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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 19, Iss. 10 — May. 9, 2011
  • pp: 9676–9689
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All-optically controllable dye-doped liquid crystal infiltrated photonic crystal fiber

Chia-Rong Lee, Jia-De Lin, Yan-Jhen Huang, Shih-Chan Huang, Shih-Hung Lin, and Chin-Ping Yu  »View Author Affiliations


Optics Express, Vol. 19, Issue 10, pp. 9676-9689 (2011)
http://dx.doi.org/10.1364/OE.19.009676


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Abstract

A novel demonstration of an all-optically controllable dye-doped liquid crystal infiltrated photonic crystal fiber (DDLCIPCF) is presented. Overall spectral transmittance of the DDLCIPCF can decrease and then increase with a concomitant red-shift of the spectrum curve with increasing irradiation time of one UV beam. Continuing irradiation of one green beam following UV illumination on the DDLCIPCF can cause the transmission spectrum to recover completely. The reversible all-optical controllability of the photonic band structure of the fiber is attributable to the isothermal planar nematic (PN) → scattering (S) → isotropic (I) and I → S → PN state transitions of the LCs via the UV-beam-induced transcis and green-beam-induced cistrans back isomerizations of the azo-dye, respectively, in the cladding of the DDLCIPCF. The photoinduced appearance of the S state and the variation of the index modulation between the core and the cladding of the fiber result in the variation of overall spectral transmittance and the shift of transmission spectrum, respectively.

© 2011 OSA

1. Introduction

Photonic crystal fiber (PCF) has been widely investigated during the last decade because of its interesting light-guiding mechanisms, many peculiarities (such as high nonlinearity, high numerical aperture, large mode area, and endlessly single mode), and potential applications [1

1. J. C. Knight, J. Broeng, T. A. Birks, and P. S. J. Russell, “Photonic band gap guidance in optical fibers,” Science 282(5393), 1476–1478 (1998). [CrossRef] [PubMed]

3

3. J. C. Knight, “Photonic crystal fibres,” Nature 424(6950), 847–851 (2003). [CrossRef] [PubMed]

]. The features of a PCF are determined by an unusual structure with a spatially periodic microstructure having air array microholes in the silica cladding around a solid or hollow core. Light in a PCF with a solid core of high refractive index is mainly guided via modified total internal reflection similar to a conventional single-mode fiber. Light in a PCF with a hollow core, however, is guided by a so-called photonic bandgap (PBG) effect [1

1. J. C. Knight, J. Broeng, T. A. Birks, and P. S. J. Russell, “Photonic band gap guidance in optical fibers,” Science 282(5393), 1476–1478 (1998). [CrossRef] [PubMed]

3

3. J. C. Knight, “Photonic crystal fibres,” Nature 424(6950), 847–851 (2003). [CrossRef] [PubMed]

]. Such a spatially periodic, microstructured air microhole array not only affects the optical properties of a PCF, but also provides an opportunity to create tunable fiber-based devices by infiltrating high-index materials such as polymer [4

4. B. J. Eggleton, C. Kerbage, P. S. Westbrook, R. S. Windeler, and A. Hale, “Microstructured optical fiber devices,” Opt. Express 9(13), 698–713 (2001). [CrossRef] [PubMed]

], oil [5

5. R. T. Bise, R. S. Windeler, K. S. Kranz, C. Kerbage, B. J. Eggleton, and D. J. Trevor, “Tunable photonic band gap fiber,” in OSA Trends in Optics and Photonics (TOPS) 70, Optical Fiber Communication Conference Technical Digest, Postconference Edition (Optical Society of America, Washington, DC, 2002), 466–468.

], and liquid crystal (LC) [6

6. T. T. Alkeskjold, J. Laegsgaard, A. Bjarklev, D. S. Hermann, A. Anawati, J. Broeng, J. Li, and S. T. Wu, “All-optical modulation in dye-doped nematic liquid crystal photonic bandgap fibers,” Opt. Express 12(24), 5857–5871 (2004). [CrossRef] [PubMed]

20

20. L. Scolari, S. Gauza, H. Xianyu, L. Zhai, L. Eskildsen, T. T. Alkeskjold, S.-T. Wu, and A. Bjarklev, “Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals,” Opt. Express 17(5), 3754–3764 (2009). [CrossRef] [PubMed]

,25

25. K. Szaniawska, T. R. Wolinski, S. Ertman, P. Lesiak, A. W. Domanski, R. Dabrowski, E. Nowinowski-Kruszelnicki, and J. Wojcik, “Temperature tuning in photonic liquid crystal fibers,” Proc. SPIE 5947, 594705, 594705-6 (2005). [CrossRef]

,26

26. J. Tuominen, H. Hoffrén, and H. Ludvigsen, “All-optical switch based on liquid-crystal infiltrated photonic bandgap fiber in transverse configuration,” JEOS:RP 2, 07016 (2007). [CrossRef]

] into the air microholes.

Among those high-index materials infiltrated PCFs mentioned above, the LC-infiltrated photonic crystal fiber (LCIPCF) attracts significant attention because its photonic band structure can be easily controlled by changing the LC structure in the microholes, and thus the index modulation between the cladding and the core in a thermal [6

6. T. T. Alkeskjold, J. Laegsgaard, A. Bjarklev, D. S. Hermann, A. Anawati, J. Broeng, J. Li, and S. T. Wu, “All-optical modulation in dye-doped nematic liquid crystal photonic bandgap fibers,” Opt. Express 12(24), 5857–5871 (2004). [CrossRef] [PubMed]

12

12. J. Du, Y. Liu, Z. Wang, B. Zou, B. Liu, and X. Dong, “Liquid crystal photonic bandgap fiber: different bandgap transmissions at different temperature ranges,” Appl. Opt. 47(29), 5321–5324 (2008). [CrossRef] [PubMed]

, 25

25. K. Szaniawska, T. R. Wolinski, S. Ertman, P. Lesiak, A. W. Domanski, R. Dabrowski, E. Nowinowski-Kruszelnicki, and J. Wojcik, “Temperature tuning in photonic liquid crystal fibers,” Proc. SPIE 5947, 594705, 594705-6 (2005). [CrossRef]

, 26

26. J. Tuominen, H. Hoffrén, and H. Ludvigsen, “All-optical switch based on liquid-crystal infiltrated photonic bandgap fiber in transverse configuration,” JEOS:RP 2, 07016 (2007). [CrossRef]

], electric [9

9. L. Wei, L. Eskildsen, J. Weirich, L. Scolari, T. T. Alkeskjold, and A. Bjarklev, “Continuously tunable all-in-fiber devices based on thermal and electrical control of negative dielectric anisotropy liquid crystal photonic bandgap fibers,” Appl. Opt. 48(3), 497–503 (2009). [CrossRef] [PubMed]

11

11. T. R. Wolínski, S. Ertman, A. Czapla, P. Lesiak, K. Nowecka, A. W. Domanski, E. Nowinowski-Kruszelnicki, R. Dabrowski, and J. Wojcik, “Polarization effects in photonic liquid crystal fibers,” Meas. Sci. Technol. 18(10), 3061–3069 (2007). [CrossRef]

, 13

13. L. Scolari, T. T. Alkeskjold, J. Riishede, A. Bjarklev, D. S. Hermann, A. Anawati, M. Nielsen, and P. Bassi, “Continuously tunable devices based on electrical control of dual-frequency liquid crystal filled photonic bandgap fibers,” Opt. Express 13(19), 7483–7496 (2005). [CrossRef] [PubMed]

16

16. A. Lorenz, H.-S. Kitzerow, A. Schwuchow, J. Kobelke, and H. Bartelt, “Photonic crystal fiber with a dual-frequency addressable liquid crystal: behavior in the visible wavelength range,” Opt. Express 16(23), 19375–19381 (2008). [CrossRef]

, 18

18. C.-H. Lee, C.-H. Chen, C.-L. Kao, C.-P. Yu, S.-M. Yeh, W.-H. Cheng, and T.-H. Lin, “Photo and electrical tunable effects in photonic liquid crystal fiber,” Opt. Express 18(3), 2814–2821 (2010). [CrossRef] [PubMed]

,20

20. L. Scolari, S. Gauza, H. Xianyu, L. Zhai, L. Eskildsen, T. T. Alkeskjold, S.-T. Wu, and A. Bjarklev, “Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals,” Opt. Express 17(5), 3754–3764 (2009). [CrossRef] [PubMed]

], or optic approach [6

6. T. T. Alkeskjold, J. Laegsgaard, A. Bjarklev, D. S. Hermann, A. Anawati, J. Broeng, J. Li, and S. T. Wu, “All-optical modulation in dye-doped nematic liquid crystal photonic bandgap fibers,” Opt. Express 12(24), 5857–5871 (2004). [CrossRef] [PubMed]

, 17

17. V. K. S. Hsiao and C.-Y. Ko, “Light-controllable photoresponsive liquid-crystal photonic crystal fiber,” Opt. Express 16(17), 12670–12676 (2008). [PubMed]

]. Alkeskjold et al., in particular, investigated an optically modulated dye-doped LCIPCF (DDLCIPCF) based on the mechanism of a local-heating effect via illumination on the dye. Hsiao et al. reported a light-switchable photoresponsive LCIPCF, in which the transmittance of the PCF can be switched in one second by the isotropic→nematic phase transition of LCs via the cistrans isomerization of azo-dye. For the first time, a peculiar DDLCIPCF is demonstrated in which photonic band structures can be reversible and all-optically controlled. Overall spectral transmittance in the transmission spectrum of the DDLCIPCF can be controlled to decay and then rise with a concomitant red-shift of the spectrum curve with the increase of irradiation time of one UV beam. Successive irradiation of one green beam on the DDLCIPCF following UV illumination can completely recover the photonic band structure of the DDLCIPCF. The reversible all-optical controllability of the DDLCIPCF is attributable to the isothermal planar nematic (PN) → scattering (S) → isotropic (I) and I → S → PN state transitions of the LCs via the UV-beam-induced transcis and green-beam-induced cistrans back isomerizations of the azo-dye in the cladding, respectively. The photoinduced scattering state, as well as the variation of the index modulation between the core and cladding, results in the variation of overall spectral transmittance and the shift of the transmission spectrum, respectively. The light-induced thermal effect of the dye is excluded from the possible mechanism of the all-optical controllability of the DDLCIPCF.

2. Sample preparation and experimental setups

Figures 2(a)
Fig. 2 Top view of the experimental setups for examining the all-optical controllability of the DDLCIPCF. One white beam is guided via a single-mode fiber A and coupled into the input end of the DDLCIPCF. One UV beam and one green beam are guided to irradiate the DDLCIPCF at sequence. (a) The transmitted image of the cross section of the DDLCIPCF at its output end is collected by an objective lens (×10) and then recorded by a CCD camera. (b) The spectrum of the transmitted output signal at the output end of the DDLCIPCF is coupled into a single-mode fiber B and guided into a spectrometer for recording the transmission spectrum of the white beam via the DDLCIPCF. In (a) and (b), the green beam is reflected by an NBS into the objective lens and guided by the single-mode fiber B, respectively, and then irradiates the DDLCIPCF.
and 2(b) present two different experimental setups for measuring the cross-sectional image and the transmission spectrum of the DDLCIPCF, respectively, under all-optical control. One white beam from a white light source is guided by a single-mode fiber A and coupled into the input end of the DDLCIPCF by aligning these two fibers on an xyz-stage. One UV beam (with a fixed intensity of 237.5 mW/cm2 and a variable irradiation time tUV) from a UV light source and one green beam (with a variable irradiation time tG) from a diode-pumped solid state (DPSS) laser source (532 nm) are used to sequentially illuminate the DDLCIPCF. The ways to guide the green beam with various intensities to irradiate the DDLCIPCF are different in the two setups. In Fig. 2(a), the signal of the transmitted image of the cross section for the DDLCIPCF at its output end is guided by an objective lens (×10) and then recorded by a CCD camera. The green beam, with 353.7 mW/cm2, is reflected by a nonpolarizing beam-splitter (NBS) and collected by the objective lens and then illuminates the DDLCIPCF. In Fig. 2(b), the transmitted signal at the output end of the DDLCIPCF is coupled into a single-mode fiber B and guided into a spectrometer (USB2000, Ocean Optics) to record the transmission spectrum of the output signal. The green beam with 955.4 mW/cm2 is guided by the single-mode fiber B and then illuminates the DDLCIPCF.

3. Results and discussion

3.1 UV-visible absorption spectra of the azo-dye in a homogeneously-aligned DDLC cell

Before the experimental examination of the all-optical controllability of the DDLCIPCF, auxiliary data, associated with the absorption spectrum in UV-visible region for the 4MAB azo-dye in a homogeneously-aligned DDLC plane cell (length × width × thickness: 3 cm × 2 cm × 7 μm), are pre-acquired. The blue and red curves in Fig. 3
Fig. 3 Blue and red absorption spectrum curves for the 4MAB azo-dye in a homogenously aligned DDLC plane cell with a 7 μm thickness before and after the irradiation of the UV light with 237.5 mW/cm2 on the cell for two minutes, respectively. The inset represents the transcis isomerization under UV irradiation and the cistrans back isomerization via green-light-irradiation or thermal relaxation (Δ) for the azo-dye.
show the measured absorption spectra of the azo-dye before and after irradiating the cell by the UV light with 237.5 mW/cm2 for approximately two minutes, respectively. The 4MAB dye has two absorption bands exhibiting in UV (around 375 nm) and visible (around 445 nm) regions, which are associated with π-π* and n-π* transitions, respectively. The azo-dyes are usually stable themselves at the rod-like trans state in the dark, as displayed in the inset of Fig. 3. With the irradiation of the UV light, massive trans-4MAB molecules can be photoisomerized rapidly into a curved cis state such that the absorption peaks at 375 and 445 nm drops and rises, respectively. Moreover, cis-4MAB can be rapidly transformed into a trans state with the irradiation of a long-wavelength green light or slowly via thermal relaxation. Subsequently, the absorption spectrum of the azo-dye may return to the initial state.

3.2 Transmitted CCD image of the cross section and the normalized transmitted intensity of the all-optically controllable DDLCIPCF

Figure 4(a)
Fig. 4 Variations of (a) the CCD image of the cross section and (b) the normalized transmitted intensity in the output end of the DDLCIPCF upon increasing the irradiation time of the UV beam tUV from 0 to 660 s. Three different states of LCs in the cladding of the DDLCIPCF present in those relative extremities of the transmitted intensity curve.
shows the variation of the CCD image of the cross section at the output end of the DDLCIPCF while increasing the irradiation time of the UV light (with a fixed intensity of 237.5 mW/cm2) from tUV=0 to 660 s. Output brightness on the DDLCIPCF core decreases from high to low levels by increasing tUV from 0 to 20 s, and then increases to a brighter level by increasing tUV from 20 to 660 s. A summary of the experimental results is seen in Fig. 4(b), in which the variation of the normalized transmitted intensity (defined as the transmitted intensity divided by the strongest transmitted intensity) at the output end of the DDLCIPCF with the tUV is presented. Apparently, experimental results in Figs. 4(a) and 4(b) imply that the LCs in the cladding region of the fiber may go through three different states corresponding to the relative extremities of the transmitted intensity curve during the increase of tUV. The normalized transmitted intensity first decreases from a high to its weakest level from state 1 at tUV=0 s to state 2 at tUV=20 s, and then increases to the strongest level from state 2 to state 3 at tUV=660 s. The mechanism models associated with the three different states will be addressed and discussed in Section 3.3. Following UV irradiation, the DDLCIPCF is irradiated with one green beam [using the setup in Fig. 2(a)] with a fixed intensity of 353.7 mW/cm2 and an increasing irradiation time tG from 0 to 60 s. Associated experimental results are displayed in Figs. 5(a)
Fig. 5 Variations of (a) the CCD image of the cross section and (b) the normalized transmitted intensity in the output end of the DDLCIPCF upon increasing the irradiation time of the green beam tG from 0 to 60 s, following UV irradiation with 237.5 mW/cm2 for 660 s.
and 5(b), in which the variations of the CCD image of the cross section and the normalized transmitted intensity at the output end of the DDLCIPCF with increasing tG are acquired, respectively. Either the core brightness or the normalized transmitted intensity at the output end of the DDLCIPCF first decreases from a highest to a weakest level from state 3 at tG=0 s to state 2 at tG=15 s, and increases to a high level from state 2 to state 1 at tG=60 s. Evidently, the changing tendency of the normalized transmitted intensity of the DDLCIPCF, with the increase of tG, is reversed to that with the increase of tUV as shown in Fig. 4. Therefore, the present DDLCIPCF is demonstrated to exhibit an all-optically (reversible) light-guiding controllability under the successive irradiation of one UV and one green beam.

3.3 Mechanism models associated with the all-optical controllability of the DDLCIPCF

Since a separate experiment shows that no optically controllable feature can be found if no azo-dye is added in the LCs infiltrated in the PCF, the azo-dye plays a key role in the previously obtained experimental results (Sec. 3.2) for the all-optical controllability of the DDLCIPCF. As shown in Fig. 6
Fig. 6 Mechanism for the isothermal phase transitions of LCs from N to I and I to N phases induced by the transcis and cistrans back isomerizations of the azo-dyes, respectively, under successive irradiations of one UV and one green beams, with increasing individual irradiation time of tUV and tG, respectively.
, the main mechanism for the reversible all-opticalcontrollability of the DDLCIPCF are, accordingly, attributed to the isothermal N→I and I→N phase transitions of the LCs via the UV-beam-induced transcis and green-beam-induced cistrans back isomerizations of the 4MAB dyes [21

21. H.-K. Lee, A. Kanazawa, T. Shiono, T. Ikeda, T. Fujisawa, M. Aizawa, and B. Lee, “All-optically controllable polymer/liquid crystal composite films containing the azobenzene liquid crystal,” Chem. Mater. 10(5), 1402–1407 (1998). [CrossRef]

]. The azo-dyes are generally stable in a rod-like trans state in the dark. The trans-4MAB dyes tend to align along the long axes of the LC molecules due to the guest-host effect in the DDLC. The trans-isomers can absorb UV photons and promptly transform to bent cis-isomers by transcis isomerization, and thus disturb the LC host. The concentration of 4MAB dyes converting to cis-state can increase with increasing tUV so that the LC host can gradually change isothermally from N to I phase. While the UV light is turned off and the DDLC is turned to be irradiated by the green light, the cis-4MAB dyes can transform rapidly back to the trans-state via cistrans back isomerization [21

21. H.-K. Lee, A. Kanazawa, T. Shiono, T. Ikeda, T. Fujisawa, M. Aizawa, and B. Lee, “All-optically controllable polymer/liquid crystal composite films containing the azobenzene liquid crystal,” Chem. Mater. 10(5), 1402–1407 (1998). [CrossRef]

]. The concentration of the cis-4MAB converting back to the trans-state via consecutive cistrans back isomerization can lead to the reverse phase transition of LCs from I to N as tG increases.

overall increase of the concentration of the trans-isomers via cistrans back isomerization, which can result in a variation of LC texture in the irradiated region. This variation is reversed to that caused by UV irradiation with increasing tUV, which is the reason that the LCs in the cladding of the DDLCIPCF undergo reversible PN→S→I and I→S→ PN state transitions under the successive irradiation of the UV and green beams.

3.4 Transmission spectrum of the all-optically controllable DDLCIPCF

To understand the all-optical controllability for the photonic band structure of the DDLCIPCF, the transmission spectrum for the output signal of the incident white beam is further measured via the DDLCIPCF under successive irradiation of the UV beam (237.5 mW/cm2) and the green beam (955.4 mW/cm2) based on the setup in Fig. 2(b). Figures 9(a)
Fig. 9 Variations of the transmission spectrum of the incident white beam through the DDLCIPCF with increasing tUV (a) from 0 to 20 s (PN → S states) and (b) from 20 to 660 s (S → I states) at a fixed irradiated intensity 237.5 mW/cm2 of the UV beam. The red-dotted vertical lines shown in (a) and (b) indicate the calculated cut-off wavelengths of the optical mode guided in a single LC hole based on Eq. (1) when the LCs in the hole is at PN and I state, respectively. These cut-off wavelengths coincide with the minima in the transmission spectrum of the DDLCIPCF.
and 9(b) show the variations of transmission spectrum of the incident white beam in the spectral region of 500–750 nm through the DDLCIPCF, with increasing tUV from 0 to 20 s and from 20 to 660 s, respectively. The transmission in the vertical axis is defined by 10 × log (It/I0) (dB), where It and I0 represent the transmitted and incident intensities of the white beam, respectively. The mechanism to guide the white beam in the DDLCIPCF is clearly the PBG effect because of the appearance of the series of bandgaps in the transmission spectrum.

The reason for the optical controllability of the overall spectral transmittance of the DDLCIPCF under the UV irradiation presented in Fig. 9 is explained as follows. The overall spectral transmittance of the fiber first decreases at tUV=0→20 s and then increases at tUV=20→660 s [Figs. 9(a) and 9(b), respectively]. The variation of overall spectral transmittance is consistent with data obtained in the variations of the CCD images of the cross section of the DDLCIPCF and of its normalized transmitted intensity [Figs. 4(a) and 4(b), respectively]. As explained in Section 3.3, under the irradiation of the UV beam with increasing tUV at 0→20 s, the multi-domain-like LC texture in the cladding region will appear to cause an S state, resulting in the significant decrease in overall spectral transmittance of DDLCIPCF. While tUV continually increases from 20 to 660 s, the isotropic LC nuclei overextend and merge with each other, such that the scattering decays in the cladding region, leading to the increase of the overall spectral transmittance of the fiber. At tUV ≥ 660 s, the overall LCs in the irradiated cladding region becomes isotropic such that the overall spectral transmittance achieves a significantly high level. Note that the transmittance at the positions of both the maxima and minima of the spectrum increases at tUV=20→660 s in Fig. 9(b). The transmission bands in the transmission spectra are mainly contributed from the guiding light at the region of the fiber core, which is identified by comparing CCD images in Fig. 4(a) and the transmission spectra in Fig. 9(a) at tUV=0→20 s. At tUV=20→660 s, the increase of brightness in the cladding region of the fiber, displayed in Fig. 4(a), causes the increase of transmittance in the positions of the minima in the spectrum. In this interval, the increase of the overall transmittance in the spectrum can be attributed to the decrease of scattering loss from the anisotropic to isotropic orientation of LCs in the DDLCIPCF [12

12. J. Du, Y. Liu, Z. Wang, B. Zou, B. Liu, and X. Dong, “Liquid crystal photonic bandgap fiber: different bandgap transmissions at different temperature ranges,” Appl. Opt. 47(29), 5321–5324 (2008). [CrossRef] [PubMed]

, 25

25. K. Szaniawska, T. R. Wolinski, S. Ertman, P. Lesiak, A. W. Domanski, R. Dabrowski, E. Nowinowski-Kruszelnicki, and J. Wojcik, “Temperature tuning in photonic liquid crystal fibers,” Proc. SPIE 5947, 594705, 594705-6 (2005). [CrossRef]

].

3.5 Exclusion of thermal-effect-induced phase transition for the mechanism of the all-optical controllability of the DDLCIPCF

The following two separate experiments will elucidate that the all-optical controllability of the DDLCIPCF is not attributable to the thermal-effect-induced phase transition of LCs in the cladding region under the photo-excitation of the azo-dye. As mentioned in Section 3.3,the LCs in the cladding lies in isotropic state once the fiber is irradiated by the UV beam with 237.5 mW/cm2 for 660 s. At the moment tUV=660 s, the UV beam is turned off. The state of the LCs in the cladding can then very slowly recover from I to S and then PN states due to the thermal cistrans back isomerization of the azo-dye. Figure 11
Fig. 11 Variations of the normalized transmitted intensity and corresponding CCD image of the cross section of the DDLCIPCF with the time via the I→S→PN state transition of LCs in the cladding of the fiber via the thermal cistrans back isomerization, following the UV irradiation with 237.5 mW/cm2 on the fiber for 660 s.
shows the variations of the normalized transmitted intensity and corresponding CCD image of the cross section of the DDLCIPCF with the time via such a state transition of LCs. Clearly, the time to induce the I→S→PN state transition of LCs in the cladding of the fiber via the thermal cistrans back isomerization is as long as tC→T,Δ≅93 hrs which is much longer than that via the green-beam-irradiation-induced cistrans back isomerization (60 s). In a separate experiment, an un-irradiated DDLCIPCF is placed on the sample platform of the POM in a dark room for observing the state variation of the LCs. The fiber is pre-heated by a vacuum thermal stage (TS102V-STC20A, INSTEC) such that the overall LCs in the cladding become isotropic, and thereupon, the thermal stage is removed. The measured thermal relaxation time (tTR) for the LCs to undergo I→S→PN state transition is less than 10 minutes. The time tTR (<10 min) is much less than tC→T,Δ (93 hr) obtained above, and thus the all-optical controllability of the fiber described previously is not attributed to the photoinduced thermal-effect, but to the isothermal photoisomerization-induced state transition of the LCs in the cladding of the fiber.

4. Conclusion

Acknowledgments

The authors would like to thank the National Science Council of the Republic of China, Taiwan (Contract number: NSC 97-2112-M-006-013-MY3) and the Advanced Optoelectronic Technology Center, National Cheng Kung University, under projects from the Ministry of Education, for financially supporting this research. We greatly appreciate KGSupport for the editorial assistance.

References and links

1.

J. C. Knight, J. Broeng, T. A. Birks, and P. S. J. Russell, “Photonic band gap guidance in optical fibers,” Science 282(5393), 1476–1478 (1998). [CrossRef] [PubMed]

2.

P. Russell, “Photonic crystal fibers,” Science 299(5605), 358–362 (2003). [CrossRef] [PubMed]

3.

J. C. Knight, “Photonic crystal fibres,” Nature 424(6950), 847–851 (2003). [CrossRef] [PubMed]

4.

B. J. Eggleton, C. Kerbage, P. S. Westbrook, R. S. Windeler, and A. Hale, “Microstructured optical fiber devices,” Opt. Express 9(13), 698–713 (2001). [CrossRef] [PubMed]

5.

R. T. Bise, R. S. Windeler, K. S. Kranz, C. Kerbage, B. J. Eggleton, and D. J. Trevor, “Tunable photonic band gap fiber,” in OSA Trends in Optics and Photonics (TOPS) 70, Optical Fiber Communication Conference Technical Digest, Postconference Edition (Optical Society of America, Washington, DC, 2002), 466–468.

6.

T. T. Alkeskjold, J. Laegsgaard, A. Bjarklev, D. S. Hermann, A. Anawati, J. Broeng, J. Li, and S. T. Wu, “All-optical modulation in dye-doped nematic liquid crystal photonic bandgap fibers,” Opt. Express 12(24), 5857–5871 (2004). [CrossRef] [PubMed]

7.

D. Noordegraaf, L. Scolari, J. Laegsgaard, T. Tanggaard Alkeskjold, G. Tartarini, E. Borelli, P. Bassi, J. Li, and S. T. Wu, “Avoided-crossing-based liquid-crystal photonic-bandgap notch filter,” Opt. Lett. 33(9), 986–988 (2008). [CrossRef] [PubMed]

8.

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9.

L. Wei, L. Eskildsen, J. Weirich, L. Scolari, T. T. Alkeskjold, and A. Bjarklev, “Continuously tunable all-in-fiber devices based on thermal and electrical control of negative dielectric anisotropy liquid crystal photonic bandgap fibers,” Appl. Opt. 48(3), 497–503 (2009). [CrossRef] [PubMed]

10.

T. R. Wolínski, K. Szaniawska, S. Ertman, P. Lesiak, A. W. Domanski, R. Dabrowski, E. Nowinowski-Kruszelnicki, and J. Wojcik, “Influence of temperature and electrical fields on propagation properties of photonic liquid-crystal fibres,” Meas. Sci. Technol. 17(5), 985–991 (2006). [CrossRef]

11.

T. R. Wolínski, S. Ertman, A. Czapla, P. Lesiak, K. Nowecka, A. W. Domanski, E. Nowinowski-Kruszelnicki, R. Dabrowski, and J. Wojcik, “Polarization effects in photonic liquid crystal fibers,” Meas. Sci. Technol. 18(10), 3061–3069 (2007). [CrossRef]

12.

J. Du, Y. Liu, Z. Wang, B. Zou, B. Liu, and X. Dong, “Liquid crystal photonic bandgap fiber: different bandgap transmissions at different temperature ranges,” Appl. Opt. 47(29), 5321–5324 (2008). [CrossRef] [PubMed]

13.

L. Scolari, T. T. Alkeskjold, J. Riishede, A. Bjarklev, D. S. Hermann, A. Anawati, M. Nielsen, and P. Bassi, “Continuously tunable devices based on electrical control of dual-frequency liquid crystal filled photonic bandgap fibers,” Opt. Express 13(19), 7483–7496 (2005). [CrossRef] [PubMed]

14.

D. Noordegraaf, L. Scolari, J. Laegsgaard, L. Rindorf, and T. T. Alkeskjold, “Electrically and mechanically induced long period gratings in liquid crystal photonic bandgap fibers,” Opt. Express 15(13), 7901–7912 (2007). [CrossRef] [PubMed]

15.

T. T. Alkeskjold and A. Bjarklev, “Electrically controlled broadband liquid crystal photonic bandgap fiber polarimeter,” Opt. Lett. 32(12), 1707–1709 (2007). [CrossRef] [PubMed]

16.

A. Lorenz, H.-S. Kitzerow, A. Schwuchow, J. Kobelke, and H. Bartelt, “Photonic crystal fiber with a dual-frequency addressable liquid crystal: behavior in the visible wavelength range,” Opt. Express 16(23), 19375–19381 (2008). [CrossRef]

17.

V. K. S. Hsiao and C.-Y. Ko, “Light-controllable photoresponsive liquid-crystal photonic crystal fiber,” Opt. Express 16(17), 12670–12676 (2008). [PubMed]

18.

C.-H. Lee, C.-H. Chen, C.-L. Kao, C.-P. Yu, S.-M. Yeh, W.-H. Cheng, and T.-H. Lin, “Photo and electrical tunable effects in photonic liquid crystal fiber,” Opt. Express 18(3), 2814–2821 (2010). [CrossRef] [PubMed]

19.

V. V. Presnyakov, Z. J. Liu, and V. G. Chigrinov, “Infiltration of photonic crystal fiber with liquid crystals,” Proc. SPIE 6017, 60170J, 60170J-7 (2005). [CrossRef]

20.

L. Scolari, S. Gauza, H. Xianyu, L. Zhai, L. Eskildsen, T. T. Alkeskjold, S.-T. Wu, and A. Bjarklev, “Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals,” Opt. Express 17(5), 3754–3764 (2009). [CrossRef] [PubMed]

21.

H.-K. Lee, A. Kanazawa, T. Shiono, T. Ikeda, T. Fujisawa, M. Aizawa, and B. Lee, “All-optically controllable polymer/liquid crystal composite films containing the azobenzene liquid crystal,” Chem. Mater. 10(5), 1402–1407 (1998). [CrossRef]

22.

N. V. Tabiryan, S. V. Serak, and V. A. Grozhik, “Photoinduced critical opalescence and reversible all-optical switching in photosensitive liquid crystals,” J. Opt. Soc. Am. B 20(3), 538–544 (2003). [CrossRef]

23.

A. K. Abeeluck, N. M. Litchinitser, C. Headley, and B. J. Eggleton, “Analysis of spectral characteristics of photonic bandgap waveguides,” Opt. Express 10(23), 1320–1333 (2002). [PubMed]

24.

N. M. Litchinitser, S. C. Dunn, P. E. Steinvurzel, B. J. Eggleton, T. P. White, R. C. McPhedran, and C. M. de Sterke, “Application of an ARROW model for designing tunable photonic devices,” Opt. Express 12(8), 1540–1550 (2004). [CrossRef] [PubMed]

25.

K. Szaniawska, T. R. Wolinski, S. Ertman, P. Lesiak, A. W. Domanski, R. Dabrowski, E. Nowinowski-Kruszelnicki, and J. Wojcik, “Temperature tuning in photonic liquid crystal fibers,” Proc. SPIE 5947, 594705, 594705-6 (2005). [CrossRef]

26.

J. Tuominen, H. Hoffrén, and H. Ludvigsen, “All-optical switch based on liquid-crystal infiltrated photonic bandgap fiber in transverse configuration,” JEOS:RP 2, 07016 (2007). [CrossRef]

OCIS Codes
(160.3710) Materials : Liquid crystals
(230.1150) Optical devices : All-optical devices
(060.4005) Fiber optics and optical communications : Microstructured fibers
(060.5295) Fiber optics and optical communications : Photonic crystal fibers

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: March 16, 2011
Revised Manuscript: April 23, 2011
Manuscript Accepted: April 26, 2011
Published: May 3, 2011

Citation
Chia-Rong Lee, Jia-De Lin, Yan-Jhen Huang, Shih-Chan Huang, Shih-Hung Lin, and Chin-Ping Yu, "All-optically controllable dye-doped liquid crystal infiltrated photonic crystal fiber," Opt. Express 19, 9676-9689 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-10-9676


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References

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  5. R. T. Bise, R. S. Windeler, K. S. Kranz, C. Kerbage, B. J. Eggleton, and D. J. Trevor, “Tunable photonic band gap fiber,” in OSA Trends in Optics and Photonics (TOPS) 70, Optical Fiber Communication Conference Technical Digest, Postconference Edition (Optical Society of America, Washington, DC, 2002), 466–468.
  6. T. T. Alkeskjold, J. Laegsgaard, A. Bjarklev, D. S. Hermann, A. Anawati, J. Broeng, J. Li, and S. T. Wu, “All-optical modulation in dye-doped nematic liquid crystal photonic bandgap fibers,” Opt. Express 12(24), 5857–5871 (2004). [CrossRef] [PubMed]
  7. D. Noordegraaf, L. Scolari, J. Laegsgaard, T. Tanggaard Alkeskjold, G. Tartarini, E. Borelli, P. Bassi, J. Li, and S. T. Wu, “Avoided-crossing-based liquid-crystal photonic-bandgap notch filter,” Opt. Lett. 33(9), 986–988 (2008). [CrossRef] [PubMed]
  8. T. T. Larsen, A. Bjarklev, D. S. Hermann, and J. Broeng, “Optical devices based on liquid crystal photonic bandgap fibres,” Opt. Express 11(20), 2589–2596 (2003). [CrossRef] [PubMed]
  9. L. Wei, L. Eskildsen, J. Weirich, L. Scolari, T. T. Alkeskjold, and A. Bjarklev, “Continuously tunable all-in-fiber devices based on thermal and electrical control of negative dielectric anisotropy liquid crystal photonic bandgap fibers,” Appl. Opt. 48(3), 497–503 (2009). [CrossRef] [PubMed]
  10. T. R. Wolínski, K. Szaniawska, S. Ertman, P. Lesiak, A. W. Domanski, R. Dabrowski, E. Nowinowski-Kruszelnicki, and J. Wojcik, “Influence of temperature and electrical fields on propagation properties of photonic liquid-crystal fibres,” Meas. Sci. Technol. 17(5), 985–991 (2006). [CrossRef]
  11. T. R. Wolínski, S. Ertman, A. Czapla, P. Lesiak, K. Nowecka, A. W. Domanski, E. Nowinowski-Kruszelnicki, R. Dabrowski, and J. Wojcik, “Polarization effects in photonic liquid crystal fibers,” Meas. Sci. Technol. 18(10), 3061–3069 (2007). [CrossRef]
  12. J. Du, Y. Liu, Z. Wang, B. Zou, B. Liu, and X. Dong, “Liquid crystal photonic bandgap fiber: different bandgap transmissions at different temperature ranges,” Appl. Opt. 47(29), 5321–5324 (2008). [CrossRef] [PubMed]
  13. L. Scolari, T. T. Alkeskjold, J. Riishede, A. Bjarklev, D. S. Hermann, A. Anawati, M. Nielsen, and P. Bassi, “Continuously tunable devices based on electrical control of dual-frequency liquid crystal filled photonic bandgap fibers,” Opt. Express 13(19), 7483–7496 (2005). [CrossRef] [PubMed]
  14. D. Noordegraaf, L. Scolari, J. Laegsgaard, L. Rindorf, and T. T. Alkeskjold, “Electrically and mechanically induced long period gratings in liquid crystal photonic bandgap fibers,” Opt. Express 15(13), 7901–7912 (2007). [CrossRef] [PubMed]
  15. T. T. Alkeskjold and A. Bjarklev, “Electrically controlled broadband liquid crystal photonic bandgap fiber polarimeter,” Opt. Lett. 32(12), 1707–1709 (2007). [CrossRef] [PubMed]
  16. A. Lorenz, H.-S. Kitzerow, A. Schwuchow, J. Kobelke, and H. Bartelt, “Photonic crystal fiber with a dual-frequency addressable liquid crystal: behavior in the visible wavelength range,” Opt. Express 16(23), 19375–19381 (2008). [CrossRef]
  17. V. K. S. Hsiao and C.-Y. Ko, “Light-controllable photoresponsive liquid-crystal photonic crystal fiber,” Opt. Express 16(17), 12670–12676 (2008). [PubMed]
  18. C.-H. Lee, C.-H. Chen, C.-L. Kao, C.-P. Yu, S.-M. Yeh, W.-H. Cheng, and T.-H. Lin, “Photo and electrical tunable effects in photonic liquid crystal fiber,” Opt. Express 18(3), 2814–2821 (2010). [CrossRef] [PubMed]
  19. V. V. Presnyakov, Z. J. Liu, and V. G. Chigrinov, “Infiltration of photonic crystal fiber with liquid crystals,” Proc. SPIE 6017, 60170J, 60170J-7 (2005). [CrossRef]
  20. L. Scolari, S. Gauza, H. Xianyu, L. Zhai, L. Eskildsen, T. T. Alkeskjold, S.-T. Wu, and A. Bjarklev, “Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals,” Opt. Express 17(5), 3754–3764 (2009). [CrossRef] [PubMed]
  21. H.-K. Lee, A. Kanazawa, T. Shiono, T. Ikeda, T. Fujisawa, M. Aizawa, and B. Lee, “All-optically controllable polymer/liquid crystal composite films containing the azobenzene liquid crystal,” Chem. Mater. 10(5), 1402–1407 (1998). [CrossRef]
  22. N. V. Tabiryan, S. V. Serak, and V. A. Grozhik, “Photoinduced critical opalescence and reversible all-optical switching in photosensitive liquid crystals,” J. Opt. Soc. Am. B 20(3), 538–544 (2003). [CrossRef]
  23. A. K. Abeeluck, N. M. Litchinitser, C. Headley, and B. J. Eggleton, “Analysis of spectral characteristics of photonic bandgap waveguides,” Opt. Express 10(23), 1320–1333 (2002). [PubMed]
  24. N. M. Litchinitser, S. C. Dunn, P. E. Steinvurzel, B. J. Eggleton, T. P. White, R. C. McPhedran, and C. M. de Sterke, “Application of an ARROW model for designing tunable photonic devices,” Opt. Express 12(8), 1540–1550 (2004). [CrossRef] [PubMed]
  25. K. Szaniawska, T. R. Wolinski, S. Ertman, P. Lesiak, A. W. Domanski, R. Dabrowski, E. Nowinowski-Kruszelnicki, and J. Wojcik, “Temperature tuning in photonic liquid crystal fibers,” Proc. SPIE 5947, 594705, 594705-6 (2005). [CrossRef]
  26. J. Tuominen, H. Hoffrén, and H. Ludvigsen, “All-optical switch based on liquid-crystal infiltrated photonic bandgap fiber in transverse configuration,” JEOS:RP 2, 07016 (2007). [CrossRef]

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