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Virtual Journal for Biomedical Optics

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  • Editor: Gregory W. Faris
  • Vol. 5, Iss. 10 — Jul. 19, 2010
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Surface plasmon-coupled emission from shaped PMMA films doped with fluorescence molecules

D. G . Zhang, K. J. Moh, and X.-C. Yuan  »View Author Affiliations


Optics Express, Vol. 18, Issue 12, pp. 12185-12190 (2010)
http://dx.doi.org/10.1364/OE.18.012185


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Abstract

Surface plasmon-coupled emission from shaped PMMA films doped with randomly oriented fluorescence molecules was investigated. Experimental results show that for different shapes, such as triangle or circular structures, the SPCE ring displays different intensity patterns. For a given shape, it was observed that the relative position and polarization of an incident laser spot on the shaped PMMA can be used to adjust the fluorescence intensity distribution of the SPCE ring. The proposed method enables controlling the fluorescence emission in azimuthal direction in addition to the radial angle controlled by common SPCE, which will further enhances the fluorescence collection efficiency and has applications in fluorescence sensing, imaging and so on.

© 2010 OSA

1. Introduction

2. Sample preparation and experiment

The samples were prepared in the following manner. A sample of Rhodamine B (RhB) powder (0.1mg/ml) was dissolved in a PMMA solution (950K PMMA, 2% in Anisole) and the solution was agitated by ultrasonic disrupter for 30 minutes. Subsequently it was allowed to stand for 48 hours, to ensure that the RhB molecules dissolved totally in solution. The RhB doped complete PMMA film was obtained by spin coating the solution onto a 45 nm-thick silver substrate and the film baked for 10min at 105°C to remove the solvent. The thickness of the PMMA films was about 80nm. An Electron Beam Lithography method (Raith GmbH, e_LiNe) was subsequently used to write different PMMA structured films on the silver substrate.

Leakage radiation microscopy (LRM) [11

11. A. Bouhelier and G. P. Wiederrecht, Excitation of broadband surface plasmon polaritons: Plasmonic continuum spectroscopy, Phys. Rev. B, 71, 195406–1-5 (2005).

14

14. D. G. Zhang, X.-C. Yuan, J. Bu, G. H. Yuan, Q. Wang, J. Lin, X. J. Zhang, P. Wang, H. Ming, and T. Mei, “Surface plasmon converging and diverging properties modulated by polymer refractive structures on metal films,” Opt. Express 17(14), 11315–11320 (2009). [CrossRef] [PubMed]

] was used to characterize the SPCE by observing fluorescence in real and reciprocal spaces respectively. The schematic of the experimental set-up was shown in Fig. 1
Fig. 1 Schematic of the experimental set-up, leaky radiation microscopy.
. A laser beam with 532 nm wavelength was expanded by a lens array to fully fill the rear aperture of an oil-immersion objective (60X, numerical aperture (N.A.), 1.42). The laser beam was tightly focused onto the shaped PMMA films to excite the doped RhB molecules. A pellicle beam-splitter (from Thorlab Corp, working wavelength 400-700nm) and a long pass filter (from SEM ROCK) were used to observe the fluorescence on the CCD. By changing the position of the CCD and the focal length of the imaging lens, we can get both the back focal plane (BFP, also named Fourier plane image) and the image plane images (also named direct-space image) of the objective. The image plane directly gives out the image of the samples and also the fluorescence, whereas, the back focal plane gives out the wave-vector information. The diameter of SPCE ring (BFP image) represents the radial angle of fluorescence emission. The intensity distributions on the ring represent the fluorescence distribution at the azimuthal angles. A fiber illuminator was used to illuminate the samples, so that bright field transmittance images of the samples can be obtained. More details on the characterization of SPCE or SPPs with LRM can be found in References [15

15. D. G. Zhang, X.-C. Yuan, A. Bouhelier, P. Wang, and H. Ming, “Excitation of surface plasmon polaritons guided mode by Rhodamine B molecules doped in a PMMA stripe,” Opt. Lett. 35(3), 408–410 (2010). [CrossRef] [PubMed]

17

17. D. G. Zhang, X. C. Yuan, and A. Bouhelier, “Direct image of surface-plasmon-coupled emission by leakage radiation microscopy,” Appl. Opt. 49(5), 875–879 (2010). [CrossRef] [PubMed]

].

3. Result and discussion

3.1. Effect of shape

Figure 2(c) demonstrates the corresponding Fourier plane fluorescence image. It shows the commonly known SPCE ring: the inner ring is caused by the SPPs-1 waves and the outer by the SPPs-2 waves. The two rings indicate that the fluorescence is mainly emitted at two angles (radial angle). The emitting angles can be estimated as about 43° and 69°, this corresponds to the calculated SPR angles (43.6°, 69.4°, n = 0.12 + 3.547i for Ag) at the peak wavelength of RhB fluorescence (576 nm). The white boxes labeled with 1, 2, 3 are three brighter arcs on the inner ring, indicating that the SPCE intensity is anisotropic in the azimuthal direction. The ratio of maximum intensity to the minimum intensity on the SPCE ring shown in Fig. 2(c) is about 2.3. This is consistent with the findings in Fig. 2(b), which show that the propagation and intensity distribution of the SPPs-1 imaged in the real space are correspondingly reflected in the reciprocal space, such as the 1, 2, and 3 areas marked in Figs. 2(b) and 2(c).

As a comparison, a circularly shape PMMA film doped with RhB molecules was investigated and shown in Fig. 3
Fig. 3 (a): Bright-field transmission image of circular PMMA film acquired by the CCD camera without long pass filter. The central bright spot is the focused laser spot. (b) direct-space fluorescence image; (c) Fourier plane fluorescence image.
. Figure 3(a) is the bright field transmission image observed without the filter and the center bright spot is the location of the focused laser spot on the PMMA film. Figure 3(b) is the direct space fluorescence image, which shows that the excited SPPs-1 wave propagating along the radial directions of the circular. Figure 3(c) is the corresponding Fourier plane (back focal plane shown in Fig. 1 fluorescence image. The white boxes labeled with 1, 2, 3 are at the sample positions as that of Fig. 2(c). When comparing Fig. 2(c) with Fig. 3(c) in the regions marked with the white boxes, we find that the fluorescence intensity distributions on the SPCE ring are different. The ratio of maximum intensity to the minimum intensity on the SPCE ring shown in Fig. 3(c) is about 1.2, which is mainly due to the different reflectivity of different polarizations relative to the plane of the beam-splitter. So experimental results verify that different SPCE intensity pattern can be obtained with different shape of the PMMA films on silver films.

A point to note in the case of circular shape is that when the PMMA films are resolved around the beam axis of the objective and the irradiated position was at the center of the circular PMMA film, the intensity variations of SPCE ring was too small to be distinguished by the CCD camera. This is a verification that the RhB molecules doped in the PMMA film are of random orientations.

3.2. Effect of irradiation location

3.3. Polarization effect

4. Conclusion

Acknowledgement

This work was partially supported by the National Natural Science Foundation of China (NNSFC) under Grant (10974101), the Ministry of Science and Technology of China under Grant 2009DFA52300 for China-Singapore collaborations, and the National Research Foundation of Singapore under Grant NRF-G-CRP 2007-01. D. G. Zhang acknowledges help on SPCE from Prof. J. R. Lakowicz of the Center for Fluorescence Spectroscopy, University Maryland School of Medicine.

References and Links:

1.

W. L. Barnes, A. Dereux, and T. W. Ebbesen, “Surface plasmon subwavelength optics,” Nature 424(6950), 824–830 (2003). [CrossRef] [PubMed]

2.

J. R. Lakowicz and Y. Fu, “Modification of single molecule fluorescence near metallic nanostructures,” Laser & Photonics Reviews 3(1-2), 221–232 (2009). [CrossRef]

3.

J. Zhang, Y. Fu, M. H. Chowdhury, and J. R. Lakowicz, “Metal-enhanced single-molecule fluorescence on silver particle monomer and dimer: coupling effect between metal particles,” Nano Lett. 7(7), 2101–2107 (2007). [CrossRef] [PubMed]

4.

J. R. Lakowicz, J. Malicka, I. Gryczynski, and Z. Gryczynski, “Directional surface plasmon-coupled emission: A new method for high sensitivity detection,” Biochem. Biophys. Res. Commun. 307(3), 435–439 (2003). [CrossRef] [PubMed]

5.

J. R. Lakowicz, “Radiative decay engineering 3. Surface plasmon-coupled directional emission,” Anal. Biochem. 324(2), 153–169 (2004). [CrossRef]

6.

I. Gryczynski, J. Malicka, Z. Gryczynski, and J. R. Lakowicz, “Radiative decay engineering 4. Experimental studies of surface plasmon-coupled directional emission,” Anal. Biochem. 324(2), 170–182 (2004). [CrossRef]

7.

C. D. Geddes, I. Gryczynski, J. Malicka, Z. Gryczynski, and J. R. Lakowicz, “Directional surface plasmon coupled emission,” J. Fluoresc. 14(1), 119–123 (2004). [CrossRef] [PubMed]

8.

N. Calander, “Theory and simulation of surface plasmon-coupled directional emission from fluorophores at planar structures,” Anal. Chem. 76(8), 2168–2173 (2004). [CrossRef] [PubMed]

9.

H. M. Hiep, M. Fujii, and S. Hayashi, Effects of molecular orientation on surface-plasmon-coupled emission patterns, Appl.Phys.Lett, 91, 183110–1-3(2007).

10.

M.Ghazali, F.Adlina, F.Minoru, and H. Shinji, Anisotropic propagation of surface plasmon polaritons caused by oriented molecular overlayer, Appl.Phys.Lett, 95, 033303–1-3(2009).

11.

A. Bouhelier and G. P. Wiederrecht, Excitation of broadband surface plasmon polaritons: Plasmonic continuum spectroscopy, Phys. Rev. B, 71, 195406–1-5 (2005).

12.

D. G. Zhang, X.-C. Yuan, A. Bouhelier, G. H. Yuan, P. Wang, and H. Ming, Active control of surface plasmon polaritons by optical isomerization of an azobenzene polymer film, Appl.Phys. Lett, 95, 101102–1-3(2009).

13.

A. L. Stepanov, J. R. Krenn, H. Ditlbacher, A. Hohenau, A. Drezet, B. Steinberger, A. Leitner, and F. R. Aussenegg, “Quantitative analysis of surface plasmon interaction with silver nanoparticles,” Opt. Lett. 30(12), 1524–1526 (2005). [CrossRef] [PubMed]

14.

D. G. Zhang, X.-C. Yuan, J. Bu, G. H. Yuan, Q. Wang, J. Lin, X. J. Zhang, P. Wang, H. Ming, and T. Mei, “Surface plasmon converging and diverging properties modulated by polymer refractive structures on metal films,” Opt. Express 17(14), 11315–11320 (2009). [CrossRef] [PubMed]

15.

D. G. Zhang, X.-C. Yuan, A. Bouhelier, P. Wang, and H. Ming, “Excitation of surface plasmon polaritons guided mode by Rhodamine B molecules doped in a PMMA stripe,” Opt. Lett. 35(3), 408–410 (2010). [CrossRef] [PubMed]

16.

D. G. Zhang, X.-C. Yuan, G. H. Yuan, P. Wang, and H. Ming, “Directional fluorescence emission characterized with leakage radiation microscopy,” J. Opt. 12(3), 035002 (2010). [CrossRef]

17.

D. G. Zhang, X. C. Yuan, and A. Bouhelier, “Direct image of surface-plasmon-coupled emission by leakage radiation microscopy,” Appl. Opt. 49(5), 875–879 (2010). [CrossRef] [PubMed]

18.

Q. W. Zhan and J. Leger, “Focus shaping using cylindrical vector beams,” Opt. Express 10(7), 324–331 (2002). [PubMed]

OCIS Codes
(240.6680) Optics at surfaces : Surface plasmons
(260.2510) Physical optics : Fluorescence
(310.6860) Thin films : Thin films, optical properties

ToC Category:
Optics at Surfaces

History
Original Manuscript: March 17, 2010
Revised Manuscript: April 6, 2010
Manuscript Accepted: April 6, 2010
Published: May 25, 2010

Virtual Issues
Vol. 5, Iss. 10 Virtual Journal for Biomedical Optics

Citation
D. G . Zhang, K. J. Moh, and X.-C. Yuan, "Surface plasmon-coupled emission from shaped PMMA films doped with fluorescence molecules," Opt. Express 18, 12185-12190 (2010)
http://www.opticsinfobase.org/vjbo/abstract.cfm?URI=oe-18-12-12185


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References

  1. W. L. Barnes, A. Dereux, and T. W. Ebbesen, “Surface plasmon subwavelength optics,” Nature 424(6950), 824–830 (2003). [CrossRef] [PubMed]
  2. J. R. Lakowicz and Y. Fu, “Modification of single molecule fluorescence near metallic nanostructures,” Laser & Photonics Reviews 3(1-2), 221–232 (2009). [CrossRef]
  3. J. Zhang, Y. Fu, M. H. Chowdhury, and J. R. Lakowicz, “Metal-enhanced single-molecule fluorescence on silver particle monomer and dimer: coupling effect between metal particles,” Nano Lett. 7(7), 2101–2107 (2007). [CrossRef] [PubMed]
  4. J. R. Lakowicz, J. Malicka, I. Gryczynski, and Z. Gryczynski, “Directional surface plasmon-coupled emission: A new method for high sensitivity detection,” Biochem. Biophys. Res. Commun. 307(3), 435–439 (2003). [CrossRef] [PubMed]
  5. J. R. Lakowicz, “Radiative decay engineering 3. Surface plasmon-coupled directional emission,” Anal. Biochem. 324(2), 153–169 (2004). [CrossRef]
  6. I. Gryczynski, J. Malicka, Z. Gryczynski, and J. R. Lakowicz, “Radiative decay engineering 4. Experimental studies of surface plasmon-coupled directional emission,” Anal. Biochem. 324(2), 170–182 (2004). [CrossRef]
  7. C. D. Geddes, I. Gryczynski, J. Malicka, Z. Gryczynski, and J. R. Lakowicz, “Directional surface plasmon coupled emission,” J. Fluoresc. 14(1), 119–123 (2004). [CrossRef] [PubMed]
  8. N. Calander, “Theory and simulation of surface plasmon-coupled directional emission from fluorophores at planar structures,” Anal. Chem. 76(8), 2168–2173 (2004). [CrossRef] [PubMed]
  9. H. M. Hiep, M. Fujii, and S. Hayashi, Effects of molecular orientation on surface-plasmon-coupled emission patterns, Appl.Phys.Lett, 91, 183110–1-3(2007).
  10. M. Ghazali, F. Adlina, F. Minoru, and H. Shinji, Anisotropic propagation of surface plasmon polaritons caused by oriented molecular overlayer, Appl.Phys.Lett, 95, 033303–1-3(2009).
  11. A. Bouhelier and G. P. Wiederrecht, Excitation of broadband surface plasmon polaritons: Plasmonic continuum spectroscopy, Phys. Rev. B, 71, 195406–1-5 (2005).
  12. D. G. Zhang, X.-C. Yuan, A. Bouhelier, G. H. Yuan, P. Wang, and H. Ming, Active control of surface plasmon polaritons by optical isomerization of an azobenzene polymer film, Appl. Phys. Lett 95, 101102–1-3(2009).
  13. A. L. Stepanov, J. R. Krenn, H. Ditlbacher, A. Hohenau, A. Drezet, B. Steinberger, A. Leitner, and F. R. Aussenegg, “Quantitative analysis of surface plasmon interaction with silver nanoparticles,” Opt. Lett. 30(12), 1524–1526 (2005). [CrossRef] [PubMed]
  14. D. G. Zhang, X.-C. Yuan, J. Bu, G. H. Yuan, Q. Wang, J. Lin, X. J. Zhang, P. Wang, H. Ming, and T. Mei, “Surface plasmon converging and diverging properties modulated by polymer refractive structures on metal films,” Opt. Express 17(14), 11315–11320 (2009). [CrossRef] [PubMed]
  15. D. G. Zhang, X.-C. Yuan, A. Bouhelier, P. Wang, and H. Ming, “Excitation of surface plasmon polaritons guided mode by Rhodamine B molecules doped in a PMMA stripe,” Opt. Lett. 35(3), 408–410 (2010). [CrossRef] [PubMed]
  16. D. G. Zhang, X.-C. Yuan, G. H. Yuan, P. Wang, and H. Ming, “Directional fluorescence emission characterized with leakage radiation microscopy,” J. Opt. 12(3), 035002 (2010). [CrossRef]
  17. D. G. Zhang, X. C. Yuan, and A. Bouhelier, “Direct image of surface-plasmon-coupled emission by leakage radiation microscopy,” Appl. Opt. 49(5), 875–879 (2010). [CrossRef] [PubMed]
  18. Q. W. Zhan and J. Leger, “Focus shaping using cylindrical vector beams,” Opt. Express 10(7), 324–331 (2002). [PubMed]

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