JP2004191302A - Terahertz spectral device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable reflection spectrum measurement and transmission spectrum measurement, using a terahertz light with a single spectral device. <P>SOLUTION: A reflection measurement optical system for irradiating a sample S (a location A) with terahertz pulse light and detecting a reflection light reflected from the sample and a transmission measurement optical system for irradiating the sample S (a location B) with the terahertz pulse light and detecting a transmission light transmitted through the sample can be switched. A detected light, as the reflection light or the transmission light, is measured by a time-series conversion terahertz spectrum. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a time-series conversion terahertz spectroscopy device using terahertz pulse light.
[0002]
[Prior art]
In a conventional time-series conversion terahertz spectrometer, a pulse light from a laser light source is split into two, one of which is guided to a terahertz light generating element as pump light, and the other is guided to a detector as probe light. Terahertz pulse light generated from the terahertz light generating element is incident on the sample, and light emitted from the sample is incident on a detector (a terahertz light detecting element) as detection light. An optical system is used both when the terahertz pulse light is incident on the sample and when the light emitted from the sample is guided to the detector. Depending on what characteristics of the sample you want to know, there are cases where the reflection spectrum is measured by detecting the reflected light reflected on the sample surface, and cases where the transmission spectrum is measured by detecting the transmitted light transmitted through the sample .
[0003]
[Problems to be solved by the invention]
The positional relationship between the sample and the optical system differs between the case where the reflection spectrum is measured and the case where the transmission spectrum is measured, and the optical system also differs. Conventionally, dedicated spectroscopes have been used, respectively, but installing two spectroscopes required a large amount of cost and a large space.
[0004]
The present invention provides a terahertz spectrometer capable of both reflection spectrum measurement and transmission spectrum measurement.
[0005]
[Means for Solving the Problems]
INDUSTRIAL APPLICABILITY The present invention is applied to a terahertz spectrometer having a detection optical system for irradiating a sample with terahertz pulsed light and detecting light from the sample, and measuring the detection light by time-series conversion terahertz spectroscopy. The present invention has the following features. The detection optical system irradiates the sample with terahertz pulsed light and guides the reflected light reflected from the sample to the terahertz light detection unit, and the transmitted light that irradiates the sample with terahertz pulsed light and transmits through the sample And a switching mechanism for selectively switching between the reflection measurement optical system and the transmission measurement optical system. Further, the optical path length of the terahertz light is made equal in both the case where the reflection measurement optical system is selected by the switching mechanism and the case where the transmission type measurement optical system is selected.
The reflection measurement optical system and the transmission measurement optical system share at least a pair of plane mirrors for converting the optical path, and switch the reflection measurement optical system and the transmission measurement optical system by changing the attitude of the pair of plane mirrors by a switching mechanism. Is preferable. In this case, the switching mechanism can be composed of a pair of connecting shafts that respectively drive the pair of plane mirrors, and a drive system that rotates the pair of driving shafts in synchronization. Further, in both cases when the reflection measuring optical system is selected by the switching mechanism and when the transmission measuring optical system is selected, the pair of connection axes are connected to the light of the terahertz pulse light so that the optical path length of the terahertz pulse light becomes equal. It is inclined at a predetermined angle with respect to the axis.
Further, the drive system has a gear device for transmitting a rotational force to a pair of connecting shafts. The gear device has a predetermined amount of backlash, and eccentrically fixes the pair of connecting shafts from the center of gravity of the plane mirror. When the reflection measurement optical system is selected by the switching mechanism, the shared plane mirror abuts on the first stopper due to gravity to define the reflection measurement position, and when the transmission measurement optical system is selected, the shared plane mirror is It is preferable that the reflection measurement position is defined by contacting the second stopper.
In such a terahertz spectrometer, a detection unit that detects a sample set at a position for reflection measurement or a position for transmission measurement, and a switching mechanism that is driven and controlled based on a detection result by the detection unit, are connected to the reflection measurement optical system and the transmission system. And a control device for switching between the measurement optical system and the measurement optical system.
The reflection measurement optical system and the transmission measurement optical system are preferably housed in a closed container except for at least the sample.
The switching mechanism may be configured as follows. A reflection measurement optical system unit accommodating a part of the reflection measurement optical system, a transmission measurement optical system unit accommodating a part of the transmission measurement optical system, and an attachment / detachment mechanism for selectively attaching or detaching these units to / from the apparatus main body. including.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a terahertz spectrometer according to the present invention will be described with reference to the drawings.
[0007]
This terahertz spectrometer simply switches the optical system with one device, detects reflected light reflected on the sample surface and measures the reflected spectrum, or detects transmitted light transmitted through the sample and changes the transmitted spectrum. It can also be measured. The optical path length from the terahertz light generating element 5 to the terahertz pulsed light detecting element 12 is configured to be substantially equal in both the case of the reflection spectrum measurement and the case of the transmission spectrum measurement.
[0008]
FIG. 1 and FIG. 2 are schematic configuration diagrams schematically showing a terahertz spectroscopic device according to an embodiment. FIG. 1 is an apparatus configuration diagram in the case of reflection spectrum measurement, and FIG. 2 is an apparatus configuration diagram in the case of transmission spectrum measurement. Originally, these two configuration diagrams should be shown together as one, but they are shown separately in two to avoid complicating the drawings.
[0009]
In the configuration diagram of FIG. 1, a plane parallel to the plane of the paper is an XY plane, and a direction perpendicular to the plane of the paper is a Z axis. However, for convenience of drawing, only the area surrounded by the dashed line is defined as a plane parallel to the plane of the paper as the XZ plane and a direction perpendicular to the plane of the paper as the Y axis. That is, a state in which side views (areas surrounded by alternate long and short dash lines) are mixed in the plan view is shown.
[0010]
In FIG. 1, a pulse light L1 emitted from a laser light source 1 is split by a beam splitter 2 into two pulse lights L2 and L3. As the laser light source 1, for example, a femtosecond pulse laser is used. The pulse light L1 is linearly polarized pulse light having a center wavelength of about 780 to 800 nm in the near infrared region, a repetition period on the order of several kHz to 100 MHz, and a pulse width of about 10 to 150 fs.
[0011]
One of the pulse lights L2 split by the beam splitter 2 becomes pump light (excitation light) for exciting the terahertz light generation element 5 to generate terahertz pulse light. This pump light L <b> 2 is guided to the terahertz light generation element 5 via the plane reflecting mirror 3 and the condenser lens 4. As a result, the terahertz light generating element 5 is excited to emit the terahertz pulse light L4. The terahertz pulse light L4 is light in a frequency range from approximately 0.01 × 10 ¹² to 100 × 10 ¹² Hertz. The terahertz pulse light L4 reaches the plane mirror 8 via the curved mirrors 6 and 7. As the curved mirrors 6 and 7, for example, a parabolic mirror or an elliptical mirror is used.
[0012]
Here, since the plane mirror 8 is located in an area surrounded by a dashed line, its reflection surface is a plane perpendicular to the XZ plane, and reflects light incident on the plane mirror 8 upward (in the + Z direction). Therefore, the terahertz pulse light L4 travels upward and enters the lower surface of the sample S.
[0013]
The terahertz pulse light L5 reflected on the surface of the sample S is light including information on characteristics of the sample S. The terahertz pulse light L5 travels downward (−Z direction), and enters the terahertz light detection element 12 through the plane mirror 9, the curved mirrors 10, 11, and the like. Since the plane mirror 9 is located in the area surrounded by the dashed line, its reflection surface is a surface perpendicular to the XZ plane.
[0014]
When the terahertz pulse light L5 is incident on the terahertz light detection element 12, an electric field is generated. When this part is irradiated with the probe light L3, a photocurrent according to the electric field strength flows, and by measuring this, the electrical characteristics and impurity concentration of the sample can be obtained. The probe light L3 enters the terahertz light detection element 12 as follows.
[0015]
The other pulse light L3 split by the beam splitter 2 becomes probe light for detecting the terahertz pulse light L5. The pulse light L3 (probe light L3) is incident on the terahertz light detection element 12 via the optical system 14, which is a combination of a movable movable mirror 14a and a fixed plane reflecting mirror 14b, and plane reflecting mirrors 15, 16. The optical system 14 changes the optical path length of the probe light L3 according to the amount of movement of the movable mirror 14a by moving the movable mirror 14a formed by combining two plane reflecting mirrors as shown by the arrow in the figure. As a result, the time for the probe light L3 to reach the terahertz light detection element 12 via the condenser lens 15 is delayed. Then, by observing the light detected by the terahertz light detection element 12 while changing the delay time by the movable mirror 14a, time-series terahertz spectroscopy becomes possible. The reflection measurement optical system 100 is an area surrounded by a broken line.
[0016]
As described above, the terahertz pulse light detecting element 12 detects a photocurrent proportional to the electric field intensity of the received terahertz pulse light, and sends the detected photocurrent to a control / calculation device (not shown). Then, the control / arithmetic unit performs a time series conversion on the detection signal, and executes an arithmetic operation according to a desired characteristic of the sample. The obtained data is displayed on a display unit such as a liquid crystal display or a CRT.
[0017]
Next, an apparatus configuration diagram in the case of transmission spectrum measurement will be described. In the configuration diagram of FIG. 2, a plane parallel to the plane of the paper is an XY plane, and a direction perpendicular to the plane of the paper is a Z-axis. In FIG. 2, the same or corresponding elements as those in FIG. 1 are denoted by the same reference numerals.
[0018]
In FIG. 2, a pulse light L1 emitted from a laser light source 1 is split by a beam splitter 2 into two pulse lights L2 and L3. One of the pulse lights L2 split by the beam splitter 2 becomes pump light (excitation light) for exciting the terahertz light generation element 5 to generate terahertz pulse light. The pump light L2 is guided to the terahertz light generation element 5 via the plane reflecting mirror 3 and the condenser lens 4. The terahertz pulse light L4 reaches the plane mirror 8 via the curved mirrors 6 and 7. The optical path up to this point is the same as in FIG. The reflecting surface of the plane mirror 8 is perpendicular to the XY plane, which is different from the state shown in FIG. The incident light is reflected in the −Y direction by the reflecting surface of the plane mirror 8.
[0019]
In FIG. 2, the terahertz pulse light L4 reflected by the plane mirror 8 is further bent in the optical path by the plane mirror 18 and enters the sample S. The optical path of the terahertz pulse light L5 transmitted through the sample S is bent by the plane mirror 19 and enters the plane mirror 9. The reflecting surface of the plane mirror 9 is perpendicular to the XY plane, which is different from the state shown in FIG. The terahertz pulse light L5 reflected by the plane mirror 9 enters the terahertz light detection element 12 through the same optical path as in FIG. 1, that is, through the curved mirrors 10 and 11.
[0020]
The optical path on which the other pulsed light L3 split by the beam splitter 2 enters the terahertz light detection element 12 is the same as that in FIG. The transmission measurement optical system 200 is an area surrounded by a broken line.
[0021]
The optical path from the plane mirror 8 to the plane mirror 9 and the optical system are different from the case of the reflection spectrum measurement of FIG. 1 and the case of the transmission spectrum measurement of FIG. Other configurations are the same. In other words, the optical system 100H surrounded by the dashed line in FIG. 1 is different from the optical system 200T surrounded by the dashed line in FIG.
[0022]
FIG. 3 is a perspective view showing the appearance of the terahertz spectroscopy device according to the embodiment of the present invention. In the case of reflection spectrum measurement, the sample S is placed horizontally on the upper surface (position A) of the container 20, and in the case of transmission spectrum measurement, the sample S is placed vertically in the sample holder (position B) on the near side of the container 20. Is done. When the cover 21 is opened, it can be seen that the sample S is placed between the plane mirrors 18 and 19.
[0023]
In the terahertz spectrometer according to the present embodiment, the reflection measurement optical system and the transmission measurement optical system are housed in the closed container 20 except for the sample S and its peripheral part. The inside of the container 20 may be kept in a vacuum or filled with a predetermined gas. With this configuration, it is possible to prevent dust and moisture in the air from adversely affecting the optical system while maintaining the ease of sample replacement.
[0024]
Next, a mechanism for switching between two different optical systems, a reflection measurement optical system and a transmission measurement optical system, will be described.
[0025]
In the case of the reflection spectrum measurement in FIG. 1, the plane mirror 8 reflects the terahertz pulse light L4 in the + Z direction, and the terahertz pulse light L5 traveling from the sample S in the −Z direction enters the plane mirror 9. At this time, if the optical path length of the optical axis from the plane mirror 8 to the sample S is r1, and the optical path length of the optical axis from the sample S to the plane mirror 9 is r2, the optical path length of the optical axis from the plane mirror 8 to the plane mirror 9 is ( r1 + r2).
[0026]
On the other hand, in the case of the transmission spectrum measurement of FIG. 2, the plane mirror 8 reflects the terahertz pulse light L4 in the −Y direction, and the plane mirror 18 reflects the reflected light from the plane mirror 8 toward the sample S. The transmitted light transmitted through the sample S is reflected by the plane mirror 19, and the terahertz pulse light L5 traveling in the + Y direction from the plane mirror 19 is incident on the plane mirror 9. At this time, if the optical path length of the optical axis from the plane mirror 8 to the plane mirror 18 is t1, the optical path length of the optical axis from the plane mirror 18 to the plane mirror 19 is t2, and the optical path length of the optical axis from the plane mirror 19 to the plane mirror 9 is t3, The optical path length of the optical axis from the plane mirror 8 to the plane mirror 9 is (t1 + t2 + t3).
[0027]
In order to be able to use two different optical systems for reflection spectrum measurement and transmission spectrum measurement by switching, the optical path length from the plane mirror 8 to the plane mirror 9 needs to be substantially equal. That is, it is necessary to set r1 + r2 ≒ t1 + t2 + t3. Further, it is necessary to make the optical path length of the pulse light L3 substantially equal to the sum of the optical path lengths of the pulse light L2, the terahertz pulse light L4, and the terahertz pulse light L5. With this configuration, the reflection measurement optical system and the transmission measurement optical system can be switched and used.
[0028]
Note that the object of the present invention can be achieved by changing the optical path length of the pulsed light L3 without making the optical path lengths from the plane mirror 8 to the plane mirror 9 substantially equal. That is, the amount of movement of the movable mirror 14a may be adjusted to change the optical path length of the pulsed light L3 so as to be substantially equal to the sum of the optical path lengths of the pulsed light L2, the terahertz pulsed light L4, and the terahertz pulsed light L5. However, using such an adjustment method requires a stage having a long moving distance, which leads to an increase in the size of the apparatus.
[0029]
In the present embodiment, the plane mirror 8 and the plane mirror 9 are rotated so that r1 + r2 ≒ t1 + t2 + t3. A stage with a short stroke length can be adopted.
[0030]
FIG. 4 is a partial perspective view showing the plane mirror and the rotation mechanism. In FIG. 4, two different optical systems for reflection spectrum measurement and transmission spectrum measurement are represented on one drawing. The optical path is represented only by the optical axis for simplicity.
[0031]
The rotational position of the plane mirror 8 and the plane mirror 9 for the reflection spectrum measurement is indicated by a position R, and the rotational position of the plane mirror 8 and the plane mirror 9 for the transmission spectrum measurement is indicated by a position T. The position of the sample S in the case of the reflection spectrum measurement is indicated by a position A, and the position of the sample S in the case of the transmission spectrum measurement is indicated by a position B. In the following description, these are indicated by 8R, 9R, 8T, 9T, SA, and SB for convenience.
[0032]
In the case of the reflection spectrum measurement, the terahertz pulse light L4 proceeds in the order of the plane mirror 8R (position R), the sample SA (position A), and the plane mirror 9R (position R), and travels to the curved mirror 10 as the terahertz pulse light L5. On the other hand, in the case of transmission spectrum measurement, the terahertz pulse light L4 travels in the order of the plane mirror 8T (position T), the plane mirror 18, the sample SB (position B), the plane mirror 19, and the plane mirror 9T (position T), and becomes a terahertz pulse light L5. Head to mirror 10.
[0033]
Switching of the optical system, that is, rotation of the plane mirror 8 and the plane mirror 9 is performed by a rotation switching mechanism 30 including a rotating shaft 31, a plurality of bevel gears 32 to 35, and two connecting shafts 36 and 37. A main bevel gear 32 is attached to the rotating shaft 31. The main bevel gear 32 is engaged with bevel gears 33 and 34, and the bevel gear 34 is engaged with a bevel gear 35. One end of the connecting shaft 36 is fixed at a position eccentric by a predetermined distance from the center of gravity of the rear surface of the plane mirror 8, and a bevel gear 33 is fixed to the other end of the connecting shaft 36. One end of the connecting shaft 37 is fixed at a position eccentric from the center of gravity of the rear surface of the plane mirror 9 by a predetermined distance, and a bevel gear 35 is fixed to the other end of the connecting shaft 37.
[0034]
In the case of the reflection spectrum measurement, the plane mirror 8 and the plane mirror 9 are set at the position R by rotating the rotating shaft 31. At the position R, the plane mirror 8 and the plane mirror 9 are held and positioned by stoppers 38 and 39, respectively.
[0035]
In the present embodiment, assuming that the terahertz pulse light L4 traveling from the plane mirror 8 (position R) to the sample S (position A) is Lr1, the incident angle of Lr1 is set to 13 ° with respect to the Z axis on the XZ plane. You. For this purpose, the rotational position of the reflecting surface of the plane mirror 8 (position R) may be set so that the angle formed by the plane perpendicular to the XZ plane and the XY plane is 38.5 °. If the plane mirror 8 (position R) and the plane mirror 9 (position R) are arranged symmetrically with respect to the sample S (position A), the angle of the light Lr2 traveling from the sample S (position A) to the plane mirror 9 (position R) is also , With respect to the Z axis on the XZ plane.
[0036]
On the other hand, in the case of the transmission spectrum measurement, the plane mirror 8 and the plane mirror 9 are set at the position T by rotating the rotation shaft 31. At the position T, the plane mirror 8 and the plane mirror 9 are held and positioned by the stoppers 40 and 41.
[0037]
In the present embodiment, assuming that the terahertz pulse light L4 traveling from the plane mirror 8 (position T) to the plane mirror 18 is Lt1, the angle of Lt1 is set to 0 ° with respect to the Y axis on the XY plane. For this purpose, the rotational position of the reflecting surface of the plane mirror 8 (position T) may be set so that the angle between the reflecting surface perpendicular to the XY plane and the XZ plane is 45 °. Assuming that light traveling from the plane mirror 18 to the plane mirror 19 is Lt2, Lt2 is parallel to the X axis. If the plane mirror 8 (position T) and the plane mirror 9 (position T) are arranged symmetrically with respect to the sample S (position B), the angle of the light Lt3 traveling from the plane mirror 19 to the plane mirror 9 (position T) is also on the XY plane. 0 ° with respect to the Y axis.
[0038]
To set the angle of the light Lr1 at 13 ° with respect to the Z axis on the XZ plane and set the angle of the light Lt1 at 0 ° with respect to the Y axis on the XY plane, The connecting shaft 36 may be fixed to the rear surface of the plane mirror 8 so that the direction is 45 ° with respect to the reflection surface of the plane mirror 8 and 6.5 ° with respect to the XY plane. If the plane mirror 8 and the plane mirror 9 are arranged symmetrically with respect to the sample S, the connecting shaft 37 may be fixed to the rear surface of the plane mirror 9 at the same angle.
[0039]
As described above, the connection shafts 36 and 37 are fixed to the rear surfaces of the plane mirrors 8 and 9, respectively, at positions slightly away from the center (center of gravity) of the plane mirrors. That is, the fixed position is slightly shifted from the center of gravity of the plane mirror. The backlash (play) of the bevel gears 32 to 35 is increased. Thereby, when switching between the reflection spectrum measurement and the transmission spectrum measurement, the plane mirrors 8 and 9 are held by the stoppers 38 to 41 by the action of gravity, so that the reproducibility of positioning is improved.
[0040]
The above arrangement will be verified with reference to FIG. FIG. 5 is an optical path diagram showing the optical path length from the plane mirror 8 to the plane mirror 9 in the reflection spectrum measurement and the transmission spectrum measurement. The optical path is represented only by the optical axis for simplicity. The optical path for the measurement of the reflection spectrum and the optical path for the measurement of the transmission spectrum are shown on the same plane for easy comparison.
[0041]
The optical path of the reflection spectrum measurement is a line connecting the reflection point a of the plane mirror 8, the existing point b of the sample S, and the point of incidence c on the plane mirror 9. The optical path of the transmission spectrum measurement is a line connecting the reflection point a of the plane mirror 8, the reflection point d of the plane mirror 18, the existence point e of the sample S, the reflection point f of the plane mirror 19, and the point of incidence c on the plane mirror 9. The optical path lengths of the lights Lr1 and Lr2 are represented by r1 and r2, respectively, and the optical path lengths of the lights Lt1, Lt2 and Lt3 are represented by t1, t2 and t3, respectively.
[0042]
Since the angle formed by the line segment ab and the angle formed by the line segment ad are set to 13 ° and 0 ° with respect to the Z axis, the optical path length of the reflection spectrum measurement can be obtained by appropriately setting the position e of the sample S. (R1 + r2) and the optical path length (t1 + t2 + t3) of the transmission spectrum measurement can be made equal.
[0043]
As described above, if r1 + r2Ｚt1 + t2 + t3 can be satisfied, the reflection angle with respect to the Z axis and the length of each line segment are not limited to the present embodiment.
[0044]
The terahertz light measurement device according to the present invention includes a reflection measurement optical system that irradiates a sample with terahertz pulse light and detects reflected light reflected from the sample, and a transmitted light that irradiates the sample with terahertz pulse light and transmits the sample. The configuration is not limited to the embodiment as long as it has a transmission measurement optical system for detecting the transmission and a switching mechanism for switching between the reflection measurement optical system and the transmission measurement optical system.
[0045]
For example, the rotation mechanism for rotating the plane mirror 8 and the plane mirror 9 can be manually operated, but if operated automatically, the burden on the operator is reduced. In the case of the automatic operation, whether the sample S is set at the position of the reflection measurement or the position of the transmission measurement is detected by an optical sensor or the like, the signal is sent to the control device, and the control device operates the switching mechanism. What should I do? Although the plane mirrors 8 and 9 are rotated in conjunction with each other, they may be driven individually.
[0046]
Further, a large backlash is provided on the bevel gears 32 to 35, the rotating shafts 36 and 37 are fixed at positions eccentric from the centers of gravity of the plane mirrors 8 and 9, and the plane mirrors 8 and 9 are brought into contact with the stoppers 38 to 41 by gravity. Positioned. However, such a positioning mechanism is not an essential component of the present invention. The positions of the plane mirrors 8 and 9 may be electrically or magnetically detected and positioned.
[0047]
Alternatively, the optical system may be switched without sharing the plane mirrors 8 and 9. For example, the optical system including the plane mirrors 8 and 9 of the reflection measuring optical system, that is, the optical system within the dashed line in FIG. 1 and the optical system including the plane mirrors 8, 9, 18 and 19 of the transmission measuring optical system, that is, FIG. The optical systems within the two-dot chain line may be separately unitized, and the optical systems may be switched by exchanging the units. In this case, the plane mirrors 8 and 9 are not shared.
[0048]
More specifically, a reflection measurement optical system unit 100H that accommodates a part of the reflection measurement optical system 100, a transmission measurement optical system unit 200T that accommodates a part of the transmission measurement optical system 200, and one of these units is selected. What is necessary is just to provide the attachment / detachment mechanism 300a-300d and 301a-301d which are attached to and detached from the apparatus main body. That is, the device main body is provided with a concave portion 350 in which the units 100H and 200T are installed, and optical surfaces 302a and 302b of terahertz light are opened on a surface facing the concave portion 350. Rails 301a to 301d are provided on both sides of the openings of the optical paths 302a and 302b, and the units 100H and 200T are provided with grooves 301a to 301d to be fitted with the rails 300a to 300d. Optical paths 303a and 303b are opened between the grooves 301a to 301d. According to such a configuration, when measurement is performed by the reflection measurement optical system, the unit 200T is moved in the direction of the arrow to remove it from the apparatus main body, and the unit 100H is moved in the direction of the arrow to be mounted on the apparatus main body. On the other hand, when measuring with the transmission measurement optical system, the unit 100H is moved in the direction of the arrow to remove it from the apparatus main body, and the unit 200T is moved in the direction of the arrow to be mounted on the apparatus main body.
[0049]
【The invention's effect】
As described above, according to the present invention, reflection spectrum measurement and transmission spectrum measurement can be performed with one spectrometer. Even if the reflection measurement optical system and the transmission measurement optical system are switched, the optical path length of the terahertz light does not change, so that the mechanism and the processing circuit for the terahertz light measurement can be made exactly the same.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a terahertz spectroscopic device according to an embodiment of the present invention, in the case of measuring a reflection spectrum.
FIG. 2 is a schematic configuration diagram of a terahertz spectroscopic device according to an embodiment of the present invention, in the case of transmission spectrum measurement.
FIG. 3 is an external perspective view of the terahertz spectrometer according to the embodiment of the present invention.
FIG. 4 is a partial perspective view showing a plane mirror and a rotation mechanism according to the embodiment of the present invention.
FIG. 5 is an optical path diagram showing an optical path length of the optical system according to the embodiment of the present invention.
FIG. 6 is a diagram illustrating units of a reflection measurement optical system and a transmission measurement optical system according to an embodiment of the present invention.
[Explanation of symbols]
1: laser light source 5: terahertz light generating element 8, 9, 18, 19: plane mirror 12: terahertz light detecting element (detector)
30: rotation switching mechanism 100: reflection measurement optical system 200: transmission measurement optical system S: sample L1, L2, L3: pulse light L4, L5: terahertz pulse light

Claims (8)

A terahertz spectrometer that has a detection optical system that irradiates a sample with terahertz pulsed light and detects light from the sample, and measures detection light by time-series conversion terahertz spectroscopy.
The detection optical system includes:
A reflection measurement optical system that irradiates the sample with the terahertz pulse light and guides the reflected light reflected from the sample to a terahertz light detection unit,
A transmission measurement optical system that irradiates the sample with the terahertz pulse light and guides the transmitted light transmitted through the sample to a terahertz light detection unit;
A switching mechanism for selectively switching the reflection measurement optical system and the transmission measurement optical system,
A terahertz spectrometer, wherein the optical path length of terahertz light is equal in both cases when the reflection measurement optical system is selected by the switching mechanism and when the transmission type measurement optical system is selected. The terahertz spectrometer according to claim 1,
The reflection measurement optical system and the transmission measurement optical system share at least a pair of plane mirrors for converting an optical path, and change the posture of the pair of plane mirrors by the switching mechanism to change the positions of the reflection measurement optical system and the transmission measurement optical system. A terahertz spectroscopy device characterized by switching. The terahertz spectrometer according to claim 2,
The switching mechanism includes a pair of connecting shafts that respectively drive the pair of plane mirrors, and a driving system that rotates the pair of driving shafts in synchronization with each other. The terahertz spectrometer according to claim 3,
The pair of connection axes are connected to the terahertz pulse so that the optical path lengths of the terahertz pulsed light are equal in both the case where the reflection measurement optical system is selected and the case where the transmission measurement optical system is selected by the switching mechanism. A terahertz spectrometer characterized by being inclined at a predetermined angle with respect to the optical axis of light. The terahertz spectrometer according to claim 3 or 4,
The drive system has a gear device that transmits a rotational force to the pair of connection shafts, and the gear device has a predetermined amount of backlash,
The pair of connecting shafts are fixed eccentrically from the center of gravity of the plane mirror,
When the reflection measurement optical system is selected by the switching mechanism, the shared plane mirror abuts on a first stopper by gravity to define a reflection measurement position,
The terahertz spectrometer is characterized in that when the transmission measurement optical system is selected, the shared plane mirror abuts on a second stopper by gravity to define a reflection measurement position. The terahertz spectrometer according to any one of claims 1 to 5,
Detecting means for detecting the sample set at the position of reflection measurement or the position of transmission measurement,
A terahertz spectrometer, comprising: a control device that drives and controls the switching mechanism based on a detection result of the detection unit to switch between the reflection measurement optical system and the transmission measurement optical system. The terahertz spectrometer according to any one of claims 1 to 6,
The terahertz spectrometer, wherein the reflection measurement optical system and the transmission measurement optical system are housed in a closed container except for at least the sample. The terahertz spectrometer according to claim 1,
The switching mechanism is a reflection measurement optical system unit accommodating a part of the reflection measurement optical system, a transmission measurement optical system unit accommodating a part of the transmission measurement optical system, and a device for selectively using these units. A terahertz spectroscopic device, comprising: a detachable mechanism that is detachably attached to a main body.

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