High-accuracy Universal Polarimeter Method Research Articles

A high-accuracy universal polarimeter study of optical anisotropy and optical activity in laminated collagen membranes.

A novel method for fabricating anisotropic collagen membranes, which regulate the preferred orientation, is developed. The high-accuracy universal polarimeter (HAUP) method is used for simultaneous and quantitative evaluations of the optical anisotropy and optical activity. The evaluation of these optical quantities, enabled by the HAUP method, is beneficial to the field of tissue engineering.

Temperature-dependent optical rotatory power in the presence of birefringence of KTA and KTP crystals by the high-accuracy universal polarimeter method at 632.8 nm wavelength

Temperature-dependent simultaneous measurement of birefringence and optical rotatory power (ORP) for orthorhombic crystals of potassium titanyl phosphate (KTP) and potassium titanyl arsenate (KTA) has been achieved by using the high-accuracy universal polarimeter method at 632.8 nm wavelength. The birefringence and ORP changes along the (110) planes for KTA and KTP crystals were found to have a nearly parabolic form for the temperature range 297–493 K. The thermal variation coefficients were found to be 0.9 (5) × 10−5 K−1and 5.6 (3) × 10−8 K−2for KTA and 0.9 (5) × 10−5K−1and 5.7 (3) × 10−8 K−2for KTP. The ORPs at 297 K were found to be 20.0 (20) and 20.5 (15)° mm−1for KTA and KTP, respectively. The thermal variation coefficients of the ORP were found to be 1.8 (2) × 10−3° mm−1 K−1and 1.1 (1) × 10–5° mm−1 K−2for KTA and 1.9 (2) × 10−3° mm−1 K−1and 1.2 (1) × 10−5° mm−1 K−2for KTP.

An application of the advanced high-accuracy universal polarimeter to the chiroptical measurement of an intercalated compound K4Nb6O17 with high anisotropy

The advanced high-accuracy universal polarimeter (HAUP) method was applied to observe anisotropic and chiroptical properties of an intercalated azobenzene derivative compound into K4Nb6O17 crystals. Prior to the HAUP measurement of the intercalated compound, we extended the HAUP method employing a conventional light source system composed of Xe or D2 lamps and a monochromator instead of a laser system. The performance of the advanced HAUP system was evaluated and we determined the parasitic ellipticities of the cross polarizers, which are essential for obtaining accurate values. The optical system was applicable to simultaneously measure the linear dichroism (LD), circular dichroism (CD), linear birefringence (LB) and circular birefringence (CB) spectra of an intercalated compound in the ultraviolet and visible regions. We found the Kramers–Kronig relation between CB and CD as well as in the case of LB and LD. Changes in LB and LD signals as obtained from HAUP measurements originated from the molecular orientation of guest molecules by the intercalation. Moreover, CB and CD signals indicated the appearance of induced chirality in the intercalated azobenzene derivative compound. These results demonstrated the usefulness of the HAUP system for evaluating the molecular conformation of chiral anisotropic specimens.

Optical Anisotropy of TGS x · TGSe1 − x Compounds

An aqueous solution technique has been used for the growth of TGS x · TGSe1 − x mixed crystals. The birefringence and rotation of the optical indicatrix of x selected samples has been measured using the high-accuracy universal polarimeter method. Simple relationships between the spontaneous optical quantities in the ferroelectric phase and the spontaneous polarization are observed.

Optical Activity Induced by Helical Arrangements of Tryptamine and 4-Chlorobenzoic Acid in Their Cocrystal

Optical rotatory powers of chiral cocrystals formed from the achiral molecules tryptamine and 4-chlorobenzoic acid were determined by the HAUP (high accuracy universal polarimeter) method. These cocrystals belonged to space group P2(1)2(1)2(1), and their absolute configuration was confirmed by the Flack parameter. In the M-crystal, 2-fold helical arrangements are formed in a counterclockwise direction between the two components through the quaternary ammonium salt bridge, hydrogen bond, and the aromatic pi-piinteraction along the c axis, while clockwise helices alone exist in the P-crystal. Large rotatory powers rho(3)(M) = -355 and rho(3)(P) = +352 deg mm(-)(1) were obtained along the c axis in the M- and P-crystal, respectively, at 632.8 nm and 303 K. The magnitude was 10 to 100 times larger than those for ordinary organic crystals. Further, it was confirmed that the negative sign was induced by the counterclockwise helical structures and the positive sign by the clockwise helices. In contrast, the rotations along the a and b axis which are in perpendicular directions to the screw axis were rho(1)(M) = +138, rho(1)(P) = -140 deg mm(-)(1), and rho(2)(M) = -56, rho(2)(P) = +58 deg mm(-)(1), much smaller than rho(3)(M) and rho(3)(P) . The results revealed that the helically arranged aromatic pi electrons as well as the helical ionic and hydrogen bond networks in the crystal contributed to the enhancement of the magnitude of these rotations.

Measurement of circular birefringence and circular dichroism of the single crystals of lambda-(+)589- and delta-(-)589-tris(ethylenediamine)cobalt(III) triiodide monohydrate by the extended HAUP method.

We have achieved measuring four optical parameters simultaneously, namely, linear birefringence (LB), circular birefringence (CB), linear dichroism (LD), and circular dichroism (CD), of single crystals of Lambda-(+)(589)- and Delta-(-)(589)-tris(ethylenediamine) cobalt(III) triiodide monohydrate (1) along the <001> plane at the fixed wavelength (514.5 nm). Such measurements are possible only when the High Accuracy Universal Polarimeter (HAUP) is employed; it is called the extended HAUP method. Our experimental results showed that both LB and LD of the Lambda-(+)(589)-(1) crystal have the same magnitude as those of the Delta-(-)(589)-(1) crystal. It was also revealed for the first time that the CB data of crystals of Lambda-(+)(589)-(1) and Delta-(-)(589)-(1) are almost of the same magnitude, but are of opposite sign, reflecting their opposite absolute configurations. On the other hand, although the CD data obtained for Lambda-(+)(589)-(1) is almost three times larger than that for Delta-(-)(589)-(1,) these CD data are also opposite in sign, as expected from the opposite chirality of crystals. .

Optical study on a phase transition of fresnoiteBa2Si2TiO8

Fresnoite ${\mathrm{Ba}}_{2}{\mathrm{Si}}_{2}{\mathrm{TiO}}_{8}$ is a ferroelectric with promising piezoelectric uses that exhibits unusual pyroelectric, elastic, and other property anomalies close to 433 K. X-ray diffraction analyses at 297 and 573 K by Markgraf et al. determined the space group to be $P4\mathrm{bm}$ at both temperatures and appeared to exclude the possibility of these anomalies being caused by a structural phase transition; a convincing alternative interpretation of the origin of these anomalies has not yet been reported. The high accuracy universal polarimeter (HAUP) method offered an alternative investigative approach. A primary difficulty in the present study was ensuring that the illuminated volume of the sample crystal was single and without domain texture. After having solved this problem, the method has established the point group of fresnoite as $4mm$ above 433 K, and as optically active below it. The single gyration tensor component ${g}_{12}$ appears abruptly but continuously on cooling below this temperature and increases with decreasing temperature, reaching $5.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ at 360 K. Thus fresnoite is found to undergo a structural phase transition of second order from a $4mm$ phase to an optically active nonenantiomorphic point group. Combining the change of optical activity with that of the birefringence leads us to the conclusion that the point group below 433 K is $\mathrm{mm}2.$ The present study illustrates the unique and deep insight the HAUP method can provide into condensed-matter phase transitions.

Optical studies in liquid crystals using the high-accuracy universal polarimeter

The so-called high-accuracy universal polarimeter (HAUP) is introduced as a tool to study optical properties of liquid crystals. It is shown that besides homogeneous crystals, the HAUP method also permits to investigate inhomogeneous materials, provided that the optical parameters vary slowly on a wavelength scale. The technique is especially useful when small effects are sought. Measurements are presented for several twisted nematic samples. Twist angles are measured with high accuracy and non-adiabatic effects for light propagation, such as apparent indicatrix rotations or effective gyrations, are easily detected. The results agree well with the predictions of a first-order perturbation treatment for light propagation through a stratified medium. Finally, the changes of the director profile are analyzed in a planar sample that presents a chiral nematic to smectic-A transition. The experimental data indicate that if the rubbing directions of the cell are not strictly parallel, the molecules at the surfaces undergo small twists in both phases, and the twist parameters are determined.

High-accuracy universal polarimeter measurement of optical activity and birefringence of α-quartz in the presence of multiple reflections

The high-accuracy universal polarimeter (HAUP) method for simultaneous measurement of birefringence and optical activity in crystals is used when multiple reflections at the plate faces cause modulated variation of the optical parameters. We applied the HAUP method to obtain the birefringence and gyration tensors of α-quartz as a function of temperature in the range 25–100 °C at λ=632.8 nm. Results for birefringence Δn= ne-no and nonnull gyration tensor components g11,g22=g11, and g33, with samples cut in different crystallography planes, are consistent with crystal symmetry and in good agreement with other reported values. For example, the temperature coefficient d(Δn)/dt for a cut perpendicular to the optical axis is -1.06× 10-6 (°C)-1,g11=(5.9±0.4)×10-5, and g33=-(10.1±0.2)×10-5 at 24 °C.

Invitation to chiral physics

Although measurement of the optical activity of solids had been impossible for 170 years since its discovery by Arago (1811), we have developed a method called HAUP (high accuracy universal polarimeter), which enables one to measure simultaneously optical activity, birefringence, and rotation of the indicatrix of any crystals, even those belonging to the monoclinic and triclinic systems. Thus the HAUP has opened a new research field in condensed matter physics. This article reviews our applications of the HAUP method to studies on several unsolved problems in this science. It includes an understanding of the origin of structurally incommensurate phases, a revelation of the twinning mechanism of the ferroelectric domains, the first exploration of optical properties of monoclinic crystals, the determination of correct crystal symmetries of transparent PLZT ceramics, first measurements of anisotropic gyrations of helical polymers, and measurements of reciprocal and non-reciprocal optical activity of high temperature superconductors. It is important to note that these problems could be solved only by making use of the crucial property of optical activity. Summing up the present study, we should like to emphasize the necessity of the new research field, ‘chiral physics’where axial tensors like gyration can play major roles.

Development of novel method for measuring optical activity of solids and its applications

Although measurement of the optical activity of solids has been impossible for the 180 years since its discovery by Arago (1811), we have developed a method called HAUP (high accuracy universal polarimeter), which enables one to measure simultaneously optical activity, birefringence, and rotation of the indicatrix of any crystals, even those belonging to the monoclinic and triclinic systems. Thus HAUP has opened new research fields in condensed matter science. This article reviews our applications of the HAUP method to studies on several unresolved problems in this science. It includes an understanding of the origin of structurally incommensurate phases of some ferroelectrics, the determination of the correct crystal symmetries of the transparent PLZT ceramics, first measurements of anisotropic gyrations in helical polymers, and optical activity of HTSC. It is important to note that these problems could be solved only by making use of the crucial property of optical activity.

Optical Activity of Oxo Amide Crystals

It has been known that oxo amide crystals made up of achiral molecules can be photochemically converted into optically active β-lactams by irradiation with a high pressure mercury lamp. Although the oxo amide crystal belongs to an enantiomorphic class D2, its optical activity could not be detected so far. We successfully measured the components of the gyration tensor of the oxo amide crystal by using the HAUP (high accuracy universal polarimeter) method: g11 = −3.5 × 10-4 (−79°/mm), g22 = −1.4 × 10-4 (−32°/mm), g33 = −3.0 × 10-4 (−68°/mm) at 305 K, where the optical rotatory powers are indicated in parentheses. It has been proved by direct experiments that the optical activity of the reactant and the product in this reaction system remains unchanged over the photocyclization process.

Optical properties of superconducting Bi2Sr2CaCu2O8.

A fundamental optical study was performed on superconducting ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8}$ by using a high-accuracy universal polarimeter (HAUP). As this crystal is strongly linearly dichroic, we developed the extended HAUP theory which includes the treatments of the optical dichroisms. After having determined the optical nature of the crystal, we applied the extended HAUP method to a thin (001) plate specimen with light traveling to the front and rear directions in the specimen. These two experiments permitted us to separate the reciprocal and nonreciprocal optical effects. No sign of the nonreciprocal effects was found in the HAUP transmission experiment. A gyration tensor component ${\mathit{g}}_{33}$ takes place suddenly at ${\mathit{T}}_{\mathit{c}}$ (90 K), increases with decreasing temperature, and reaches 1.87\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ (36\ifmmode^\circ\else\textdegree\fi{}/mm of rotatory power) at 15 K. A steep change of birefringence \ensuremath{\Delta}n with temperature also occurs below ${\mathit{T}}_{\mathit{c}}$. From the behaviors of ${\mathit{g}}_{33}$ and \ensuremath{\Delta}n with temperature, it can be concluded that the crystal undergoes a second-order phase transition at ${\mathit{T}}_{\mathit{c}}$ into an optically active class. The crystal manifests large linear dichroism, i.e., \ensuremath{\Delta}m=-2.2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}2}$. \textcopyright{} 1996 The American Physical Society.

Optical activity of solid polymers

Abstract The methods of measuring optical activity of solid polymers are reviewed. The extreme difficulty of the methods is exhibited in serious drawbacks of the traditional statistical methods. The invention of HAUP (high accuracy universal polarimeter) method by Kobayashi et al. has opened a way to perfect measurements of gyro-optical properties of any solids. As an example of application of the HAUP method to helical polymers, the process of analyzing the gyration tensor components of poly-L-lactic acid and poly-D-lactic acid is illustrated in details.

Optical Study of Pb1-xLax(ZryTiz)1-(x/4)O3

Optical properties of La-modified lead zirconate titanate (9/65/35) in the intermediate phase were studied by the HAUP (high accuracy universal polarimeter) method. It was found that this material is optically inactive under electric fields. On the other hand, temperature dependence of the quadratic electrooptic coefficient was measured after careful corrections using the HAUP method.

Optical Properties of Gd2(MoO4)3 Studied by High Accuracy Universal Polarimeter (HAUP) Method*

Birefringence Δnc of the improper ferroelectric Gd2(MoO4)3 was accurately measured by using the HAUP (high accuracy universal polarimeter) method as a function of temperature and electric field. Electric field dependence of Δnc was found to show unique behaviour in the vicinity of Tc. It is of importance that the linear electrooptic coefficient r63 changes its sign and manifests a sharp peak in the close vicinity of Tc. This result coincides qualitatively with the result reported by Kobayashi and Miyazaki, but disagrees with other reports.

Optical Activity of Incommensurate Phases of (C3H7NH3)2MnCl4

By applying the HAUP (high-accuracy universal polarimeter) method, (C3H7NH3)2MnCl4 was found to be optically active in its incommensurate phases, e.g., g33=1.1×10-5 in the γ phase at 83.0°C and g33=2.4×10-5 in the ε phase at -139.0°C. The temperature dependence of g33 was obtained. Commensurate domains were found to begin to grow below -139°C in the ε phase.

Incommensurate phase transitions and optical activity.

Recent experiments with the high-accuracy universal polarimeter method have revealed optical activity of the incommensurate phases of ${\mathit{A}}_{2}$${\mathit{BX}}_{4}$ crystals. The origin of this important phenomenon is explained. A pure imaginary perturbation that takes place in the Hermitian dynamical matrix induces two circularly helical lattice waves. One of them is condensed in the same form in the incommensurate phase. This is also the physical picture of the existence of the phason mode. The symmetry of the crystal becomes ${\mathit{D}}_{\mathrm{\ensuremath{\infty}}}$, which permits optical activity. The theory is consistent with the Lifshitz condition and with our experimental results.

Optical activity of incommensurate state of [N(CH3)4]2CuCl4

By applying the HAUP (high-accuracy universal polarimeter) method, [N(CH3)4]2CuCl4 was found to be optically active in its incommensurate phase, e.g., g23=3.9×10−5 at 24 °C. The temperature dependence of g23 was obtained. By making use of the fact that the commensurate phase of [N(CH3)4]2CuCl4 is ferroelastic and centrosymmetric, the temperature dependence of the soliton density in its incommensurate phase was deduced by this optical measurement. It is suggested that the HAUP method will become a new and direct method for measuring soliton densities of incommensurate states.

Evaluation of the systematic errors of polarimetric measurements: application to measurements of the gyration tensors of α-quartz by the HAUP

It was shown in the course of developing the high-accuracy universal polarimeter (HAUP) that any polarimetric optical analyses cannot be free from a systematic error γ originating in the parasitic ellipticities of the constituent Nicol prisms. A method by which one can remove γ in the HAUP method is presented. This has been successfully applied to measurements of the gyration tensors and birefringence of two enantiomorphic crystals of α-quartz. It was found that the order of magnitude of this error for a polarizer is about 10−4 and consequently γ lies between 10−4 and 10−3 in typical optical systems. Our results, g11 = 5.7 ± 0.52 × 10−5 and g33 = −13.6 ± 0.52 × 10−5 with a wavelength of 6328 Å for laevorotatory quartz at 300 K are in good agreement with some of the previous reports.