JP2004271261A - Terahertz spectroscopic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a terahertz spectroscopic device having a small-size casing. <P>SOLUTION: In this device, a terahertz light generation part, a terahertz light detection part and a terahertz optical element are stored in the casing, and a transmission optical element having light condensability is used as a casing window for transmitting terahertz light. Also, a light-condensable optical member held by the terahertz light generation part and a light-condensable optical member held by the terahertz light detection part are used as the casing window. <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 light.
[0002]
[Prior art]
A time-series conversion terahertz spectrometer splits a laser beam, irradiates one with a terahertz light generator to generate terahertz light, and guides the other with a time delay to a terahertz photodetector to terahertz light from a sample. This is a device that detects and measures various characteristics of the sample.
Some conventional terahertz spectroscopy devices are configured such that an optical path of terahertz light is housed in a housing in order to prevent absorption of terahertz light by water vapor in the atmosphere. A terahertz optical element forming a terahertz optical system is housed in a housing, and a terahertz light generator and a detector are also housed in the housing (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP 2000-49402 A (FIG. 13)
[0004]
[Problems to be solved by the invention]
A conventional terahertz spectrometer has an optical element for terahertz light in a vacuum-evacuated housing, and further requires a window member of the housing through which terahertz light is transmitted, which increases the number of components and accommodates these components. There is a problem that the size of the housing is large.
An object of the present invention is to provide a terahertz spectroscopic device having a small housing size.
[0005]
[Means for Solving the Problems]
(1) A terahertz spectrometer according to claim 1, wherein a terahertz light generating unit that emits terahertz light, a terahertz light detecting unit that receives the terahertz light via the sample, and a terahertz light from the terahertz light generating unit is irradiated on the sample. A terahertz optical system that guides terahertz light from the sample to the terahertz light detection unit, a housing that houses the terahertz light generation unit, the terahertz light detection unit and the terahertz optical system, and a sample chamber that installs the sample in the atmosphere. A housing window provided between the terahertz light generation unit and the sample and passing terahertz light from the housing to the sample chamber, and a housing window provided between the sample and the terahertz light detection unit and passing terahertz light from the sample chamber to the housing In addition, a transmission optical element having a light condensing property is used.
(2) The terahertz spectroscopic device according to claim 2, wherein the terahertz light generating unit that emits terahertz light, the terahertz light detecting unit that receives the terahertz light via the sample, and the terahertz light from the terahertz light generating unit is irradiated on the sample. A terahertz optical system that guides terahertz light from the sample to the terahertz light detection unit; and a housing that houses the terahertz optical system. Two housing windows are formed in the housing, and one of the housing windows has a terahertz light generation unit. And a terahertz light detection unit is provided on the other housing window.
[0006]
(3) It is preferable that the inside of the casing of the terahertz spectroscopic device according to claims 1 and 2 be a vacuum or a replacement gas atmosphere.
Further, in the terahertz spectroscopy device according to claim 2, the terahertz light generation unit is formed by the terahertz light generation element and the first optical element to which the element is fixed, and the terahertz light detection unit includes the terahertz light detection element and the element It is preferable that the first and second optical elements are embedded in the housing window, respectively.
The transmission optical element, the first optical element, or the second optical element is preferably made of Si, GaAs, Ge, MgO, polyethylene, quartz, polymethylpentene, sapphire, or diamond. .
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment)
FIG. 1 is an overall configuration diagram of an optical system of a terahertz spectroscopy device according to a first embodiment of the present invention.
In FIG. 1, a laser light L1 emitted from a laser light source 1 is reflected by a plane mirror 2 and split by a beam splitter 3 into two laser lights L2 and L3. As the laser light source 1, for example, a femtosecond pulse laser is used. The laser light L1 is a 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.
[0008]
One of the laser beams L2 split by the beam splitter 3 is reflected by a plane mirror 4, passes through a flat laser beam entrance window 5 provided in a housing 20, passes through a condenser lens 6, and passes through a terahertz light generator 7 Incident on. The inside of the housing 20 is in a vacuum or replacement gas (eg, dry nitrogen, argon gas) atmosphere.
[0009]
The terahertz light generator (terahertz light generating unit) 7 includes a terahertz light generating element 7a and a hemispherical lens 7b bonded to the element. The laser light L2 is pump light (excitation light) for exciting the terahertz light generation element 7a to generate terahertz light. The path from the laser light source 1 to the terahertz light generating element 7a is an optical path of the laser light system on the pump light side through which the laser lights L1 and L2 pass.
[0010]
The terahertz light generating element 7a emits terahertz light T1. The terahertz light T1 is light in a frequency range from approximately 0.01 × 10 ¹² to 100 × 10 ¹² Hertz.
The terahertz light T1 is emitted from the back surface of the terahertz light generating element 7a, is condensed by the hemispherical lens 7b, and enters the parabolic mirror 8. The terahertz light T1 reflected by the parabolic mirror 8 becomes parallel light, reaches the convex lens 9 provided as a housing window on the housing wall 21, is collected by the convex lens 9, and irradiates one point of the sample 30. . That is, the sample 30 is arranged at the focal position of the convex lens 9. The sample 30 is supported by a holding member (not shown) in a sample chamber 31 partitioned by the housing wall 21 and communicating with the atmosphere. Since the sample 30 is in the atmosphere, the sample can be easily exchanged. Further, since there is no optical path of the laser optical system in the sample chamber 31, safety at the time of changing the sample can be ensured. Although not shown, the terahertz light T1 can irradiate an arbitrary point on the sample 30 by moving the sample 30 along a two-dimensional region orthogonal to the optical axis of the parallel light.
[0011]
The terahertz light T2 transmitted through the sample 30 reaches the convex lens 10 provided as a housing window on the housing wall 21 and becomes parallel light by the convex lens 10 and enters the parabolic mirror 11. That is, the sample 30 is arranged at the focal position of the convex lens 10. The terahertz light T2 reflected by the parabolic mirror 11 enters the terahertz light detector 12. The terahertz light detector (terahertz light detection unit) 12 includes a terahertz light detection element 12a and a hemispherical lens 12b bonded thereto. The terahertz light T2 is converged by the hemispherical lens 12b and guided to one point of the terahertz light detection element 12a.
[0012]
The optical path from the terahertz light generation element 7a to the terahertz light detection element 12a is an optical path through which the terahertz lights T1 and T2 pass. The parabolic mirrors 8 and 11 and the convex lenses 9 and 10 are terahertz optical elements constituting a terahertz optical system.
As shown in FIG. 1, the optical path of the terahertz light is in the atmosphere from the exit surface 9a of the convex lens 9 to the incident surface 10a of the convex lens 10.
[0013]
As a material of the convex lenses 9, 10, Si, GaAs, Ge, MgO, polyethylene, quartz, polymethylpentene, sapphire, diamond, or the like can be used. The lens shape may be spherical or aspherical. By using an aspherical lens, aberration can be reduced.
[0014]
The other laser beam L3 split by the beam splitter 3 is a probe beam for detecting the terahertz light T2. The laser beam L3 is sequentially reflected by the plane mirrors 13 and 14, reflected twice or three times by the movable mirror 15 movable in the optical axis direction, sequentially reflected by the plane mirrors 16 and 17, and is provided on the housing 20 by the flat plate. To the laser light entrance window 18. The movable mirror 15 formed by combining two or three plane reflecting mirrors is driven as indicated by an arrow in the drawing, and changes the optical path length of the laser beam L3 according to the amount of movement of the movable mirror 15.
The laser light L3 transmitted through the laser light incident window 18 is incident on the terahertz light detection element 12a via the condenser lens 19. The path from the beam splitter 3 to the terahertz light detecting element 12a is an optical path of the laser optical system on the probe light side through which the laser light L3 passes. Therefore, the optical path through which the laser beams L1, L2 and L3 pass is the entire optical path of the laser optical system.
[0015]
The electric field intensity of the terahertz light T2 converged on one point of the terahertz light detection element 12a is detected as follows.
When the terahertz light T2 enters the terahertz light detection element 12a and irradiates the probe light L3 to this portion, a photocurrent flows according to the electric field intensity of the terahertz light T2. By changing the optical path length of the laser beam L3 using the movable mirror 15 described above, that is, detecting this photocurrent while changing the delay time, time-series conversion terahertz spectroscopy becomes possible. The terahertz light detection element 12a sends the detected photocurrent as a detection signal to a control / calculation device (not shown). The control / arithmetic unit executes a mathematical transformation, for example, a Fourier transform, on the detection signal, and performs an arithmetic operation in accordance with desired characteristics of the sample, for example, electric characteristics and impurity concentration. The obtained data is displayed on a display unit such as a liquid crystal display or a CRT.
[0016]
Here, the terahertz spectrometer of the present embodiment will be compared with the terahertz spectrometer of FIG.
FIG. 6 is an optical path diagram of an optical system of a terahertz spectroscopy device taken as a comparative example. In the optical path diagram of FIG. 6, only the inside of the housing is shown, and components corresponding to those in FIG. 1 are denoted by the same reference numerals. In FIG. 6, the laser optical system outside the housing including the laser light source is the same as that in FIG.
[0017]
In FIG. 6, one laser beam L2 split by the beam splitter passes through a laser beam incident window 5 provided in a housing 40, and enters a terahertz light generator 7 via a condenser lens 6. The inside of the housing 40 is in a vacuum or replacement gas (eg, dry nitrogen, argon gas) atmosphere.
[0018]
The terahertz light T1 emitted from the terahertz light generating element 7a is emitted from the back surface of the terahertz light generating element 7a, is condensed by the hemispherical lens 7b, and is incident on the parabolic mirror 8. The terahertz light T1 reflected by the parabolic mirror 8 becomes parallel light, enters the parabolic mirror 32, is condensed by the parabolic mirror 32, passes through the plate-shaped housing window 42, and passes through the sample 30. Irradiate one point.
[0019]
The sample 30 is set in the sample chamber 41. The terahertz light T <b> 2 transmitted through the sample 30 passes through the plate-shaped housing window 43 and reaches the parabolic mirror 33. The housing windows 42 and 43 have a flat plate shape and do not have a light collecting action. The terahertz light T2 reflected by the parabolic mirror 33 becomes parallel light, enters the parabolic mirror 11, is reflected by the parabolic mirror 11, and enters the terahertz light detector 12.
The other laser beam L3 split by the beam splitter passes through the laser beam incident window 18 provided in the housing 40, and enters the terahertz photodetector 12 via the condenser lens 19.
[0020]
In FIG. 6, the optical path from the terahertz light generating element 7a to the terahertz light detecting element 12a is a path through which the terahertz lights T1 and T2 pass. The parabolic mirrors 8, 32, 33, and 11 and the housing windows 42 and 43 are terahertz optical elements constituting a terahertz optical system.
[0021]
In the terahertz spectroscopic device of the present embodiment shown in FIG. 1, the parabolic mirrors 32 and 33 can be omitted because the optical element used as the housing window has a light condensing function as compared with the device of the comparative example in FIG. . Since the number of optical elements through which the terahertz light passes is reduced as compared with the device of the comparative example, the loss of the terahertz light is small and the size of the housing can be reduced.
[0022]
(Second embodiment)
FIG. 2 is an optical path diagram of the terahertz optical system of the terahertz spectroscopy according to the second embodiment of the present invention. In the optical path diagram of FIG. 2, only the inside of the housing is shown. Components corresponding to those in FIG. 1 are denoted by the same reference numerals, and differences will be described. Further, in FIG. 2, the laser optical system outside the housing including the laser light source is the same as that in FIG.
[0023]
The difference between the terahertz spectrometer of the present embodiment shown in FIG. 2 and the terahertz spectrometer of the first embodiment is that the parabolic mirrors 8 and 11 of FIG. 1 are omitted. That is, the terahertz light T1 emitted from the terahertz light generator 7 directly reaches the convex lens 9 and is focused on one point of the sample 30. The terahertz light transmitted through the sample 30 is directly condensed on the terahertz light detector 12 by the convex lens 10 as terahertz light T2.
Accordingly, the number of optical elements through which terahertz light passes is further reduced as compared with the first embodiment, so that the loss of terahertz light is small and the size of the housing can be reduced.
[0024]
(Third embodiment)
FIG. 3 is an optical path diagram of a terahertz optical system of the terahertz spectroscopic device according to the third embodiment of the present invention. The terahertz optical system is a parallel light irradiation optical system. In the optical path diagram of FIG. 3, only the inside of the housing is shown, and components corresponding to those in FIG. 1 are denoted by the same reference numerals, and differences will be described. In FIG. 3, the laser optical system outside the housing including the laser light source is the same as that in FIG.
[0025]
The terahertz spectrometer of the present embodiment shown in FIG. 3 differs from the terahertz spectrometer of the first embodiment in that the parabolic mirrors 8 and 11 in FIG. That is, an irradiation optical system is used. That is, the terahertz light T1 emitted from the terahertz light generator 7 directly reaches the convex lens 9, and the terahertz light T2 transmitted through the convex lens 10 directly enters the terahertz light detector 12. In the parallel light irradiation optical system of the present embodiment, the space between the convex lens 9 and the convex lens 10 is a parallel light flux. With such an optical system, averaged information from a two-dimensional area of the sample can be obtained.
Thus, even in the parallel light irradiation optical system, the number of optical elements through which terahertz light passes is further reduced as compared with the first embodiment, so that the loss of terahertz light is small and the size of the housing can be reduced. it can.
[0026]
(Fourth embodiment)
FIG. 4 is an overall configuration diagram of an optical system of a terahertz spectroscopy device according to a fourth embodiment of the present invention. 4, components corresponding to those in FIG. 1 are denoted by the same reference numerals. Further, in FIG. 4, the laser light source and the laser optical system up to the plane mirror 4 and the plane mirror 17 are the same as those in FIG.
[0027]
One laser beam L2 split by the beam splitter passes through the condenser lens 6 and reaches the terahertz light generator 107 provided in the housing 20A. The terahertz light generator 107 includes a terahertz light generating element 107a and a hemispherical lens 107b bonded thereto.
In the present embodiment, the hemispherical lens 107b is an optical element that transmits terahertz light, and also serves as a housing window that separates the inside of the housing from the atmosphere. The terahertz light T1 emitted from the terahertz light generating element 107a is emitted from the back surface of the terahertz light generating element 107a, is condensed by the hemispherical lens 107b, and is incident on the parabolic mirror 8. The terahertz light T1 reflected by the parabolic mirror 8 becomes parallel light, enters the parabolic mirror 32, is collected by the parabolic mirror 32, and irradiates one point of the sample 30.
[0028]
The sample 30 is held in a housing 20A, unlike the first to third embodiments. Although not shown, the terahertz light T1 can irradiate an arbitrary point on the sample 30 by moving the sample 30 along a two-dimensional region orthogonal to the optical axis of the parallel light. Inside the housing 20A is a vacuum or a replacement gas (eg, dry nitrogen, argon gas) atmosphere.
[0029]
The terahertz light T2 transmitted through the sample 30 is reflected by the parabolic mirror 33, becomes parallel light, enters the parabolic mirror 11, is reflected by the parabolic mirror 11, and enters the terahertz light detector 112. I do. The terahertz light detector 112 includes a terahertz light detection element 112a and a hemispherical lens 112b bonded thereto.
In the present embodiment, the hemispherical lens 112b is an optical element that transmits terahertz light, and also serves as a housing window that separates the inside of the housing from the atmosphere. The terahertz light T2 is converged by the hemispherical lens 112b and guided to one point of the terahertz light detection element 112a. As described above, the other laser beam L3 split by the beam splitter is incident on this point, so that the terahertz light T2 is detected.
[0030]
The optical path from the terahertz light generating element 107a to the terahertz light detecting element 112a is an optical path through which the terahertz lights T1 and T2 pass. The parabolic mirrors 8, 32, 33, and 11 are terahertz optical elements forming a terahertz optical system. Note that Si is used as a material for the hemispherical lenses 107b and 112b.
[0031]
In the terahertz spectroscopy apparatus of the present embodiment, the hemispherical lens 107b of the terahertz light generator 107 and the hemispherical lens 112b of the terahertz light detector 112 are also used as a housing window through which the terahertz light is transmitted. There is no laser light. Therefore, safety can be ensured when exchanging the sample and adjusting the optical axis of the terahertz optical system.
[0032]
In the terahertz spectrometer of the present embodiment, the optical path of the laser optical system is completely outside the housing, so that the optical axis of the laser optical system can be easily adjusted.
In addition, since the laser light incident windows 5 and 18 which are present in the first to third embodiments are not required, the loss of the laser light is reduced, and particularly when the femtosecond pulse laser light is used, the laser light incident window is not required. Does not affect the pulse width of the laser light.
[0033]
(Fifth embodiment)
FIG. 5 is an overall configuration diagram of an optical system of a terahertz spectroscopy device according to a fifth embodiment of the present invention. 5, parts corresponding to those in FIG. 4 are denoted by the same reference numerals, and differences will be mainly described. In FIG. 5, the laser light source and the laser optical system are the same as those in FIGS.
[0034]
The difference between the terahertz spectrometer of the present embodiment shown in FIG. 5 and the device of the fourth embodiment is that the parabolic mirrors 32 and 33 of FIG. 31 and the convex lens 9 and the convex lens 10 were used as a housing window. The difference between the terahertz spectroscopic device of the present embodiment and the device of the first embodiment is that the hemispherical lens 107b and the hemispherical lens 112b are used as housing windows. That is, in the present embodiment, the convex lens 9, the convex lens 10, the hemispherical lens 107b, and the hemispherical lens 112b allow the passage of terahertz light and also serve as a housing window separating the housing from the atmosphere. With such a configuration, the convenience in exchanging the sample and the safety in adjusting the optical axis of the terahertz optical system are improved, and the number of parts can be reduced and the size of the housing can be reduced.
[0035]
Further, in the terahertz spectroscopy apparatus of the present embodiment, similarly to the apparatus of the fourth embodiment, the optical path of the laser optical system is completely outside the housing, so that the optical axis of the laser optical system can be easily adjusted. The optical axis of the terahertz optical system can be safely adjusted. Further, since the laser light entrance windows 5 and 18 are not required, the loss of the laser light is reduced, and particularly when the femtosecond pulse laser light is used, the influence of the dispersion of the laser light entrance window on the pulse width of the laser light. Is also gone.
[0036]
In this embodiment, an optical element through which terahertz light passes is a combination of the first embodiment and the fourth embodiment. Similarly, the terahertz spectroscopy device according to the present invention can be provided by combining the second embodiment and the fourth embodiment, or by combining the third embodiment and the fourth embodiment.
[0037]
In the first to fifth embodiments, transmission measurement for measuring terahertz light transmitted through a sample has been described. However, the present invention is also applicable to reflection measurement reflected on a sample.
In the first to third and fifth embodiments, the sample 30 is held in the sample chamber 31 and is in the atmosphere. In order to reduce the influence of water vapor in the atmosphere, the optical path of the terahertz light in the atmosphere should be as short as possible. For this purpose, the focal lengths of the convex lenses 9 and 10 may be reduced. As a result, the sample chamber becomes smaller and the housing can be made smaller.
In the first to fifth embodiments, the inside of the housing is desirably set to a vacuum or a replacement gas atmosphere. However, even in a state where the housing is open to the atmosphere, the influence of dust and the like from the outside can be reduced.
[0038]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a terahertz spectroscopic device having a small housing size.
[Brief description of the drawings]
FIG. 1 is an optical path diagram of an optical system of a terahertz spectroscopy apparatus according to a first embodiment of the present invention.
FIG. 2 is an optical path diagram of a terahertz optical system of a terahertz spectroscopy apparatus according to a second embodiment of the present invention.
FIG. 3 is an optical path diagram of a terahertz optical system of a terahertz spectrometer according to a third embodiment of the present invention.
FIG. 4 is an optical path diagram of an optical system of a terahertz spectroscopic device according to a fourth embodiment of the present invention.
FIG. 5 is an optical path diagram of an optical system of a terahertz spectrometer according to a fifth embodiment of the present invention.
FIG. 6 is an optical path diagram of a terahertz optical system of a terahertz spectroscopy apparatus taken as a comparative example.
[Explanation of symbols]
1: laser light source 3: beam splitters 7, 107: terahertz light generators 7a, 107a: terahertz light generating elements 7b, 107b: hemispheric lenses 8, 11, 32, 33: parabolic mirrors 9, 10: convex lenses 12, 112 : Terahertz light detectors 12a, 112a: Terahertz light detection elements 12b, 112b: Hemispherical lenses 20, 20A: Housing 30: Samples L1, L2, L3: Laser light T1, T2: Terahertz light

Claims (5)

A terahertz light generator that emits terahertz light,
A terahertz light detection unit that receives the terahertz light through a sample,
A terahertz optical system that irradiates the sample with terahertz light from the terahertz light generation unit and guides terahertz light from the sample to the terahertz light detection unit;
A housing housing the terahertz light generation unit, the terahertz light detection unit, and the terahertz optical system;
A sample chamber for installing the sample in the atmosphere,
A housing window that is provided between the terahertz light generation unit and the sample, passes a terahertz light from the housing to the sample chamber, and is provided between the sample and the terahertz light detection unit, and is provided from the sample chamber. A terahertz spectrometer, wherein a transmission optical element having a light-collecting property is used for a housing window through which terahertz light passes through the housing. A terahertz light generator that emits terahertz light,
A terahertz light detection unit that receives the terahertz light through a sample,
A terahertz optical system that irradiates the sample with terahertz light from the terahertz light generation unit and guides terahertz light from the sample to the terahertz light detection unit;
A housing for housing the terahertz optical system,
The housing is formed with two housing windows, one of the housing windows is provided with the terahertz light generation unit, and the other of the housing windows is provided with the terahertz light detection unit. Terahertz spectrometer. The terahertz spectrometer according to claim 1 or 2,
A terahertz spectrometer, wherein the inside of the housing is a vacuum or a replacement gas atmosphere. The terahertz spectrometer according to claim 2,
The terahertz light generation unit is formed of a terahertz light generation element and a first optical element to which the element is fixed,
The terahertz light detection unit is formed from a terahertz light detection element and a second optical element to which the element is fixed,
The terahertz spectroscopy device, wherein the first and second optical elements are respectively buried in the housing window. The terahertz spectroscopic device according to claim 1, 3 or 4,
The transmission optical element, the first optical element, or the second optical element is any one of Si, GaAs, Ge, MgO, polyethylene, quartz, polymethylpentene, sapphire, and diamond. A terahertz spectroscopy device, comprising:

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