JP5087488B2 - Near-field optical waveguide bonding device - Google Patents

Description

  The present invention relates to a near-field optical waveguide joining apparatus for joining a near-field optical waveguide and a propagation optical waveguide.

According to the semiconductor roadmap ITRS, it has been said that LSIs have been advancing from around 2015 due to problems such as leakage current and information delay in the circuit, and a near-field system has been proposed as one of information control systems that change to that. An optical system has wavelength multiplexing, light speed information transmission, and high-speed logic operation, but is said to be unsuitable for integration because of the diffraction limit. However, in recent years, the near field light having no diffraction limit has been proposed, and this problem may be solved.

Optical microscopes with sub-micron resolution-Near-field optical microscopes increase the resolution with optical fiber processed probes. The opening diameter of the output end of the optical fiber is made smaller, and the portions other than the opening are coated with metal. In this case, the conversion efficiency from propagating light to near-field light is as shown in the following table, for example.

However, when considering the system efficiency, there is a practical problem with an aperture diameter of 100 nm and 10 ⁻⁴ . Higher coupling efficiency in the construction of near-field light systems and LD (Laser Diode), LED (Light Emitting Diode) as the light source in SoC (System On Chip) optical wiring, or fiber or propagation optical waveguide from outside the system Is required.

In general, it is known that the near-field light has a stronger interaction when using metal-so-called plasmons. One-dimensional metal fine wires and one-dimensional submicron dot (or cylinder) arrays are known for plasmon waveguide. In the one-dimensional metal wiring, surface plasmon polariton generated on the metal surface is guided. That is, energy is guided only on the surface. In the one-dimensional sub-micron array method, plasmons generated on the surface guide energy, but the space between the spheres is also an energy transmission space. Patent Document 1 shows that plasmons are guided in a system in which gold nanoparticles of 4 nm are dispersed.
JP 2007-148289 A

  The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a near-field optical waveguide junction device capable of increasing the coupling efficiency between propagating light and near-field light as much as possible. And

  A near-field optical waveguide joining device according to a first aspect of the present invention joins a propagation optical waveguide through which light propagates and a near-field optical waveguide of a metal nanoparticle dispersed film in which metal nanoparticles are dispersed in a dielectric. A junction part that is a metal nanoparticle-dispersed film of the same material as the near-field optical waveguide, and the difference between the real part of the refractive index of the propagation optical waveguide and the real part of the effective refractive index of the joint part is It is 0 or more and 0.5 or less.

  The near-field optical waveguide joining device according to the second aspect of the present invention includes a propagation optical waveguide through which light propagates and a near-field optical waveguide of a metal nanoparticle-dispersed film in which metal nanoparticles are dispersed in a dielectric. It has a junction part which is metal nanoparticle dispersion film of the same material as the near field optical waveguide, and the real part of the effective refractive index of the junction part is 1.0 or more and 1.2 or less And

  According to the present invention, it is possible to provide a near-field optical waveguide bonding apparatus capable of increasing the coupling efficiency between propagating light and near-field light as much as possible.

  Before describing the embodiments of the present invention, the background to the present invention and the outline of the present invention will be described.

  As described above, it is generally known that the near-field light has a stronger interaction when using a metal-based so-called plasmon. One-dimensional metal fine wires and one-dimensional submicron dot (or cylinder) arrays are known for plasmon waveguide. In the one-dimensional metal wiring, surface plasmon polariton generated on the metal surface is guided. That is, energy is guided only on the surface. In the one-dimensional sub-micron array method, plasmons generated on the surface guide energy, but the space between the spheres is also an energy transmission space.

  Although propagating light has a diffraction limit, energy once changed to plasmon does not cause a diffraction limit. Therefore, the present inventors considered that it is effective to reduce the waveguide width after the energy is transferred to plasmon. And when it implement | achieved, it thought that it was important to use a dispersion system as described in patent document 1. FIG. That is, in a waveguide having a width equal to or greater than the diffraction limit, the propagation light is converted into plasmon, and then the size of the plasmon waveguide is reduced. The plasmon waveguide, that is, the near-field waveguide is a system as described in Patent Document 1. It is important to use

  At this time, reflection may occur at the boundary end face between the propagation optical waveguide and the plasmon waveguide. For this reason, it is important to reduce this reflectance. The refractive index of a metal is generally less than 1 in the visible and near infrared, and the imaginary part (extinction coefficient) is large. In such cases, energy does not enter the material and is reflected. In metal, energy is transferred only to the surface. At this time, it is a condition that energy conservation and wave number conservation (momentum conservation) are established. However, in general, these two conservation laws are unlikely to be realized because the dispersion relation between propagating light and plasmon is different, and the conversion efficiency is extremely low because the cross-sectional areas of energy propagation are greatly different.

As one countermeasure against this problem, it has been found that a metal nanoparticle dispersion system in which metal nanoparticles are dispersed in a dielectric may be used. This makes it possible to increase the conversion efficiency because this metal nanoparticle dispersion system can make the waveguide cross-sectional area the same as that of the propagation optical waveguide. Further, as another countermeasure, it has been found that an effective refractive index is defined in a metal nanoparticle dispersion system and this effective refractive index satisfies a certain condition. This effective refractive index _ne is defined as follows. The volume of material A Va, the complex refractive index _{n a,} volume _{V b} of the material B, and the complex refractive index and _{n b,}
Can be defined as In the metal nanoparticle dispersion system, this effective refractive index _ne is a weighted average of the complex refractive index of metal and the complex refractive index of a dielectric that is a matrix, weighted by volume. The present inventors have found that the reflection can be reduced by matching the real part or the real part and the imaginary part at the end face where the propagation optical waveguide and the plasmon waveguide are in contact. This is common when considering reflection at a dielectric waveguide or a heterogeneous dielectric interface, but is not effective when one is a metal. For example, an antireflection film cannot be attached to the surface of a metal. This is because the metal nanoparticle dispersion system is a material system in which plasmons are guided, but the overall system is a general dielectric material. It depends on being able to realize a complex refractive index in which a similar real part is larger than 1 and an imaginary part is not so large.

In addition, as will be described in the embodiments described below, the present inventors have found that the energy from the propagation optical waveguide to the plasmon waveguide increases as the real part of the complex refractive index of the metal nanoparticle dispersion system is 1 or more and closer to 1. It was experimentally found that the conversion efficiency is increased.

Furthermore, it has been confirmed that the near-field optical waveguide bonding apparatus according to an embodiment of the present invention is effective for preventing reflection by a subwavelength structure that has become popular recently.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
A near-field optical waveguide bonding apparatus according to a first embodiment of the present invention is shown in FIG. FIG. 1 is a plan view of the near-field optical waveguide bonding apparatus according to the present embodiment. In the near-field optical waveguide bonding apparatus of the present embodiment, the propagation optical waveguide 20 and metal nanoparticles having a size (diameter) on the order of nanometer (for example, silver particles having a diameter of 10 nm) are in a dielectric (for example, SiO ₂ ). A joint 10 for connecting a near-field optical waveguide (plasmon waveguide) 30 made of a metal nanoparticle-dispersed film. The joint 10 is made of a metal nanoparticle-dispersed film made of the same material as that of the plasmon waveguide 30, and has the same size (diameter (eg, 1 μm) or cross-sectional area as that of the propagation optical waveguide 20 at the connection portion with the propagation optical waveguide 20. ) And has the same size (diameter (for example, 100 nm) or cross-sectional area) as the plasmon waveguide 30 at the connection portion with the plasmon waveguide 30, and is connected to the plasmon waveguide 30 from the connection portion with the propagation optical waveguide 20. The size is smoothly reduced to the connecting portion.

  In the bonding apparatus of the present embodiment configured as described above, the effective refractive index of the bonding portion 10 is changed by changing the refractive index value of the dielectric (matrix) in which the metal nanoparticles (silver nanoparticles) are dispersed. At the same time, the real part of the refractive index of the propagation optical waveguide 20 was changed, and the difference in coupling efficiency (conversion efficiency) was examined by simulation. The result is shown in FIG. In FIG. 2, the real part of the refractive index of the propagation optical waveguide 20 is 1, 1.2, 1.5, 1.053, 1.183, 1.283, 1.383, 1.5, 1.183, When changed to 1.283 and 1.118, the real part of the effective refractive index of the joint 10 is 1, 1, 1, 1.053, 1.053, 1.053, 1.053, 1.053, 1 .183, 1.183, and 1.118, the difference Δn at that time, and the coupling efficiency obtained by simulation are shown. A graph in which Δn is taken on the horizontal axis and the coupling efficiency is taken on the vertical axis is shown in FIG. In the graph shown in FIG. 3, the values of the real part of the refractive index of the joint 10 are plotted with parameters of 1, 1.053, 1.118, and 1.183. FIG. 4 is a graph in which the real part of the effective refractive index of the joint 10 is plotted on the horizontal axis and the data when the coupling efficiency is taken on the vertical axis. In this case, the real part of the refractive index of the propagation optical waveguide 20 has the same value as the real part of the effective refractive index of the joint 10.

  As can be seen from FIGS. 2 to 4, even if the real part of the effective refractive index of the joint 10 changes, the difference between the real part of the refractive index of the propagation optical waveguide 20 and the real part of the effective refractive index of the joint 10. The smaller Δn, the higher the conversion efficiency (that is, the conversion efficiency from propagating light to plasmon). Further, if the difference Δn is 0.5 or less, the conversion efficiency is 0.057 or more, which is two orders of magnitude larger than the case of using a fiber probe as in the conventional case.

  If there is no difference between the real part of the effective refractive index of the joint 10 and the real part of the refractive index of the propagation optical waveguide 20, the effective refractive index of the joint 10 is close to 1, as can be seen from FIG. However, the conversion efficiency is high. From this simulation, it can be seen that if the real part of the effective refractive index of the joint 10 is 1.0 or more and 1.2 or less, higher conversion efficiency can be obtained than in the conventional case.

  As described above, according to the present embodiment, the conversion efficiency (coupling efficiency) from propagating light to plasmon (near-field light) can be made as high as possible.

(Second Embodiment)
Next, a near-field optical waveguide joining device according to a second embodiment of the present invention is shown in FIG. FIG. 5 is a plan view of the near-field optical waveguide bonding apparatus according to the present embodiment. The near-field optical waveguide bonding apparatus of the present embodiment uses cylindrical silver nanoparticles 12 having a diameter of 30 nm as the metal nanoparticles of the bonding portion 10 in the near-field optical waveguide bonding apparatus of the first embodiment. The joint 10 is manufactured by using a focused ion beam (FIB) to process silver nanoparticles each having a diameter of 30 nm into a cylindrical shape, and surrounding TEOS (Tetra) so as to surround the silver nanoparticles 12. An organic SiO ₂ film (not shown) prepared by hydrolysis of (Ethyl Ortho Silicate) was applied. The thickness of this organic SiO ₂ film was about 500 nm. The width of the propagation optical waveguide 20 is 1 μm, and the width of the plasmon waveguide 30 is 100 nm. In addition, the plasmon waveguide 30 was comprised from the same material as the junction part 10 similarly to 1st Embodiment. In FIG. 5, the cylindrical silver nanoparticles 12 are arranged so that the axial direction of the cylinder is perpendicular to the paper surface.

  The joint 10 thus configured is observed with a differential interference near-field optical microscope (hereinafter also referred to as a SNOM (Scanning Near-field Optical Microscope)) that combines a near-field microscope and a differential interferometer. The effective refractive index of was measured. The dopant contained at the time of TEOS application is changed, some of them are measured by differential interference SNOM, the one having an effective refractive index of the junction 10 of about 1.05 is selected, and the real part of the refractive index of the propagation optical waveguide 20 What was changed was joined. In this embodiment, the difference Δn between the real part of the refractive index of the propagation optical waveguide 20 and the real part of the effective refractive index of the joint 10 is set to 0.05, 0.45, and 0.53. Ring efficiency (conversion efficiency from propagating light to plasmon) was measured. The wavelength of light used for this measurement is 1 μm. The result of this measurement is shown in FIG. When the difference Δn = 0.05, the light was incident on the joint from the air without using the propagation optical waveguide 20 and measured.

As can be seen from FIG. 6, if 0.53 hereinafter difference [Delta] n, the coupling efficiency becomes 6.0 × 10 ^-2 or more, than the conventional case, it is understood that it is possible to obtain a higher conversion efficiency .

  As described above, according to the present embodiment, the conversion efficiency (coupling efficiency) from propagating light to plasmon (near-field light) can be made as high as possible.

(Modification)
Next, a near-field optical waveguide bonding apparatus according to a modification of the present embodiment is shown in FIG. In the near-field optical waveguide joining device according to this modification, the propagation optical waveguide 20 has a shape in which the cross-sectional area becomes smaller toward the tip, for example, a triangular portion 20a having a sharp tip in a planar shape. The pointed tip of the portion 20 a is configured to be inserted into the joint portion 10. That is, the joint surface between the propagation optical waveguide 20 and the joint portion 10 is the surface of the tip of the triangular portion 20a, and the area of the joint surface can be increased by sharpening the sharpness of the triangular portion 20a. The joint 10 is formed in the same manner as the method for manufacturing the joint 10 described in the second embodiment, and has a configuration in which cylindrical silver nanoparticles having a diameter of 30 nm are dispersed in the organic SiO ₂ film. doing.

  Also in this modification, as in the first embodiment, if the difference Δn between the real part of the refractive index of the propagation optical waveguide 20 and the real part of the effective refractive index of the joint 10 in contact with the propagation optical waveguide 20 is small. As high a conversion efficiency as possible can be obtained. Further, the closer the real part of the effective refractive index of the joint 10 is to 1, the higher the conversion efficiency can be obtained.

(Third embodiment)
Next, a near-field optical waveguide joining device according to a third embodiment of the present invention will be described. The near-field optical waveguide bonding apparatus according to the present embodiment is different from the near-field optical waveguide bonding apparatus according to the second embodiment in the method for manufacturing the bonding portion 10 and the plasmon waveguide 30 made of a silver nanoparticle-dispersed film. For the junction 10 and the plasmon waveguide 30 according to the present embodiment, a silver nanoparticle-dispersed film in which silver nanoparticles are dispersed in organic SiO ₂ is produced by a silver reduction method using Sn seeds. As a result of measuring the produced silver nanoparticle dispersion film using a TEM (Transmission Electron Microscope), the diameter of the silver nanoparticles was 10 nm on average. As a result of measurement with a differential interference near-field optical microscope, there was a variation in density and a difference in effective refractive index. For this reason, a member having an effective refractive index of 1.183 was selected, and the junction 10 and the plasmon waveguide 30 having the structure as in the second embodiment shown in FIG. 5 were produced by ion milling. The joint 10 was joined to the fiber type propagation optical waveguide 20 and the conversion efficiency was measured. In this measurement, the difference Δn between the real part of the refractive index of the propagation optical waveguide 20 and the real part of the effective refractive index of the joint 10 is set to 0.05, 0.45, and 0.53. Efficiency (conversion efficiency from propagating light to plasmon) was measured. The wavelength of light used for this measurement is 1 μm. The result of this measurement is shown in FIG. When the difference Δn = 0.05, the light was incident on the joint 10 from the air without using the propagation optical waveguide 20 and measured.

As can be seen from FIG. 8, if 0.53 hereinafter difference [Delta] n, the coupling efficiency becomes 6.4 × 10 ^-2 or more, than the conventional case, it is understood that it is possible to obtain a higher conversion efficiency .

  As described above, according to the present embodiment, the conversion efficiency (coupling efficiency) from propagating light to plasmon (near-field light) can be made as high as possible.

(Fourth embodiment)
Next, a near-field optical waveguide joining device according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 9 is a partial plan view of the near-field optical waveguide joining device of this embodiment. The near-field optical waveguide bonding apparatus of this embodiment is the same as the near-field optical waveguide bonding apparatus of the second embodiment shown in FIG. The configuration is thinned (see FIG. 9). As the thinning method, the closer to the propagation optical waveguide 20, the more thinning was performed and a sub-wavelength structure was configured. Also in this embodiment, the difference Δn between the real part of the refractive index of the propagation optical waveguide 20 and the real part of the refractive index in the region of the joint 10 adjacent to the propagation optical waveguide 20 is the first embodiment. As described in the embodiment, it was set to 1.183 or less.

  It is well known that the subwavelength structure is effective for antireflection (for example, H. Toyota, K. Takahara. M. Okamoto, T. Yotsuya, and H. Kikuta, Jpn J. Appl. Phys. 40). L747 (2001)). In this embodiment, since it has a sub-wavelength structure, reflection of propagating light at the joint surface between the propagation optical waveguide 20 and the joint 10 is suppressed, and the conversion efficiency is about 3 compared to the second embodiment. % Increase.

  Similarly to the second embodiment, this embodiment can also increase the conversion efficiency (coupling efficiency) from propagating light to plasmon (near-field light) as much as possible.

(Fifth embodiment)
Next, a near-field optical waveguide junction device according to a fifth embodiment of the present invention is described with reference to FIGS. FIG. 10A is a schematic diagram showing the metal nanoparticles 13 used in the metal nanoparticle dispersion film according to the near-field optical waveguide bonding device of the present embodiment, and FIG. 10B is shown in FIG. It is a schematic diagram which shows the metal nanoparticle dispersion film | membrane with which the metal nanoparticle 13 was arranged.

  The near-field optical waveguide bonding apparatus according to the present embodiment is different from the near-field optical waveguide bonding apparatus according to the second embodiment in the method for manufacturing the bonding portion 10 and the plasmon waveguide 30 made of the metal nanoparticle-dispersed film. As shown in FIG. 10A, the junction 10 and the plasmon waveguide 30 according to the present embodiment have a configuration in which core-shell gold nanoparticles 13 having dodecanethiol as a ligand (organic shell) are formed by a dip method. It has become.

  As a result of measuring the produced gold nanoparticle dispersed film using a TEM (Transmission Electron Microscope), the diameter of the gold nanoparticle was about 3 nm. As a result of measurement with a differential interference near-field optical microscope, there was a variation in density and a difference in effective refractive index. For this reason, a member having an effective refractive index of 1.183 was selected, and the junction 10 and the plasmon waveguide 30 having the structure as in the second embodiment shown in FIG. 5 were produced by ion milling. The joint 10 was joined to the fiber type propagation optical waveguide 20 and the conversion efficiency was measured. In this measurement, the difference Δn between the real part of the refractive index of the propagation optical waveguide 20 and the real part of the effective refractive index of the joint 10 is set to 0.05, 0.45, and 0.53. Efficiency (conversion efficiency from propagating light to plasmon) was measured. The wavelength of light used for this measurement is 1 μm. The result of this measurement is shown in FIG. When the difference Δn = 0.05, the light was incident on the joint 10 from the air without using the propagation optical waveguide 20 and measured.

As can be seen from Figure 11, if 0.53 hereinafter difference Δn is, the coupling efficiency becomes 0.05 or more, than the conventional case, it is found that it is possible to obtain a higher conversion efficiency.

  As described above, according to the present embodiment, the conversion efficiency (coupling efficiency) from propagating light to plasmon (near-field light) can be made as high as possible.

  In this embodiment, gold nanoparticles are used, but silver nanoparticles or Al nanoparticles may be used.

  Moreover, in this embodiment, as shown in 4th Embodiment, it is good also as a structure which thinned out the metal nanoparticle 12 of the area | region which adjoins the propagation optical waveguide 20 of the junction part 10. FIG.

(Sixth embodiment)
Next, a near-field optical waveguide junction device according to a sixth embodiment of the present invention will be described with reference to FIG.

The following finite difference time domain (FDTD) simulation calculation was performed. First, as shown in FIG. 12, a sample having a structure in which five waveguides A, B, C, D, and E were connected to the end face of the silver nanoparticle dispersion film was designed. The refractive index of the matrix (SiO ₂ ) of the silver nanoparticle dispersion film was 1.2, and the volume ratio of the silver nanoparticles was 20 Vol%. The volume weighted average (real part) of the complex refractive index at a wavelength of 1 μm is about 1.0. On the other hand, in the calculation by Maxwell-Garnett, the real part of the effective refractive index is about 1.64. The refractive indexes of the connected waveguides A, B, C, D, and E were 1.0, 1.2, 1.4, 1.6, and 1.8, respectively, and the other portions were platinum. That is, the refractive indexes of the waveguides A, B, C, D, and E are increased from 1.0 to 0.2.

  A pulse having a wavelength of 1 μm was simultaneously incident on each of the waveguides A, B, C, D, and E on the sample thus configured. In the propagation optical waveguide, the larger the refractive index, the slower the propagation speed, and the time to reach the boundary line with the silver nanoparticle dispersed film is delayed. Since the silver nanoparticle-dispersed films have the same characteristics, the propagation speed is the same. In addition, since the imaginary part of the complex refractive index is not zero in the silver nanoparticle-dispersed film, the intensity is absorbed and becomes weak as the light propagates. FIG. 12 is a diagram showing the photoelectric magnetic field intensity at a certain moment after the light is guided. In FIG. 12, the higher the light intensity, the darker the density. In FIG. 12, the electromagnetic field intensity of the light incident from the waveguide A reaches the silver nanoparticle-dispersed film region quickly and travels a longer distance accordingly. On the other hand, from the waveguide B to the waveguide E, the time to reach the silver nanoparticle dispersion film region is gradually delayed, so the distance traveled in the silver nanoparticle dispersion film is short. In FIG. 12, the light pulse that passed through the waveguide A has a stronger intensity than the light pulse that passed through the waveguide E, although the traveling distance is long. That is, it is shown that the coupling efficiency decreases in the order of the waveguide A, the waveguide B, the waveguide C, the waveguide D, and the waveguide E.

  If Maxwell-Garnett's calculation of the effective refractive index for the silver nanoparticle-dispersed film is correct, the difference Δn between the real part of the refractive index of the waveguide and the real part of the refractive index of the silver nanoparticle-dispersed film (1.63) is the most. A waveguide that becomes small and has high coupling efficiency should be waveguide D. However, the measurement result shown in FIG. 12 shows that the coupling efficiency of the waveguide A is high. Therefore, the measurement results in FIG. 12 indicate that it is better to analyze using the effective refractive index described in each embodiment of the present invention.

  As described above, according to the present embodiment, the conversion efficiency (coupling efficiency) from propagating light to plasmon (near-field light) can be made as high as possible.

  As described above, according to each embodiment of the present invention, there is provided a near-field optical waveguide junction device capable of increasing the coupling efficiency (conversion efficiency) between propagating light and near-field light as much as possible. can do.

  In addition, in 1st thru | or 5th and 7th embodiment, although the silver nanoparticle was used as a metal nanoparticle, the same effect can be acquired even if it uses a gold nanoparticle or an Al nanoparticle.

The top view which shows the near-field optical waveguide joining apparatus of 1st Embodiment. The figure which shows the simulation result of the near-field optical waveguide joining apparatus by 1st Embodiment. The figure which plotted the simulation result shown in FIG. The figure which plotted the simulation result shown in FIG. The top view which shows the near-field optical waveguide joining apparatus of 2nd Embodiment. The figure which shows the conversion efficiency of the near-field optical waveguide joining apparatus of 2nd Embodiment. The top view which shows the near-field optical waveguide joining apparatus by the modification of 2nd Embodiment. The figure which shows the conversion efficiency of the near-field optical waveguide joining apparatus of 3rd Embodiment. The top view which shows the near-field optical waveguide joining apparatus of 4th Embodiment. The figure which shows the structure of the metal nanoparticle film | membrane which concerns on 5th Embodiment. The figure which shows the conversion efficiency of the near-field optical waveguide joining apparatus of 5th Embodiment. The figure explaining the near-field optical waveguide joining apparatus of 6th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Junction part 12 Cylindrical metal nanoparticle 13 Core-shell type metal nanoparticle 20 Propagation optical waveguide 30 Plasmon waveguide (near field waveguide)

Claims (7)

A propagation optical waveguide through which light propagates;
A near-field optical waveguide in which metal nanoparticles are dispersed in a dielectric;
The propagation optical waveguide and the near-field optical waveguide are joined together, a portion having the same cross section as the propagation optical waveguide at the joint surface with the propagation optical waveguide, and the near-field light is converted from propagation light to near-field light. A portion having a cross-sectional area that decreases from a cross-section in a portion that propagates and converts to the near-field light toward the near-field optical waveguide, and a joint portion of the same material as the near-field optical waveguide;
The provided, and the real part of the refractive index of the propagating optical waveguide, the difference between the real part of the effective refractive index of the junction, the near-field optical waveguide junction and wherein the at 0 to 0.5. A propagation optical waveguide through which light propagates;
A near-field optical waveguide in which metal nanoparticles are dispersed in a dielectric;
The near-field light that joins the propagation optical waveguide and the near-field optical waveguide , has the same cross section as the propagation optical waveguide at the joint surface with the propagation optical waveguide, and converts the propagation light into near-field light, and the near-field light A portion having a cross-sectional area that decreases from the cross-section in the portion that propagates from and converts to the near-field light toward the near-field optical waveguide, and a joint portion of the same material as the near-field optical waveguide;
The equipped, near-field optical waveguide junction and wherein the real part of the effective refractive index of the junction is 1.0 to 1.2. 3. The near-field optical waveguide junction according to claim 1 , wherein the junction is configured such that a cross-sectional area smoothly decreases from the propagation optical waveguide toward the near-field optical waveguide. apparatus. 4. The near field according to claim 1, wherein, in the junction and the near field optical waveguide, the metal nanoparticles have a cylindrical shape, and the dielectric is SiO _2. Optical waveguide bonding device.   4. The near-field optical waveguide bonding apparatus according to claim 1, wherein the metal nanoparticles are core-shell type metal nanoparticles in the junction and the near-field optical waveguide. 5.   The number of the metal nanoparticles in the region where the joint is close to the joint surface with the propagation optical waveguide is smaller than that in other regions. Near-field optical waveguide bonding device.   The tip portion of the propagation optical waveguide has a shape in which a cross-sectional area decreases toward the tip, and the tip portion is configured to be inserted into the joint portion. The near-field optical waveguide bonding apparatus according to any one of the above.