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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 2 — Jan. 18, 2010
  • pp: 1283–1288
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Magnetic-field tunable defect modes in a photonic-crystal/liquid-crystal cell

Victor Ya. Zyryanov, Sergey A. Myslivets, Vladimir A. Gunyakov, Alexander M. Parshin, Vasily G. Arkhipkin, Vasily F. Shabanov, and Wei Lee  »View Author Affiliations


Optics Express, Vol. 18, Issue 2, pp. 1283-1288 (2010)
http://dx.doi.org/10.1364/OE.18.001283


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Abstract

Light transmission spectrum of a multilayer photonic crystal with a central liquid-crystal defect layer placed between crossed polarizers has been studied. Transmittance was varied due to the magnetically induced reorientation of the nematic director from homeotropic to planar alignment. Two notable effects were observed for this scheme: the spectral shift of defect modes corresponding to the extraordinary light wave and its superposition with the ordinary one. As a result, the optical cell allows controlling the intensity of interfering defect modes by applied magnetic field.

© 2010 OSA

1. Introduction

Multilayer photonic crystal (PC) structures are widely applied in optics such as dielectric mirrors and antireflection coatings [1

1. J. D. Joannopoulos, R. D. Meade, and J. N. Winn, Photonic Crystals: Molding the Flow of Light (Princeton University Press, Princeton, 1995).

]. A new approach [2

2. E. Yablonovitch, “Inhibited spontaneous emission in solid-state physics and electronics,” Phys. Rev. Lett. 58(20), 2059–2062 (1987). [CrossRef] [PubMed]

,3

3. S. John, “Strong localization of photons in certain disordered dielectric superlattices,” Phys. Rev. Lett. 58(23), 2486–2489 (1987). [CrossRef] [PubMed]

] to the study of these structures has initiated the development of PC materials with tunable spectral properties [4

4. H. Kitzerow, “Tunable photonic crystals,” Liq. Cryst. Today 11(4), 3–7 (2002).

]. One of such materials is the PC’s with liquid-crystal (LC) structural units [5

5. K. Busch and S. John, “Liquid-crystal photonic-band-gap materials: The tunable electromagnetic vacuum,” Phys. Rev. Lett. 83(5), 967–970 (1999). [CrossRef]

14

14. G. Petriashvili, M. A. Matranga, M. P. De Santo, G. Chilaya, and R. Barberi, “Wide band gap materials as a new tuning strategy for dye doped cholesteric liquid crystals laser,” Opt. Express 17(6), 4553–4558 (2009). [CrossRef] [PubMed]

]. A high sensitivity of liquid crystals to the external stimuli allows designing various optical devices based on PC/LC structures. For example, multilayer photonic crystals with a nematic defect layer can be used to create narrow-band spectral filters with defect modes (i.e., spectral windows) removable on wavelength by applied voltage [8

8. R. Ozaki, T. Matsui, M. Ozaki, and K. Yoshino, “Electro-tunable defect mode in one-dimensional periodic structure containing nematic liquid crystal as a defect layer,” Jpn. J. Appl. Phys. 41(Part 2, No. 12B), L1482–L1484 (2002). [CrossRef]

].

As a matter of fact, a high-contrast light modulation in a multilayer PC/LC cell can be achieved by placing the cell between two crossed linear polarizers. In this scheme the spectral overlap of the extraordinary and ordinary components of defect modes with different serial numbers can result in the interference addition of their intensities as well as in the mutual quenching of both components projected to the transmission axis of the analyzer. Here we propose an experimental method to control the intensities of defect modes within the transmission spectrum of a PC/LC cell based on the aforementioned interference effect. The realization of such a tunable device regulated by magnetic field is demonstrated.

2. Experimental

The PC/LC cell (Fig. 1
Fig. 1 Schematic of experimental setup used to study transmission spectra of a PC/LC cell with a magnetically controlled nematic as a tunable defect layer. (P) and (A) are crossed linear polarizers.
) consisted of two identical dielectric mirrors, the gap between which was filled with the nematic liquid crystal 4-methoxybenzylidene-4’-butylaniline (MBBA). In the initial (i.e., unperturbed) state the nematic director n was aligned homeotropically, n || z. The thickness of the LC defect layer was L = 13.8 μm. The refractive indices of MBBA were n || = 1.765 and n = 1.552 at wavelength λ = 0.589 μm and temperature T = 25°C for the light polarized parallel and perpendicular to n, respectively. The multilayer film of each mirror comprised six layers of a high-index substance, zirconium dioxide (ZrO2), with the refractive index n 1 = 2.04 and thickness l 1 = 0.052 μm and five layers of a low-index dielectric, silicon dioxide (SiO2), with the refractive index n 2 = 1.45 and thickness l 2 = 0.102 μm. These layers were deposited in alternating sequence onto fused quartz substrates.

The PC/LC cell was placed in a steady magnetic field H || x, which enabled to reorient the nematic director smoothly through 90° within the xz-plane. Consequently, for the normally incident light the refractive index ne of extraordinary (e) wave changed from n at n || z to n || at n || x as the strength of the field increased, whereas the refractive index of ordinary (o) wave no = n remained constant. The transmission spectra of the PC/LC cell were recorded by a high-resolution spectrometer (Ocean Optics HR4000) at fixed temperature T = 25°C. Both input light to the cell and output signal to the spectrometer were transmitted via the fiber waveguides. In the experimental setup for optical transmission measurement, two Glan prisms as polarizer P and analyzer A were oriented in the way such that their transmission axes lay within the xy-plane at the angle β = ± 45° to the х-axis, respectively. Note that only polarizer P oriented along either the x- or y-axis was employed to measure the polarized extraordinary (ordinary) component of the transmission spectrum.

3. Results and discussion

The magnetic field dependence of spectral positions of the defect-mode maxima for the polarizations P || x and P || y of light normally incident on the sample are presented in Fig. 2
Fig. 2 Spectral positions of the maxima of polarized defect modes versus applied magnetic field. Experimental data for e-wave are denoted by symbols and approximated by the solid lines. Dashed lines show the invariable positions of maxima for o-wave. Threshold magnetic field H c = 6.3 kOe.
. The spectra do not change up to field strength H с = 6.3 kOe due to the threshold character of the reorientation of the nematic layer [15

15. V. K. Freedericksz and V. Zolina, “Forces causing the orientation of an anisotropic liquid,” Trans. Faraday Soc. 29, 919 (1933). [CrossRef]

]. Above the threshold H с, the spectrum of defect modes is divided into two independent, orthogonally polarized components with the wavelengths corresponding to the maxima of defect modes
λe=2Lneme,P||x,e-modes,λo=2Lnomo,P||y,o-modes,
(1)
where the integers me and mo denote the serial numbers of defect modes for e- and o-waves, respectively. For example, the serial number mo = 73 for о-mode corresponds to a spectral peak at λo = 584.4 nm. The number mo (me) rises when λo (λe) decreases and vice-versa. Spectral positions of о-modes remain invariable while the e-modes smoothly shift to the long-wavelength region. Each e-mode crosses sequentially several o-modes with various serial numbers. When an e-mode overlaps an o-mode in the crossed-polarizer scheme, their intensities are added if memo = 2k + 1 (k = 0, 1, 2…) and the modes quench each other if memo = 2k. Such behavior of polarized components of defect modes gives rise to the complex resulting transmittance as a function of the field (see Fig. 3
Fig. 3 Typical transmission spectrum of the PC/LC cell placed between crossed polarizers as a function of the reduced magnetic field.
) when the PC/LC cell is arranged between crossed polarizers. All data presented further were acquired with this scheme.

An especially promising fact is that the first maxima of transmittance (memo = 1) at various wavelengths are reached practically for the same value of applied field (see Figs. 4 and 5
Fig. 5 Magnetic-field-induced switching of the spectrum. Solid line represents the transmittance at HH c. Dashed line displays the first maximum of defect mode intensity at Н/Hc = 1.06. Dotted line is a second maximum at Н/Hc = 1.21. Dashed-dotted line is a second minimum at Н/Hc = 1.32. All curves correspond to the extrema at λo = 584.4 nm.
). It means that one can switch all spectral windows simultaneously between optically on and off states by varying the field within a small range (merely (1–1.06)H c in this study) above the threshold. Figure 6
Fig. 6 The variation of simulated transmission spectrum depending on the applied magnetic field between 6.1 and 20 kOe (Media 1). H = 6.68 kOe corresponds to Н/Hc = 1.06.
shows how the simulated spectrum changes from 6.1 to 20 kOe.

The values of applied field required to obtain a second and following maxima and minima of light transmission at various λo differ considerably (see Figs. 4 and 5). The more a serial number of a maximum (minimum) the more this distinction. This characteristic can be used to produce the optical states of a PC/LC device with different color gamuts.

4. Concluding remarks

In conclusion, we have demonstrated that the configuration with a one-dimensional PC/LC cell placed between two crossed polarizers can yield interesting spectral profile because of the vector sum of two orthogonal components belonging to different serial numbers. The defect modes and the consequent transmittance through the two-polarizer scheme can be modulated by an external field applied upon the LC infiltrated as the central defect layer in the multilayer structure. Knowing that it could be of less use in a practical device, we have employed magnetic field instead of electric field. To our best knowledge, this work is the first study on a PC/LC controlled by a magnetic field. One can certainly expect similar results by means of the application of an electric field for reorientation of the nematic director in the LC bulk.

Acknowledgments

This work was partially supported by the Russian Federal Grant No. 02.740.11.0220 and SB RAS Grant Nos. 5, 27.1 and 144. W. Lee gratefully acknowledges financial support from the National Science Council of the Republic of China (Taiwan) under Grant No. NSC 98-2923-M-033-001-MY3 dedicated to an internationally joint effort between Russia and Taiwan.

References and links

1.

J. D. Joannopoulos, R. D. Meade, and J. N. Winn, Photonic Crystals: Molding the Flow of Light (Princeton University Press, Princeton, 1995).

2.

E. Yablonovitch, “Inhibited spontaneous emission in solid-state physics and electronics,” Phys. Rev. Lett. 58(20), 2059–2062 (1987). [CrossRef] [PubMed]

3.

S. John, “Strong localization of photons in certain disordered dielectric superlattices,” Phys. Rev. Lett. 58(23), 2486–2489 (1987). [CrossRef] [PubMed]

4.

H. Kitzerow, “Tunable photonic crystals,” Liq. Cryst. Today 11(4), 3–7 (2002).

5.

K. Busch and S. John, “Liquid-crystal photonic-band-gap materials: The tunable electromagnetic vacuum,” Phys. Rev. Lett. 83(5), 967–970 (1999). [CrossRef]

6.

Y. Shimoda, M. Ozaki, and K. Yoshino, “Electric field tuning of a stop band in a reflection spectrum of synthetic opal infiltrated with nematic liquid crystal,” Appl. Phys. Lett. 79(22), 3627 (2001). [CrossRef]

7.

S. Ya. Vetrov and A. V. Shabanov, “Localized electromagnetic modes and the transmission spectrum of a one-dimensional photonic crystal with lattice defects,” Sov. Phys. JETP 93(5), 977–984 (2001). [CrossRef]

8.

R. Ozaki, T. Matsui, M. Ozaki, and K. Yoshino, “Electro-tunable defect mode in one-dimensional periodic structure containing nematic liquid crystal as a defect layer,” Jpn. J. Appl. Phys. 41(Part 2, No. 12B), L1482–L1484 (2002). [CrossRef]

9.

F. Du, Y.-Q. Lu, and S.-T. Wu, “Electrically tunable liquid-crystal photonic crystal fiber,” Appl. Phys. Lett. 85(12), 2181 (2004). [CrossRef]

10.

A. E. Miroshnichenko, I. Pinkevych, and Y. S. Kivshar, “Tunable all-optical switching in periodic structures with liquid-crystal defects,” Opt. Express 14(7), 2839–2844 (2006). [CrossRef] [PubMed]

11.

A. E. Miroshnichenko, E. Brasselet, and Y. S. Kivshar, “All-optical switching and multistability in photonic structures with liquid crystal defects,” Appl. Phys. Lett. 92(25), 253306 (2008). [CrossRef]

12.

R. Ozaki, T. Matsui, M. Ozaki, and K. Yoshino, “Electrically color-tunable defect mode lasing in one-dimensional photonic-band-gap system containing liquid crystal,” Appl. Phys. Lett. 82(21), 3593 (2003). [CrossRef]

13.

T. Nagata, T. Ohta, M. H. Song, Y. Takanishi, K. Ishikawa, J. Watanabe, T. Toyooka, S. Nishimura, and H. Takezoe, “Anomalously directed amplified spontaneous emission from a wedge-shaped cell sandwiched by cholesteric liquid crystal films,” Jpn. J. Appl. Phys. 43(No. 9A/B), L1220–L1222 (2004). [CrossRef]

14.

G. Petriashvili, M. A. Matranga, M. P. De Santo, G. Chilaya, and R. Barberi, “Wide band gap materials as a new tuning strategy for dye doped cholesteric liquid crystals laser,” Opt. Express 17(6), 4553–4558 (2009). [CrossRef] [PubMed]

15.

V. K. Freedericksz and V. Zolina, “Forces causing the orientation of an anisotropic liquid,” Trans. Faraday Soc. 29, 919 (1933). [CrossRef]

OCIS Codes
(160.3710) Materials : Liquid crystals
(230.3720) Optical devices : Liquid-crystal devices
(230.5298) Optical devices : Photonic crystals

ToC Category:
Optical Devices

History
Original Manuscript: December 4, 2009
Revised Manuscript: December 24, 2009
Manuscript Accepted: December 24, 2009
Published: January 11, 2010

Citation
Victor Ya. Zyryanov, Sergey A. Myslivets, Vladimir A. Gunyakov, Alexander M. Parshin, Vasily G. Arkhipkin, Vasily F. Shabanov, and Wei Lee, "Magnetic-field tunable defect modes in a photonic-crystal/liquid-crystal cell," Opt. Express 18, 1283-1288 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-2-1283


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References

  1. J. D. Joannopoulos, R. D. Meade, and J. N. Winn, Photonic Crystals: Molding the Flow of Light (Princeton University Press, Princeton, 1995).
  2. E. Yablonovitch, “Inhibited spontaneous emission in solid-state physics and electronics,” Phys. Rev. Lett. 58(20), 2059–2062 (1987). [CrossRef] [PubMed]
  3. S. John, “Strong localization of photons in certain disordered dielectric superlattices,” Phys. Rev. Lett. 58(23), 2486–2489 (1987). [CrossRef] [PubMed]
  4. H. Kitzerow, “Tunable photonic crystals,” Liq. Cryst. Today 11(4), 3–7 (2002).
  5. K. Busch and S. John, “Liquid-crystal photonic-band-gap materials: The tunable electromagnetic vacuum,” Phys. Rev. Lett. 83(5), 967–970 (1999). [CrossRef]
  6. Y. Shimoda, M. Ozaki, and K. Yoshino, “Electric field tuning of a stop band in a reflection spectrum of synthetic opal infiltrated with nematic liquid crystal,” Appl. Phys. Lett. 79(22), 3627 (2001). [CrossRef]
  7. S. Ya. Vetrov and A. V. Shabanov, “Localized electromagnetic modes and the transmission spectrum of a one-dimensional photonic crystal with lattice defects,” Sov. Phys. JETP 93(5), 977–984 (2001). [CrossRef]
  8. R. Ozaki, T. Matsui, M. Ozaki, and K. Yoshino, “Electro-tunable defect mode in one-dimensional periodic structure containing nematic liquid crystal as a defect layer,” Jpn. J. Appl. Phys. 41(Part 2, No. 12B), L1482–L1484 (2002). [CrossRef]
  9. F. Du, Y.-Q. Lu, and S.-T. Wu, “Electrically tunable liquid-crystal photonic crystal fiber,” Appl. Phys. Lett. 85(12), 2181 (2004). [CrossRef]
  10. A. E. Miroshnichenko, I. Pinkevych, and Y. S. Kivshar, “Tunable all-optical switching in periodic structures with liquid-crystal defects,” Opt. Express 14(7), 2839–2844 (2006). [CrossRef] [PubMed]
  11. A. E. Miroshnichenko, E. Brasselet, and Y. S. Kivshar, “All-optical switching and multistability in photonic structures with liquid crystal defects,” Appl. Phys. Lett. 92(25), 253306 (2008). [CrossRef]
  12. R. Ozaki, T. Matsui, M. Ozaki, and K. Yoshino, “Electrically color-tunable defect mode lasing in one-dimensional photonic-band-gap system containing liquid crystal,” Appl. Phys. Lett. 82(21), 3593 (2003). [CrossRef]
  13. T. Nagata, T. Ohta, M. H. Song, Y. Takanishi, K. Ishikawa, J. Watanabe, T. Toyooka, S. Nishimura, and H. Takezoe, “Anomalously directed amplified spontaneous emission from a wedge-shaped cell sandwiched by cholesteric liquid crystal films,” Jpn. J. Appl. Phys. 43(No. 9A/B), L1220–L1222 (2004). [CrossRef]
  14. G. Petriashvili, M. A. Matranga, M. P. De Santo, G. Chilaya, and R. Barberi, “Wide band gap materials as a new tuning strategy for dye doped cholesteric liquid crystals laser,” Opt. Express 17(6), 4553–4558 (2009). [CrossRef] [PubMed]
  15. V. K. Freedericksz and V. Zolina, “Forces causing the orientation of an anisotropic liquid,” Trans. Faraday Soc. 29, 919 (1933). [CrossRef]

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