JP4636917B2 - Sample holding device, sample detection apparatus and sample detection method using the same - Google Patents

Description

  The present invention relates to a technique for detecting a specimen using electromagnetic waves, and more particularly to an apparatus and method for detecting a specimen from a change in the propagation state of electromagnetic waves in a transmission line.

In recent years, with the development of means for generating and detecting terahertz waves (30 GHz to 30 THz) from millimeter waves, technology using terahertz waves has attracted attention. For example, specimens such as a technique for imaging as a safe fluoroscopic inspection device that changes to X-rays as an application field of terahertz waves, a spectroscopic technique for examining a binding state by examining an absorption spectrum and a complex dielectric constant inside a substance, and a biomolecule analysis technique It has been attracting attention and developed as a non-contact inspection technology. Non-Patent Document 1 discloses a technique for irradiating a substance with a terahertz wave using a spatial optical system and detecting the terahertz wave transmitted through the substance.
Chemical Physics Letters 332 (2000) 389-395

  On the other hand, sample detection technology is assumed to be able to move the device only with a very small amount of sample due to downsizing of the device itself or difficulty in obtaining the sample itself. Even in such a case, sufficient detection sensitivity is required. Yes. However, in the technique of Non-Patent Document 1, a certain amount or more of the sample is necessary, and it may be difficult to obtain sufficient detection sensitivity when detecting a small amount of sample.

  Therefore, the present invention provides a sample holding device for obtaining sufficient detection sensitivity even with a small amount of sample, a sample detection apparatus and a sample detection method using the device.

Therefore, in order to solve the above-described object, the device of the present invention has a substrate, an input antenna for allowing electromagnetic waves in a frequency range of 30 GHz to 30 THz to enter from space, and a transmission line for propagating the electromagnetic waves from the input antenna. And an output antenna for radiating electromagnetic waves from the transmission line to space, and a specimen holding unit for holding the specimen and causing the specimen to interact with the electromagnetic waves propagating through the transmission line, The input antenna, the transmission line, and the output antenna are formed to be connected to a substrate so that the plane of polarization of electromagnetic waves incident on the input antenna and the plane of polarization of electromagnetic waves radiated from the output antenna are different. It is configured .

  According to the present invention, by confining an electromagnetic wave in a transmission line, it is possible to efficiently interact the specimen and the electromagnetic wave, and even a very small amount of specimen can be detected.

  Therefore, the present invention is configured as follows in order to achieve the above object.

  A device for holding a sample includes a transmission line for transmitting electromagnetic waves, a sample holding unit for holding a sample in the transmission line, a spatial coupler for inputting electromagnetic waves from space, and the transmission line. A spatial coupler for outputting the propagated electromagnetic wave to the space, and the spatial coupler for inputting the electromagnetic wave from the space is connected to the transmission line.

  Here, the spatial coupler has a function of efficiently entering electromagnetic waves from space or emitting electromagnetic waves efficiently into space. For example, there are couplers using antennas and surface plasmons. The antenna can also be formed by changing the width of the microstrip line. The shape of the antenna can be designed as necessary, such as a square, a rectangle, a circle, and an ellipse. Transmission lines include microstrip lines and coplanar lines, and are preferably formed of a conductive material such as Au, Ag, Cu, or Pt. Further, it is more preferable that the transmission line is bent at 90 degrees in the middle. The specimen can be not only solid and liquid, but also gas if high-pressure gas that can interact with electromagnetic waves is held in the specimen holder. The specimen holding part is a part for holding the specimen described above, and is preferably present in the transmission line. However, since the electromagnetic wave spreads not only in the transmission line but also outside, the specimen holding part is used as the transmission line. You may provide in the vicinity. Or the effect which the change of the propagation characteristic of electromagnetic waves produces is anticipated also with the form which affixes specimen itself on a transmission line. For example, as shown in FIG. 4, a gap 33 is provided in the center of the specimen holder 32 made of an insulating material, and the specimen is dropped into the gap and held in contact with the transmission line.

  The sample detection apparatus includes the above-described sample holding device, a generation unit for generating electromagnetic waves, and a detection unit for detecting electromagnetic waves. By interacting the electromagnetic wave propagating in the transmission line with the specimen held in the specimen holding part, the propagation state of the electromagnetic wave in the transmission line is changed, and the change of the specimen is compared with the case where the specimen is not held from the change. Perform detection. Furthermore, it is preferable that the specimen detection apparatus includes a polarizing filter. Thereby, noise can be removed and detection with higher accuracy is possible. As the electromagnetic wave, it is preferable to use one having a frequency range of millimeter wave to terahertz wave (30 GHz to 30 THz). Examples of the generator for generating electromagnetic waves include a photoconductive element, a parametric generator, a quantum cascade laser, and a backward traveling wave tube (BWO). As the detection unit for detecting electromagnetic waves, a photoconductive element, an EO crystal, a bolometer, a superconducting tunnel junction element, or the like can be considered. The polarizing filter has a function of separating an electromagnetic wave having a certain polarization plane and an electromagnetic wave inclined by 90 degrees in the polarization plane. For example, a wire grid is used.

It is preferable that the polarization plane of the electromagnetic wave having a strong coupling efficiency with the space of one spatial coupler is different from the polarization plane of the electromagnetic wave having a strong coupling efficiency with the space of the other spatial coupler.
Or, among the spatial couplers, the polarization plane of the electromagnetic wave having a strong coupling efficiency with the space of one spatial coupler and the polarization plane of the electromagnetic wave having a strong coupling efficiency with the space of the other spatial coupler may differ by 90 degrees. preferable.

  Hereinafter, an embodiment of the specimen detection apparatus using a terahertz wave as an electromagnetic wave will be described more specifically with reference to FIG. Of course, the present invention is not limited to these examples. The sample detection apparatus includes a transmission line 4 for transmitting electromagnetic waves, at least two spatial couplers 3 and 6, and a sample holding unit 5 for holding the sample on the transmission line. In the coupler, an electromagnetic wave 2 is input to one spatial coupler 3 from the space, and a specimen holding device that outputs the electromagnetic wave 7 from the other spatial coupler 6 to the space, the electromagnetic wave generator 1, the polarizing filter 8, and the electromagnetic wave detection It consists of part 9.

  In the sample holding device, the spatial coupler has a role as an input / output of electromagnetic waves. On the transmission line, there is a sample holder 5 which is a sample holding mechanism. The configuration of the sample holder 5 is not particularly limited as long as the sample and the electromagnetic wave can stably interact with each other. For example, as shown in FIG. 4, a gap 33 is provided in the center of the sample holder 32 made of an insulating material. The specimen is held while the specimen is dropped onto the portion and brought into contact with the transmission line. A terahertz wave is incident on one of the spatial couplers of the specimen holding device from the electromagnetic wave generation unit, propagates on the transmission line, and then radiates from the other spatial coupler, and is output from the spatial coupler of the output portion by the polarizing filter. The radiated electromagnetic wave is separated from the electromagnetic wave and the electromagnetic wave whose polarization plane is different by 90 degrees, and the electromagnetic wave radiated from the spatial coupler of the output portion is detected by the electromagnetic wave detection device. The specimen holding part extracts the changes in the propagation characteristics of the electromagnetic wave, such as the propagation loss of the electromagnetic wave, the phase delay, and the change in the characteristic absorption spectrum. Can be detected. In this embodiment, the polarization planes of electromagnetic waves having strong coupling efficiency with the spaces of both space couplers are particularly shifted. This is to shift the polarization of the electromagnetic wave radiated from the spatial coupler of the output part with respect to the polarization of the electromagnetic wave noise caused by reflection from the spatial coupler or transmission line of the input part in the input electromagnetic wave. Thereby, electromagnetic wave noise due to reflection can be removed, and interference can be prevented. That is, the electromagnetic wave radiated from the spatial coupler at the output portion can be distinguished from the noise, and the S / N is improved so that the interaction between the minute amount of the specimen and the electromagnetic wave can be detected.

  A second embodiment according to the present invention is illustrated in FIG. In the specimen detection device used in the present invention, a high-frequency insulating material 14 is applied to the specimen holding device after vapor-depositing a metal on the high-resistance Si substrate 13 as a ground plane. As the high-frequency insulating material, various substances such as BCB (benzocyclobutene), polyimide, and polysilane are conceivable. Metal lines such as patch antennas 15a and 15b as space couplers and a microstrip line 17 as a transmission line are formed on the high-frequency insulating material by patterning. The method applies a photoresist over a high frequency insulating material. Exposure and development are performed, and the photoresist is patterned and baked. Metal (titanium, gold laminated structure, etc.) is deposited, and the photoresist is peeled off by lift-off. After the transmission line and the patch antenna are formed, the specimen holding unit 18 is formed by coating, baking, and etching using an insulating material.

  FIG. 4 illustrates the sample holder. The specimen is held by dropping the specimen into the gap. Note that the specimen holding mechanism is not limited to this form as long as it can interact with electromagnetic waves stably. In this way, the device is completed. The typical size of the patch antenna is about 100 μm as the wavelength order of the terahertz wave, and the length of the transmission line is about 1 mm in consideration of the loss of electromagnetic waves in the transmission line. The width of the transmission line is adjusted so as to achieve impedance matching with the patch antenna by setting the impedance value of the transmission line from three values of the thickness of the high-frequency insulating material and the dielectric constant of the high-frequency insulating material. In order to achieve impedance matching as shown in FIG. 3, a cut 23 may be made in the patch antenna 22. In order to narrow the radiation distribution from the antenna, a slit 16a, 16b may be provided in the center of the antenna. By using an element having only the function of propagating the terahertz wave in this way, the cost of the specimen holding device as the exchange unit can be reduced.

  In the second embodiment, the transmission line is bent as shown in FIG. This is due to the following reason. The terahertz wave has a wavelength of about 300 μm at 1 THz and does not have spatial resolution and light beam straightness as light. The size of the antenna is about 100 μm, and there is a possibility that the terahertz wave cannot be condensed and irradiated on the antenna portion. At that time, there is a risk of interference from radiation from the antenna at the output portion and noise due to reflection (from the transmission line or the antenna at the input portion) that could not be incident on the input portion. The direction of polarization of the electromagnetic wave radiated from the patch antenna is the direction connecting the transmission line (feeding point) and the central portion of the patch antenna. The transmission line part is bent 90 degrees and the polarization direction of the electromagnetic wave is shifted 90 degrees in advance. If you do, there will be no interference with the previous noise. By preventing this interference, the optical axis of the terahertz wave can be easily adjusted in the optical system, and simplification of the optical system can be achieved. Further, by preventing noise and interference, the S / N is improved, and it becomes possible to detect a smaller amount of the interaction between the specimen and the electromagnetic wave.

  After the terahertz wave incident on the patch antenna 15 a from the terahertz wave generation device 10 propagates through the transmission line and interacts with the sample held by the sample holding unit 18, the terahertz wave is emitted from the patch antenna 15 b and passes through the polarization filter 19. It is detected by the terahertz wave detection device 20. As an example of generation of a terahertz wave, there is a method using a photoconductive element and an optical pulse. The configuration is shown in FIG. The photoconductive element has a configuration in which an antenna structure 53 is provided on a photoconductive film 52. The photoconductive film 52 is made of a material having a high carrier mobility, a short carrier life, and a high withstand voltage (for example, LT-GaAs). When a DC bias voltage 56 is applied to the gap portion 54 of the antenna structure 53 and the gap portion is irradiated with an optical pulse 57 (femtosecond laser), a terahertz pulse 55 is emitted.

  A wire grid etc. can be considered as an example of a polarizing filter. This is a thin metal wire line periodically arranged at regular intervals. When the distance between metal wire lines is sufficiently shorter than the wavelength of the terahertz wave (up to 30 μm), it is perpendicular to the metal wire lines. Electromagnetic waves having a polarization plane in any direction are transmitted, and electromagnetic waves having a polarization plane in a direction perpendicular to the metal wire are absorbed by the metal and do not transmit. Using this function, it is possible to separate electromagnetic waves having different 90-degree polarization planes.

  In other words, by arranging the wire grid so that the plane of polarization of the electromagnetic wave from the spatial coupler of the output portion is perpendicular to the metal wire line of the wire grid, the electromagnetic wave from the spatial coupler of the output portion and the electromagnetic wave are polarized. It is possible to separate electromagnetic waves inclined by 90 degrees on the wavefront.

  A third embodiment of the present invention is shown in FIG. FIG. 5 shows only the pattern on the high frequency insulating material. The description of the overlapping parts with the first and second embodiments is omitted. As shown in the figure, 43 printed dipole antennas are used for the spatial coupler of the output portion. A printed dipole antenna is provided through the transmission line and the gap. The length L of the printed dipole antenna is about 100 μm, and the printed dipole antenna has a resonance structure with the gap as a feeding point, and an electromagnetic wave in a band near the wavelength where L is a half wavelength is radiated from the printed dipole antenna. Also in this case, the radiated electromagnetic wave is 90 degrees different from the noise caused by reflection from the transmission line and the spatial coupler of the input part, and the effect of preventing interference with noise by using a polarizing filter. I can expect. As a result, the optical axis of the terahertz wave can be easily adjusted in the optical system as in the first embodiment, and the simplification of the optical system can be achieved. Further, by preventing noise and interference, the S / N is improved, and it becomes possible to detect a smaller amount of the interaction between the specimen and the electromagnetic wave.

Embodiment relating to one specimen detection apparatus in the present invention Overall view of the sample detection apparatus of the first embodiment Enlarged view of antenna The figure which showed the sample holding part in a transmission line Pattern diagram of the sample detection apparatus of the second embodiment Schematic diagram of terahertz wave generation by photoconductive element

Explanation of symbols

1, 10 Electromagnetic wave (terahertz wave) generator 2, 7, 11, 12 Electromagnetic wave (terahertz wave)
3, 6 Spatial coupler 13 Substrate 14 High-frequency insulating material 15a, 15b, 22, 41 Patch antenna 16a, 16b Slit 4, 17, 21, 31, 42, 51 Transmission line 5, 18, 32 Specimen holder 8, 19 Polarization Filters 9 and 20 Electromagnetic wave (terahertz wave) detector 23 Notch 33 Air gap 43 Printed dipole antenna 52 Photoconductive film 53 Dipole antenna 54 Gap portion 55 Terahertz pulse 56 Bias voltage 57 Optical pulse (femtosecond laser)

Claims (5)

A substrate,
An input antenna for an electromagnetic wave in a frequency range from 30 GHz to 30 THz to enter from a space;
A transmission line for propagating electromagnetic waves from the input antenna ;
An output antenna for radiating electromagnetic waves from the transmission line to space;
A sample holding unit for holding the sample and causing the sample to interact with the electromagnetic wave propagating through the transmission line,
The input antenna , the transmission line, and the output antenna are formed connected to a substrate ,
A device configured such that a plane of polarization of an electromagnetic wave incident on the input antenna is different from a plane of polarization of an electromagnetic wave radiated from the output antenna . By bending 90 degrees the transmission line, according to claim wherein the input enters the antenna electromagnetic wave polarization plane of the radiating from the polarization plane and the output antenna is characterized that you have been configured differently 90 degrees The device according to 1 . By configuring the output antenna in printed dipole antenna, the polarization of an electromagnetic wave radiated from the polarization plane and the output antenna of the electromagnetic wave incident on the input antenna, and features that you have been configured differently 90 degrees The device of claim 1 . A device according to any one of claims 1 to 3 ,
A generator for generating an electromagnetic wave incident on the input antenna ;
And a detection unit for detecting electromagnetic waves radiated from the output antenna . A device according to any one of claims 1 to 3 ,
A specimen detection apparatus comprising: a polarization filter for separating the electromagnetic wave radiated from the output antenna for each electromagnetic wave having different polarization planes.

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