JP2018036098A - Electromagnetic wave detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an influence of a temperature change by an electromagnetic wave detection device.SOLUTION: An electromagnetic wave detection device includes a first detector for outputting a first current on the basis of input of a reference voltage and a polarized electromagnetic wave, a second detector having an electrical characteristic equivalent to the first detector, for outputting a second current on the basis of at least input of the reference voltage, and an output part for outputting intensity of the electromagnetic wave on the basis of the first and second currents. The second detector is arranged so that a second component output on the basis of input of the electromagnetic wave in the second current becomes smaller than a first component output on the basis of input of the electromagnetic wave in the first current.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a technical field of an electromagnetic wave detection device that detects electromagnetic waves.

  As an example of a detection element used in this type of apparatus, Patent Document 1 discloses a detection element including a Schottky barrier diode. Patent Document 1 discloses that, as an operation example of the detection element, a direct current output can be obtained when infrared light (wavelength 10.6 μm) is irradiated with a bias voltage applied to the detection element. ing.

JP-A-9-162424

  According to the study by the inventors of the present application, when such electromagnetic wave detection is performed, even if the intensity of the input electromagnetic wave is unchanged, the current flowing through the detection element changes due to a change in the operating temperature, and this change is detected. It becomes an error. Further, when the bias voltage is fixed as a bias current (hereinafter simply referred to as “optimal bias current”) that gives an optimal or preferable dynamic range at a certain operating temperature, the fixed bias voltage is changed due to a change in the operating temperature. Then, a bias current deviating from the optimum bias current can be supplied.

  However, Patent Document 1 does not disclose how to set the bias voltage. If the bias voltage is always fixed, a correct detection result may not be obtained depending on the operating temperature.

  This invention is made | formed in view of the said problem, for example, and makes it a subject to provide the electromagnetic wave detection apparatus which can suppress the influence of a temperature change.

  In order to solve the above problems, an electromagnetic wave detection device of the present invention has a first detection unit that outputs a first current based on a reference voltage and an input of a polarized electromagnetic wave, and an electrical characteristic of the first detection unit. A second detection unit that is equivalent and outputs a second current based on at least the input of the reference voltage; and an output unit that outputs the intensity of the electromagnetic wave based on the first and second currents. The portion is arranged such that the second component of the second current output based on the input of the electromagnetic wave is smaller than the first component of the first current output based on the input of the electromagnetic wave. Is done.

  The effect | action and other gain of this invention are clarified from the form for implementing invention demonstrated below.

It is a characteristic view which shows an example of a voltage-current characteristic for every intensity | strength of the terahertz wave which injects into a Schottky barrier diode. It is a characteristic view which shows an example of the temperature change of the voltage-current characteristic of a Schottky barrier diode. It is a conceptual characteristic figure which shows the intensity | strength detection method of the terahertz wave using a Schottky barrier diode. It is a schematic side view of a detection optical system including the terahertz wave intensity detection device according to the first example. It is a circuit diagram which shows an example of the principal part of the detection circuit of the terahertz wave intensity detection apparatus which concerns on 1st Example. It is a circuit diagram which shows an example of the difference voltage detection part which concerns on 1st Example. It is sectional drawing of the Schottky barrier diode used in 1st Example. FIG. 8 is a schematic plan view (FIG. 8A) and two circuit diagrams (FIG. 8B) showing two Schottky barrier diodes in the first embodiment. FIG. 3 is a schematic plan view showing two antenna elements in the first embodiment. FIG. 10 is a schematic plan view showing the two Schottky barrier diodes of FIG. 8 and the two antenna elements of FIG. 9 in an overlapping manner in the first embodiment. It is a characteristic view which shows the angle which the antenna and polarization form in 1st Example, and the relationship of detection sensitivity. It is a circuit diagram which shows an example of the principal part of the detection circuit of the terahertz wave intensity detection apparatus which concerns on 2nd Example.

<1>
The electromagnetic wave detection device according to the embodiment includes a first detection unit that outputs a first current based on an input of a reference voltage and a polarized electromagnetic wave, and the first detection unit has an electrical characteristic equivalent to at least the reference voltage. A second detection unit that outputs a second current based on the input of the first current, and an output unit that outputs the intensity of the electromagnetic wave based on the first and second currents, the second detection unit including the first current The second component of the second current output based on the input of the electromagnetic wave is smaller than the first component output based on the input of the electromagnetic wave. Here, a terahertz wave is mentioned as an example of electromagnetic waves. Examples of the first detection unit and the second detection unit include those using a Schottky barrier diode as a detection element.

  According to the present embodiment, for example, when an electromagnetic wave is incident on the first detection unit in a state in which a reference voltage as a bias voltage that gives an optimum bias current is applied, the first voltage corresponding to the reference voltage and the input of the incident electromagnetic wave. One current is output from the first detector. In parallel with or in parallel with this, a second current corresponding to at least the reference voltage is output from the second detector in a state where the reference voltage is applied.

  Here, for example, when such electromagnetic wave detection is performed by the first detection unit using a Schottky barrier diode as a detection element, even if the intensity of the electromagnetic wave is the same, if the operating temperature changes, the resistance of the detection element The value or impedance changes. As a result, the current output from the first detection unit also changes, and this change becomes a detection error. That is, it is difficult to obtain a correct detection result without depending on the operating temperature only by applying an optimum bias voltage or bias current.

  Furthermore, if the bias voltage is fixed so as to give an optimum bias current at a certain temperature, a bias current that deviates from the optimum bias current flows depending on the operating temperature, resulting in detection in a range other than the optimum or preferred dynamic range. obtain. That is, even if the correction for the change in current due to the change in operating temperature is performed on the current output from the first detection unit, the detection is performed in such a range other than the optimum or suitable dynamic range. However, there is a possibility that only detection with a low resolution and a large detection error can be performed.

  Therefore, first, the “reference voltage” according to the present embodiment is a reference voltage that gives an optimum bias current at any operating temperature, for example. Specifically, the “reference voltage” is preferably a variable value or the like according to the operating temperature, and ideally is set to a voltage that allows a bias current that can take the widest dynamic range. That is, the reference voltage is applied as a bias voltage to the first and second detection units so that the bias current flowing through the first and second detection units becomes the optimum bias current.

  Furthermore, in this embodiment, in order to reduce the detection error due to the change in operating temperature that occurs even in the situation where the optimum bias current is applied, not only from the current from a single detection unit, but also as described in detail below. The intensity of the electromagnetic wave is output from the first current and the second current.

  That is, at the time of electromagnetic wave detection, a first current is output from the first detection unit based on the input of the reference voltage and the polarized electromagnetic wave, and at least from the second detection unit whose electrical characteristics are equivalent to the first detection unit. When the second current is output based on the input of the reference voltage, the output unit outputs, for example, a differential output obtained by subtracting the second current from the first current or a specific output obtained by dividing the first current by the second current. As a result, the intensity of the electromagnetic wave (for example, an electrical signal indicating the intensity of the electromagnetic wave as a direct current value) is output. Here, “the electrical characteristics are equivalent” is not limited to the case where the electrical characteristics are exactly the same, but to detect the intensity of the electromagnetic wave output from the output unit, to the extent that the electrical characteristics are equal, It is a concept that includes cases where the electrical characteristics are close to each other.

  Therefore, even if the operating temperature changes, the bias currents flowing through the first detection unit and the second detection unit also change in the same or similar manner, and thus the first output current from these two units. Based on the current and the second current, it is possible to output in a form in which the change caused by the change in the operating temperature is at least partially offset or reduced.

  In addition, the second detection unit is configured to input the electromagnetic wave in the second current rather than the first component (more specifically, the current value of the first component) output based on the input of the electromagnetic wave in the first current. The second component (more specifically, the current value of the second component) output based on the output is arranged to be smaller.

  Here, the “first component” is an effective component for detecting the electromagnetic wave that changes according to the intensity of the electromagnetic wave that is the detection target output by the first detection unit. The first current includes the effective first component as described above and a fluctuation component that changes due to the operating temperature due to the bias current corresponding to the reference voltage (that is, ideally the optimum bias current) (hereinafter referred to as “first” as appropriate). Referred to as “one fluctuation component”). The first fluctuation component is an unnecessary component in detecting the electromagnetic wave.

  On the other hand, the “second component” changes according to the intensity of the electromagnetic wave to be detected, which may or may not be output by the second detector unintentionally. The component is not effective in detecting the electromagnetic wave. The second current has a second component that is not effective in this way and a fluctuation component that changes due to the operating temperature due to the bias current corresponding to the reference voltage (that is, ideally the optimum bias current) (hereinafter referred to as “first” as appropriate). Referred to as “2 fluctuation component”).

  Therefore, the smaller the second component, the better the detection of the electromagnetic wave. On the other hand, the second fluctuation component has a current value that is equal to or similar to that of the first fluctuation component. Therefore, the first fluctuation component that fluctuates according to the fluctuation of the operating temperature (that is, in detecting the electromagnetic wave, This is used to cancel or reduce unnecessary components.

  Typically, if the output unit adopts a specific configuration that outputs the intensity of the electromagnetic wave from the difference between the first current and the second current, such a second variation component makes it very simple and reliable, The first fluctuation component can be partially or substantially completely canceled out. Alternatively, if the output unit adopts a specific configuration for outputting the intensity of the electromagnetic wave from the ratio of the first current and the second current, the first fluctuation can be very easily and reliably caused by such a second fluctuation component. The component can be reduced.

  Note that the first component and the second component can each be regarded as changing according to the change in the operating temperature, but such a changing component is the first changing component that changes according to the change in the operating temperature. Are offset or reduced on the differential output or the specific output together with the fluctuation of the second fluctuation component and the fluctuation of the second fluctuation component. Alternatively, a component in which the first component fluctuates according to a change in operating temperature is regarded as a part of the first fluctuating component, and a component in which the second component fluctuates in accordance with a fluctuation in operating temperature is a second fluctuating component. In this case, as a part of the first fluctuation component and a part of the second fluctuation component, they are canceled or reduced on the differential output or the specific output. Regardless of which method is used, the components that vary in accordance with the variation in operating temperature related to the first component and the second component are canceled or reduced on the output by the output unit.

  Particularly in this embodiment, since the electromagnetic waves are polarized, the second component is smaller than the first component in this way by employing a simple optical arrangement by utilizing the polarization characteristics. Such an arrangement (ideally an arrangement in which the second component is extremely smaller, more ideally the arrangement in which the second component is close to zero) can be realized very easily. For example, by adopting an optical arrangement using such polarization characteristics, the second detector is arranged so that the second component is smaller than the first component. According to the relative smallness with respect to the first component, the detection accuracy can be increased.

  “The second detector” is “arranged like...” Means the relative arrangement of the second detector with respect to the first detector, and “the first and second detectors”. May be rephrased as “arranged like ...”.

  As a result, the second component is smaller than the first component for the component that changes according to the intensity of the electromagnetic wave to be detected by the arrangement of the second detection unit. By taking the current difference, ratio, and the like, it is possible to reduce or reduce detection errors caused by changes in operating temperature. In addition, it is very easy to adopt a configuration in which an optimum bias current is applied to the first and second detectors in accordance with the operating temperature, and detection in the optimum or suitable dynamic range is possible. In addition, detection with a high resolution and a small detection error can be performed.

  As a result, the influence of the temperature change can be suppressed, and a highly accurate detection result can be obtained without depending on the operating temperature.

<2>
In one aspect of this embodiment, the electromagnetic wave detection device has a predetermined current value or a current value within a predetermined range for the reference voltage, a current component output based on the input of the reference voltage in the second current. Bias voltage applying means is further provided so as to flow as a bias current.

  According to this aspect, the bias voltage applying means applies the reference voltage such that the current component output by the reference voltage is the optimum bias current to the first and second detection units, thereby increasing the operating temperature. Regardless of this, the optimum bias current can be supplied to the first and second detection units. As a result, the detection accuracy can be improved by using an optimal or suitable dynamic range for the electromagnetic wave to be detected with a relatively easy apparatus configuration and method.

  With respect to the “reference voltage” according to this aspect, the dynamic range can be widened, and in addition to or instead, the linearity at the time of detection can be increased, or the detection gain sensitivity can be increased, the DC offset can be suppressed, and the temperature characteristics It is preferable to set the optimum value according to the operating temperature so as to suppress the detection error based on the change due to the difference, suppress the detection error due to individual differences, and improve the detection accuracy as a whole. By adopting a configuration in which the reference voltage is set and the output is obtained from the first and second currents in this way, detection errors due to individual differences in the detection units can be easily reduced.

  Applying a bias voltage in this way from the bias voltage application means enables detection at an optimum or suitable dynamic range or a range as close as possible at any operating temperature. This is extremely effective for the purpose of reducing the error.

<3>
In another aspect of the present embodiment, the output unit outputs a difference between the first and second currents as the intensity.

  According to this aspect, at the time of electromagnetic wave detection, the output unit outputs the intensity of the electromagnetic wave as a differential output obtained by subtracting the second current from the first current. Here, the change in current in the first and second detectors due to the change in the operating temperature changes in the same or similar manner, and thus by taking the difference in this way, the change is at least Output in a partially offset form is possible. Thereby, the influence of a temperature change can be suppressed easily and reliably. Further, by adopting a configuration in which the difference is output in this way while setting the reference voltage as described above, the detection error due to the individual difference of the detection unit can be easily reduced.

  Outputting the difference in this manner at the output unit is extremely effective for the purpose of simply and efficiently canceling out detection errors due to changes in operating temperature.

<4>
In another aspect of this embodiment, the detection directions of the electromagnetic waves are different in the first and second detection units so that the second component is smaller than the first component, respectively. .

  According to this aspect, by utilizing the polarization characteristics, it is possible to extremely easily arrange such that the second component is smaller than the first component by adopting a simple optical arrangement. realizable. For example, the second detection unit is arranged so that the second component is ideally reduced to zero or close to zero.

<5>
In this aspect, the first and second detection units may be arranged such that the detection directions of the electromagnetic waves form an angle of 72 degrees to 108 degrees with each other on the same plane.

  With this configuration, the detection sensitivity is proportional to the square of COSθ (where θ is the angle formed by the detection directions of the first and second detection units), and therefore the sensitivity of the second component is the sensitivity of the first component. Compared to the above, it becomes 1/10 or less. Therefore, in the output unit, by using the second current including the second component that is suppressed to be less than one-tenth of the first component, it is detected from the first current and the second current in a practical sense. It is possible to output the intensity of the electromagnetic wave suppressed to such an extent that the error can be ignored.

<6>
In another aspect of the present embodiment, the first and second detection units include a semiconductor element in which anodes or cathodes are integrally connected on the same substrate.

  According to this aspect, the first and second detection units that are relatively easy to manufacture, have a relatively simple structure, and have equivalent electrical characteristics, for example, by a planar technology that is a semiconductor manufacturing technology. (Particularly, the detection element portion) can be constructed.

<7>
In this aspect, the electromagnetic wave is a terahertz wave, and the semiconductor element may include a Schottky barrier diode.

  According to this aspect, the terahertz wave can be detected with high accuracy without depending on the operating temperature of the Schottky barrier diode. In particular, since the output is obtained from the first and second currents while the optimum bias current is applied, it is possible to detect electromagnetic waves with very high accuracy.

<8>
In another aspect of the present embodiment, the electromagnetic wave detection device further includes polarization means arranged in the traveling path of the electromagnetic wave reaching the first and second detection units.

  According to this aspect, since the electromagnetic waves are polarized by, for example, a polarizing means such as a polarizer, the first component can be used as described above by employing a simple optical arrangement by utilizing the polarization characteristics. An arrangement that makes the second component smaller (ideally, an arrangement that makes the second component extremely smaller, more ideally an arrangement that makes the second component close to zero) is extremely easy. Can be realized. For example, by adopting a relative optical arrangement of the first and second detection units using polarization characteristics, it becomes possible to increase detection accuracy according to the relative smallness of the second component. .

  The effect | action and other gain of this embodiment are clarified from the Example demonstrated below.

  Embodiments of the electromagnetic wave detection device of the present invention will be described with reference to the drawings. In the following examples, a “terahertz wave intensity detection device” is cited as an example of an “electromagnetic wave detection device” according to the present invention. An example of the “electromagnetic wave” according to the present invention is “terahertz wave”.

<First embodiment>
A first embodiment of the terahertz wave intensity detection device will be described with reference to FIGS. In the terahertz wave intensity detection device 1 according to the first embodiment, a Schottky barrier diode is used as a terahertz wave detection element.

(Schottky barrier diode)
First, the features of the Schottky barrier diode and the outline of each terahertz wave intensity detection method using the Schottky barrier diode will be described with reference to FIGS. FIG. 1 is a diagram illustrating an example of voltage-current characteristics for each intensity of a terahertz wave incident on a Schottky barrier diode. FIG. 2 is a diagram illustrating an example of a temperature change of the voltage-current characteristic of the Schottky barrier diode. FIG. 3 is a conceptual diagram showing a terahertz wave intensity detection method using a Schottky barrier diode.

  As shown in FIG. 1, as the intensity of the terahertz wave incident on the Schottky barrier diode decreases, the current generated in the Schottky barrier diode also decreases. In particular, when a bias voltage is not applied to the Schottky barrier diode (see the broken line indicating voltage 0 in FIG. 1), when the intensity of the incident terahertz wave becomes weak, the current generated in the Schottky barrier diode approaches 0, Terahertz wave intensity cannot be detected.

  By applying a bias voltage to the Schottky barrier diode, even if the intensity of the terahertz wave incident on the Schottky barrier diode is weak, a detectable current can be generated in the Schottky barrier diode (in FIG. 1). (See broken line showing voltage V).

  However, as shown in FIG. 2, the voltage-current characteristic of the Schottky barrier diode has temperature dependence. For this reason, if the bias voltage is fixed, even if no terahertz wave is incident on the Schottky barrier diode, the current generated in the Schottky barrier diode changes due to a temperature change (voltage) V and currents I1, I2 and I3).

  Here, a terahertz wave intensity detection method will be described with reference to FIG. When a voltage Vf is applied as a bias voltage to the Schottky barrier diode and no terahertz wave is incident on the Schottky barrier diode, a current generated in the Schottky barrier diode is defined as a current If.

  Assuming that the current generated in the Schottky barrier diode when the terahertz wave is incident on the Schottky barrier diode is the current Its, the difference Isig between the current Its and the current If is the current increased due to the terahertz wave. Become. As described above, the current flowing through the Schottky barrier diode also changes according to the intensity of the terahertz wave incident on the Schottky barrier diode. For this reason, the intensity of the terahertz wave can be detected from the difference Isig between the current Its and the current If.

  In particular, as is apparent from FIGS. 1 to 3, when the bias voltage V is applied, the increase / decrease of the current increases according to the intensity of the terahertz wave, compared to the case where the bias voltage is 0. ing. That is, the dynamic range in detection is increased.

  In particular, as is clear from FIG. 2, if the current generated in the Schottky barrier diode changes due to a temperature change, simply from the current value flowing through one Schottky barrier diode, The intensity of the terahertz wave cannot be detected correctly. Therefore, in this embodiment, as will be described in detail later, the difference between the currents from the two Schottky barrier diodes is adopted as the current value indicating the electromagnetic wave intensity.

  In addition, the “voltage Vf” according to the present embodiment shown in FIG. 3 means a bias voltage for supplying an optimum bias current that gives an optimum or suitable dynamic range at a certain operating temperature or operating temperature range. A reference voltage is applied to the two Schottky barrier diodes. For such a bias voltage, the dynamic range can be widened, and in addition or instead, the linearity at the time of detection can be increased, or the detection gain sensitivity can be increased, the DC offset can be suppressed, and the change due to temperature characteristics can be achieved. It is preferable to set the optimum value according to the operating temperature or the operating temperature range so that the detection error based on the difference can be suppressed, the detection error due to individual differences can be suppressed, and the detection accuracy can be improved as a whole. Such a setting can be achieved by, for example, optimizing the bias current value (or the optimum bias current value) that can improve the detection accuracy from the above-mentioned various viewpoints for each individual (that is, each detection unit including each individual Schottky barrier diode). (Bias voltage value for supplying the bias current) is specifically obtained experimentally, empirically, or by simulation, and the voltage (or bias voltage set for each temperature) for supplying the optimum bias current is actually detected. What is necessary is just to employ | adopt as a reference voltage in. Typically, the voltage is variable according to the operating temperature or a voltage set for each temperature. Further, by adopting a configuration in which the reference voltage is set and the output is obtained from the first and second currents in this way, in this embodiment, as described in detail below, the detection error due to the individual difference of the detection unit is reduced. Can be reduced easily.

(Terahertz wave intensity detector)
Next, a specific configuration of the terahertz wave intensity detection device will be described with reference to FIGS.

In FIG. 4, a detection optical system including a Schottky barrier diode constituting the terahertz wave intensity detection device according to the embodiment and a polarizer as an example of the “polarization means” according to the present invention is a terahertz transmitter. 101, the collimating lens 102 and the objective lens 103 are provided, and the terahertz wave 100 is irradiated to the measurement test 200 from the terahertz transmitter 101 through the collimating lens 102 and the objective lens 103 in this order. The detection optical system further includes an objective lens 104, a polarizer 105, a collimating lens 106, and Schottky barrier diodes D1 and D2. The terahertz wave 100 from the measurement test 200 is converted into the objective lens 104, the polarizer 105, and the collimating lens 106. It is configured to irradiate the Schottky barrier diodes D1 and D2 in order. The polarizer 105 is configured to emit a terahertz wave polarized in one specific direction by transmission or reflection.

  The Schottky barrier diode D1 is an example of a detection element included in the “first detection unit” according to the present invention, and the Schottky barrier diode D2 is a detection element included in the “second detection unit” according to the present invention. This constitutes an example. As will be described in detail later, in the Schottky barrier diode D1, the polarization direction by the polarizer 105 and the detection direction are parallel to each other, and the Schottky barrier diode D2 has a polarization direction and a detection direction by the polarizer 105. Orthogonal. Here, the term “parallel” means that it is sufficient that the deviation from the parallel in terms of accuracy in detecting the terahertz wave 100 in this embodiment is parallel enough to generate a detection error that can be ignored in practice. Is completely parallel, but in practice it is sufficient to be parallel. On the other hand, the term “orthogonal” means that the orthogonality is sufficient to generate a detection error that can be ignored in practice in terms of accuracy when detecting the terahertz wave 100 in this embodiment. Are completely orthogonal, but it is sufficient that they are orthogonal in a practical sense (these will be described later with reference to FIG. 11 and the like).

  The terahertz wave intensity detection device 1 including the Schottky barrier diodes D1 and D2 illustrated in FIG. 4 includes the circuit illustrated in FIG.

  In FIG. 5, “OA1” represents an example of an operational amplifier. The detection direction of the Schottky barrier diode D2 is orthogonal to the polarized terahertz wave. The detection direction of the Schottky barrier diode D1 is parallel to the polarized terahertz wave. The difference voltage detection unit 50 constituting an example of the “output unit” according to the present invention obtains a difference between currents flowing through these Schottky barrier diodes D1 and D2, thereby allowing the terahertz wave intensity detection device 1 according to the present embodiment. Is configured to reduce the adverse effects of the change in operating temperature on the detection result regardless of whether or not the terahertz wave is incident.

  That is, in this embodiment, the electrical characteristics of the Schottky barrier diode D1 and the electrical characteristics of the Schottky barrier diode D2 are equivalent. In addition, the Schottky barrier diode D1 is placed in a thermal environment close to the thermal environment in which the Schottky barrier diode D2 is placed. These can be easily achieved by forming Schottky barrier diodes D1 and D2 close to each other as described later (preferably, cathodes or anodes are formed in common).

  The differential voltage detection unit 50 illustrated in FIG. 5 includes, for example, the circuit illustrated in FIG.

  In FIG. 5, in the terahertz wave intensity detection device 1, during measurement of terahertz waves (THz waves), a voltage Vf is applied as a bias voltage so that a predetermined current value If is generated in the Schottky barrier diode D2. Specifically, the resistance value between the positive electrode of the DC power supply and the positive input terminal of the operational amplifier OA1 is “R1”, and the potential of the positive electrode of the DC power supply is set to “V1 = If × R1 + Vf”. The potential of the negative input terminal of the differential voltage detector 50 is “V1”.

  When a terahertz wave (THz wave) is incident on the Schottky barrier diode D1, the current generated in the Schottky barrier diode D1 is “Its”, and the resistance between the output terminal of the operational amplifier OA1 and the negative input terminal of the operational amplifier OA1 The value is “R1”. The potential V2 of the output terminal of the operational amplifier OA1 can be expressed as “V2 = Its × R1 + Vf”. The potential of the positive input terminal of the differential voltage detector 50 is “V2”, and the potential of the negative input terminal of the differential voltage detector 50 is “V1”. Then, the differential voltage detection unit 50 outputs a signal indicating “V2−V1 = Its × R1 + Vf− (If × R1 + Vf) = Its × R1−If × R1 = Isig × R1”. Since the resistance value R1 is known, the intensity of the terahertz wave incident on the Schottky barrier diode D1 is detected from the output of the differential voltage detector 50. At this time, the level of the bias voltage Vf does not relate to the differential output from the differential voltage detector 50.

  As described above, in the first embodiment, an example of the “bias voltage applying unit” according to the present invention includes the DC power supply that supplies V1 and the operational amplifier OA1, and an example of the “output unit” according to the present invention. Is configured to include the differential voltage detector 50.

  Next, an example of a specific element structure of the Schottky barrier diodes D1 and D2 will be described with reference to FIGS.

  As shown in FIG. 7, in a semiconductor element including a Schottky barrier diode D1 (or D2), a heavily doped n-type semiconductor 11, an n-type semiconductor 12, a Schottky electrode 13, and an ohmic electrode 14 are formed on a semiconductor substrate 10. These are stacked in this order. The semiconductor is formed by, for example, epitaxial growth.

The semiconductor substrate 10 is a semiconductor wafer made of, for example, InP. The heavily doped n-type semiconductor 11 is mainly composed of, for example, InGaAs by epitaxial growth, the In composition is 53%, the dopant is Si, and the doping amount is 2 × 10 ¹⁸ [atoms / Cm ³ ] or more. . The n-type semiconductor 12 is mainly composed of, for example, InGaAs by epitaxial growth, the In composition is 53%, the dopant is Si, and the doping amount is 1 × 10 ¹⁶ to 1 × 10 ¹⁸ [atoms / Cm ³ ]. The The Schottky electrode 13 is mainly composed of, for example, Al or Ti. The ohmic electrode 14 is mainly composed of, for example, an AuGeNi alloy.

  Further, as shown in the plan view of FIG. 8, each layer is provided with the Schottky electrode 13 of FIG. 7 on the Schottky barrier diodes D1 and D2, respectively, and the cathode 16 and the anode 17 of the Schottky barrier diode D1, and the Schottky barrier. Patterning is performed so that the anode 17 and the cathode 18 of the diode D2 are provided (see FIG. 8A). As a result, as shown in FIG. 5, the circuit portions of the Schottky barrier diodes D1 and D2 are constructed on the same substrate (see FIG. 8B corresponding to FIG. 8A). In particular, the anodes of the two Schottky barrier diodes D1 and D2 are integrally connected (in other words, both anodes are common). The two Schottky electrodes 13 are configured to have the same shape.

  Next, with reference to FIGS. 9 and 10, the structure of the antenna that defines the detection directions of the Schottky barrier diodes D1 and D2 will be described.

  As shown in FIG. 10, on the same plane, the antenna AN1 has a detection direction arranged along the X direction, and the antenna AN2 has a detection direction arranged along the Y direction. That is, the antenna AN1 and the antenna AN2 are constructed as dipole antennas arranged so that the detection directions are orthogonal to each other in the same plane.

  Further, such antennas 1 and 2 are arranged on the ohmic electrode (see FIGS. 7 and 8) of the Schottky barrier diode D1 (or D2). As a result, the detection direction of the Schottky barrier diode D1 and the detection direction of the Schottky barrier diode D2 are arranged to be orthogonal to each other in the same plane. Therefore, the terahertz wave polarized in the X direction via the polarizer 105 shown in FIG. 4 is detected with a detection sensitivity close to 100% in the Schottky barrier diode D1, and 0% in the Schottky barrier diode D2. The detection sensitivity is close to. That is, in the Schottky barrier diode D2 whose detection direction is the Y direction, the terahertz wave 100 shown in FIG. 4 is hardly detected. For example, theoretically, if the “width” (see FIG. 9) of the antenna AN2 is zero, the Schottky barrier diode D2 shown in FIG. 10 does not detect any terahertz wave polarized in the X direction. .

  As shown in FIGS. 8 and 10, under the situation where the anodes are connected and used as a circuit (see FIG. 5), according to this embodiment, the anodes are integrated continuously from the beginning. Since it is formed, the manufacturing efficiency when manufacturing each layer on the semiconductor substrate as shown in FIG. 7 is very high. Alternatively, even when a circuit configuration in which the cathodes are integrally formed continuously by reversing the characteristics of the semiconductor element used in this embodiment, the efficiency in manufacturing each layer is increased.

  In addition, as shown in FIGS. 8 and 10, since the two Schottky barrier diodes D1 and D2 are arranged close to each other, it is easy to equalize their electrical characteristics. In particular, when each layer is manufactured on a semiconductor substrate as shown in FIG. 7, the characteristics of the semiconductor differ depending on the position in the surface of the semiconductor wafer constituting the semiconductor substrate. The arrangement is very useful in reducing the difference in electrical characteristics. Further, the close arrangement as described above is very advantageous in applications where a plurality of devices as shown in FIG. 10 are arranged in a high density in an array or matrix.

  As shown in FIG. 11, the detection sensitivity of the Schottky barrier diodes D1 and D2 is an angle θ formed by the antennas AN1 and AN2 that are the detection directions of the Schottky barrier diodes D1 and D2 and the polarization direction by the polarizer 105. It depends. In this embodiment, as described with reference to FIGS. 8 to 10 and the like, this angle θ coincides with the angle θ formed by the detection directions of D1 and D2 of the two Schottky barrier diodes. More specifically, as is apparent from FIG. 11, the detection sensitivity is proportional to the square of COSθ. Therefore, if it is in the range of θ = 72 degrees to 108 degrees, the terahertz wave is generated by the Schottky barrier diode D2. The sensitivity when the current due to the current is detected is 1/10 or less compared with the sensitivity when the current due to the terahertz wave is detected by the Schottky barrier diode D1.

  Therefore, since the difference voltage detection unit 50 (see FIGS. 5 and 6) outputs the difference between the detected currents from D1 and D2 of the two Schottky barrier diodes, the detection of D1 and D2 of the two Schottky barrier diodes is performed. In practice, if the angle is in the range of 72 to 108 degrees (although ideally at an angle of 90 degrees to each other), sufficient detection accuracy can be obtained.

(Technical effect)
Particularly in the first embodiment, the current generated in the Schottky barrier diode D2 when the terahertz wave is hardly incident by the action of the polarizer 105 (see FIG. 4) can always be set to the predetermined current value If. Therefore, the influence of the temperature change on the detection result of the terahertz wave intensity detection device 1 can be suppressed.

  The “Schottky barrier diode D1” according to the example is an example of a detection element that constitutes the “first detection unit” according to the present invention. The “Schottky barrier diode D2” according to the embodiment is an example of a detection element constituting the “second detection unit” according to the present invention.

<Second embodiment>
Next, a terahertz wave intensity detection device according to a second embodiment will be described with reference to FIG. The second embodiment is the same as the first embodiment described above except that a part of the configuration of the terahertz wave intensity detection device is different. Therefore, in the second embodiment, the description overlapping with that of the first embodiment is omitted, and common portions in the drawing are denoted by the same reference numerals, and only differences are basically described with reference to FIG. To do. FIG. 12 is a diagram illustrating an example of a main part of the detection circuit of the terahertz wave intensity detection device according to the second embodiment.

(Terahertz wave intensity detector)
The terahertz wave intensity detection device 2 has a circuit shown in FIG. In FIG. 12, “OA3” and “OA4” are operational amplifiers. In the terahertz wave intensity detection device 2, the resistance value between the positive electrode of the DC power supply and the negative input terminal of the operational amplifier OA4 is set to “R2”, and the potential of the positive electrode of the DC power supply is set to “V3 = If × R2”. The

  As shown in FIG. 12, since the negative input terminal of the operational amplifier OA4 and the output terminal of the operational amplifier OA4 are electrically connected via the Schottky barrier diode D2, the potential V− of the negative input terminal of the operational amplifier OA4. And the potential V + of the positive input terminal of the operational amplifier OA4 become the same potential (here, the ground potential).

  As shown in FIG. 12, a predetermined current value If flows through the Schottky barrier diode D2 disposed between the negative input terminal of the operational amplifier OA4 and the output terminal of the operational amplifier OA4. Therefore, the voltage Vf that generates the predetermined current value If is applied as a bias voltage to the Schottky barrier diode D2.

  As described above, since the potential V− of the negative input terminal of the operational amplifier OA4 (that is, the potential on the anode side of the Schottky barrier diode D2) is the ground potential, the potential V4 of the output terminal of the operational amplifier OA4 (in other words, the shot potential) The potential on the cathode side of the key barrier diode D2 is “−Vf”. Therefore, the potential on the cathode side of the Schottky barrier diode D1 is also “−Vf”.

  As shown in FIG. 12, since the negative input terminal of the operational amplifier OA3 and the output terminal of the operational amplifier OA3 are electrically connected, the potential V− of the negative input terminal of the operational amplifier OA3 and the positive input of the operational amplifier OA3. The potential V + of the terminal becomes the same potential. Here, since the potential V + of the positive input terminal of the operational amplifier OA3 is equal to the potential on the anode side of the Schottky barrier diode D2, it is a ground potential. As a result, the potential V− of the negative input terminal of the operational amplifier OA3, in other words, the potential on the anode side of the Schottky barrier diode D1 also becomes the ground potential. That is, the voltage Vf is applied as a bias voltage to the Schottky barrier diode D1.

  When a terahertz wave enters the Schottky barrier diode D1, a current Its (Its> If) is generated in the Schottky barrier diode D1. At this time, the current flowing through the resistor (resistance value R3) between the negative input terminal of the operational amplifier OA3 and the output terminal of the operational amplifier OA3 becomes “Its-If” according to Kirchhoff's law, and the output of the circuit shown in FIG. The voltage is “(Its−If) × R3 = Isig × R3”. Since the resistance value R3 is known, the intensity of the terahertz wave incident on the Schottky barrier diode D1 is detected from the output of the operational amplifier OA3. At this time, the level of the bias voltage Vf does not relate to the differential output from the operational amplifier OA3.

  As described above, in the second embodiment, an example of the “bias voltage applying unit” according to the present invention includes the DC power supply that supplies V3 and the operational amplifier OA4, and an example of the “output unit” according to the present invention. Includes an operational amplifier OA3.

  The present invention is not limited to the above-described embodiments or examples, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. The detection device is also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 1, 2 ... Terahertz wave intensity detection apparatus, D1, D2 ... Schottky barrier diode, OA1, OA3, OA4 ... Operational amplifier, 50 ... Difference voltage detection part, 105 ... Polarizer

Claims (8)

A first detector that outputs a first current based on an input of a reference voltage and a polarized electromagnetic wave;
A second detector that is electrically equivalent to the first detector and outputs a second current based on at least the input of the reference voltage;
An output unit that outputs the intensity of the electromagnetic wave based on the first and second currents,
In the second detection unit, the second component output based on the input of the electromagnetic wave in the second current is smaller than the first component output based on the input of the electromagnetic wave in the first current. An electromagnetic wave detection device arranged to be   Bias voltage applying means for applying the reference voltage so that a current component output based on the input of the reference voltage in the second current flows as a bias current having a predetermined current value or a current value within a predetermined range. The electromagnetic wave detection device according to claim 1, further comprising:   The electromagnetic wave detection apparatus according to claim 1, wherein the output unit outputs a difference between the first and second currents as the intensity.   The detection directions of the electromagnetic waves are different from each other so that the first and second detection units are smaller in the second component than in the first component, respectively. The electromagnetic wave detection device according to any one of claims 3 to 4.   5. The electromagnetic wave detection according to claim 4, wherein the first detection unit and the second detection unit are arranged so that detection directions of the electromagnetic wave form an angle of 72 degrees to 108 degrees with each other on the same plane. apparatus.   The said 1st and 2nd detection part is comprised including the semiconductor element by which anodes or cathodes were integrally connected on the same board | substrate, The any one of Claim 1 to 5 characterized by the above-mentioned. The electromagnetic wave detection apparatus of description. The electromagnetic wave is a terahertz wave,
The electromagnetic wave detection device according to claim 6, wherein the semiconductor element includes a Schottky barrier diode.   The electromagnetic wave detection device according to any one of claims 1 to 7, further comprising a polarization unit disposed in a traveling path of the electromagnetic wave reaching the first and second detection units.