EP2149040A2 - Procédé et dispositif pour mesure un dichroïsme en temps réel - Google Patents

Procédé et dispositif pour mesure un dichroïsme en temps réel

Info

Publication number
EP2149040A2
EP2149040A2 EP08763869A EP08763869A EP2149040A2 EP 2149040 A2 EP2149040 A2 EP 2149040A2 EP 08763869 A EP08763869 A EP 08763869A EP 08763869 A EP08763869 A EP 08763869A EP 2149040 A2 EP2149040 A2 EP 2149040A2
Authority
EP
European Patent Office
Prior art keywords
circular dichroism
fact
measuring
sample
grating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP08763869A
Other languages
German (de)
English (en)
Inventor
Gabriella Cipparrone
Pasquale Pagliusi
Clementina Provenzano
Alfredo Mazzulla
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Universita della Calabria
Original Assignee
Universita della Calabria
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Universita della Calabria filed Critical Universita della Calabria
Publication of EP2149040A2 publication Critical patent/EP2149040A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/19—Dichroism
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G01N21/23—Bi-refringence

Definitions

  • the present invention concerns a method and a device for measuring circular dichroism using a diffraction grating on a material having an induced linear optical anisotropy.
  • the above-mentioned grating generates only the fields diffracted to the first order, whose amplitudes are proportional to the ones of the right and left circular components of the light beam impinging onto the grating.
  • the method and the device of the present invention demonstrate that, by using these characteristics of the grating, the circular dichroism of a medium can be easily determined by sending the light beam coming from the medium to be analysed (transmitted or reflected), onto the grating, and measuring the intensity of the beams diffracted by the grating.
  • the systems conventionally used to measure circular dichroism generally require an intense source of light with a wide spectrum, a monochromator, modulators of polarisation, and use phase sensitive detectors (lock-in amplifiers) tuned to the frequency and the phase of the modulator.
  • They are generally constituted by several optical elements placed before and after the sample to be analysed, and some of these elements are used to alternatively select the right and left circular polarisation of the wave striking the sample, while others are dispersive elements (prisms or gratings) necessary to select the various wavelengths, etc..
  • US2004156051 A1 describes a method and a device for measuring the birefringence starting from a circularly polarised light beam that strikes the sample and that uses the Stokes' parameters.
  • the presence of a polarizer to select the circular polarisation is necessary.
  • the principal aim of the invention is to create a method for measuring the circular dichroism of a sample, in which a beam of light passes through said sample, and said light beam successively passes through an optical element (PH) constituted by a film of material with a spatially modulated linear optical anisotropy.
  • the diffracted beams are detected and the signals of the diffracted beams are sent to a computer which, through a software, calculates the circular dichroism spectrum, performing the intensity ratio of the diffracted beams.
  • Another important objective is to create a device that permits the method of circular dichroism measurement described above to be realized.
  • optical element with spatially modulated linear optical anisotropy is a diffracting grating.
  • the sensors for revealing the beams are multi-channel light detectors.
  • the multi-channel detectors can be arrays of photodiodes.
  • CCDs Charged coupled devices
  • Said device allows structural information and detailed enantiomeric information about- various systems, such as, for example, proteins, carbohydrates, nucleic acids, pharmaceuticals, liquid crystals, etc. to be obtained.
  • the real time measurement of the circular dichroism permits studies of both dynamic processes and kinetics of chiral molecules.
  • a compact device allows making a portable version of the instrument.
  • the method is based on the use of a single element, other optical elements (prisms, mirrors, wave plates, etc.) are not required, implying a reduction of the light losses;
  • the dispersion properties of the grating allow measurements in real time to be taken, in fact the signal at every wavelength diffracted at different angles can be detected in parallel by a photodiodes array or a CCD;
  • linear polarisation, random linear or non-polarised light can be used to measure the circular dichroism
  • the method does not require complex and repetitive calibration procedures; 9) decrease of the production costs because it does not require optical and/or electro-optical elements as the standard systems do; 10)performances enhancement, real time measurements due to the absence of moving elements, extremely simplified calibration procedures of the system; 11)real time measurement implies the possibility to investigate dynamic processes (new market areas);
  • the device can be integrated into multifunctional apparatus and is able for
  • Fig.1 diffraction grating, schematic representation of the spatial modulation of the optical axis in the material
  • Fig.2 outline of the method in accordance with the present invention
  • FIG.3 schematic view of the device in accordance with the present invention.
  • the diffracting grating on whose properties the proposed method is based, is a film of a material with spatially modulated linear optical anisotropy (dichroism or linear birefringence).
  • the spatially modulated optical anisotropy in the present context indicates that:
  • the Jones' vector of a light beam with arbitrary polarisation can be written as follows: I11
  • the transmission matrix of the grating can be written in the following way: l2]
  • ⁇ is the wavelength of the incoming wave.
  • the transmitted wave (equation 2), zero order, has the same polarisation state of the incident wave, but its amplitude is reduced by the factor a.
  • the first order diffracted beam +1 (equation 3) is a wave having left circular polarisation but its amplitude is proportional to the one of the right component of the incident wave.
  • the diffracted beam of the -1 order has a right circular polarisation but its amplitude is proportional to the one of the left component of the incident wave (equation 4).
  • the diffraction occurs only onto the first orders +1 and/or -1.
  • the incoming beam is elliptically polarised, according to both the direction of rotation (right or left helicity) and the ellipticity, energy transfer between the two diffracted beams can be obtained, however the sum of the two beams intensities remains constant.
  • Circular dichroism is generally calculated by measuring the transmitted intensity when a beam with right or left circular polarisation strikes the sample by using the following expression:
  • I 0L and I 0R are the intensities of left and right polarised beams that alternatively strike a sample
  • I JL and I T R are the intensities of the left and right circularly polarised transmitted light, respectively.
  • the light beam which strikes the sample to be analysed, can have a linear polarisation or a random linear polarisation or a non-polarised state, when the sample is an isotropic system or a liquid or a solution, etc..
  • the method requires the use of non-polarised light or random linear polarisation when analysing samples that present linear birefringence (crystals, oriented polymers, liquid crystals, etc.).
  • the incoming beam can be considered as composed of two opposed circularly polarised waves (one right circular and one left circular) of equal amplitude.
  • the grating is placed immediately after the sample the wave (transmitted or reflected) coming from it and impinging onto the grating will be diffracted in the way described above.
  • Equation (7) demonstrates that circular dichroism can be easily calculated by the logarithm of the intensities ratio of the beams diffracted by the grating.
  • the described method does not necessarily require the use of linearly polarised light to be sent onto the sample, and it is, in fact, possible to use random linear polarised or non-polarised light source. Random linear polarised or non-polarised light is necessary for the analysis of oriented samples that present linear birefringence.
  • the incoming wave can always be written as being composed of two waves with opposite circular states of polarisation where, however, both the amplitudes of the components waves E x and Ey and the phase ⁇ randomly vary in time.
  • the wave can be written in the following way:
  • the only optical element necessary to the described method is a grating, which possesses spectral selectivity, intending that waves with different wavelengths incident onto the grating are diffracted at different angles.
  • a grating which possesses spectral selectivity, intending that waves with different wavelengths incident onto the grating are diffracted at different angles.
  • CCD Charged coupled device
  • the simultaneous acquisition of the diffracted beams intensities at different wavelengths is possible and, therefore, the real-time circular dichroism spectrum, throughout the spectral range of the used light source, can be obtained.
  • the proposed method does not require any particular procedure for the grating characterisation, such as for example the diffraction efficiency measurement and its determination at each wavelength, since it is simply based on the ratio of the diffracted beams intensities. Films of materials that possess only one or both the indicated anisotropies (linear dichroism or birefringence) can be used to create the grating.
  • FIG. 3 schematically illustrates a device according to the invention.
  • a beam of light L passes through the sample S and the diffracting grating PH, which has a spatially modulated linear optical anisotropy.
  • the beams diffracted to the first order 1 +1 and Li are collected by the multi-channel light sensors CCd 1 and CCd2 that convey the relative signals to .
  • the computer PC which, through an appropriate software calculates the circular dichroism spectrum, carrying out the logarithm of the diffracted beams intensities ratio.
  • the present invention permits numerous advantages and overcome difficulties that could not be defeated with the systems presently on sale.

Landscapes

  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Arrangements For Transmission Of Measured Signals (AREA)

Abstract

La présente invention concerne un procédé et un dispositif pour mesurer le dichroïsme circulaire d'un échantillon dans lequel un faisceau de lumière passe par l'échantillon, caractérisé en ce que le faisceau passe successivement par un réseau et en ce que les faisceaux différentiés sont recueillis et que les signaux des faisceaux diffractés sont collectés. Les signaux des faisceaux diffractés sont envoyés à un ordinateur qui, via un logiciel, calcule la valeur du dichroïsme circulaire, réalisant le logarithme du rapport des intensités de faisceaux diffractés.
EP08763869A 2007-05-18 2008-05-19 Procédé et dispositif pour mesure un dichroïsme en temps réel Withdrawn EP2149040A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITCS20070024 ITCS20070024A1 (it) 2007-05-18 2007-05-18 Metodo e dispositivo per la misura in tempo reale di dicroismo circolare
PCT/IT2008/000334 WO2008142723A2 (fr) 2007-05-18 2008-05-19 Procédé et dispositif pour mesure un dichroïsme en temps réel

Publications (1)

Publication Number Publication Date
EP2149040A2 true EP2149040A2 (fr) 2010-02-03

Family

ID=39884636

Family Applications (1)

Application Number Title Priority Date Filing Date
EP08763869A Withdrawn EP2149040A2 (fr) 2007-05-18 2008-05-19 Procédé et dispositif pour mesure un dichroïsme en temps réel

Country Status (3)

Country Link
EP (1) EP2149040A2 (fr)
IT (1) ITCS20070024A1 (fr)
WO (1) WO2008142723A2 (fr)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1403559B1 (it) * 2011-01-27 2013-10-31 Università Della Calabria Metodo per la misura di proprietà chiro-ottiche in tempo reale basato su un reticolo di polarizzazione
US10161797B2 (en) * 2015-07-05 2018-12-25 Purdue Research Foundation Sub-millimeter real-time circular dichroism spectrometer with metasurfaces
JP7045663B2 (ja) * 2017-12-04 2022-04-01 学校法人同志社 複屈折測定装置および複屈折測定方法
EP3722787B1 (fr) * 2017-12-07 2024-03-27 Yokogawa Electric Corporation Analyseur spectroscopique
US12007276B2 (en) 2018-03-22 2024-06-11 Purdue Research Foundation Sensor for hyperspectral imaging based on a metasurface-integrated light detector array
JP7700985B2 (ja) * 2021-06-11 2025-07-01 国立大学法人徳島大学 円二色性分光測定装置およびこれに用いる偏光素子
CN119546988A (zh) * 2022-08-18 2025-02-28 富士胶片株式会社 光学元件

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2008142723A3 *

Also Published As

Publication number Publication date
WO2008142723A2 (fr) 2008-11-27
ITCS20070024A1 (it) 2008-11-19
WO2008142723A3 (fr) 2009-01-08

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