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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 15 — Jul. 16, 2012
  • pp: 16974–16980
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Replicable one-dimensional non-polarizing guided mode resonance gratings under normal incidence

Muhammad Rizwan Saleem, Dandan Zheng, Benfeng Bai, Petri Stenberg, Markku Kuittinen, Seppo Honkanen, and Jari Turunen  »View Author Affiliations


Optics Express, Vol. 20, Issue 15, pp. 16974-16980 (2012)
http://dx.doi.org/10.1364/OE.20.016974


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Abstract

Polarization-insensitive guided-mode resonance (GMR) filters have significant role in applications such as optical communication systems. Here, we report the design and fabrication of two types of simple-structured one-dimensional (1D) GMR gratings with non-polarizing resonance properties under normal incidence. A single-layer rectangular-profile TiO2 grating is fabricated by electron beam lithography and reactive ion etching, which demonstrates, for the first time in experiment, almost perfect non-polarizing filtering effect with 1D grating under normal incidence. Then, a TiO2-coated polycarbonate 1D GMR grating is fabricated by nanoimprinting and atomic layer deposition, which also exhibits good non-polarizing property and the potential of low-cost mass replication of such functional devices.

© 2012 OSA

1. Introduction

Dielectric waveguide gratings with guided mode resonance (GMR) [1

1. D. Rosenblatt, A. Sharon, and A. A. Friesem, “Resonant grating waveguide structures,” IEEE. J. Quantum Electron. 33, 2038–2059 (1997). [CrossRef]

, 2

2. S. S. Wang and R. Magnusson, “Theory and applications of guided-mode resonance filters,” Appl. Opt. 32, 2606–2613 (1993). [CrossRef] [PubMed]

] have attracted much attention in the past two decades. Since GMR gratings can generate high-Q resonances, one important application is narrow-band filtering [2

2. S. S. Wang and R. Magnusson, “Theory and applications of guided-mode resonance filters,” Appl. Opt. 32, 2606–2613 (1993). [CrossRef] [PubMed]

]. Such GMR filters have been extensively studied so far by improving their optical performance such as diffraction efficiency, Q factor, passband frequency, and sideband suppression. Meanwhile, various applications based on GMR filters have been proposed, such as those in laser systems and optical communications [2

2. S. S. Wang and R. Magnusson, “Theory and applications of guided-mode resonance filters,” Appl. Opt. 32, 2606–2613 (1993). [CrossRef] [PubMed]

].

Recently, we proposed a simple design of single-layer 1D GMR gratings with non-polarizing properties under normal incidence [9

9. T. Alasaarela, D. Zheng, L. Huang, A. Priimagi, B. Bai, A. Tervonen, S. Honkanen, M. Kuittinen, and J. Turunen, “Single-layer one-dimensional nonpolarizing guided-mode resonance filters under normal incidence,” Opt. Lett. 36, 2411–2413 (2011). [CrossRef] [PubMed]

]. Preliminary test fabrication has been performed on a sinusoidal-profile non-polarizing 1D GMR grating using photoinduced polymer deformation and atomic layer deposition (ALD), which shows the potential of low-cost fabrication of such devices [9

9. T. Alasaarela, D. Zheng, L. Huang, A. Priimagi, B. Bai, A. Tervonen, S. Honkanen, M. Kuittinen, and J. Turunen, “Single-layer one-dimensional nonpolarizing guided-mode resonance filters under normal incidence,” Opt. Lett. 36, 2411–2413 (2011). [CrossRef] [PubMed]

]. However, the measured non-polarizing filtering effect was not satisfactory therein and should be further improved.

In this work, we present the design and experimental realization of a single-layer rectangular-profile non-polarizing 1D GMR grating (Type-I) and a double-layer non-polarizing 1D GMR grating (Type-II), which are both designed to work around a resonance wavelength of 850 nm under normal incidence. High-quality TiO2 Type-I GMR gratings are fabricated with electron-beam lithography (EBL) and reactive ion etching (RIE), exhibiting good non-polarizing effect. By employing nanoimprinting and ALD technique, TiO2-coated Type-II GMR gratings are realized, showing the potential of generating replicable non-polarizing GMR filters with relatively low cost, which are suitable for mass production.

2. Design of the non-polarizing GMR gratings

The investigated two types of GMR gratings are schematically depicted in Fig. 1. The Type-I GMR grating consists of a rectangular-profile TiO2 grating layer on a fused silica substrate. This design aims to verify the non-polarizing filtering effect with the simplest single-layer 1D GMR grating geometry, which has not been realized before. The Type-II grating is a TiO2-coated grating with the polycarbonate substrate replicated from a rectangular-profile master grating stamp by nanoimprinting. It aims to demonstrate the replicability of the 1D non-polarizing GMR grating. Without loss of generality, both gratings are designed to work around a resonance wavelength of 850 nm under normal incidence. The gratings at oblique incidence can also be designed easily by the same method. The electric field vector of the incident field may be parallel (TE) or perpendicular (TM) to the grating lines.

Fig. 1 Schematic of the (a) Type-I and (b) Type-II 1D non-polarizing GMR gratings.

Fig. 2 Numerically calculated TE and TM transmittance T and reflectance R of the optimized GMR gratings. (a) Type-I GMR grating with d = 540 nm, w = 395 nm, and h = 195 nm. (b) Type-II GMR grating with d = 540 nm, w = 200 nm, h = 145 nm, and t = 60 nm.

3. Fabrication of the GMR gratings

We employed ALD, EBL, and RIE techniques to fabricate the Type-I GMR grating. The fabrication procedure is schematically presented in Fig. 3.

Fig. 3 Schematic of the fabrication process of the Type-I GMR grating.

Fig. 4 SEM images of the fabricated GMR gratings. (a) The Type-I TiO2 GMR grating on a SiO2 substrate. (b), (c) and (d) are the master stamp of HSQ on a Si substrate, the replicated polycarbonate grating, and the final TiO2-coated Type-II GMR grating, respectively.

The fabrication and replication of the Type-II GMR grating were performed with the methods presented in Ref. [13

13. M. R. Saleem, P. A. Stenberg, M. B. Khan, Z. M. Khan, S. Honkanen, and J. Turunen, “Hydrogen silsesquioxane resist stamp for replication of nanophotonic components in polymers,” J. Micro/Nanolith. MEMS MOEMS 11, 013007 (2012).

]. In brief, the master stamp grating was fabricated on a Si wafer by EBL with a negative e-beam resist HSQ without any etching process. Then, replication in thermoplastic was realized using an Obducat Eitre imprinter at a temperature of 165 °C which is above the glass transition temperature Tg ∼ 150 °C of polycarbonate. After the nanoimprinting, the polycarbonate substrate was covered by an amorphous TiO2 layer by ALD process at a deposition temperature of 120 °C using commonly known precursors TiCl4 and H2O. The SEM images of the master stamp, the replicated polycarbonate grating, and the final TiO2-coated GMR grating are shown in Fig. 4(b)–(d).

It is seen from Fig. 4 that the fabricated profiles of both types of GMR gratings deviate slightly from the theoretical designs, which are trapezoidal rather than perfect rectangular ones. This is unavoidable in the practical etching (for the Type-I grating) and master grating fabrication (for the Type-II grating) processes. Furthermore, the uncertainty of the refractive indices of materials, especially that of the ALD-prepared TiO2, also sensitively influences the practical resonance properties of the GMR gratings. For these reasons, our fabrication processes, though mainly guided by the theoretical designs, still have to be tuned a little by trial and error so as to get the best structural parameters to demonstrate the non-polarizing GMR effect.

4. Resonance properties of the fabricated GMR gratings

The optical properties of the fabricated GMR grating samples were characterized by a variable angle spectroscopic ellipsometer VASE from J. A. Woollam Co. The ellipsometer was set to measure the spectral transmittance of the gratings under normal incidence of TE and TM polarized light. The collimated beam spot diameter is 3 mm, which is sufficiently smaller than the grating area of 7×7 mm2. The scanning wavelength step is 0.2 nm in measurement in the wavelength range from 700 to 1000 nm. The measured zeroth-order transmittance spectra of the two fabricated grating samples are plotted in Fig. 5, both of which show the non-polarizing GMR effect around a wavelength of 840 nm. The small shift of the resonance wavelength (10 nm from the expected 850 nm) is mainly due to the deviation of the practical grating profiles from the designed ones, as mentioned above. In principle, we can tune the resonance wavelength to 850 nm by further parameter adjustment (for example, by increasing the period of the grating) in the fabrication process. But the current fabrication results already demonstrate well the expected non-polarizing GMR effect at a wavelength very close to the designed one. Furthermore, by comparing Fig. 5 with Fig. 2, we can see very good correspondence between theory and experiment; the main resonance features such as the lineshapes, the resonance linewidths, and the diffraction efficiencies are well reproduced in experiment. These show the reliability of the theoretical design and the fabrication processes. The measurement results are also the first experimental demonstration so far on the realization of polarization-insensitive 1D GMR gratings under normal incidence.

Fig. 5 Measured transmittance spectra of the fabricated (a) Type-I and (b) Type-II GMR grating samples, demonstrating the non-polarizing GMR effect under normal incidence.

By inspecting the spectra of the Type-I GMR grating in Fig. 5(a), we can see that the TE and TM resonance peaks are almost at the same wavelength, with a small difference of 2.4 nm; the linewidths of the two resonances are also very close to each other, with a full width at half maximum of 30 nm for TE and 38 nm for TM. Therefore, the Type-I grating exhibits the non-polarizing GMR effect almost perfectly. The Type-II grating also demonstrates very good non-polarizing effect (with only 1.4 nm difference between the TE and TM peak wavelengths), but has a larger difference between the TE and TM resonance linewidths and the sidebands are not as well suppressed, as seen in Fig. 5(b). The structure needs to be further optimized to improve the filtering property (for example, by adding underneath layers to suppress the sidebands). Nevertheless, owing to the easier fabrication process and much lower manufacturing cost, the Type-II grating has good perspective for practical applications. We are taking further study to improve its resonance performance while maintaining the relatively simple geometry.

5. Conclusion

We have presented the design and fabrication of two types of 1D GMR gratings with simple geometries, which demonstrate polarization-insensitive GMRs under normal incidence. The Type-I single-layer rectangular-profile TiO2 grating is fabricated by employing ALD, EBL, and RIE techniques, which shows almost perfect non-polarizing property. The Type-II grating is an TiO2-coated polycarbonate GMR grating manufactured by nanoimprinting and ALD, without any etching process. Both types of 1D non-polarizing GMR gratings are realized for the first time in experiment so far, which show the potential of low-cost mass production of such functional devices for practical applications, for example, in enhancing fluorescence in biosensors.

Acknowledgment

We acknowledge the support by the National Natural Science Foundation of China (Projects No. 11004119 and No. 61161130005), the Academy of Finland (Projects No. 128420 and No. 250968), the Strategic Funding Initiative TAILOR of the University of Eastern Finland, and the Higher Education Commission, Pakistan.

References and links

1.

D. Rosenblatt, A. Sharon, and A. A. Friesem, “Resonant grating waveguide structures,” IEEE. J. Quantum Electron. 33, 2038–2059 (1997). [CrossRef]

2.

S. S. Wang and R. Magnusson, “Theory and applications of guided-mode resonance filters,” Appl. Opt. 32, 2606–2613 (1993). [CrossRef] [PubMed]

3.

D. Lacour, G. Granet, J-P. Plumey, and A. Mure-Ravaud, “Polarization independence of a one dimensional grating in conical mounting,” J. Opt. Soc. Am. A. 20, 1546–1552 (2003). [CrossRef]

4.

B. Cunningham, B. Lin, J. Qiu, P. Li, J. Pepper, and B. Hugh, “A plastic colorimetric resonant optical biosensor for multiparallel detection of label-free biochemical interactions,” Sens. Actuators 85, 219–226 (2002). [CrossRef]

5.

P. Karvinen, T. Nuutinen, J. Rahomäki, O. Hyvärinen, and P. Vahimaa, “Strong fluorescence-signal gain with single-excitation-enhancing and emission-directing nanostructured diffraction grating,” Opt. Lett. 34, 3208–3210 (2009). [CrossRef] [PubMed]

6.

G. Niederer, W. Nakagawa, and H. P. Herzig, “Design and characterization of a tunable polarization-independent resonanct grating filter,” Opt. Express 13, 2196–2200 (2005). [CrossRef] [PubMed]

7.

D. W. Peters, R. R. Boye, J. R. Wendt, R. A. Kellogg, S. A. Kemme, T. R. Carter, and S. Samora, “Demonstration of polarization-independent resonant subwavelength grating filter arrays,” Opt. Lett. 35, 3201–3203 (2010). [CrossRef] [PubMed]

8.

A.-L. Fehrembach and A. Sentenac, “Unpolarized narrow-band filtering with resonant gratings,” Appl. Phys. Lett. 86, 121105 (2005). [CrossRef]

9.

T. Alasaarela, D. Zheng, L. Huang, A. Priimagi, B. Bai, A. Tervonen, S. Honkanen, M. Kuittinen, and J. Turunen, “Single-layer one-dimensional nonpolarizing guided-mode resonance filters under normal incidence,” Opt. Lett. 36, 2411–2413 (2011). [CrossRef] [PubMed]

10.

L. Li, “New formulation of the Fourier modal method for crossed surface-relief gratings,” J. Opt. Soc. Am. A 14, 2758–2767 (1997). [CrossRef]

11.

D. Delbeke, R. Baets, and P. Muys, “Polarization-selective beam splitter based on a highly efficient simple binary diffraction grating,” Appl. Opt. 43, 6157–6165 (2004). [CrossRef] [PubMed]

12.

T. Clausnitzer, A. V. Tishchenko, E. B. Kley, J. Fuchs, D. Schelle, O. Parriaux, and U. Kroll, “Narrowband, polarization-independent free-space wave notch filter,” J. Opt. Soc. Am. A 22, 2799–2803 (2005). [CrossRef]

13.

M. R. Saleem, P. A. Stenberg, M. B. Khan, Z. M. Khan, S. Honkanen, and J. Turunen, “Hydrogen silsesquioxane resist stamp for replication of nanophotonic components in polymers,” J. Micro/Nanolith. MEMS MOEMS 11, 013007 (2012).

OCIS Codes
(050.2770) Diffraction and gratings : Gratings
(230.7400) Optical devices : Waveguides, slab
(310.2790) Thin films : Guided waves
(350.2460) Other areas of optics : Filters, interference

ToC Category:
Diffraction and Gratings

History
Original Manuscript: May 9, 2012
Revised Manuscript: June 17, 2012
Manuscript Accepted: July 3, 2012
Published: July 11, 2012

Citation
Muhammad Rizwan Saleem, Dandan Zheng, Benfeng Bai, Petri Stenberg, Markku Kuittinen, Seppo Honkanen, and Jari Turunen, "Replicable one-dimensional non-polarizing guided mode resonance gratings under normal incidence," Opt. Express 20, 16974-16980 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-15-16974


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References

  1. D. Rosenblatt, A. Sharon, and A. A. Friesem, “Resonant grating waveguide structures,” IEEE. J. Quantum Electron.33, 2038–2059 (1997). [CrossRef]
  2. S. S. Wang and R. Magnusson, “Theory and applications of guided-mode resonance filters,” Appl. Opt.32, 2606–2613 (1993). [CrossRef] [PubMed]
  3. D. Lacour, G. Granet, J-P. Plumey, and A. Mure-Ravaud, “Polarization independence of a one dimensional grating in conical mounting,” J. Opt. Soc. Am. A.20, 1546–1552 (2003). [CrossRef]
  4. B. Cunningham, B. Lin, J. Qiu, P. Li, J. Pepper, and B. Hugh, “A plastic colorimetric resonant optical biosensor for multiparallel detection of label-free biochemical interactions,” Sens. Actuators85, 219–226 (2002). [CrossRef]
  5. P. Karvinen, T. Nuutinen, J. Rahomäki, O. Hyvärinen, and P. Vahimaa, “Strong fluorescence-signal gain with single-excitation-enhancing and emission-directing nanostructured diffraction grating,” Opt. Lett.34, 3208–3210 (2009). [CrossRef] [PubMed]
  6. G. Niederer, W. Nakagawa, and H. P. Herzig, “Design and characterization of a tunable polarization-independent resonanct grating filter,” Opt. Express13, 2196–2200 (2005). [CrossRef] [PubMed]
  7. D. W. Peters, R. R. Boye, J. R. Wendt, R. A. Kellogg, S. A. Kemme, T. R. Carter, and S. Samora, “Demonstration of polarization-independent resonant subwavelength grating filter arrays,” Opt. Lett.35, 3201–3203 (2010). [CrossRef] [PubMed]
  8. A.-L. Fehrembach and A. Sentenac, “Unpolarized narrow-band filtering with resonant gratings,” Appl. Phys. Lett.86, 121105 (2005). [CrossRef]
  9. T. Alasaarela, D. Zheng, L. Huang, A. Priimagi, B. Bai, A. Tervonen, S. Honkanen, M. Kuittinen, and J. Turunen, “Single-layer one-dimensional nonpolarizing guided-mode resonance filters under normal incidence,” Opt. Lett.36, 2411–2413 (2011). [CrossRef] [PubMed]
  10. L. Li, “New formulation of the Fourier modal method for crossed surface-relief gratings,” J. Opt. Soc. Am. A14, 2758–2767 (1997). [CrossRef]
  11. D. Delbeke, R. Baets, and P. Muys, “Polarization-selective beam splitter based on a highly efficient simple binary diffraction grating,” Appl. Opt.43, 6157–6165 (2004). [CrossRef] [PubMed]
  12. T. Clausnitzer, A. V. Tishchenko, E. B. Kley, J. Fuchs, D. Schelle, O. Parriaux, and U. Kroll, “Narrowband, polarization-independent free-space wave notch filter,” J. Opt. Soc. Am. A22, 2799–2803 (2005). [CrossRef]
  13. M. R. Saleem, P. A. Stenberg, M. B. Khan, Z. M. Khan, S. Honkanen, and J. Turunen, “Hydrogen silsesquioxane resist stamp for replication of nanophotonic components in polymers,” J. Micro/Nanolith. MEMS MOEMS11, 013007 (2012).

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