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Spoof localized surface plasmons on ultrathin textured MIM ring resonator with enhanced resonances.

Zhou YJ, Xiao QX, Yang BJ - Sci Rep (2015)

Bottom Line: Quality factors of resonance peaks have become much larger and multipolar resonances modes can be easily observed on the textured MIM ring resonator excited by a microstrip line.We have shown that the fabricated resonator is sensitive to the variation of both the dielectric constant and the thickness of surrounding materials under test.The spoof plasmonic resonator can be used as key elements to provide many important device functionalities such as optical communications, signal processing, and spectral engineering in the plasmonic integration platform.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072, China.

ABSTRACT
We numerically demonstrate that spoof localized surface plasmons (LSPs) resonant modes can be enhanced based on ultrathin corrugated metal-insulator-metal (MIM) ring resonator. Further enhancement of the LSPs modes has been achieved by incorporating an efficient and ease-of-integration exciting method. Quality factors of resonance peaks have become much larger and multipolar resonances modes can be easily observed on the textured MIM ring resonator excited by a microstrip line. Experimental results validate the high-efficiency excitation and resonance enhancements of spoof LSPs modes on the MIM ring resonator in the microwave frequencies. We have shown that the fabricated resonator is sensitive to the variation of both the dielectric constant and the thickness of surrounding materials under test. The spoof plasmonic resonator can be used as key elements to provide many important device functionalities such as optical communications, signal processing, and spectral engineering in the plasmonic integration platform.

No MeSH data available.


(a) Schematic diagram of the single straight corrugated strip excited by the microstrip line on the bottom of the substrate, where ws = 1.1 mm, ls = 6 mm, and r1 = 1.5 mm. (b) Schematic diagram of the straight corrugated MIM waveguide excited by the microstrip line. 2D electric-field distribution in the xy-plane at 8 GHz for the single corrugated strip (c) and for the corrugated MIM waveguide (d). (e) The electric fields varying on an observed line along the x direction, which is corresponding to the white dotted line in Fig. 3(a,b). (f) The electric fields in the xy-plane and (g) the magnetic fields in the xz-plane for the corrugated MIM waveguide at 8 GHz.
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f3: (a) Schematic diagram of the single straight corrugated strip excited by the microstrip line on the bottom of the substrate, where ws = 1.1 mm, ls = 6 mm, and r1 = 1.5 mm. (b) Schematic diagram of the straight corrugated MIM waveguide excited by the microstrip line. 2D electric-field distribution in the xy-plane at 8 GHz for the single corrugated strip (c) and for the corrugated MIM waveguide (d). (e) The electric fields varying on an observed line along the x direction, which is corresponding to the white dotted line in Fig. 3(a,b). (f) The electric fields in the xy-plane and (g) the magnetic fields in the xz-plane for the corrugated MIM waveguide at 8 GHz.

Mentions: There is an important question of how to excite efficiently spoof SPPs on the spoof plasmonic waveguides. The launching device can be considered as a field transformer which converts the field of a waveguide into that of spoof SPPs. The efficiency will be greater if the field built up by the launching device has a better agreement to that of surface wave50. The ultrathin MIM waveguide without grooves is similar to the slot line which has been deeply investigated and widely used in microwave circuits. It’s been found that if a slot line and a microstrip line cross each other at right angles, coupling will be especially tight51 due to good magnetic field matching between the slot line and the microstrip line. Here a microstrip line is used to excite spoof SPPs on the straight single or MIM corrugated strips. The schematic configurations are displayed in Fig. 3(a,b), where the EM energies are fed by the microstrip line (see the red dashed line) on the bottom of the dielectric substrate. In order to minimize the reflected waves from the end of the microstrip line, the metallic disk with radius r1 = 1.5 mm is connected to the microstrip line to increase the coupling degree of EM energies52. The width ws and length ls of the microstrip line are 1.1 mm and 6 mm, respectively. The tapering part is also used to avoid reflection. First, we observe the 2D electric field distribution in the xy-plane at 8 GHz, as illustrated in Fig. 3(c,d). Figure 3(e) shows the electric fields varying on an observed line along the x direction, which is corresponding to the white dotted line in Fig. 3(a,b). It is clearly found that the electric fields in the corrugated MIM strips are much higher than those in single corrugated strip. This better field confinement is consistent with the dispersion analysis in Fig. 2(c). Besides, it has been shown that the loss of spoof SPPs in corrugated MIM waveguide is obviously lower than that in single corrugated metallic strip23. Q factor is 2π times the ratio of the total energy stored divided by the energy lost in a single cycle. The larger the total energy stored is or the smaller the energy loss is, the larger Q factor is. Hence, it’s expected that Q factor of resonance modes in the corrugated MIM ring structure should be larger than that in the corrugated disk. Second, the electric fields on the xy-plane and the magnetic fields on the xz-plane of the corrugated MIM waveguide at 8 GHz are demonstrated in Fig. 3(f,g). Firstly, the dominant surface wave mode on the corrugated MIM waveguide is anti-symmetric (odd mode), which has been reported earlier48. Secondly, the major electric field component is oriented across the insulator (air) and the longitudinal component of the electric field is very weak. The major magnetic field component is vertical to the insulator surface, as shown in Fig. 3(g). After figuring out the EM field distributions on the corrugated MIM waveguide, we can understand why spoof LSPs in the corrugated MIM ring can be excited by different excitation sources in the following section. The exciting efficiency depends on the matching degree between the magnetic field of the exciting source and that in the corrugated MIM ring.


Spoof localized surface plasmons on ultrathin textured MIM ring resonator with enhanced resonances.

Zhou YJ, Xiao QX, Yang BJ - Sci Rep (2015)

(a) Schematic diagram of the single straight corrugated strip excited by the microstrip line on the bottom of the substrate, where ws = 1.1 mm, ls = 6 mm, and r1 = 1.5 mm. (b) Schematic diagram of the straight corrugated MIM waveguide excited by the microstrip line. 2D electric-field distribution in the xy-plane at 8 GHz for the single corrugated strip (c) and for the corrugated MIM waveguide (d). (e) The electric fields varying on an observed line along the x direction, which is corresponding to the white dotted line in Fig. 3(a,b). (f) The electric fields in the xy-plane and (g) the magnetic fields in the xz-plane for the corrugated MIM waveguide at 8 GHz.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588594&req=5

f3: (a) Schematic diagram of the single straight corrugated strip excited by the microstrip line on the bottom of the substrate, where ws = 1.1 mm, ls = 6 mm, and r1 = 1.5 mm. (b) Schematic diagram of the straight corrugated MIM waveguide excited by the microstrip line. 2D electric-field distribution in the xy-plane at 8 GHz for the single corrugated strip (c) and for the corrugated MIM waveguide (d). (e) The electric fields varying on an observed line along the x direction, which is corresponding to the white dotted line in Fig. 3(a,b). (f) The electric fields in the xy-plane and (g) the magnetic fields in the xz-plane for the corrugated MIM waveguide at 8 GHz.
Mentions: There is an important question of how to excite efficiently spoof SPPs on the spoof plasmonic waveguides. The launching device can be considered as a field transformer which converts the field of a waveguide into that of spoof SPPs. The efficiency will be greater if the field built up by the launching device has a better agreement to that of surface wave50. The ultrathin MIM waveguide without grooves is similar to the slot line which has been deeply investigated and widely used in microwave circuits. It’s been found that if a slot line and a microstrip line cross each other at right angles, coupling will be especially tight51 due to good magnetic field matching between the slot line and the microstrip line. Here a microstrip line is used to excite spoof SPPs on the straight single or MIM corrugated strips. The schematic configurations are displayed in Fig. 3(a,b), where the EM energies are fed by the microstrip line (see the red dashed line) on the bottom of the dielectric substrate. In order to minimize the reflected waves from the end of the microstrip line, the metallic disk with radius r1 = 1.5 mm is connected to the microstrip line to increase the coupling degree of EM energies52. The width ws and length ls of the microstrip line are 1.1 mm and 6 mm, respectively. The tapering part is also used to avoid reflection. First, we observe the 2D electric field distribution in the xy-plane at 8 GHz, as illustrated in Fig. 3(c,d). Figure 3(e) shows the electric fields varying on an observed line along the x direction, which is corresponding to the white dotted line in Fig. 3(a,b). It is clearly found that the electric fields in the corrugated MIM strips are much higher than those in single corrugated strip. This better field confinement is consistent with the dispersion analysis in Fig. 2(c). Besides, it has been shown that the loss of spoof SPPs in corrugated MIM waveguide is obviously lower than that in single corrugated metallic strip23. Q factor is 2π times the ratio of the total energy stored divided by the energy lost in a single cycle. The larger the total energy stored is or the smaller the energy loss is, the larger Q factor is. Hence, it’s expected that Q factor of resonance modes in the corrugated MIM ring structure should be larger than that in the corrugated disk. Second, the electric fields on the xy-plane and the magnetic fields on the xz-plane of the corrugated MIM waveguide at 8 GHz are demonstrated in Fig. 3(f,g). Firstly, the dominant surface wave mode on the corrugated MIM waveguide is anti-symmetric (odd mode), which has been reported earlier48. Secondly, the major electric field component is oriented across the insulator (air) and the longitudinal component of the electric field is very weak. The major magnetic field component is vertical to the insulator surface, as shown in Fig. 3(g). After figuring out the EM field distributions on the corrugated MIM waveguide, we can understand why spoof LSPs in the corrugated MIM ring can be excited by different excitation sources in the following section. The exciting efficiency depends on the matching degree between the magnetic field of the exciting source and that in the corrugated MIM ring.

Bottom Line: Quality factors of resonance peaks have become much larger and multipolar resonances modes can be easily observed on the textured MIM ring resonator excited by a microstrip line.We have shown that the fabricated resonator is sensitive to the variation of both the dielectric constant and the thickness of surrounding materials under test.The spoof plasmonic resonator can be used as key elements to provide many important device functionalities such as optical communications, signal processing, and spectral engineering in the plasmonic integration platform.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Specialty Fiber Optics and Optical Access Networks, Shanghai University, Shanghai 200072, China.

ABSTRACT
We numerically demonstrate that spoof localized surface plasmons (LSPs) resonant modes can be enhanced based on ultrathin corrugated metal-insulator-metal (MIM) ring resonator. Further enhancement of the LSPs modes has been achieved by incorporating an efficient and ease-of-integration exciting method. Quality factors of resonance peaks have become much larger and multipolar resonances modes can be easily observed on the textured MIM ring resonator excited by a microstrip line. Experimental results validate the high-efficiency excitation and resonance enhancements of spoof LSPs modes on the MIM ring resonator in the microwave frequencies. We have shown that the fabricated resonator is sensitive to the variation of both the dielectric constant and the thickness of surrounding materials under test. The spoof plasmonic resonator can be used as key elements to provide many important device functionalities such as optical communications, signal processing, and spectral engineering in the plasmonic integration platform.

No MeSH data available.