Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
  • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
  • G01N21/3581—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using far infrared light; using Terahertz radiation
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
  • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
  • G01N21/3577—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing liquids, e.g. polluted water

Definitions

• the present invention relates to a technique for detecting a change in propagation state of an electromagnetic wave passed through an object to be inspected or examined (hereinafter, simply referred to as "object"), and more particularly to a detection apparatus for detecting a change in propagation state ⁇ of an electromagnetic wave passed through an object to perform measurement, sensing and/or analysis of the object.
• techniques now under development in application fields of the terahertz-wave include an imaging technique using a safe fluoroscopic apparatus alternative to an X-ray apparatus, a spectral technique for obtaining an absorption spectrum or complex dielectric constant of a substance to examine a bonding state therein, a technique for analyzing biomolecules, a technique for estimating a carrier concentration or mobility.
• a method of spectroscopically analyzing a substance using the terahertz-wave there has been known a method of irradiating a substance to be analyzed with the terahertz-wave to obtain a spectrum of a transmitted or reflected terahertz-wave.
• water has a number of very strong absorption spectrums in a frequency range of 30 GHz to 30 THz. Therefore, the terahertz-wave is almost shielded by, for example, a container with a thickness of 1 mm containing liquid water. Thus, it is relatively difficult to obtain an information of a substance contained in water by means of a terahertz- wave passed through the water.
• a terahertz-wave exited from a third surface of the prism is detected by a detector, and a sample is disposed on the second surface so as to interact with an evanescent wave of the terahertz- wave which is generated upon the total reflection of the terahertz-wave by the second surface, thereby spectroscopically analyzing the sample.
• this method it is possible to analyze a sample in a form of solid, powder, liquid, or the like.
• a detection apparatus for detecting an electromagnetic wave passed through an object comprising a transmission line for transmitting an electromagnetic wave therethrough; and a detector for detecting an electromagnetic wave passed through an object, wherein the transmission line has a gap for disposing the object therein.
• a detection method of detecting an electromagnetic wave passed through an object comprising the steps of disposing an object in a gap of a transmission line for transmitting an electromagnetic wave therethrough; and detecting an electromagnetic wave passed through the object.
• a transmission line for transmitting an electromagnetic wave therethrough for use-in a detection apparatus for detecting an electromagnetic wave passed through an object, comprising a gap for disposing an object in the transmission line.
• FIGS. IA and IB are schematic views showing a detection apparatus in accordance with a preferred embodiment of the present invention, and FIG. IA is a plan view and FIG. IB is a perspective view;
• FIG. 2 is a schematic diagram showing a detection apparatus in accordance with a preferred embodiment of the present invention.
• FIGS. 3A, 3B, and 3C are schematic graphical representations each showing a change in state of an electromagnetic wave obtained by a detection apparatus in accordance with a preferred embodiment of the present invention
• FIG. 4 is a schematic perspective view showing a detection apparatus in accordance with a preferred embodiment of the present invention.
• FIG. 5 is a schematic perspective view showing a detection apparatus in accordance with a preferred embodiment of the present invention
• FIGS. 6A and 6B are schematic views showing a detection apparatus in accordance with a preferred embodiment of the present invention, and FIG. 6A is a plan view and FIG. 6B is a front view;
• FIG. 7 is a schematic perspective view showing a detection apparatus in accordance with a preferred embodiment of the present invention
• FIG. 8 is a schematic perspective view showing a detection apparatus in accordance with a preferred embodiment of the present invention.
• FIG. 9 is a schematic perspective view showing a detection apparatus in accordance with a preferred embodiment of the present invention.
• FIG. 10 is a schematic perspective view showing a detection apparatus in accordance with a preferred embodiment of the present invention.
• a transmission line for guiding a terahertz-wave have a flow path through which a flowable substance such as liquid or powder can be introduced.
• a flowable substance such as liquid or powder
• Any path capable of disposing an objective substance to be inspected or examined (hereinafter, simply referred to as "object substance") in the transmission line may be used. It is preferable that the flow path is not parallel to a propagation direction of an electromagnetic wave and is provided so as to pass through a region of the transmission line in which the electromagnetic wave is strongly distributed.
• the physical properties of the flowable substance can be examined or the substance can be identified, for example.
• the terahertz-wave can pass through a sample of such substance.
• a gap may be provided at a part of a cladding and a core which compose the waveguide to thereby form a flow path.
• a pipe-shaped hollow member made of a dielectric may be provided in a cavity of a waveguide tube composing the metallic waveguide tube to thereby form a flow path.
• a gap may be provided in a portion of the dielectric to thereby form a flow path.
• a transmission cable is used as the transmission line, a gap may be provided at a part of a dielectric portion between a ground cable and a signal cable which compose the transmission cable to thereby form a flow path.
• a pipe-shaped hollow member made of a dielectric can be provided in the cavity to thereby form a flow path.
• the pipe-shaped hollow member constituting the flow path is a dielectric with a low loss, a low dispersion and a low refractive index.
• a metallic waveguide tube is internally filled with a dielectric and a gap is provided in a portion of the dielectric to thereby form a flow path, " it is desirable that the dielectric has a ' low loss, a low dispersion and a low refractive index.
• a terahertz-wave may be coupled from the outside into a transmission line, while a terahertz- wave generator may be integrated in a portion of a transmission line.
• a terahertz-wave generator may be integrated at an end surface of the waveguide or the waveguide tube.
• a terahertz-wave generator may be integrated on the transmission cable.
• a terahertz-wave propagating through a transmission line may be radiated outside and detected by a terahertz-wave detector, while a terahertz-wave detector may be integrated in a portion of a transmission line.
• a terahertz-wave detector may be integrated in a portion of a transmission line.
• Examples of the terahertz-wave generator and terahertz-wave generating method include a method of applying a voltage to a photoconductive antenna formed on gallium arsenide formed by a low- temperature growth method and irradiating a femtosecond laser light thereto.
• Examples of n integration of a terahertz-wave generator include a method in which such a photoconductive antenna as mentioned above is provided on, for example, an end surface of a waveguide tube.
• examples of the terahertz-wave detector include one utilizing a method of irradiating a femtosecond laser light to a photoconductive antenna without applying a voltage thereto and measuring a current.
• the above-mentioned photoconductive antenna may be provided on an end surface of a waveguide tube from which a terahertz-wave is exited. Thereby, sensing can be performed with a terahertz-wave being not influenced by moisture in air.
• an EO crystal having an electrooptic effect such as ZnTe
• the crystal orientation of the EO crystal and the polarization direction of the terahertz-wave are suitably selected, thereby utilizing a phenomenon in which the reflectance and refractive index of the EO crystal are changed with polarization dependence.
• a nonlinear substance such as DAST crystal
• a waveguide tube or waveguide may be provided inside or at an end surface of a waveguide tube or waveguide.
• a sampling tool such as a needle for syringe
• the flow path as connecting means for connecting the obtained object to a path through another flow path (such as a tube)
• the sample can be set at a predetermined position simultaneously with sampling.
• a sampling tool such as a needle for syringe
• the flow path as connecting means for connecting the obtained object to a path through another flow path (such as a tube)
• the sample can be set at a predetermined position simultaneously with sampling.
• an area of the sample in the flow path which is in contact with outside air is small, such configuration is advantageous in the case where a sample susceptible to outside air is to be measured.
• sensing can be performed while increasing the concentration of the specific particles or molecules in a sensing portion.
• This method makes it possible to successively or simultaneously perform sample concentration and sensing, and is therefore advantageous for improving working efficiency.
• a substance which absorbs or is bonded to specific (one or more kinds of) particles or molecules contained in a flowable substance by disposing on a wall surface.of a flow path a substance which absorbs or is bonded to specific (one or more kinds of) particles or molecules contained in a flowable substance, and by capturing the specific particles or molecules on the wall surface of the flow path, it is possible to sense a flowable sample and particles or molecules contained therein based on a change in the complex dielectric constant or absorption spectrum of the substance disposed on the wall surface of the flow path resulting from the absorption or bonding of the particles or molecules.
• the electromagnetic wave it is preferable to use an electromagnetic wave including an arbitrary component in a frequency range of 30 GHz to 30 THz.
• a parallel plate waveguide 10 has a structure in which a polystyrene plate 12 is interposed between metallic plates 11a, lib.
• the polystyrene plate 12 has a gap 13 provided therein.
• the interval between the opposed surfaces of the metallic plates 11a, lib is about 100 ⁇ m.
• a typical size of each of the metallic plates 11a, lib is about 10 mm to 20 mm in each of x-direction and z-direction,
• the gap 13 is about 50 ⁇ m in x-direction.
• a flowable sample such as a fluid can be introduced into the gap 13.
• the interval between the metallic plates 11a, lib is set to 100 ⁇ m.
• the present invention is not limited thereto.
• polystyrene is used for the member interposed between the metallic plates 11a, lib
• the present invention is not limited thereto.
• any other dielectric may be used as long as it is sufficiently small in absorption (loss) and dispersion with respect to the terahertz-wave.
• it is desirable that the refraction index is close to 1.
• a semiconductor having a high conductivity may be used instead of the metallic plates 11a, lib.
• a terahertz-wave enters the parallel plate waveguide 10 in a direction indicated by the left-hand arrow in the figures and exits from the parallel plate waveguide 10 in a direction indicated by the right-hand arrow in the figures .
• the terahertz-wave propagating through the parallel plate waveguide 10 interacts with a flowable sample introduced into the gap 13.
• the flowable substance can be measured, sensed, or analyzed.
• a laser light having a pulse width of about 100 fs (femtoseconds) emitted from a femtosecond laser 20 is split by a beam splitter 21 into two optical paths, one of which 5 is irradiated onto a biased gap portion of a photoconductive antenna 22a made of low-temperature grown GaAs (LT-GaAs) or the like to generate terahertz-wave pulses 27 (a hemispherical lens made of high-resistance Si or the like being in close
• the terahertz-wave pulses 27 are reflected by a parabolic mirror 23a, pass through a semicylindrical lens 24a made of high-resistance Si (for example, 10 k ⁇ -cm) or the like and are coupled
• the terahertz-wave pulses interact with the sample (not shown) introduced into the gap 13 of the parallel plate waveguide 10 and are then exited from a second end of
• the parallel plate waveguide 10 and reach a photoconductive antenna 22b through a semicylindrical lens 24b and a parabolic mirror 23b.
• the other component of the laser light as split by the beam splitter 21 passes through a time delay
• device 26 is reflected by a mirror 25 and reaches the photoconductive antenna 22b simultaneously with the arrival of the terahertz-wave pulses. At this time, by shifting the timing of the laser light beam reaching the photoconductive antenna 22b through the time delay device 26 and the timing of the terahertz- wave pulses reaching the photoconductive antenna 22b through the parallel plate waveguide 10 from each other by use of the time delay device 26, the waveform of the terahertz-wave pulse can be obtained.
• a current flows through the photoconductive antenna 22b for a period which corresponds to the pulse time width of the femtosecond laser and a carrier life of a semiconductor film constituting the photoconductive antenna 22b.
• the magnitude of the current at this time reflects the magnitude of electric field amplitude of the terahertz-wave pulse 27 incident on the photoconductive antenna 22b. Therefore, measuring the current that flows through the photoconductive antenna makes it possible to obtain the waveform of the terahertz-wave pulse 27, which is then subjected to Fourier transform to give a spectrum of the terahertz-wave pulse 27.
• the parallel plate waveguide can transmit an electromagnetic wave in a TEM mode. Therefore, when no sample exists in the gap 13, the terahertz-wave pulses 27 propagate through the parallel plate waveguide 10 without changing the pulse waveform before and after the parallel plate waveguide 10. That is, when no sample exists in the gap 13, the waveform of the terahertz-wave pulse 27 before incidence on the parallel plate waveguide 10 and the waveform of the terahertz-wave pulse 27 after passing through the parallel plate waveguide 10 are substantially similar to each other.
• the gap 13 has such a sufficiently small thickness as about 50 ⁇ m in the x-direction, even when the gap 13 is filled with a sample which well absorbs the terahertz-wave, such as water, the terahertz-wave pulses propagating through the parallel plate waveguide 10 can ⁇ pass through the gap 13 without being completely absorbed.
• FIGS. 3A, 3B, and 3C are schematic graphical representations showing spectrums of the terahertz-wave which are obtained in the embodiment of the present invention.
• the waveform of the terahertz-wave passing through the parallel plate waveguide 10 is recorded and subjected to Fourier transform to obtain a power spectrum 30 (FIG. 3A) .
• the volume of the gap 13 is sufficiently small and only a slight amount of sample is required. Therefore, this method is advantageous in the case where an expensive sample (for example, a solution containing an antibody) is to be examined.
• the terahertz-wave pulse generation has been described by taking as an example a method using a photoconductive antenna.
• FIGS. 4 and 5 A second embodiment of the present invention will be described with reference to FIGS. 4 and 5.
• photoconductive antennas 33a, 33b are provided in both ends of the parallel plate waveguide 10.
• a hemispherical lens made of high-resistance Si or the like is not in close contact with the photoconductive antennas 33a, 33b. In this case, it is unnecessary to perform optical axis alignment of the terahertz-wave spatial propagation optical system, so that the size reduction of the system can be attained.
• the photoconductive antennas 33a, 33b each typically has a substrate with a size of about several millimeters to one centimeter in each of the y- and z-directions and are each provided with an antenna pattern (not shown) on its outer surface.
• Typical sizes of the metallic plates 11a, lib, the polystyrene plate 12, and the gap 13 are identical to those described in the first embodiment.
• the photoconductive antennas 22a, 22b can be provided in both ends of the parallel plate waveguide 10.
• a photoconductive antenna 33a and an EO crystal 34 which is a substance having an electrooptic effect (such as ZnTe) may be provided in the respective ends of the parallel plate waveguide 10.
• the terahertz-wave is detected using a known technique of utilizing a phenomenon in which when a terahertz-wave generated by irradiating a femtosecond laser to the photoconductive antenna 33a passes through the gap 13 and then reaches the EO crystal 34, the reflectance of the EO crystal 34 to the laser light varies depending on a wave amplitude of the reached terahertz-wave, thereby obtaining the amplitude of the terahertz-wave.
• a nonlinear optical crystal such as a DAST crystal or InP may be provided at an end of the parallel plate waveguide 10 instead of the photoconductive element 33a. In this case, irradiating such a nonlinear optical crystal directly with a femtosecond laser generates a terahertz-wave.
• the detection apparatus in accordance with this embodiment has a structure in which a hollow member 40 made of a substance with less absorption/loss and dispersion to the terahertz-wave, such as polystyrene is interposed between metallic plates 11a, lib composing the parallel plate waveguide 10.
• a hollow member 40 made of a substance with less absorption/loss and dispersion to the terahertz-wave, such as polystyrene is interposed between metallic plates 11a, lib composing the parallel plate waveguide 10.
• a fourth embodiment of the present invention will be described with reference to FIGS. 7 and 8.
• a waveguide tube whose section is square or circular is used instead of the parallel plate waveguide.
• a hollow member 40 for flowable sample introduction is provided in a waveguide tube 50 having a square section.
• a typical size of the section of the square waveguide tube is 100 ⁇ m to 200 ⁇ m in each of the y- and z-directions .
• a gap capable of introducing a flowable sample may be provided between a signal cable and a ground cable of a transmission cable.
• a flow path 63 is provided between a signal cable 61 and a ground cable 62 of a transmission cable 60 (microstrip line in the example shown -in the figure) .
• the sample introducing flow path and the terahertz-waveguide portion (transmission cable) can be integrally formed on the same substrate, so that further size reduction can be realized.
• FIG. 9 A fifth embodiment of the present invention will be described with reference to FIG. 9.
• a filter 14 is provided in a portion of the gap 13.
• a metallic plate lib as illustrated in FIGS. IA and IB is omitted for convenience of description.
• a terahertz-wave enters the parallel plate waveguide 10 in a direction indicated by the left- hand arrow and exits from the parallel plate waveguide 10 in a direction indicated by the right- hand arrow.
• an end of the gap 13 at which the filter 14 is provided is a first end of the gap 13 and an end opposed to the first end is a second end of the gap 13.
• a filter for example, a semipermeable membrane which allows passing of water but does not allow passing of the certain type of protein is provided.
• the concentration of the certain type of protein in the gap 13 increases, so that a transmission spectrum of the certain type of protein can be measured at a high sensitivity with a high precision.
• a sixth embodiment of the present invention will be described with reference to FIG. 10.
• a first substance 15 e.g., biotin
• FIGS. IA and IB a metallic plate lib as illustrated in FIGS. IA and IB is omitted for convenience of description.
• a terahertz-wave enters the parallel plate waveguide 10 in a direction indicated by the left- hand arrow and exits from the parallel plate waveguide 10 in a direction indicated by the right- hand arrow.
• a solution containing a second substance (e.g., avidin; not shown) which is specifically bonded to the first substance 15 is flown into the gap 13.
• the second substance in the solution is bonded to the first substance 15 applied to the- inner surface of the gap 13, so that a complex dielectric constant and an absorption spectrum of the first substance 15 in the frequency range of the terahertz- wave are changed, based on which the second substance can be sensed at a high sensitivity.

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• 2004
  • 2004-12-27 JP JP2004376370A patent/JP4154388B2/ja not_active Expired - Fee Related
• 2005
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