The Optical Rotatory Dispersion and Linear Dichroism Option of the JASCO J-500 A-Type CD Spectropolarimeter

1989 ◽  
Vol 43 (8) ◽  
pp. 1471-1475 ◽  
Author(s):  
Yohji Shindo ◽  
Hiroshi Hayakawa ◽  
Masahiro Sudani
Keyword(s):  
Optical Axis ◽  
High Sensitivity ◽  
Linear Dichroism ◽  
Null Point ◽  
Optical Rotatory Dispersion ◽  
Polarization Modulation ◽  
Know How ◽  
Harmonic Rejection ◽  
Lock In ◽  
Point Detection

We have made an ORD option for our JASCO J-500 A-type CD spectrometer based on the know-how obtained from the studies of our new polarization-modulation spectrometer. The Mueller matrix approach is used to analyze and evaluate important factors determining the performance of our ORD option. These are (1) the harmonic rejection and “in band” overload capability of the lock-in amplifier, (2) the position of the analyzer's optical axis, (3) the residual static birefringence of the PEM. The capability of our ORD option is equal to that of commercially available ORD spectropolarimeters, in the range from 200 to 700 nm. Furthermore, our option has much faster speed for ORD measurements than does the ORD spectropolarimeter of the null-point detection type. Our ORD option can also be used to measure linear dichroism in high sensitivity.

Measurement of quadratic electrogyration effect in KDP crystals for light propagating along the optical axis

2019 ◽  
Vol 52 (1) ◽  
pp. 158-167 ◽  
Author(s):  
Marek Izdebski
Keyword(s):  
Optical Axis ◽  
Potassium Dihydrogen Phosphate ◽  
High Sensitivity ◽  
Measurement Procedure ◽  
Measuring System ◽  
Dihydrogen Phosphate ◽  
Kdp Crystal ◽  
Potassium Dihydrogen ◽  
Electro Optic ◽  
Lock In

In this paper, a method of measuring the β31 coefficient of the quadratic electrogyration effect in potassium dihydrogen phosphate (KDP)-type crystals is proposed. It is shown that this very weak effect can be decoupled from other stronger effects occurring simultaneously in the real measuring system, even when small inaccuracies in crystal cutting and alignment are taken into account. Theoretical and numerical analyses are illustrated by experimental data obtained for the KDP crystal. High sensitivity, which is required for successful measurements at room and higher temperatures, has been achieved by using the polarimetric method for a light beam propagating along the optical axis of the crystal in combination with the lock-in technique and a new measurement procedure that compensates for the contribution of other effects such as electro-optic effects, natural birefringence and dichroism. It was found that the β31 coefficient measured at a wavelength of 632.8 nm decreases linearly from 2.53 × 10−21 m2 V−2 at a temperature of 298 K to 2.08 × 10−21 m2 V−2 at 343 K.

Near Edge X-Ray Absorption Fine Structure (NEXAFS) Microscopy: Chemical Analysis at Sub Visible Spatial Resolution

1997 ◽  
Vol 3 (S2) ◽  
pp. 851-852
Author(s):  
H. Ade
Keyword(s):  
Fine Structure ◽  
Compositional Analysis ◽  
High Sensitivity ◽  
Linear Dichroism ◽  
X Rays ◽  
X Ray ◽  
Absorption Fine ◽  
Nexafs Spectroscopy ◽  
Wide Range ◽  
X Ray Absorption

Infrared, Raman, and fluorescence/luminescence microspectroscopy/microscopy in many instances seek to provide high sensitivity compositional and functional information that goes beyond mere elemental composition. This goal is shared by NEXAFS microscopy, in which Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is employed to provide chemical sensitivity and can be relatively easily adopted in a scanning transmission x-ray microscope (STXM). In addition to compositional information, NEXAFS microscopy can exploit the dependence of x-ray absorption resonances on the bond orientation relative to the linearly polarized x rays (linear dichroism microscopy). For compositional analysis, NEXAFS microscopy is analogous to Electron Energy Loss Spectroscopy (EELS) in an electron microscope. However, when utilizing near edge spectral features, NEXAFS microscopy requires a considerable lower dose than EELS microscopy which makes it very suitable to studying radiation sensitive materials such as polymers. NEXAFS has shown to have excellent sensitivity to a wide range of moieties in polymers, including sensitivity to substitution isomerism.

scholarly journals DETERMINATION OF THE POLARIZATION OPTICAL PROPERTIES OF THE AMYLOID-CONGO RED COMPLEX BY PHASE MODULATION MICROSPECTROPHOTOMETRY

1974 ◽  
Vol 22 (12) ◽  
pp. 1105-1112 ◽  
Author(s):  
DOUGLASS L. TAYLOR ◽  
ROBERT D. ALLEN ◽  
EARL P. BENDITT
Keyword(s):  
Circular Dichroism ◽  
Congo Red ◽  
Phase Modulation ◽  
Optical Rotation ◽  
Polarized Light ◽  
Visible Spectrum ◽  
Linear Dichroism ◽  
Cotton Effect ◽  
Optical Rotatory Dispersion ◽  
Circular Dichroïsm

The polarization properties responsible for the classical "green birefringence" of the amyloid-Congo red complex have been determined by a new optical method, phase modulation microspectrophotometry. This method now makes possible the measurement of one optical property at a time (birefringence, optical rotation, linear dichroism and circular dichroism throughout the visible spectrum) in complex specimens in which visible contrast in polarized light is the result of a mixture of polarization effects. The green birefringence is explained by a combination of optical effects, the strongest of which are dispersion of birefringence and linear dichroism superimposed on the smaller effects of circular dichroism and optical rotatory dispersion. The interaction of the planar dye molecules with the amyloid protein induces an extrinsic Cotton effect.

The Application of Signal Processing Techniques in Improving Spectrometer Detection Limit

2011 ◽  
Vol 148-149 ◽  
pp. 1045-1050
Author(s):  
Zhi Ying Wu ◽  
Yi Zhang ◽  
Zuo Yuan Shen
Keyword(s):  
Signal Processing ◽  
Detection Limit ◽  
High Sensitivity ◽  
Processing Technique ◽  
Laser Source ◽  
Sampled Data ◽  
High Concentration ◽  
Signal Processing Technique ◽  
Processing Techniques ◽  
Lock In

Improving spectrometer detection limit using statistical principle and signal-processing technique are described simply in this work. In the detection of gas photoacoustic(PA) signal, accurate partitions of the sampled data affect on the detection limit to some extent although Lock-in amplification technique with high SNR and microphone sensor with high sensitivity have been used. A model and the resulting algorithm are proposed from PA-signal samples. The techniques are validated at ppb level on PA spectrometer for NH3 breath detection in high concentration of CO2 and H2O based on tunable erbium-doped fiber laser (TEDFL) or for multicomponent trace gas detection based on waveguide CO2 laser or on other laser source.

Optical Anisotropy Studies of Sapphire by Raman Scattering and Spectroscopic Transmission Ellipsometry

1998 ◽  
Vol 512 ◽  
Author(s):  
H. Yao ◽  
C. H. Yan ◽  
S. P. Denbaars ◽  
J. M. Zavada
Keyword(s):  
Raman Scattering ◽  
Optical Anisotropy ◽  
Optical Axis ◽  
High Sensitivity ◽  
Incident Laser ◽  
Axis Orientation ◽  
Raman Analysis ◽  
Sapphire Substrates ◽  
Peak Intensity ◽  
Polarized Raman

ABSTRACTOptical anisotropy of sapphire have been studied by both polarized Raman scattering and transmission variable angle spectroscopic ellipsometry (TVASE). The polarized Raman effect was measured on both c-plane (0001) and a-plane (2110) sapphire substrates. Two TO phonons (379 and 431 cm−l) and four LO phonons (418, 450, 577, and 750 cm−1) were observed when the optical axis <c> is perpendicular to the polarization of the incident laser beam (for both c-plane and a-plane). While only two TO phonons (379 and 431cm−1) and two LO phonons (418 and 645 cm−1) can be seen when the optical axis is parallel to the polarization for an a-plane sapphire. The optical axis of the a-plane sapphire can then be quickly determined by either maximizing or minimizing the 645 LO peak intensity with about ±10° error. TVASE measurements were carried out in the energy range of 0.75eV to 5.8eV at room temperature. Sizable off-diagonal Jones matrix elements Apst, and Aspt can be detected even with the optical axis 1° off the X-axis. This indicates that TVASE has a high sensitivity to optical anisotropy. By minimizing these off-diagonal elements and combining the Raman analysis, the optical axis orientation of an a-plane or m-plane (0110) sapphire can therefore be fully determined with an error of less than 1°.

High sensitivity photothermal surface spectroscopy with polarization modulation

1984 ◽  
Vol 145 (2-3) ◽  
pp. L504-L508 ◽  
Author(s):  
H. Coufal ◽  
F. Träger ◽  
T.J. Chuang ◽  
A.C. Tam
Keyword(s):  
High Sensitivity ◽  
Polarization Modulation ◽  
Surface Spectroscopy

Theory of High Frequency Differential Interferometry: Application to the Measurement of Infrared Circular and Linear Dichroism via Fourier Transform Spectroscopy

1979 ◽  
Vol 33 (2) ◽  
pp. 130-135 ◽  
Author(s):  
Laurence A. Nafie ◽  
Max Diem
Keyword(s):  
Fourier Transform ◽  
High Frequency ◽  
Linear Dichroism ◽  
Periodic Variation ◽  
Polarization Modulation ◽  
Differential Absorption ◽  
Differential Interferometry ◽  
Infrared Spectrometer ◽  
Alternate States ◽  
General Method

A general method for the direct measurement of differential absorption intensities using a Fourier transform infrared spectrometer is described. The differential intensities must be higher in frequency than the interferogram frequencies and may arise from a periodic variation of the absorption strength of the sample, or by dichroic response of the sample to alternate states of polarization of the infrared beam. Specific expressions are presented for the measurement of circular and linear dichroism. These expressions represent an extension of the Grosjean-Legrand polarization modulation technique to Fourier transform interferometry.

Sign in / Sign up

Export Citation Format

Share Document