JP2007103997A - Electromagnetic wave emission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave emission device capable of irradiating electromagnetic waves toward a desired direction by a simple structure. <P>SOLUTION: The device includes an optical beat signal generation section 1 for generating an optical beat signal; an optical branching section 2 for allowing the optical beat signal to branch into n channels; an optical delay circuit 3 for independently adjusting the amount of delay in the optical beat signal of n channels input from the optical branching section 2; a terahertz wave radiation source 6 in which n terahertz wave radiation elements, which receive the optical beat signal from the optical delay circuit 3 for irradiating terahertz waves, are arranged in an array; and a control section 9 that controls the amount of delay in the optical beat signal of n channels output from the optical delay circuit 3 for controlling the phase of the terahertz waves irradiated by the terahertz wave radiation element each, and hence controls the direction of the terahertz waves irradiated by the terahertz wave radiation source 6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electromagnetic wave radiation device that generates an electromagnetic wave of a terahertz wave band from a millimeter wave band used for imaging and material analysis.

  For example, Non-Patent Document 1 discloses a conventional electromagnetic wave radiation device. FIG. 5 is a block diagram showing a conventional electromagnetic wave emission device, and FIG. 6 is a view showing the back surface of the silicon layer of the electromagnetic wave emission device shown in FIG.

  The electromagnetic wave emission device shown in FIG. 5 is electrically connected to the sapphire substrate 101, the silicon layer 102 which is attached to the sapphire substrate 101 and is ion-implanted, the hemispherical lens 103 made of MgO, and the back surface pattern of the silicon layer 102. It includes a bonding wire 104 for taking, a femtosecond pulse laser 105, a power source 106, an optical system 107 for collimating femtosecond pulse laser light, and a parabolic reflection mirror 108 for collimating terahertz electromagnetic waves.

  Further, as shown in FIG. 6, an ion-implanted silicon layer 102 is provided on the back surface of the sapphire substrate 101, and a dipole antenna pair 109 with a minute gap 111 is formed on the front surface by aluminum wiring.

  A circle 110 indicated by a dotted line is a line indicating the positional relationship between the hemispherical lens 103 installed on the surface side of the sapphire substrate 101 and the minute gap 111 of the dipole antenna pair 109. The dipole antenna pair 109 is made conductive by the bonding wire 104 and a voltage is applied from the power source 106.

  The femtosecond pulse light generated from the femtosecond pulse laser 105 is applied to the minute gap 111 of the dipole antenna pair 109 by the collimating optical system 107. Since carriers generated in the silicon layer 102 by light irradiation move due to an applied electric field, a displacement current is generated in the dipole antenna pair 109. This displacement current coincides with the pulse width of the femtosecond laser irradiated with the rising edge, and includes a frequency component in the terahertz band.

Therefore, the dipole antenna pair 109 functions as a terahertz wave radiator and irradiates the terahertz wave in the direction of the sapphire substrate 101. The terahertz wave that has passed through the sapphire substrate 101 is radiated in the direction of the parabolic reflection mirror 108 with the radiation angle θ narrowed by the hemispherical lens 103. Then, the radiation direction is bent 90 degrees by the parabolic reflection mirror 108 and collimated into a parallel beam.
High-brightness terahertz beams characterized with an ultrafast detector, Martin van Exter, CH. Fattinger, and D. Grischkowsky, Applied Physics Letters, Vol. 55 (4), 24 july 1989.

  In the electromagnetic wave emission device shown in FIG. 5, in order to change the direction of the collimated terahertz beam, one of the following (1) and (2) must be performed.

(1) The collimating optical system 107 to the parabolic reflection mirror 108 are integrated and mounted on a movable stage, and this is moved.

(2) The parabolic reflection mirror 108 is provided with an angle adjustment function that enables a complicated movement that allows the beam to be steered while keeping the output beam parallel.

  However, there is a problem that all of them require a complicated optical system.

  The present invention has been made in view of the above, and an object thereof is to provide an electromagnetic wave radiation device capable of radiating an electromagnetic wave in a desired direction with a simple structure.

  In order to achieve the above object, an invention according to claim 1 is an electromagnetic wave emission device for emitting an electromagnetic wave having at least one wavelength among electromagnetic waves in a wavelength band ranging from a millimeter wave band to a terahertz wave band. An optical beat signal generating means for generating, an optical branching means for branching the optical beat signal into n channels, and a delay amount of the optical beat signal of the n channel branched by the optical branching means are independently adjusted and output. An optical delay means for receiving the optical beat signal from the optical delay means, an electromagnetic wave radiation source for radiating electromagnetic waves in an array, and an n-channel output from the optical delay means By controlling the delay amount of the optical beat signal, the phase of the electromagnetic wave radiated by the electromagnetic wave radiating element is respectively controlled. There is characterized in that a control means for controlling the direction of the electromagnetic wave radiation.

  According to a second aspect of the present invention, the electromagnetic wave radiating element includes a photoelectric conversion unit that generates a high-frequency current in response to the optical beat signal, and a second electromagnetic wave corresponding to the high-frequency current generated by the photoelectric conversion unit. And a planar antenna for radiating the light.

  The invention according to claim 3 is characterized in that the planar antenna radiates an electromagnetic wave in the same direction as the traveling direction of the optical beat signal applied to the photoelectric conversion means.

  According to a fourth aspect of the present invention, there is provided an electromagnetic wave radiation device that radiates an electromagnetic wave having at least one wavelength among electromagnetic waves in a wavelength band ranging from a millimeter wave band to a terahertz wave band. An electromagnetic wave radiation source arranged, and a control means for controlling the direction of the electromagnetic wave emitted from the electromagnetic wave radiation source by respectively controlling the phase of the electromagnetic wave emitted from the plurality of electromagnetic wave radiation elements.

  According to the present invention, a plurality of electromagnetic wave radiating elements that radiate electromagnetic waves are arranged in an array, and the direction of the electromagnetic waves radiated from the electromagnetic wave radiation source is controlled by adjusting the phase of the electromagnetic waves radiated by the respective electromagnetic wave radiating elements. Therefore, it is possible to provide an electromagnetic wave radiation device that can radiate an electromagnetic wave in a desired direction with a simple structure.

  The best mode for carrying out the electromagnetic wave emission device of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an electromagnetic wave radiation device according to an embodiment of the present invention.

  As shown in FIG. 1, the electromagnetic wave emission device according to the present embodiment is input from an optical beat signal generator 1 that generates an optical beat signal that generates a terahertz wave by photoelectric conversion, and an optical beat signal generator 1. It has an optical branching unit 2 that branches an optical beat signal into n channels and n phase shifters 31 to 3n, and independently adjusts the delay amount of the n-channel optical beat signal input from the optical branching unit 2 An optical delay circuit 3, an n-channel two-dimensional optical fiber array 4, a collimator lens 5 that collimates an n-channel optical beat signal emitted from the two-dimensional optical fiber array 4, and a terahertz wave radiating element in an array. A terahertz wave radiation source 6 in which n elements are arranged, a radiation source mounter 7 having a hole in the center and configured to irradiate the terahertz wave radiation source 6 with light from the back surface, A power supply 8 for applying a bias voltage to n terahertz wave radiating elements of the terahertz radiation source 6 and a control unit for controlling the optical delay circuit 3 and controlling the direction of the terahertz wave emitted from the terahertz wave radiation source 6. 9. In the following, n = 9.

  FIG. 2 is a block diagram showing a terahertz wave radiation source of the electromagnetic wave radiation device shown in FIG. As shown in FIG. 2, the terahertz radiation source 6 includes an InP substrate 61, a low dielectric layer 62 formed on the InP substrate 61, and patch antennas 631 to 639 on the low dielectric layer 62 in 3 rows × 3. A patch antenna array 63 formed side by side and an electrode pad 64 for supplying a DC voltage to a power feeding element existing below the low dielectric layer 62 are provided.

  FIG. 3 is a diagram showing a feed element under the patch antenna, and FIG. 4 is a circuit diagram of the feed element. Since all the feeding elements of the patch antennas 631 to 639 have the same configuration, the feeding element of the patch antenna 631 is illustrated as an example. As shown in FIGS. 3 and 4, the power feeding element 69 includes a ground electrode 65 formed on the InP substrate 61 and a high-frequency current that is formed on the InP substrate 61 and oscillates at an appropriate frequency in response to the optical beat signal. The backside light incident type single traveling carrier photodiode 66 that is generated, the transmission line 67 that transmits the high-frequency current generated by the single traveling carrier photodiode 66, and the high-frequency current that has been transmitted through the transmission line 67 are reduced to the low dielectric layer 62. And a via hole 68 that is transmitted to the patch antenna 631.

  This structure can be produced by subjecting a compound semiconductor heterojunction structure epitaxially grown on the semi-insulating InP substrate 61 to normal photolithography, etching, metal lift-off, and the like. As an example, if the patch antenna 631 is 240 microns × 240 microns, the patch antenna 631 has a resonance frequency near 300 GHz.

  Here, the operation of the electromagnetic wave emission device of the present exemplary embodiment will be described. First, the optical beat signal generation unit 1 generates an optical beat signal that generates a terahertz wave by photoelectric conversion, and outputs the optical beat signal to the optical branching unit 2.

  Next, the optical branching unit 2 branches the optical beat signal input from the optical beat signal generating unit 1 into 9 channels, and outputs them to the phase shifters 31 to 39 of the optical delay circuit 3, respectively.

  After that, the phase shifters 31 to 39 independently adjust the delay amount of the optical beat signal input from the optical branching unit 2 based on the control instruction from the control unit 9, and then 3 × 3 two-dimensional light An optical beat signal is radiated to the collimating lens 5 via the fiber array 4.

  The collimating lens 5 collimates the optical beat signal and irradiates the terahertz wave radiation source 6 from the back surface. Here, the optical beat signals emitted from the respective optical fibers of the two-dimensional optical fiber array 4 are applied to the feeding elements of the patch antenna at diagonal positions.

  The single traveling carrier photodiode 66 of the feed element 69 receives the optical beat signal and generates a high-frequency current that vibrates at a corresponding frequency. This high-frequency current is transmitted to the patch antenna 631 via the transmission line 67 and the via hole 68. The patch antenna 631 secondarily radiates a terahertz wave corresponding to the high-frequency current into the air. Similarly, terahertz waves are radiated from the patch antennas 631 to 639.

  The terahertz waves radiated from the patch antennas 631 to 639 arranged in an array interfere with each other and are radiated strongly only in a specific direction. Therefore, the control unit 9 controls the radiation distribution of the interference wave by controlling the phase for exciting the patch antennas 631 to 639, and controls the radiation direction of the terahertz wave.

  Here, the control unit 9 controls the optical delay amount given to each channel by the phase shifters 31 to 39 so that the terahertz waves radiated from the nine patch antennas 631 to 639 are narrowed in one arbitrary direction. To do.

  As described above, according to the electromagnetic wave radiation device of the present embodiment, the radiation direction of the terahertz wave radiated from the patch antenna array 63 is controlled by controlling the delay of each optical beat signal that excites the patch antennas 631 to 639. Since it can be radiated as a convergent beam defined in a specific direction, the terahertz wave is directed in a desired direction without moving the terahertz wave radiation source 6 and without using a complicated optical system such as a movable mirror. It becomes possible to launch.

  In addition, since the terahertz wave is radiated by the patch antenna 631 disposed at a position facing the single traveling carrier photodiode 66 and the low dielectric layer 62, the optical beat signal of the single traveling carrier photodiode 66 is irradiated. The traveling direction and the radiation direction of the terahertz wave radiated from the patch antenna 631 are the same direction, and the radiated terahertz wave does not interfere with the collimating lens 5 for collecting the optical beat signal to the single traveling carrier photodiode 66. It is possible to freely adjust the emission direction of the radiation terahertz wave.

  Further, since the patch antennas 631 to 639 are arranged in an array, it is possible to earn power obtained by power synthesis by arraying.

  The optical delay circuit 3 can be realized by a spatial optical delay circuit in which a lens and a movable reflecting prism are combined, or by using a fiber integrated optical phase modulator.

  In the present embodiment, the frequency of the radiated electromagnetic wave is not limited to 300 GHz, and an electromagnetic wave having any frequency in the range from the millimeter wave band to the terahertz band may be used. Further, the arrangement of antennas forming the patch antenna array 63 is not limited to 3 rows and 3 columns, and may be any number of rows and columns. Also, the shape of the antenna is not limited to the patch antenna, but may be other shapes such as a dipole or log peri.

It is a block diagram which shows the electromagnetic wave radiation apparatus of embodiment of this invention. It is a block diagram which shows the terahertz wave radiation source of the electromagnetic wave radiation apparatus shown in FIG. It is a figure which shows the electric power feeding element in the lower layer of a patch antenna. It is a circuit diagram of a feed element. It is a block diagram which shows the conventional electromagnetic wave radiation apparatus. It is a figure which shows the back surface of the silicon layer of the electromagnetic wave emission apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical beat signal generation part 2 Optical branch part 3 Optical delay circuit 4 Two-dimensional optical fiber array 5 Collimating lens 6 Terahertz radiation source 7 Radiation source mounter 8 Power supply 9 Control part 31-39 Phase shifter 61 InP board 62 Low dielectric Layer 63 Patch antenna array 631-639 Patch antenna 64 Electrode pad 65 Ground electrode 66 Single traveling carrier photodiode 67 Transmission line 68 Via hole

Claims (4)

In an electromagnetic wave emission device that radiates electromagnetic waves of at least one wavelength among electromagnetic waves in a wavelength band ranging from the millimeter wave band to the terahertz wave band,
An optical beat signal generating means for generating an optical beat signal;
Optical branching means for branching the optical beat signal into n channels;
An optical delay means for independently adjusting and outputting delay amounts of the optical beat signals of the n channels branched by the optical branch means;
An electromagnetic wave radiation source in which n elements arranged in an array form receive electromagnetic wave radiation elements that receive the optical beat signal from the optical delay means, and radiate electromagnetic waves;
The phase of the electromagnetic wave emitted by the electromagnetic wave radiation element is controlled by controlling the delay amount of the optical beat signal of the n channel output from the optical delay means, and thereby the direction of the electromagnetic wave emitted by the electromagnetic wave radiation source An electromagnetic wave radiation device comprising: control means for controlling The electromagnetic radiation element is:
Photoelectric conversion means for receiving the optical beat signal and generating a high-frequency current;
The electromagnetic wave radiation device according to claim 1, further comprising: a planar antenna that secondarily radiates electromagnetic waves according to the high-frequency current generated by the photoelectric conversion means into the air.   The electromagnetic wave radiation device according to claim 2, wherein the planar antenna radiates an electromagnetic wave in the same direction as a traveling direction of the optical beat signal irradiated to the photoelectric conversion means. In an electromagnetic wave emission device that radiates electromagnetic waves of at least one wavelength among electromagnetic waves in a wavelength band ranging from the millimeter wave band to the terahertz wave band,
An electromagnetic radiation source in which electromagnetic radiation elements that emit electromagnetic waves are arranged in an array; and
An electromagnetic wave radiation device comprising: control means for controlling the direction of the electromagnetic wave emitted by the electromagnetic wave radiation source by controlling the phase of the electromagnetic wave emitted by the plurality of electromagnetic wave radiation elements.

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