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Experimental demonstration of a transparent graphene millimetre wave absorber with 28% fractional bandwidth at 140 GHz.

Wu B, Tuncer HM, Naeem M, Yang B, Cole MT, Milne WI, Hao Y - Sci Rep (2014)

Bottom Line: Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate.Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125-165 GHz.Our data suggests that the absorbers' operation can also be extended to microwave and low-terahertz bands with negligible loss in performance.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Electronic Engineering and Computer Science, Queen Mary University of London, London, E1 4NS, United Kingdom [2] School of Electronic Engineering, Xidian University, Xi'an, 710071, China.

ABSTRACT
The development of transparent radio-frequency electronics has been limited, until recently, by the lack of suitable materials. Naturally thin and transparent graphene may lead to disruptive innovations in such applications. Here, we realize optically transparent broadband absorbers operating in the millimetre wave regime achieved by stacking graphene bearing quartz substrates on a ground plate. Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate. An analytical model has been developed to predict the absorption performance and the angular dependence of the absorber. Using a repeated transfer-and-etch process, multilayer graphene was processed to control its surface resistivity. Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125-165 GHz. Our data suggests that the absorbers' operation can also be extended to microwave and low-terahertz bands with negligible loss in performance.

No MeSH data available.


Related in: MedlinePlus

Comparison of calculated and measured spectra of stacked graphene-quartz absorbers.(a, c) Calculated reflection and absorption spectra showing a centre frequency at 148 GHz and an increased number of reflection zeros (or absorption peaks) as well as absorption bandwidth from N = 1 to N = 5, where N is the number of stacked graphene-quartz units. All graphene sheets are assumed to have the same parameters (μc = 0.15 eV, Γ = 5 meV) and separated by homogeneous quartz substrate (εr = 3.8 and h = 1.3 mm). (b, d) Measured reflection and absorption spectra show similar responses as the calculations. The observed slight frequency shift and amplitude variation are mainly associated with parameter differences between each sample and experimental systematic errors.
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f4: Comparison of calculated and measured spectra of stacked graphene-quartz absorbers.(a, c) Calculated reflection and absorption spectra showing a centre frequency at 148 GHz and an increased number of reflection zeros (or absorption peaks) as well as absorption bandwidth from N = 1 to N = 5, where N is the number of stacked graphene-quartz units. All graphene sheets are assumed to have the same parameters (μc = 0.15 eV, Γ = 5 meV) and separated by homogeneous quartz substrate (εr = 3.8 and h = 1.3 mm). (b, d) Measured reflection and absorption spectra show similar responses as the calculations. The observed slight frequency shift and amplitude variation are mainly associated with parameter differences between each sample and experimental systematic errors.

Mentions: The calculation results for stacked graphene-quartz absorbers are depicted in Fig. 4a and 4c. For simplicity, the graphene films are assumed to have the same parameters as per the initial calculation (Γ = 5 meV, μc = 0.15 eV) which corresponds to a sheet resistance of 859 Ω/sq. The calculated reflection spectra in Fig. 4a have the same number of reflection zeros as the measured stacked units, which extends the absorption bandwidth but keeps the centre frequency around 148 GHz. A similar phenomenon exists in the absorption spectra in Fig. 4c, which show more absorption peaks and wider absorption bands as the layers increase. Mutual coupling of the Fabry-Perot resonators contributes to the multiple absorption peaks within the band. The measured results in Fig. 4b and 4d show a good agreement with the calculations, except for a small frequency shift of reflection zeros and an increased reflection within the band. The difference is possibly due to parameter errors and additional losses in the practical samples, as well as the small air-gap between adjacent units that induces multiple reflections. For the 5-unit stacked absorber, approximately 90% absorption can be achieved for 125–165 GHz, which indicates the practical millimetre wave absorber has a 28% fractional absorption bandwidth with the added benefit of optical transparency.


Experimental demonstration of a transparent graphene millimetre wave absorber with 28% fractional bandwidth at 140 GHz.

Wu B, Tuncer HM, Naeem M, Yang B, Cole MT, Milne WI, Hao Y - Sci Rep (2014)

Comparison of calculated and measured spectra of stacked graphene-quartz absorbers.(a, c) Calculated reflection and absorption spectra showing a centre frequency at 148 GHz and an increased number of reflection zeros (or absorption peaks) as well as absorption bandwidth from N = 1 to N = 5, where N is the number of stacked graphene-quartz units. All graphene sheets are assumed to have the same parameters (μc = 0.15 eV, Γ = 5 meV) and separated by homogeneous quartz substrate (εr = 3.8 and h = 1.3 mm). (b, d) Measured reflection and absorption spectra show similar responses as the calculations. The observed slight frequency shift and amplitude variation are mainly associated with parameter differences between each sample and experimental systematic errors.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3928574&req=5

f4: Comparison of calculated and measured spectra of stacked graphene-quartz absorbers.(a, c) Calculated reflection and absorption spectra showing a centre frequency at 148 GHz and an increased number of reflection zeros (or absorption peaks) as well as absorption bandwidth from N = 1 to N = 5, where N is the number of stacked graphene-quartz units. All graphene sheets are assumed to have the same parameters (μc = 0.15 eV, Γ = 5 meV) and separated by homogeneous quartz substrate (εr = 3.8 and h = 1.3 mm). (b, d) Measured reflection and absorption spectra show similar responses as the calculations. The observed slight frequency shift and amplitude variation are mainly associated with parameter differences between each sample and experimental systematic errors.
Mentions: The calculation results for stacked graphene-quartz absorbers are depicted in Fig. 4a and 4c. For simplicity, the graphene films are assumed to have the same parameters as per the initial calculation (Γ = 5 meV, μc = 0.15 eV) which corresponds to a sheet resistance of 859 Ω/sq. The calculated reflection spectra in Fig. 4a have the same number of reflection zeros as the measured stacked units, which extends the absorption bandwidth but keeps the centre frequency around 148 GHz. A similar phenomenon exists in the absorption spectra in Fig. 4c, which show more absorption peaks and wider absorption bands as the layers increase. Mutual coupling of the Fabry-Perot resonators contributes to the multiple absorption peaks within the band. The measured results in Fig. 4b and 4d show a good agreement with the calculations, except for a small frequency shift of reflection zeros and an increased reflection within the band. The difference is possibly due to parameter errors and additional losses in the practical samples, as well as the small air-gap between adjacent units that induces multiple reflections. For the 5-unit stacked absorber, approximately 90% absorption can be achieved for 125–165 GHz, which indicates the practical millimetre wave absorber has a 28% fractional absorption bandwidth with the added benefit of optical transparency.

Bottom Line: Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate.Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125-165 GHz.Our data suggests that the absorbers' operation can also be extended to microwave and low-terahertz bands with negligible loss in performance.

View Article: PubMed Central - PubMed

Affiliation: 1] School of Electronic Engineering and Computer Science, Queen Mary University of London, London, E1 4NS, United Kingdom [2] School of Electronic Engineering, Xidian University, Xi'an, 710071, China.

ABSTRACT
The development of transparent radio-frequency electronics has been limited, until recently, by the lack of suitable materials. Naturally thin and transparent graphene may lead to disruptive innovations in such applications. Here, we realize optically transparent broadband absorbers operating in the millimetre wave regime achieved by stacking graphene bearing quartz substrates on a ground plate. Broadband absorption is a result of mutually coupled Fabry-Perot resonators represented by each graphene-quartz substrate. An analytical model has been developed to predict the absorption performance and the angular dependence of the absorber. Using a repeated transfer-and-etch process, multilayer graphene was processed to control its surface resistivity. Millimetre wave reflectometer measurements of the stacked graphene-quartz absorbers demonstrated excellent broadband absorption of 90% with a 28% fractional bandwidth from 125-165 GHz. Our data suggests that the absorbers' operation can also be extended to microwave and low-terahertz bands with negligible loss in performance.

No MeSH data available.


Related in: MedlinePlus