Limits...
Manipulating surface-plasmon-polariton launching with quasi-cylindrical waves.

Sun C, Chen J, Yao W, Li H, Gong Q - Sci Rep (2015)

Bottom Line: Consequently, a broadband unidirectional SPP launcher is realized in the asymmetric slit.More importantly, it is found that this principle can be extended to the three-dimensional subwavelength plasmonic waveguide, in which the excited Quasi-CWs in the aperture could be effectively converted to the tightly guided SPP mode along the subwavelength plasmonic waveguide.In the large wavelength range from about 600 nm to 1300 nm, the SPP mode mainly propagates to one direction along the plasmonic waveguide, revealing an ultra-broad (about 700 nm) operation bandwidth of the unidirectional SPP launching.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, China [2] Collaborative Innovation Center of Quantum Matter, Beijing, China.

ABSTRACT
Launching the free-space light to the surface plasmon polaritons (SPPs) in a broad bandwidth is of importance for the future plasmonic circuits. Based on the interference of the pure SPP component, the bandwidths of the unidirectional SPP launching is difficult to be further broadened. By greatly manipulating the SPP intensities with the quasi-cylindrical waves (Quasi-CWs), an ultra-broadband unidirectional SPP launcher is experimentally realized in a submicron asymmetric slit. In the nano-groove of the asymmetric slit, the excited Quasi-CWs are not totally damped, and they can be scattered into the SPPs along the metal surface. This brings additional interference and thus greatly manipulates the SPP launching. Consequently, a broadband unidirectional SPP launcher is realized in the asymmetric slit. More importantly, it is found that this principle can be extended to the three-dimensional subwavelength plasmonic waveguide, in which the excited Quasi-CWs in the aperture could be effectively converted to the tightly guided SPP mode along the subwavelength plasmonic waveguide. In the large wavelength range from about 600 nm to 1300 nm, the SPP mode mainly propagates to one direction along the plasmonic waveguide, revealing an ultra-broad (about 700 nm) operation bandwidth of the unidirectional SPP launching.

No MeSH data available.


Experimental demonstration of the broadband unidirectional SPP launching in the asymmetric slit.(a) SEM image of the experimental sample on the Au film. (b) Detail of the asymmetric slit. Scattered field distributions for different incident wavelengths of (c) λ = 700 nm, (d) λ = 765 nm, (e) λ = 860 nm, and (f) λ = 940 nm. (g) Both the left- (black) and right-propagating (red) SPP launching efficiencies versus the wavelengths obtained in the simulation (solid line) and experiment (symbols).
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f3: Experimental demonstration of the broadband unidirectional SPP launching in the asymmetric slit.(a) SEM image of the experimental sample on the Au film. (b) Detail of the asymmetric slit. Scattered field distributions for different incident wavelengths of (c) λ = 700 nm, (d) λ = 765 nm, (e) λ = 860 nm, and (f) λ = 940 nm. (g) Both the left- (black) and right-propagating (red) SPP launching efficiencies versus the wavelengths obtained in the simulation (solid line) and experiment (symbols).

Mentions: To test our proposal experimentally, the asymmetric slit is fabricated on a planar metal film, and the scanning electron microscope (SEM) image of the experimental sample is shown in Fig. 3(a,b). The measured geometrical parameters of the fabricated asymmetric slit structure are about: wslit = 540 nm, wgroove = 360 nm, and d = 400 nm. So the total lateral dimension is only about 900 nm. An in-chip reference slit is also fabricated for comparison. In the experiment, it is observed that the scattering light from the upper parts of the decoupling gratings is nearly the same because of the structural symmetry of the in-chip reference slit. However, for the lower parts of the decoupling gratings, the phenomena are quite different. We observed that the left grating is nearly dark while the right one keeps bright in a broad bandwidth, and the extinction ratio is greater than 11 dB, as show in Fig. 3(c–f). This indicates the excited SPPs mainly propagate to the right direction. Moreover, the lower right grating is always brighter than the upper gratings, revealing that the launching efficiencies increase greatly. Figure 3(g) depicts the measured launching efficiency, η, at different wavelengths (dots). Here, η is obtained from the quotient between the light intensities scattered from the lower and the upper parts of each decoupling gratings (evaluated by integration over a spatial scale on the grating)18. By doing this, the laser fluctuation and the CCD sensitivity varying with the wavelengths can be eliminated. From Fig. 3(g), it is observed that ηR (red dots) is always greater than 1.5 while ηL (black dots) is nearly vanished within the measured wavelength range from 675 nm to 970 nm, which matches the simulation results (solid lines) quite well. Therefore, a broadband unidirectional SPP launcher with increasing launching efficiencies and high extinction ratios is realized in the submicron asymmetric slit structure.


Manipulating surface-plasmon-polariton launching with quasi-cylindrical waves.

Sun C, Chen J, Yao W, Li H, Gong Q - Sci Rep (2015)

Experimental demonstration of the broadband unidirectional SPP launching in the asymmetric slit.(a) SEM image of the experimental sample on the Au film. (b) Detail of the asymmetric slit. Scattered field distributions for different incident wavelengths of (c) λ = 700 nm, (d) λ = 765 nm, (e) λ = 860 nm, and (f) λ = 940 nm. (g) Both the left- (black) and right-propagating (red) SPP launching efficiencies versus the wavelengths obtained in the simulation (solid line) and experiment (symbols).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4462146&req=5

f3: Experimental demonstration of the broadband unidirectional SPP launching in the asymmetric slit.(a) SEM image of the experimental sample on the Au film. (b) Detail of the asymmetric slit. Scattered field distributions for different incident wavelengths of (c) λ = 700 nm, (d) λ = 765 nm, (e) λ = 860 nm, and (f) λ = 940 nm. (g) Both the left- (black) and right-propagating (red) SPP launching efficiencies versus the wavelengths obtained in the simulation (solid line) and experiment (symbols).
Mentions: To test our proposal experimentally, the asymmetric slit is fabricated on a planar metal film, and the scanning electron microscope (SEM) image of the experimental sample is shown in Fig. 3(a,b). The measured geometrical parameters of the fabricated asymmetric slit structure are about: wslit = 540 nm, wgroove = 360 nm, and d = 400 nm. So the total lateral dimension is only about 900 nm. An in-chip reference slit is also fabricated for comparison. In the experiment, it is observed that the scattering light from the upper parts of the decoupling gratings is nearly the same because of the structural symmetry of the in-chip reference slit. However, for the lower parts of the decoupling gratings, the phenomena are quite different. We observed that the left grating is nearly dark while the right one keeps bright in a broad bandwidth, and the extinction ratio is greater than 11 dB, as show in Fig. 3(c–f). This indicates the excited SPPs mainly propagate to the right direction. Moreover, the lower right grating is always brighter than the upper gratings, revealing that the launching efficiencies increase greatly. Figure 3(g) depicts the measured launching efficiency, η, at different wavelengths (dots). Here, η is obtained from the quotient between the light intensities scattered from the lower and the upper parts of each decoupling gratings (evaluated by integration over a spatial scale on the grating)18. By doing this, the laser fluctuation and the CCD sensitivity varying with the wavelengths can be eliminated. From Fig. 3(g), it is observed that ηR (red dots) is always greater than 1.5 while ηL (black dots) is nearly vanished within the measured wavelength range from 675 nm to 970 nm, which matches the simulation results (solid lines) quite well. Therefore, a broadband unidirectional SPP launcher with increasing launching efficiencies and high extinction ratios is realized in the submicron asymmetric slit structure.

Bottom Line: Consequently, a broadband unidirectional SPP launcher is realized in the asymmetric slit.More importantly, it is found that this principle can be extended to the three-dimensional subwavelength plasmonic waveguide, in which the excited Quasi-CWs in the aperture could be effectively converted to the tightly guided SPP mode along the subwavelength plasmonic waveguide.In the large wavelength range from about 600 nm to 1300 nm, the SPP mode mainly propagates to one direction along the plasmonic waveguide, revealing an ultra-broad (about 700 nm) operation bandwidth of the unidirectional SPP launching.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing 100871, China [2] Collaborative Innovation Center of Quantum Matter, Beijing, China.

ABSTRACT
Launching the free-space light to the surface plasmon polaritons (SPPs) in a broad bandwidth is of importance for the future plasmonic circuits. Based on the interference of the pure SPP component, the bandwidths of the unidirectional SPP launching is difficult to be further broadened. By greatly manipulating the SPP intensities with the quasi-cylindrical waves (Quasi-CWs), an ultra-broadband unidirectional SPP launcher is experimentally realized in a submicron asymmetric slit. In the nano-groove of the asymmetric slit, the excited Quasi-CWs are not totally damped, and they can be scattered into the SPPs along the metal surface. This brings additional interference and thus greatly manipulates the SPP launching. Consequently, a broadband unidirectional SPP launcher is realized in the asymmetric slit. More importantly, it is found that this principle can be extended to the three-dimensional subwavelength plasmonic waveguide, in which the excited Quasi-CWs in the aperture could be effectively converted to the tightly guided SPP mode along the subwavelength plasmonic waveguide. In the large wavelength range from about 600 nm to 1300 nm, the SPP mode mainly propagates to one direction along the plasmonic waveguide, revealing an ultra-broad (about 700 nm) operation bandwidth of the unidirectional SPP launching.

No MeSH data available.