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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 17, Iss. 10 — May. 11, 2009
  • pp: 8548–8551
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Towards the lasing spaser: controlling metamaterial optical response with semiconductor quantum dots

E. Plum, V. A. Fedotov, P. Kuo, D. P. Tsai, and N. I. Zheludev  »View Author Affiliations


Optics Express, Vol. 17, Issue 10, pp. 8548-8551 (2009)
http://dx.doi.org/10.1364/OE.17.008548


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Abstract

We report the first experimental demonstration of compensating Joule losses in metallic photonic metamaterial using optically pumped PbS semiconductor quantum dots.

© 2009 OSA

Metallic Joule losses in nano-structured metamaterials are the main obstacle in achieving optical negative index media and narrow resonance frequency selective surfaces for photonic applications. Several schemes have been suggested to overcome these losses including using gain media and parametric processes [1

1. A. B. Kozyrev, H. Kim, and D. W. van der Weide, “Parametric amplification in left-handed transmission line media,” Appl. Phys. Lett. 88(26), 264101 (2006). [CrossRef]

9

9. Z.-G. Dong, H. Liu, T. Li, Z.-H. Zhu, S.-M. Wang, J.-X. Cao, S.-N. Zhu, and X. Zhang, “Resonance amplification of left-handed transmission at optical frequencies by stimulated emission of radiation in active metamaterials,” Opt. Express 16(25), 20974–20980 (2008). [CrossRef] [PubMed]

]. In particular it has been shown theoretically that through the local-field amplification mechanism a very small amount of gain can strongly change absorption and transmission of certain metamaterials [10

10. N. I. Zheludev, S. L. Prosvirnin, N. Papasimakis, and V. A. Fedotov, “Lasing spaser,” Nat. Photonics 2(6), 351–354 (2008). [CrossRef]

,11

11. M. Wegener, J. L. García-Pomar, C. M. Soukoulis, N. Meinzer, M. Ruther, and S. Linden, “Toy model for plasmonic metamaterial resonances coupled to two-level system gain,” Opt. Express 16(24), 19785–19798 (2008). [CrossRef] [PubMed]

] to the extend of creating conditions for a metamaterial lasing device, the “lasing spaser”, a metamaterial version of the spaser [12

12. D. J. Bergman and M. I. Stockman, “Surface plasmon amplification by stimulated emission of radiation: quantum generation of coherent surface plasmons in nanosystems,” Phys. Rev. Lett. 90(2), 027402 (2003). [CrossRef] [PubMed]

]. In this paper for the first time we demonstrate experimentally that hybridization of a metamaterial with a layer of semiconductor quantum dots has a profound effect on its optical properties: first, a layer of quantum dots deposited on a metamaterial red-shifts its resonances, and second, when the quantum dots are optically pumped the resonant transmission is modified in a way corresponding to the reduction of Joule losses, thus providing the first step towards the demonstration of a metamaterial gain device and the lasing spaser.

Metamaterials supporting trapped-mode resonances, i.e. current oscillations weakly coupled to free space and thus exhibiting low radiation losses are of special interest from the standpoint of loss control. In photonic trapped-mode metamaterials the resistive Joule loss is the main mechanism of dissipation as radiation losses are small and may be controlled by design. Arrays of asymmetrically split ring resonators belong to this class of metamaterials where the quality factor of the trapped-mode resonance may be controlled by the degree of asymmetry of the split [13

13. V. A. Fedotov, M. Rose, S. L. Prosvirnin, N. Papasimakis, and N. I. Zheludev, “Sharp trapped-mode resonances in planar metamaterials with a broken structural symmetry,” Phys. Rev. Lett. 99(14), 147401 (2007). [CrossRef] [PubMed]

]. Moreover, strong interaction between the magnetic moments of the oscillating trapped-mode currents in arrays of asymmetrically split rings offer the intriguing opportunity of creating a coherent source of optical radiation, the lasing spaser, fueled by plasmonic current oscillations. In this case the gain substrate supporting the rings is the source of energy for the lasing spaser device.

In our experiment reported here we used a négative metamaterial array of split ring slits. The ring slits were cut from a 55 nm thick gold film supported by a silica substrate using focused ion beam milling (see Fig. 1
Fig. 1 Photonic metamaterial hybridized with semiconductor quantum dots. The insets show the metamaterial unit cell and an SEM image of the actual metamaterial structure.
). The unit cell of the structure (360 x 360 nm2) contained a square “ring” with the following design parameters: the ring was 290 x 290 nm2 in size and had a 100 nm wide asymmetric split. The overall size of the metamaterial array was 45 x 45 μm2.

Transmission properties of the metamaterial array were characterized using a microscope-based spectrophotometer by CRAIC Technologies. Optical characteristics of the structure are polarization-sensitive. In a positive (complementary) design consisting of wire rings [13

13. V. A. Fedotov, M. Rose, S. L. Prosvirnin, N. Papasimakis, and N. I. Zheludev, “Sharp trapped-mode resonances in planar metamaterials with a broken structural symmetry,” Phys. Rev. Lett. 99(14), 147401 (2007). [CrossRef] [PubMed]

] the trapped mode would be excited by light polarized along the split. However, as dictated by the Babinet principle, in a négative structure of slits the trapped-mode resonance will be excited with the polarization perpendicular to the direction of the split. Indeed, according to Fig. 2(a)
Fig. 2 Transmission spectra of (a) the metamaterial before deposition of quantum dots and (b) the metamaterial after deposition of PbS quantum dots. Blue lines correspond to x-polarization, black lines correspond to y-polarization and a differential spectrum Ty-Tx is shown in gray. The trapped-mode resonance for y-polarization is marked by a gray shaded region. (c) Transmission spectrum of PbS quantum dots on a glass substrate (blue line). The resonant curves show the change ΔT of the transmission signal due to optically pumping the quantum dot layer on the glass substrate. (d) Difference between pump-induced changes of the transmission signal for x and y-polarizations for different levels of pumping.
which shows transmission spectra of the array for two perpendicular polarizations, the transmission spectrum is featureless for light polarized along the split, while a resonant dip in transmission at 860 nm corresponds to the excitation of the trapped mode for the perpendicular polarization. While for microwave metamaterials consisting of a metal plate perforated with asymmetric ring slits the trapped mode resonance occurs when the wavelength is twice the average slit length [14

14. E. Plum, X.-X. Liu, V. A. Fedotov, Y. Chen, D. P. Tsai, and N. I. Zheludev, “Metamaterials: Optical Activity without Chirality,” Phys. Rev. Lett. 102(11), 113902 (2009). [CrossRef] [PubMed]

], here it is slightly red-shifted due to the presence of the silica substrate and relative increase of the slit width.

To study the role of optical gain on characteristics of the metamaterial it was functionalized with semiconductor quantum dots (QDs). We used quantum dots with a 3.2 nm diameter PbS-core surrounded by a 2 nm thick shell of ligands, which were deposited on the metamaterial array as a suspension in toluene and then dried. The density of quantum dots was determined from the QD molar extinction coefficient (6 x104 L mol−1 cm−1) in control measurements on the glass substrate: the strength of exciton resonant absorption at 1050 nm corresponds to a density of quantum dots of approximately 4 ∙ 106 μm−2 in a layer of approximately 1 μm thickness, see 2(c).

Resulting from deposition of the quantum dot layer we observed substantial red shift of the transmission spectrum: the trapped-mode resonance moved from 860 nm to 1000 nm, i.e. in a position overlapping with the emission peak of the QDs at 1050 nm. We argue that the red shift results from the shortening of the excitation wavelength due to increased effective permittivity of the dielectric environment. In addition we observed broadening of the resonance from about 70 nm to 105 nm, which is explainable by the additional resonant absorption losses brought about by the QDs.

In summary we have provided the first experimental evidence that presence of optically pumped semiconductor quantum dots compensates Joule losses in metallic metamaterial arrays in the optical part of the spectrum. This is a very substantial step towards demonstrating a lasing spaser device. Lasing will require much higher levels of gain which could be achieved by using nanosecond optical pump pulses and/or lowering the sample temperature.

Acknowledgments

The authors are thankful to Yuan Hsing Fu and Xing-Xiang Liu for assistance with sample fabrication. Technical support from NanoCore, the Core Facilities for Nanoscience and Nanotechnology at Academia Sinica, is acknowledged. This work has been supported by the UK's Engineering and Physical Sciences Research Council via the Nanophotonics Portfolio grant, International Collaborative grant with National Taiwan University and a CA Fellowship (VAF).

References and links

1.

A. B. Kozyrev, H. Kim, and D. W. van der Weide, “Parametric amplification in left-handed transmission line media,” Appl. Phys. Lett. 88(26), 264101 (2006). [CrossRef]

2.

A. K. Popov and V. M. Shalaev, “Compensating losses in negative-index metamaterials by optical parametric amplification,” Opt. Lett. 31(14), 2169–2171 (2006). [CrossRef] [PubMed]

3.

A. D. Boardman, Y. G. Rapoport, N. King, and V. N. Malnev, “Creating stable gain in active metamaterials,” J. Opt. Soc. Am. B 24(10), A53–A61 (2007). [CrossRef]

4.

A. A. Govyadinov, V. A. Podolskiy, and M. A. Noginov, “Active metamaterials: Sign of refractive index and gain-assisted dispersion management,” Appl. Phys. Lett. 91(19), 191103 (2007). [CrossRef]

5.

A. K. Sarychev and G. Tartakovsky, “Magnetic plasmonic metamaterials in actively pumped host medium and plasmonic nanolaser,” Phys. Rev. B 75(8), 085436 (2007). [CrossRef]

6.

O. Sydoruk, E. Shamonina, and L. Solymar, “Parametric amplification in coupled magnetoinductive waveguides,” J. Phys. D Appl. Phys. 40(22), 6879–6887 (2007). [CrossRef]

7.

A. Bratkovsky, E. Ponizovskaya, S.-Y. Wang, P. Holmström, L. Thylén, Y. Fu, and H. Ågren, “A metal-wire/quantum-dot composite metamaterial with negative ε and compensated optical loss,” Appl. Phys. Lett. 93(19), 193106 (2008). [CrossRef]

8.

S. Chakrabarti, S. A. Ramakrishna, and H. Wanare, “Coherently controlling metamaterials,” Opt. Express 16(24), 19504–19511 (2008). [CrossRef] [PubMed]

9.

Z.-G. Dong, H. Liu, T. Li, Z.-H. Zhu, S.-M. Wang, J.-X. Cao, S.-N. Zhu, and X. Zhang, “Resonance amplification of left-handed transmission at optical frequencies by stimulated emission of radiation in active metamaterials,” Opt. Express 16(25), 20974–20980 (2008). [CrossRef] [PubMed]

10.

N. I. Zheludev, S. L. Prosvirnin, N. Papasimakis, and V. A. Fedotov, “Lasing spaser,” Nat. Photonics 2(6), 351–354 (2008). [CrossRef]

11.

M. Wegener, J. L. García-Pomar, C. M. Soukoulis, N. Meinzer, M. Ruther, and S. Linden, “Toy model for plasmonic metamaterial resonances coupled to two-level system gain,” Opt. Express 16(24), 19785–19798 (2008). [CrossRef] [PubMed]

12.

D. J. Bergman and M. I. Stockman, “Surface plasmon amplification by stimulated emission of radiation: quantum generation of coherent surface plasmons in nanosystems,” Phys. Rev. Lett. 90(2), 027402 (2003). [CrossRef] [PubMed]

13.

V. A. Fedotov, M. Rose, S. L. Prosvirnin, N. Papasimakis, and N. I. Zheludev, “Sharp trapped-mode resonances in planar metamaterials with a broken structural symmetry,” Phys. Rev. Lett. 99(14), 147401 (2007). [CrossRef] [PubMed]

14.

E. Plum, X.-X. Liu, V. A. Fedotov, Y. Chen, D. P. Tsai, and N. I. Zheludev, “Metamaterials: Optical Activity without Chirality,” Phys. Rev. Lett. 102(11), 113902 (2009). [CrossRef] [PubMed]

15.

J. Dintinger, S. Klein, F. Bustos, W. L. Barnes, and T. W. Ebbesen, “Strong coupling between surface plasmon-polaritons and organic molecules in subwavelength hole arrays,” Phys. Rev. B 71(3), 035424 (2005). [CrossRef]

16.

J. Dintinger, S. Klein, and T. W. Ebbesen, “Molecule–Surface Plasmon Interactions in Hole Arrays: Enhanced Absorption, Refractive Index Changes, and All-Optical Switching,” Adv. Mater. 18(10), 1267–1270 (2006). [CrossRef]

OCIS Codes
(160.3918) Materials : Metamaterials
(310.6628) Thin films : Subwavelength structures, nanostructures

ToC Category:
Metamaterials

History
Original Manuscript: April 6, 2009
Revised Manuscript: May 3, 2009
Manuscript Accepted: May 3, 2009
Published: May 5, 2009

Citation
E. Plum, V. A. Fedotov, P. Kuo, D. P. Tsai, and N. I. Zheludev, "Towards the lasing spaser: controlling metamaterial optical response with semiconductor quantum dots," Opt. Express 17, 8548-8551 (2009)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-10-8548


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References

  1. A. B. Kozyrev, H. Kim, and D. W. van der Weide, “Parametric amplification in left-handed transmission line media,” Appl. Phys. Lett. 88(26), 264101 (2006). [CrossRef]
  2. A. K. Popov and V. M. Shalaev, “Compensating losses in negative-index metamaterials by optical parametric amplification,” Opt. Lett. 31(14), 2169–2171 (2006). [CrossRef] [PubMed]
  3. A. D. Boardman, Y. G. Rapoport, N. King, and V. N. Malnev, “Creating stable gain in active metamaterials,” J. Opt. Soc. Am. B 24(10), A53–A61 (2007). [CrossRef]
  4. A. A. Govyadinov, V. A. Podolskiy, and M. A. Noginov, “Active metamaterials: Sign of refractive index and gain-assisted dispersion management,” Appl. Phys. Lett. 91(19), 191103 (2007). [CrossRef]
  5. A. K. Sarychev and G. Tartakovsky, “Magnetic plasmonic metamaterials in actively pumped host medium and plasmonic nanolaser,” Phys. Rev. B 75(8), 085436 (2007). [CrossRef]
  6. O. Sydoruk, E. Shamonina, and L. Solymar, “Parametric amplification in coupled magnetoinductive waveguides,” J. Phys. D Appl. Phys. 40(22), 6879–6887 (2007). [CrossRef]
  7. A. Bratkovsky, E. Ponizovskaya, S.-Y. Wang, P. Holmström, L. Thylén, Y. Fu, and H. Ågren, “A metal-wire/quantum-dot composite metamaterial with negative ε and compensated optical loss,” Appl. Phys. Lett. 93(19), 193106 (2008). [CrossRef]
  8. S. Chakrabarti, S. A. Ramakrishna, and H. Wanare, “Coherently controlling metamaterials,” Opt. Express 16(24), 19504–19511 (2008). [CrossRef] [PubMed]
  9. Z.-G. Dong, H. Liu, T. Li, Z.-H. Zhu, S.-M. Wang, J.-X. Cao, S.-N. Zhu, and X. Zhang, “Resonance amplification of left-handed transmission at optical frequencies by stimulated emission of radiation in active metamaterials,” Opt. Express 16(25), 20974–20980 (2008). [CrossRef] [PubMed]
  10. N. I. Zheludev, S. L. Prosvirnin, N. Papasimakis, and V. A. Fedotov, “Lasing spaser,” Nat. Photonics 2(6), 351–354 (2008). [CrossRef]
  11. M. Wegener, J. L. García-Pomar, C. M. Soukoulis, N. Meinzer, M. Ruther, and S. Linden, “Toy model for plasmonic metamaterial resonances coupled to two-level system gain,” Opt. Express 16(24), 19785–19798 (2008). [CrossRef] [PubMed]
  12. D. J. Bergman and M. I. Stockman, “Surface plasmon amplification by stimulated emission of radiation: quantum generation of coherent surface plasmons in nanosystems,” Phys. Rev. Lett. 90(2), 027402 (2003). [CrossRef] [PubMed]
  13. V. A. Fedotov, M. Rose, S. L. Prosvirnin, N. Papasimakis, and N. I. Zheludev, “Sharp trapped-mode resonances in planar metamaterials with a broken structural symmetry,” Phys. Rev. Lett. 99(14), 147401 (2007). [CrossRef] [PubMed]
  14. E. Plum, X.-X. Liu, V. A. Fedotov, Y. Chen, D. P. Tsai, and N. I. Zheludev, “Metamaterials: Optical Activity without Chirality,” Phys. Rev. Lett. 102(11), 113902 (2009). [CrossRef] [PubMed]
  15. J. Dintinger, S. Klein, F. Bustos, W. L. Barnes, and T. W. Ebbesen, “Strong coupling between surface plasmon-polaritons and organic molecules in subwavelength hole arrays,” Phys. Rev. B 71(3), 035424 (2005). [CrossRef]
  16. J. Dintinger, S. Klein, and T. W. Ebbesen, “Molecule–Surface Plasmon Interactions in Hole Arrays: Enhanced Absorption, Refractive Index Changes, and All-Optical Switching,” Adv. Mater. 18(10), 1267–1270 (2006). [CrossRef]

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