JP4786928B2 - Waveguide element, spatial modulation element, and time modulation element - Google Patents

Description

The present invention relates to a waveguide element used for spatial distribution, branching, synthesis, spatial modulation, time modulation, or wiring of an optical signal in the nanometer region, and a spatial modulation element including the waveguide element and The present invention relates to a time modulation element.
More particularly, the present invention relates to an optical frequency multiplexed signal distribution element, an optical signal combining element, and an optical signal time in optical device technology and optical integrated circuit technology that handle information in the nanometer region below the diffraction limit of light. The present invention relates to a wiring technology for a modulation element, a spatial modulation element in a nanoscale region, and a micro optical waveguide. Furthermore, the present invention relates to a waveguide element, a spatial modulation element, and a time modulation element that can be used as an element for introducing a wavelength multiplexed signal in a conventional optical communication network into an optical device in the nanometer region. Here, although the optical frequency and the wavelength are treated synonymously in the region above the diffraction limit of light, the wavelength of light is not defined in the nanometer region, and therefore the waveguide element of the present invention, particularly, the waveguide element is used. The operation of the plasmon spatial modulation element and time modulation element will be described as the optical frequency.

  With the increase in information capacity in recent years, optical information processing systems and nano-optical devices in the nanoscale region exceeding the diffraction limit of light have become necessary. Here, it is necessary to divide the wavelength multiplexed signal that has propagated through the optical communication network in the nanometer range and perform various information processing, but the technology for branching, synthesizing, and copying signals at the nanoscale is still known. Not.

The plasmon resonance effect depending on the size of the metal fine particles used in the present invention is known and is described in Non-Patent Document 1 below.
In addition, there are already some known literatures regarding plasmon propagation and signal control by metal fine particles used in the present invention, and the metal fine particle array waveguide and plasmon interference described in Non-Patent Document 2 below are used. And a plasmon concentrator described in Non-Patent Document 3 below have been proposed.

Further, as a technique using plasmons generated in a metal periodic structure as in the present invention, an optical element described in Patent Document 1 below and an optical head using the same have been proposed.
Further, as a technique using the plasmon energy propagation mechanism, a recording medium, a near-field optical head, and an optical storage device in which metal fine particles are dispersed as described in Patent Document 2 below have been proposed.

JP 2003-287656 A Japanese Patent Laid-Open No. 13-283466 Fukui and Otsu, “Basics of Optical Nanotechnology” (Ohm) M.L.Brongersma, J.W.Hartman, and A.Atwater, Phys.Rev.B62 (2000) R16 356) Nomura, Yai, Hoki, Otsu: Proceedings of the 64th JSAP Scientific Meeting, 1p-Q-4

Here, the prior art described in Non-Patent Document 1 is a general known technique related to a resonance phenomenon caused by localized surface plasmons of metal fine particles, and describes the size dependency of plasmons of metal fine particles.
Further, as shown in FIG. 10, the prior art described in Non-Patent Document 2 uses a plasmon propagation in which metal fine particles are linearly arranged and electric dipole coupling between metal fine particles is used. A waveguide structure with less is realized. The symbols L and T in FIG. 10 indicate whether the direction of the electric dipole is the longitudinal direction (longitudinal mode) or the transverse direction (transverse mode) with respect to the propagation direction of the plasmon. It shows that a waveguide or a T-shaped branch can be configured. In addition, it is shown that a switch based on plasmon interference can be realized by exciting the plasmons subjected to deflection control using the three terminals of the T-shaped branch path as input, output, and control terminals.

  The plasmon concentrator in the prior art described in Non-Patent Document 3 is one in which metal fine particles are arranged in an arc shape at an appropriate interval as shown in the electron microscope image of FIG. The surface plasmon on the plane is scattered and diffracted, and as a result of the plasmon interference due to the phase relationship adjusted by the position of the metal fine particle, a plasmon concentrator that concentrates the energy of the incident plasmon at one point is realized.

  As shown in FIG. 12, the optical element in the prior art described in Patent Document 1 includes a plasmon effect by inserting a layer having an effect of improving surface unevenness as an intermediate layer 21 between conductive films 20. Thus, a highly efficient and high-resolution optical element 10 that is efficiently amplified at the same time, and an optical read / write head that enables reading and writing at a scale below the wavelength on the optical disk using the optical element 10 can be obtained. As a result, it is possible to record / read linear data density much higher than the linear data density limited by the diffraction limit of light.

  The recording medium, the near-field optical head, and the optical storage device in the prior art described in Patent Document 2 are information for realizing recording and reading of high-density information by interaction with the recording medium via near-field light. For the purpose of providing a recording / reading apparatus, in particular, a near-field optical head with high light efficiency and a method for manufacturing the same, as shown in FIG. 13, fine metal particles are dispersed in minute apertures for generating near-field light 6. By forming the layer 14, an energy propagation mechanism via plasmons is realized, and an improvement in light efficiency is realized.

Here, the prior art described in Non-Patent Document 2 considers coupling and propagation of light selected at a single optical frequency, that is, a plasmon resonance frequency of a single metal fine particle, and wavelength (frequency) multiplexed light. It is not intended for connection with conventional optical communication technologies such as separation, modulation, and combination of the above.
The prior art described in Non-Patent Document 3 is intended to collect surface plasmons, and the frequency of plasmons input to a nanoscale optical device arranged downstream of the collector is the lower layer of the collector. This is the excitation frequency of surface plasmons in the metal film. Therefore, it cannot be applied to information processing for multiple multiplexed frequencies.
Further, the prior art described in Patent Document 2 shows an improvement in transmittance due to the coupling between randomly dispersed metal fine particles, and since there is no periodicity, a plasmon waveguide mode is not formed, It cannot be applied to information processing technology using interference.

The present invention has been made in view of the above circumstances, and one of its purposes is the spatial distribution, branching, synthesis, and spatial modulation of optical signals in the nanometer range with respect to input signal light having a plurality of optical frequency components. It is to provide a waveguide element used for time modulation or wiring, and a spatial modulation element and a time modulation element constituted by the waveguide element.
Another object of the present invention is to provide a technique for ensuring the freedom of wiring and ease of processing in an optical integrated circuit in the nanometer region.

In order to achieve the above object, the present invention employs the following technical means.
A first means of the present invention is a waveguide element that propagates plasmons, and has a different size from a waveguide structure in which metal fine particles of uniform size are linearly arranged on a smooth substrate at equal intervals. A waveguide structure in which metal fine particles are linearly arranged at equal intervals is provided in multiple stages (claim 1).
The second means of the present invention is a spatial modulation element constituted by the waveguide element of the first means, and is excited corresponding to the frequency of light incident on the input end of the waveguide element . The plasmon is selectively coupled to a waveguide structure made of metal fine particles of different sizes of the waveguide element , and propagates the plasmon (claim 2).

The third means of the present invention is a time modulation element constituted by the waveguide element of the first means, and in the waveguide structure, the propagation speed of plasmon differs depending on the size of the metal fine particles. And a time delay is applied to each frequency component of the plasmon.
The fourth means of the present invention is a time modulation element constituted by the waveguide element of the first means. In the waveguide structure, the propagation speed of plasmon differs depending on the distance between the metal fine particles. Thus, a time delay is given to each frequency component of the plasmon (claim 4).

The fifth means of the present invention is a spatial modulation element constituted by the waveguide element of the first means, and each of the frequency components of the plasmon is obtained by having each waveguide structure spatially expanded. Spatial branching is provided (claim 5).
The sixth means of the present invention is a spatial modulation element constituted by the waveguide element of the first means, and each waveguide structure is arranged so as to be bent at a right angle, so that each frequency of the plasmon is The deflection direction of the component is maintained and spatially branched (claim 6).

A seventh means of the present invention is a waveguide element that propagates plasmon, and has the same size as a waveguide structure in which metal fine particles of uniform size are linearly arranged on a smooth substrate at equal intervals. It has a multi-stage waveguide structure made of metal fine particles having different intervals (claim 7).
The eighth means of the present invention is a spatial modulation element constituted by the waveguide element of the seventh means, and utilizes the fact that the plasmon propagation speed varies depending on the distance between the metal fine particles. Is deflected (claim 8).

A ninth means of the present invention is a waveguide element for propagating plasmons, which is different from a waveguide structure in which metal fine particles of uniform size are linearly arranged on a smooth substrate at equal intervals. A waveguide structure in which metal fine particles are linearly arranged at equal intervals has a structure that intersects each other (claim 9).
The tenth means of the present invention is a spatial modulation element constituted by the waveguide element of the ninth means, and each frequency component of plasmon is mixed by the difference in resonance frequency between metal particles of different sizes. The transmission is performed without any problem (claim 10).
Further, an eleventh means of the present invention is a spatial modulation element constituted by the waveguide element of the ninth means, and at a point where the waveguide structure intersects, one metal fine particle in one waveguide structure is It has a structure in which metal fine particles having different sizes in the other waveguide structure are replaced, and each frequency component of plasmon is transmitted without being mixed by the difference in resonance frequency between metal fine particles of different sizes. (Claim 11).

  The waveguide element of the first means is a waveguide structure in which metal fine particles of uniform size are linearly arranged at equal intervals on a smooth substrate, and metal particles of different sizes are linearly arranged at equal intervals. By using the waveguide structure in multiple stages, the resonance effect depending on the size of the metal microparticles and the propagation speed of plasmon differing depending on the size of the metal microparticles can be used. It is possible to perform spatial distribution, branching, combining, spatial modulation, time modulation, and the like of optical signals.

The spatial modulation element of the second means is composed of the waveguide element of the first means, and makes use of the resonance effect depending on the size of the metal fine particles, thereby making the light incident on the input end of the waveguide element. The plasmon excited corresponding to the frequency of the light can be selectively coupled to the waveguide structure having metal particles of different sizes of the waveguide element to propagate the plasmon, and the optical frequency space in the nanometer region can be propagated. Distribution can be realized.

The time modulation element of the third means is composed of the waveguide element of the first means, and the propagation speed of the plasmon differs depending on the size of the metal fine particles, that is, between the metal fine particles by the electric dipole. By utilizing the fact that the strength of the coupling is different, a time delay is given to each frequency component of the plasmon, and time modulation for each frequency component can be realized.
The time modulation element of the fourth means is composed of the waveguide element of the first means, and the strength of the coupling between the metal fine particles by the electric dipole is adjusted by adjusting the interval of the metal fine particles. Thus, it is possible to change the propagation speed of the plasmon, give a time delay to each frequency component of the plasmon, and realize time modulation for each frequency component.

The spatial modulation element of the fifth means is composed of the waveguide elements of the first means, and each waveguide structure has a spatially expanded structure, so that each frequency component of plasmon is spatially distributed. It is distributed, and the effect as a prism of light (plasmon) in the nanometer region can be given.
The spatial modulation element of the sixth means is composed of the waveguide element of the first means, and each waveguide structure is arranged so as to be bent at a right angle, thereby deflecting each frequency component of the plasmon. Spatial distribution can be realized while maintaining the direction.

The waveguide element of the seventh means includes a waveguide structure in which metal fine particles having a uniform size are linearly arranged at equal intervals on a smooth substrate, and a waveguide structure by metal fine particles having the same size and different intervals. By using the resonance effect depending on the size of the metal fine particle and the difference in the propagation speed of the plasmon depending on the size of the metal fine particle, the spatial signal of the optical signal in the nanometer region can be obtained. Distribution, branching, synthesis, spatial modulation, time modulation, and the like can be performed.
Further, the spatial modulation element of the eighth means is composed of the waveguide element of the seventh means, and utilizes the fact that the propagation speed of plasmon differs depending on the distance between the metal fine particles, so Since the plasmon having one frequency is spatially deflected, signal control in the nanometer region can be performed.

  The waveguide element of the ninth means is a waveguide structure in which metal fine particles of uniform size are linearly arranged at equal intervals on a smooth substrate, and metal particles of different sizes are linearly arranged at equal intervals. By making use of the fact that the waveguide structure thus formed intersects with each other, the resonance effect depends on the size of the metal fine particles, and the propagation speed of plasmons varies depending on the size of the metal fine particles. It is possible to perform spatial distribution, branching, synthesis, spatial modulation, time modulation and the like of optical signals in the nanometer range.

The spatial modulation element of the tenth means is composed of the waveguide element of the ninth means, and transmits each frequency component of the plasmon without mixing due to the difference in the resonance frequency between the fine metal particles of different sizes. Therefore, the ease of arrangement (wiring) of the waveguide structure and high integration can be realized.
Further, the spatial modulation element of the eleventh means is constituted by the waveguide element of the ninth means, and at the point where the waveguide structure intersects, one metal fine particle in one waveguide structure is replaced with the other. Since it has a structure that is replaced with metal fine particles of different sizes in the waveguide structure, and because of the difference in resonance frequency between metal fine particles of different sizes, each frequency component of plasmons can be transmitted without being mixed, Ease of arrangement (wiring) of the waveguide structure and high integration can be realized. In addition, since all the metal fine particles are arranged on the square lattice, it is possible to realize ease of processing as well as ease of arrangement (wiring) of the waveguide structure and high integration.

  Hereinafter, the configuration, operation, and action of the present invention will be described in detail based on the illustrated embodiments.

[Example 1] (Examples of the first and second means)
A first embodiment of the present invention will be described with reference to FIGS. In this example, a waveguide structure in which metal fine particles having a uniform size are linearly arranged at equal intervals on a smooth substrate, and a waveguide structure in which metal fine particles of different sizes are linearly arranged at equal intervals. Is a plasmon spatial modulation element that uses a waveguide element having a multi-stage configuration as a spatial modulation element in the nanoscale region, and this plasmon spatial modulation element converts the incident light into a waveguide structure based on an array of metal fine particles It functions as an optical frequency distribution element that is selectively coupled to each other according to frequency components.

As shown in FIG. 1, the waveguide 3 of the waveguide element constituting the plasmon spatial modulation element of this embodiment is arranged as a metal fine particle array on the surface of a smooth substrate 1 made of a dielectric such as SiO ₂ or CaF _2. Is done. A structure in which a plurality of waveguide structures (metal particle array waveguides 3) in which metal fine particles 2 of uniform size are linearly arranged at equal intervals are arranged on the dielectric substrate 1 by changing the size of the metal fine particles. In the direction orthogonal to the arrangement direction of the metal fine particles having the same size, the metal fine particles of different sizes are linearly arranged at equal intervals. That is, in the embodiment of FIG. 1, a waveguide structure in which metal fine particles of uniform size are linearly arranged at equal intervals on a smooth dielectric substrate 1, and metal particles of different sizes are linear at equal intervals. The waveguide structure is arranged in multiple stages.

  When incident light is incident on one end side of the waveguide 3 having such a configuration via the optical fiber probe 4, light energy is introduced into the waveguide 3 by coupling of the incident light and plasmons in the metal fine particles. The reason why the dielectric substrate 1 is used as a smooth substrate is to avoid energy loss due to charge movement in the substrate and injection of charges into the metal fine particles 2.

  The shape of the metal fine particles 2 is assumed to be a cylindrical shape in FIG. 1 for ease of production, but may be a hemispherical shape or a cubic shape, or may be a structure embedded in a substrate. . Further, an ellipsoidal shape or the like may be used depending on the required optical frequency and polarization characteristics. Here, when the size of the metal fine particles 2 is about several tens of nanometers, the plasmon resonance frequency varies depending on the size and shape of the metal fine particles 2, so that the incident light as an input signal must be adjusted to that frequency. It is already known that the plasmon resonance frequency differs depending on the size and shape of the metal fine particles 2 as shown in the aforementioned Non-Patent Document 1.

  The material of the metal fine particles 2 may be a medium having a plasmon resonance frequency in the visible region of electromagnetic waves, and a medium in which gold (Au) fine particles, silver (Ag) fine particles, aluminum (Al) fine particles, etc. excite plasmons. Suitable as For example, an Au fine particle having a diameter of about 50 nm has a resonance wavelength at a light wavelength of about 500 nm.

  In order to inject light energy into the plasmon spatial modulation element shown in FIG. 1, a sharpened optical fiber probe 4 allows a single metal fine particle or a plurality of metal fine particles having different sizes near the tip of the probe from the diffraction limit. May be excited using near-field light localized in a minute region. In addition, if a silicon (Si) protruding probe or the like manufactured by an optical lithography technique is used, or a Si protruding probe or the like is manufactured on the same substrate, and the waveguide structure is partially irradiated with metal fine particles, Good.

  Next, a detailed configuration of the plasmon spatial modulation element shown in FIG. 1 will be described with reference to FIG. The plasmon spatial modulation element shown in FIG. 2 has a structure in which metal fine particles 2a, 2b, and 2c having large, medium, and small aligned sizes are linearly arranged at equal intervals on a smooth dielectric substrate 1. And a waveguide structure in which metal fine particles of the same size in the horizontal direction in the figure are linearly arranged at equal intervals, and a waveguide structure in which metal fine particles of different sizes in the vertical direction in the figure are linearly arranged at equal intervals. It is composed of waveguide elements having multiple stages of waveguide structures. When incident light is incident on the metal fine particles at the lateral incident end of the plasmon spatial modulation element and the plasmons are excited, the energy of the plasmons is successively transferred to the adjacent metal fine particles due to the electric dipole interaction between the metal fine particles. And form a propagation mode. As a result, in the example of FIG. 2, a propagation mode (longitudinal mode) in the horizontal direction in the figure having a wave number of (πn / d) in relation to the metal fine particle interval d is formed as a steady state. The arrows shown in FIG. 2 schematically represent the direction and size of the electric dipole and indicate the propagation of plasmons in the longitudinal mode. Unlike a macroscopic solid (bulk) or thin film, plasmons excited by metal fine particles can also have a propagation mode (transverse mode) in the vertical direction in the figure. In the application example shown in FIG. 2, it is assumed that the metal fine particles 2a, 2b, and 2c having three types of large, medium, and small sizes are linearly arranged at equal intervals and arranged in parallel. In this case, since the metal fine particles 2a, 2b, and 2c existing in the vertical direction have different sizes for each column, their resonance frequencies are different, and coupling between waveguide structures having different particle sizes is weak.

  Next, plasmon resonance energy (frequency) in metal fine particles having different sizes will be described with reference to FIG. FIG. 3 shows the Maxwell equation representing the spatio-temporal change of electromagnetic waves by a single finite difference time domain method (FDTD method), which is a numerical analysis method of differential equations (Au in FIG. 1). This is a result of calculating resonance energy using Fourier transform from a transient time response when a plane wave electromagnetic wave input is given to one metal fine particle 2) and the input is instantaneously disconnected from a steady state. It can be seen that the peak of the intensity spectrum changes toward the higher energy side as the size of the metal fine particle 2 becomes smaller. When the size of the metal fine particles reaches several nanometers, a quantum effect is generated and energy is discretized, and the calculation result of FIG. 3 becomes inaccurate, but the quantum effect does not appear at about 10 to several tens of nanometers. Along with this, there is a tendency to shift to the short wavelength side.

  The arrangement of the waveguides by the metal fine particle array is not particularly determined, but as shown in FIG. 2, from the bottom to the top, the metal fine particle (large) ) The reason why they are arranged in a row 2a is that they are arranged in the order of resonance energy for convenience, as can be seen from the intensity spectrum of FIG.

  There are various methods for producing metal fine particles as shown in FIGS. For example, a method of scraping a metal film deposited using an electron beam lithography apparatus, a method of using photolithography, a method of forming a deposit with a focused ion beam to form a metal film, a method of nanoimprinting pressing a mold, a water An anodic oxidation method for the reaction between the electrode and the electrode is conceivable.

  Next, the operation of the plasmon spatial modulation element shown in FIGS. 1 and 2 will be described with reference to FIGS. The light irradiated to the input end of the waveguide structure made of metal fine particles shown in FIG. 2 is divided into three frequency components in order to absorb light having a frequency depending on the size and excite plasmons as shown in FIG. The plasmons excited by the metal particles at the incident end cause energy transfer to the adjacent metal particles through coupling by the electric dipole, and form a propagation mode in the metal particle array of the same size. Since coupling between metal particles of different sizes cannot form a propagation mode due to resonance frequency mismatch, coupling between waveguides is weakened. In this way, energy propagation can be realized by spatially distributing plasmon frequency components.

[Example 2] (Examples of the first and third means)
A second embodiment of the present invention will be described with reference to FIG. This embodiment is a plasmon time modulation element using a waveguide element similar to that of the first embodiment as a time modulation element in the nanoscale region, and this plasmon time modulation element is a waveguide formed of metal fine particles having different sizes. It has a function as an optical delay element using the difference in plasmon propagation speed between structures.

  The basic configuration of the waveguide of the plasmon time modulation element of this embodiment is as described in the first embodiment. Here, the propagation speed of the plasmon in the waveguide structure by the metal fine particles 2 is determined by the strength of the electric dipole coupling, and the strength of the coupling by the electric dipole is determined by the size of the metal fine particles 2. Therefore, the larger the size of the metal fine particle, the faster the propagation speed of the plasmon, the delay time for each frequency component can be changed depending on the length of the waveguide structure by the metal fine particle, and the time modulation for each frequency component of the plasmon can be realized. .

[Example 3] (Examples of the first and fourth means)
A third embodiment of the present invention will be described with reference to FIG. The present embodiment is a plasmon time modulation element using a waveguide element similar to that of the first embodiment as a time modulation element in the nanoscale region, and this plasmon time modulation element is the same as the second embodiment. It has a function as an optical delay element using the difference in the propagation speed of plasmons between the waveguide structures of the metal fine particles. The basic configuration of this embodiment is substantially the same as that shown in FIGS. 1 and 2, but as shown in FIG. 4, the interval between the metal fine particles forming the waveguide structure differs depending on the size of the metal fine particles. That is, in the example of FIG. 4, the interval between the metal fine particles is narrowed in the order of the metal fine particles (large) 2a, the metal fine particles (medium) 2b, and the metal fine particles (small) 2c.

  The strength of the coupling by the electric dipole is proportional to the (−3) power of the interval d of the metal fine particles. If this is utilized, the propagation speed of a plasmon can be changed depending on the space | interval of a metal microparticle. Therefore, by adjusting the interval between the metal fine particles in each waveguide structure, the delay time of the plasmon can be changed, and the time modulation for each frequency component of the plasmon can be realized.

[Embodiment 4] (Embodiment of first and fifth means)
A fourth embodiment of the present invention will be described with reference to FIG. The plasmon spatial modulation element of this embodiment is a plasmon space in the nanometer region that spatially distributes the energy of each frequency component of incident light or plasmon by adjusting the spatial arrangement of the waveguide structure with metal fine particles. It has a function as a dispersive element.

  The configuration of the plasmon spatial modulation element of this embodiment is configured by an array of metal fine particles 2a, 2b, and 2c produced on a dielectric substrate 1, as in FIG. Here, in the example of FIGS. 1 and 2, metal fine particles 2a, 2b, and 2c having different sizes are arranged in parallel, whereas in this embodiment, as shown in FIG. 5, large and small sizes are arranged. The waveguide structures 3a and 3c formed by the metal fine particles 2a and 2c having the same thickness are arranged at an angle θ with respect to the waveguide structure 3b of the central metal fine particle (medium) 2b. In this case, in the metal fine particle array having an angle with respect to the polarization of the incident light, both vertical and horizontal modes are formed and propagated along the waveguide structures 3a and 3c by the metal fine particles 2a and 2c. As a result, the plasmon spatial modulation element of this embodiment converts light in the nanometer region into plasmons, and generates spatial modulation depending on the arrangement of the metal fine particle arrays for each frequency component. It functions as an element.

[Embodiment 5] (Embodiments of the first and sixth means)
A fifth embodiment of the present invention will be described with reference to FIG. As in the fourth embodiment, the plasmon spatial modulation element of the present embodiment spatially converts the energy of each frequency component of incident light or plasmons by adjusting the spatial arrangement of the waveguide structure of metal fine particles. It functions as a plasmon space distribution element in the nanometer region for distribution.

  The configuration of the plasmon spatial modulation element of this embodiment is such that the large, medium, and small sized metal fine particles 2a, 2b, and 2c as described in the fourth embodiment are formed in an L-shaped corner as shown in FIG. It is arranged so as to have In this case, in the embodiment shown in FIG. 6, the light guided by the metal fine particles 2a and 2c having the upper and lower large and small sizes with respect to the light incident on the waveguide structure 3b by the middle-sized metal fine particle 2b in the center is polarized. In the waveguide structures 3a and 3b, the transverse mode is first excited, converted into the longitudinal mode through a corner that is bent at a right angle, and propagates. The arrows in the figure schematically show the direction and size of the electric dipole as in FIG. Therefore, at the output end, outputs of a plurality of frequency components whose plasmon deflection directions are aligned in the longitudinal mode can be obtained, and each frequency component of the plasmons can be spatially distributed while maintaining the polarization state of the incident light. .

[Embodiment 6] (Embodiments of seventh and eighth means)
A sixth embodiment of the present invention will be described with reference to FIG. As in the third embodiment, the plasmon spatial modulation element of this embodiment has a function as a plasmon spatial dispersion element that utilizes the difference in the propagation speed of plasmons between the waveguide structures of metal fine particles. This plasmon spatial modulation element includes a waveguide structure in which metal fine particles 2 of uniform size are linearly arranged on a smooth substrate 1 and a metal fine particle 2 having the same size and different intervals. Are made up of waveguide elements having multiple stages.

  As shown in FIG. 7, in this embodiment, all the metal fine particles 2 arranged on the dielectric substrate 1 have the same size. However, the interval between the metal fine particles is different for each row. In this case, the propagation speed of the plasmon in the horizontal direction in FIG. 7 is such that the strength of the coupling by the electric dipole between the metal fine particles is proportional to the (−3) power of the particle spacing d. It changes according to the arrangement period of the fine particles. The arrows in the figure schematically represent the difference in the propagation speed of plasmons corresponding to the arrangement period of the metal fine particle arrays. As a result, the output of the plasmon propagating through the element is spatially bent, and the element functions as a spatial dispersion element in the nanometer region.

[Embodiment 7] (Embodiments of ninth and tenth means)
A seventh embodiment of the present invention will be described with reference to FIG. The plasmon spatial modulation element of the present embodiment has a function as a plasmon waveguide with respect to spatially distributed plasmon frequency components. In this plasmon spatial modulation element, a waveguide structure in which metal fine particles of uniform size are linearly arranged at equal intervals on a smooth substrate 1 and metal particles of different sizes are linearly arranged at equal intervals. The waveguide structure is composed of waveguide elements having structures that cross each other.

  The configuration of the metal fine particles in the plasmon spatial modulation element of the present embodiment is arranged so that one of the two waveguides by the large and small metal fine particles 2a and 2c intersects the other as shown in FIG. The frequency component of the plasmon depending on the size of the metal fine particles 2a and 2c at the incident end selectively propagates through the waveguide structure formed by the metal fine particles 2a and 2c. Here, the waveguides that propagate each frequency component are independent from each other, and the waveguide structure can be bent spatially through the conversion between the longitudinal mode and the transverse mode of the plasmon by the arrangement of the metal fine particles 2a and 2c. Since it is possible, it is possible to take a waveguide structure that intersects spatially. The optical device and the optical integrated circuit in the nanometer region having the plasmon waveguide thus configured can improve the problem of wiring on the substrate and the difficulty of integration.

[Embodiment 8] (Embodiments of ninth and eleventh means)
An eighth embodiment of the present invention will be described with reference to FIG. The plasmon spatial modulation element of the present embodiment has a function as a plasmon waveguide with respect to spatially distributed plasmon frequency components. As in the seventh embodiment, this plasmon spatial modulation element has a waveguide structure in which metal fine particles having a uniform size are linearly arranged at equal intervals on a smooth substrate 1, and metal fine particles of different sizes. The waveguide structures linearly arranged at equal intervals are composed of waveguide elements having a structure that intersects each other. At the point where the waveguide structures intersect, one waveguide structure in one waveguide structure The metal fine particles have a structure in which metal fine particles having different sizes in the other waveguide structure are replaced.

  The arrangement configuration of the metal fine particles in the plasmon spatial modulation element of the present embodiment is arranged so that one of the two waveguides by the large and small metal fine particles 2a and 2c intersects the other as shown in FIG. . Here, the metal fine particles 2a in one waveguide structure are replaced with metal fine particles 2c having the size of the other waveguide structure. The incident light is converted into plasmons having a frequency component that resonates with the size of the metal fine particles 2a and 2b constituting the waveguide structure, and propagates through the waveguide structure. Here, the periodicity of the metal fine particles is not disturbed even in the waveguide structure in which the metal fine particles are replaced, and plasmons can propagate through the waveguide of the metal fine particles. Therefore, it is possible to take a waveguide structure that intersects spatially, and all the metal fine particles are arranged in a square lattice, so that in the nanometer region having the plasmon waveguide thus configured. The optical device and the optical integrated circuit can improve the wiring problem on the substrate and the difficulty of integration.

As described above, the configuration and operation of the present invention have been described based on the embodiments. However, in the plasmon spatial modulation element (waveguide element) according to the first and second means, locally introduced light energy is converted into a plurality of frequencies. Since it is distributed to plasmons of components and extracted for each frequency component via a waveguide structure made of metal fine particles, it can be used for an optical information processing technique in the nanometer region using optical signals multiplexed in frequency.
In the plasmon time modulation element (waveguide element) according to the first, third, and fourth means, each frequency component of plasmon is utilized by utilizing the difference in propagation velocity depending on the size of metal particles and the distance between particles. On the other hand, since a time delay is given, it can be used for optical information processing technology in the nanometer region.
Furthermore, in the plasmon spatial modulation element (waveguide element) according to the first, fifth, and sixth means, the plasmon is arranged at an arbitrary angle, position, and deflection direction with respect to each frequency component by the spatial arrangement of the metal fine particles. Since it is distributed and distributed, it can be used for optical information processing technology such as input / output elements in an optical integrated circuit in the nanometer region.

In the plasmon spatial modulation element (waveguide element) according to the seventh and eighth means, the plasmon propagation direction is changed in the nanometer region by utilizing the difference in the propagation speed of the plasmon depending on the interval between the metal fine particles. Therefore, it can be used for nano-optical device technology such as signal control in the nanometer region and interference type elements.
In addition, in the plasmon spatial modulation element (waveguide element) according to the ninth, tenth, and eleventh means, the resonance effect depending on the size of the metal fine particles and the periodicity of the arrangement are utilized to enable the intersection of the waveguides. Therefore, it can be used for wiring technology and miniaturization technology of nano-optical devices.

1 is a schematic perspective view of a plasmon spatial modulation element showing one embodiment of the present invention. It is a principal part top view of the plasmon spatial modulation element shown in FIG. It is a figure which shows the relationship between the energy of the light which injects into the plasmon spatial modulation element shown in FIG.1, 2, and the intensity | strength of the excited plasmon. It is a principal part top view of the plasmon time modulation element which shows another Example of this invention. It is a principal part top view of the plasmon spatial modulation element which shows another Example of this invention. It is a principal part top view of the plasmon spatial modulation element which shows another Example of this invention. It is a principal part top view of the plasmon spatial modulation element which shows another Example of this invention. It is a principal part top view of the plasmon spatial modulation element which shows another Example of this invention. It is a principal part top view of the plasmon spatial modulation element which shows another Example of this invention. It is a top view of the waveguide which shows an example of a prior art. It is a figure which shows another example of a prior art, and is a figure which shows the light intensity distribution by the near field optical microscope of the waveguide part from the electron microscope image of the plasmon collector, and its condensing point. It is a perspective view of the optical element which shows another example of a prior art. It is sectional drawing of the near-field optical head which shows another example of a prior art.

Explanation of symbols

1: Smooth substrate (dielectric substrate)
2: Metal fine particles 2a: Metal fine particles (large)
2b: Metal fine particles (medium)
2c: Metal fine particles (small)
3: Metal fine particle array waveguide 3a, 3b, 3c: Waveguide structure (waveguide)
4: Optical fiber probe

Claims (11)

A waveguide element that propagates plasmons, in which metal particles of uniform size are linearly arranged at equal intervals on a smooth substrate, and metal particles of different sizes are linearly arranged at equal intervals. A waveguide element having a plurality of arranged waveguide structures. Claim 1 is a spatial modulation element composed of a waveguide element, wherein the plasmon excited in response to the frequency of the light incident on the input end of the waveguide element, the different sizes of said waveguide element selectively coupled to the waveguide structure by metal fine particles, the spatial modulation element, characterized in that propagate the plasmon.   A time modulation element comprising the waveguide element according to claim 1, wherein in the waveguide structure, each frequency component of the plasmon is utilized by utilizing a propagation speed of plasmon depending on a size of the metal fine particle. A time modulation element characterized in that a time delay is given to.   A time modulation element comprising the waveguide element according to claim 1, wherein in the waveguide structure, each frequency component of the plasmon is utilized by utilizing a propagation speed of plasmon depending on a distance between metal fine particles. A time modulation element characterized in that a time delay is given to.   A spatial modulation element comprising the waveguide element according to claim 1, wherein each of the frequency components of the plasmon is spatially branched by having a structure in which each waveguide structure is spatially expanded. Spatial modulation element.   A spatial modulation element comprising the waveguide element according to claim 1, wherein each waveguide structure is arranged so as to be bent at a right angle, thereby maintaining a deflection direction in each frequency component of the plasmon, and spatially A spatial modulation element that is branched. A waveguide element that propagates plasmons, which is a waveguide structure in which metal particles of uniform size are linearly arranged on a smooth substrate at equal intervals, and a waveguide composed of metal particles having the same size and different intervals A waveguide element characterized by having a multistage structure.   A spatial modulation element comprising the waveguide element according to claim 7, wherein the plasmon is deflected by utilizing the fact that the propagation speed of the plasmon varies depending on the distance between the metal fine particles. . A waveguide element that propagates plasmons, in which metal particles of uniform size are linearly arranged at equal intervals on a smooth substrate, and metal particles of different sizes are linearly arranged at equal intervals. A waveguide element having a structure in which the arranged waveguide structures cross each other.   A spatial modulation element comprising the waveguide element according to claim 9, wherein each frequency component of plasmon is transmitted without being mixed due to a difference in resonance frequency between metal particles of different sizes. element.   10. A spatial modulation element comprising the waveguide element according to claim 9, wherein one metal fine particle in one waveguide structure is a metal having a different size in the other waveguide structure at a point where the waveguide structure intersects. A spatial modulation element having a structure replaced with fine particles, and transmitting each frequency component of plasmon without mixing due to a difference in resonance frequency between fine metal particles of different sizes.

Images