case of TM, θ = 40°, φ = 45°, 90°, Figures 6 and 7 shows that a new resonance is detected near 41.4 GHz. Absorptivity decreases dramatically when θ is increased to 80° during the stimulation of TE waves, while TM waves exhibit stronger resonance and higher absorptivity. The new resonance point locates in 43.755 GHz during the stimulation of TE, θ = 80°, φ = 90°, whereas the TM waves cause two fresh resonances near 41.6 GHz and 43.5 GHz. The absorption properties and mechanism of the designed PD are further analyzed by demonstrating the electric fields distributions of the resonator surface in Figure 8. Strong resonance occurs in the corners of periodic "I" shaped patches.  1200 "I" dimension l 2 1000 "I" dimension l 3 1000 "I" dimension l 4 100 "I" dimension

Simulation Analysis
We first explored the connection between incident wave polarization and absorptivity with various incidence angles. The simulated results are shown in Figures 2-7. Figure 2 indicates that the transverse electromagnetic (TEM) waves with vertical incidence generate an absorptivity of 0.94679 at 36.9 GHz, which is the strongest resonance point. When the angle of incidence remains the same (θ = 0˝), and the polarizing angle increases in 45˝steps (φ = 0˝, 45˝, 90˝), Figure 2 shows that the increased polarization angle of the transverse electric (TE) waves causes a decline of absorptivity peak in the high band and the appearance of an absorptivity peak at 16.055 GHz, which is located in the low band. In other words, the absorptivity peak is directly proportional to the polarization angle of the TE waves in the low band, whereas the proportion reverses in the high band. Figure 3 reveals the inverse of the proportional relationship between the absorptivity peak and the polarization angle when the incidence waves become transverse magnetic (TM) waves. The elaborative comparison of the two illustrations reveals that there is no shift of resonance points when the polarization state of the incidence waves changes. Figures 4 and 5 show that when the incidence angle is increased to 40( θ = 40˝), the proportionality relationship between the absorptivity peak and the polarization angle remains the same in both the high band and the low band for all polarization states. The comparison of Figures 2 and 4 reveals that the absorptivity peaks decline in the resonance points, except for the case of θ = 40˝, φ = 0˝. The contrast of Figures 3 and 5 shows that the decreased absorptivity peaks increase. In the case of TM, θ = 40˝, φ = 45˝, 90˝, Figures 6 and 7 shows that a new resonance is detected near 41.4 GHz. Absorptivity decreases dramatically when θ is increased to 80˝during the stimulation of TE waves, while TM waves exhibit stronger resonance and higher absorptivity. The new resonance point locates in 43.755 GHz during the stimulation of TE, θ = 80˝, φ = 90˝, whereas the TM waves cause two fresh resonances near 41.6 GHz and 43.5 GHz. The absorption properties and mechanism of the designed PD are further analyzed by demonstrating the electric fields distributions of the resonator surface in Figure 8. Strong resonance occurs in the corners of periodic "I" shaped patches. In the case of θ = 40˝, φ = 0˝, the TE waves cause a powerful resonance at 36.9 GHz, whereas the TM waves cause a forceful resonance at 16.055 GHz. The polarization of the incident waves can be achieved from the analysis on the absorptivity of PD with the help of Table 2. Then, we investigate the effects on absorptivity produced by electromagnetic properties of the dielectric. Figure 9 shows the transformation of absorptivity and resonance points of PD when the middle dielectric is porcelain, FR-4, and polyimide with a permittivity of 5.7, 4.4, and 3.5, respectively. The image indicates that the increase of dielectric permittivity triggers a red shift of the resonance frequency, an increase of absorptivity in the high band, and a reduction of absorptivity in the low band. The relevance help concerned individuals to select a suitable dielectric to project the appropriate PD for special circumstances. Finally, in order to study the relationship between the conductivity of metallic material and the absorbing performance of PD, we defined the metal as gold, copper, and silver with conductivity of 4.5e7 S/m, 5.8e7 S/m, and 6.3e7 S/m, respectively. As shown in Figure 10, the metal conductivity mainly affects the absorptivity peak value rather than the resonance frequency. In the case of θ = 40°, φ = 0°, the TE waves cause a powerful resonance at 36.9 GHz, whereas the TM waves cause a forceful resonance at 16.055 GHz. The polarization of the incident waves can be achieved from the analysis on the absorptivity of PD with the help of Table 2. Then, we investigate the effects on absorptivity produced by electromagnetic properties of the dielectric. Figure 9 shows the transformation of absorptivity and resonance points of PD when the middle dielectric is porcelain, FR-4, and polyimide with a permittivity of 5.7, 4.4, and 3.5, respectively. The image indicates that the increase of dielectric permittivity triggers a red shift of the resonance frequency, an increase of absorptivity in the high band, and a reduction of absorptivity in the low band. The relevance help concerned individuals to select a suitable dielectric to project the appropriate PD for special circumstances. Finally, in order to study the relationship between the conductivity of metallic material and the absorbing performance of PD, we defined the metal as gold, copper, and silver with conductivity of 4.5e7 S/m, 5.8e7 S/m, and 6.3e7 S/m, respectively. As shown in Figure 10, the metal conductivity mainly affects the absorptivity peak value rather than the resonance frequency.   In the case of θ = 40°, φ = 0°, the TE waves cause a powerful resonance at 36.9 GHz, whereas the TM waves cause a forceful resonance at 16.055 GHz. The polarization of the incident waves can be achieved from the analysis on the absorptivity of PD with the help of Table 2. Then, we investigate the effects on absorptivity produced by electromagnetic properties of the dielectric. Figure 9 shows the transformation of absorptivity and resonance points of PD when the middle dielectric is porcelain, FR-4, and polyimide with a permittivity of 5.7, 4.4, and 3.5, respectively. The image indicates that the increase of dielectric permittivity triggers a red shift of the resonance frequency, an increase of absorptivity in the high band, and a reduction of absorptivity in the low band. The relevance help concerned individuals to select a suitable dielectric to project the appropriate PD for special circumstances. Finally, in order to study the relationship between the conductivity of metallic material and the absorbing performance of PD, we defined the metal as gold, copper, and silver with conductivity of 4.5e7 S/m, 5.8e7 S/m, and 6.3e7 S/m, respectively. As shown in Figure 10, the metal conductivity mainly affects the absorptivity peak value rather than the resonance frequency.

Processing and Testing
To verify the validity of the simulation results, the physical dimensions and material parameters of the manufactured MMA were determined by the optimized analysis presented in Section 2. A type JTRC-550 magnetron sputtering machine (Jiangtai vacuum coating technology Co., Ltd, Chengdu, China) was employed to sputter 0.1 μm copper and 0.3 μm copper on the 40 cm × 40 cm × 200 μm FR-4 board's front and back, respectively. Then, the redundant copper film on the front was removed using LPKF ProtoLaser U3 laser burning equipment (LPKF Laser & Electronics AG, Garbsen, Germany). The left copper film's structure is shown in Figure 1. The flow chart of the process is demonstrated in Figure 11. Figure 12 shows the prepared sample and its local amplifying structure.

. Processing and Testing
To verify the validity of the simulation results, the physical dimensions and material parameters of the manufactured MMA were determined by the optimized analysis presented in Section 2. A type JTRC-550 magnetron sputtering machine (Jiangtai vacuum coating technology Co., Ltd, Chengdu, China) was employed to sputter 0.1 µm copper and 0.3 µm copper on the 40 cmˆ40 cmˆ200 µm FR-4 board's front and back, respectively. Then, the redundant copper film on the front was removed using LPKF ProtoLaser U3 laser burning equipment (LPKF Laser & Electronics AG, Garbsen, Germany). The left copper film's structure is shown in Figure 1. The flow chart of the process is demonstrated in Figure 11. Figure 12 shows the prepared sample and its local amplifying structure.  We adopt the free-space reflection method in an anechoic chamber to test the scattering parameters of the sample. The scene and schematic of the free-space reflection method are shown as Figures 13 and 14. In order to ensure that the electromagnetic waves which incide upon the sample surface are plane waves d, the distance between the antenna and the sample, should meet the far field condition d > (2D 2 )/λ, where λ is the wavelength of the incident waves, and D is the diagonal length of the antenna. In addition, in order to eliminate the sample edge scattering effects which will affect the measurement precision, the size of the test sample should be at least more than two times the maximum working wavelength. The signal source of an Agilent N5224A network analyzer Agilent Technologies, Santa Clara, CA, USA) (shown in Figure 15) with frequency expansion module of 500 GHz is responsible for generating the excitation signal that meets the requirements of frequency and power. The excitation signal is divided into two signals by a power splitter. One of them is served as input signal marked red line in Figure 16, and another one as reference signal marked with a brown line. Then, the input signal is radiated by an emitting antenna. Radiant electromagnetic waves incident upon the metasurface of the prepared PD. A part of the incident waves' energy will be reflected, the surplus energy will be coupled into the metasurface, and then, diffuse continually in the dielectric.  We adopt the free-space reflection method in an anechoic chamber to test the scattering parameters of the sample. The scene and schematic of the free-space reflection method are shown as Figures 13 and 14. In order to ensure that the electromagnetic waves which incide upon the sample surface are plane waves d, the distance between the antenna and the sample, should meet the far field condition d > (2D 2 )/λ, where λ is the wavelength of the incident waves, and D is the diagonal length of the antenna. In addition, in order to eliminate the sample edge scattering effects which will affect the measurement precision, the size of the test sample should be at least more than two times the maximum working wavelength. The signal source of an Agilent N5224A network analyzer Agilent Technologies, Santa Clara, CA, USA) (shown in Figure 15) with frequency expansion module of 500 GHz is responsible for generating the excitation signal that meets the requirements of frequency and power. The excitation signal is divided into two signals by a power splitter. One of them is served as input signal marked red line in Figure 16, and another one as reference signal marked with a brown line. Then, the input signal is radiated by an emitting antenna. Radiant electromagnetic waves incident upon the metasurface of the prepared PD. A part of the incident waves' energy will be reflected, the surplus energy will be coupled into the metasurface, and then, diffuse continually in the dielectric. We adopt the free-space reflection method in an anechoic chamber to test the scattering parameters of the sample. The scene and schematic of the free-space reflection method are shown as Figures 13  and 14. In order to ensure that the electromagnetic waves which incide upon the sample surface are plane waves d, the distance between the antenna and the sample, should meet the far field condition d > (2D 2 )/λ, where λ is the wavelength of the incident waves, and D is the diagonal length of the antenna. In addition, in order to eliminate the sample edge scattering effects which will affect the measurement precision, the size of the test sample should be at least more than two times the maximum working wavelength. The signal source of an Agilent N5224A network analyzer Agilent Technologies, Santa Clara, CA, USA) (shown in Figure 15) with frequency expansion module of 500 GHz is responsible for generating the excitation signal that meets the requirements of frequency and power. The excitation signal is divided into two signals by a power splitter. One of them is served as input signal marked red line in Figure 16, and another one as reference signal marked with a brown line. Then, the input signal is radiated by an emitting antenna. Radiant electromagnetic waves incident upon the metasurface of the prepared PD. A part of the incident waves' energy will be reflected, the surplus energy will be coupled into the metasurface, and then, diffuse continually in the dielectric.     . Figure 15. Photograph of the Agilent N5224A.  . Figure 15. Photograph of the Agilent N5224A.  The contrastive diagrams of the test and simulation results with a vertical incidence and different polarization angles of the TE and TM waves are presented in Figures 17 and 18. The contradictory results indicate that slight resonance point and absorptivity shifts occurred. The causes of delicate differences are analyzed after representing the sample feature. The copper film may be oxidized during the laser ablation process. The thickness of the copper film on the metasurface is asymmetrical because of the micromachining tolerance of the magnetron sputtering machine. Slight deviations between the structure size of the prepared sample and the physical dimensions of the simulated one are inevitable on account of the precision of the laser burning equipment.  The contrastive diagrams of the test and simulation results with a vertical incidence and different polarization angles of the TE and TM waves are presented in Figures 17 and 18. The contradictory results indicate that slight resonance point and absorptivity shifts occurred. The causes of delicate differences are analyzed after representing the sample feature. The copper film may be oxidized during the laser ablation process. The thickness of the copper film on the metasurface is asymmetrical because of the micromachining tolerance of the magnetron sputtering machine. Slight deviations between the structure size of the prepared sample and the physical dimensions of the simulated one are inevitable on account of the precision of the laser burning equipment. The contrastive diagrams of the test and simulation results with a vertical incidence and different polarization angles of the TE and TM waves are presented in Figures 17 and 18. The contradictory results indicate that slight resonance point and absorptivity shifts occurred. The causes of delicate differences are analyzed after representing the sample feature. The copper film may be oxidized during the laser ablation process. The thickness of the copper film on the metasurface is asymmetrical because of the micromachining tolerance of the magnetron sputtering machine. Slight deviations between the structure size of the prepared sample and the physical dimensions of the simulated one are inevitable on account of the precision of the laser burning equipment.

Conclusions
A polarization sensitive MMA was first employed to design a PD and the PD absorptivity is first used to reflect and describe the polarization of incident waves in this paper. The sandwich structures of the presented PD composed of 0.1 μm periodic "I" shaped patches on the metasurface, a dielectric of 200 μm FR-4 on the interlayer, a 0.3 μm copper film on the substrate are uncomplicated, and the preparation technology is fully developed. The study of the influences on absorptivity of the incidence angles, polarization angles, and materials confirmed that the designed and prepared PD with absorbing responses located in the radar bands possesses excellent characteristics such as polarization sensitivity at all incidence angles and an ultrathin structure which are the basic elements for polarization detection. The sample prepared by laser ablation on the FR-4 board coated with copper on a double plane is executed with scattering parameter measurement in a microwave chamber. Compared with simulated results, the tested absorptivity was slightly decreased because of the fabricauion tolerance. Multiband and broadband PD in the desired resonance bands can be designed conveniently by adjusting the structure and size of resonators. The presented PD, which greatly enriches the metamaterial applications in polarized glasses, thermal images, stealth materials, communication and electromagnetic devices, should be easy to mass produce and market because of its strong detectability, ultrathin thickness, low cost, simple structure, and convenient manufacturing process.

Conclusions
A polarization sensitive MMA was first employed to design a PD and the PD absorptivity is first used to reflect and describe the polarization of incident waves in this paper. The sandwich structures of the presented PD composed of 0.1 µm periodic "I" shaped patches on the metasurface, a dielectric of 200 µm FR-4 on the interlayer, a 0.3 µm copper film on the substrate are uncomplicated, and the preparation technology is fully developed. The study of the influences on absorptivity of the incidence angles, polarization angles, and materials confirmed that the designed and prepared PD with absorbing responses located in the radar bands possesses excellent characteristics such as polarization sensitivity at all incidence angles and an ultrathin structure which are the basic elements for polarization detection. The sample prepared by laser ablation on the FR-4 board coated with copper on a double plane is executed with scattering parameter measurement in a microwave chamber. Compared with simulated results, the tested absorptivity was slightly decreased because of the fabricauion tolerance. Multiband and broadband PD in the desired resonance bands can be designed conveniently by adjusting the structure and size of resonators. The presented PD, which greatly enriches the metamaterial applications in polarized glasses, thermal images, stealth materials, communication and electromagnetic devices, should be easy to mass produce and market because of its strong detectability, ultrathin thickness, low cost, simple structure, and convenient manufacturing process.

Conflicts of Interest:
The authors declare no conflict of interest.

Abbreviations
The following abbreviations are used in this manuscript: