JP2009288047A - Liquid cell for terahertz spectroscopic analysis and method for manufacturing liquid cell for terahertz spectroscopic analysis - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid cell for terahertz spectroscopic analysis, for smoothly performing solution replacement and providing a high signal, and a method for manufacturing the liquid cell for terahertz spectroscopic analysis. <P>SOLUTION: The liquid cell 1 includes two translucent substrates 2 and 3 transmitting terahertz pulse light, which are superposed and adhered together with a liquid flow passage 2A at the interface between the translucent substrates 2 and 3 to which a sample solution is injected. The liquid flow passage 2A is one flow passage formed on one side of the translucent substrate 2 and composed of a spiral passage part 2a formed in an area enclosing a light collecting area CA of terahertz pulse light, a liquid guide passage part 2b and an outflow passage part 2c, and the passage is connected to a liquid inlet port part 3a and an outflow port part 3b formed on one side of the translucent substrate 3. Microtubes 4 to be connected to a liquid chromatography or the like are attached to the liquid inlet port part 3a and the outflow port part 3b. The liquid cell 1 is used to measure time waveform of an oscillating electric field by use of a terahertz pulse spectroscopic measuring device by injecting the sample solution in the liquid flow passage 2A. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid cell for terahertz spectral analysis that can be suitably used in a spectroscopic measurement apparatus that uses a terahertz frequency band as a light source, and a method for manufacturing a liquid cell for terahertz spectral analysis.

In recent years, terahertz time domain spectroscopy (THz) in which light (pulsed electromagnetic waves) in a terahertz frequency region (0.1 THz to 10 THz) is irradiated onto a sample and transmitted light transmitted through the sample or reflected light reflected from the sample is detected. -TDS: THz-Time Domain Spectroscopy) is drawing attention.
The THz-TDS method uses a terahertz pulse spectroscopic measurement device to measure the electric field strength of a sample depending on the time of terahertz light (pulsed electromagnetic wave), and performs Fourier transform processing on the time-series data depending on the time. The frequency dependence of the electric field strength and phase forming the pulse can be obtained (see, for example, Patent Document 1).

  Conventionally, when a liquid (sample solution) is measured using such a THz-TDS method, a transmission measurement method can be used for a sample solution containing a solvent that absorbs weak pulse light such as ethanol. It is difficult to use a transmission measurement method for a sample solution containing a solvent that strongly absorbs pulsed light, and a reflection measurement method is generally used. For example, a reflection measurement method (total reflection attenuation) that measures using evanescent light generated by placing a sample (solution sample) on a triangular prism that transmits THz light and totally reflecting the bottom surface of the triangular prism. Spectroscopy) (see Non-Patent Document 1).

The transmission measurement method using a triangular prism as shown in Non-Patent Document 1 is easily affected by moisture in the air, and must be used in a nitrogen atmosphere, and the sample solution is triangulated every time the sample solution is replaced. There is a problem that the sample solution needs to be completely adhered to the bottom surface, and that the sample solution replacement and measurement work are complicated.
In order to solve these problems, a test object is applied to the surface of a chip on which a transmission line and an antenna having a coplanar stripline structure on an Si substrate are formed, and the interaction with THz electromagnetic waves propagating through the transmission line is reduced by air. There has been proposed a sensing device that senses physical properties of an inspection object by a reflection measurement method using an evanescent wave that has oozed out (see, for example, Patent Document 2).

JP 2006-266908 A JP 2006-64691 A Junichi Nishizawa, “Basics and Applications of Terahertz Waves”, first edition, Industrial Research Institute, Inc., April 1, 2005, p. 245

  However, the reflection measurement method performed by applying an inspection object to the chip surface as shown in Patent Document 2 determines the thickness of the inspection object based on the wettability of the inspection object, gravity, etc. It is difficult to control the thickness by, for example, and a stable analysis result with high accuracy cannot be obtained. Therefore, regardless of the absorption coefficient of the liquid (sample solution), a high-accuracy signal can be obtained corresponding to any sample solution, and a liquid cell that allows easy replacement of the sample solution and facilitates measurement work has appeared. It is desired.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
The liquid cell for terahertz spectroscopic analysis according to this application example is formed by laminating a translucent base material that transmits terahertz light, and has a liquid flow path in which the liquid flows along the interface of the translucent base material. In addition, at least in a region including a condensing area where the terahertz light is collected, a liquid flow path portion having an isotropic structure with respect to the polarized terahertz light is provided.

  According to this, the liquid cell for terahertz spectroscopic analysis is formed by laminating a translucent base material that transmits terahertz light, and has a liquid flow path in which the liquid flows along the interface of the translucent base material. In addition, at least in the region including the condensing area where the terahertz light is collected, by having a liquid flow path portion with an isotropic structure with respect to the polarized terahertz light, generation of diffraction resonance of the terahertz light is greatly suppressed, and high An accurate signal can be obtained. Therefore, any liquid can be handled regardless of the absorption coefficient of the liquid. Moreover, the attachment direction with respect to the condensing area of a liquid cell can be set arbitrarily and used.

[Application Example 2]
In the liquid cell for terahertz spectroscopic analysis according to the application example, the liquid flow path portion having the isotropic structure includes a double spiral in which two spirals are coupled to each other at a substantially central portion of the spiral, and the coupling portion is a base point of each other. A spiral flow path made of a spiral is preferable.

  According to this, the liquid flow path portion having an isotropic structure formed in a region including at least a condensing area where the terahertz light is collected, the two spirals are coupled at the substantially central portion of the spiral, and the coupling portion By using a spiral flow path composed of double spirals having the mutual base points as the mutual base points, generation of diffraction resonance of terahertz light can be significantly suppressed, and a highly accurate signal can be obtained. Therefore, any liquid can be handled regardless of the absorption coefficient of the liquid. Moreover, the attachment direction with respect to the condensing area of a liquid cell can be set arbitrarily and used.

[Application Example 3]
In the liquid cell for terahertz spectroscopic analysis according to the application example described above, a large number of protrusions having an aspect ratio represented by the following general formula (3) on the surface in the thickness direction of the laminate of the laminated translucent base materials However, it is preferable to have an antireflection function formed in an array with a period P equal to or less than the terahertz wavelength.
1.5 <(H / P) (3)
However, H represents the height from the bottom of the protrusion to the apex, and P represents the period.

  According to this, on the surface in the plate thickness direction of the laminate of the translucent substrate on which the translucent substrate is laminated, a large number of protrusions whose aspect ratio is represented by the above general formula (3) are terahertz wavelengths. By providing an antireflection function formed in an array with the following period P, a high transmittance characteristic corresponding to a wide frequency region of the terahertz light condensed on the liquid cell for terahertz spectroscopy can be obtained. Therefore, a signal with higher accuracy can be obtained.

[Application Example 4]
In the liquid cell for terahertz spectroscopic analysis according to the application example, the translucent substrate is made of any of quartz, sapphire, polyethylene, polypropylene, fluororesin, polymethylpentene resin, diamond, and translucent ceramic. Is preferred.

  According to this, the translucent base material on which the two translucent base materials are laminated and pasted is quartz, sapphire, polyethylene, polypropylene, fluororesin, polymethylpentene resin, diamond, translucent ceramic. Thus, a liquid cell for terahertz spectroscopic analysis that transmits terahertz pulse light can be obtained. Furthermore, the material of the translucent substrate suitable for the processing method of forming the liquid flow path along the interface of the translucent substrate can be selected. For example, the materials of the transparent base materials to be laminated may be different from each other. By joining a translucent base material that is easy to form a recess on the surface and a translucent base material that has a smooth surface and mechanical strength that is resistant to stress deformation, it can be formed with easy processing, In addition, a liquid cell for terahertz spectroscopic analysis that hardly causes stress deformation can be obtained.

[Application Example 5]
The method for manufacturing a liquid cell for terahertz spectroscopy according to this application example is formed by laminating a translucent substrate that transmits terahertz light, and a liquid flow in which a liquid flows along an interface of the translucent substrate. A method for producing a liquid cell for terahertz spectroscopy having a channel, wherein a photosensitive film is laminated on a surface of the translucent substrate, and the liquid channel is formed on the surface of the translucent substrate. A masking process for forming a mask of the photosensitive film having a similar shape, a blasting process for spraying an abrasive onto the surface of the translucent substrate masked with the photosensitive film, and a mask for removing the mask A peeling step and a translucent base material joining step of laminating the translucent base materials and joining each other are provided.

  According to this manufacturing method, a masking step of laminating a photosensitive film on the surface of the translucent substrate and forming a mask of the photosensitive film having a shape similar to the liquid flow path on the surface of the translucent substrate; , A blasting process for spraying an abrasive on the surface of a translucent substrate masked with a photosensitive film, a mask peeling process for removing the mask, and a translucent substrate for laminating a translucent substrate and bonding them together The terahertz spectroscopic liquid cell capable of obtaining a highly accurate signal can be easily manufactured by providing the conductive substrate bonding step.

[Application Example 6]
The method for manufacturing a liquid cell for terahertz spectroscopy according to this application example is formed by laminating a translucent substrate that transmits terahertz light, and a liquid flow in which a liquid flows along an interface of the translucent substrate. A method of manufacturing a liquid cell for terahertz spectroscopy having a channel, wherein a metal film and a resist film are formed on a surface of the translucent substrate in order from the surface, and the resist film is irradiated with light or an electron beam. An etching mask forming step of etching the metal film to form an etching mask after drawing a shape similar to the liquid flow path, and an etching step of etching the translucent substrate on which the etching mask is formed; And a peeling step of peeling the resist film and the etching mask, and a translucent base material joining step of laminating the translucent base materials and joining them to each other.

  According to this manufacturing method, after forming a metal film and a resist film on the surface of the translucent substrate in order from the surface, and irradiating the resist film with light or an electron beam to draw a shape similar to a liquid channel Etching mask forming process for etching metal film to form etching mask, etching process for etching translucent substrate on which etching mask is formed, peeling process for stripping resist and etching mask, translucency By providing a translucent base material joining step in which base materials are laminated and joined together, a liquid cell for terahertz spectroscopic analysis in which a highly accurate liquid flow path is formed can be easily manufactured. Therefore, a liquid cell for terahertz spectroscopic analysis capable of obtaining a higher signal can be obtained.

Hereinafter, an example of the liquid cell for terahertz spectroscopy according to the present embodiment will be described with reference to FIG.
Note that the terahertz spectroscopic liquid cell of the present embodiment is a liquid cell for analyzing the frequency dependence of a sample solution using a transmission measurement method.

  FIG. 1A is a front view schematically showing a configuration of a liquid cell for terahertz spectroscopy according to the present embodiment, and FIG. 1B is a diagram illustrating terahertz spectroscopy in a section AA in FIG. It is sectional drawing of the liquid cell for analysis. In the drawings shown below, the dimensions and ratios of the constituent elements are different from actual ones for convenience of explanation.

In FIG. 1, a liquid cell for terahertz spectroscopy analysis (hereinafter sometimes referred to as a liquid cell) 1 includes two translucent substrates 2 and 3 that transmit terahertz light and a microtube 4. Yes.
The translucent substrates 2 and 3 are both made of a Z plate crystal, and have, for example, a rectangular flat plate shape with a plate thickness of about 1.35 mm and a plane size of about 10 mm × 17 mm.

The translucent substrate 2 has a liquid channel 2 </ b> A serving as a liquid (sample solution) passage on one surface.
The liquid channel 2A is constituted by a single channel including a spiral channel 2a, a liquid guide channel 2b, and an outflow channel 2c. The liquid flow path 2A (the spiral flow path portion 2a, the liquid introduction flow path portion 2b, and the outflow flow path portion 2c) is formed of, for example, recesses (grooves) of the same size having a width of about 100 μm and a depth of about 100 μm.

  The spiral flow path portion 2a is a flow path arranged in a spiral shape. Two spirals are coupled at the substantially central part of the spiral, and a double spiral with a predetermined interval (pitch) having the coupling part as a base point of each other is formed. For example, it is formed around the left. The predetermined interval of the double spiral is, for example, 200 μm. The spiral channel portion 2a is formed in a region including at least a condensing area CA (a circular inner region indicated by a two-dot chain line in the drawing) of terahertz light irradiated from a terahertz pulse spectroscopic measurement device 100 described later. Yes. The diameter of the condensing area CA is about 3 mm.

  In addition, the spiral channel portion 2a (double spiral) is coupled to the liquid guide channel portion 2b having one end extending along the long side of the rectangular shape toward the short side, and the other end is guided. Similarly to the liquid flow path portion 2b, it is coupled to the outflow flow path portion 2c extending to the same short side along the other long side of the rectangular shape.

  The translucent base material 3 is formed so that a part of the short side of the liquid introduction flow path portion 2b and the outflow flow path portion 2c formed on the surface of the translucent base material 2 overlaps on one surface. The liquid introduction port portion 3a and the outflow port portion 3b, each of which extends along the long side direction of the rectangle and opens on one short side of the rectangle and has a recess having a width of about 600 μm and a depth of about 600 μm, They are spaced apart in the direction.

  The liquid introduction port portion 3a communicates with the liquid introduction flow passage portion 2b of the liquid flow passage 2A formed on one surface of the translucent substrate 2, and the spiral flow through the liquid introduction flow passage portion 2b. A microtube 4a for supplying a liquid (sample solution) to the liquid cell is inserted and attached to the passage 2a. On the other hand, the outflow port 3b communicates with the outflow channel 2c of the liquid channel 2A, and the liquid (sample solution) that has passed through the spiral channel 2a flows out through the outflow channel 2c. A microtube 4b is attached in the same manner as the liquid introduction port 3a.

  Thus, the translucent substrate 2 in which the liquid flow path 2A made of the concave portion is formed on one surface, and the liquid introduction port portion 3a and the outlet port portion 3b made of the concave portion are formed on the one surface. The optical base material 3 is bonded to each other by using an adhesive (not shown) with the respective outer shapes substantially matched to each other, with the surfaces on which the concave portions are formed being overlapped with each other. Thereby, the liquid flow path 2 </ b> A is located at the interface between the translucent substrate 2 and the translucent substrate 3.

  In addition, in the area | region except the liquid flow path 2A of the translucent base material 2, the excess adhesive apply | coated when adhering the translucent base material 2 and the translucent base material 3 is dropped inside. A large number of adhesive dropping grooves (not shown) serving as an adhesive reservoir are formed in a matrix. The adhesive dropping groove is formed so as not to be applied to any of the spiral flow path portion 2a, the liquid introduction flow path portion 2b, and the outflow flow path portion 2c.

  The microtube 4 (4a, 4b) is made of, for example, fluorine plastic such as PFA or ETFE having an outer diameter of about 0.4 mm and an inner diameter of about 0.2 mm, and is provided in each hole of the liquid introduction port portion 3a and the outlet portion 3b. And bonded and fixed to the translucent substrate 2 and the translucent substrate 3 with a silicone-based adhesive 5.

  The microtube 4 (4a, 4b) is bonded and fixed at a position where at least a space in which the liquid can flow is formed between the inner wall of each hole to be inserted and the tip of the tube. Accordingly, the liquid supplied from the microtube 4a is supplied from the liquid introduction channel 2b, the spiral channel 2a, and the outflow channel 2c of the liquid channel 2A formed on the surface of the translucent substrate 2. It passes through in order and can flow out from the microtube 4b.

  The liquid is supplied from the outflow port 3b (microtube 4b), passes through the outflow channel 2c, the spiral channel 2a, and the liquid guide channel 2b in this order, and enters the liquid guide channel 2b. You may use so that it may flow outside from the liquid introduction port part 3a (microtube 4a) which connects.

In addition, the liquid cell 1 formed by laminating the translucent substrates 2 and 3 desirably has an antireflection function on the surfaces of the translucent substrates 2 and 3 which are both surfaces in the plate thickness direction.
FIG. 2 is a perspective view schematically showing an antireflection structure formed on the surface of the translucent substrate.

In FIG. 2, on the surface of the translucent base materials 2 and 3, a large number of fine-structured protrusions T made of a square pyramid with a bottom shape arranged in an array with a period P of terahertz wavelength or less. Is formed. That is, a moth-eye structure is formed.
The aspect ratio of the projection T is preferably a value represented by the following general formula (1).
1.5 <(H / P) (1)
However, H represents the height from the bottom to the top of the quadrangular pyramid, and P represents the period.

This antireflection structure can be formed on one surface of the translucent substrates 2 and 3 in advance using a grinding method, a blasting method, an etching method, a laser processing method, or the like.
The antireflection structure formed by arranging the protrusions T in an array can correspond to a wide frequency region including the terahertz wavelength region. Further, by continuously changing the refractive index, the reflection of light is suppressed, and the generation of diffracted light is prevented and a high antireflection effect is obtained. Furthermore, the protrusions T can be formed on the surfaces of the translucent substrate 2 and the translucent substrate 3 without any gaps, and higher transmittance characteristics can be obtained. Therefore, the liquid cell 1 having high transmittance characteristics and corresponding to a wide frequency range including the terahertz wavelength range can be obtained.

  In addition, although the processus | protrusion T which forms an antireflection structure demonstrated in the case where the bottom face shape consists of a square frustum with a square shape, it is not limited to this. The base shape may be a trapezoidal protrusion having a regular hexagon or a regular triangle. That is, the projection may be a trapezoidal hexagonal frustum or a trapezoidal triangular frustum. Moreover, the antireflection structure should just be formed in the area | region used as the condensing area CA at least.

The liquid cell 1 configured as described above is used for injecting a liquid (sample solution) into the liquid flow path 2A and analyzing the frequency dependence of the liquid (sample solution) by a permeation measurement method.
Next, the terahertz pulse spectrometer 100 that measures a sample solution using the liquid cell 1 will be described.
FIG. 3 is a schematic diagram illustrating a schematic configuration of the terahertz pulse spectrometer. Note that the terahertz pulse spectroscopic measurement apparatus 100 is shown with the liquid cell 1 set therein.

  In FIG. 3, the terahertz pulse spectroscopic measurement apparatus 100 irradiates the liquid cell 1 into which the sample solution is injected with terahertz light in a pulse shape, and at the time of the electric field intensity of the terahertz pulse light transmitted through the liquid cell 1 (sample solution). Frequency dependence of the electric field strength, spectral transmittance, absorption rate, etc., by measuring the dependent waveform (time waveform of the oscillating electric field) and subjecting the time series data based on the time waveform of the oscillating electric field to Fourier transform processing. Etc. are obtained.

  The terahertz pulse spectroscopic measurement apparatus 100 is a pump-probe spectroscopic measurement apparatus, which includes a laser generator 30 that emits pulsed light L1, a beam splitter 31, mirrors 32, 41, 43, 44, and 45, and terahertz light. A generation element 33, condenser lenses 34 and 46, off-axis parabolic mirrors 35 and 36, a time delay device 42, and a terahertz light detection element 47 are provided.

  The terahertz pulse spectroscopic measurement apparatus 100 includes a current amplifier 50 connected to the terahertz light detection element 47, a lock-in amplifier 51, a computer 52, and a holder 60 that holds and fixes the liquid cell 1.

Laser generator 30 includes a femtosecond (10 ^-15 second) pulsed laser light source, the repetition period of several kHz~ number 10MHz about, pulse width emits pulsed light L1 of the linearly polarized light of about 10～150Fs.
The beam splitter 31 splits the pulsed light L1 emitted from the laser generator 30 into pump light L2 and probe light L11.

The terahertz light generating element 33 includes a semiconductor substrate 33a, a super hemispherical lens 33b, and the like.
In the semiconductor substrate 33a, a photoconductive antenna having a minute gap 33c between parallel transmission lines made of an alloy is formed on a substrate made of low-temperature grown gallium arsenide, and several tens of volts are provided between the parallel transmission lines (small gap 33c). By applying the voltage (33d), terahertz light is generated from the pump light L2 that is focused and incident on the minute gap 33c via the condenser lens 34. The super hemispherical lens 33b has a function of collimating terahertz pulse light generated on the semiconductor substrate 33a.

Both the off-axis parabolic mirror 35 and the off-axis parabolic mirror 36 include two concave mirrors having a rotating paraboloid.
The off-axis parabolic mirror 35 has a function of reflecting the terahertz light L <b> 3 (pulse form) emitted from the terahertz light generating element 33 so as to be focused and irradiated toward the liquid cell 1. The off-axis parabolic mirror 36 has a function of reflecting the terahertz light L4 transmitted through the liquid cell 1 and focusing and irradiating the terahertz light detection element 47.

  The time delay device 42 includes a movable stage 42a provided with a folding mirror 42b, a moving device (not shown) for moving the movable stage 42a in the β direction indicated by an arrow in the drawing. The time delay device 42 has a function of giving a time delay to the probe light L11 that is split by the beam splitter 31 and incident on the folding mirror 42b of the movable stage 42a.

Similar to the terahertz light generating element 33, the terahertz light detecting element 47 includes a semiconductor substrate 47a and a super hemispherical lens 47b.
In the semiconductor substrate 47a, a minute gap (photoconductive antenna) 47c is formed between parallel transmission lines made of an alloy on a substrate made of gallium arsenide or the like, and a minute ammeter 47d is formed between the parallel transmission lines (small gap 47c). Is connected.

  The terahertz light detecting element 47 is opposite to the terahertz light L4 that is focused from the off-axis parabolic mirror 36 through the super hemispherical lens 47b and focused on the minute gap 47c, and the terahertz light L4 through the condensing lens 34. From the probe light L12 time-delayed by the time delay device 42 that is focused and irradiated on the photoconductive antenna 47c from the side, an instantaneous current (instantaneous current waveform) proportional to the oscillating electric field of the terahertz light L4 in the minute ammeter 47d It has a function to measure. That is, the time waveform (time-series data depending on time) of the oscillating electric field of the terahertz light L4 is measured.

The current amplifier 50 amplifies the instantaneous current detected by the terahertz light detection element 47.
The lock-in amplifier 51 performs synchronous detection by modulating the optical chopper in order to reduce the noise component of the time waveform of the oscillating electric field amplified by the current amplifier 50.

  The computer 52 includes a memory circuit, an arithmetic circuit, a display, and the like, and obtains frequency characteristics of the spectral transmittance of the terahertz light L4 by performing Fourier transform on the time waveform of the terahertz light L4 detected through the lock-in amplifier 51. be able to.

  The holder 60 is a detachable chuck for holding and fixing the liquid cell 1 (see FIG. 1). Two holders 60a attach the liquid cell 1 on which the translucent substrates 2 and 3 are superposed on both sides in the plate thickness direction. Clamp it from the (front and back) side and fix it. The holder 60 is disposed between the off-axis parabolic mirror 35 and the off-axis parabolic mirror 36 at a position where the terahertz light L3 is substantially focused.

The two holders 60a are formed with through holes 60b that function as windows through which the terahertz light L3 passes. Each through-hole 60b forms a circular hole of the same shape having a size larger than the condensing area CA of the liquid cell 1.
In the liquid cell 1 held and fixed to the holder 60, the microtube 4a (see FIG. 1) attached to the liquid introduction port 3a is connected to, for example, a liquid chromatography 61 and attached to the outflow port 3b. A tube 4b (see FIG. 1) is connected to a waste liquid container (not shown).

  The liquid chromatography 61 is a device that includes, for example, a syringe-type pump that uses a motor as a power source, uses a liquid as a mobile phase, and separates components of a mixture into components based on molecular weight, for example. The liquid (sample solution) separated for each component is injected as a sample solution to be analyzed using the liquid cell 1 into the liquid flow path 2A of the liquid cell 1 through the microtube 4a by operating the pump. Or discharged into a waste liquid container through the microtube 4b. The injection speed at which the sample solution is injected into the liquid flow path 2A of the liquid cell 1, that is, the speed at which the liquid is discharged from the liquid flow path 2A is, for example, about 1 cm / sec.

  When a liquid channel shape with a variable channel diameter (channel width) is formed when liquid is injected into or discharged from the liquid channel of the liquid cell 1, bubbles are easily generated. In particular, in a liquid channel shape in which the channel diameter changes from small to large, the inflow pressure decreases due to a rapid increase in the channel volume, and the liquid is easily vaporized to generate bubbles. On the other hand, the liquid flow path 2A of the liquid cell 1 is formed by a flow path composed of recesses of the same size, thereby smoothly injecting and discharging without generating defective bubbles such as generation of bubbles and residual sample solution. It can be performed.

  Next, the operation of the terahertz pulse spectrometer 100 will be briefly described. The holder 60 holds and fixes the liquid cell 1 in which a liquid (sample solution) is previously injected from the liquid chromatography 61 into the liquid channel 2A via the microtube 4a.

First, pulse light L1 of a femtosecond pulse laser is emitted from the laser generator 30. The pulsed light L1 emitted from the laser generator 30 has, for example, a repetition period of 10 MHz and a pulse width of 100 fs.
Then, the pulse light L 1 of the femtosecond pulse laser emitted (emitted) from the laser generator 30 enters the beam splitter 31. In the beam splitter 31, the incident pulsed light L1 is split into pump light L2 and probe light L11.

  One pump light L <b> 2 divided by the beam splitter 31 is reflected by the mirror 32 and then enters the terahertz light generation element 33 through the condenser lens 34. The pump light L2 incident on the terahertz light generating element 33 is focused on the minute gap (photoconductive antenna) 33c between the parallel transmission lines formed on the semiconductor substrate 33a and applied with a voltage of several tens of volts.

  In the terahertz light generating element 33, photoexcited carriers are generated in the semiconductor substrate 33a, the photoexcited carriers are accelerated by the voltage between the minute gaps 33c, and an instantaneous current flows, whereby the terahertz light L3 having a pulse width of about 1 picosecond. Is emitted.

Then, the terahertz light L3 (pulsed) radiated from between the minute gaps 33c is collimated by the super hemispherical lens 33b and enters the off-axis parabolic mirror 35.
In the off-axis parabolic mirror 35, the terahertz light L3 emitted from the terahertz light generating element 33 is reflected by two concave mirrors having a rotating paraboloid and focused toward the liquid cell 1 held and fixed to the holder 60. And then irradiate.

  The terahertz light L3 focused and irradiated toward the liquid cell 1 enters the liquid cell 1 through the through-hole 60b formed in one holder of the holder 60 and transmits through the liquid cell 1. At this time, the terahertz light L3 is focused and transmitted to the light collection area CA (see FIG. 1) with respect to the liquid (sample solution) injected into the liquid cell 1 (liquid flow path 2A). The diameter of the condensing area CA is, for example, about 3 mm.

The terahertz light L4 (pulse form) transmitted through the liquid cell 1 includes characteristic information on the sample solution.
Then, the terahertz light L4 transmitted through the liquid cell 1 enters the off-axis parabolic mirror 36.

  In the off-axis paraboloidal mirror 36, the terahertz light L 4 transmitted through the liquid cell 1 is reflected by two concave mirrors having a rotating paraboloid and enters the terahertz light detection element 47. The terahertz light L4 is focused and incident on the minute gap 47c via the super hemispherical lens 47b.

On the other hand, the probe light L11 split by the beam splitter 31 is reflected by the mirror 41 and enters the time delay device.
In the time delay device 42, the moving device is operated to move the movable stage 42a in the β direction indicated by the arrow in the drawing, and the probe light L12 given a time delay to the probe light L11 incident on the folding mirror 42b is reflected. . The time delay given by the time delay device 42 is that the repetition period of the probe light L11 is 10 MHz, so that a change of 0.3 mm in the optical path length of the incident light corresponds to a change of 1 picosecond.

  Then, the probe light L12 to which the time delay is given by the time delay device 42 is sequentially reflected in the order of the mirror 43, the mirror 44, and the mirror 45, and then converges on the terahertz light detection element 47 through the condenser lens 46. Incident. The probe light L12 incident on the terahertz light detection element 47 is focused on the minute gap (photoconductive antenna) 47c between the parallel transmission lines formed on the semiconductor substrate 47a and connected to the minute ammeter 47d.

  In the terahertz light detection element 47, when the probe light L12 is incident on the photoconductive antenna 47c in a state where the terahertz light L4 transmitted through the liquid cell 1 is incident on the photoconductive antenna 47c, the probe light L12 is incident. The photoexcited carriers generated in the semiconductor substrate 47a by the terahertz light L4 are accelerated by the oscillating electric field accompanying the terahertz light L4, and an instantaneous current proportional to the oscillating electric field flows. This instantaneous current is measured by a minute ammeter 47d. That is, time series data (time waveform of the oscillating electric field) depending on the time of the oscillating electric field of the terahertz light L4 is measured.

  Thus, in the terahertz light detecting element 47, an optical time delay is set between the probe light L12 and the terahertz light L4 by changing the timing at which the probe light L12 reaches the terahertz light detecting element 47 by the time delay. Thus, the time waveform of the oscillating electric field of the terahertz light L4 incident at a repetition period of 10 MHz is measured.

The time waveform of the electric field intensity of the terahertz light L4 measured by the terahertz light detecting element 47 is output to the current amplifier 50 and amplified, and then output from the current amplifier 50 to the lock-in amplifier 51.
In the lock-in amplifier 51, in order to reduce the noise component of the time waveform of the oscillating electric field amplified in the current amplifier 50, the synchronous detection is performed by applying modulation of several KHz with an optical chopper. Since the repetition period of the terahertz light L4 is 10 MHz with respect to the modulation of several KHz, the time waveform of the terahertz light L4 subjected to synchronous detection can be handled as a continuous waveform.

Then, the time waveform of the oscillating electric field of the terahertz light L4 subjected to synchronous detection is output to the computer 52.
In the computer 52, the time waveform of the oscillating electric field of the terahertz light L4 synchronously detected by the lock-in amplifier 51 is Fourier-transformed, so that the frequency dependence of the electric field strength of the terahertz light L4, the spectral transmission factor, the absorption factor, and the like. Data, that is, characteristic information of the sample solution. Thereafter, the physical and chemical properties of the sample solution can be explored by analyzing the obtained frequency characteristics and frequency dependence.

  Thus, the liquid cell 1 can be used directly connected to the liquid chromatography 61, the replacement of the sample solution is smooth, and the measurement operation can be easily performed. In addition to the terahertz analysis, the liquid cell 1 can be used for infrared spectroscopic analysis, Raman spectroscopic analysis, and the like. The sample solution used is not limited as long as it is a liquid. For example, organic solvents and blood.

Next, measurement data obtained by measuring the sample solution injected into the liquid cell 1 using the terahertz pulse spectrometer 100 will be described.
Measurement data is measured using the transmission measurement method as a solvent for the sample solution, which has weak absorption of terahertz pulsed light (small absorption coefficient) and strong absorption of terahertz pulsed light (large absorption coefficient). This will be described in the case of using water that is said to be difficult to do. Note that the majority of sample solutions show absorption coefficient values between ethanol and water.

  FIG. 4 is a graph showing the transmittance waveform obtained by subjecting the time waveform of the oscillating electric field to Fourier transform, and FIG. 5 is a graph showing the waveform of the absorption coefficient (spectral intensity). The waveform of the absorption coefficient shown in FIG. 5 is a graph obtained by calculating the reference transmittance of the liquid cell 1 as 1, based on the actually measured waveform data of the transmittance shown in FIG.

The horizontal axis of the graph shown in FIG. 4 represents the wave number (cm ⁻¹ ), the vertical axis represents the transmittance (%), and shows the signal transmittance up to a wave number of 100 cm ⁻¹ (corresponding to a frequency of 3.0 THz). Moreover, the diagram a1 in a graph shows the waveform in ethanol, and the diagram a2 shows the waveform in water.
On the other hand, the horizontal axis of the graph shown in FIG. 5 represents the wave number (cm ⁻¹ ), the vertical axis represents the absorption coefficient (cm ⁻¹ ), the diagram b1 in the graph shows the waveform in ethanol, and the diagram b2 The waveform in water is shown.

5 and 4, ethanol (diagrams b1 and a1) and water (diagrams b2 and a2) injected into the liquid cell 1 as liquids (sample solutions) can obtain signals. That is, by using the liquid cell 1, even water that is said to be difficult to measure using the transmission measurement method can be measured using the transmission measurement method.
Further, in FIG. 5, the alpha absorption coefficient when the liquid is water, is about 60cm ^-1 ~180cm ^-1, the absorption coefficient in ethanol alpha, is about 10cm ^-1 ~40cm ^-1.

Next, the shape of the liquid flow path 2A of the liquid cell 1 for obtaining a signal will be described.
The relationship between the incident light intensity and the transmitted light intensity of the liquid cell 1 is as follows, assuming that the incident light intensity I0, the liquid thickness L, the absorption coefficient α, and the transmitted light intensity I1 are based on the Lambert-Beer law. It is given by (2).
I1 = I0 × 10 ^−αL (2)
From the general formula (2), when the value of L is large, liquid absorption increases and transmitted light cannot be obtained. On the other hand, when the value of L is small, there is no difference between I1 and I0 and it is difficult to observe a signal.

Based on this general formula (2), it can be said that the shape of the liquid channel 2A for obtaining a signal should satisfy the following general formula (3).
(0.05 / (1-10 ^−αL )) ≦ A ≦ ((0.95 / (1-10 ^−αL )) (3)
However, the value of A in the general formula (3) is a condensing area CA (FIG. 1) in which the terahertz light L3 is focused and irradiated on the liquid (sample solution) injected into the liquid cell 1 (liquid channel 2A). (Ref.) Is a value represented by “Ss / St”, where St is the light collection area and St is the flow area of the spiral flow path portion 2a in the light collection area CA. That is, the value A is the ratio of the flow area Ss of the spiral flow path portion 2a to the light collection area St of the light collection area CA.

  The values of 0.05 and 0.95 in the general formula (3) mean that a signal transmittance of 5% to 95% is obtained when the reference of the liquid cell 1 is 100%. This value is a value considering noise generation from the viewpoint of reliability.

When the value of A (Ss / St) at which a signal of 5% or more is obtained is calculated based on the general formula (3) and the graph of the absorption coefficient α shown in FIG. 5, the following calculation results are obtained.
In the range of “α <10 cm ⁻¹ ”, “0.25 ≦ A ≦ 1”.
In the range of “10 cm ⁻¹ ≦ α ≦ 50 cm ⁻¹ ”, “0.08 ≦ A ≦ 1”.
In the range of “50 cm ⁻¹ <α ≦ 180 cm ⁻¹ ”, “0.05 ≦ A ≦ 1”.

From this, on the condition that a signal transmittance of 5% to 95% is obtained, the value of A (the ratio of the flow area Ss of the spiral flow path portion 2a to the light collection area St of the light collection area CA) Is preferably “0.05 ≦ A ≦ 1”. A more preferable range of “A ≦ 0.5” is within the range of “0.05 ≦ A ≦ 1” of the value of A.
The value of L used in this calculation is 100 μm (the depth of the recess (groove) that forms the liquid flow path 2A (the spiral flow path portion 2a)). That is, the depth of the recess that forms the spiral flow path portion 2a of the liquid cell 1 corresponds to the thickness L of the liquid. Therefore, hereinafter, the depth of the recess may be expressed as L.

Similarly, on the basis of the graph of the absorption coefficient α shown in the general formula (3) and FIG. 5, the liquid thickness L at which a signal of 5% or more is obtained, that is, the spiral flow path portion 2a of the liquid cell 1 is formed. When the depth of the recess is obtained, the following calculation result is obtained.
When the value of A is 1, the thickness L when the liquid is water is 50 μm or less (30 μm to 50 μm), and the thickness L when the sample solution is ethanol is 300 μm or less.
When the value of A is 0.5, the thickness L when the liquid is water is 100 μm or less, and the thickness L when the liquid is ethanol is 600 μm or less.

  From this, it is preferable that the liquid thickness L (depth L of the concave portion forming the spiral flow path portion 2a of the liquid cell 1) from which a signal of 5% or more is obtained is “30 μm ≦ L ≦ 600 μm”. It can be said. Within this L value range “30 μm ≦ L ≦ 600 μm”, if the value of L is about 100 μm, a signal of 5% or more can be easily obtained for any liquid (sample solution) containing any substance.

On the other hand, the cross-sectional area of the recess to form the liquid cell 1 liquid "flow path 2A, i.e. the cross-sectional area of the flow path, preferably .0.25Mm ² or more in the range of 0.0015mm ² ~0.25mm ² about (size If it is too small, the replacement of the sample solution requires a long time, and the replacement cannot be performed smoothly, and if it is 0.015 mm ² or less (too small), there is no problem in replacing the sample solution, but it is difficult to obtain a signal.
Based on this value, for example, when the depth L of the recess is 30 μm at the minimum cross-sectional area of 0.0015 mm ² , the width of the recess is 0.05 mm (50 μm), and the cross-sectional area is 0 at the maximum value. When the depth L of the concave portion at 25 mm ² is 100 μm, the width of the concave portion is 2.5 mm.

Here, the cross-sectional area of the preferred flow path (0.0015mm ² ~0.25mm ^2), from the relationship between the flow rate and pressure indicated in the following formula based on the formula of Hagen-Poazoiyu (4), the liquid (sample solution) It is a value calculated as an appropriate pressure range to be injected (discharged) into the liquid flow path 2A of the liquid cell 1 as 60 gf / cm ^{2 to} 4000 gf / cm ² .
Q = 5 × 10 ⁻⁵ × ((w × h ³ ) / l)) × P (4)
In general formula (4), Q represents the flow rate, P represents the pressure, w represents the width of the flow path, h represents the depth of the flow path, and l represents the length of the flow path.

Next, the spiral flow path portion 2a (see FIG. 1) that forms the liquid flow path 2A of the liquid cell 1 will be described.
In the liquid flow path 2A of the liquid cell 1, the flow path structure that appears as noise and the terahertz light that is linearly polarized light diffract-resonate when measuring the electric field strength of the liquid (sample solution) injected into the flow path. Therefore, it is required not to obtain a signal different from the molecular vibration.

  Therefore, in order to cope with this problem, the liquid flow path 2A of the liquid cell 1 has a spiral flow path portion 2a in which the flow paths are arranged in a spiral shape in a condensing area CA where the terahertz light is focused and irradiated. It is arranged. That is, it has an isotropic structure. This makes it possible to handle the liquid flow path 2A isotropically with respect to the polarized terahertz light, greatly suppressing the occurrence of diffraction resonance and obtaining a signal with higher accuracy.

In order to confirm the effect on the diffraction resonance due to the arrangement of the spiral flow path portion 2a, the following simulation was performed.
In the simulation, a double spiral having the same shape as the spiral flow path portion 2a formed in the liquid cell 1 (two spirals having a width of 100 μm are coupled at the substantially central portion of the spiral, and a pitch with the coupling portion as a base point of each other) Simulation of a mode in which a quartz plate with a thickness of 100 μm formed with a spiral through hole (corresponding to a spiral flow path) of 200 μm double spiral is sandwiched from both sides of a quartz plate with an infinite thickness. This was performed assuming that the liquid cell for use was irradiated with terahertz light (pulsed). The quartz plates arranged on both sides were made infinite in thickness in order to eliminate the occurrence of interference fringes. Further, the refractive index of quartz was 2.12 and the refractive index of air was 1.0, and both did not absorb light.

FIG. 6 shows the frequency characteristics of the transmittance at the interface of the spiral flow path (spiral through hole) obtained by this simulation.
FIG. 6A is a graph showing frequency characteristics of transmittance in the polarization direction parallel to the polarization axis of the terahertz light in the spiral flow path, and FIG. 6B is polarization of the terahertz light in the spiral flow path. It is a graph which shows the frequency characteristic of the transmittance | permeability in the polarization direction perpendicular | vertical to an axis | shaft.
In the graphs shown in FIGS. 6A and 6B, the horizontal axis represents wavelength (μm), the vertical axis represents transmittance (%), and shows the frequency characteristics of transmittance between wavelengths up to 1000 μm.

6 (a) and 6 (b), the frequency characteristics of transmittance in the polarization direction parallel to the polarization axis of the THz light shown by the diagram c1 in FIG. 6 (a), and the diagram in FIG. 6 (b). The frequency characteristic of the transmittance in the polarization direction perpendicular to the polarization axis of the THz light indicated by c2 draws substantially the same diagram. That is, the spiral flow path has an isotropic structure for polarized terahertz light.
Therefore, it can be said that the liquid cell 1 including the spiral flow path portion 2a having an isotropic structure can significantly suppress the occurrence of diffraction resonance and obtain a signal with higher accuracy.

Next, a manufacturing method of the liquid cell 1 will be described with reference to FIG.
First, a quartz plate (Z plate crystal) having a rectangular flat plate shape having a plate thickness of about 1.35 mm and a plane size of about 10 mm × 17 mm prepared in advance is prepared (preparation step). This quartz plate will later constitute translucent substrates 2 and 3.
Then, the prepared crystal plate shifts to a grooving process.

In the groove processing step, a groove having a predetermined shape is formed by using a blast processing method.
The groove to be formed becomes a liquid flow path 2A (a spiral flow path portion 2a, a liquid introduction flow path portion 2b, and an outflow flow path portion 2c) on one surface of one crystal plate (first crystal plate). A recess is formed. Moreover, the recessed part used as the liquid introduction port part 3a and the outflow port part 3b is formed on one surface of another one crystal plate (2nd crystal plate).

The blast processing method includes a masking process for forming a mask and a blast process.
In the masking step, a photosensitive dry film is laminated on the surface of the first quartz plate. Then, the photosensitive dry film is exposed by superimposing a mask formed so as to remove the region other than the previously prepared liquid flow path 2A on the upper surface of the photosensitive dry film. In the exposure, ultraviolet rays are irradiated onto the mask using an exposure apparatus. The width of the liquid channel 2A formed on the surface of the first quartz plate is approximately 100 μm.

  Then, development is performed. The development is performed by putting the first crystal plate on which the photosensitive dry film has been exposed into a developing device and spraying a developer from the spray nozzle onto the exposed photosensitive dry film. As the developer, for example, an aqueous sodium carbonate solution having a concentration of about 0.1% to 0.3% and a liquid temperature of about 30 ° C. is used. Thereby, a large number of photosensitive dry films having a shape similar to the flow channel shape of the liquid flow channel 2A remain on the surface of the first quartz plate.

Also for the second quartz plate, a mask formed so as to remove the region other than the liquid inlet port portion 3a and the outlet port portion 3b is superposed on the upper surface of the photosensitive dry film laminated on the surface, and the photosensitive dry film is laminated. After the film is exposed, development is performed in the same manner as the first quartz plate. In addition, the width | variety of the liquid introduction port part 3a and the outflow port part 3b formed in the surface of a 2nd crystal plate is about 600 micrometers.
Then, after rinsing and drying with an acidic aqueous solution, the process proceeds to a blasting process.

In the blasting process, the first quartz plate and the second quartz plate on which the photosensitive dry film is developed are blasted using a microblasting device.
Blasting is performed by using a microblasting device to spray an abrasive together with compressed air from the blast nozzle onto the surfaces of the first quartz plate and the second quartz plate on which the photosensitive dry film has been developed. The quartz plate in the area other than the conductive dry film is removed by the brittle fracture principle. Examples of the abrasive include silicon carbide, alumina, glass beads, and stainless powder. Moreover, it is preferable to use the fine particle | grains of about # 600- # 6000 (particle diameter: 4 micrometers-25 micrometers) prescribed | regulated to JIS1998 as the particle size of an abrasive | polishing agent.

The first quartz plate performs 20-pass processing at a moving speed of about 50 mm / sec while spraying an abrasive with a jet pressure of about 0.15 MP on the surface of the quartz plate. As a result, a liquid channel 2A composed of a spiral channel portion 2a having a depth of about 100 μm and a width of about 100 μm, a liquid introduction channel portion 2b, and an outflow channel portion 2c is formed on the surface of the first quartz plate. The translucent base material 2 is completed.
On the other hand, the second crystal plate is processed by 30 passes at a moving speed of about 50 mm / sec while spraying an abrasive with a spray pressure of about 0.35 MP on the surface of the crystal plate. A liquid inlet portion 3a and an outlet portion 3b having a thickness of about 600 μm are formed.

And it transfers to a mask peeling process.
In the mask peeling step, the blasted first crystal plate and second crystal plate are left in water having a water temperature of about 25 ° C. to 50 ° C. for one hour to remove the photosensitive dry film.
Thereby, the translucent base material 2 and the translucent base material 3 are completed.

Although description has been omitted, the liquid crystal flow path 2A is formed in a region excluding the concave portion to be the liquid flow path 2A simultaneously with the formation of the concave section to be the liquid flow path 2A on the processed surface of the first crystal plate. A large number of adhesive dropping grooves are formed in a matrix so as not to get caught in the recesses. Therefore, the depth of the many adhesive dropping grooves to be formed is also about 100 μm. As described above, the adhesive dropping groove is used to remove excess adhesive when bonding the completed translucent substrate 2 and translucent substrate 3 in the subsequent translucent substrate bonding step. It is a concave part (groove) that drops into the adhesive and stores the adhesive.
And it transfers to a translucent base material joining process.

In the translucent base material joining step, the translucent base material 2 and the translucent base material 3 completed in the groove processing step (masking step and blasting step) by the blasting method are bonded and fixed.
In the adhesive fixation, a thermosetting adhesive is applied to the surface of the translucent substrate 2 on which the liquid flow path 2A is formed, for example, using a screen printing method. And the liquid introduction port part 3a and the outflow port part 3b were formed by making the outer shape of the translucent base material 3 substantially coincide with the surface of the translucent base material 2 coated with the thermosetting adhesive. Overlapping surfaces.

  Thereafter, the superposed translucent base material 2 and translucent base material 3 are put into a heating furnace set at a temperature of about 75 ° with pressure applied from both outer sides for about 2.5 hours. The thermosetting adhesive is cured.

At the time of such adhesive fixing, by pressing the translucent substrates from both sides, the excess adhesive applied to the surface of the translucent substrate 2 is dropped into the adhesive dropping groove. The translucent substrate 2 and the translucent substrate 3 are bonded and fixed by a cured adhesive layer having a thickness of about several μm. As the adhesive, an ultraviolet curable adhesive may be used in place of the thermosetting adhesive.
And it transfers to a microtube attachment process.

In the microtube mounting step, the microtube 4 (4a, 4b) is inserted into each hole of the liquid introduction port portion 3a and the outflow port portion 3b, and the translucent substrate 2 and the silicone adhesive 5 are used. Adhering and fixing to the translucent substrate 3. The microtube 4 is bonded and fixed at a position where at least a space in which a liquid can flow is formed between the inner wall of each hole to be inserted and the tip of the tube.
Thereby, the liquid cell 1 is completed.

  In the completed liquid cell 1, the microtube 4 a is coupled to the liquid chromatography 61, attached to the holder 60 of the terahertz pulse spectrometer 100, and the liquid separated for each component in the liquid chromatography 61 is sequentially used as a sample solution. The time waveform of the oscillating electric field of the sample solution can be measured by injecting the liquid cell 1 into the liquid channel 2A.

  In the above embodiment, even if it is a form mentioned as the next modification, it is possible to obtain the same effect as the embodiment.

(Modification 1)
The liquid flow path formed on one surface of the translucent substrate 2 of the liquid cell 1 is not limited to the liquid flow path 2A arranged in a spiral shape shown in FIG.
FIG. 7 is a front view schematically showing another configuration of the liquid cell for terahertz spectroscopy, and FIG. 8 is a front view schematically showing still another configuration of the liquid cell for terahertz spectroscopy. The liquid cell shown in FIGS. 7 and 8 is the same as the liquid cell 1 shown in FIG. 1 except for the front shape of the liquid channel, and the description other than the liquid channel is omitted or simplified. Further, for the sake of clarity of the configuration, the liquid flow path is indicated by a solid line, and other components are indicated by a two-dot chain line.

In FIG. 7, the liquid flow path 22A of the liquid cell 20 is composed of a single flow path including a rectangular spiral flow path portion 22a, a liquid introduction flow path portion 22b, and an outflow flow path portion 22c.
The rectangular spiral channel portion 22a is joined at a substantially central portion of two rectangular spirals, and a double rectangular spiral having a predetermined interval (pitch) is formed around the left, for example, with the joint as a base point. ing. The predetermined interval between the double rectangular spirals is, for example, 200 μm. The rectangular spiral channel portion 22a is formed in a region including at least a condensing area CA (a circular inner region indicated by a two-dot chain line in the drawing) of the terahertz light irradiated from the terahertz pulse spectrometer 100.

In addition, the rectangular spiral channel portion 22a (double rectangular spiral) is coupled to the liquid guide channel portion 22b that has one end extending to the short side along one long side of the rectangular shape. The end is coupled to the outflow channel 22c extending to the same short side along the other long side of the rectangular shape, like the liquid guide channel 22b.
The liquid cell 20 configured as described above can be used in the same manner as the liquid cell 1. Further, the same effect as the liquid cell 1 can be obtained.

On the other hand, in FIG. 8, the liquid flow path 12A of the liquid cell 10 is configured by a single flow path including a repetitive line-shaped flow path portion 12a, a liquid introduction flow path portion 12b, and an outflow flow path portion 12c. Yes.
The repetitive line-shaped flow path portion 12a has a rectangular outer shape in a region including at least a condensing area CA (a circular inner region indicated by a two-dot chain line in the drawing) of the terahertz light irradiated from the terahertz pulse spectrometer 100. It is formed in a shape that is repeatedly folded at a predetermined interval (pitch) in a direction along the long side of the shape. The predetermined interval is, for example, 200 μm.

Further, the repetitive line-shaped channel portion 12a is coupled to the liquid introduction flow channel portion 12b whose one end extends to the short side along one long side of the rectangular shape, and the other end is the liquid introduction flow channel portion. Similarly to 12b, it is coupled to the outflow channel portion 12c extending to the same short side along the other long side of the rectangular shape.
The liquid cell 10 configured as described above can obtain the same effects as the liquid cell 1. However, in the case of using the liquid cell 10, in order to avoid diffraction resonance, the direction in which the repetitive line-shaped flow path portion 12a repeatedly turns is determined in consideration of the polarization direction of the irradiated terahertz pulse light. It is necessary to set.

(Modification 2)
In the manufacturing method of the liquid cell 1, the blast processing method is used for the groove processing step for forming the concave portion to be the liquid flow path 2 </ b> A on one surface of the first crystal plate, but the blast processing method is used instead. Thus, an etching method can be used.

The grooves formed by using the etching method are formed on one surface of a single crystal plate (first crystal plate) on the liquid flow path 2A (the spiral flow path portion 2a, the liquid introduction flow path portion 2b, the outflow flow. A recess to be a path portion 2c) is formed. Moreover, the recessed part used as the liquid introduction port part 3a and the outflow port part 3b is formed on one surface of another one crystal plate (2nd crystal plate).
The etching method includes an etching mask forming step and an etching step for performing an etching process.

  In the etching mask forming step, first, a Cr film as a metal film is formed with a thickness of about 0.1 μm on the surface of the crystal plate (the first crystal plate and the second crystal plate) using a sputtering method. This Cr film functions as a mask when performing an etching process. Then, a resist film made of a thermoplastic resin such as PMMA (polymethyl methacrylate) is formed on the surface of the Cr film by using a spin coating method.

Then, the resist film formed on the Cr film is irradiated with light or an electron beam to form a liquid channel 2A (a spiral channel portion 2a, a liquid guide channel portion 2b) formed on the surface of the first crystal plate. The shape of the outflow channel 2c) is drawn. Thereby, the drawing part irradiated with light or an electron beam becomes soluble with respect to a chemical reaction.
Then, the resist film in the drawing portion and the Cr film formed under the resist film are etched by a wet etching method to form a positive film made of a Cr film similar to the shape of the liquid flow path 2A on the surface of the first quartz plate. A mold etching mask is formed.
And it transfers to an etching process.

In the etching step, the first crystal plate on which the etching mask is formed is etched using a wet etching apparatus.
The etching process takes about 100 minutes. By this etching process, a liquid flow path 2A composed of a spiral flow path portion 2a having a depth of about 100 μm and a width of about 100 μm, a liquid introduction flow path portion 2b, and an outflow flow path portion 2c is formed on the surface of the first quartz plate. It is formed.

And it transfers to a peeling process.
In the peeling process, the resist film is removed with a KOH aqueous solution, and the Cr mask is removed with a Cr etching solution. Thereby, the translucent base material 2 is completed.

  Similarly to the first crystal plate, the second crystal plate is formed by irradiating the resist film formed on the Cr film with light or an electron beam to form the liquid introduction port portion 3a and the outflow port portion 3b. After drawing the shape, wet etching is performed to form a positive etching mask made of a Cr film similar to the liquid introduction port portion 3a and the outflow port portion 3b on the surface of the second crystal plate. Then, by performing an etching process or the like, the translucent substrate 3 in which the liquid introduction port portion 3a and the outflow port portion 3b having a depth of about 600 μm are formed is completed. Note that the etching processing time is about 600 minutes.

  Since the liquid cell 1 grooved using such an etching method has a higher processing resolution than when the blasting method is used, the value of A (the spiral flow with respect to the light collection area St of the light collection area CA). The ratio of the flow path area Ss of the path portion 2a can be set large, and a signal with higher accuracy can be obtained.

(Modification 3)
The case where quartz is used as the translucent base materials 2 and 3 that transmit terahertz light has been described. However, instead of quartz, sapphire, polyethylene, polypropylene, fluororesin, polymethylpentene resin, diamond, and translucent ceramic Lumicera (registered trademark, Murata Manufacturing Co., Ltd.) can be used. Alternatively, a liquid cell for terahertz spectroscopic analysis may be formed by combining these layers.

(Modification 4)
Although the case where a Z-plate crystal is used for the translucent substrates 2 and 3 has been described, an X-plate crystal or a Y-plate crystal may be used. However, it is necessary to select appropriately according to the processing method of the recesses (grooves) formed on the surfaces of the translucent substrates 2 and 3. For example, when the Y plate crystal is formed as a translucent substrate using an etching method, the etching rate is low.
In addition, although the example which laminates | stacks two translucent base materials was shown in said Example, not only that but a translucent base material of 3 or more sheets is laminated | stacked, and the liquid cell for terahertz spectroscopy analysis is set. It may be formed.

(A) is a front view which shows typically the structure of the liquid cell for terahertz spectroscopy based on this embodiment, (b) is sectional drawing of the liquid cell for terahertz spectroscopy in the AA cross section of (a). The perspective view which shows typically the antireflection structure formed in the surface of a translucent base material. The schematic diagram which shows schematic structure of a terahertz pulse spectroscopy measuring device. The graph which shows the waveform of the transmittance | permeability obtained by giving a Fourier transform to the time waveform of an oscillating electric field. The graph which shows the waveform of an absorption coefficient. (A) is a graph which shows the frequency characteristic of the transmittance | permeability in the polarization direction parallel to the polarization axis of the terahertz light of a spiral flow path, (b) is a polarization direction perpendicular | vertical to the polarization axis of the terahertz light of a spiral flow path. The graph which shows the frequency characteristic of the transmittance | permeability in. The front view which shows typically another structure of the liquid cell for terahertz spectroscopy analysis. The front view which shows typically another structure of the liquid cell for terahertz spectroscopy analysis.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,10,20 ... Liquid cell (liquid cell) for terahertz spectroscopy analysis, 2 ... Translucent base material, 2A, 12A, 22A ... Liquid flow path, 2a ... Spiral flow path part, 2b, 12b, 22b ... Guide Liquid channel part, 2c, 12c, 22b ... Outflow channel part, 3 ... Translucent base material, 3a ... Liquid introduction port part, 3b ... Outlet part, 4 (4a, 4b) ... Micro tube, 5 ... Adhesion Agent, 12a ... repetitive line-shaped channel portion, 22a ... rectangular spiral channel portion, 33 ... terahertz light generating element, 35, 36 ... parabolic mirror, 42 ... time delay device, 47 ... terahertz light detecting element, 60 ... Holder, 61 ... Liquid chromatography, 100 ... Terahertz pulse spectroscopic measurement device.

Claims (6)

A liquid cell for terahertz spectroscopy,
The liquid cell for terahertz spectroscopic analysis is formed by joining a translucent substrate that transmits terahertz light, and has a liquid flow path in which a liquid flows along an interface of the translucent substrate,
A liquid cell for terahertz spectroscopy, comprising a liquid channel portion having an isotropic structure with respect to the polarized terahertz light in a region including at least a condensing area where the terahertz light is condensed. The terahertz spectroscopic liquid cell according to claim 1,
The liquid channel portion having the isotropic structure is a spiral channel formed by a double spiral in which two spirals are joined at a substantially central portion of the spiral, and the joint is a base point of each other. A liquid cell for terahertz spectroscopic analysis. A liquid cell for terahertz spectroscopy according to claim 1 or claim 2,
On the surface in the plate thickness direction of the laminate of the laminated translucent substrate,
For terahertz spectroscopic analysis, comprising an antireflection function in which a large number of protrusions having an aspect ratio represented by the following general formula (3) are arranged in an array with a period P of terahertz wavelength or less Liquid cell.
1.5 <(H / P) (3)
However, H represents the height from the bottom of the protrusion to the apex, and P represents the period. It is a liquid cell for terahertz spectroscopy analysis according to any one of claims 1 to 3,
The liquid cell for terahertz spectrometry, wherein the light-transmitting substrate is made of any one of crystal, sapphire, polyethylene, polypropylene, fluororesin, polymethylpentene resin, diamond, and light-transmitting ceramic. A method for producing a liquid cell for terahertz spectroscopy, comprising: a transparent base material that transmits terahertz light; and a liquid channel through which a liquid flows along an interface of the transparent base material. ,
A masking step of laminating a photosensitive film on the surface of the translucent substrate, and forming a mask of the photosensitive film having a shape similar to the liquid flow path on the surface of the translucent substrate;
A blasting step of injecting an abrasive onto the surface of the translucent substrate masked with the photosensitive film;
A mask peeling step for removing the mask;
A translucent base material joining step of laminating the translucent base materials and joining each other;
A method for producing a liquid cell for terahertz spectroscopic analysis, comprising: A method for producing a liquid cell for terahertz spectroscopy, comprising: a transparent base material that transmits terahertz light; and a liquid channel through which a liquid flows along an interface of the transparent base material. ,
On the surface of the translucent substrate, a metal film and a resist film are formed in order from the surface, and the resist film is irradiated with light or an electron beam to draw a shape similar to the liquid flow path. An etching mask forming step of forming an etching mask by etching;
An etching step of etching the translucent substrate on which the etching mask is formed;
A peeling step of peeling the resist film and the etching mask;
A translucent base material joining step of laminating the translucent base materials and joining each other;
A method for producing a liquid cell for terahertz spectroscopic analysis, comprising:

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