JP5229876B2 - Terahertz band electromagnetic wave oscillator using higher harmonics - Google Patents

Description

The present invention relates to a coherent terahertz (10 ¹² Hz) band electromagnetic wave oscillator using a high-temperature superconductor, and more particularly to a terahertz band electromagnetic wave oscillation apparatus using higher harmonics of a fundamental wave.

  Terahertz electromagnetic waves (for example, 0.1 to several tens of THz, hereinafter referred to as “THZ band” where appropriate) have extremely high transparency compared to currently used electromagnetic waves in the gigahertz band, so that objects can be viewed in detail. In the near future, it will be widely used in physicochemical spectrometers, identification of various molecules, macromolecules, proteins, etc., sophisticated imaging fields, medical and diagnostic equipment, aerospace or defense fields, high-speed communications, etc. It is a promising frequency band with a wide range of applications to be used. This wide range of applicability comes from two unique properties of terahertz electromagnetic waves. That is, the spectrum specificity of terahertz electromagnetic waves for vibration and rotation modes of a wide variety of important chemical or biological substances, and the permeability of terahertz electromagnetic waves that pass through packaging materials, clothing, plastics, and the like.

For this reason, conventionally, as a THz band electromagnetic wave oscillator, a high-power femtosecond (1/10 ¹⁵ ) level laser beam is irradiated onto a semiconductor, and a pulse-like wideband THz is generated by a current induced by the strong electric field. In addition to an optical switch method for generating a band wave and a parametric method for irradiating a nonlinear optical crystal with a high-power laser beam, various methods such as a free electron laser, synchrotron radiation, and photomixing have been known.

In addition, as examples of other known techniques for electromagnetic wave oscillators in the THz region, BSCCO (bismuth / strontium / calcium / copper oxide: Bi ₂ Sr ₂ CaCu ₂ O ₈ , Bi ₂ Sr ₂ Ca ₂ Cu ₃ O ₁₀ ), Laminate in which intrinsic Josephson junctions of a superconducting layer made of a superconducting single crystal such as TBCCO (thallium, barium, calcium, copper oxide: TL ₂ Ba ₂ Ca ₂ Cu ₃ O ₁₀ ) and an insulating layer are laminated in series. A THz band oscillator using a superconducting single crystal element having a Josephson junction has been proposed (see, for example, Patent Document 1 or Patent Document 2).
Japanese Patent Laid-Open No. 2006-210585 JP 2005-251863 A

However, all of these conventional THz-band oscillators require a large-scale incidental device despite their low oscillation efficiency (ratio of THz-band electromagnetic wave output to input energy) (several percent or less). It was not practical.
That is, as described in Patent Document 1 or Patent Document 2, any of the conventional THz band electromagnetic wave oscillation device proposals using Josephson junctions applies a strong magnetic field to a narrow element width of a superconducting element. Therefore, it is necessary to install a large external magnetic field application device as an accessory device, and it is difficult to oscillate and use an electromagnetic wave in a high intensity THz band that is not portable.

  On the other hand, using conventional laser mixing, parametric resonance technology, quantum cascade laser, etc., it is possible to generate monochromatic THz waves. However, these prior art techniques are inferior in efficiency, device compactness and cost performance, especially in the frequency range of 1 to 5 THz. In particular, in order to overcome the so-called “THz gap” problem in this frequency band, it is highly desirable to develop a completely new THz source with sufficient power based on new physical and technical principles. It is.

  The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a multi-layered layer that originally exists using a highly layered anisotropic BSCCO single crystal that is a high-temperature superconductor. It is another object of the present invention to provide a practical THz-band electromagnetic wave oscillation device that generates a monochromatic, coherent, strong and continuous electromagnetic wave particularly in the 1 to 5 THz frequency band by using the intrinsic Josephson junction.

Therefore, the present invention is formed by a single crystal of superconducting BSCCO structure having multiple stacked intrinsic Josephson junctions, a plurality of Josephson junctions in the single crystal by using the AC Josephson effect The present invention provides a terahertz band electromagnetic wave oscillating device using a higher order harmonic of a fundamental wave of a terahertz band electromagnetic wave that oscillates by oscillating synchronously .

Here, the frequency of the fundamental wave is 0.648 THz, and the higher order harmonic is a fourth order harmonic, which is 2.589 THz. In this case, the single crystal having the BSCCO structure has a size of 400 × 60 × 1.0 μm ³ .

  By the way, the single crystal body of the superconductor BSCCO structure is characterized by being excited by electromagnetic cavity resonance that does not require external magnetic field application.

  Here, the electromagnetic cavity resonance is a Fabry-Perot cavity resonance and can be modulated by changing the oscillation frequency according to the cavity size in the single crystal body of the BSCCO structure.

  As described above, the terahertz band electromagnetic wave oscillation device according to the present invention is formed of a single crystal of a superconductor BSCCO structure having a multi-layered intrinsic Josephson junction, and a higher order of the fundamental wave radiated from the single crystal. Since harmonics are utilized, it is possible to provide a practical THz band electromagnetic wave oscillation device that generates a monochromatic, coherent, strong and continuous electromagnetic wave, particularly in the 1 to 5 THz frequency band, so-called “THZ gap”. It was.

  Hereinafter, the terahertz band electromagnetic wave oscillation device having directivity according to the present invention will be described in detail. First, a single crystal body having a superconductor BSCCO structure excited by electromagnetic cavity resonance will be described in detail.

  The superconducting Josephson junction has the basic property of forming a high-frequency electromagnetic field having a frequency proportional to the voltage, but this property enables the production of a coherent and modulatable high-frequency oscillator. This attractive possibility has been extensively explored in the past by manufacturing large arrays of artificial Josephson junctions.

A major problem is that all the junctions in the array are synchronized and oscillated in phase, but this can be achieved, for example, by coupling them to the same electronic resonant circuit. Due to the intrinsic Josephson effect in BSCCO (Bismuth / Strontium / Calcium / Copper Oxide: Bi ₂ Sr ₂ CaCu ₂ O ₈ , Bi ₂ Sr ₂ Ca ₂ Cu ₃ O ₁₀ ), in the form of a laminate, ie single crystal It is possible to easily produce a one-dimensional array consisting of a very large number of closely packed identical joints in the form of so-called mesas formed as:

  If all the junctions in the above laminate are forced to vibrate at the same frequency and in phase, there will be a strong coherent electromagnetic emission line whose total power is measured by the square of the number of junctions. It is thought that it is obtained. This synchronization is further facilitated by coupling the junction to an external microwave cavity, or the mesa's own resonant mode. Electromagnetic waves inside large area mesas propagate as Josephson plasma mode.

  The in-plane velocity of this mode is highly dependent on the out-of-plane wave vector, the maximum velocity matches the in-phase mode (all joints vibrate in phase), and the minimum speed vibrates in the adjacent joints out of phase. Matches the reverse phase mode. Furthermore, in all of the above modes, the multiple reflections at the mesa side result in standing wave patterns and Fabry-Perot cavity resonances known as Fiske modes.

  In all but the common mode, on the same surface, the average electric field cancels each other, so that only the common mode generates detectable external electromagnetic waves. A Josephson vortex moving grid is often used to excite the Fiske resonance. However, a triangular vortex lattice structure is advantageous for inductive interaction between vortices, but in this structure, a non-electromagnetic wave-generating reverse phase mode is exclusively excited. A proposal was made that the side effect in a sufficiently narrow mesa, that is, the dynamic action at high drive, would enable stabilization of a vortex lattice with square symmetry that can excite the common mode. No proof of this proposal has been reported yet.

In the present invention, a means is disclosed that makes it possible to efficiently convert an alternating electromagnetic field localized at the Josephson junction into a coherent, deflectable high frequency electromagnetic wave. Our approach is based on the coupling of waves at the junction to the Fabry-Perot cavity mode. This has two effects. That is,
(A) A large number of Josephson junctions will operate synchronously in common mode, which is not primary as observed in uncorrelated junctions, but secondary with the number of junctions Increases available electromagnetic energy.
(B) At resonance, energy is efficiently absorbed into the synchronous mode, enhancing its strength by a factor equal to the quality factor of the cavity. The quality factor of this cavity can be increased and is ultimately limited only by the loss in the cavity.

  Analysis of the basic symmetry of a device with a junction as described above shows that a uniform current flowing perpendicular to the junction cannot excite the resonant cavity mode. Therefore, the prior art related to using a Josephson junction as an electromagnetic wave generation source exclusively considers operation in a magnetic field applied parallel to the junction. Next, so-called Josephson vortices enter between the superconducting layers, breaking the symmetry and exciting a resonance known as Fiske resonance.

In the present invention, by forming a non-uniform coupling between the current and the electromagnetic wave mode, the pairing is broken and the resonance cavity mode can be excited in a zero applied magnetic field. This can be realized by, for example, the following method, but is not limited thereto.
(A) The BSCCO composition gradient induces a non-uniform critical current density across the width of the mesa. The superconductivity (TC, J _C, ) of BSCCO is highly dependent on its oxygen content. Thus, by using controlled quenching in an oxygen atmosphere, a critical current density is established near one side that is higher than near the opposite side.
(B) For example, an asymmetric cross section of a mesa with a trapezoid rather than a rectangle induces an asymmetric current and an asymmetric reflection coefficient at multiple sides.
(C) An asymmetric critical current distribution can also be established by irradiating one side of the mesa with an electron or proton beam, or intentionally suppressing superconductivity by implanting ions. It is.

  The electromagnetic generation and transfer properties of an ideal mesa composed of the same layer with exactly the same critical current modulation can be evaluated for various modulation profiles.

Such critical current modulation couples uniform vibration with the fundamental mode inside the mesa, and its coupling strength is proportional to the product rD. The length L of the mesa must be greater than or at least approximately equal to the wavelength of the emitted electromagnetic wave. In a mesa whose height H is higher than 1 to 1.5 μm, which depends on the mesa width W and the quasiparticle conductivity, the electromagnetic wave generation loss exceeds the ohmic loss. The lower mesas than the typical height, wave power generated at the resonance increases in proportion to H ^2. In a tall mesa, the maximum total electromagnetic wave generation power can be estimated as P _max ≈πJ _J ² (rD) ² L / ω [CGS unit] without depending on the height.

  Currently, continuous mesochromatic THz radiation up to 0.85 THz with high intensity is extracted from the mesa-type intrinsic Josephson junction in the superconductor BSCCO structure having the multi-layered intrinsic Josephson junction as described above. It is known to get.

Here, the inventor of the present application has developed a THz-band electromagnetic wave oscillation device that uses an intrinsic Josephson junction BSCCO (Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ} ) and increases the magnitude of power by an order of magnitude compared to the conventional one. It is. The estimated total power emitted from the development sample is 5 μW at 0.648 THz, but in addition to this, the electromagnetic wave oscillation of harmonics up to the fourth order (hereinafter referred to as “emission” as appropriate) has a maximum frequency of 2.589 THz. Was observed. Since the unique temperature dependence of the luminescence power was found to be greatest between 20 and 40 K, the non-equilibrium effect due to heating is related to the formation of coherent states responsible for THz radiation in this system. It has been shown that it can play an important role.

In high-temperature superconductors, particularly in the THz frequency region using multi-layered intrinsic Josephson junctions inherently present in highly layered anisotropic Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ} single crystals A promising method for generating monochromatic and continuous EM waves is shown. And the prototype sample by this inventor obtained light emission as high as 5 microwatts in total power. This is much higher than previously known and satisfies some commercial application requirements. The line width is very sharp and it is limited by the resolution of FT-IR (Fourier Transform Infrared), which is 0.25 cm ⁻¹ = 7.5 GHz.

  Experimental results by the present inventor have revealed that such monochromatic radiation having a frequency ν follows the following simple relationship.

    ν = c / nλ = c / 2 nw = 2 eV / hN (1)

  In the above formula (1), c is the speed of light in vacuum, n is the refractive index of the superconductor, λ is the wavelength of the EM wave generated in the mesa, w is the width of the sample, V is the intrinsic Josephson junction The voltage that appears, N is the number of intrinsic Josephson junctions, and e and h are the charge and Planck constant, respectively.

By the way, for higher harmonics, the frequency is given by ν _m = mν, and in equation (1), m is an integer and is a harmonic index. These simple relationships are firstly that the superconductor itself can act like a resonant cavity with a constant resonant mode, and secondly, the radiation is generated by the ac-Josephson effect. It has been shown to be done. The intensity of these higher harmonics decreases rapidly as the index m increases, but they are still as sharp as the baseline even at the fourth harmonic. The frequency observed in the 4th harmonic exceeds 2.5 THz.

FIG. 1 shows an example of a terahertz band electromagnetic wave oscillation device according to the present invention. Then, FIG. 1 (a) shows a schematic diagram of a mesa structure that is created on the cleaved surface of the _{"Bi 2 Sr 2 CaCu 2 O 8} + δ ". In FIG. 1A, the width w varies at 100, 80, 60 and 40 μm, while the length is constant at 300 μm (A type), but one prototype sample is long at w = 60 μm. Is 400 μm (T-type). The mesa height is 1 μm. The basic Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ} crystal has a size of 1 to 2 mm × 1 mm and a thickness of 10 μm. The top layer of the mesa was then covered with gold deposited as an electrode with a thickness of about 100 nm, while the other two electrodes were taken from the bottom of the mesa.

  FIG. 1 (b) shows a three-dimensional differential topographic AFM photograph of mesa. In FIG. 1 (b), the tail structure at the base of the mesa forming the trapezoid shape can be clearly seen.

  FIG. 2 shows an example of an IV curve obtained from a mesa (T type) having a width of 60 μm. Here, FIG. 2 (A) shows the overall IV curve obtained by scanning I in the direction of the arrow at 0.1 mHz. In the return branch, a dent is clearly seen (circled) at a voltage of about 0.9 V and a current of about 20 mA.

  FIG. 2 (B) is an enlarged view around the dent shown in FIG. 2 (A), where strong light emission is observed. The maximum power of 5 μW was obtained at V = 0.8850 V and I = 19.83 mA.

The inventor of the present application presents the above-mentioned remarkable experimental results occurring in the intrinsic Josephson junction system Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ} , and analyzes the spectrum of higher harmonics to obtain a certain knowledge of the above phenomenon. In particular, the knowledge about the mechanism of the emission of such strong, continuous and monochromatic electromagnetic waves at THz frequencies will be described.

Traditionally, many researchers have explored EM wave generation at THz frequencies using intrinsic Josephson junctions, but most of these theoretical and experimental studies have been conducted in a magnetic field. It was. As one of the research results, the observation of the Fiske step corresponding to the excitation of the stationary EM wave in the sample has been reported. In addition, more direct measurements of emission using a separate detector have recently been reported, and intrinsic Josephson junctions using resonant Shapiro steps that occur in the Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ} single crystal itself. An example in which a laminate of the above is used as a detector is known.

  However, in the zero magnetic field, only some reports have been made, and one example is a direct observation example of radiation at about 0.5 THz. The estimated power in this case is several orders of magnitude smaller than the magnitude obtained in the present invention. In general, the power observed in all previous measurements is so small that special and sophisticated techniques such as superheterodyne methods are required for detection, which significantly hinders the development of applications. It was.

The sample used in the experiments of the present invention is a mesa produced by argon ion etching and photolithographic techniques from cleaved single crystal Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ} fragments grown by the moving float region method.

Here, the superconducting transition temperature is between 75 and 85K, indicating that the prototype samples are slightly underdoped, probably due to the fabrication process under high vacuum, but before the mesa fabrication This is because the initial _Tc had 90K. Therefore, the critical Josephson current is low, 100 A / cm ² or less.

This means that the Josephson plasma frequency ω _p is also low and can be estimated as ν _p = ω _p / 2π ≦ 70 GHz. This is because ω _p = c / √ελ _c , where c = 2.99979 × 10 ¹⁰ cm / sec, ε is 17.54, and λ _c ≈170 μm. Note that this Josephson plasma frequency is significantly lower than the emission frequency currently observed.

  The lateral dimensions of the mesas prepared and studied so far are 300 μm in length and w = 100, 80, 60 and 40 μm (A type) due to the rectangular shape and 400 μm in length and w in width = 60 μm (T-type) and the height of all mesas is ˜1.0 μm.

FIG. 1A shows a schematic view of the mesa. The accuracy of the height depends on the calibration of the etching rate during the argon ion etching process and is within 3%.
In our mesa, as shown in FIG. 1 (b), a considerable tail effect was found at the base by topographical considerations by AFM (Atomic Force Microscope, KEYENCE, Japan). This trapezoidal shape of the mesa cross section depends on the argon ion etching process.

  FIG. 2A shows a typical example of a current-voltage (IV) curve of a mesa (T type) having a size of 60 μm according to the present invention. The curve shows a large hysteresis and has a strong dent profile at the voltage on the return branch as indicated by the circle. This region is shown on an enlarged scale in FIG. 2B, where we have observed intense radiation with a magnitude about an order of magnitude stronger than the known magnitudes discussed in detail below. .

  In FIG. 2B, the detected radiation power is also displayed on an arbitrary scale. Looking closely at the IV curve, it is clear that the current and voltage fluctuate when the current and voltage are in the vicinity of the light emitting point. However, once it starts emitting light, the current and voltage are constant and stable over time.

At regions of high current and voltage I _c of the mesa, I-V curve shows a strong negative differential resistance. The estimated temperature of the mesa exceeds even T _c . This is considered because the heating effect by direct current is severe and the thermal conductivity of the superconducting sample at the bottom of the mesa is insufficient.

  FIG. 3 shows a power spectrum of light emitted from a 60 μm mesa (T type) at 40 K of the terahertz band electromagnetic wave oscillation device according to the present invention. As shown in FIG. 3, harmonics up to the fourth order are observed. Note in FIG. 3 that the ordinate is plotted on a logarithmic scale. The inset is for three different samples: one sample with w = 60 μm (filled with ◆) and two samples with w = 100 μm (●) and 60 μm (▼) used for This shows the temperature dependence of the emission power observed. The intensity is normalized by the maximum value.

Radiation is generated only at the return branch when the light emission condition of Formula (1) is satisfied at a constant voltage as shown in FIG. When radiation was detected with reasonable power by another detector placed 180 ° opposite the spectrometer, the FT-IR spectrometer was activated to acquire the spectrum. Here, FT-IR spectrometer (JASCO FARIS-I) is designed only for THz frequency range, is possible to measure the 2～650Cm ^-1 by resolution of 0.25 cm ^-1.

  FIG. 3 shows a typical example of data including higher order harmonics, where radiation is continuously received during a 10-20 minute FT-IR measurement. Here, in order to test the stability of oscillation, measurement was continuously performed over 2 hours. However, no significant changes in power and frequency were observed during this operation test.

In the radiation power spectrum of the 60 μm mesa provided in FIG. 3, the higher harmonics up to the fourth order are clearly shown. One of the intense fundamental emission lines with a frequency of 0.6482 GHz, while the observed maximum frequency reaches the fourth harmonic of 2.589 THz. In addition to these harmonics, a weak variant suggestion of the presence of further higher harmonics up to m = 15 can be seen. The accuracy of the frequency is better than 0.01 cm ⁻¹ and the line width is limited by the experimental resolution limit (≦ 0.25 cm ⁻¹ = 7.50 GHz) of our FT-IR instrument. The observed frequencies and intensities are summarized in Table 1.

Table 1 shows the characteristics of the fundamental emission line and higher harmonics obtained from a 60 μm mesa, k is the wave number of the emission, ν is the corresponding frequency, Δν is the corresponding line width, and I _m / I ₁ is the line intensity normalized by the basic line.

  In the inset of FIG. 3, the temperature dependence of the emission intensity for three samples (two from A type and one from T type) is compared. All of the samples measured so far have a similar tendency to have a maximum emission between 20 and 45K. It should be noted that the maximum emission temperature depends on the sample and is sensitive to experimental conditions such as cooling conditions. This strongly represents an important role of the nonequilibrium effect involved in the mechanism of this radiation phenomenon.

  As can be seen in the IV curve shown in FIG. 2, the radiation occurs continuously at a voltage within a certain range, which may be greater than 10% of V. Within this voltage range, the radiation frequency was measured and the spectrum was analyzed. It has been found that it varies linearly with voltage V, but the intensity varies considerably depending on V. Further, the frequency is proportional to the voltage V and follows the ac Josephson relation with a coefficient of 2e / h = 483.594 GHz / mV as shown in FIG. This observation ensures that the AC Josephson effect acts as a driving mechanism for the emission of THz EM waves.

Due to the nonlinearity of the Josephson current, the higher order harmonics shown in FIG. 3 and Table 1 are expected to appear and the experimental results can be explained as follows. The ac Josephson current induces an oscillation voltage with a Josephson frequency ω _J between the superconducting CuO ₂ layers. Phase difference of each layer is given by _{θ (t) = ω J t} + υsinω J t, where, upsilon is the ratio of the ac Josephson voltage for static voltage V. Therefore, the Josephson current J is expressed as follows.

J = J _c sin (ω _J t + υsin ω _J t)
= J _c [{J ₀ (υ) −J ₂ (υ)} sinω _J t + {J ₁ (υ) + J ₃ (υ)} ×
sin2ω _J t + {J ₂ (υ) −J ₄ (υ)} sin 3ω _J t + {J ₃ (υ) + J ₅ (υ)} sin 4ω _J t] +..., (2)

In equation (2), J _n (υ) is an nth order Bessel function. Since the total light emission power is proportional to the spatial average of J, the intensity of higher order harmonics strongly depends on the spatial variation of υ. Therefore, a detailed analysis of higher harmonics provides definitive information for understanding the mechanism of THz emission in this system.

Next, the total power P emitted from the sample mesa was estimated. The EM wave propagates with a 50% efficiency through a chopper whose bolometer window has a diameter of 1.27 cm and reaches the Si detector. Therefore, the power P _obs received by the detector can be expressed as P = e _eff P _obs by the efficiency constant e _eff .

This value can be estimated from the geometry of the device as e _eff = 5.7 × 10 ³ . Since the observed power is V _out is the output voltage from the detector and can be expressed as P _obs = V _out / S as S = 2.19 × 10 ⁵ V / W, the calibration constant of the Si bolometer is This is about 0.2 mV, which leads to a value of P≈5 μW.

This results in an efficiency of ˜3 × 10 ⁻⁴ since the total power delivered to the mesa is approximately 15 mW. However, in order to make it more strict, the angular distribution of the light emission power must be taken into account.

In conclusion, in the present invention, a novel technique of generating intense, continuous and monochromatic electromagnetic waves at the THz frequency by the intrinsic Josephson junction mesa of monocrystalline Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ} can be shown. It was. Here, the total power of light emission was successfully increased to 5 μW, which is approximately an order of magnitude larger than that of the prior art. Then, higher-order harmonics having a fundamental frequency of 0.6482 THz were observed up to the fourth order exceeding 2.5 THz.

  The emission frequency is determined by a simple relationship described by equation (1), and the observed higher order harmonics can be described by equation (2) where υ is an even function. Here, it is pointed out that the heating effect is decisive and can play an important role for the generation mechanism. This problem can be solved by finding an optimum condition that ultimately overcomes the so-called “THZ technology gap” in the 1-5 THz band.

  FIG. 4 shows the frequency as a function of the voltage applied to the mesa. The line shows the ac Josephson relationship at two different temperatures.

  As described above in detail, the terahertz band electromagnetic wave oscillation device according to the present invention is formed of a single crystal having a superconductor BSCCO structure having a multi-layered intrinsic Josephson junction, and the terahertz band in which the single crystal is oscillated. It is characterized by using higher harmonics of the fundamental wave of electromagnetic waves. This makes it possible to provide a practical THz band electromagnetic wave oscillation device that generates a monochromatic, coherent, strong and continuous electromagnetic wave, particularly in the 1 to 5 THz frequency band, so-called “THZ gap”.

  The present invention relates to terahertz electromagnetic waves, particularly 1 to 5 THz electromagnetic wave oscillators, physicochemical spectrometers, identification of various molecules, polymers, proteins, etc., elaborate imaging fields, medicine and diagnostics. It has industrial applicability in a wide range of application fields widely used in equipment, aerospace or defense fields, high-speed communications, and the like.

1 illustrates an example of a terahertz band electromagnetic wave oscillation device according to the present invention. Here, (a) shows a schematic diagram of a mesa structure created on a cleavage plane of “Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ} ”, and (b) shows a three-dimensional differential topographic AFM photograph of the mesa. The example of the IV curve obtained from the 60-micrometer width mesa (T type) in the terahertz band electromagnetic wave oscillation apparatus which concerns on this invention is shown. The power spectrum of the light emission from the 60-micrometer mesa (T type) in 40K of the terahertz band electromagnetic wave oscillation apparatus which concerns on this invention is shown. 3 shows the frequency as a function of the voltage applied to the mesa in the terahertz band electromagnetic wave oscillator according to the present invention.

Claims (7)

Is formed by a single crystal of superconducting BSCCO structure having multiple stacked intrinsic Josephson junctions, by a plurality of Josephson junctions in the single crystal by using the AC Josephson effect vibrates synchronously A terahertz band electromagnetic wave oscillating device using a higher order harmonic of a fundamental wave of an oscillating terahertz band electromagnetic wave.   2. The terahertz band electromagnetic wave oscillation device according to claim 1, wherein the higher-order harmonic is a fourth-order harmonic of the fundamental wave. 2. The terahertz electromagnetic wave oscillation device according to claim 1, wherein the BSCCO single crystal has a width of 40 to 100 μm. The single crystal of the BSCCO structure has a size of 400 × 60 × 1.0 μm ³ , the frequency of the fundamental wave is 0.648 THz, the higher order harmonic is the fourth order harmonic of the fundamental wave, and the fourth order harmonic The terahertz band electromagnetic wave oscillation device according to claim 1 , wherein the wave is 2.589 THz.   5. The terahertz band electromagnetic wave oscillation device according to claim 1, wherein the single crystal body of the superconductor BSCCO structure is excited by electromagnetic cavity resonance that does not require application of an external magnetic field. .   6. The terahertz band electromagnetic wave oscillation device according to claim 5, wherein the electromagnetic cavity resonance is a Fabry-Perot cavity resonance.   The terahertz band electromagnetic wave oscillation device according to claim 6, wherein the terahertz band electromagnetic wave oscillation device can be modulated by changing an oscillation frequency according to a cavity size in the single crystal body having the BSCCO structure.