Abstract:
A detection device having: a terahertz wave generation element; a terahertz wave detection element; a first transmission path arranged upon the terahertz wave generation element; a second transmission path arranged upon the terahertz wave detection element; and a sealed section arranged between the terahertz wave generation element and the terahertz wave detection element and separated from the first transmission path and the second transmission path, so as to surround the first transmission path and the second transmission path. A space between an emission surface in the first transmission path and an incident surface in the second transmission path is connected to a space between the first transmission path and the sealed section and to a space between the second transmission path and the sealed section.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a detection device for acquiring information of an object by detecting the state of terahertz waves having passed through the object, and a method of manufacturing the detection device. 
       BACKGROUND ART 
       [0002]    Terahertz waves consist of electromagnetic waves having a frequency of about 0.01 to 100 THz between light waves and radio waves, and have an intermediate property between light waves and radio waves. In recent years, techniques of acquiring information of an object by detecting terahertz waves having passed through the object or by detecting the state of terahertz waves reflected by the object have been proposed (see, for example, PTLS 1 to 3). 
         [0003]    PTL 1 discloses a reflection type detection apparatus which acquires information of an object by detecting the state of terahertz waves reflected by the object. The detection apparatus disclosed in PTL 1 includes a terahertz wave generation section, a prism and a terahertz wave detection section. The terahertz wave generation section applies femtosecond pulse laser light to InAs to generate terahertz waves. The terahertz waves are incident on the prism through a light path including two off-axis parabolic mirrors. The object is placed on a planar surface of the prism. When totally reflected by the planar surface under the object, the terahertz waves incident on the prism become terahertz waves containing the information of the object. The terahertz waves containing the information of the object are emitted from the prism, and reach the terahertz wave detection section through the light path including the two off-axis parabolic mirrors. The terahertz wave detection section detects the terahertz waves containing the information of the object. 
         [0004]    In the detection apparatus disclosed in PTL 1, a large number of optical elements are provided between the terahertz wave generation section and the prism, and between the prism and the terahertz wave detection section. As such, the detection apparatus disclosed in PTL 1 has a problem that the device size is large. In addition, since terahertz waves are absorbed by the moisture in the air, the space between the terahertz wave generation section and the prism and the space between the prism and the terahertz wave detection section are required to be filled with nitrogen, or vacuumized. To solve such problems, PTL 2 proposes a technique in which the terahertz wave generation element and the terahertz wave detection element are integrated with the prism. 
         [0005]    PTL 2 discloses a reflection type detection apparatus which acquires the information of an object by detecting the state of the terahertz waves reflected by the object and a reflection type detection device used for the reflection type detection apparatus. The detection apparatus disclosed in PTL 2 includes a light source, a detection device, and a light detector. The detection device includes a prism, a terahertz wave generation element disposed on the incidence surface of the prism, and a terahertz wave detection element disposed on the emission surface of the prism. The light source applies femtosecond pulse laser light to the terahertz wave generation element of the detection device. As a result, terahertz waves are generated at the terahertz wave generation element, and the terahertz waves travel in the prism. The object is placed on the planar surface of the prism. When totally reflected by the planar surface under the object, the terahertz waves incident on the prism become terahertz waves containing the information of the object, and reach the terahertz wave detection element. The terahertz wave detection element generates light containing information of the object in accordance with the input terahertz waves. The light detector detects the light containing the information of the object. 
         [0006]    In addition, PTL 3 discloses a transmission type detection device which acquires information of an object by detecting the state of the terahertz waves having passed through the object.  FIG. 1  is a perspective view of the detection device disclosed in PTL 3. As illustrated in  FIG. 1 , detection device  10  disclosed in PTL 3 includes two metal plates  12   a  and  12   b , two polystyrene plates  14   a  and  14   b  and two photoconductive antennas  16   a  and  16   b . Two metal plates  12   a  and  12   b  are disposed to face each other with a distance of approximately 100 μm therebetween, and two polystyrene plates  14   a  and  14   b  are disposed between metal plates  12   a  and  12   b . The laminated body composed of two metal plates  12   a  and  12   b  and two polystyrene plates  14   a  and  14   b  serves as a parallel flat plate waveguide path. Space  18  for housing an object is formed between two polystyrene plates  14   a  and  14   b . The distance between two polystyrene plates  14   a  and  14   b  is approximately 50 μm. The object housed in space  18  is thus present at a middle point of the waveguide path. Photoconductive antenna  16   a  is disposed at one end portion of the laminated body, and photoconductive antenna  16   b  is disposed at the other end portion of the laminated body. When femtosecond pulse laser light is applied to photoconductive antenna  16   a , terahertz waves are generated. The terahertz waves travel through polystyrene plate  14   a , space  18  (object) and polystyrene plate  14   b , and reach photoconductive antenna  16   b . Photoconductive antenna  16   b  detects the terahertz waves transmitted through the object (converts the terahertz waves into an electric signal). 
         [0007]    Since attenuation of terahertz waves is large, and terahertz waves are difficult to be directly applied to polystyrene plate  14   a , detection device  10  disclosed in PTL 3 applies laser light to photoconductive antenna  16   a  to generate terahertz waves. In addition, since terahertz waves are attenuated when the size of space  18  is increased, the size of space  18  is preferably small as much as possible. 
         [0008]    Even with a small size, detection device  10  disclosed in PTL 3 can detect the state of the terahertz waves having passed through the object. 
       CITATION LIST 
     Patent Literature 
     PTL 1 
     Japanese Patent Application Laid-Open No. 2004-354246 
     PTL 2 
     Japanese Patent Application Laid-Open No. 2008-224449 
     PTL 3 
     Japanese Patent Application Laid-Open No. 2006-184078 
     SUMMARY OF INVENTION 
     Technical Problem 
       [0009]    When the terahertz waves having passed through the object in space  18  have to be efficiently detected with transmission type detection device  10  disclosed in PTL 3, the distance between two polystyrene plates  14   a  and  14   b  has to be extremely reduced, and consequently the size of space  18  for housing an object is extremely reduced. When space  18  has such a small size, it is difficult to install an object in space  18 , and it is difficult to cause a reaction between the object and another material in space  18 . 
         [0010]    An object of the present invention is to provide a transmission type detection device which acquires information of an object by detecting the state of the terahertz waves having passed through the object, and can achieve downsizing and detection with high sensitivity while sufficiently ensuring a space for housing an object, and a manufacturing method of the transmission type detection device. 
       Solution to Problem 
       [0011]    To solve the above-mentioned problems, a detection device according to embodiments of the present invention is a detection device for acquiring information of an object by detecting a state of terahertz waves having passed through the object, the detection device including: a terahertz wave generation element; a terahertz wave detection element disposed to face the terahertz wave generation element; a first transmission path disposed on the terahertz wave generation element to protrude from the terahertz wave generation element toward the terahertz wave detection element; a second transmission path disposed on the terahertz wave detection element to protrude from the terahertz wave detection element toward the terahertz wave generation element; and a sealing part disposed between the terahertz wave generation element and the terahertz wave detection element to surround the first transmission path and the second transmission path, the sealing part being separated from the first transmission path and the second transmission path. The first transmission path includes an emission surface which emits terahertz waves generated at the terahertz wave generation element, the emission surface being disposed at an end of the first transmission path; the second transmission path includes an incidence surface on which the terahertz waves emitted from the emission surface are incident, the incidence surface being disposed at an end of the second transmission path to face the emission surface, the incidence surface being separated from the emission surface; and a space between the emission surface and the incidence surface is communicated with a space between the first transmission path and the sealing part and a space between the second transmission path and the sealing part. 
         [0012]    To solve the above-mentioned problems a method of manufacturing the detection device according to embodiments of the present invention includes: forming a plurality of pairs of first electrode films on a first surface of a first photoconductive substrate; forming a plurality of pairs of second electrode films on a first surface of a second photoconductive substrate; forming a plurality of first transmission paths on a second surface of the first photoconductive substrate; forming a plurality of second transmission paths on a second surface of the second photoconductive substrate; producing a laminated body by disposing a sealing sheet including a plurality of through holes for housing the first transmission path and the second transmission path at a position between the second surface of the first photoconductive substrate and the second surface of the second photoconductive substrate, and by fixing the first photoconductive substrate, the sealing sheet and the second photoconductive substrate; and obtaining a plurality of detection devices by cutting the laminated body at a position between the through holes. 
       Advantageous Effects of Invention 
       [0013]    In the present invention, the sealing part is provided between the terahertz wave generation element and the terahertz wave detection element to surround the first transmission path and the second transmission path such that a space for housing an object is sufficiently ensured in the sealing part. Consequently, even when the distance between the first transmission path and the second transmission path is reduced, the object can be easily move to the position between the first transmission path and the second transmission path, and thus it is possible to provide a detection device which can achieve downsizing and detection with high sensitivity. With the detection device according to the embodiments of the present invention, the state of the terahertz waves having passed through the object can be detected with high sensitivity. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a perspective view of a transmission type detection device disclosed in PTL 3; 
           [0015]      FIG. 2A  is a perspective view of a detection device according to Embodiment 1, and  FIG. 2B  is a perspective view of the detection device according to Embodiment 1 in which a sealing part is omitted; 
           [0016]      FIG. 3  is a sectional view of the detection device according to Embodiment 1; 
           [0017]      FIG. 4  is a sectional view of a modification of the detection device according to Embodiment 1; 
           [0018]      FIG. 5  is a sectional view of the detection device according to Embodiment 1 in which the distance between an emission surface and an incidence surface can be changed; 
           [0019]      FIG. 6  is a schematic view illustrating a configuration of the detection apparatus according to Embodiment 1; 
           [0020]      FIGS. 7A to 7F  are sectional views illustrating a manufacturing method of the detection device according to Embodiment 1; 
           [0021]      FIG. 8A  is a perspective view of the detection device according to Embodiment 2, and  FIG. 8B  is a perspective view of the detection device according to Embodiment 2 in which a sealing part is omitted; 
           [0022]      FIG. 9  is a perspective view of a modification of the detection device according to Embodiment 2 in which a sealing part is omitted; 
           [0023]      FIG. 10A  is a perspective view of a detection device according to Embodiment 3, and  FIG. 10B  is a perspective view of the detection device according to Embodiment 3 in which a sealing part is omitted; and 
           [0024]      FIG. 11  is a perspective view of a modification of the detection device according to Embodiment 3 in which the sealing part is omitted. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0025]    Embodiments of the present invention are described below in detail with reference to the accompanying drawings. 
       Embodiment 1 
     Configuration of Detection Device 
       [0026]      FIG. 2  and  FIG. 3  illustrate detection device  100  according to Embodiment 1 of the present invention.  FIG. 2A  is a perspective view of detection device  100 , and  FIG. 2B  is a perspective view of detection device  100  in which sealing part  150  is omitted.  FIG. 3  is a sectional view of detection device  100 . 
         [0027]    Detection device  100  is a device (chip) for acquiring information of an object by detecting the state of terahertz waves having passed through the object. Here, the “terahertz wave” is electromagnetic waves whose frequency is within a range of 0.01 to 100 THz. While the kind of the object is not limited, detection device  100  according to the present embodiment is particularly effective for objects having fluidity such as liquid and powder. 
         [0028]    As illustrated in  FIG. 2  and  FIG. 3 , detection device  100  includes terahertz wave generation element  110 , terahertz wave detection element  120 , first waveguide path  130 , second waveguide path  140  and sealing part  150 . 
         [0029]    Terahertz wave generation element  110  generates terahertz waves for transmission through an object. In the present embodiment, terahertz wave generation element  110  is a photoconductive antenna including photoconductive substrate  112 , and a pair of electrode films  114   a  and  114   b  disposed on photoconductive substrate  112  (for example, low-temperature growth GaAs). However, the type of terahertz wave generation element  110  is not limited as long as desired terahertz waves can be generated. Examples of terahertz wave generation element  110  include a nonlinear optical crystal (for example, ZnTe). 
         [0030]    Terahertz wave detection element  120  is disposed to face terahertz wave generation element  110 . Terahertz wave detection element  120  detects terahertz waves having passed through the object after being emitted from terahertz wave generation element  110 . In the present embodiment, terahertz wave detection element  120  is a photoconductive antenna including photoconductive substrate  122 , and a pair of electrode films  124   a  and  124   b  disposed on photoconductive substrate  122  (for example, low-temperature growth GaAs). As with terahertz wave generation element  110 , the type of terahertz wave detection element  120  is not limited as long as terahertz waves emitted from terahertz wave generation element  110  can be detected. Examples of terahertz wave detection element  120  include a nonlinear optical crystal (for example, ZnTe). 
         [0031]    First waveguide path  130  is a transmission path disposed on terahertz wave generation element  110  (photoconductive substrate  112 ). To be more specific, first waveguide path  130  is disposed at a position (in the present embodiment, the rear side of the gap of the pair of electrode films  114   a  and  114   b ) corresponding to a portion where terahertz waves are generated in terahertz wave generation element  110 . First waveguide path  130  protrudes from terahertz wave generation element  110  (photoconductive substrate  112 ) toward terahertz wave detection element  120 , and includes, at an end thereof, emission surface  132  that emits terahertz waves. First waveguide path  130  transmits the terahertz waves generated at terahertz wave generation element  110  to emission surface  132 , and emits the terahertz waves from emission surface  132 . 
         [0032]    Second waveguide path  140  is a transmission path disposed on terahertz wave detection element  120  (photoconductive substrate  122 ). To be more specific, second waveguide path  140  is disposed at a position (in the present embodiment, the rear side of the gap of the pair of electrode films  124   a  and  124   b ) corresponding to a portion where terahertz waves are detected at terahertz wave detection element  120 . Second waveguide path  140  protrudes from terahertz wave detection element  120  (photoconductive substrate  122 ) toward terahertz wave generation element  110 , and includes, at an end thereof, incidence surface  142  on which terahertz waves emitted from emission surface  132  of first waveguide path  130  are incident. Emission surface  132  and incidence surface  142  are separated from each other to face each other. Detection device  100  of the present embodiment irradiates an object which is present between emission surface  132  and incidence surface  142  with terahertz waves to detect the terahertz waves having passed through the object. The terahertz waves having passed through the object are incident on second waveguide path  140 , and second waveguide path  140  transmits the terahertz waves to terahertz wave detection element  120 . 
         [0033]    The type of the material of first waveguide path  130  and second waveguide path  140  is not limited as long as absorption (loss) and dispersion of terahertz waves are small. Examples of the material of first waveguide path  130  and second waveguide path  140  include resins (for example, polytetrafluoroethylene), ceramics, and silicon. The material of first waveguide path  130  and the material of second waveguide path  140  may be different from each other. Preferably, first waveguide path  130  and second waveguide path  140  are made of a resin material from the standpoint of the ease of working. 
         [0034]    The shape of first waveguide path  130  and second waveguide path  140  is not limited as long as terahertz waves can be efficiently transmitted. In the present embodiment, each of first waveguide path  130  and second waveguide path  140  has a cuboid shape. 
         [0035]    While the length of first waveguide path  130  (the height from terahertz wave generation element  110 ) and the length of second waveguide path  140  (the height of terahertz wave detection element  120 ) are not limited, the lengths are preferably each 10 μm or greater. When each of first waveguide path  130  and second waveguide path  140  has a length of 10 μm or greater, the influence of multiple reflection can be reduced by delaying the travelling of the stray light. From the standpoint of the handleability of detection device  100 , the upper limit of the length of first waveguide path  130  and second waveguide path  140  is about several millimeters. 
         [0036]    The widths of first waveguide path  130  and second waveguide path  140  (the lengths in the direction parallel to emission surface  132  and incidence surface  142 ) are not limited, and may be appropriately selected in accordance with the wavelength of terahertz waves. By setting the widths of first waveguide path  130  and second waveguide path  140  in accordance with the wavelength of terahertz waves, the S/N ratio can be improved by intensifying terahertz waves of a desired wavelength. 
         [0037]    The distance between emission surface  132  and incidence surface  142  is not limited. In terms of the balance between the movability of the object and the loss of terahertz waves, the distance between emission surface  132  and incidence surface  142  preferably falls within a range of 10 to 100 μm. 
         [0038]    The side surface of first waveguide path  130  (the surface other than emission surface  132 ) and the side surface of second waveguide path  140  (the surface other than incidence surface  142 ) are preferably covered with metal films  134  and  144  for reflecting terahertz waves. In the present embodiment, the rear surface of terahertz wave generation element  110  (photoconductive substrate  112 ) and the side surface of first waveguide path  130  are covered with metal film  134  for reflecting terahertz waves. In addition, the rear surface of terahertz wave detection element  120  (photoconductive substrate  122 ) and the side surface of second waveguide path  140  are covered with metal film  144  for reflecting terahertz waves. No metal film  134  is present at the interface between terahertz wave generation element  110  (photoconductive substrate  112 ) and first waveguide path  130 , and no metal film  144  is present at the interface between terahertz wave detection element  120  (photoconductive substrate  122 ) and second waveguide path  140 . The type of the metal of metal films  134  and  144  is not limited as long as terahertz waves can be reflected. Examples of the metal of metal films  134  and  144  include gold, silver, aluminum, and alloys thereof. 
         [0039]    It is to be noted that, from the viewpoint of the ease of manufacturing, first waveguide path  130  may be formed integrally with base  136  disposed on the rear surface of terahertz wave generation element  110  (photoconductive substrate  112 ) as illustrated in  FIG. 4 . Likewise, second waveguide path  140  may be formed integrally with base  146  disposed the rear surface of terahertz wave detection element  120  (photoconductive substrate  122 ). 
         [0040]    Sealing part  150  is disposed between terahertz wave generation element  110  (photoconductive substrate  112 ) and terahertz wave detection element  120  (photoconductive substrate  122 ) to surround first waveguide path  130  and second waveguide path  140 . In addition, sealing part  150  is separated from first waveguide path  130  and second waveguide path  140 , and thus a space for housing an object, which is surrounded by terahertz wave generation element  110  (photoconductive substrate  112 ), terahertz wave detection element  120  (photoconductive substrate  122 ) and sealing part  150 , is formed around first waveguide path  130  and second waveguide path  140 . For the purpose of housing an object in this space, terahertz wave generation element  110  (photoconductive substrate  112 ) is provided with two through holes  116   a  and  116   b.    
         [0041]    As described above, an object to be irradiated with terahertz wave is required to be present in the space between emission surface  132  and incidence surface  142 , and the space between emission surface  132  and incidence surface  142  is communicated with the space around first waveguide path  130  and second waveguide path  140  (the space between first waveguide path  130  and sealing part  150 , and the space between second waveguide path  140  and sealing part  150 ). Thus, the object can freely move in the spaces. 
         [0042]    The material of sealing part  150  is not limited as long as sealing part  150  is not influenced by the object. Examples of the material of sealing part  150  include resins, rubber, and metals. From the viewpoint of adjustability of the distance between emission surface  132  and incidence surface  142 , sealing part  150  is preferably composed of an elastic body. When sealing part  150  is provided with elasticity, the distance between emission surface  132  and incidence surface  142  can be adjusted as illustrated in  FIG. 5 , and the distance between first waveguide path  130  and second waveguide path  140  can be changed. In addition, reaction can be facilitated by agitating the fluid housed in detection device  100 . By conducting measurement multiple times with variations of the distance between emission surface  132  and incidence surface  142 , the difference of the object in absorption of terahertz waves can be determined. Even in the case where the material of sealing part  150  is a resin or a metal, the effect identical to that of sealing part  150  composed of an elastic body can be expected by forming sealing part  150  with a plurality of mutually slidable members, or by providing sealing part  150  with an accordion structure. 
         [0043]    (Usage of Detection Device) 
         [0044]    Next, a usage of detection device  100  is described. 
         [0045]      FIG. 6  illustrates a configuration of detection apparatus  200  for acquiring information of an object with use of detection device  100  according to the present embodiment. As illustrated in  FIG. 6 , detection apparatus  200  includes laser light source  210 , beam splitter  220 , mirrors  230 ,  240  and  260 , time delayer  250 , power source  270 , ammeter  280  and detection device  100 . Object (sample) S is housed in the internal space of detection device  100 . 
         [0046]    Laser light source  210  emits short-pulse laser light (for example, femtosecond pulse laser light). The light flux of pulse laser light is divided by beam splitter  220  into two light fluxes (pump light and probe light). The pump light is reflected by mirror  230 , and reaches terahertz wave generation element  110  of detection device  100 . Each of electrode films  114   a  and  114   b  of terahertz wave generation element  110  is connected with power source  270 , and a predetermined voltage is applied across electrode films  114   a  and  114   b . When pump light is applied to the gap between electrode films  114   a  and  114   b  in the above-mentioned state, pulsed terahertz waves are generated. The terahertz waves travel in first waveguide path  130  and are emitted from emission surface  132 . Then, terahertz waves pass through an object (sample) S between emission surface  132  and incidence surface  142 , and become terahertz waves containing information of object S. 
         [0047]    The terahertz waves having passed through object S enter second waveguide path  140  from incidence surface  142 , travel in second waveguide path  140 , and reach terahertz wave detection element  120 . On the other hand, the probe light passes through time delayer  250  after being reflected by mirror  240 , and reaches terahertz wave detection element  120  of detection device  100  after being reflected by mirror  260 . Each of electrode films  124   a  and  124   b  of terahertz wave detection element  120  is connected with ammeter  280 . When terahertz waves reach terahertz wave detection element  120  at the time of application of the probe light to the gap between electrode films  124   a  and  124   b , a current flows between electrode films  124   a  and  124   b  for a period corresponding to the pulse time width of the probe light and the carrier lifetime in photoconductive substrate  122 . The value of the current corresponds to the value of the amplitude of the electric field of the terahertz waves having reached terahertz wave detection element  120 . In addition, with use of time delayer  250 , the timing of arrival of terahertz waves at the terahertz waves detection device  120  and the timing of arrival of the probe light at terahertz wave detection element  120  can be shifted from each other. Accordingly, the waveform of pulsed terahertz waves can be acquired by measuring the current with use of ammeter  280 . The spectrum of the terahertz waves having passed through object S can be obtained by Fourier transform of the waveform of the terahertz waves. For example, the absorption spectrum of object S to the terahertz waves can be obtained by acquiring the spectrum of the terahertz waves of the state where object S is housed in the internal space of detection device  100  and the state where object S is not housed in the internal space of detection device  100 , and calculating the ratio of the acquired the spectrums. 
         [0048]    (Manufacturing Method of Detection Device) 
         [0049]    The manufacturing method of detection device  100  according to the present embodiment is not limited. For example, detection device  100  is manufactured through the procedure illustrated in  FIG. 7 . 
         [0050]    First, as illustrated in  FIG. 7A , photoconductive substrate  112 ′ in the form of a wafer is prepared. Next, as illustrated in  FIG. 7B , a plurality of pairs of electrode films  114   a  and  114   b  are formed on one surface of photoconductive substrate  112 ′. The formation method of electrode films  114   a  and  114   b  is not limited. For example, electrode films  114   a  and  114   b  are formed by photolithography. Next, as illustrated in  FIG. 7C , a plurality of first waveguide paths  130  are formed on the other surface of photoconductive substrate  112 ′. The formation method of first waveguide path  130  is not limited. For example, first waveguide path  130  is made of a resin material, and is formed by imprint molding. Thereafter, metal film  134  is formed on the side surface of first waveguide path  130  as necessary. 
         [0051]    Through the above-mentioned steps, a plurality of the combinations of terahertz wave generation element  110  and first waveguide path  130  are formed on one photoconductive substrate  112 ′. In addition, through similar procedure, a plurality of the combinations of terahertz wave detection element  120  and second waveguide path  140  are formed on one photoconductive substrate  122 ′. Thereafter, through holes  116   a  and  116   b  are also formed in a region around terahertz wave generation element  110  in photoconductive substrate  112 ′ on which a plurality of the combinations of terahertz wave generation element  110  and first waveguide path  130  are formed. 
         [0052]    Next, as illustrated in  FIG. 7D , sealing sheet  150 ′ provided with a plurality of through holes is disposed and fixed (bonded) on photoconductive substrate  122 ′ on which terahertz wave detection elements  120  and second waveguide path  140  are formed (or photoconductive substrate  112 ′ on which terahertz wave generation elements  110  and first waveguide paths  130  are formed). Next, as illustrated in  FIG. 7E , photoconductive substrate  112 ′ on which terahertz wave generation elements  110  and first waveguide paths  130  are formed (or photoconductive substrate  122 ′ on which terahertz wave detection elements  120  and second waveguide paths  140  are formed) is disposed and fixed (bonded) on sealing sheet  150 ′. In this manner, a laminated body including terahertz wave generation elements  110 , terahertz wave detection elements  120 , first waveguide paths  130  and second waveguide paths  140  is obtained. In this laminated body, first waveguide path  130  and second waveguide path  140  are housed in the through hole of sealing sheet  150 ′. 
         [0053]    Finally, as illustrated in  FIG. 7F , the laminated body is cut at a position between each through hole of sealing sheet  150 ′, and thus a plurality of detection devices can be obtained. 
         [0054]    (Effect) 
         [0055]    As described above, in detection device  100  according to the present embodiment, a large space communicated with the space between emission surface  132  and incidence surface  142  is provided around first waveguide path  130  and second waveguide path  140 . With this configuration, an object can be easily installed in the space between emission surface  132  and incidence surface  142  without increasing the size of detection device  100 . In addition, a reaction of an object with another material can be easily caused in detection device  100 . 
         [0056]    While each of terahertz wave generation element  110  and terahertz wave detection element  120  is composed of a photoconductive antenna in the present embodiment, the type of terahertz wave generation element  110  and terahertz wave detection element  120  is not limited to a photoconductive antenna as described above. The means for generating terahertz waves and the means for detecting the terahertz waves may be appropriately changed when terahertz wave generation element  110  and terahertz wave detection element  120  are composed of other elements. 
         [0057]    While two through holes  116   a  and  116   b  are formed in terahertz wave generation element  110  (photoconductive substrate  112 ) in the present embodiment, the number and position of through holes for housing an object is not limited. For example, one or a plurality of the through holes for housing an object may be provided. In addition, the position of the through hole for housing an object is not limited as long as the through hole is communicated with the space surrounded by terahertz wave generation element  110  (photoconductive substrate  112 ), terahertz wave detection element  120  (photoconductive substrate  122 ) and sealing part  150 . To be more specific, the through hole may be formed in terahertz wave detection element  120  (photoconductive substrate  122 ) or sealing part  150 . 
       Embodiment 2 
       [0058]    A detection device according to Embodiment 2 is different from the detection device according to Embodiment 1 in that, for example, each of the terahertz wave generation element and the terahertz wave detection element has a plurality of pairs of electrode films. In view of this, the same components as those of detection device  100  according to Embodiment 1 are denoted by the same reference numerals, and the descriptions thereof are omitted. 
         [0059]      FIG. 8A  is a perspective view of detection device  300  according to Embodiment 2 of the present invention, and  FIG. 8B  is a perspective view of detection device  300  in which sealing part  150  is omitted. 
         [0060]    As illustrated in  FIG. 8 , detection device  300  includes terahertz wave generation element  310 , terahertz wave detection element  320 , three first waveguide paths  330 , three second waveguide paths  340  and sealing part  150 . 
         [0061]    Terahertz wave generation element  310  is a photoconductive antenna including photoconductive substrate  112 , and three pairs of electrode films  114   a  and  114   b  disposed on photoconductive substrate  112 . Likewise, terahertz wave detection element  320  is a photoconductive antenna including photoconductive substrate  122 , and three pairs of electrode films  124   a  and  124   b  disposed on photoconductive substrate  122 . 
         [0062]    Three first waveguide paths  330  are respectively disposed on the rear side of the gaps of the three pairs of electrode films  114   a  and  114   b  of terahertz wave generation element  310 . Likewise, three second waveguide paths  340  are respectively disposed on the rear side of the gaps of the three pairs of electrode films  124   a  and  124   b  of terahertz wave detection element  320 . Emission surface  132  of each first waveguide path  330  faces incidence surface  142  of corresponding second waveguide path  340  with a space therebetween. That is, in detection device  300  of the present embodiment, three sets of a combination of a pair of electrode films  114   a  and  114   b , one first waveguide path  330 , one second waveguide path  340  and a pair of electrode films  124   a  and  124   b  are formed. 
         [0063]    The length of first waveguide path  330  (the height from terahertz wave generation element  310 ) and the length of second waveguide path  340  (the height from terahertz wave detection element  320 ) are different among the combinations of first waveguide path  330  and second waveguide path  340 . Accordingly, the distance between emission surface  132  and incidence surface  142  is different among the combinations of first waveguide path  330  and second waveguide path  340 . In the example illustrated in  FIG. 8B , the lengths of first waveguide path  330  and second waveguide path  340  illustrated on the left side are small (the distance between emission surface  132  and incidence surface  142  is large), and the lengths of first waveguide path  330  and second waveguide path  340  illustrated on the right side are large (the distance between emission surface  132  and incidence surface  142  is small). It is to be noted that first waveguide paths  330  and second waveguide paths  340  have the same width. 
         [0064]    In addition to the effect of detection device  100  of Embodiment 1, detection device  300  according to Embodiment 2 can perform measurement while changing the distance between emission surface  132  and incidence surface  142  for the same object by only changing the position for irradiation of the pump light and the probe light. 
         [0065]    While three first waveguide paths  330  are separately formed, and three second waveguide paths  340  are separately formed in the present embodiment, three first waveguide paths  330  may be integrally formed, and, three second waveguide paths  340  may be integrally formed as illustrated in  FIG. 9 . 
       Embodiment 3 
       [0066]    A detection device according to Embodiment 3 is different from the detection device according to Embodiment 2 in that, for example, the widths of a plurality of first waveguide paths and the widths of a plurality of second waveguide paths are different from each other. In view of this, the same components as those of detection device  100  according to Embodiment 1 or detection device  300  according to Embodiment 2 are denoted by the same reference numerals, and the descriptions thereof are omitted. 
         [0067]      FIG. 10A  is a perspective view of detection device  400  according to Embodiment 3 of the present invention, and  FIG. 10B  is a perspective view of detection device  400  in which sealing part  150  is omitted. 
         [0068]    As illustrated in  FIG. 10 , detection device  400  includes terahertz wave generation element  310 , terahertz wave detection element  320 , three first waveguide paths  430 , three second waveguide paths  440  and sealing part  150 . 
         [0069]    Three first waveguide paths  430  are integrally formed and three second waveguide paths  440  are integrally formed. The width of first waveguide path  430  and the width second waveguide path  440  are different from each other among the combinations of first waveguide path  430  and second waveguide path  440 . In the example illustrated in  FIG. 10B , the widths of first waveguide path  430  and second waveguide path  440  illustrated on the left side are small, and the widths of first waveguide path  430  and second waveguide path  440  illustrated on the right side are large. It is to be noted that first waveguide path  430  and second waveguide path  440  have the same distance therebetween. 
         [0070]    In addition to the effect of detection device  100  of Embodiment 1, detection device  400  according to Embodiment 3 can perform measurement while changing the wavelength of the applied terahertz waves for the same object by only changing the position for irradiation of the pump light and the probe light. 
         [0071]    While the widths of integrally formed three first waveguide paths  430  and integrally formed three second waveguide paths  440  are discontinuously changed in the present embodiment, the widths of integrally formed three first waveguide paths  430  and integrally formed three second waveguide paths  440  may be continuously (successively) changed as illustrated in  FIG. 11 . 
         [0072]    While three pairs of electrode films  114   a  and  114   b  are disposed for three first waveguide paths  330  and  430  and three pairs of electrode films  124   a  and  124   b  are disposed for three second waveguide paths  340  and  440  in Embodiment 2 and Embodiment 3, a pair of slidable electrode films may be disposed for a plurality of first waveguide paths  330  and  430  or second waveguide paths  340  and  440  instead of disposing a corresponding number of pairs of electrode films. 
         [0073]    While each of the transmission path (first transmission path) disposed on the rear side of terahertz wave generation element  110  and the transmission path (second transmission path) disposed on the rear side of terahertz wave detection element  120  is composed of a waveguide path in the Embodiments, the type of the first transmission path and the second transmission path is not limited to this. For example, each of the first transmission path and the second transmission path may also be a waveguide pipe or a transmission line. 
         [0074]    This application is entitled to and claims the benefit of Japanese Patent Application No. 2014-100320 filed on May 14, 2014, the disclosure each of which including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0075]    The detection device according to the embodiments of the present invention is suitable for food inspection and the like, for example. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10  Detection device 
           12   a ,  12   b  Metal plate 
           14   a ,  14   b  Polystyrene plate 
           16   a ,  16   b  Photoconductive antenna 
           18  Space 
           100 ,  300 ,  400  Detection device 
           110 ,  310  Terahertz wave generation element 
           112 ,  112 ′ Photoconductive substrate 
           114   a ,  114   b  Electrode film 
           116   a ,  116   b  Through hole 
           120 ,  320  Terahertz wave detection element 
           122 ,  122 ′ Photoconductive substrate 
           124   a ,  124   b  Electrode film 
           130 ,  330 ,  430  First waveguide path 
           132  Emission surface 
           134 ,  144  Metal film 
           136 ,  146  Base 
           140 ,  340 ,  440  Second waveguide path 
           142  Incidence surface 
           150  Sealing part 
           150 ′ Sealing sheet 
           200  Detection device 
           210  Laser light source 
           220  Beam splitter 
           230 ,  240 ,  260  Mirror 
           250  Time delayer 
           270  Power source 
           280  Ammeter 
         S Object (Sample)