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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 1 — Jan. 13, 2014
  • pp: 925–930
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Polarization-independent and fast tunable microlens array based on blue phase liquid crystals

Shih-Hung Lin, Lin-Song Huang, Chi-Huang Lin, and Chie-Tong Kuo  »View Author Affiliations


Optics Express, Vol. 22, Issue 1, pp. 925-930 (2014)
http://dx.doi.org/10.1364/OE.22.000925


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Abstract

This work investigates a polarization-independent and fast response microlens array. This array is composed of a concave polymer microlens array and blue phase liquid crystals (BPLCs). The microlens array can be either positive or negative, depending on the birefringence of the BPLCs. The experimental results show that the microlens array is fast switched between positive and negative focal lengths via controlling the electric fields, and the response time is a few hundred microseconds. Additionally, the focusing efficiency is independent of the polarization of the incident light.

© 2014 Optical Society of America

1. Introduction

Tunable-focus liquid crystal (LC) lenses and LC microlens arrays have been of interest and investigated widely for an increasing variety of optoelectronic applications including 3D displays, image processing, photonic devices, eye glasses and optical communications [1

1. Y.-P. Huang, C.-W. Chen, T.-C. Shen, and J.-F. Huang, “Autostereoscopic 3D display with scanning multi-electrode driven liquid crystal (MeD-LC) lens,” J. 3D Res. 1(1), 39–42 (2010). [CrossRef]

6

6. Z. He, T. Nose, and S. Sato, “Molecular orientations and optical transmission properties of liquid crystal cells with slit-patterned electrodes,” Jpn. J. Appl. Phys. 36(1), 1178–1184 (1997). [CrossRef]

]. LC lenses have been fabricated using Fresnel zone plates [4

4. K.-C. Lo, J.-D. Wang, C.-R. Lee, and T.-S. Mo, “Electrically controllable and polarization-independent Fresnel zone-plate in a circularly symmetric hybrid-aligned liquid crystal film with a photoconductive polymer layer,” Appl. Phys. Lett. 91(18), 181104 (2007). [CrossRef]

,7

7. C.-H. Lin, Y.-Y. Wang, and C.-W. Hsieh, “Polarization-independent and high-diffraction-efficiency Fresnel lenses based on blue phase liquid crystals,” Opt. Lett. 36(4), 502–504 (2011). [CrossRef] [PubMed]

], patterned electrodes [1

1. Y.-P. Huang, C.-W. Chen, T.-C. Shen, and J.-F. Huang, “Autostereoscopic 3D display with scanning multi-electrode driven liquid crystal (MeD-LC) lens,” J. 3D Res. 1(1), 39–42 (2010). [CrossRef]

,3

3. C. J. Hsu and C. R. Sheu, “Using photopolymerization to achieve tunable liquid crystal lenses with coaxial bifocals,” Opt. Express 20(4), 4738–4746 (2012). [CrossRef] [PubMed]

,8

8. Y.-H. Lin, H.-S. Chen, H.-C. Lin, Y.-S. Tsou, H.-K. Hsu, and W.-Y. Li, “Polarizer-free and fast response microlens arrays using polymer-stabilized blue phase liquid crystals,” Appl. Phys. Lett. 96(11), 113505 (2010). [CrossRef]

], polymer dispersed LCs [9

9. H. Ren, Y.-H. Lin, Y.-H. Fan, and S.-T. Wu, “Polarization-independent phase modulation using a polymer-dispersed liquid crystal,” Appl. Phys. Lett. 86(14), 141110 (2005). [CrossRef]

], polymer-stabilized LCs [10

10. V. Presnyakov, K. E. Asatryan, T. V. Galstian, and A. Tork, “Polymer-stabilized liquid crystal for tunable microlens applications,” Opt. Express 10(17), 865–870 (2002). [CrossRef] [PubMed]

,11

11. M. Xu, Z. Zhou, H. Ren, S. H. Lee, and Q. Wang, “A microlens array based on polymer network liquid crystal,” Appl. Phys. Lett. 113(5), 053105 (2013).

], and surface relief structures [2

2. Y.-J. Lee, J.-H. Baek, Y. Kim, J. U. Heo, Y.-K. Moon, J. S. Gwag, C.-J. Yu, and J.-H. Kim, “Polarizer-free liquid crystal display with electrically switchable microlens array,” Opt. Express 21(1), 129–134 (2013). [CrossRef] [PubMed]

,5

5. S. Sato, “Liquid-crystal lens-cells with variable focal length,” Jpn. J. Appl. Phys. 18(9), 1679–1684 (1979). [CrossRef]

,12

12. Y. Choi, J.-H. Park, J.-H. Kim, and S.-D. Lee, “Fabrication of a focal length variable microlens array based on a nematic liquid crystal,” Opt. Mater. 21(1–3), 643–646 (2002).

15

15. L. G. Commander, S. E. Day, and D. R. Selviah, “Variable focal length microlenses,” Opt. Commun. 177(1–6), 157–170 (2000). [CrossRef]

]. Refractive index modulation can be utilized for tuning many LC devices, and is dependent on the molecular orientation and the polarization direction of the incident light. Therefore, fabricating a LC lens which possesses the characteristic of polarization independence is crucial. In the future, the optoelectronic devices have to be upgraded and developed to allow faster electro-optic response time and to simplify the fabrication process. So the response time and the fabrication process of the LC microlens are also two of the factors that need to be considered.

In recent years, blue phase liquid crystals (BPLCs) have been widely investigated because of their unique characteristics of optical isotropy, selective Bragg reflection and fast response time (in the range of sub-millisecond), and they do not require the molecular alignment layer [7

7. C.-H. Lin, Y.-Y. Wang, and C.-W. Hsieh, “Polarization-independent and high-diffraction-efficiency Fresnel lenses based on blue phase liquid crystals,” Opt. Lett. 36(4), 502–504 (2011). [CrossRef] [PubMed]

,8

8. Y.-H. Lin, H.-S. Chen, H.-C. Lin, Y.-S. Tsou, H.-K. Hsu, and W.-Y. Li, “Polarizer-free and fast response microlens arrays using polymer-stabilized blue phase liquid crystals,” Appl. Phys. Lett. 96(11), 113505 (2010). [CrossRef]

,16

16. Y. Hisakado, H. Kikichi, T. Nagamura, and T. Kajiyama, “Large Electro-optic Kerr Effect in Polymer-Stabilized Liquid-Crystalline Blue Phases,” Adv. Mater. 17(1), 96–98 (2005). [CrossRef]

21

21. K. M. Chen, S. Gauza, H. Xianyu, and S. T. Wu, “Submillisecond Gray-Level Response Time of a Polymer-Stabilized Blue-Phase Liquid Crystal,” J. Disp. Technol. 6(2), 49–51 (2010). [CrossRef]

]. The blue phase can be found at temperature range between the cholesteric phase and the isotropic phase. In an external electric field, the BPLCs exhibit the insignificant local reorientation of LC directors, the reorientational transformation of crystals, and electrostriction, all of which lead to the Bragg reflection shift, phase shift and the Kerr effect [16

16. Y. Hisakado, H. Kikichi, T. Nagamura, and T. Kajiyama, “Large Electro-optic Kerr Effect in Polymer-Stabilized Liquid-Crystalline Blue Phases,” Adv. Mater. 17(1), 96–98 (2005). [CrossRef]

18

18. J. Yan, H.-C. Cheng, S. Gauza, Y. Li, M. Jiao, L. Rao, and S.-T. Wu, “Extended Kerr effect of polymer-stabilized blue-phase liquid crystals,” Appl. Phys. Lett. 96(7), 071105 (2010). [CrossRef]

]. Based on the above characteristics, the BPLCs have been developed to optoelectronic applications, such as tunable photonic crystals [7

7. C.-H. Lin, Y.-Y. Wang, and C.-W. Hsieh, “Polarization-independent and high-diffraction-efficiency Fresnel lenses based on blue phase liquid crystals,” Opt. Lett. 36(4), 502–504 (2011). [CrossRef] [PubMed]

,17

17. S. Y. Lu and L. C. Chien, “Electrically switched color with polymer-stabilized blue-phase liquid crystals,” Opt. Lett. 35(4), 562–564 (2010). [CrossRef] [PubMed]

], photonic devices of phase modulation [7

7. C.-H. Lin, Y.-Y. Wang, and C.-W. Hsieh, “Polarization-independent and high-diffraction-efficiency Fresnel lenses based on blue phase liquid crystals,” Opt. Lett. 36(4), 502–504 (2011). [CrossRef] [PubMed]

,8

8. Y.-H. Lin, H.-S. Chen, H.-C. Lin, Y.-S. Tsou, H.-K. Hsu, and W.-Y. Li, “Polarizer-free and fast response microlens arrays using polymer-stabilized blue phase liquid crystals,” Appl. Phys. Lett. 96(11), 113505 (2010). [CrossRef]

,19

19. J. Yan, Y. Li, and S.-T. Wu, “High-efficiency and fast-response tunable phase grating using a blue phase liquid crystal,” Opt. Lett. 36(8), 1404–1406 (2011). [CrossRef] [PubMed]

], and LC displays [20

20. Z. Ge, S. Gauza, M. Jiao, H. Xianyu, and S.-T. Wu, “Electro-optics of polymer-stabilized blue phase liquid crystal displays,” Appl. Phys. Lett. 94(10), 101104 (2009). [CrossRef]

].

In this study, we propose a simple method of fabricating microlens arrays based on a surface relief structure with the BPLC material. The BPLC microlens has the polarization-independent feature, has fast tuned focal lengths, and can be fast switched between positive and negative lenses via controlling the strength of the electric fields.

2. Operating principle

Fig. 1 Basic configuration and operating principles of the BPLC microlens array without electric state (left side) and with electric state (right side).
Figure 1 shows a schematic diagram and the operating principles of the BPLC microlens array. The cell of the microlens array is fabricated using two ITO glasses. On the bottom substrate of the cell is the deposited concave polymer structure, as shown in Fig. 1. The two glass substrates are separated by two 3.5 μm-thick plastic spacers. The cavities of the microlens cell are filled with BPLCs. In a state in which an external field is not applied, the optical refractive-index ellipsoid of BPLCs is circular. Owing to the orientation of BPLCs in the cell being optically isotropic, its refractive index at zero applied voltage is given by niso = (ne + 2no)/3, where ne and no are the extraordinary and ordinary refractive indices of the LC host, respectively. When voltage is applied to the BPLC layer, the BPLCs will exhibit birefringence due to the extended Kerr effect [16

16. Y. Hisakado, H. Kikichi, T. Nagamura, and T. Kajiyama, “Large Electro-optic Kerr Effect in Polymer-Stabilized Liquid-Crystalline Blue Phases,” Adv. Mater. 17(1), 96–98 (2005). [CrossRef]

,18

18. J. Yan, H.-C. Cheng, S. Gauza, Y. Li, M. Jiao, L. Rao, and S.-T. Wu, “Extended Kerr effect of polymer-stabilized blue-phase liquid crystals,” Appl. Phys. Lett. 96(7), 071105 (2010). [CrossRef]

]. Therefore, the refractive-index ellipsoid of BPLCs is transformed from a spherical to an ellipsoidal shape, where the optic axis of ellipsoidal refractive-index ellipsoid is parallel to the electric field [18

18. J. Yan, H.-C. Cheng, S. Gauza, Y. Li, M. Jiao, L. Rao, and S.-T. Wu, “Extended Kerr effect of polymer-stabilized blue-phase liquid crystals,” Appl. Phys. Lett. 96(7), 071105 (2010). [CrossRef]

,20

20. Z. Ge, S. Gauza, M. Jiao, H. Xianyu, and S.-T. Wu, “Electro-optics of polymer-stabilized blue phase liquid crystal displays,” Appl. Phys. Lett. 94(10), 101104 (2009). [CrossRef]

]. When the normal incident light propagates along the optic axis of the BPLCs, the probe light will experience an effective refractive index no(V) which depends on the magnitude of the applied voltage (V). Based on the above electro-optical properties of the BPLCs, the refractive index of BPLCs can be modulated from a range of niso to no(V) by the applied voltage.

3. Sample preparation and experimental setups

Fig. 2 The SEM images of the concave-shaped surface relief structure.
A concave polymer microlens array is deposited on the bottom ITO glass substrate. The first step is to spin-coat UV-curable polymer (Norland, NOA81) onto an ITO glass substrate at the rate of 3000 rpm for 25 sec. The second step is to produce a concave-shaped surface relief structure of the polymer by employing a uniform UV light through a photomask to expose onto the UV-curable polymer film, as shown in Fig. 2(a). The UV light (λ = 365 nm), with an intensity of 30 mW/cm2, irradiates the deposited polymer for 19 min. The photomask is a circular array pattern of the metal coating with a diameter and pitch of 100 μm and 200 μm, respectively. The circular pattern of the photomask is designed to resist the UV light irradiating onto to UV-curable polymer film. Because the UV-curable polymer film is spatially-modulated exposed by using UV light with the photomask, it results in the monomeric density generating an uneven distribution. For the above reasons, there is a diffusion shift of the monomers from the unirradiated to the irradiated regions [2

2. Y.-J. Lee, J.-H. Baek, Y. Kim, J. U. Heo, Y.-K. Moon, J. S. Gwag, C.-J. Yu, and J.-H. Kim, “Polarizer-free liquid crystal display with electrically switchable microlens array,” Opt. Express 21(1), 129–134 (2013). [CrossRef] [PubMed]

,22

22. S. Piazzolla and B. K. Jenkins, “Dynamics during holographic exposure in photopolymers for single and multiplexed gratings,” J. Mod. Opt. 46(15), 2079–2110 (1999).

]. The monomers move to the illuminated regions and polymerize to form the concave-shaped surface structure on the bottom substrate. Figure 2(b) shows the profile image of a concave-shaped surface relief structure. The diameter and center depth of the concave structure are 140 μm and 7.3 μm, respectively.

The BPLC mixture used in the experiment includes a nematic LC (Fusol material co., HTW114200-100; ne = 1.77 and no = 1.51) and a left-handed chiral dopant (Merck, S811) at a ratio of 65:35 wt%. The BPLC microlens cell is heated up to above its clear point and then is cooled from the isotropic state down to the blue phase at a cooling rate of 0.01 °C/min by controlling the temperature. The temperature range of the blue phase is from 44 to 36 °C. In our experiment, the BP in the microlens array is 40 °C.

Fig. 3 Experimental setup for measuring the focusing properties of the BPLC microlens array.
Figure 3 depicts the experimental setup for measuring the focusing properties and response times of the BPLC microlens array by using a CCD camera and a photo detector. A circularly polarized laser beam (from a He-Ne laser, wavelength: 633 nm) is magnified with a beam expander, which passes through a polarizer to change the polarization direction of the normal incident light and then illuminates the cell of the BPLC microlens array. Utilizing an imaging lens (L3) allows the transmitted light from the sample to be focused on the CCD camera. The CCD camera is placed near the position of the focal plane in order to analyze the intensity distribution of focused light of the microlens array. The sample is linearly moved along the optical path in order to determine the effective focal length.

4. Results and discussion

Fig. 4 (a) Polarizing microscopic image of the BPLC microlens array without applied voltage. The focused image of the BPLC microlens array at (b) V = 0, (c) V = 70 V, (d) V = 150 V, respectively.
Figure 4(a) shows the polarizing microscopic image of the BPLC microlens array at zero applied voltage. The domain diameters of the platelet texture in the BPLC ranges from 100 to 200 μm at zero applied voltage. Because of the larger domain size, the scattering effect from the multi-domain is weak in the microlens array. Obviously, the microlens array can converge the incident light, as displayed in Fig. 4(a). Figures 4(b)4(d) show focused images of the microlens array that are taken from the CCD camera at various applied voltages. At zero applied voltage, all focal points at the focal plane are uniform and consistent, and the convergent performance of the microlens can be clearly displayed, as shown in Fig. 4(b). When the voltage is increased to 70 V, the focal points gradually disappear and exhibit uniform intensity, as shown in Fig. 4(c). The BPLC effective refractive index no(V) matches the polymer refractive index np, resulting in the defocusing of the light. Figure 4(d) illustrates that when a voltage of 150 V is applied to the BPLC layer, the transmitted light from the microlens is diverged due to no(V) < np. Therefore, the focus of the microlens deteriorates significantly.

The tuning of the focal length can be achieved by utilizing the difference of the refractive indices between the BPLC and concave polymer structure. Owing to the concave shape of the polymer structure, the BPLC layer resembles a plano-convex lens. On the basis of Lensmaker’s formula, the focal length is determined by the curvature radius (r) of the surface relief structure, and the refractive index difference (Δn = no(V)−np) between the BPLC layer and the polymer, as f = r/(no(V)−np). In this experiment, the curvature radius of the surface relief structure r is about 138 μm, and the refractive index of the concave polymer structure np is 1.56. However, the measured focal length of the microlens is shown in Fig. 5.
Fig. 5 Measured focal length of the BPLC microlens as a function of applied voltage.
At V = 0, the refractive index of the BPLCs is larger than that of the polymer, and the focal length of the microlens is about 4.0 mm. When the difference of the refractive index between the BPLC layer and the polymer is the greatest, the focal length can be the shortest. After the applied voltage is higher than the threshold Vth ~20 V, the focal length increases via the increase in the applied voltage in the positive lens. Because the effective refractive index no(V) of the BPLCs equals the refractive index np of the polymer at the voltage range between 60 V and 70 V, there is no refracted light in the concave-shaped surface relief structure. Therefore, the focal length is infinite. In the negative lens, the BPLC refractive index is smaller than the polymer refractive index (no(V) < np), and the focal length gradually decreases from −12.0 mm to −3.7 mm by increasing applied voltage from 80 to 150 V. The tunability of the focal length is in the range of 2 mm in the positive lens and 8.3 mm in the negative lens. Therefore, by varying the voltage, the focal length can be continuously tuned between the positive lens and the negative lens. Under a high applied voltage, the BPLC effective index no(V) is gradually saturated and close to no. In the process of tuning the focal length, the matching of the refractive index difference between the BPLCs and polymer plays an important role. Therefore, the microlens may be formed via either a convex or a concave lens, depending on the difference values between np and no(V).

Fig. 6 (a) Measurement of intensity of focused light for single BPLC microlens under applied voltage V = 30 V with various polarization directions of the incident light. (b) and (c) Measurement of response times for the BPLC microlenses (red lines) with the square-wave voltage (blue lines) switched between 0 and 80 V.
Figure 6(a) plots the intensity of the focused light at various polarization directions of the incident light. Under an applied voltage of 30 V, the photo detector is placed on the focal point of a BPLC microlens and measures the intensity of the focused light. As shown in Fig. 6(a), the BPLC microlens exhibits a focusing effect of polarization independence. As the polarization direction of the incident light changes, the intensity of the focal point remains constant. It is attributable to the optical isotropy of the BPLCs at zero applied voltage. Under a vertical electric field, the electrically tunable BPLC refractive index is insensitive to variation in polarization, because the propagation of a normal incident light is along the optic axis of the birefringence of the BPLC. This result implies that the microlens exhibits the polarization-independent feature.

The response time of the BPLCs depends on the strength of the electric field [21

21. K. M. Chen, S. Gauza, H. Xianyu, and S. T. Wu, “Submillisecond Gray-Level Response Time of a Polymer-Stabilized Blue-Phase Liquid Crystal,” J. Disp. Technol. 6(2), 49–51 (2010). [CrossRef]

]. Therefore, the microlens is a thin cell gap, which can increase the electric field strength of the BPLC layer, and then it decreases the response time of the microlens. In this experiment, the thickness of the BPLC layer is less than 11 μm, so it can gain fast response times without using polymer network stabilized BPLCs. The response times are measured via switching the intensity of focused light of the microlens between convergence and divergence. The intensity of focused light of the microlens is measured at a focal length of −12 mm by switching an applied voltage which is 80 V with a square wave of 1 KHz. The measured response times of the BPLC microlens are at a rise time τrise of:0.86 msec and a decay time τdecay of:0.74 msec, as shown in Fig. 6(b) and 6(c), respectively. The response times of the BPLC microlens are much shorter than those of the conventional nematic LC microlens, which are of the order of milliseconds [2

2. Y.-J. Lee, J.-H. Baek, Y. Kim, J. U. Heo, Y.-K. Moon, J. S. Gwag, C.-J. Yu, and J.-H. Kim, “Polarizer-free liquid crystal display with electrically switchable microlens array,” Opt. Express 21(1), 129–134 (2013). [CrossRef] [PubMed]

,11

11. M. Xu, Z. Zhou, H. Ren, S. H. Lee, and Q. Wang, “A microlens array based on polymer network liquid crystal,” Appl. Phys. Lett. 113(5), 053105 (2013).

,13

13. Y.-H. Fan, H. Ren, X. Liang, H. Wang, and S.-T. Wu, “Liquid crystal microlens arrays with switchable positive and negative focal lengths,” J. Disp. Technol. 1(1), 151–156 (2005). [CrossRef]

,14

14. H. Ren, Y.-H. Fan, and S.-T. Wu, “Liquid-crystal microlens arrays using patterned polymer networks,” Opt. Lett. 29(14), 1608–1610 (2004). [CrossRef] [PubMed]

].

5. Conclusion

In summary, this study successfully demonstrates a polarization-independent microlens array based on BPLCs. In this method of fabricating a microlens array, the BPLC material can be applied in the microlens array device without giving the molecular alignment layer. Therefore it simplifies the fabrication process, and it also promotes the properties of polarization independence and fast response. In addition to the advantage that the microlens can be tuned by the focal lengths, the microlens can also be switched between positive and negative lenses. The microlens array has potential in the future optoelectronic device applications.

Acknowledgments

This work is supported by the National Science Council in Taiwan (Contract No. NSC 102-2112-M-110-007).

References and links

1.

Y.-P. Huang, C.-W. Chen, T.-C. Shen, and J.-F. Huang, “Autostereoscopic 3D display with scanning multi-electrode driven liquid crystal (MeD-LC) lens,” J. 3D Res. 1(1), 39–42 (2010). [CrossRef]

2.

Y.-J. Lee, J.-H. Baek, Y. Kim, J. U. Heo, Y.-K. Moon, J. S. Gwag, C.-J. Yu, and J.-H. Kim, “Polarizer-free liquid crystal display with electrically switchable microlens array,” Opt. Express 21(1), 129–134 (2013). [CrossRef] [PubMed]

3.

C. J. Hsu and C. R. Sheu, “Using photopolymerization to achieve tunable liquid crystal lenses with coaxial bifocals,” Opt. Express 20(4), 4738–4746 (2012). [CrossRef] [PubMed]

4.

K.-C. Lo, J.-D. Wang, C.-R. Lee, and T.-S. Mo, “Electrically controllable and polarization-independent Fresnel zone-plate in a circularly symmetric hybrid-aligned liquid crystal film with a photoconductive polymer layer,” Appl. Phys. Lett. 91(18), 181104 (2007). [CrossRef]

5.

S. Sato, “Liquid-crystal lens-cells with variable focal length,” Jpn. J. Appl. Phys. 18(9), 1679–1684 (1979). [CrossRef]

6.

Z. He, T. Nose, and S. Sato, “Molecular orientations and optical transmission properties of liquid crystal cells with slit-patterned electrodes,” Jpn. J. Appl. Phys. 36(1), 1178–1184 (1997). [CrossRef]

7.

C.-H. Lin, Y.-Y. Wang, and C.-W. Hsieh, “Polarization-independent and high-diffraction-efficiency Fresnel lenses based on blue phase liquid crystals,” Opt. Lett. 36(4), 502–504 (2011). [CrossRef] [PubMed]

8.

Y.-H. Lin, H.-S. Chen, H.-C. Lin, Y.-S. Tsou, H.-K. Hsu, and W.-Y. Li, “Polarizer-free and fast response microlens arrays using polymer-stabilized blue phase liquid crystals,” Appl. Phys. Lett. 96(11), 113505 (2010). [CrossRef]

9.

H. Ren, Y.-H. Lin, Y.-H. Fan, and S.-T. Wu, “Polarization-independent phase modulation using a polymer-dispersed liquid crystal,” Appl. Phys. Lett. 86(14), 141110 (2005). [CrossRef]

10.

V. Presnyakov, K. E. Asatryan, T. V. Galstian, and A. Tork, “Polymer-stabilized liquid crystal for tunable microlens applications,” Opt. Express 10(17), 865–870 (2002). [CrossRef] [PubMed]

11.

M. Xu, Z. Zhou, H. Ren, S. H. Lee, and Q. Wang, “A microlens array based on polymer network liquid crystal,” Appl. Phys. Lett. 113(5), 053105 (2013).

12.

Y. Choi, J.-H. Park, J.-H. Kim, and S.-D. Lee, “Fabrication of a focal length variable microlens array based on a nematic liquid crystal,” Opt. Mater. 21(1–3), 643–646 (2002).

13.

Y.-H. Fan, H. Ren, X. Liang, H. Wang, and S.-T. Wu, “Liquid crystal microlens arrays with switchable positive and negative focal lengths,” J. Disp. Technol. 1(1), 151–156 (2005). [CrossRef]

14.

H. Ren, Y.-H. Fan, and S.-T. Wu, “Liquid-crystal microlens arrays using patterned polymer networks,” Opt. Lett. 29(14), 1608–1610 (2004). [CrossRef] [PubMed]

15.

L. G. Commander, S. E. Day, and D. R. Selviah, “Variable focal length microlenses,” Opt. Commun. 177(1–6), 157–170 (2000). [CrossRef]

16.

Y. Hisakado, H. Kikichi, T. Nagamura, and T. Kajiyama, “Large Electro-optic Kerr Effect in Polymer-Stabilized Liquid-Crystalline Blue Phases,” Adv. Mater. 17(1), 96–98 (2005). [CrossRef]

17.

S. Y. Lu and L. C. Chien, “Electrically switched color with polymer-stabilized blue-phase liquid crystals,” Opt. Lett. 35(4), 562–564 (2010). [CrossRef] [PubMed]

18.

J. Yan, H.-C. Cheng, S. Gauza, Y. Li, M. Jiao, L. Rao, and S.-T. Wu, “Extended Kerr effect of polymer-stabilized blue-phase liquid crystals,” Appl. Phys. Lett. 96(7), 071105 (2010). [CrossRef]

19.

J. Yan, Y. Li, and S.-T. Wu, “High-efficiency and fast-response tunable phase grating using a blue phase liquid crystal,” Opt. Lett. 36(8), 1404–1406 (2011). [CrossRef] [PubMed]

20.

Z. Ge, S. Gauza, M. Jiao, H. Xianyu, and S.-T. Wu, “Electro-optics of polymer-stabilized blue phase liquid crystal displays,” Appl. Phys. Lett. 94(10), 101104 (2009). [CrossRef]

21.

K. M. Chen, S. Gauza, H. Xianyu, and S. T. Wu, “Submillisecond Gray-Level Response Time of a Polymer-Stabilized Blue-Phase Liquid Crystal,” J. Disp. Technol. 6(2), 49–51 (2010). [CrossRef]

22.

S. Piazzolla and B. K. Jenkins, “Dynamics during holographic exposure in photopolymers for single and multiplexed gratings,” J. Mod. Opt. 46(15), 2079–2110 (1999).

OCIS Codes
(160.3710) Materials : Liquid crystals
(220.3630) Optical design and fabrication : Lenses
(230.3720) Optical devices : Liquid-crystal devices

ToC Category:
Optical Devices

History
Original Manuscript: November 15, 2013
Revised Manuscript: December 26, 2013
Manuscript Accepted: December 27, 2013
Published: January 8, 2014

Citation
Shih-Hung Lin, Lin-Song Huang, Chi-Huang Lin, and Chie-Tong Kuo, "Polarization-independent and fast tunable microlens array based on blue phase liquid crystals," Opt. Express 22, 925-930 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-1-925


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References

  1. Y.-P. Huang, C.-W. Chen, T.-C. Shen, J.-F. Huang, “Autostereoscopic 3D display with scanning multi-electrode driven liquid crystal (MeD-LC) lens,” J. 3D Res. 1(1), 39–42 (2010). [CrossRef]
  2. Y.-J. Lee, J.-H. Baek, Y. Kim, J. U. Heo, Y.-K. Moon, J. S. Gwag, C.-J. Yu, J.-H. Kim, “Polarizer-free liquid crystal display with electrically switchable microlens array,” Opt. Express 21(1), 129–134 (2013). [CrossRef] [PubMed]
  3. C. J. Hsu, C. R. Sheu, “Using photopolymerization to achieve tunable liquid crystal lenses with coaxial bifocals,” Opt. Express 20(4), 4738–4746 (2012). [CrossRef] [PubMed]
  4. K.-C. Lo, J.-D. Wang, C.-R. Lee, T.-S. Mo, “Electrically controllable and polarization-independent Fresnel zone-plate in a circularly symmetric hybrid-aligned liquid crystal film with a photoconductive polymer layer,” Appl. Phys. Lett. 91(18), 181104 (2007). [CrossRef]
  5. S. Sato, “Liquid-crystal lens-cells with variable focal length,” Jpn. J. Appl. Phys. 18(9), 1679–1684 (1979). [CrossRef]
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