JP3778670B2 - Opto-magneto-optic effect measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for measuring a photo-magneto-optic effect (Faraday effect and / or magnetic Kerr effect) relating to magnetorotation, and more particularly, to measuring a photo-magneto-optic effect for measuring the effect in a short wavelength band of a sample. Relates to the device.
[0002]
[Prior art]
Jpn. J. et al. Appl. Phys. Vol. 32 (1993), pages 989-995, introduces the newest photo-magneto-optic effect measuring device known today. In this apparatus, light from a light source is incident on a spectroscope to extract light having a necessary wavelength. The extracted light is linearly polarized by the first polarizer and then irradiated onto the sample. Here, a magnetic field is applied to the sample by an electromagnet. When measuring the Faraday effect, the light transmitted through the sample is observed. When measuring the magnetic Kerr effect, the light reflected by the sample is observed. In any case, the intensity of the light transmitted through the sample or reflected by the sample is detected after passing through the second polarizer. The above measurement method is common to the cross-Nicol method, the Faraday cell method, the rotation analyzer method, and the circular polarization modulation method.
[0003]
[Problems to be solved by the invention]
By the way, in recent ultra-high density storage technology using the magneto-optic effect, in order to improve the storage density, there is a tendency for light of shorter wavelengths to be used. Realization of a magneto-optical effect measurement technique is desired. For example, the photo-magneto-optical effect measuring apparatus described in the above paper has also been improved so that measurement with short wavelength light is possible, and measurement up to a wavelength of around 210 nm is possible.
[0004]
However, measurement at a wavelength of 200 nm or less is impossible even with the apparatus described in the above paper. That is, light in a short wavelength region of 200 nm or less, referred to as vacuum ultraviolet light, is significantly absorbed and attenuated in the atmosphere or in a lens or the like. Therefore, in order to enable measurement in a wavelength region of 200 nm or less, it is not necessary to use a light source having a continuous spectrum in the wavelength region such as a deuterium lamp. A breakthrough is required to ensure the necessary S / N ratio.
The present invention has been made in view of such a point, and realizes the breakthrough, and an optical-magneto-optical effect measuring apparatus capable of measuring an optical-magneto-optical effect with short-wavelength light having a wavelength of 200 nm or less. Is intended to provide.
[0005]
[Means for Solving the Problems]
  In order to achieve the above object, in the present invention,A light source unit, a spectroscope that separates light from the light source unit and extracts light of a necessary wavelength, a first polarizer that polarizes light extracted by the spectroscope, and a magnetic field is applied to the sample A sample holding unit provided with means, and a second light that passes through the sample irradiated from the first polarizer to the sample mounted on the sample holding unit or the light reflected by the sample. And a photo-magneto-optic effect measurement apparatus comprising: a polarizer; and a photodetector that detects the intensity of light that has passed through the second polarizer.
  The light source unit is configured to emit short wavelength light having a wavelength of 200 nm or less,
  The optical path of the short wavelength light from the light source part to the photodetector is housed in a container that can be sealed together with the sample holder,
  The container is capable of transmitting the short-wavelength light and mutually incapable of gas flow between a container including a sample holder and a container including an optical system including a first polarizer and a second polarizer. With a vacuum ultraviolet light transmitting member separated by
  Here, the container including the sample holder is provided with a vent for opening and closing the gas in the container so as to be openable and closable, and the optical system includes the first polarizer and the second polarizer. The container containing the system is provided with an exhaust means for discharging the gas in the container,
  In measuring the magneto-optical effect, a container including the optical system including the first polarizer and the second polarizer is used while the container including the sample holder is replaced with a gas not containing oxygen. Provided is a photo-magneto-optic effect measuring device characterized in that the inside is realized in a vacuum state.
  In this specification, “vacuum” refers to a vacuum as an engineering predicate, and does not mean a so-called absolute vacuum. Therefore, the state of the space where the pressure is reduced to such an extent that so-called vacuum ultraviolet light having a wavelength of 200 nm or less can be transmitted without much attenuation is typical of the vacuum state in this specification.
[0006]
  In the present invention, an optical path from the light source unit to the photodetector is ensured in the sealed space in the container. Furthermore, without obstructing the optical path, the container contains the sample holding part and is provided with the ventilation port and the part that does not contain the sample holding part and is provided with the exhaust means. It is divided. Accordingly, most of the optical path (that is, the container including the sample holding unit and the container including the optical system including the first polarizer and the second polarizer) is placed under vacuum, while surrounding the sample holding unit. Can be replaced with a gas containing no oxygen. Therefore, the sample holder can be kept under the same atmospheric pressure as the outside air, and the sample replacement operation in the sample holder can be easily performed. In addition, since the sample holder is not depressurized at the time of measuring the magneto-optical effect, it can be applied to measurement of samples having various shapes and properties.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, preferred embodiments of the magneto-optical effect measuring apparatus of the present invention will be described in detail with reference to the drawings.
[0010]
First, a measurement apparatus suitable as the first apparatus of the present invention will be described as the first embodiment. FIG. 1 is a plan view schematically showing the appearance of the magneto-optical effect measuring apparatus according to the present embodiment. FIG. 2 is a plan view schematically showing the layout of various main components (optical elements) in the photo-magneto-optic effect measurement apparatus according to the present embodiment with the Faraday effect measurement unit attached.
As shown in FIG. 1, the measurement apparatus according to the present embodiment roughly includes a light source unit 101 including a deuterium lamp 102 and a xenon lamp 108 described later as light sources, and light emitted from the light source unit 101. A spectroscope 120 for taking out light of a desired wavelength while splitting light, and optical elements such as a first polarizer 150, a second polarizer 156, and a Kerr effect measurement photodetector clearly shown in FIG. An optical system box 165, an electromagnet 172 corresponding to a means for applying a magnetic field to the sample 176, and a sample holder 175 formed so as to be surrounded by the electromagnet 172. Are also arranged on a surface plate 200 (that is, an optical bench called an optical bench).
[0011]
Thus, as shown in FIG. 1, a portion of the light source unit 101 that generates short-wavelength light having a wavelength of 200 nm or less (ie, a portion related to the deuterium lamp 102), a spectroscope 120, an optical system box 165, and an electromagnet unit 169. (Including the electromagnet 172 and the sample holder 175. The same applies hereinafter) are accommodated in containers 106, 142, 166, and 170 that can be sealed. These containers 106, 142, 166, and 170 are made of a high-strength material (preferably a metal that can be used in a vacuum dryer, etc.) that can maintain its shape even when an excessive pressure difference occurs inside and outside the container with the inside being in a vacuum state. (Or glass) and shielded (for example, welding or rubbing via grease when the container is made of thick glass or the like) in a state where it can be mutually ventilated. Thereby, one container is formed as a whole for accommodating various optical elements (excluding the xenon lamp 108 system) constituting the measuring apparatus according to the present embodiment. As a result, the optical path from the light source section to the Kerr effect measurement photodetector through the sample to the short wavelength light having a wavelength of 200 nm or less is accommodated in the container.
[0012]
On the other hand, a control valve such as an electromagnetic valve corresponding to the exhaust means in the present embodiment is provided at one end of the container 106 that stores the light source unit 101 (deuterium lamp 102 system) and the container 166 that stores the optical system box 165. Exhaust pipes 114 and 115 having 113 and 116 are provided. Thus, by connecting a gas suction device such as an external vacuum pump or aspirator (not shown) to the exhaust pipes 114 and 115, the gas inside the containers 106, 142, 166, and 170 is sucked and removed, and the containers 106, The inside of 142,166,170 can be made into a vacuum state. Therefore, in the measurement apparatus according to the present embodiment, the optical path from the light source unit 101 to the Kerr effect measurement photodetector, which will be described later, from the light source unit 101 to the short wavelength light having a wavelength of 200 nm or less can be placed under a vacuum condition. .
[0013]
Hereinafter, main components of the measurement apparatus according to the present embodiment and measurement procedures in the measurement apparatus will be described in detail.
[0014]
As described above, the light source unit 101 of the measuring apparatus according to the present embodiment includes two types of lamps, that is, the deuterium lamp 102 and the xenon lamp 108 as light sources. Among these, the deuterium lamp 102 can suitably emit light including short wavelength light having a wavelength of 200 nm or less. As shown in FIG. 2, the short wavelength light emitted from the deuterium lamp 102 is reflected and collected by the concave reflecting mirror 104 and is incident on the first incident slit 121 of the spectrometer 120. The concave reflecting mirror 104 polishes the surface of quartz (which may be replaced with SiC), coats the polished surface with Pt (which may alternatively be replaced with Au), and further, Al-MgF.₂The film has a characteristic of reflecting best at 160 nm where the lamp intensity is low. Here, the reflectance at 160 nm is 84 to 86%. In addition, the same surface treatment is given also to each reflective mirror and concave-surface reflective mirror mentioned later, and can reflect short wavelength light with high efficiency. As described above, the optical path from the deuterium lamp 102 to the first incident slit 121 is secured in the container 106 provided with the exhaust means. For this reason, by making the inside of the container 106 in a vacuum state as described above, short wavelength light of 200 nm or less generated from the deuterium lamp 102 can be incident on the spectroscope 120 with almost no attenuation.
[0015]
On the other hand, reference numeral 108 in FIGS. 1 and 2 denotes a xenon lamp, which has an emission wavelength band on the longer wavelength side than the deuterium lamp 102. That is, the emission wavelength bands of the xenon lamp 108 and the deuterium lamp 102 overlap, and the deuterium lamp 102 is preferentially used at a wavelength of 300 nm or less including short wavelength light of 200 nm or less, and the xenon lamp 108 is used at a wavelength of 300 nm or more. Is used. Since light having a wavelength of 300 nm or more is not easily attenuated by a gas such as oxygen, in the present embodiment, the xenon lamp 108 is laid out to be used in the atmosphere. Thus, the light from the xenon lamp 108 in the light source unit 101 is collected and reflected by the concave reflecting mirror 110 and the reflecting mirror 112 and is incident on the second incident slit 122 of the spectroscope 120 (FIG. 2).
[0016]
Next, the spectroscope 120 of the measuring apparatus according to the present embodiment will be described in detail. The spectroscope 120 according to this embodiment is configured without using optical elements that strongly attenuate short-wavelength light such as prisms and lenses in order to extract short-wavelength light having a wavelength of 200 nm or less without much attenuation. That is, as shown in FIG. 2, the spectroscope 120 includes a switching mirror 123 in the vicinity of the inside of the first incident slit 121 and the second incident slit 122, and light from either one of the incident slits 121 and 122. Is guided to the concave reflecting mirror 126. The symbol (m) in FIG. 2 indicates an element that is movable by the step motor (m). For example, the switching mirror 123 is switched by the step motor 123m. Each step motor is controlled by a computer 192 connected to the measuring apparatus. Note that the switching mirror 123 can be switched manually by the handle 123a (see FIG. 3).
[0017]
As shown in FIG. 3, in the spectroscope 120, light incident from either the first incident slit 121 or the second incident slit 122 is reflected by the switching mirror 123 and then reflected by the concave reflecting mirror 126. And is incident on one of the diffraction gratings 130, 132, and 134. These three diffraction gratings 130, 132, and 134 are arranged on a turntable 128 so as to form a triangle in plan view, and the turntable 128 is rotated as indicated by an arrow in the drawing, and any one of the diffraction gratings. Can be used selectively. FIG. 3 shows a state where the diffraction grating 134 is placed at the use position. The turntable 128 is rotated by a step motor 128m and a worm gear 129. The diffraction grating 130 has the shortest inter-grating distance and is used for spectroscopy with a wavelength of 400 nm or less. On the other hand, the diffraction grating 134 has the longest inter-grating distance and is used for spectroscopy with a wavelength of 800 nm or more. The diffraction grating 132 has an intermediate inter-grating distance and is used for spectroscopy with a wavelength of 400 nm to 800 nm.
The step motor 128m is used not only to select a diffraction grating to be used, but also to finely adjust the reflection angle of the selected diffraction grating to switch the wavelength of light reflected toward the concave reflecting mirror 136. The light having the wavelength selected by adjusting the angle of any one of the diffraction gratings is reflected by the concave reflecting mirror 136 and the reflecting mirror 138 and condensed on the exit slit 140. In this way, light having a wavelength necessary for measurement is extracted from the spectroscope 120. As described above, the spectroscope 120 as a whole is also housed in a sealable container 142. By making the container 142 into a vacuum state as described above, the wavelength within the spectroscope 120 is 200 nm or less. Attenuation of short wavelength light is prevented.
[0018]
Next, the optical system box 165 of the measuring apparatus according to the present embodiment will be described.
Immediately after the exit slit 140, a filter 144 is provided for removing diffracted light having a higher order from the light reflected from the diffraction grating at the same angle. As shown in FIG. 3B, the filter 144 is provided with six through holes in a disk that rotates about the axis 144x, and five of the through holes are specified. A filter plate for cutting the wavelength is incorporated. The wavelength band characteristics to be cut by each filter plate are different from each other, and the filter plate to be used is switched according to the wavelength to be used. On the other hand, no filter plate is incorporated in the through hole 144a, and light passes through. The through-hole 144a and the filter plates 144b to 144f are switched by a filter motor 144m and its rotating shaft 145.
[0019]
On the other hand, as shown in FIG. 2, a concave reflecting mirror 146, a reflecting mirror 148, a first polarizer 150, and a photoelastic modulator (modulator) 152 are provided behind the filter 144. The light having a specific wavelength selected by the filter 144 can be changed into linearly polarized light and circularly polarized light.
That is, the light having a specific wavelength selected by the spectroscope 120 and the filter 144 that cuts high-order diffracted light is then condensed and reflected by the concave reflecting mirror 146 and the reflecting mirror 148 and directed to the sample 176 ( Figure 2). The concave reflecting mirror 146 collects light on the surface of the sample 176. The reflecting mirror 148 is rotatable about the horizontal axis and the vertical axis, and the angle is adjusted so that the reflected light from the sample 176 enters the concave reflecting mirror 158 described later. For this purpose, a horizontal motor 148m1 and a vertical motor 148m2 are attached to the reflecting mirror 148.
[0020]
As shown in FIG. 4, the light that has passed through the first polarizer 150 is linearly polarized. The obtained linearly polarized wave then passes through the photoelastic modulator 152. In this embodiment, the photoelastic modulator 152 has a built-in piezoelectric element that vibrates at a frequency of 50 KHz, and the vibration direction is inclined 45 ° counterclockwise with respect to the linearly polarized wave. That is, as shown in FIG. 4, the linearly polarized wave is divided into a wave in a plane inclined by 45 ° clockwise (indicated by white in the figure) and a wave inclined by 45 ° counterclockwise (shown in FIG. 4). The photoelastic modulator 152 changes the phase of the wave in the vibration direction (black wave) and the wave perpendicular to it (the white wave). Does not change the phase. Here, the phase change is delayed or advanced at a frequency equal to the frequency (50 KHz). That is, the light passing through the photoelastic modulator 152 is modulated into circularly polarized light, and the modulation frequency is 50 KHz in this case. As described above, after the wavelength is selected by the spectroscope 120 and the filter 144, the light circularly polarized at the frequency of 50 KHz by the first polarizer 150 and the photoelastic modulator 152 passes through the stop 154. Incident on sample 176.
As described above, the optical system box 165 that houses the first polarizer 150, the photoelastic modulator 152, and the like is also housed in a container 166 that can be hermetically sealed, and the interior of the container 166 is as described above. By making the vacuum state, the attenuation of short wavelength light having a wavelength of 200 nm or less in the optical system box 165 is prevented, and the light enters the sample 176 in the electromagnet portion 169 with almost no attenuation.
[0021]
Next, the electromagnet unit 169 in this measuring apparatus will be described.
As shown in FIG. 2, the sample 176 to be measured for the photo-magneto-optic effect in this measuring apparatus is accommodated in a sample holder 174 whose light irradiation surface is flat, and a gap sandwiched between mounting portions 172 a of an electromagnet 172. The formed sample holder 175 is attached. The sample holder 174 is provided with a light transmission window formed of a material that does not absorb short wavelength light (typically, fused silica). The sample holder 174 incorporates a cooling device for adiabatic expansion of liquid nitrogen to cool the sample 176 and a heater (none of which is shown) for heating the sample 176, and the sample temperature is set to 80 to 600. Variable in the range of ° k. The interior of the sample holder 174 is preferably filled with an inert gas to prevent the sample from being oxidized when the sample is heated.
Thus, as shown in FIGS. 1 and 2, the sample holder 174 is set in the mounting portion 172a of the electromagnet 172 in which a hole for securing an optical path is formed, and a magnetic field up to 20 KOe is applied to the sample 176. It is possible to do. Here, in the present embodiment, an O-ring 171 is appropriately mounted on one mounting portion 172a (near the optical system box 165). Accordingly, the sample holder 174 can be pressed and held in the sample holding portion 175 with the O-ring 171 sandwiched between the mounting portion 172a. Thus, even when the inside of the container 170 that houses the electromagnet portion 169 is in a vacuum state, the light irradiation surface of the sample holder 174 can be stably held, and the reproducibility of measurement can be ensured.
[0022]
Next, the arrangement part of the second polarizer 156 and the photodetector for measuring the Kerr effect in this measuring apparatus will be described.
As shown in FIG. 2, in the optical system box 165, the Kerr effect measurement photodetector (ie, the germanium diode 160 and the photoelectron amplifier tube 162; the same applies hereinafter), the Kerr effect measurement second polarizer 156, and the concave reflection. The mirror 158 is set at a position where the light reflected from the sample 176 can be measured (FIG. 1). Here, the second polarizer 156 can be rotated in a plane by a step motor 156m, and is adjusted to a zero angle after being rotated at the time of calibration as will be described later. On the other hand, the photoelectron amplifier 162 constituting the Kerr effect measurement photodetector is used for short wavelength detection, and the germanium diode 160 is used for long wavelength detection. The concave reflecting mirror 158a is rotated by the step motor 158m and condenses the measurement light on either the photoelectron amplifier tube 162a or the germanium diode 160a. The second polarizer 156 can be rotated in the plane by a step motor 156m, and is adjusted to a zero angle after being rotated at the time of calibration as will be described later. The photoelectron amplifier tube 162 is used for short wavelength detection, and the germanium diode 160 is used for long wavelength detection. The concave reflecting mirror 158 is rotated by the step motor 158m and condenses the measurement light on either the photoelectron amplifier tube 162 or the germanium diode 160. As described above, since the inside of the container 166 of the optical system box 165 can be in a vacuum state, the short wavelength light reflected from the sample 176 reaches one of the photoelectron amplifier tube 162 and the germanium diode 160. It is not attenuated in the middle of the optical path before.
[0023]
Incidentally, FIG. 1 shows an outline of an apparatus for measuring the Kerr effect as the measuring apparatus according to the present embodiment, but the present invention is not limited to this, and is similar to that for Kerr effect measurement. A device for measuring the Faraday effect can be obtained by appropriately arranging optical elements.
That is, as shown in FIG. 2, in order to measure the Faraday effect, the Faraday effect measurement photodetector (germanium diode 160a and photoelectron amplifier 162a similar to the Kerr effect measurement) and the Faraday effect measurement second polarization are measured. The child 156a and the concave reflecting mirror 158a are set at positions where the light reflected from the sample 176 can be measured (FIG. 2). As in the case of the Kerr effect measurement, the second polarizer 156a can be rotated in a plane by a step motor 156m, and is adjusted to a zero angle after being rotated during calibration as will be described later. The photoelectron amplifier tube 162a is used for short wavelength detection, and the germanium diode 160a is used for long wavelength detection. The concave reflecting mirror 158a is rotated by the step motor 158m and condenses the measurement light on either the photoelectron amplifier tube 162 or the germanium diode 160.
[0024]
As shown in FIG. 2, in the Faraday effect measurement unit, the Faraday effect measurement photodetectors 160a and 162a and the second polarizer 156a can all be sealed in the same manner as the containers 106, 142, 166, and 170. It is accommodated in a container 178 and is shielded and connected to the container 170 of the electromagnet portion 169 so that it can be vented. For this reason, the optical path in the container 178 can be kept under vacuum, and the short wavelength light transmitted through the sample 176 is attenuated in the optical path before reaching one of the photoelectron amplifier 162a and the germanium diode 160a. It will not be done.
[0025]
As described above, this measuring apparatus has been described for each main component. The outline of the overall configuration is summarized in FIG. This figure focuses on the optical system, and schematically shows a path until light from the deuterium lamp 102 or the xenon lamp 108 enters either the photoelectron amplifier tube 162 or the germanium diode 160. Yes.
[0026]
Hereinafter, an operation mode and a measurement method of the measurement apparatus will be briefly described.
The above-described various motors (m), the photoelastic modulator 152, and the like are controlled by a computer 192. The measurement data is also processed by the computer 192. Therefore, in this measuring apparatus, various control devices are provided so as to be controlled by a computer 192 in addition to the main components for measuring the above-described photo-magnetic effect.
For example, 182 and 180 in FIG. 2 are amplifiers for the photoelectron amplifier tube 162 and the germanium diode 160, respectively. 2 is a switch that is switched in conjunction with the concave reflecting mirror 158. While the concave reflecting mirror 158 focuses the measurement light on the germanium diode 160, the signal of the amplifier 180 for the germanium diode 160 is shown. Is input to the computer 192, and the signal of the amplifier 182 for the photoelectron amplifier tube 182 is input to the computer 192 while the light is condensed on the photoelectron amplifier tube 162.
[0027]
188 in FIG. 2 is a DC component voltmeter that detects a DC component of the detected light intensity, 184 is a first lock-in amplifier that detects the intensity of the component of the modulation frequency (in this case, 50 KHz), 186 This is a second lock-in amplifier that detects a component of twice the frequency (100 KHz). Each output value is input to the computer 192, and the result processed by the computer 192 is displayed on the display device 194. Note that reference numeral 190 in FIG. 2 denotes a feedback circuit. That is, during use of the photoelectron amplifier 162, the voltage applied to the optoelectronic amplifier 162 is feedback controlled in accordance with the DC component detected by the DC component voltmeter 188, and the detected value of the DC component voltmeter 188 is substantially constant. The gain of the photoamplifier tube 162 is feedback-controlled so as to reach a level.
[0028]
As shown in FIG. 4, when the Kerr effect is measured with this measuring apparatus, the angle formed between the incident light and the sample normal is 3 degrees or less, and the reflected light is the same. When this angle is 3 degrees or less, the measurement accuracy of the Kerr effect is kept good. Further, as shown in FIG. 4, the Kerr effect measurement second polarizer 156 is used on the basis of an angle (zero angle) that passes through the polarization modulated by the photoelastic modulator 152 and does not pass the unmodulated polarization. .
[0029]
6 and 7 show the electrical system configuration of the present measuring apparatus centered on the computer 192. FIG. In addition, the solid line arrow in FIG. 6 indicates an electric signal line related to control, and the thick solid line indicates a control bus. On the other hand, solid arrows in FIG. 7 indicate the path of light, and thin broken arrows indicate electrical signal lines related to control.
As shown in FIGS. 6 and 7, in this measuring apparatus, the computer 192 operates the step motors 123m and 128m via the spectroscope controller 401, and the types of the switching mirror 123 and the diffraction grating (130, 132, 134). Adjust the angle). This realizes switching of the wavelength and switching of the light source (xenon lamp 108 or deuterium lamp 102). Similarly, the step motor 144m can be operated via the filter controller 402, and any one of the through holes 144a to be used and the filter plates 144b to f can be selected. Further, the operation of the motor 148m (the horizontal motor 148m1 and the vertical motor 148m2) of the reflecting mirror 148 is controlled via the condensing system controller 403 to irradiate the sample 176 with desired light.
The outline of the control of the optical system is shown in FIG. The arrows in the figure indicate the optical path of light, and the broken lines indicate the relationship between the various motors (m) described above and the optical system devices that are operated by the motors (m). In the drawing, a thin solid line indicates an electric signal line, and a thick solid line indicates a control bus.
[0030]
Similarly, the computer 192 operates the step motors 156m and 158m via the detection system controller 404 to switch the angle of the second polarizer (also referred to as an analyzer; hereinafter the same) 156 and the angle of the concave reflecting mirror 158. be able to.
[0031]
On the other hand, a Hall element 177 is disposed in the vicinity of the sample holder 174, and the magnitude and direction (intensity) of the magnetic field applied to the sample are input to the computer 192 via the magnetic field measuring means 405 such as a gauss meter. Further, the computer 192 controls the heater and the cooling device (179 in FIG. 6) via the sample heating / cooling controller 406 based on the temperature measured by the thermometer incorporated in the sample holder 174. The temperature is feedback controlled around the value set by the operator.
[0032]
Furthermore, the computer 192 switches the switch 183 via the switch controller 407, and the signal of one of the amplifiers 180 and 182 is sent to the DC component voltmeter 188, the first lock-in amplifier 184, and the second lock-in. Input to the amplifier 186. The output of the DC component voltmeter 188 is input to the voltage controller 410, and a high voltage adjusted according to this input value is applied to the photoelectron amplifier 162, and the light intensity level detected by the DC component voltmeter 188 is changed. Feedback control is performed so as to be substantially constant.
In addition to the above, the computer 192 adjusts the current applied to the electromagnet 172 via the magnetic field controller 409 or controls the photoelastic modulator 152 via the modulation controller 408.
[0033]
The above-described control system using the computer 192 is merely an example for controlling the measurement apparatus. Various controls based on the information (see FIG. 2) regarding the assembly of the main components (that is, various optical instruments) and the arrangement between the components for measuring the optical-magnetic effect described in this specification and the accompanying drawings. Building a system is merely a design matter of a person skilled in the art, and does not depart from the present invention.
[0034]
Hereinafter, the measurement processing procedure in the present measurement apparatus will be described in more detail with reference to FIGS. 9 to 22.
FIG. 9 shows a procedure for selecting the lamps 102 and 108 to be used according to the wavelength to be measured. The lamps 102 and 108 to be used are selected when the wavelength to be measured is 300 nm or less. Specifically, the light source taken into the spectroscope 120 is switched by switching the switching mirror 123 with a motor 123m. When the wavelength is 300 nm or less, the deuterium lamp 102 is used (S74 or S75), and when the wavelength is 300 nm or more, the xenon lamp 108 is used (S72 or S73).
[0035]
FIG. 10 shows a processing procedure for selecting and adjusting the angle of the diffraction gratings 130, 132, 134. The diffraction grating 130 is used when measuring at a wavelength of 400 nm or less (S82), and diffraction is performed when measuring at a wavelength of 400 nm to 800 nm. The grating 132 is used (S84), and the diffraction grating 134 is used when measuring at a wavelength of 800 nm or more. In the figure, S86 represents a step of finely adjusting the angle of the selected diffraction grating, and thereby the wavelength to be measured is determined.
[0036]
FIG. 11 shows a control procedure of the filter 144. When the measurement wavelength is 250 nm or less, the through hole 144a is used. When the spectroscope 120 is used in the state of extracting light with a wavelength of 250 nm or less, the second or higher order diffracted light that can be extracted simultaneously becomes light with a wavelength of 125 nm or less. This is because the strength is extremely low even if the filter is used, and it is not necessary to cut with a filter. When measuring with light of 250 nm to 400 nm, high-order diffracted light is removed using a band pass filter 144 b that passes only light with a wavelength of 250 to 500 nm. When measuring with light having a wavelength of 400 to 610 nm, high-order diffracted light is cut by using a filter 144c that cuts light with a wavelength of 320 nm or less. Hereinafter, the high-order diffracted light is cut by properly using the filters 144d to 144f according to the conditions of FIG.
[0037]
FIG. 12 shows the switching procedure on the photodetector side, and the photoelectron amplifier 162 is used when the measurement wavelength is 830 nm or less. At this time, the concave reflecting mirror 158 is switched by the motor 158m, and the switch 183 is further switched. When the photoelectron amplifier 162 is used, the output of the DC component voltmeter 188 is monitored. If it is too low (S107), the voltage applied to the photoelectron amplifier 162 is increased to increase the gain (S108), and if it is too high (S109). ) Reduce the gain by decreasing the applied voltage (S110). At this time, the increase or decrease of the voltage is proportional to the difference from the reference voltage so as to be feedback-controlled quickly. In addition, a hysteresis characteristic is provided between the voltage increasing process and the decreasing process to prevent repeated overshoot of feedback control.
On the other hand, when using at a wavelength of 830 nm or more, the germanium diode 160 is used (S104; the reflecting mirror 158 and the switch 183 are also switched at this time), and the voltage applied to the photoelectron amplifier 162 is set to zero (S105).
[0038]
FIG. 13 shows the entire processing procedure in the measurement preparation stage, and details of S113 to S117 are as described in FIGS. S118 represents a process of adjusting the voltage applied to the photoelastic modulator (modulator) 152 in accordance with the wavelength used for measurement. For example, the case where the measurement wavelengths are 300 nm and 600 nm will be described as an example. When each wave is modulated by π / 2, in order to modulate 600 nm by π / 2 as compared with the case where 300 nm is modulated by π / 2. Need to be modulated more strongly and shifted by a larger distance. In step S118, the voltage applied to the photoelastic modulator is adjusted in accordance with the measurement wavelength, and the light is modulated weakly for short-wavelength light, but strongly modulated for long-wavelength light. Keep constant regardless of wavelength. In this example, the phase difference is adjusted to be slightly smaller than π regardless of the wavelength. This phase difference is a phase difference at which simultaneous measurement of the optical rotation angle (more precisely, the optical-magnetic effect rotation angle) and the ellipticity is accurately performed.
[0039]
14 and 15 show the state of the calibration process for this measuring apparatus. In the case of this measuring apparatus, it has been confirmed that the coefficient for calibration has no wavelength dependence, and the user using this can select and calibrate by selecting an appropriate wavelength (S121). However, it is more reliable to calibrate at a wavelength equal to the wavelength of the measurement light.
[0040]
In FIG. 14, during the calibration process, first, the second polarizer 156 (that is, the analyzer 156) is rotated from zero to minus 2 degrees from the device side (S122), and the direct current component VDC, the modulation frequency component VF, and the double frequency component thereof. V2F is detected. Thereafter, the analyzer 156 is rotated by +1 degree (S125), the same process is continued, and this process is continued until it reaches +2 degrees (S124). As a result, a total of five measurements are performed. As schematically shown in FIG. 15, the computer 192 divides the angle X (−2, −1, 0, +1, +2) of the analyzer 156 and V 2 F / VDC (ie, doubles the frequency component by the DC component). And the relationship established between this value and Y) is analyzed. The processing contents of this analysis are schematically shown. A regression line is drawn on the XY axis graph by the least square method, the calibration coefficient A is obtained from the slope of this regression line, and zero from the value of A where Y = O. Find the angle.
The above processing is performed by the computer 192 (step S126 in FIG. 14). After the above processing, the analyzer 156 is rotated to zero angle (S127), set to a wavelength for measurement (S128), and prepared for actual measurement. The zero degree on the apparatus side in FIG. 14 is a design zero degree that should not pass the white wave through the black wave in FIG. 4, and the zero angle obtained in step S126 is the actually calibrated zero angle. .
[0041]
FIG. 16 shows a measurement procedure in a magnetic field having a certain wavelength. In this case, after the stabilization time of the amplifier or the like has elapsed, the DC component VDC, the modulation frequency component VF, the doubled frequency component V2F, and the magnetic field are measured (S141 to S144), and each value is temporarily stored in the computer 192 (S145). ˜S147), and the optical rotation angle (θ; light-magnetooptic effect rotation angle) and ellipticity (ε) are obtained from the measured values. The calculation formula is shown in step S148 in FIG. Here, J1 and J2 indicate the first order and second order of the Bessel function, and δ is the phase delay due to the photoelastic modulator. As described above, δ is adjusted to 0.383 × 2π radians regardless of the measurement wavelength (this is a value slightly smaller than π).
FIG. 17 shows the procedure for measuring only the optical rotation angle (θ), and FIG. 18 shows the procedure for measuring only the ellipticity (ε).
[0042]
FIG. 19 shows a procedure diagram for measuring the hysteresis characteristic of the sample with respect to the magnetic field by changing the magnetic field from “zero → plus maximum value → zero → minus maximum value → zero”. The direction and intensity of the magnetic field are determined in advance with respect to the number of measurements, and the above-described magnetic field change pattern is obtained. First, the calibration process shown in FIGS. 14 and 15 is performed at the start of measurement (S171). Next, the magnetic field is changed according to a predetermined order (S173). When the one-step measurement is finished, step S172 becomes no and the measurement is finished. At this time, the magnetic field is set to zero (S176), and the voltage applied to the photoelectron amplifier tube 162 is set to zero (S177). During the execution of the sequential measurement, the measurement is continued (S175) while changing the magnetic field (S173).
[0043]
FIG. 20 shows a processing procedure for measuring the wavelength dependence. In this measurement, the photo-magnetic effect when the sample is saturated with respect to the magnetic field is examined. For this purpose, the sample 176 is measured by adding a positive maximum magnetic field and a negative maximum magnetic field, and the saturation characteristic is examined from the difference between the measured values. In step S181, calibration processing is performed. In step S182, the wavelength at the start of measurement is set. In this state, a positive maximum magnetic field is applied (S183). A series of measurements are continued while changing the wavelength, and when measurement at the final wavelength is performed, step S184 becomes NO. At this time, the measurement is finished (S190, S191). During measurement, after measuring with the maximum positive magnetic field (S185), the direction of the magnetic field is reversed, and then the maximum negative magnetic field is applied (S186) and measurement is performed (S187).
After the above processing, the difference between the two is taken and divided by 2 (S188), and the optical rotation angle θ and the ellipticity ε at the time of saturation are calculated. This is performed for all wavelengths while changing the wavelength (S189).
When measuring at the next wavelength, measurement is first performed while applying a negative magnetic field, and then measurement is performed by reversing the magnetic field and applying a positive magnetic field (S185, S186, S187). Thus, for each wavelength, measurement is performed while alternately changing the magnetic field as “+ → −” and “− → +”. Wavelength dependence is measured by completing a series of measurements for all wavelengths.
[0044]
FIG. 21 illustrates an improved wavelength dependent process. In this processing procedure, calibration processing is performed for each wavelength. For this purpose, the analyzer is measured at +2 degrees (S194, S195), and then the analyzer 156 is measured at 0 degrees (S196, S197). As a result, a calibration straight line as shown in FIG. 21B is obtained, and a calibration coefficient at that wavelength is calculated therefrom. In this example, the measurement of the photo-magneto-optical effect is performed with the analyzer 156 at +2 degrees (S194 and S195) (S199 and 200). That is, it does not measure at zero angle. However, since the difference between the positive magnetic field and the negative magnetic field is obtained in step S201, the influence of the deviation from the zero angle is canceled out, and good measurement is performed.
[0045]
FIG. 22 shows another example in which the same improvement as in FIG. 21 is performed, and the analyzer 156 is used at either +2 degrees or −2 degrees. In this improved example, calibration is performed by applying a positive magnetic field at a certain wavelength (FIG. 22B), and calibration is performed by applying a negative magnetic field at the next wavelength (FIG. 22C). In this way, the number of magnetic field reversals required for calibration is minimized, and the measurement time is significantly shortened.
In the above-described embodiment, the case where the present invention is applied to a measurement device using a circularly polarized wave is shown. However, the present invention can also be applied to a measurement device using a cross-Nicol method, a Faraday cell method, or a rotating analyzer method. . Moreover, in the said embodiment, although the process procedure was mainly demonstrated about the case where a Kerr effect is measured, the same procedure can be applied also when measuring a Faraday effect.
[0046]
As described above, the preferred embodiment as the first device of the present invention has been described. However, according to the measurement device according to the present embodiment, the short wavelength light having a wavelength of 200 nm or less emitted from the deuterium lamp 102 is routed. Any of the above-described components can be accommodated in the sealable containers 106, 142, 166, 170, 178 and the containers 106, 142, 166, 170, 178 can be evacuated. Therefore, an optical path (see FIG. 5) from the deuterium lamp 102 to the photodetectors (160, 160a, 162, 162a) is secured in the sealed space in the containers 106, 142, 166, 170, 178, and Short wavelength light having a wavelength of 200 nm or less in the optical path is not attenuated by the atmosphere. That is, in the general atmosphere, vacuum ultraviolet light having a wavelength of 200 nm or less is absorbed by oxygen and vacuum ultraviolet light having a wavelength of 145 nm or less is absorbed by nitrogen. In this measuring apparatus, such absorption by gas molecules is a practical problem. It can be suppressed to a level that is not possible. Therefore, according to the first apparatus of the present invention, it is possible to realize the measurement of the photo-magneto-optic effect (Faraday effect and / or Kerr effect) with short wavelength light having a wavelength of 200 nm or less based on the above processing procedure. .
[0047]
Next, as a second embodiment of the present invention, a Kerr effect measuring apparatus suitable as the second apparatus of the present invention will be described with reference to FIG. FIG. 23 is a plan view schematically showing the measuring apparatus according to this embodiment.
[0048]
As shown in FIG. 23, the measurement apparatus according to the present embodiment is similar to the measurement apparatus according to the first embodiment described above. The light source unit 201 includes a deuterium lamp 202 and a xenon lamp 208 as light sources, and the light source unit. A spectroscope 220 for extracting light having a desired wavelength while dispersing light emitted from 201, a sample holder 274 for storing the sample 276, and an electromagnet 272 corresponding to means for applying a magnetic field to the sample 276. The electromagnet unit 269 and the optical system box 265 are main components, which are arranged on the surface plate 200. The optical system box 265 receives the reflected light from the first polarizer, the photoelastic modulator, and the sample 276 for polarizing the light extracted from the spectroscope 220, as in the first embodiment. A second polarizer that passes through, a germanium diode that detects the intensity of light that has passed through the second polarizer, and a photodetector (none of which is shown) having an optical path switching reflector in a photoelectron amplifier tube are accommodated ing.
[0049]
Thus, as in the first embodiment, the light source unit 201 (deuterium lamp 202 system) excluding the xenon lamp 208 and the reflecting mirrors 210 and 212 associated therewith, the spectroscope 220, the optical system box 265, and the electromagnet 272 ( That is, the sample holding portion is accommodated in containers 206, 242, 266, and 270 that can be sealed. As a result, also in the measurement apparatus according to the present embodiment, the optical path of short-wavelength light having a wavelength of 200 nm or less from the light source unit 201 to the photodetector is blocked from the outside air and accommodated in the sealed containers 206, 242, 266, and 270. Is done.
In addition, as in the first embodiment, one end of a container 206 that houses the light source unit 201 and a container 266 that houses the optical system box 265 is provided with an electromagnetic valve or the like corresponding to the exhaust unit in the present embodiment. Exhaust pipes 214 and 215 having control valves 213 and 216 are provided.
[0050]
By the way, in the measuring apparatus according to the present embodiment, the container 206 for storing the light source unit 201, the container 242 for storing the spectroscope 220, and the container 266 for storing the optical system box 265 are in a state of being able to ventilate each other and shielded from the outside air. On the other hand, as shown in FIG. 23, the optical path from the first polarizer to the sample 276 and the optical path from the sample 276 to the second polarizer, that is, the electromagnet portion 269 are connected. Between the container 270 for accommodating the optical system box 265 and the container 266 for accommodating the optical system 265, it is possible to transmit short wavelength light having a wavelength of 200 nm or less by the vacuum ultraviolet light transmitting member 211 preferably made of lithium fluoride or magnesium fluoride. However, they are separated from each other in an incapable state.
Further, a vent 218 having an electromagnetic valve 217 is provided at one end of the container 270 that houses the electromagnet portion, independently of the exhaust unit, and a desired gas (typically, typically in the container 270). Can be replaced by nitrogen gas).
[0051]
As a result of the above configuration, in the measuring apparatus according to the present embodiment, the light source unit 201 storage container 206, the spectroscope 220 storage container 242 and the optical system are performed by performing exhaust processing through the exhaust pipes 214 and 215. While the box 265 storage container 266 is in a vacuum state, the optical path of the short wavelength light in the containers 206, 242, 266 is placed under vacuum, while the electromagnet part 269 storage container 270 is connected to the inside and outside through the ventilation port 218. The gas inside the container 270 can be replaced with a gas not containing oxygen (for example, nitrogen gas) without causing a pressure difference.
Therefore, according to the measuring apparatus according to the present embodiment, the sample holder 275 can be kept under the same atmospheric pressure as the outside air, and the sample holder 274 and the sample 276 can be easily replaced in the sample holder 275. Further, since the electromagnet portion 269 including the sample holding portion 275 is not decompressed even when measuring the magneto-optical effect, the auxiliary means such as the above-described O-ring 171 is used for the sample 276 or the sample holder 274 having various shapes and properties. Therefore, the sample can be stably held in the sample holder 275, and measurement can be performed with good reproducibility.
In the measuring apparatus according to the present embodiment, most of the optical path is placed under vacuum, and the normal pressure portion (that is, the vicinity of the sample 276) does not contain oxygen that absorbs short-wavelength light having a wavelength of 200 nm or less. Since it can be replaced with nitrogen gas or the like, the attenuation of short wavelength light with a wavelength of 200 nm or less can be suppressed to a level that does not cause a practical problem. Therefore, according to the second apparatus of the present invention, the measurement of the photo-magneto-optic effect with a short wavelength light having a wavelength of 200 nm or less is realized based on the same procedure as the processing procedure described in the first embodiment. be able to.
[0052]
The preferred embodiments of the magneto-optical effect measuring apparatus of the present invention have been described above, but the present invention is not intended to be limited to those shown in the above embodiments.
For example, in each of the embodiments described above, the control valve and the exhaust pipe as the exhaust means are both provided in the container of the light source unit and the container of the optical system box. It can be suitably provided in the part which does not become. Further, by providing the measuring apparatus according to the second embodiment with the same Faraday effect measuring device (optical element) as disclosed in the first embodiment, the Kerr effect can be obtained based on the above processing procedure. It will be appreciated by those skilled in the art that the Faraday effect can be suitably measured as well.
Moreover, although the case where this invention was applied to the measuring apparatus by a circularly polarized modulated wave was shown in the said embodiment, it can also be applied to the measuring apparatus by a cross-Nicol method, a Faraday cell method, and a rotation analyzer method.
[0053]
【The invention's effect】
According to the present invention, it is possible to measure the magneto-optic effect with short wavelength light having a wavelength of 200 nm or less with a simple apparatus configuration. That is, in the present invention, an optical element that can absorb a short-wavelength light having a wavelength of not more than 200 nm, such as oxygen, can be eliminated from the optical path of the short-wavelength light having a wavelength of not more than 200 nm from the light source part to the photodetector, and further used. However, short-wavelength light having a wavelength of 200 nm or less is not strongly attenuated, so that the photo-magneto-optic effect at a wavelength of 200 nm or less can be measured. The photo-magneto-optical effect measuring apparatus of the present invention greatly contributes to the progress of ultra-high density storage technology that is expected to become important in the future.
[Brief description of the drawings]
FIG. 1 is a plan view schematically showing an outline of a measurement apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a planar layout of the measurement apparatus of the present invention according to one embodiment.
FIG. 3 is a diagram showing details of a spectroscope and a filter.
FIG. 4 is a diagram schematically showing a measurement principle.
FIG. 5 is a diagram showing an optical path as a center.
FIG. 6 is an electrical system diagram of the measurement apparatus of the present invention according to one embodiment.
FIG. 7 is a diagram schematically showing an electrical system of the measuring apparatus according to the embodiment of the present invention.
FIG. 8 is a diagram showing an irradiation optical system.
FIG. 9 is a diagram illustrating a procedure for selecting a lamp.
FIG. 10 is a diagram showing a procedure for selecting a diffraction grating and adjusting an angle.
FIG. 11 is a selection procedure diagram of a filter.
FIG. 12 is a selection procedure diagram of a detection apparatus.
FIG. 13 is an overall processing procedure diagram of a measurement preparation procedure.
FIG. 14 is a calibration processing procedure diagram.
FIG. 15 is a diagram showing the contents of calibration.
FIG. 16 is an actual procedure diagram at the time of measurement.
FIG. 17 is a measurement procedure diagram of a light-magnetic effect rotation angle (optical rotation angle).
FIG. 18 is a measurement procedure diagram of ellipticity.
FIG. 19 is a measurement procedure diagram of hysteresis characteristics.
FIG. 20 is a measurement procedure diagram of wavelength dependence (part 1);
FIG. 21 is a measurement procedure diagram of wavelength dependence (part 2);
FIG. 22 is a measurement procedure diagram of wavelength dependence (part 3);
FIG. 23 is a plan view schematically showing the measurement apparatus of the present invention according to one embodiment.
[Explanation of symbols]
101, 201 Light source unit
102,202 Deuterium lamp
106, 142, 166, 170, 178, 206, 242, 266, 270 containers
108,208 Xenon lamp
113, 116, 213, 216 Valve
114, 115, 214, 215 Exhaust pipe
120,220 Spectrometer
130, 132, 134 diffraction grating
150 First polarizer
152 Photoelastic Modulator
156, 156a Second polarizer
160, 160a germanium diode
162, 162a Photoelectric amplifier tubes
165, 265 Optical box
169, 269 Electromagnet part
172,272 Electromagnet
175,275 Sample holder
174,274 Sample holder
176,276 samples
211 Vacuum ultraviolet light transmitting member
218 Ventilation opening

Claims (1)

A light source unit, a spectroscope that separates light from the light source unit and extracts light of a necessary wavelength, a first polarizer that polarizes light extracted by the spectroscope, and a magnetic field is applied to the sample A sample holding unit provided with means, and a second light that passes through the sample irradiated from the first polarizer to the sample mounted on the sample holding unit or the light reflected by the sample. And a photo-magneto-optic effect measurement apparatus comprising: a polarizer; and a photodetector that detects the intensity of light that has passed through the second polarizer.
The light source unit is configured to emit short wavelength light having a wavelength of 200 nm or less,
The optical path of the short wavelength light from the light source part to the photodetector is housed in a container that can be sealed together with the sample holder,
The container is capable of transmitting the short-wavelength light and mutually incapable of gas flow between a container including a sample holder and a container including an optical system including a first polarizer and a second polarizer. With a vacuum ultraviolet light transmitting member separated by
Here, the container including the sample holder is provided with a vent for opening and closing the gas in the container so as to be openable and closable, and the optical system includes the first polarizer and the second polarizer. The container containing the system is provided with an exhaust means for discharging the gas in the container,
In measuring the magneto-optical effect, a container including the optical system including the first polarizer and the second polarizer is used while the container including the sample holder is replaced with a gas not containing oxygen. A photo-magneto-optic effect measuring apparatus characterized in that the inside is made into a vacuum state.

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