JP6116053B2 - Spin wave induction and initial phase control system and method, spin wave induction and propagation control system and method - Google Patents

Description

  The present invention relates to a spin wave induction / initial phase control system and method suitable for light pulse irradiation, and a spin wave induction / propagation control system and method.

  In the field of electronics that supports the modern information society, the degree of freedom of charge of electrons and the current that is the flow of those charges have been responsible for information. However, due to the influence of Joule heat that is generated when electricity is supplied, the increase in the density of information devices is reaching its limit.

  Under these circumstances, in recent years, the field of spintronics that actively uses electron spin (hereinafter referred to as “spin”), which is another degree of freedom of electrons, has been launched, and research is being conducted worldwide as a technology that supports the next-generation information society. Development is progressing.

  In the field of electronics, the charge of an electron was directly used as information, but in this field of spintronics, the direction of the spin of an electron becomes one piece of information. Transmission of information with a spin of “0” is assumed.

  As shown in FIG. 21, a phenomenon in which the rotation axis of one spin swings in a circle is called precession. When this spin begins to precess, for example, spins other than the A point around one spin at the A point start precessing at the same frequency due to the interaction between the spins. Here, when spins adjacent to each other perform a precession while having a phase shift between them, a wave having a finite length is generated, and this wave is called a spin wave. Unlike spin current, this spin wave does not generate Joule heat, and is expected to be applied to new information devices. In the case shown in FIG. 21, the length from point A to point B is called the wavelength of the spin wave.

  As a technique related to a conventional spin wave, it has been proposed to induce a spin wave using the inverse Faraday effect by concentrating a circularly polarized pulse having a pulse width of about 100 femtoseconds on a magnetic material (for example, Non-Patent Document 1).

  The technique disclosed in Non-Patent Document 1 enables time-space-resolved measurement of spin precession by gradually shifting the relative position of the probe beam to the pump beam irradiated on the sample in the same direction as the magnetic field. It is said. The pump beam is light that excites the substance, and the probe beam is light for reading information without exciting the substance. According to the observation result of the spatial propagation of the spin wave by the pump-probe method, the spin precession occurs by shifting the distance between the spot of the pump beam and the spot of the probe beam in order of 100 μm, 200 μm, and 300 μm. It can be seen that the timing gradually shifts and the wave packet of the spin wave propagates.

  Similarly, as a result of the spatial propagation experiment of the spin wave by the pump-probe method, it was clearly shown that the spin wave propagates anisotropically by changing the spot shape of the pump beam on the medium surface. This result is also reproduced by numerical calculation using the spin wave dispersion relation (see, for example, Non-Patent Document 2).

  Furthermore, a spin wave induction / propagation control system and a wave induction / propagation control method for inducing a spin wave by irradiating a medium with a pump beam and controlling a function of the spin wave by changing a spot shape of the pump beam Has been proposed (see, for example, Patent Document 1).

Japanese Patent Application No. 2012-203893 U.S. Pat. No. 4,912,478

Teruki Yuki et al., Photo-Induced Spin Dynamics in Rare Earth Iron Garnet, The 66th Annual Meeting of the Physical Society of Japan, Vol. 66, No. 4, 751, March 3, 2011 Terui Yuki et al., Wavenumber distribution control of spin wave by shaping circularly polarized pulse, 59th Joint Lecture on Applied Physics, Proceedings, 10-076, February 29, 2012

  In the disclosed technology of Non-Patent Document 1, it is shown that the induced spin wave propagates to the surroundings. In addition, the disclosure techniques of Non-Patent Document 2 and Patent Document 1 show that spin waves propagate anisotropically by changing the spot shape of the pump beam. In the disclosed technologies of Non-Patent Document 2 and Patent Document 1, the function of the spin wave can be controlled by changing the spot shape of the pump beam, but in either case, the pump light polarization is counterclockwise or clockwise circular polarization. Therefore, there are only two initial phases of spin precession, 0 or π, depending on the helicity, and there is a problem that the initial phase cannot be controlled continuously.

  Further, in the disclosed technique of Patent Document 1, the propagation direction of the spin wave can be controlled by changing the spatial distribution of the spot of the pump beam, but when there is a limit to the space to which the spot of the pump beam is applied, There was a problem that the spatial distribution of the spot of the pump beam could not be changed.

  In addition, there is no disclosed technique regarding the propagation state of spin waves and the propagation control of spin waves when a medium is irradiated with pump light of linearly polarized light instead of circularly polarized light.

  Furthermore, it is generally well known to change the propagation direction of radio waves and sound waves by controlling the phase of radio waves and sound waves with a phased array radar or the like. In addition, a spin wave is conventionally induced by a microstrip antenna, a synthesized spin wave is induced by interfering with a plurality of spin waves, and the propagation direction of the synthesized spin wave is changed by changing the initial phase of each spin wave. Control is proposed (for example, refer patent document 2). However, the disclosed technique of Patent Document 2 is a method of inducing spin waves using a microstrip antenna, and there is a problem in that spin waves cannot be induced in an ultrafast and non-contact manner. In addition, since the disclosed technique of Patent Document 2 requires microfabrication of a medium in which spin waves are induced, there is a problem that spin wave propagation is difficult to control and spin wave propagation is difficult to control. It was.

  Therefore, the present invention has been devised in view of the above-described problems, and its object is to induce spin waves that control the initial phase of the spin waves that are induced by irradiating the medium with pump rays. To provide an initial phase control system and method. Furthermore, it is possible to control the propagation direction of the synthesized spin wave by inducing a synthesized spin wave that is synthesized by interfering with the multiple spin waves induced in the spot of the pump beam formed by irradiating the medium with multiple pump beams. A spin wave induction and propagation control system and method are provided.

  In order to solve the above problems, a spin wave induction / initial phase control system and method, and a spin wave induction / propagation control system and method according to the present invention are configured as follows.

  The first invention of the present application is a spin wave induction / initial phase control system, comprising a light source, a polarization azimuth rotating means capable of rotating a polarization azimuth angle of a pump beam emitted from the light source, and a pump beam having a polarization direction A medium disposed on an optical path passing through the angular rotation means and capable of inducing a spin wave, and by irradiating the pump beam toward the medium, the spin wave is induced in the medium. Based on the equation (1), the initial phase of the induced spin wave is controlled by changing the polarization azimuth angle of the pump beam by the polarization azimuth rotation means.

  The second invention of the present application is characterized in that, in the first invention, the pump beam emitted from the light source is linearly polarized light.

  A third invention of the present application is a spin wave induction / propagation control system in which N pump beams are irradiated toward a medium, and N spin waves induced in the medium propagate to each other. The synthesized spin wave is induced by the interference, and the polarization azimuth of the N pump beams is changed by the polarization azimuth rotation means in the spin wave induction / initial phase control system according to claim 1, so that the N spins By changing the initial phase of each wave, the function of the synthesized spin wave is controlled based on the following equation (2).

  The fourth invention of the present application is characterized in that, in the third invention, the pump beam emitted from the light source is linearly polarized light.

  The fifth invention of the present application is a spin wave induction / initial phase control method, in which a pump beam emitted from a light source is irradiated onto a medium via a polarization azimuth rotating means for rotating a polarization azimuth angle of the pump beam. The initial phase of the spin wave is controlled by changing the polarization azimuth of the pump beam by the polarization azimuth rotation means based on the first step of inducing the spin wave in the medium and the following equation (1). And a second step.

  The sixth invention of the present application is characterized in that, in the fifth invention, the pump beam emitted from the light source is linearly polarized light.

  A seventh invention of the present application is a spin wave induction / propagation control method, wherein N pump beams emitted from a light source are transmitted to a medium via a polarization azimuth rotation means for rotating the polarization azimuth angle of the pump beam. The first step of irradiating and inducing N spin waves in the medium to cause interference to induce a synthesized spin wave, and the polarization azimuth rotation in the spin wave induction and initial phase control method according to the fifth aspect of the present invention The function of the synthesized spin wave is controlled based on the following equation (2) by changing the polarization azimuth angle of the N pump beams by means and changing the initial phase of each of the N spin waves. And a second step.

  The eighth invention of the present application is characterized in that, in the seventh invention, the pump beam emitted from the light source is linearly polarized light.

  According to the first and fifth aspects of the present application, the initial phase of the spin wave can be controlled based on the model of the equation (1) by changing the polarization azimuth angle of the pump beam by the polarization azimuth rotation means.

  According to the third and seventh inventions of the present application, the synthesized spin waves are induced by the N spin waves induced from the spots of the N pump beams interfering with each other, as in the first invention of the present application. Then, the initial phases of the N spin waves are respectively changed, and the function of the synthesized spin wave is controlled based on the model of equation (2). As a result, a desired function of the synthesized spin wave can be obtained by controlling the initial phase of each of the N spin waves. Also, according to equation (2), the sample characteristics are based on the dispersion relation of the angular frequency of the spin wave and the relaxation coefficient of the spin wave, so the sample characteristics can be predicted in advance by numerical calculation, and the desired synthesized spin wave can be predicted. It is possible to select a sample for inducing or to synthesize a desired sample.

  According to the third and seventh aspects of the present invention, when the phased array technology for controlling the propagation direction of the spin wave by controlling the initial phase is applied to the propagation direction control of the synthesized spin wave, It is possible to change the initial phases of the N spin waves induced in the spots of the N pump beams without providing a delay time in the irradiation timing. Accordingly, it is not necessary to secure a propagation space for the pump beam for providing a delay time for the pump beam, and the device can be downsized.

  According to the second, fourth, sixth, and eighth inventions of the present application, since the polarization of the pump beam is linearly polarized, the polarization azimuth angle of the pump beam can be continuously changed. It is possible to continuously change the initial phase according to the change.

It is the schematic diagram which showed the structure of the induction | guidance | derivation and initial phase control apparatus of the spin wave by the pump probe method to which this invention is applied. FIG. 2 is a conceptual diagram of a spin wave induction / initial phase control system in which main components of the spin wave induction / initial phase control apparatus shown in FIG. 1 to which the present invention is applied are extracted. It is the conceptual diagram which showed the state of the initial stage magnetic field and initial stage spin in a sample at the time of giving an external magnetic field to a sample. It is the conceptual diagram which showed the state from which the direction of the synthetic magnetic field and the spin changed from the initial magnetic field and the initial spin, respectively, when the sample was irradiated with the pump beam emitted from the light source. It is the conceptual diagram which showed the state in which the spin precesses around a synthetic magnetic field, after irradiating a sample with a pump beam. It is the conceptual diagram which showed the state which the polarization azimuth of the pump beam changed with the polarization azimuth rotation means. It is the conceptual diagram which showed the state which has detected the mode that the spin wave induced by the spin of FIG. 5 performing precession propagates around. It is the figure which showed the temporal change of the spin precession induced by irradiating the sample with the pump beam and observed by the pump-probe method for each polarization azimuth angle of the pump beam. It is the figure which showed the numerical analysis result which extracted the case where the polarization azimuth angle of pump light was -60 degrees among the experimental graphs of FIG. 8, and fitted the graph. (A) is the figure which showed the experimental result showing the relationship between the polarization azimuth of a pump beam and the vibration amplitude of the polarization azimuth rotation angle of a probe beam, (b) is the polarization azimuth of a pump beam, It is the figure which showed the experimental result showing the relationship of the initial phase of the vibration amplitude of the polarization azimuth | direction rotation angle of a probe beam. Vector u ₁ when about a resultant magnetic field spins precess, vectors u _2, is a conceptual diagram showing the relationship of the vector u _3. (A) is a graph showing the results the experimental results and numerical analysis showing a relationship between polarization azimuth and u _1z of pump radiation, (b), the table the relationship between polarization azimuth and u _2z of pump radiation It is the figure which showed the experimental result and numerical analysis result which were performed. It is the schematic diagram which showed the structure of the induction | guidance | derivation and propagation control apparatus of the synthetic | combination spin wave by the spot of two pump rays using the pump probe method of 2nd Embodiment to which this invention is applied. FIG. 14 is a conceptual diagram of a spin wave induction / propagation control system in which main components of the spin wave induction / propagation control apparatus shown in FIG. 13 to which the present invention is applied are extracted. It is the conceptual diagram which showed the state which nine spin waves on a sample interfered using the pump probe method of 2nd Embodiment to which this invention is applied. (A) is the figure which showed the simulation result of the amplitude map after 3 ns of the spin wave induced from the spot of one pump beam, (b) shows the phase map of the spin wave in the case of (a). It is a figure. (A) is the figure which showed the simulation result of the amplitude map of the spin after 3 ns in case the initial phase of all the spin waves induced from the spot of nine pump light rays is the same phase, (b) is (a) FIG. 6 is a diagram showing a phase map of spin waves in the case of (). (A) is the figure which showed the simulation result of the amplitude map of the spin wave after 3 ns in case the phase difference of the initial phase of the spin wave induced from the spot of nine pump light rays is 60 degrees, (b) ) Is a diagram showing a phase map of spin waves in the case of (a). (A) shows 3 ns when the initial phase C _n of the spin wave induced from the spots of the nine pump beams is C _n = 15 ° × (n−4) ² (where n = 1 to 9). It is the figure which showed the simulation result of the amplitude map of a later spin wave, (b) is the figure which showed the phase map of the spin wave in the case of (a). (A) shows that the initial phase C _n of the spin wave induced from the spots of nine pump rays is C _n = 60 ° × (n−4) + 15 ° × (n−4) ² (where n = It is the figure which showed the simulation result of the amplitude map of the spin wave after 3 ns in the case of 1-9), (b) is the figure which showed the phase map of the spin wave in the case of (a). It is a conceptual diagram of a spin wave having a finite wave number.

First embodiment

  Hereinafter, as embodiments of the present invention, a spin wave induction / initial phase control device 1, a spin wave induction / initial phase control system 10, and a spin wave induction / initial phase control that control an initial phase of a spin wave propagating in a medium. The method will be described in detail with reference to FIGS.

  FIG. 1 is a schematic diagram showing a configuration of a spin wave induction / initial phase control apparatus 1 by a pump-probe method to which the present invention is applied. FIG. 2 is a conceptual diagram of a spin wave induction / initial phase control system 10 in which main components of the spin wave induction / initial phase control apparatus 1 shown in FIG. 1 to which the present invention is applied are extracted.

  The spin wave induction / initial phase control apparatus 1 shown in FIG. 1 applies an external magnetic field by an electromagnet 41 in the in-plane direction of the flat sample 2 to direct the initial spin in the sample 2 in the direction of the initial magnetic field. This is a device that makes a pump beam incident in the direction perpendicular to the surface of the sample 2 and performs time-space-resolved measurement of the spin wave generated by the spin by the pump-probe method. Here, the initial magnetic field is represented by a vector sum of an external magnetic field and an anisotropic magnetic field.

  The spin wave induction / initial phase control device 1 is arranged on a light source 3, a beam splitter 11 that separates the pump beam emitted from the light source 3, and an optical path of the pump beam that has passed through the beam splitter 11. An optical parametric amplifier 12 that converts the wavelength of the light beam, a chopper 13 that chops the pump light beam at a frequency that is half the repetition frequency of the pump light beam bent in a substantially right angle direction by the optical parametric amplifier 12, and a pump light beam that has passed through the chopper 13 , A beam detector 14 for detecting the intensity of one of the separated pump beams, a mirror 16 for reflecting the separated pump beam in a substantially perpendicular direction, and a beam reflected by the mirror 16. Polarizer 18 that makes the pump beam linearly polarized, and the polarization direction of the pump beam that has passed through It includes a polarization azimuth rotating device 4 to be rotatable, and a lens 5 for focusing the pump light beam having passed through the polarization azimuth rotating device 4.

  In addition, the spin wave induction / initial phase control device 1 is bent in a substantially right angle direction by a mirror 21 disposed on an optical path of a probe beam that is bent and separated in a substantially right angle direction by a beam splitter 11, and a mirror 21. The polarization beam splitter 22 that guides the probe beam to the delay stage side, the quarter-wave plate 23 that converts the probe beam from the polarization beam splitter 22 from linearly polarized light to circularly polarized light, and the quarter-wave plate 23. A delay stage 24 that delays the probe beam with respect to the pump beam, and a probe beam returned from the delay stage 24 is bent in a substantially right angle direction by the polarization beam splitter 22 and is placed on the optical path of the probe beam. The probe beam that has passed through the filter 26 and the ND filter 26 is reflected toward the sample 2 side. A mirror 28, and a lens 55 for focusing the probe beam reflected by the mirror 28, and a measuring instrument 6 polarizing direction rotation angle that measures the polarization direction rotation angle of the probe beam transmitted through the sample 2.

  A spin wave induction / initial phase control system 10 shown in FIG. 2 is a system in which main components of the spin wave induction / initial phase control apparatus 1 shown in FIG. By applying an external magnetic field in the x direction in 2, the initial spin in the sample 2 is directed in the direction of the initial magnetic field, a pump beam is incident in the z direction of the sample 2, and is generated by spin using the pump-probe method. A system that enables time-space-resolved measurement of a spin wave, which is a light source 3, a polarization azimuth rotation device 4 that passes a pump beam emitted from the light source 3, and a pump beam that has passed through the polarization azimuth rotation device 4 In order to obtain information on the function of the spin wave that is induced in the spot 8 of the pump beam irradiated to the sample 2 and propagated outside the spot 8 of the pump beam, either light source (see FIG. By transmitting the probe light emitted from the drawings) to the sample 2, and a polarization direction rotation angle of the measuring instrument 6 for enabling measurement of polarization direction rotation angle of the probe beam.

  Sample 2 is, for example, a ferrimagnetic insulator such as rare earth iron garnet.

  The electromagnet 41 is used for applying an external magnetic field. The dispersion relation of the spin wave itself depends on the initial magnetic field expressed as the vector sum of the applied external magnetic field and anisotropic magnetic field. The magnetic field intensity of the electromagnet 41 is about 1 kOe.

  The light source 3 is, for example, a femtosecond pulse laser light source. Specifically, the light source 3 may be a regenerative amplification titanium sapphire laser or the like that generates an optical pulse having a center wavelength of 800 nm and a time width of about 150 fs at a repetition frequency of 1 kHz. The light pulse energy of the light source 3 is about 1 mJ.

  The beam splitter 11 separates the light pulse emitted from the light source 3 into a pump beam and a probe beam. The beam splitter 11 guides about 80% of the separated optical pulses as a pump beam to the optical parametric amplifier 12 side, and the remaining about 20% of the optical pulses as a probe beam to the delay stage 24 side. Lead.

  The optical parametric amplifier 12 converts the wavelength of the pump beam to about 1200 to 2400 nm. When the light beam passes through the optical parametric amplifier 12, two wavelengths, for example, idler light having a wavelength of about 1800 nm and signal light having a wavelength of about 1400 nm are generated. Among them, only the signal light is guided to the chopper 13. The pulse energy of the light beam that has passed through the optical parametric amplifier 12 is about 30 μJ.

   The chopper 13 periodically chops the pump light by periodically interrupting at half the repetition frequency of the pump light whose wavelength is converted by the optical parametric amplifier 12. The chopper 13 may be configured as a rotating disk in which light reflecting portions and light transmitting portions are alternately arranged in the circumferential direction, and the pump light beam may be periodically reflected or passed by rotating the motor. The purpose of disposing the chopper 13 is to improve the signal-to-noise ratio of the signal to be acquired. The pump beam modulated by the chopper 13 is guided to the beam splitter 14.

   The beam splitter 14 transmits about 90% of the pump light chopped by the chopper 13 as it is, and guides the remaining about 10% of light to the photodetector 15 by bending it in a direction substantially perpendicular thereto.

  The photodetector 15 can monitor the intensity of the pump beam. When a pump beam of 1 kHz is chopped by the chopper 13 as a half frequency of the repetition frequency of the pump beam emitted from the optical parametric amplifier 12, the frequency drops to 500 Hz. This intensity can be detected by the photodetector 15.

  The mirror 16 is configured as a reflector that changes the optical path of the incident pump beam by reflecting the incident pump beam in a substantially perpendicular direction. Among these, the mirror 16 bends the optical path of the pump beam transmitted through the beam splitter 14 in a substantially right angle direction and guides it to the sample 2 side.

  The polarizer 18 converts the polarization of the pump beam reflected by the mirror 16 into linearly polarized light and guides it to the polarization azimuth rotation means 4.

  The polarization azimuth rotation device 4 is composed of, for example, a half-wave plate. The polarization azimuth rotation device 4 can freely rotate the polarization azimuth angle of the pump beam. However, the polarization azimuth rotation device 4 is not limited to this, and may be a spatial light phase modulator, for example, as long as the polarization azimuth angle of the pump beam can be freely rotated.

  The lens 5 collects the pump beam on the sample 2. The pump beam is reduced to a diameter of about 50 μm by the lens 5 and reaches the sample 2.

  The mirrors 21 and 28 are configured as reflecting plates that change the optical path by reflecting the incident probe beam. The mirror 21 reflects the probe beam transmitted through the beam splitter 11 in a substantially right angle direction and guides it to the delay stage 24 side. The mirror 28 reflects the probe light beam that is bent by the polarizing beam splitter 22 and reaches the sample 2 side.

  The polarization beam splitter 22 transmits the P-polarized light in the probe beam and reflects the S-polarized light.

  When the ¼ wavelength plate 23 tilts this optical axis to plus 45 ° or minus 45 ° with respect to the plane of linear polarization of the probe beam, the linear polarization of the probe beam becomes clockwise or counterclockwise circularly polarized light, respectively. can do.

  The delay stage 24 is used for adjusting the probe optical path length by the movable mirror 25 and the fixed mirror 27. The movable mirror 25 is adjusted to have a long probe optical path length when moved to the right in FIG. 1, and to a short probe optical path length when moved to the left in FIG. Therefore, the delay stage 24 can adjust the delay time between the pump light pulse and the probe light pulse by the movement of the movable mirror 25. The fixed mirror 27 can return the reflected light accurately on the optical path of the incident light by vertically reflecting the probe light incident vertically from the movable mirror 25. Here, the variable range of the probe optical path length is generally about 90 cm, and a delay time setting range of 0 to 3 ns is given between the probe light pulse and the pump light pulse.

  The delay stage 24 has been described by taking as an example the case of time delay by adjusting the optical path of the probe beam, but is not limited to this, and may be provided on the optical path of the pump beam. Accordingly, it is possible to delay the time by adjusting the optical path of the pump beam.

  Here, the probe beam emitted from the light source 3 is reflected by the mirror 21 while being P-polarized light, passes through the polarization beam splitter 22, and reaches the quarter-wave plate 23. This P-polarized light is converted into counterclockwise circularly polarized light by the quarter-wave plate 23. This counterclockwise circularly polarized light is converted into clockwise circularly polarized light when reflected by the movable mirror 25 and the fixed mirror 27 of the delay stage 24. When the clockwise circularly polarized light passes through the quarter wavelength plate 23 once passed, it is converted to S polarized light. S-polarized light is reflected in a substantially right angle direction by the polarization beam splitter 22 and guided to the mirror 28 side.

  The ND filter 26 adjusts the intensity of the probe beam. If the intensity of the probe beam applied to the sample 2 is too strong, the sample 2 may be damaged. If it is too weak, the signal of the probe beam becomes invisible. For this reason, it is necessary to adjust the intensity of the probe beam by the ND filter 26.

  After passing through the ND filter 26, the intensity of the probe beam further decreases, and immediately before the sample 2 is irradiated, the intensity ratio between the pump beam and the probe beam reaches about 1000: 1. Thus, by making the intensity of the probe light much smaller than the intensity of the pump light, the influence of the spin wave induced in the sample 2 due to the probe light can be kept small.

  The lens 55 collects the probe light beam reflected by the mirror 28 and irradiates the collected probe light beam on the surface of the sample 2 from the 7 ° direction of the normal line of the sample 2.

  The polarization azimuth measuring device 6 includes a Wollaston prism 33, a photodetector 34, and a photodetector 35.

  The Wollaston prism 33 separates the incident probe beam into two orthogonal linearly polarized lights. Here, when the sample 2 is not irradiated with the pump beam, it is separated into the linearly polarized light of the same intensity perpendicular to plus 45 ° and minus 45 ° with respect to the polarization plane of the probe beam perpendicularly incident on the Wollaston prism 33. . However, when the sample 2 is irradiated with a pump beam, Faraday rotation occurs in the probe beam due to the induction of the spin wave. As a result, the intensity of the probe light beam separated into + 45 ° and −45 ° of the probe light beam perpendicularly incident on the Wollaston prism 33 is different.

  The photodetectors 34 and 35 measure the intensity of the probe beam separated into two by the Wollaston prism 33, respectively. The polarization azimuth rotation angle of the probe beam is measured by taking the difference in the intensity of the probe beam detected by the photodetector 34 and the photodetector 35, and information on the perpendicular direction of the function of the spin wave propagated in the sample 2 Can be obtained.

  The pump beam has a repetition frequency of about 500 Hz, and its intensity is detected by the photodetector 15. The probe beam that has passed through the sample 2 is about 1 kHz, and its intensity is detected by the photodetector 34 and the photodetector 35. By comparing the intensities detected by the photodetectors 15, 34, and 35, it is possible to distinguish ON and OFF of the pump beam.

  Next, a spin wave induction / initial phase control apparatus 1 and a spin wave induction / initial phase control system 10 and a spin wave induction / initial phase control system 10 to which the present invention is applied will be described with reference to FIGS. This will be described in detail with reference to FIG.

FIG. 3 is a conceptual diagram showing the state of the initial magnetic field H ₀ and the initial spin M ₀ in the sample 2 when an external magnetic field is applied to the sample 2. FIG. 4 is a conceptual diagram showing a state in which the directions of the synthetic magnetic field H and the spin M are changed from the initial magnetic field H ₀ and the initial spin M ₀ when the sample 2 is irradiated with the pump beam emitted from the light source. is there. FIG. 5 is a conceptual diagram showing a state where the spin M is precessing around the synthetic magnetic field H after the sample 2 is irradiated with the pump beam. FIG. 6 is a conceptual diagram showing a state in which the polarization azimuth angle φ of the pump beam is changed by the polarization azimuth rotation device 4. FIG. 7 is a conceptual diagram showing a state in which the state in which the spin wave induced by the precession of the spin M in FIG. 5 propagates to the surroundings is detected by the probe beam.

  First, a spin wave induction / propagation control method in the spin wave induction / initial phase control system 10 will be described with reference to FIGS.

First, by applying an external magnetic field in the x direction of the sample 2 shown in FIG. 3, an initial magnetic field H ₀ is generated as a vector sum of the external magnetic field and the anisotropic magnetic field, and the direction of the initial spin M _{0 in} the direction of the initial magnetic field H _0. Are aligned. Next, the pump beam emitted from the light source 3 shown in FIG. 4 is condensed by the lens 5 through the polarization azimuth rotating device 4 and irradiated onto the sample 2. At this time, the vector sum of the initial magnetic field H ₀ and the magnetic field ΔH generated by the magnetic anisotropy modulation shown in FIG.

Further, the spin M is the vector sum of the initial spin M ₀ that is in the same direction as the initial magnetic field H ₀ and the spin modulation ΔM generated by the inverse cotton-Mouton effect. As shown in FIG. 5, the spin M rotates around the synthetic magnetic field H to start precession. The precession of the spin M propagates not only in the spot 8 of the pump beam but also outside the spot 8 of the pump beam, and the precession of the spin M starts outside the spot 8 of the pump beam, and a spin wave is induced. The

Then the linearly polarized light L polarization azimuth angle phi ₁ from the polarization azimuth angle phi ₁ to polarization azimuth angle phi ₂ of the linearly polarized light L ₂ of ₁ and the polarization azimuth is a pump light ray incident on the polarization azimuth angle spinning device 4 shown in FIG. 6 Change by the difference θ of φ ₂ . As a result, the initial phase of the spin wave induced in the spot 8 of the pump beam irradiated on the sample 2 is changed.

  Further, as shown in FIG. 7, the sample 2 is irradiated with the probe beam and transmitted, the polarization azimuth rotation angle of the transmitted probe beam is detected by the measuring device 6 of the polarization azimuth rotation angle, and the spin propagating through the sample 2. Get wave function information.

  Next, a spin wave induction / initial phase control method performed using the spin wave induction / initial phase control apparatus 1 will be described with reference to FIG.

  In this spin wave induction / initial phase control apparatus 1, the probe optical path length is changed by physically moving the movable mirror 25 of the delay stage 24 placed in the optical path of the probe beam by the pump-probe method. Adjust the delay time between the pump beam.

  The pump beam is applied to the sample 2 after being chopped by the chopper 13. By irradiation with the pump beam, a spin wave is induced in the spot 8 of the pump beam in the sample 2, and the spin wave propagates outside the spot 8 of the pump beam.

  The probe beam is incident on the sample 2 from the direction of 7 ° of the normal of the sample 2, the polarization azimuth rotation angle of the probe beam is measured by the polarization azimuth rotation angle measuring device 6, and the function of the propagating spin wave is measured. Information is analyzed. Here, by rotating the polarization azimuth angle of the pump beam irradiated into the sample 2 by the polarization azimuth rotation device 4, the initial phase of the spin wave induced in the spot 8 of the pump beam in the sample 2 changes. . The pump beam and the probe beam are shifted in the delay time by the delay stage 24, and the relative two-dimensional position of the probe beam with respect to the pump beam is shifted. Information on the function of the spin wave can be obtained.

  The probe light beam used in the spin wave induction / initial phase control device 1 and the spin wave induction / initial phase control system 10 is one for detecting information of the spin wave induced and propagated by the pump beam. Means. Therefore, any means may be used without being limited to the probe beam as long as the information of the spin wave can be detected.

  Next, an experimental result by the pump-probe method by the spin wave induction / initial phase control apparatus 1 shown in FIG.

FIG. 8 is a diagram showing the temporal change of the spin precession induced by irradiating the sample 2 with the pump beam, observed by the pump-probe method, for each polarization azimuth angle of the pump beam. 8 shows the delay time of the probe beam with respect to the pump beam on the horizontal axis, and the polarization azimuth angle φ, which is an angle from the x direction that is the same direction as the external magnetic field of FIG. 6 of the pump beam, is −90 °, −60 °, The experimental results shown in graphs g1 to g7 are plotted with the polarization azimuth rotation angle of the probe beam at −30 °, 0 °, 30 °, 60 °, and 90 ° as the vertical axis. The peak P shown in FIG. 8 changes from P ₁ to P ₇ . This showed that spin precession was induced in the garnet when pumped with linearly polarized light. It was also demonstrated that the initial phase C of the spin wave changes due to the change in the polarization azimuth angle φ of the pump beam.

  FIG. 9 is a diagram showing a numerical analysis result obtained by extracting the case where the polarization azimuth angle of the pump beam is −60 ° from the experimental graph of FIG. 8 and fitting the graph. The numerical analysis result obtained by fitting in FIG. 9 can be expressed by Expression (3). The unit of the polarization direction rotation angle of the probe beam on the vertical axis shown in FIG. 9 is obtained by offsetting the unit of the polarization direction rotation angle of the probe beam on the vertical axis shown in FIG.

  A, B, C, D, and E in this equation (3) are fitting parameters. Among these, in particular, A represents the vibration amplitude, B represents the relaxation time, and C represents the initial phase.

  FIG. 10A is a diagram showing experimental results showing the relationship between the vibration azimuth A of the polarization azimuth angle φ of the pump beam and the polarization azimuth rotation angle of the probe beam. FIG. 10B is a diagram showing experimental results showing the relationship between the polarization azimuth angle φ of the pump beam and the initial phase C of vibration of the polarization azimuth rotation angle of the probe beam. 10A and 10B, a plurality of polarization azimuth angles φ are set more finely including the fitting of the graph g6 shown in FIG. 9 including the other graphs g1 to g5 and g7. Further, the equation (3) is applied to extract the vibration amplitude A and the initial phase C corresponding to the polarization azimuth angle φ, and the relationship between the polarization azimuth angle φ and the vibration amplitude A and the polarization azimuth angle φ and the initial phase C. Shows the relationship.

  FIG. 10B shows that the initial phase C continuously changes with respect to the continuous change in the polarization azimuth angle φ of the pump light.

  Next, a numerical calculation model in the spin wave induction / initial phase control system 10 shown in FIG. 2 to which the present invention is applied will be described.

  As the modulation mechanism of the spin M and the synthetic magnetic field H at the time of light irradiation, the following two modulations are assumed. One is that a spin M modulated by the inverse cotton Mouton effect is generated, and the other is that a synthetic magnetic field H modulated by magnetic anisotropy modulation is generated.

The inverse cotton-Mouton effect can be said to be that the spin modulation ΔM is proportional to the second order of the initial spin M ₀ and the incident pump photoelectric field E as shown in the equation (4).

  On the other hand, magnetic anisotropy modulation is a phenomenon in which charge transfer occurs between Fe ions having different valences by irradiation with pump light, and as a result ΔH occurs. It is assumed that the relationship between the modulation amount and the incident pump photoelectric field is phenomenologically expressed as the following equation (5).

Expression (5) is an expression expressing magnetic anisotropy modulation. Here, E _k and _El are the same as spin. (I, j, k, l) represents (x, y, z).

  Here, the correspondence between the magnetization motion and the polarization azimuth rotation angle obtained as an experimental result is described. Vectors M (t) and H are the vectors of spin M and synthetic magnetic field H immediately after receiving the inverse cotton-Mouton effect and magnetic anisotropy modulation by the pump beam.

  The spin M (t) and the synthetic magnetic field H can be expressed by the following equations.

FIG. 11 is a conceptual diagram showing the relationship between the vector u ₁ , the vector u ₂ , and the vector u ₃ when the spin M (t) precesses around the synthetic magnetic field H.

Further, the vector M (t) can be expressed by the following mathematical formula using the vector u ₁ , the vector u ₂ , and the vector u ₃ .

  Here, it is assumed that the z component of Expression (10) is extracted and is equal to Expression (3).

  That is, the equation (14) can be transformed as the following equation (1).

Equation (1) shows that the initial phase C can be controlled by the variables of the vector u ₁ and the vector u ₂ .

Expression (15) shows the relationship between the polarization azimuth angle φ of the pump beam and the pump photoelectric fields E _x and E _y .

FIG. 12A is a diagram showing experimental results and numerical analysis results showing the relationship between the polarization azimuth angle φ and u _1z of the pump beam. FIG. 12B is a diagram showing experimental results and numerical analysis results showing the relationship between the polarization azimuth angle φ of pump light and u _2z .

Graph by a dotted line shown in FIG. 12 (a) shows the experimental results with the polarization azimuth angle φ of u _1z and the pump light, the graph represented by the solid line, the polarization azimuth of u _1z and the pump light φ The relationship between u _1z calculated by the models shown in Equations (1) to (15) and the polarization azimuth angle φ of the pump beam is shown. 12B shows the experimental results of u _2z and the polarization azimuth angle φ of the pump beam, and the graph represented by a solid line shows the polarization azimuth angle of u _2z and the pump beam. The relationship between u _2z calculated by the equations (1) to (15) with φ and the polarization azimuth angle φ of the pump beam is shown.

  FIG. 12 shows that the experimental result and the numerical analysis result can be fitted, and it is shown that the magnetic anisotropy modulation and the inverse cotton-Mouton effect occur simultaneously. The polarization azimuth of the initial phase of the spin wave Dependency proved. That is, it was shown that the initial phase C of the spin wave induced in the sample 2 can be controlled by rotating the polarization azimuth angle φ of the pump beam with the polarization azimuth rotation device 4.

  Therefore, the spin wave induction / initial phase control device 1 and the spin wave induction / initial phase control 10 are based on the model of the equation (1) by changing the polarization azimuth angle φ of the pump beam by the polarization azimuth rotation device 4. Thus, the initial phase C of the spin wave can be controlled.

  Further, since the polarization of the pump beam is linearly polarized light, the polarization azimuth angle φ of the pump beam can be continuously changed, and the initial phase C is also continuously changed according to the continuous change of the polarization azimuth angle φ. It becomes possible to change to.

Second embodiment

  Next, the synthesized spin wave synthesized by interference of the spin waves induced by the spots of the plurality of pump beams changes the initial phase of each spin wave, thereby controlling the propagation direction of the synthesized spin wave. The induction / propagation control device 1 ′, the spin wave induction / propagation control system 10 ′, and the spin wave induction / propagation control method will be described with reference to FIGS.

  The case of two pump beam spots among a plurality of pump beam spots will be described with reference to FIGS.

  FIG. 13 is a schematic diagram showing a configuration of a synthetic spin wave induction / propagation control device 1 ′ using two pump beam spots according to the pump-probe method to which the present invention is applied. FIG. 14 is a conceptual diagram of a spin wave induction / propagation phase control system 10 ′ extracted from main components of the spin wave induction / propagation control apparatus 1 ′ shown in FIG. 13 to which the present invention is applied.

  The spin wave induction / propagation control device 1 ′ shown in FIG. 13 applies an external magnetic field by an electromagnet 41 ′ in the in-plane direction of a flat sample 2 ′ to direct the spin in the sample 2 ′ in the initial magnetic field direction. In this apparatus, a pump beam is incident in the direction perpendicular to the surface of the sample 2 ′, and a time-space-resolved measurement of a spin wave generated by the spin is performed by a pump-probe method.

  The spin wave induction / propagation control device 1 ′ is arranged on a light source 3 ′, a beam splitter 11 ′ that separates light beams emitted from the light source 3 ′, and an optical path of pump light beams that have passed through the beam splitter 11 ′. And an optical parametric amplifier 12 'for converting the wavelength of the pump beam, and a chopper 13' for chopping the pump beam at a half frequency of the repetition frequency of the pump beam folded in a substantially perpendicular direction by the optical parametric amplifier 12 '; A beam splitter 14 ′ that separates the pump beam that has passed through the chopper 13 ′, a photodetector 15 ′ that detects the intensity of one separated pump beam, and a beam splitter 36 ′ that separates the other separated pump beam. And a mirror 16 'for reflecting one pump beam from the beam splitter 36' in a substantially perpendicular direction. A polarizer 18a ′ that makes the pump beam reflected by the mirror 16 ′ linearly polarized light, a polarization azimuth rotation device 4a ′ that can rotate the polarization azimuth angle of the pump beam that has passed, and a polarization azimuth rotation device 4a 'A lens 5a' for condensing the pump beam passing through ', a mirror 37' for reflecting the other pump beam from the beam splitter 36 'in a substantially right angle direction, and a pump beam reflected by the mirror 37' in a substantially right angle direction. Mirror 38 'that is reflected to the sample 2' side, the polarizer 18b 'that makes the pump beam reflected by the mirror 38' linearly polarized light, and the polarization that enables rotation of the polarization azimuth angle of the passed pump beam An azimuth rotation device 4b ′ and a lens 5b ′ that collects the pump beam that has passed through the polarization azimuth rotation device 4b ′ are provided.

  In addition, the spin wave induction / propagation control device 1 ′ includes a mirror 21 ′ disposed on the optical path of the probe beam bent and separated in a substantially right angle direction by a beam splitter 11 ′, and a substantially right angle direction by the mirror 21 ′. A polarizing beam splitter 22 'for guiding the probe light beam bent to the delay stage side, a quarter wavelength plate 23' for converting the probe light beam from the polarizing beam splitter 22 'from linearly polarized light to circularly polarized light, and 1/4 A delay stage 24 ′ that delays the probe beam that has passed through the wave plate 23 ′ with respect to the pump beam, and the probe beam that has returned from the delay stage 24 ′ are bent in a substantially right angle direction by the polarization beam splitter 22 ′. An ND filter 26 ′ arranged on the optical path of the probe beam, and the probe beam that has passed through the ND filter 26 ′ is sample 2 ′. Mirror 28 'that reflects to the side, lens 55' that collects the probe light reflected by the mirror 28 ', and a polarization azimuth rotation angle measuring instrument that measures the polarization rotation angle of the probe light that has passed through the sample 2' 6 '.

  The spin wave induction / propagation control system 10 ′ shown in FIG. 14 applies the magnetic field in the x direction in the flat sample 2 ′ so that the initial spin in the sample 2 ′ is directed in the direction of the initial magnetic field. A pump / probe measurement system that enables time-space-resolved measurement of a spin wave generated by entering a pump beam in the z direction, which is the direction perpendicular to the plane of ′, and is emitted from any light source (not shown) A polarization azimuth rotating device 4 'that passes the pump beam, a lens 5' that collects the pump beam that has passed through the polarization azimuth rotating device 4 ', and a spot 8' of the pump beam irradiated on the sample 2 '. In order to obtain information on the function of the spin wave that is induced and propagated outside the spot 8 ′ of the pump beam, the probe beam emitted from any one of the light sources (not shown) is transmitted through the sample 2 ′. Probe beam And a polarization azimuth rotation angle measuring device 6 ′ capable of measuring the polarization azimuth rotation angle.

  Here, in the configuration of the spin wave induction / propagation control device 1 ′ shown in FIG. 13, the polarizers 18a ′ and 18b ′, the polarization azimuth rotation devices 4a ′ and 4b ′, and the lenses 5a ′ and 5b ′ are respectively the first. The configuration is the same as that of the polarizer 18, the polarization azimuth rotation device 4, and the lens 5 of one embodiment. Further, the configuration of the first embodiment is the same as the configuration of the spin wave induction / initial phase control device 1 of the first embodiment except for the configuration of the other beam splitter 36 ′, the mirror 37 ′, and the mirror 38 ′. Will be omitted.

  The beam splitter 36 'transmits 50% of the pump beam and reflects the remaining 50%.

  The mirrors 37 ′ and 38 ′ are configured as reflecting plates that change the optical path by reflecting the incident pump beam in the same manner as the mirror 16 of the first embodiment.

  Here, as shown in FIG. 13, one of the pump beams separated by the beam splitter 36 ′ and reflected by the mirror 16 ′ passes through points a and d, and then bends in a substantially right angle direction at point m. And reaches the point n on the sample 2 '. The optical path of this one pump beam is called an optical path admn. The pump beam separated by the beam splitter 36 'is bent in a substantially right angle direction from the point a to the optical path of one pump beam, bent in a substantially right angle direction in the b point, and further bent in a substantially right angle direction in the c point. Passes through the point d, and then reaches the point h on the sample 2 '. The other optical path of the pump beam is called an optical path abcdh. Here, the distance between the m point and the n point is equal to the distance between the d point and the h point, the distance between the a point and the m point, the distance between the a point and the b point, the distance between the b point and the c point, and the c point d. It is designed to be equal to the distance including the distance between points. Thereby, the distance between the optical path admn and the optical path abcdh becomes equal. For this reason, the two pump beams separated by the beam splitter 36 ′ simultaneously reach the sample 2 ′. Accordingly, the pump beam spot 8a ′ and the pump beam spot 8b ′ on the sample 2 ′ shown in FIG. 14 are generated simultaneously.

  Next, the spin wave induction / propagation control method in the spin wave induction / propagation control device 1 ′ and the spin wave induction / propagation control system 10 ′ to which the present invention is applied will be described in detail with reference to FIGS. Explained.

  First, a spin wave induction / propagation control method in the spin wave induction / propagation control system 10 'will be described with reference to FIG.

First, an external magnetic field is applied in the x direction of the sample 2 ′ shown in FIG. Two pump beams emitted from one of the light sources (not shown) are condensed by the lenses 5a ′ and 5b ′ via the polarization azimuth rotating devices 4a ′ and 4b ′, and the sample 2 ′. Irradiate. At this time, two spin waves w _a and w _b are induced and interfered with the spots 8 a ′ and 8 _b ′ of the pump beam formed by irradiating the sample 2 ′ with the two pump beams. A synthetic spin wave w _c is induced by the interference of the spin waves w _a and w _b .

Further, the sample beam 2 ′ is irradiated with the probe beam and transmitted, the polarization azimuth rotation angle of the transmitted probe beam is detected by the measuring device 6 of the polarization azimuth rotation angle, and the synthesized spin wave w _c propagating in the sample 2 ′ is detected. Get information about the function.

  Next, a spin wave induction / propagation control method performed using the spin wave induction / propagation control apparatus 1 ′ will be described with reference to FIG.

  In this spin wave induction / propagation control device 1 ', the probe optical path length is changed by physically moving the movable mirror 25' of the delay stage 24 'placed in the optical path of the probe beam by the pump-probe method. Then, the delay time between the pump beam is adjusted.

The pump beam emitted from the light source 3 'is separated into two beams by the beam splitter 36', one pump beam is passed on the optical path admn, and the other pump beam is passed on the optical path abcdh. As a result, since the pump beam is irradiated onto the sample 2 ′ at the same timing, spots 8a ′ and 8b ′ of the pump beam are simultaneously formed, and spin waves are simultaneously generated in the spots 8a ′ and 8b ′ of the pump beam. Induced. Thereafter, the spin waves w _a and w _b simultaneously induced in the pump beam spots 8 a ′ and 8 _{b ′} are propagated outside the pump beam spots 8 a ′ and 8 _b ′ to cause interference to induce a synthesized spin wave w _c . Let

The probe beam is incident on the sample 2 ′ from the normal direction of the sample 2 ′, and the polarization direction rotation angle of the probe beam is measured by the measuring device 6 ′ of the polarization azimuth rotation angle. Analyze the function information of the wave w _c . Here, by rotating the polarization azimuth angle of the pump beam irradiated into the sample 2 ′ by the polarization azimuth rotation device 4 ′, the pump beam spots 8 a ′ and 8 b ′ in the sample 2 ′ are induced. The initial phase of the spin waves w _a and w _b is changed. The pump beam and the probe beam are shifted in the delay time by the delay stage 24 ′, and the relative two-dimensional position of the probe beam with respect to the pump beam is shifted, so that the time-space decomposition of the synthesized spin wave w _c becomes possible. Information on the function of the spatio-temporal synthesized spin wave w _c can be obtained.

  The probe beam used in the spin wave induction / propagation control device 1 ′ and the spin wave induction / propagation control system 10 ′ is one for detecting information on the spin wave induced and propagated by the pump beam. Means. Therefore, any means may be used without being limited to the probe beam as long as the information of the spin wave can be detected.

13 and 14 show the interference of the two spin waves w _a and w _b induced by the spots of the two pump beams. Similarly, the beam splitter 14 ′ and the beam splitter 36 ′ By providing another plurality of beam splitters 36 ′ and a plurality of mirrors 37 ′ and 38 ′ therebetween, it is possible to separate the light into three or more pump beams. Furthermore, by making the pump optical path lengths separated into a plurality of light beams equal, a plurality of pump light spots 8 ′ formed on the sample 2 ′ can be generated simultaneously.

  Next, a numerical calculation model when the number of spots of a plurality of pump beams is nine in the spin wave induction / propagation control system 10 ′ shown in FIG. 14 to which the present invention is applied will be described. However, the intensity of each pump beam is the same.

Using h _n (vector k) as a spin wave source, a model of the following equation (2) was established.

 Here, t represents time.

Here, ω (vector k) represents the dispersion relation of the angular frequency of the spin wave. However, the in-plane anisotropy was set to 0 for simplicity. α is a relaxation coefficient of the spin wave when the vector k = 0. This α can be obtained by an experiment of magnetic resonance. C _n represents the initial phase of the spin precession within the spot of the nth pump beam. _{M N} (vector r, t), which is a function of the synthesized spin wave, can be obtained by integrating in the wave number space. The initial phase C _n of the spin wave depends on how the light and the magnetic material interact. When the pump light pulse that is linearly polarized induces spin precession, C _n is shown in FIG. 10 (b) according to the polarization azimuth of the linearly polarized pump beam by the inverse Cotton Mouton effect and magnetic anisotropic modulation. ) Changes continuously as shown.

The spin wave induction / propagation control device 1 ′ and the spin wave induction / propagation control system 10 ′ shown in FIGS. 13 and 14 include two spins induced from two pump beam spots 8 a ′ and 8 b ′. A synthesized spin wave w _c synthesized by the waves w _a and w _b interfering with each other is induced, the initial phase C of each of the two spin waves is changed, and the synthesis is performed based on the model of equation (2). Controls the function of the spin wave w _c . Thus, a desired function of the synthesized spin wave w _c can be obtained by controlling the initial phase C of each of the two spin waves w _a and w _b . The addition (2), characteristics of the sample 2 'prediction, because it is based on relaxation coefficient dispersion relation and synthetic spin wave w _c of the angular frequency of the synthetic spin waves w _c, advance the characteristics of a sample 2'numerically Thus, it is possible to select the sample 2 ′ for inducing the desired synthesized spin wave w _c or to synthesize the desired sample 2 ′. Thereby, a desired synthetic spin wave w _c can be created. The spin wave induction / propagation control device 1 ′ and the spin wave induction / propagation control system 10 ′ show the case of two pump beam spots 8 a ′ and 8 b ′, but are not limited thereto. Instead, it may be a synthesized spin wave w induced by the interference of a plurality of spin waves w induced by three or more pump light spots formed by three or more pump light beams.

  Further, since the pump light polarization is linearly polarized light, the polarization azimuth angle φ of the pump beam can be continuously changed, and the initial phase C is also continuously changed according to the continuous change of the polarization azimuth angle φ. It can be changed.

  Next, a numerical simulation result in the case of one or nine pump beam spots based on the model (2) of the spin wave induction / propagation control device 1 ′ and the spin wave induction / propagation control system 10 ′ is illustrated. This will be described in detail with reference to FIGS.

FIG. 15 is a conceptual diagram showing a state in which nine spin waves on the sample 2 interfere with each other by the pump-probe method of the second embodiment to which the present invention is applied. FIG. 15 shows nine pump beam spots S ₁ , S ₂ , S ₃ , S ₄ , S ₅ , S ₆ , S ₇ , S ₈ , S ₉ , spin waves w ₁ , w ₂ , w ₃ , It shows the interference _{w 4, w 5, w 6} , w 7, w 8, w 9.

  Next, FIG. 16 shows a numerical simulation result in the case of one spot 8 of the pump beam by the model (2) of the spin wave induction / propagation control device 1 ′ and the spin wave induction / propagation control system 10 ′. Details will be described with reference to FIG.

  FIG. 16A shows an amplitude map of a spin wave 3 ns after irradiation with linearly polarized pump light in the case of one pump beam spot when the polarization azimuth rotation device 4 ′ is a half-wave plate. FIG. FIG. 16B is a diagram showing a phase map of spin waves in the case of FIG.

  16 (a) and 16 (b), it can be seen that the spin wave isotropically propagates in all directions such as the arrow direction when the number of the spot of the pump beam is one.

  Next, numerical simulation results in the case of nine pump beam spots according to the model of the formula (2) of the spin wave induction / propagation control device 1 ′ and the spin wave induction / propagation control system 10 ′ are shown in FIGS. Will be described in detail with reference to FIG. Here, it is assumed that the spot shapes of the nine pump beams are substantially circular, are all circular two-dimensional Gaussian functions, and have the same full width at half maximum.

FIG. 17A shows a case where the initial phases C _n of the spin waves induced from the spots of nine pump beams when the polarization azimuth rotation device 4 ′ is a half-wave plate are all in phase. It is the figure which showed the amplitude map of the spin wave after 3 ns from linearly polarized light pump irradiation. FIG. 17B is a diagram showing a phase map of spin waves in the case of FIG.

17A and 17B, there are nine pump beam spots, and there is no phase difference in the initial phase C _n of all spin waves. That is, in the case of C _n = 0 °, it can be seen that the synthesized spin wave in which nine spin waves are synthesized propagates the spin wave in the left-right direction indicated by the arrow direction.

FIG. 18A shows that the phase difference of the initial phase C _n of the spin wave induced from the spots of nine pump beams when the polarization azimuth rotating device 4 ′ is a half-wave plate is 60 °. FIG. 18B is a diagram showing an amplitude map of a spin wave 3 ns after irradiation with the linearly polarized pump light, and FIG. 18B is a diagram showing a phase map of the spin wave in the case of FIG. Here, the case _where the phase difference of the initial phase C _n of the spin wave is 60 ° is a case where C _n = 60 ° × (n−4) (where n = 1 to 9).

  18A and 18B, when the number of pump light spots is nine and the phase difference of all the spin waves is 60 °, nine spin waves are synthesized in the diagonally upward and left directions indicated by the arrows. It can be seen that the synthetic spin wave propagates.

FIG. 19A shows that when the polarization azimuth rotation device 4 ′ is a half-wave plate, the initial phase C _{n of} spin waves induced from the spots of nine pump beams is C _n = 15 °. It is the figure which showed the amplitude map of the spin wave 3ns after linearly polarized light pump light irradiation in the case of * (n-4) < ² > (however, n = 1-9). FIG. 19B is a diagram showing a phase map of spin waves in the case of FIG.

19 (a) and 19 (b), when the initial phase C _n of the spin wave with nine pump light spots is C _n = 15 ° × (n−4) ² , the horizontal direction indicated by the arrow direction, It can be seen that the synthesized spin wave, in which nine spin waves are synthesized in the left and right diagonally upward direction and the left and right diagonally downward direction, propagates and converges.

FIG. 20A shows that the initial phase C _n of the spin wave induced from the spots of the nine pump beams when the polarization azimuth rotation device 4 ′ is a half-wave plate is C _n = 60 °. It is the figure which showed the amplitude map of the spin wave 3ns after linearly polarized light pump light irradiation in the case of * (n-4) +15 degrees * (n-4) < ² > (however, n = 1-9). FIG. 20B is a diagram showing a phase map of spin waves in the case of FIG.

20A and 20B, when the initial phase C _n of the spin wave with nine spots of the pump beam is C _n = 60 ° × (n−4) + 15 ° × (n−4) ² It can be seen that a synthesized spin wave in which nine spin waves are synthesized propagates and converges in the left-right direction indicated by the arrow direction, the left-right diagonally upward direction, and the left-right diagonally downward direction.

  Although the embodiments and application examples of the present invention have been described in detail above, the above-described embodiments and application examples are merely examples of implementation in carrying out the present invention, and the present invention is thereby limited. This technical scope should not be interpreted in a limited way.

1 Spin Wave Induction / Initial Phase Control Device 1 ′ Spin Wave Induction / Propagation Control Device 2, 2 ′ Sample 3, 3 ′ Light Source 4, 4a ′, 4b ′ Polarization Azimuth Rotation Device 5, 5a ′, 5b ′ Lens 6, 6 ′ Polarization azimuth angle measuring device 8, 8 ′, 8a ′, 8b ′ Pump beam spot 10 Spin wave induction / initial phase control system 10 ′ Spin wave induction / propagation control system 11, 11 ′, 14, 14 'beam splitter 12, 12' optical parametric amplifier 13, 13 'chopper 15, 15', 34, 34 ', 35, 35' photodetector 16, 16 ', 21, 21', 28, 28 ', 37 ', 38' Mirror 18, 18a ', 18b' Polarizer 23, 23 '1/4 wavelength plate 22, 22' Polarizing beam splitter 24, 24 'Delay stage 25, 25' Movable mirror 26, 26 'ND filter 2 , 27 'fixed mirror 33,33' Wollaston prism 36' beam splitter 41,41' electromagnet S1 of the pump light spot w _a, w _b spin wave w _c synthetic spin wave

Claims (8)

A light source;
A polarization azimuth rotation means capable of rotating the polarization azimuth angle of the pump beam emitted from the light source;
A medium disposed on an optical path through which the pump beam passes through the polarization azimuth rotating means and capable of inducing a spin wave;
When the pump beam is irradiated toward the medium, the spin wave is induced in the medium, and the polarization azimuth angle of the pump beam is changed by the polarization azimuth rotation unit based on the following equation (1). A spin wave induction / initial phase control system characterized by controlling the initial phase of the induced spin wave.
The spin wave induction / initial phase control system according to claim 1, wherein the pump beam emitted from the light source is linearly polarized light. N pump beams are irradiated toward the medium, and N spin waves induced in the medium propagate and interfere with each other to induce a synthetic spin wave,
2. The polarization azimuth rotation means in the spin wave induction / initial phase control system according to claim 1 changes the polarization azimuth of the N pump beams to change the initial phase of each of the N spin waves. By controlling the function of the synthetic spin wave, the spin wave induction / propagation control system is controlled based on the following equation (2).
The spin wave induction / propagation control system according to claim 3, wherein the pump beam emitted from the light source is linearly polarized light. A first step of irradiating the medium with a pump beam emitted from a light source via a polarization azimuth rotating unit that rotates a polarization azimuth of the pump beam to induce a spin wave in the medium;
A spin wave comprising: a second step of controlling an initial phase of the spin wave by changing a polarization azimuth angle of the pump beam by the polarization azimuth rotation means based on (1) below. Induction / initial phase control method.
The spin wave induction / initial phase control method according to claim 5, wherein the pump beam emitted from the light source is linearly polarized light. The pump light emitted from the light source is irradiated onto the medium via the polarization azimuth rotating means for rotating the polarization azimuth angle of the pump light, and N spin waves are induced and interfered in the medium. A first step of inducing a synthetic spin wave;
6. The spin wave induction / initial phase control method according to claim 5, wherein the polarization azimuth rotation means changes the polarization azimuth angle of the N pump beams to change the initial phase of each of the N spin waves. And a second step of controlling the function of the synthetic spin wave based on the following formula (2): a spin wave induction / propagation control method.
The spin wave induction / propagation control method according to claim 7, wherein the pump beam emitted from the light source is linearly polarized light.