Photonic Liquid Crystal Fibers for Sensing Applications

1796 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 57, NO. 8, AUGUST 2008

Photonic Liquid Crystal Fibersfor Sensing Applications

Tomasz R. Wolinski, Member, IEEE, Aleksandra Czapla, Sławomir Ertman, Marzena Tefelska,Andrzej W. Domanski, Jan Wójcik, Edward Nowinowski-Kruszelnicki, and Roman Dabrowski

Abstract—The paper presents our latest experimental resultson the influence of temperature, an external electric field, andhydrostatic pressure on propagation properties of the photoniccrystal fibers infiltrated with liquid crystals of low and mediummaterial anisotropies. Measurand-induced shifts of the photonicbandgap wavelengths give information about the value of temper-ature, voltage, and pressure. Moreover, temperature-dependentpositions of the photonic bandgap wavelengths in the transmissionspectrum can serve to determine the thermal characteristics of theliquid crystal ordinary refractive index.

Index Terms—Liquid crystals (LCs), optical fiber devices,optical fiber measurement applications, optical fibers, sensors.

I. INTRODUCTION

M ICROSTRUCTURED optical fibers (MOFs) are a newclass of optical fibers with a regular structure of micro-

holes running along the axial direction, and they have beenthe subject of intense research over the past decade. MOFswith the periodic microstructure are called photonic crystalfibers (PCFs). There are two different types of PCFs: 1) witha solid core and 2) with a hollow core. In solid-core PCFs, therefractive index of the silica core is higher than the effectiverefractive index of the cladding, so the total internal refrac-tion (TIR) phenomenon is the mechanism responsible for theguiding of light. [Fig. 1(a)]. In hollow-core PCFs, the refractiveindex of the air core is always lower than the effective refractiveindex of the cladding, so light guiding by the TIR mechanismis not possible. In these fibers, only selected wavelengths canbe guided by the photonic bandgap (PBG) effect [Fig. 1(b)].PCFs have been intensively explored to achieve high bire-fringence (HB). Birefringence in PCFs usually results fromaccidental asymmetries in the cladding-hole lattice or fromthe intentional manipulation of the core and/or claddingstructure [1]–[3].

Manuscript received July 9, 2007; revised March 4, 2008.T. R. Wolinski, S. Ertman, M. Tefelska, and A. W. Domanski are with the

Faculty of Physics, Warsaw University of Technology, 00-662 Warsaw, Poland.A. Czapla is with the Faculty of Physics, Warsaw University of Technology,

00-662 Warsaw, Poland, and also with the Université du Québec en Outaouais,Gatineau, QC J8X 3X7, Canada (e-mail: [email protected]).

J. Wójcik is with the Maria Curie Sklodowska University, 20-031 Lublin,Poland, and also with the Military University of Technology, 00-908 Warsaw,Poland.

E. Nowinowski-Kruszelnicki and R. Dabrowski are with the Military Uni-versity of Technology, 00-908 Warsaw, Poland.

Color versions of one or more of the figures in this paper are available onlineat http://ieeexplore.ieee.org.

Digital Object Identifier 10.1109/TIM.2008.922077

Fig. 1. Mechanism of light propagation in PCF. (a) TIR. (b) PBG.

In specific applications, it is important to consider sensitivityof propagation and polarization properties to environmentalperturbations [4], [5]. An interesting case is to infiltrate PCFswith liquid crystals (LCs) that induce significant changes to theguiding properties. In empty solid-core PCFs with air holes, therefractive index of the core is higher than the refractive index ofthe cladding, and the whole spectrum of the input light is guidedby the modified total internal reflection (mTIR) mechanism,which is well known and is similar to the waveguiding effectwithin a conventional fiber.

An LC introduced into a PCF significantly changes its guid-ing properties; the effective refractive index of cladding in-creases and, in most cases, is higher than the refractive index ofthe core. Hence, the light can be guided due to the PBG effect.This guiding mechanism relies on coherent backscattering ofthe light into the core, whereas only selected wavelengths ofinput light can propagate within the fiber.

LCs seem to be particularly interesting substances to infil-trate PCFs, since their optical properties strongly depend onthermal, electric, magnetic, and optic fields. The LC-infiltratedPCF structures, which we call photonic LC fibers (PLCFs),open up a wide range of new possibilities for tuning light prop-agation properties due to the fact that LCs are materials with astrongly adjustable anisotropy [6]–[9]. Moreover, temperatureswitching between two propagation mechanisms (mTIR andPBG) in a single PLCF has been demonstrated [10].

The paper reports the latest experimental results on tem-perature, hydrostatic pressure, and electrically induced tuningof the PLCF propagation and polarization properties, in viewof potential applications in all-optical fiber optic sensors, oftemperature, an electric field (E-field), or hydrostatic pressure.

0018-9456/$25.00 © 2008 IEEE

WOLINSKI et al.: PHOTONIC LIQUID CRYSTAL FIBERS FOR SENSING APPLICATIONS 1797

Fig. 2. PCFs used as PLCF host matrix. (a) MCSU 1023 PCF. (b) LMA-PM-5PCF (produced by CrystalFibre).

Fig. 3. Experimental setup for investigating electrical tuning of PCFs filledwith LCs.

Simultaneously, we propose a new method of indirect mea-surement of LC ordinary refractive index thermal characteris-tics. We also discuss preliminary results of hydrostatic pressureeffects on polarization properties of HB PLCFs.

II. EXPERIMENTAL SETUPS AND MATERIALS

As host structures to be infiltrated with LCs, we used twodifferent PCFs (Fig. 2). The first one is a prototype isotropicPCF manufactured at the Maria Curie Sklodowska University(MCSU), Lublin, Poland [Fig. 2(a)]. This structure contains asolid core surrounded with nine rings of air holes character-ized by a diameter and hole spacing of 4.8 µm and 6.5 µm,respectively. This fiber was used to investigate the influenceof temperature and an external E-field. The second host HBPCF, which is denoted the LMA-PM-5 PCF, combines stressrod applied birefringence, and its cross section is shown inFig. 2(b). Its solid core with a diameter of 5 µm is surroundedby four rings of holes. PLCFs based on the LMA-PM-5 PCFwere used to investigate hydrostatic-pressure-induced effects.

The experimental setup for temperature- and external-electric-field-induced measurements is presented in Fig. 3. Weused a ∼50-cm-long photonic crystal host fiber in which onlya ∼10-mm-long section was filled with the guest nematic LC.The input light from a broadband source was coupled into anempty section of the PCF. The terminal section of the PCF filledwith LCs, i.e., the PLCF under investigation, was placed into athermoelectric module, allowing for temperature regulation inthe 10 ◦C–120 ◦C range with ∼0.1 ◦C long-term stability andan E-field regulation in the 0–1000-V range with a frequencyfrom 50 Hz to 2 kHz. The optical signal from the outputof the PLCF was analyzed by the Ocean Optics fiber opticspectrometer HR4000.

A special sensing head was used to investigate the influenceof hydrostatic pressure on light propagation in the HB PLCFs

(Fig. 4). First, ∼20 mm of the 35-cm-long HB PCF wasfilled with LCs, and then, the LCs were moved to the middleof the HB PCF by using high-pressure air. The HB PLCFwas next introduced into a high-pressure chamber through aspecially designed lead-through system. Then, the HB PLCFsample was connected to the white-light source and to thespectrometer by using capillary connections and single-mode(SM) leading fibers. The measurement apparatus also includeda tunable laser source (Tunics Plus CL) operating at the thirdoptical window (spectral range 1500 ÷ 1640 nm) and a modularPAT 9000B polarimeter (Tektronix) polarization analysis of theoutgoing light from the HB PLCF. Finally, hydrostatic pressure(from the range 20–70 MPa) was applied to the chamberand was modified and controlled with a deadweight pistonmanometer.

LCs are organic materials that consists of geometricallyanisotropic molecules. The elongated shape of molecules leadsto long-range orientation order due to the van der Waalsforces. Nematic LCs have only long-range orientation orderof molecules in a long axis, which means that moleculesare parallel, but their centers of gravity are randomly distrib-uted. The aligned nematic LC molecules, on the average, arecharacterized by one symmetry axis called the director. Theoptical properties of nematic LCs differ for waves travelingnormal or parallel to the director, and LCs are characterizedby two refractive indices: 1) ordinary and 2) extraordinary.Fig. 5 shows the thermal characteristics of the refractive indicesof three LCs with medium birefringence used in our work:1) a typical nematic PCB (4’-n-pentyl-4-cyanobiphenyl);2) 6CHBT 4-(trans-4-n-hexylcyclohexyl) isothiocyanatoben-zene; and 3) an experimental nematic mixture abbreviated as1294-1b. For the 1702 LC mixture, the thermal dependences ofrefractive indices have yet to be measured. Table I presents therefractive indices and optical and electrical anisotropies of theLC mixture. All of the LC mixtures used for PCF infiltrationwere synthesized at the Military University of Technology,Warsaw, Poland.

III. PLCF AS A SENSING ELEMENT FOR TEMPERATURE

The PCFs used as a host structure are a typical solid-coreholey fiber with the index guiding mechanism. However, theLC material introduced into the holes of the cladding regionnot only influences the properties of light propagation but canalso change the guiding mechanism. The guiding mechanismof the PLCF depends on the effective refractive index of thenematic LC that strongly depends on the ambient temperatureand the molecular alignment. Due to flow-induced orientationduring the filling process of the PLCF, planar molecular align-ments dominate over the radial geometry, which means thatthe propagating light experiences an effective refractive indexthat is close to the ordinary refractive index no of the guestLC. In most cases, the no of the guest LC is higher than therefractive index of the core. Hence, the light can be guided dueto the PBG effect. PBG positions in the PLCF can be calculatedwith the help of the ARROW model [11]–[13]. In this model,the infiltrated holes are treated as isolated waveguides. Minimain the transmission spectrum occur for cutoff wavelengths of


Fig. 4. Experimental setup to investigate propagation and polarization properties of the HB PLCF under the influence of hydrostatic pressure, temperature, andan external electric field.

Fig. 5. Refractive indices of the LC with medium birefringence. PCB,6CHBT, and experimental LC mixture 1294-1b, compared with the refractiveindex of the silica glass.

TABLE IREFRACTIVE INDICES AND OPTICAL (ELECTRICAL) ANISOTROPIES OF

NEMATIC LCS USED AS PLCF GUEST MATERIALS (22 ◦C, λ = 589 nm)

following modes propagated in one hole. The position of theseminima can be calculated according to

λm =2d

m + 1/2

√n2

LC − n2Si (1)

where λm is the wavelength corresponding to the minimumin the fiber’s transmission spectrum, d is the diameter of thehole, m is a natural number, and nSi and nLC are the refractiveindices of silica glass and the mixture filling the hole, respec-tively. Transforming (1) in the form

nLC =

√(λm

(m +

12

) /2d

)2

+ n2Si (2)

a simple relation between an ordinary refractive index of theguest LC and the position of the bandgaps in the transmissionspectrum can be established.

The experiment results of thermal bandgap tuning in theMCSU-1023 PCF filled with the medium-birefringence 1702LC mixture (∼0.3) are shown in Fig. 6. The thermal de-pendences of its refractive indices have yet to be measured;however, the effect of thermally induced PBG tuning allows

Fig. 6. Thermal tuning in MCSU-1023 PCF filled with the 1702 LC mixture.(a) Red shift is observed if the ordinary refractive index is decreasing withtemperature. (b) Blue shift could be observed if the ordinary refractive index isincreasing with temperature.

for a qualitative description of the no thermal characteristic.Since the LC molecules are predominantly oriented along thefiber axis (flow-induced orientation), the bandgaps’ position isdetermined by the value of no, and if no is decreasing, a blueshift of PBGs is observed [Fig. 6(a)]. Similarly, any increase inno leads to a red shift of PBGs [Fig. 6(b)]. This phenomenon isqualitatively in agreement with (2).

In the transmission spectra shown in Fig. 6, three possi-ble positions of PBGs were observed: 1) for the range of540–575 nm; 2) for the range of 650–720 nm; and 3) for therange of 800–950 nm (at 21◦C). Due to the thermally inducedchanges in the refractive indices of the LC-infiltrated PCF, wecan smoothly tune the positions of the PBGs and, consequently,the wavelengths guided in the PLCF (Fig. 7). As a result, theoperating wavelength strongly depends on temperature, and thisopens up a range of perspective applications of the PLCF.

Summing up by using, as a light source, a laser diodeoperating at a defined wavelength, we can measure temperature


Fig. 7. Thermal tuning three differing positions of the PBGs under a givenoptical power value in the PLCF filled with the 1702 LC mixture.

Fig. 8. Optical fiber temperature sensor operating at the wavelength 565 nm.Intensity of the output light increases with temperature.

with high precision. Fig. 8 presents temperature influences onpropagating wavelengths in PLCF. In the temperature rangefrom 61 ◦C to 80 ◦C, the wavelength of the transmitted lightdecreases with increasing temperature.

IV. PLCF AS A SENSING ELEMENT FOR E-FIELD

The first effect that was observed after increasing the voltagewas the decay of the optical power transmitted in the PLCF.For the PCF filled with PCB, increasing the voltage to 41 V(2 kHz) caused an almost complete decay of light at the outputof the fiber. In the PLCF manufactured by using the 1294-1bmixture, the maximum decay of the output optical power wasobserved for 160 V. Further increasing the voltage resulted in anincrease of the optical power transmitted in the PLCF, but thepositions of PBGs were different than they are in the off-voltagestate (Figs. 9 and 10). It seems that electrical tuning of PLCFsallows for switching between two different positions of PBGs,which depend on the ordinary refractive index of LCs in theoff-voltage state and the extraordinary index in the high-voltagestate. This behavior does significantly differ from temperaturetuning of PLCFs, where the positions of PBGs can be smoothlychanged.

The influence of the E-field on PLCFs is different belowand above the specified threshold voltage (VT) value. For thePLCF filled with PCB, VT ≈ 41 V, and for that filled with

Fig. 9. Selective light propagation in the PLCF filled with PCB. Electricaltuning of PBG positions in the PLCF filled with PCB.

Fig. 10. Selective light propagation in the PLCF filled with the 1294-1bmixture. Applied voltage results in a decay of the optical power transmittedin PLCF.

Fig. 11. Normalized optical power for selected wavelengths as a function ofthe applied voltage for the PCF filled with PCB.

1294-1b, VT ≈ 160 V (in practice, the value of the thresholdvoltage VT can be adjusted by using different PCFs and LCs).Initially, the voltage increase to VT causes the gradual decay ofthe optical power. However, a further voltage increase above thethreshold value induces electrically tuned PBGs in the PLCFs(as observed in Figs. 9 and 10). In the result, the influenceof the E-field strongly depends on the operating wavelength.Examples of responses to increasing the voltage for selectedwavelengths are shown in Figs. 11 and 12.


Fig. 12. Normalized optical power for selected wavelengths as a function ofthe applied voltage for the PCF filled with the 1294-1b LC mixture.

Fig. 13. Examples of the LC molecules orientation within the holes of micro-structured fibers. (a) Planar. (b) Radial. (c) Axial. (d) Example of anisotropicmolecule distribution [(a), (b), and (c) are isotropic].

The choice of the operating wavelength may depend on theperspective applications. From the practical point of view, thefollowing are four useful choices of the operating wavelength:

1) with “linear” dependence in the range from 0 V to VT—tomeasure low intensities of an E-field (562 and 800 nm inFig. 11 and 635 nm in Fig. 12);

2) with “linear” dependence for voltages higher than VT—tomeasure high intensities of an E-field (562 nm in Fig. 11and 484 nm in Fig. 12);

3) with the low level of signal in the range from 0 V toVT—in automatics, to signal that the E-field value ishigher than VT (740 nm in Fig. 11 and 599 nm in Fig. 12);

4) with the low level of signal for voltages higher the VT—inautomatics, similar to 3).

It must be mentioned that there are some potential issues thatmust be discussed in the context of the practical applications.The first one is that the refractive indices of LCs are usu-ally highly temperature dependent, which may result in un-predictable behavior with changing environmental conditions.This issue can be solved by using special LC mixtures withreduced thermal sensitivity (such as the 1294-1b LC mixturepresented in Fig. 5). The second potential issue concerns the so-called “memory effects,” which may occur in PLCFs subjectedto a high E-field—the field-reoriented LC molecules may be“frozen,” even if the E-field is no longer present. This problemcan be eliminated by using special aligning layers within thefiber holes. Such layers with high anchoring energy can lead toone of the specified molecule orientations (Fig. 13) [14].

Fig. 14. Transmission spectra for the LMA-PM-5 PCF infiltrated with the6CHBT LC mixture—influence of hydrostatic pressure.

V. PLCF AS A SENSING ELEMENT FOR

HYDROSTATIC PRESSURE

Hydrostatic pressure can also change the optical properties ofthe PLCF. The positions of PBG maxima in transition spectradepend not only on the refractive index of the holes’ infiltratingmaterial but also on the geometry (diameter) of the capillary.Subsequently, any change in the holes’ diameter induces achange in the PBG wavelength.

In our experiment, we used an LMA-PM-5 PCF (35 cm long)filled with 6CHBT LC (section of 2 cm). The 6CHBT LC ischaracterized by both refractive indices that are higher thanthe refractive index of the silica glass used for the HB PCFfabrication process, which means that propagation in the fibercore is possible only for the wavelengths corresponding toPBGs formed in the cladding.

The HB PLCF sample was connected to the white-lightsource and to the spectrometer. In transmission spectra withoutany external perturbation, two possible ranges for the lightpropagation were observed. It was observed that hydrostaticpressure resulted in the narrowing of the changes in the direc-tion of longer wavelengths. This effect was particularly evidentfor the range of 600–750 nm (Fig. 14) in which the observednarrowing effect was about 40 nm. The preliminary resultsobtained are particularly interesting in view of our previousresearch on the influence of the external perturbations on PLCF.Although, in the case of an external E-field and temperature,PBG tuning was observed, under hydrostatic pressure, therewas a PBG tuning effect. Instead, we observed a one-sidenarrowing effect of the PBGs in transmission spectra (Fig. 14).As can be seen in Fig. 15, the operating wavelength dependson the hydrostatic pressure. Hence, by injecting only selectedwavelengths into the PLCF and observing the output lightsensitivity, we are able to measure the value of hydrostaticpressure (Fig. 15).

Subsequently, hydrostatic-pressure-induced effects on thepropagation properties of the HB PCF (by using a tunableTunics Plus laser operating at IR wavelengths) were also in-vestigated. The polarimeter PAT 9000B with the POL 9320FIRmodule served as an analyzer. On the Poincaré sphere


Fig. 15. Normalized optical power for selected wavelengths as a function ofhydrostatic pressure for the LMA-PM-5 PCF with the 6CHBT LC mixture.

Fig. 16. Change of polarization state in the LMA-PM-5 PCF with 6CHBT LCunder hydrostatic pressure—visualization of the Poincaré sphere.

representation, we observed repeatable hydrostatic-pressure-induced evaluations of the polarization state (Fig. 16). Thiseffect indicates that hydrostatic pressure can tune the polariza-tion properties of the HB PLCF. Moreover, the result obtainedsuggests that the phase birefringence is being changed underthe influence of hydrostatic pressure.

Then, we calculated the pressure sensitivity of the phase bire-fringence under the hydrostatic pressure by using the followingformula:

K =2π

TpL∼= 0.18

[rad

m · MPa

](3)

where Tp is the value of hydrostatic pressure that is responsiblefor the 2π phase shift between two polarization eigenmodes,and L is the fiber length. Further experiments are in progress.

VI. CONCLUSION

We have demonstrated the propagation effects in PLCFscomposed of a PCF filled with LCs. As a host material, we usedeither isotropic or HB PCF structures. As an “active” elementof the PLCFs, we used nematic LCs with low and mediumbirefringence. The changes in the output optical spectrum in-duced by temperature, an E-field, and hydrostatic pressure canbe used for the measurement of these quantities. The spectralshifts of the PBG wavelengths are repeatable and are typical

for PLCFs that operate in the PBG regime. It is evident that byusing different combinations of PCFs and LCs, we can proposea new method of optical fiber sensing with wide sensitivity andoperating regions. The perspective new sensing method allowsfor the measurement of external factor distribution in a specifiedarea by using an array of PLCF sensing elements.

At the current stage, it is difficult to envisage any practicalapplications of PLCFs to real sensing systems, since PLCFscan respond simultaneously to changes induced by numerousenvironmental parameters (this can be a basis for multiparam-eter sensing). However, from the technological point of view,a far greater care must be taken to ensure the repeatability ofPLCF-based sensors. Moreover, when a single parameter has tobe measured, there is a great need for either compensation ortaking into account, at the data processing stage, the influenceof other environmental parameters. All of this is a subjectof further research and optimization activities that are still inprogress.

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Tomasz R. Wolinski (M’92) received the M.Sc.degree (with honors) in applied physics, the Ph.D.degree (with honors) in physics, and the D.Sc. degreein physics–optics from the Warsaw University ofTechnology, Warsaw, Poland, in 1980, 1985, and1995, respectively.

He is currently a Professor with the Faculty ofPhysics, Warsaw University of Technology, wherehe has been the Head of the Optics Division since1997. He is the author or a coauthor of more than200 journal and conference papers, including two

review chapters in Progress in Optics and Encyclopedia of Optical Engineeringand more than 60 peer-reviewed journal papers. He is an Associate Editor forOptical Engineering and Opto-Electronics Review. He has served as an invitedspeaker at several international conferences in recent years. He is the holder ofseven patents in the U.S., Canada, and Poland. His current research interestsinclude polarization phenomena in optical fibers and liquid crystals, photonic(liquid) crystal fibers, and fiber optic sensors and systems.

Dr. Wolinski was the President of the International Society for Optical Engi-neers (SPIE) Poland Chapter in 2002, which transformed into the PhotonicsSociety of Poland in 2008. He was the Chair of the Optoelectronics Section ofthe Committee of Electronics and Telecommunications of the Polish Academyof Sciences in 2007. He has been the Vice Chair of the Polish Committee ofOptoelectronics since 2003 and a Fellow of SPIE since 2004. He is a memberof the Optical Society of America. He is the General and Founding Chair ofSPIE’s series of International Congresses of Optics and Optoelectronics, whichwas initially held in Warsaw in 2005, and was the Technical Program Chairof the IEEE Instrumentation and Measurement Technology Conference held inWarsaw in 2007. He was granted the Scientific Title of Professor of Physics bythe President of Poland in 2002.

Aleksandra Czapla was born in Warsaw, Poland, in1982. She received the M.Sc. degree in physics fromthe Warsaw University of Technology in 2006. Shehas been working toward the Ph.D. degree with theFaculty of Physics, Warsaw University of Technol-ogy, since 2006 and with the Université du Québecen Outaouais, Gatineau, QC, Canada, since 2008.

For the last three years, her research activities havebeen focused on optic fiber applications. She is par-ticularly interested in long-period grating fibers andphotonic crystal fibers infiltrated with liquid crystals.

Ms. Czapla is a member of the International Society for Optical Engineers(SPIE). She received the Third Prize at the National Competition for Best M.Sc.Thesis in Optoelectronics in 2006.

Sławomir Ertman is currently working toward thePh.D. degree with the Faculty of Physics, WarsawUniversity of Technology, Warsaw, Poland.

His scientific interest focuses on fiber optics,particularly on photonic crystal fibers filled withliquid crystals from both experimental and theo-retical approaches.

Mr. Ertman is a member of the Photonics Societyof Poland and the International Society for OpticalEngineers (SPIE). He received the First Prize at theNational Contest for Best M.Sc. thesis in the field of

optoelectronics in 2005.

Marzena Tefelska was born in Kolobrzeg, Poland,in 1983. She received the M.S. degree and Engi-neer diploma in optoelectronics from the WarsawUniversity of Technology, Warsaw, Poland, in 2007.She is currently working toward the Ph.D. degreewith the Faculty of Physics, Warsaw University ofTechnology.

Her research interests include photonic liquidcrystal fibers, telecommunication fibers, liquid crys-tals, and sensor fibers.

Ms. Tefelska has been a member of the Interna-tional Society for Optical Engineers (SPIE) since 2007. She received the ThirdPrize at the Adam Smolinski Contest for the best master thesis for 2006–2007in the optoelectronics discipline.

Andrzej W. Domanski received the M.S.E.E.,Ph.D., and D.Sc. degrees from the Warsaw Univer-sity of Technology, Warsaw, Poland.

He is currently a Professor of optics with theFaculty of Physics, Warsaw University of Tech-nology. He is the holder of more than 150 scientificpatents and patents on polarization and diffractionoptics, magnetooptics, optical fiber sensors, and op-tical tomography.

Dr. Domanski is a Fellow of the InternationalSociety for Optical Engineers (SPIE).

Jan Wójcik received the M.S. degree in chemistry and the Ph.D. degreein physical chemistry from the Maria Curie-Sklodowska University, Lublin,Poland, in 1971 and 1982, respectively.

He is the Head of the Optical Fibers Technology Group, Department of Op-tical Fiber Technology, Maria Curie Sklodowska University. He is also with theMilitary University of Technology, Warsaw, Poland. Since 1975, his researchactivity has been concerned with the design, fabrication, and measurement ofoptical fibers for both telecommunications and special applications. He haspublished more than 150 papers on optical fiber technology.

Edward Nowinowski-Kruszelnicki received the M.S. degree in solid-statephysics from the Warsaw University of Technology, Warsaw, Poland, in 1967and the Ph.D. degree in solid-state engineering from the Military University ofTechnology (MUT), Warsaw, in 1974. His thesis concerned the application ofultrasonic delay lines in radar technology.

He is currently with the Faculty of Engineering, Chemistry, and AppliedPhysics, MUT. His main research interests include liquid crystal technology ofoptical elements, photonic fibers infiltrated with liquid crystals, liquid crystalplanar waveguides, photoconductive polymers, and photorefractive effects.

Roman Dabrowski received the M.Sc. degree inpolymer technology from the Warsaw University ofTechnology, Warsaw, Poland, in 1961 and the Ph.D.and Sc.D. degrees in organic semiconductors studiesfrom the Military University of Technology (MUT),Warsaw, in 1966 and 1970, respectively.

He is currently a Full Professor of organic chem-istry and the Director of the Institute of Chemistry atMUT. In 1975, he changed his interest to liquid crys-tals (LCs), searching for new LC materials for dis-plays and photonic applications, and he investigated

the relations between the chemical structure of molecules and their mesogenicand physical properties. He is the author of more than 300 publications andconference presentations.

Dr. Dabrowski is a member of the scientific and organizing committees of theInternational Liquid Crystal Conferences. He is a recipient of the Frederick’sMedal.

Photonic Liquid Crystal Fibers for Sensing Applications

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Transcript of Photonic Liquid Crystal Fibers for Sensing Applications