JP2019152523A - Optical rotation measuring device - Google Patents

Abstract

To provide an optical rotation measuring device capable of reducing power consumption and miniaturization by constituting the optical rotation measuring device without using a Faraday cell.SOLUTION: An optical measuring device according to the present invention has at least a light source unit, a magnetic optical modulation element, a magnetic field applying mechanism, and a photodetector which emit a linearly polarized light. A light from a light source unit is irradiated to a multilayer body under conditions in which a magneto-optical signal is enhanced by multiple reflections generated by the laminated body of the magneto-optic modulation element. In this case, the change of the reflected light from a stack is detected as a magneto-optical signal which is the magnetization of the laminated body by the magnetic field applying mechanism by means of controlling the rotation angle of the polarization plane with the passage of the measurement object.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical rotation measuring device for measuring the optical rotation of an optically active substance.

  2. Description of the Related Art There are known optical rotation measuring devices for measuring the specificity or concentration of optically active substances having optical activity, such as sugars, amino acids and vitamins. Optical rotatory power is a property that the plane of polarization rotates when linearly polarized light passes through an optically active substance such as glucose. The rotation angle of the plane of polarization at this time is called optical rotation. The optical rotation per unit substance is a value specific to the substance. By measuring the optical rotation of the solution, the substance in the solution can be identified or its concentration can be measured.

  The optical rotation measurement device that measures the optical rotation enters the measurement light that is linearly polarized light using a polarizer, then enters the measurement light that has passed through the measurement object, and passes through the analyzer. It is a device that measures the optical rotation of the measurement substance by measuring the amount of light. Specifically, by rotating the analyzer while detecting the amount of light that has passed through the analyzer, and determining the rotation angle of the analyzer at which the amount of light that passes through the analyzer becomes zero, the object to be measured has a plane of polarization of linearly polarized light. The rotated angle, that is, the optical rotation of the measurement object can be obtained.

  Conventionally, in order to measure the optical rotation with high accuracy, a polarization plane vibration method is generally used in which the polarization plane of measurement light is periodically changed at a constant angle to modulate the amount of light passing through the analyzer. As a typical optical rotation measuring device, a device that vibrates the angle of a polarization plane using a Faraday cell arranged in front of an analyzer is known (for example, see Patent Documents 1 and 2).

  The Faraday cell has a configuration in which a Faraday glass is incorporated in a Faraday coil, a magnetic field is generated by supplying current to the Faraday coil, and the angle of the polarization plane of linearly polarized light passing through the Faraday glass is The Faraday effect, which is one of magneto-optical effects, is varied according to the strength of the applied magnetic field. The Faraday coil supplied with the alternating current generates an oscillating magnetic field therein, and the polarization plane of the linearly polarized light passing through the Faraday glass vibrates in accordance with the oscillating magnetic field. Since the amount of light that passes through the analyzer varies depending on the angle of the polarization plane, the detection signal that detects the measurement light becomes an AC signal, and even when there are many noise components in the measurement light, the optical rotation must be measured with high accuracy. Can do.

The rotation angle θ _f of the polarization plane due to the Faraday effect is proportional to the length l of the Faraday glass through which light passes and the strength H of the applied magnetic field,
θ _f = V × l × H (Formula 1)
V is called the Verde constant. For example, when a heavy flint glass (V = 1.3 × 10 ⁻¹ min / A) having a relatively large Verde constant is used, in order to obtain an optical rotation angle of several degrees, from Equation 1, H to 10 ⁵ A / m (where l = 1 cm), and depending on the Faraday coil diameter and the number of windings, a current of several A is required.

  On the other hand, as another method for measuring the angle of the polarization plane of light that has passed through a measurement object, an optical rotation measurement device using a differential detection method generally known in a magneto-optical recording system is disclosed in Patent Document 3. It is disclosed. The light that has passed through the measuring object is divided into two lights by a polarization beam splitter, and each light is measured by two photodetectors so that the polarization angle can be read without using an analyzer. Yes. In this prior art document, the optical rotation is measured without using a Faraday cell, but in order to measure the optical rotation with high accuracy, it is necessary to modulate the measurement light by some method. This is the same as a conventional optical rotation measuring apparatus using an analyzer.

Japanese Patent Laid-Open No. 9-138231 JP 2000-81386 A JP 2012-83311 A

  In the optical rotation measuring device employing the Faraday cell, as described above, in order to change the angle of the polarization plane, it is necessary to supply a current of several A to the Faraday cell, and there is a problem that power consumption increases. Furthermore, since the size of the Faraday cell is as large as several centimeters, improvement is also required in terms of downsizing the apparatus.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical rotation measuring device that can be reduced in power consumption and reduced in size by configuring the optical rotation measuring device without using a Faraday cell in order to solve the above problems. It is in.

  In order to solve the above problems, an optical rotation measuring device according to the present invention includes at least a light source unit that emits linearly polarized light, a magneto-optical modulation element that modulates the intensity or polarization angle of measurement light by the magnetic Kerr effect, and the magnetic A magnetic field application mechanism that applies an alternating magnetic field to the optical modulation element; and a photodetector that detects light reflected from the magneto-optical modulation element. The magnetic Kerr effect is one of magneto-optical effects, and is a phenomenon in which when a magnetic material is irradiated with linearly polarized light, the reflection intensity of reflected light or the angle of the polarization plane changes according to the magnetization direction of the magnetic material. . Here, the optical rotation measuring device according to the present invention includes at least a laminated body in which a metal magnetic layer, a dielectric optical interference layer, and a metal reflective layer are laminated on a substrate as the magneto-optic modulation element. can do. According to the optical rotation measuring device of the present invention, when the linearly polarized light emitted from the light source unit is incident on the laminated body arranged after passing through the measurement object, the multiple reflection generated in the laminated body The light from the light source unit is irradiated under the condition that the magneto-optical signal that is reflected light is enhanced. At this time, the optical rotation measuring apparatus according to the present invention reflects the reflection angle from the laminate by controlling the rotation angle of the polarization plane accompanying the passage of the measurement object and the magnetization direction of the metal magnetic layer by the magnetic field application mechanism. The optical rotation of the object to be measured is measured by detecting the magneto-optical signal, which is a change in light, with the photodetector. The magneto-optic modulation element is configured by a laminated body in which thin films are laminated, and can provide a smaller optical rotation measuring device than a conventional optical rotation measuring device using a Faraday cell.

  Furthermore, in the optical rotation measuring apparatus according to the present invention, the metal magnetic layer constituting the magneto-optic modulation element is preferably a soft magnetic thin film having a small saturation magnetic field. According to this configuration, it is possible to reduce the current supplied to the magnetic field application mechanism in order to control the magnetization of the metal magnetic layer, and to provide a low power consumption optical rotation measuring device.

  In addition, the optical rotation measuring apparatus according to the present invention is configured such that the magnetic field application mechanism for applying an alternating magnetic field to the magneto-optic modulation element is formed on the laminate functioning as the magneto-optic modulation element via an insulator layer. It is preferable that the metal current layer is formed. According to such a configuration, by using a leakage magnetic field generated by supplying an alternating current to the metal current layer, it becomes possible to control the magnetization of the metal magnetic layer constituting the laminate, and an electromagnet or the like. Since there is no need to provide it separately, the apparatus configuration is simplified, and it is possible to provide a small and low-cost optical rotation measuring apparatus.

  The metal magnetic layer constituting the magneto-optic modulation element is preferably an FeCo alloy thin film or a CoPt alloy thin film. According to this configuration, the magneto-optical signal generated by the magneto-optical modulation element can be increased, and the optical rotation can be measured with high accuracy.

  Furthermore, in the optical rotation measuring device according to the present invention, as the light source unit that emits linearly polarized light, the polarizer is rotated in order to adjust the angle of the polarization plane of the linearly polarized light that irradiates the magneto-optic modulation element. It is preferable to provide a rotation means. According to such a configuration, the rotation angle of the polarizer is adjusted so that the magneto-optical signal reflected from the magneto-optic modulation element has a predetermined value, so that the rotation angle of the measurement target can be determined from the rotation angle of the polarizer. Therefore, it is possible to provide an optical rotation measuring device capable of efficiently measuring the optical rotation.

  An optical rotation measuring device according to the present invention includes at least a light source unit, a magneto-optical modulation element, a magnetic field application mechanism, and a photodetector, and further, the light emitted from the light source unit is disposed after passing through a measurement target. When the light is incident on the magneto-optic modulation element composed of a thin film laminate, linearly polarized light is irradiated from the light source unit under the condition that the magneto-optic signal is enhanced by multiple reflections generated by the laminate, and passes through the measurement target. The rotation angle of the polarization plane of the linearly polarized light is measured by measuring the magnetization of the metal magnetic layer constituting the laminate by the magnetic field application mechanism, and measuring it as the magneto-optical signal by the photodetector. Measure the optical rotation of the object. Therefore, in the optical rotation measuring device according to the present invention, since the magneto-optic modulation element is composed of a thin film laminate, the device can be downsized as compared with a conventional optical rotation measuring device using a Faraday cell. It becomes possible. Further, by using a soft magnetic material having a small saturation magnetic field as the metal magnetic layer, power consumption can be reduced. Furthermore, as a method for controlling the magnetization of the metal magnetic layer constituting the laminate, a leakage magnetic field generated by applying an alternating current to the metal current layer formed on the laminate via an insulator layer is used. Further, the present invention has excellent effects such as further miniaturization of the optical rotation measuring device and reduction of power consumption.

It is a lineblock diagram showing typically the optical rotation measuring device of a 1st embodiment. It is a block diagram which shows typically the other optical rotation measuring apparatus of 1st Embodiment. It is explanatory drawing which shows the measurement principle of the magneto-optical characteristic and optical rotation of the magneto-optical modulation element which comprises the optical rotation measuring apparatus shown in FIG. 1, FIG. 1 is a cross-sectional view schematically showing a magneto-optic modulation element that constitutes an optical rotation measuring device of Example 1. FIG. FIG. 5 is a characteristic diagram showing measurement of optical rotation by the magneto-optical modulation element shown in FIG. 4. It is a block diagram which shows typically the optical rotation measuring apparatus of 2nd Embodiment. It is explanatory drawing which shows the magneto-optical characteristic of the magneto-optical modulation element which comprises the optical rotation measuring apparatus shown in FIG. It is explanatory drawing which shows the measurement principle of the optical rotation of the magneto-optical modulation element which comprises the optical rotation measuring apparatus shown in FIG. It is a block diagram which shows typically the magneto-optical modulation element of 3rd Embodiment. It is explanatory drawing which shows the magneto-optical characteristic of the magneto-optical modulation element which comprises the optical rotation measuring apparatus shown in FIG. FIG. 5 is a cross-sectional view schematically showing a magneto-optic modulation element that constitutes an optical rotation measuring device of Example 2. FIG. 12 is a characteristic diagram showing measurement of optical rotation by the magneto-optic modulation element shown in FIG. 11.

  In the optical rotation measuring device of the present invention, when linearly polarized light is irradiated to a magneto-optic modulation element composed of a laminate including at least a metal magnetic layer, a dielectric optical interference layer, and a metal reflection layer, By using the enhancement phenomenon of the magneto-optical signal due to the multiple reflection that occurs, the change in the angle of the polarization plane of the measurement light that occurs as the measurement object passes, that is, the optical rotation of the measurement object is measured. Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[First Embodiment]
1 and 2 are configuration diagrams schematically showing an optical rotation measuring apparatus 10 according to the first embodiment of the present invention. The dotted arrow in the figure is the optical path, and the optical rotation measuring device 10 is based on a transverse Kerr effect optical system, which is one of the magnetic Kerr effects, and as shown in FIGS. A direction perpendicular to the projection of incident light and reflected light onto the reflection surface (laminate 15) in a state where light is applied to the surface of the functional laminate 15 from an oblique direction, that is, FIGS. 1 and 2 The angle of the polarization plane of the light incident on the laminate 15 is measured by applying an alternating magnetic field in the direction perpendicular to the drawing surface and measuring a magneto-optical signal that is a change in the intensity of the reflected light from the laminate 15. taking measurement. The light source unit U includes a light source 11, a hollow motor 12 as a rotating means, and a polarizer 13. In the present embodiment, the optical rotation measuring device 10 uses a magneto-optic effect to convert a polarizer 13 that makes light emitted from the light source 11 linearly polarized light, a sample cell 14 into which the measurement object is placed, and measurement light that has passed through the measurement object. A layered body 15 for modulation, and a photodetector 17 that detects the light that has passed through the bandpass filter after the light reflected from the layered body is incident on the bandpass filter 16.

  As the light source 11, a monochromatic light source that emits light of a single wavelength, such as a semiconductor laser or a gas laser, is used. Further, as the polarizer 13 for converting the light emitted from the light source 11 into linearly polarized light, It is preferable to improve the linear polarization characteristic using a Glan-Thompson prism or the like. In addition, when the light source 11 is comprised by the semiconductor laser etc. which radiate | emit linearly polarized light, since an optical rotation measuring apparatus can be comprised without using the polarizer 13, the simplification and cost reduction of an apparatus are further simplified. The effect of making it possible. Further, the polarizer 13 is fixed at a position that covers the opening of the hollow motor 12, which is an electric motor formed in a hollow cylindrical shape. A motor driver 21 is connected to the hollow motor 12, and by rotating the hollow motor by a drive current supplied from the motor driver, the polarizer 13 is rotated, so that the polarization plane of linearly polarized light has a predetermined polarization plane. The linearly polarized light is incident on the sample cell 14 by adjusting the angle.

  The sample cell 14 is a transparent container into which a liquid measurement object is injected, and is arranged at a position where an optical path passes through the measurement object. The light that has passed through the sample cell 14 enters the laminate 15 that functions as a magneto-optic modulation element, and is emitted as a magneto-optic signal due to the magneto-optic effect generated in the laminate 15. The light emitted from the laminated body 15 passes through the bandpass filter 16 and enters the photodetector 17. The bandpass filter 16 is an optical filter that allows light having a wavelength used for measuring the optical rotation to pass and blocks light having other wavelengths.

  The multilayer body 15 is constituted by a structure in which a metal magnetic layer 32, a dielectric optical interference layer 31, and a metal reflective layer 30 are laminated in this order on a substrate, and magneto-optics are generated by multiple reflections generated inside the multilayer body 15. Linearly polarized light is irradiated under conditions that enhance the effect. Therefore, the dielectric optical interference layer 31 needs to be set to a thickness at which the light irradiated on the multilayer body 15 causes multiple reflection inside the multilayer body 15. Specifically, the dielectric optical interference layer 31 is required. It is preferable that the value obtained by multiplying the thickness of each of the metal reflection layer 30 and the refractive index is greater than about 1/4 of the wavelength of the light to be irradiated. Furthermore, the metal reflection layer 30 needs to have a thickness that allows the light irradiated on the multilayer body 15 to enter the multilayer body 15. Specifically, the thickness is preferably 30 nm or less. In addition, the metal magnetic layer 32 needs to have a thickness sufficient to reflect light that has entered the laminated body 15, and specifically has a thickness of 30 nm or more. In addition, the order which laminates | stacks each layer which comprises the laminated body 15 is not limited above. In the case where the thickness of each layer is adjusted so that the magneto-optical signal is enhanced by the multiple reflection occurring inside the multilayer body 15, for example, the metal reflection layer 30, the dielectric optical interference layer 31, and the metal magnetism are formed on the substrate. It is also possible to laminate the layer 32 in this order.

  A current source 19 is connected to the magnetic field application mechanism 18 shown in FIG. 1 or the metal current layer 34 shown in FIG. 2, and a leakage magnetic field generated by supplying an alternating current from the current source is used. Thus, the magnetization of the metal magnetic layer 32 is controlled in a direction perpendicular to the incident light on the laminate 15 and the projection onto the reflected light, that is, in the near direction or the depth direction with respect to the drawing surface of FIGS. Is for. The magnetic field application mechanism 18 applies a magnetic field in the normal direction of incident light and reflected light on the laminate 15. In particular, as shown in FIG. 2, when the metal current layer 34 is formed in the vicinity of the laminate 15 as a magnetic field application mechanism, it is not necessary to provide an electromagnet or the like separately. There exists an effect that a low-cost optical rotation measuring device can be provided. In this case, in order to efficiently supply current to the metal current layer 34, it is desirable to form an insulator layer 33 between the metal current layer 34 and the metal magnetic layer 32. The thickness needs to be sufficient to supply a current sufficient to control the magnetization of the metal magnetic layer 32. Specifically, the thickness is preferably 30 nm or more. The magnetic field application mechanism 18 in FIG. 2 includes an insulator layer 33 and a metal current layer 34.

Examples of the material used for the metal magnetic layer 32 include general magnetic materials made of metals such as Fe, Co, and Ni, alloys, and the like. In particular, the material is mainly composed of Fe having a large magneto-optical effect. It is preferable. In this case, it is possible to increase the magneto-optical signal associated with the change in the angle of the polarization plane of the measurement light, and it is possible to achieve an effect of enabling highly accurate optical rotation measurement. Furthermore, from the viewpoint of suppressing power consumption, the material used for the magnetic metal layer 32 is preferably a soft magnetic material having a small saturation magnetic field. As an example of the magnetic metal layer 32 satisfying such conditions, an FeCo alloy (an alloy thin film of iron and cobalt), an FeSi alloy, or the like can be given. In general, the saturation magnetic field of these magnetic materials is about 10 ³ A / m, which is about 1/100 of the Faraday cell driving magnetic field (H to 10 ⁵ A / m) calculated using Equation 1. Therefore, in the optical rotation measuring device of the present invention using the soft magnetic material having a small saturation magnetic field as the magnetic metal layer 32, the current consumption is increased to about 1/100 compared to the conventional optical rotation measuring device using the Faraday cell. There is an effect that it can be reduced.

Examples of the material used for the dielectric optical interference layer 31 include general transparent oxides such as SiO ₂ , ZnO, TiO ₂ , AlN, and MgF ₂ , transparent nitrides, and transparent fluorides. It is preferable to have a high transmittance with respect to the wavelength of light. Furthermore, as a material used for the metal reflection layer 30, a general metal material made of a metal such as Ag, Al, Au, or Cu, an alloy, or the like can be given, which is higher than the wavelength of light emitted from the light source 11. It preferably has a reflectance. When these materials are used, the reduction in the amount of light generated by the multiple reflection inside the laminate 15 can be reduced, and the effect of enabling highly accurate optical rotation measurement is obtained.

Next, the principle of optical rotation measurement by the optical rotation measurement device 10 of this embodiment will be described with reference to FIG. Here, when the linearly polarized light whose polarization plane angle is θ ₁ is incident on the laminated body 15 constituting the magneto-optic modulation element, the intensity change of the reflected light is caused by the multiple reflection generated inside the laminated body 15. That is, a case where the magneto-optical signal is the largest is considered.

In the laminated body 15 having the above-described configuration, a magnetic field (+ H ₁ or −H ₁ ) having a predetermined intensity capable of setting the magnetization of the metal magnetic layer 32 in a single direction is applied to the magnetic field applying mechanism 18 shown in FIG. When linearly polarized light is applied in the state of being applied by the leakage magnetic field from the metal current layer 34 shown in FIG. 2, large magneto-optics are caused by multiple reflections occurring inside the laminate 13 as shown in FIG. As a result, the irradiated light is emitted with a large intensity change (+ ΔR ₁ or −ΔR ₁ ). The direction of the magnetic field applied to the metal magnetic layer 32 is a direction orthogonal to the projection of incident light and reflected light onto the reflecting surface, and such a configuration is generally called a lateral Kerr effect. Next, as shown in FIG. 3B, the angle of the polarization plane of the linearly polarized light incident on the laminate 15 is changed from θ ₁ to θ ₂ in a state where a magnetic field (+ H ₁ or −H ₁ ) is applied. In this case, since the interference condition of the light in the stacked body 15 changes, the influence of multiple reflection becomes small, and as a result, the magnitude of the intensity change of the emitted light (| ΔR ₂ |) is the polarization plane of the incident light Is smaller than the initial state in which the angle is θ ₁ (| ΔR ₁ |> | ΔR ₂ |). R ₁ and R ₂ each represent the average intensity of the reflected light. Since the intensity change of the light reflected from the laminated body 15 changes according to the direction of magnetization of the metal magnetic layer 32 constituting the laminated body 15, the magneto-optical curve is shown in FIG. c) and as shown in FIG.

Therefore, by applying a magnetic field (± H ₁ ) periodically changing at a predetermined intensity by the leakage magnetic field generated from the magnetic field applying mechanism 18 shown in FIG. 1 or the metal current layer 34 shown in FIG. The polarization of the measurement light generated by passing through the measurement object by measuring the angle of the polarization plane of the incident light by the photodetector 17 as a magneto-optical signal that is a change in the intensity of the light reflected from the laminate 15. It becomes possible to measure the rotation angle of the surface, that is, the optical rotation. In particular, deriving the relationship between the angle of the polarization plane of incident light and the magneto-optical signal in advance has the effect of making it possible to easily measure the optical rotation of the measurement object in a short time.

  Specifically, the rotation plane of the polarizer 13 is rotated by rotating the hollow motor 12 in a state where the measurement object is not injected into the sample cell 14, so that the polarization plane of the light incident on the stacked body 15 is changed. A magneto-optical signal, which is a change in intensity of light reflected from the laminate 15, is measured by the photodetector 17 by changing the angle. As described with reference to FIG. 3, the magneto-optical signal reflected from the laminate 15 changes depending on the angle of the polarization plane of the incident light, and the relational expression between the angle of the polarization plane and the magneto-optical signal is determined in advance. Derived and stored in the computer 20. Thereafter, the hollow motor 12 is rotated to rotate the polarizer 13 so that the magneto-optical signal from the laminate 15 is maximized, and this is set to the initial state. Next, the measurement object is injected into the sample cell 14, the magneto-optical signal from the laminate 15 is measured, and the measurement object passes through the relational expression between the previously derived magneto-optical signal and the angle of the polarization plane. Then, the rotation angle of the polarization plane of the measurement light generated by this, that is, the optical rotation is derived.

  In such a measurement method, it is not necessary to rotate the polarizer 13 to change the angle of the polarization plane of the measurement light when actually measuring the optical rotation of the measurement object. It is possible to measure the optical rotation at.

  FIG. 4 is a cross-sectional view schematically showing the magneto-optical modulation element 40 constituting the optical rotation measuring device according to the example of the present embodiment.

  In the magneto-optic modulation element 40 of this embodiment, a base layer 45 made of a Pd thin film having a thickness of 10 nm is formed on a glass substrate 46, and a laminate 41 for actually measuring the optical rotation is formed thereon. Yes. The laminated body 41 includes a FeCo alloy thin film with a thickness of 100 nm as the metal magnetic layer 44, a ZnO thin film with a thickness of 116 nm as the dielectric optical interference layer 43, and an Au thin film with a thickness of 11 nm as the metal reflective layer 42. It is comprised by the structure laminated | stacked in order.

  FIG. 5A and FIG. 5B show the results of actually measuring the angle change of the polarization plane of incident light, that is, the optical rotation using this magneto-optic modulation element 40. In this embodiment, a semiconductor laser having a wavelength of 658 nm is used as the light source, and light that is linearly polarized by transmitting the polarizer is inclined at an angle of 45 degrees with respect to the surface of the magneto-optic modulation element 40. Irradiating and applying a periodically changing magnetic field from -40 Oe (in the depth direction with respect to the drawing surface in FIG. 4) to +40 Oe (in the front direction with respect to the drawing surface in FIG. 4). The intensity change of the reflected light from the magneto-optic modulation element 40 was measured. The direction of the magnetic field applied to the magneto-optic modulation element 40 was set to be orthogonal to the projection of incident light and reflected light onto the reflecting surface.

The magneto-optical signal emitted from the laminate 41, that is, the rate of change ΔR / R of the reflected light intensity due to the application of a magnetic field is the angle θ _P of the polarization plane of the light incident on the laminate 41 as shown in FIG. It fluctuated according to. Here, the relational expression between the change rate ΔR / R of the reflected light intensity and the angle θ _P of the polarization plane of the incident light is

と表すことができた。したがって、計測光の偏光面の角度θ_Ｐ、つまり旋光度は、計測光の変化率ΔＲ／Ｒを測定することで、

It was possible to express. Therefore, the angle θ _P of the polarization plane of the measurement light, that is, the optical rotation is obtained by measuring the rate of change ΔR / R of the measurement light.

より導出することができる。
図５（ｂ）は、磁気光学変調素子４０に入射する計測光の偏光角、つまり旋光度が、偏光子を回動させることで初期状態から＋１．２度回転した場合に、磁気光学変調素子４０から出射される磁気光学信号の変化する様子を示している。最初に、磁気光学変調素子４０から出射される磁気光学信号、つまり反射光の強度変化が最も大きくなるように偏光子を回動させて、これを初期状態、つまり旋光度がゼロとする。次に、偏光子を時計回りに回動させることで偏光角を＋１．２度に設定して、同様に磁気光学変調素子４０から出射される磁気光学信号を計測する。このとき、図５（ｂ）から分かるように、光検出器１７で計測される磁気光学信号は、初期状態の±４８．４％から、偏光角を＋１．２度とすることで±３８．４％に変化した。したがって、式３にΔＲ／Ｒ＝３８．４を代入することで、旋光度θ_Ｐは＋１．２１度と求めることができ、偏光子による設定値とよく一致することが確認できた。

Can be derived.
FIG. 5B shows the magneto-optical modulation element when the polarization angle of the measurement light incident on the magneto-optical modulation element 40, that is, the optical rotation is rotated by +1.2 degrees from the initial state by rotating the polarizer. A state in which a magneto-optical signal emitted from 40 changes is shown. First, the polarizer is rotated so that the intensity change of the magneto-optical signal emitted from the magneto-optical modulation element 40, that is, the reflected light is maximized, and this is set to the initial state, that is, the optical rotation is zero. Next, the polarizing angle is set to +1.2 degrees by rotating the polarizer clockwise, and the magneto-optical signal emitted from the magneto-optical modulation element 40 is measured in the same manner. At this time, as can be seen from FIG. 5B, the magneto-optical signal measured by the photodetector 17 is ± 38.4 by changing the polarization angle to +1.2 degrees from ± 48.4% in the initial state. It changed to 4%. Therefore, by substituting [Delta] R / R = 38.4 to Equation 3, the optical rotation angle theta _P can be determined as Tasu1.21 degrees, that good agreement with the set value by the polarizer was confirmed.

  In the present embodiment, the case where the optical rotation is measured by measuring the amount of decrease in the change rate of the reflected light intensity has been described, but the present invention is not limited to this. The angle of the polarization plane of incident light in the initial state can be set to an arbitrary angle. In particular, the optical rotation can be measured with high resolution by setting the initial state of the polarizer 13 to an angle at which the magneto-optical signal shows a steep change.

  Further, in the optical rotation measuring device as described above, the magneto-optical signal measured by the photodetector 17 is detected in synchronization with the magnetic field applied to the laminate 15 from the magnetic field application mechanism 18 or the metal current layer 34. Therefore, performing synchronous measurement or Fourier analysis using a periodically varying magnetic field is effective in improving measurement accuracy by reducing noise in the magneto-optical signal.

  As another method of measuring the optical rotation, the polarizer 13 is rotated by rotating the hollow motor 12 so that the magneto-optical signal from the laminate 15 is maximized in a state where the measurement object is injected into the sample cell 14. It is also effective to obtain the optical rotation by measuring the rotation angle of the polarizer 13 at this time as the amount of change from the initial state. In this case, the optical rotation can be measured with high accuracy even for a measurement object having a large optical rotation.

[Second Embodiment]
FIG. 6 is a configuration diagram schematically showing an optical rotation measuring device 50 according to the second embodiment of the present invention. The optical rotation measuring device 50 is based on a longitudinal Kerr effect optical system, which is one of the magnetic Kerr effects, and irradiates light on the surface of the laminate 15 functioning as a magneto-optic modulation element from an oblique direction. Magneto-optics, which is a change in the angle of the polarization plane of reflected light that occurs when an alternating magnetic field is applied in the same direction with respect to the projection of incident light and reflected light onto the reflecting surface, that is, in-plane direction with respect to the drawing surface of FIG. The optical rotation is measured by measuring the signal. In the present embodiment, the optical rotation measuring device 50 includes a polarizer 13 that uses light emitted from the light source 11 as linearly polarized light, a sample cell 14 that contains a measurement object, and light that has passed through the measurement object by changing the polarization angle. A laminate 15 for converting to a certain magneto-optical signal, an analyzer 23 for converting a magneto-optical signal reflected from the laminate into a change in light intensity, and detecting the intensity of light transmitted through the analyzer It is comprised by the photodetector 17 for doing.

  Here, in the optical rotation measuring device 50 of the present embodiment, the magnetic field application mechanism 18 applies alternating current to the laminate 15 that functions as a magneto-optic modulation element in the same direction with respect to the projection of incident light and reflected light onto the reflecting surface. Except for being configured to apply a magnetic field and including an analyzer 23 for converting a magneto-optical signal, which is a change in the polarization angle of light reflected from the laminate 15, into a change in light intensity. This is the same as the embodiment. Further, the magnetic field application mechanism 18 is not limited to the configuration shown in FIG. 6, and is formed on the stacked body 15 via the insulator layer 33 as in the other optical rotation measuring devices of the first embodiment. A configuration in which an alternating current is supplied to the formed metal current layer 34 may be used.

  As in the case of the first embodiment, the magneto-optic modulation element of the optical rotation measuring device 50 of the present embodiment is a laminate 15 in which a metal magnetic layer 32, a dielectric optical interference layer 31, and a metal reflection layer 30 are laminated. The structure of the laminate 15 and the material and thickness of each layer constituting the laminate 15 are preferably the same as those in the first embodiment for the same reason as in the first embodiment. .

  The principle of optical rotation measurement by the optical rotation measurement device 50 of this embodiment will be described with reference to FIGS.

When a magnetic field in the same direction is applied to the reflecting surface of the incident light and the reflected light in a state where linearly polarized light is incident on the laminated body 15 constituting the magneto-optic modulation element from an oblique direction, FIG. As shown, the reflected light from the laminate 15 is emitted as a magneto-optical signal that is a change in polarization angle according to the magnetization direction of the metal magnetic layer 32. Such a configuration is generally called a vertical Kerr effect. Specifically, the polarization angle is θ in a state where a magnetic field (+ H ₂ or −H ₂ ) having a predetermined intensity capable of setting the magnetization of the metal magnetic layer 32 in one direction is applied to the stacked body 15. When the linearly polarized light is incident, the light reflected from the laminated body 15 due to a large magneto-optical effect due to the multiple reflections generated inside the laminated body 15 undergoes a large angle change (+ Δθ ₂ or −Δθ ₂ ) of the polarization plane. It is emitted. That is, the magneto-optic curve of the laminate 15 constituting the magneto-optic modulation element is as shown in FIG. 7B according to the applied magnetic field.

FIG. 8A shows the relationship between the magneto-optical signal (θ + Δθ ₂ or θ−Δθ ₂ ) reflected from the laminated body 15 and the polarization direction of the analyzer 23. The magneto-optical signal reflected from the laminate 15 is converted into a change in light intensity (I + ΔI ₂ or I−ΔI ₂ ) by passing through the analyzer 23 and is incident on the photodetector 17. 17 outputs an AC signal of + ΔV ₂ or −ΔV ₂ . FIG. 8B shows an output signal of the photodetector 17 when the polarizer 13 is rotated to change the polarization plane of the light incident on the stacked body 15. The AC output of the photodetector 17 depends on the angle of the polarization plane of the light incident on the laminate 15 and the polarization direction of the analyzer 23. In particular, when both become the same angle, the output signal is zero. It becomes. Accordingly, the hollow motor 12 is rotated to rotate the polarizer 13 so that the output signal of the photodetector 17 becomes zero, and the rotation angle of the polarizer 13 at this time is defined as the amount of change from the initial state. By measuring, it is possible to measure the optical rotation of the measurement object.

  Actually, the longitudinal Kerr effect is measured with respect to the magneto-optic modulation element 40 shown in FIG. 4 shown as an example in the first embodiment, which is about the same as the Faraday cell used in the conventional optical rotation measuring device. A magneto-optical signal, which is a change in polarization angle of about ± 8 degrees, was confirmed. Since the magneto-optic modulation element of this embodiment is composed of a thin film laminate, the apparatus can be made smaller than a conventional optical rotation measuring apparatus.

  Also in this embodiment, as in the case of the first embodiment, performing synchronous measurement or Fourier analysis using a periodically changing magnetic field is effective in improving the measurement system by reducing noise in the magneto-optical signal. It is. Furthermore, when the metal current layer 34 formed through the insulator layer is used as the magnetic field application mechanism in the stacked body 15, the apparatus configuration is further simplified as in the case of the first embodiment. There exists an effect that the optical rotation measuring device which can be reduced in size and can be provided at low cost can be provided.

  It is also effective to use a differential detection method generally known in the magneto-optical recording system as another method for measuring the polarization angle. Specifically, by using a polarization beam splitter and two photodetectors instead of the analyzer 23, the intensity of the light split into two lights by passing through the polarization beam splitter can be reduced to two. It is possible to derive the polarization angle by detecting with a photodetector and measuring the intensity ratio. In this method, even when the intensity of light emitted from the light source fluctuates, it is possible to perform measurement with low noise and to provide an effect that a high-performance optical rotation measuring device can be supplied.

[Third Embodiment]
FIG. 9 is a configuration diagram schematically showing an optical rotation measuring device 60 according to the third embodiment of the present invention. As shown in FIGS. 9 and 10, the optical rotation measuring device 60 is based on a polar Kerr effect optical system that is one of the magnetic Kerr effects, and with respect to the surface of the laminate 15 that functions as a magneto-optic modulation element. A magneto-optical signal which is an angle change (+ Δθ ₃ or −Δθ ₃ ) of the polarization plane of the reflected light generated when an alternating magnetic field is applied to the laminate 15 in the same direction as the incident light in a state where light is irradiated from the vertical direction. The optical rotation is measured by measuring. The magneto-optic curve of the laminate 15 constituting the magneto-optic modulation element is as shown in FIG. 10B according to the applied magnetic field. In the present embodiment, the optical rotation measuring device 60 uses a polarizer 13 that makes light emitted from the light source 11 linearly polarized light, a sample cell 14 into which the measurement object is placed, and the measurement light that has passed through the measurement object by the magneto-optical effect. A laminate 15 for converting to a magneto-optic signal that is a change in polarization angle, a half mirror 22 for guiding the magneto-optic signal reflected from the laminate 15 to the band-pass filter 16, and a magnet that has passed through the band-pass filter 16. It comprises an analyzer 23 for converting an optical signal into a change in light intensity, and a photodetector 17 for detecting the intensity of light transmitted through the analyzer 23.

Here, the optical rotation measuring device 60 of the present embodiment is arranged to irradiate the laminated body 15 with linearly polarized light from the vertical direction, and is a half for guiding the light reflected from the laminated body 15 to the photodetector 17. The second embodiment is the same as the second embodiment except that the mirror 22 is provided and the magnetic field application mechanism 18 is configured to apply a magnetic field (+ H ₃ or −H ₃ ) in the vertical direction to the surface of the stacked body 15. Similarly, the optical rotation is measured by a method similar to the method described in FIG.

  However, the laminated body 15 functioning as the magneto-optical modulation element of the present embodiment is configured by the laminated body 15 in which the metal reflection layer 30, the dielectric optical interference layer 31, and the metal magnetic layer 32 are laminated in this order on the substrate. The stacking order is the reverse of that in the second embodiment. Also in the present embodiment, the thickness of each layer constituting the stacked body 15 needs to be a condition that the magneto-optical signal is enhanced by multiple reflection occurring inside the stacked body. Specifically, the dielectric optical interference layer 31 needs to be set to a thickness at which the light irradiated on the multilayer body 15 causes multiple reflection inside the multilayer body 15. A value obtained by multiplying each thickness of the magnetic layer 32 by the refractive index is preferably thicker than about ¼ with respect to the wavelength of light to be irradiated. Further, the metal magnetic layer 32 needs to have a thickness that allows the light irradiated to the multilayer body 15 to enter the multilayer body 15 and is desirably 30 nm or less. In addition, the metal reflection layer 30 needs to have a thickness sufficient to reflect light that has entered the laminated body 15 and is preferably 30 nm or more. Further, the laminated body 15 has not only the above-described configuration but also the metal magnetic layer 32, the dielectric optical interference layer 31, and the metal reflective layer 30 on the substrate, as in the optical rotation measuring device of the second embodiment. You may laminate | stack in order.

  The material used for the metal magnetic layer 32 of this embodiment is preferably a material having an axis of easy magnetization in the direction perpendicular to the film surface in order to efficiently magnetize the metal magnetic layer 32 in the direction perpendicular to the film surface. Specifically, a CoPt alloy film (alloy thin film of cobalt and platinum), an FePt alloy film, a TbFeCo alloy film, a Co / Pt multilayer film, a Co / Pd multilayer film, a Co / Ni multilayer film, and the like can be given. By using these materials, it becomes possible to provide an optical rotation measuring device with low power consumption.

  FIG. 11 is a cross-sectional view schematically showing a magneto-optical modulation element 70 constituting the optical rotation measuring device according to the example of the present embodiment.

  In the magneto-optic modulation element 70 of this embodiment, a base layer 75 made of a ZnO thin film having a thickness of 10 nm is formed on a glass substrate 76, and a laminate 71 for actually measuring the optical rotation is formed thereon. Yes. The laminated body 71 is made of an Ag thin film having a thickness of 100 nm as the metal reflective layer 74, a ZnO thin film having a thickness of 60 nm as the dielectric optical interference layer 73, and a CoPt alloy thin film having a thickness of 5 nm as the metal magnetic layer 72. It is comprised by the structure laminated | stacked in order.

  FIG. 12A shows a magnetic field that fluctuates periodically from −1 kOe (downward in FIG. 11) to +1 kOe (upward in FIG. 11) in a direction perpendicular to the surface of the magneto-optic modulation element 70 having the above configuration. FIG. 5 shows a change in the polarization angle of the reflected light from the magneto-optic modulation element 70 when linearly polarized light is incident on the magneto-optic modulation element in a vertical manner in the applied state. The magneto-optic modulation element 70 emits a magneto-optic signal having a polarization angle change of about ± 13 degrees depending on whether the magnetization direction of the metal magnetic layer 72 is upward or downward. As described above, this is a magneto-optical signal equal to or higher than that of the Faraday cell used in the conventional optical rotation measuring apparatus. In the magneto-optical modulation element of this embodiment configured by a thin film stack, It is possible to provide a smaller optical rotation measuring device than

  FIG. 12B shows the result of actually measuring the polarization angle of the incident light, that is, the optical rotation using the magneto-optic modulation element 70 by the method described with reference to FIG. The offset amount of the polarizer, which is the vertical axis in FIG. 12B, is the rotation of the polarizer necessary to make the angle of the polarization plane of the light reflected from the magneto-optic modulation element 70 the same as the polarization direction of the analyzer. Shows the angle. The offset amount of the polarizer and the polarization angle of the incident light are in good agreement, and the optical rotation (the polarization angle of the incident light) can be measured by measuring the offset amount of the polarizer from the initial state. It was confirmed that it was possible.

  Also in the optical rotation measuring device of this embodiment, as in the first and second embodiments, performing synchronous measurement or Fourier analysis using a periodically changing magnetic field is a noise of a magneto-optical signal. It is effective in improving the measurement system by reducing the amount.

  As in the case of the second embodiment, as a method for measuring the polarization angle of measurement light, a differential detection method is used by using a polarization beam splitter and two photodetectors instead of an analyzer. It is also effective to do. In this method, even when the intensity fluctuation of the light emitted from the light source occurs, it is possible to perform measurement with low noise and to provide an effect that a high-performance optical rotation measuring device can be supplied.

  The optical rotation measuring device according to the present invention can be used as an optical rotation measuring device for measuring the optical rotation of an optically active substance.

10, 50, 60 ... Optical rotation measuring device, U ... Light source unit, 11 ... Light source,
12 ... Hollow motor, 13 ... Polarizer, 14 ... Sample cell, 15, 41, 71 ... Laminate,
16 ... band pass filter, 17 ... photodetector, 18 ... magnetic field application mechanism, 19 ... current source,
20 ... computer, 21 ... motor driver, 22 ... half mirror, 23 ... analyzer,
30, 42, 74 ... metal reflective layer, 31, 43, 73 ... dielectric optical interference layer,
32, 44, 72 ... metal magnetic layer, 33 ... insulator layer, 34 ... metal current layer,
40, 70: magneto-optic modulation element, 45, 75: underlayer, 46, 76: glass substrate.

Claims (10)

At least a light source unit that emits linearly polarized light, a magneto-optic modulation element composed of a laminate including a metal magnetic layer, a dielectric optical interference layer, and a metal reflection layer, a magnetic field application mechanism, and a photodetector,
Multiplexing that occurs in the laminate when the linearly polarized light emitted from the light source unit is incident on a measurement object and the linearly polarized light after passing through the measurement object is incident on the magneto-optic modulation element as incident light. By irradiating light from the light source unit under conditions where the magneto-optical signal is enhanced by reflection,
The rotation angle of the polarization plane of the linearly polarized light accompanying the measurement object is controlled by controlling the magnetization of the laminate by the magnetic field application mechanism, so that the magneto-optical signal that is a change in the reflected light from the laminate can be obtained. An optical rotation measuring device for measuring the optical rotation of the measurement object by converting and measuring with the photodetector. The light source unit is
A light source that emits light;
A polarizer having the light emitted from the light source as the linearly polarized light;
Rotation means for rotating the polarizer to adjust the angle of the polarization plane of the linearly polarized light applied to the magneto-optic modulation element;
The optical rotation measuring device according to claim 1, comprising: The magnetic field application mechanism comprises a metal current layer, and an insulator layer formed between the laminate and the metal current layer,
2. The optical rotation measuring device according to claim 1, wherein the magnetic field application mechanism controls the magnetization of the metal magnetic layer constituting the stacked body by applying an alternating current to the metal current layer. 3. .   The magnetic field application mechanism applies a magnetic field in a direction orthogonal to the projection of the incident light and the reflected light on the laminate, and the photodetector is a change in the intensity of the reflected light. The optical rotation measuring device according to claim 1, wherein an optical signal is detected.   The magnetic field application mechanism applies a magnetic field in the same direction with respect to the projection of the incident light and the reflected light onto the laminate, and the photodetector detects a change in the angle of the polarization plane of the reflected light. 2. The optical rotation measuring device according to claim 1, wherein the magneto-optical signal is detected.   The magneto-optics wherein the magnetic field application mechanism applies a magnetic field in the normal direction of the incident light and the reflected light to the laminate, and the photodetector is a change in the angle of the polarization plane of the reflected light The optical rotation measuring device according to claim 1, wherein a signal is detected.   2. The optical rotation measuring device according to claim 1, wherein the metal magnetic layer constituting the laminated body is a magnetic material having an easy axis of magnetization in the in-plane direction of the film.   The optical rotation measuring device according to claim 7, wherein the metal magnetic layer constituting the laminated body is an alloy thin film of iron and cobalt.   The optical rotation measuring apparatus according to claim 1, wherein the metal magnetic layer constituting the laminate is a magnetic material having an easy axis of magnetization in a direction perpendicular to the film surface.   The optical rotation measuring apparatus according to claim 9, wherein the metal magnetic layer constituting the laminated body is an alloy thin film of cobalt and platinum.

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