JP3828472B2 - Optical functional element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical functional element used as a laser, an optical switch, an optical filter, an optical modulator, or the like.
[0002]
[Prior art]
In recent years, photonic crystals have attracted great interest as materials that enable control of light, which was impossible with conventional optical functional elements. A photonic crystal is a multidimensional periodic structure in which two or more media having different refractive indexes are combined. FIG. 2 is a diagram showing an example of what is called a two-dimensional photonic crystal among the photonic crystals. In the two-dimensional photonic crystal shown in FIG. 2, cylinders 22 having a dielectric constant ε2 are arranged in a triangular lattice shape on a medium 11 having a dielectric constant ε1 (ε1> ε2). The cylinder 22 has a periodic structure in a direction parallel to the paper surface, and the vertical structure has a uniform structure. In the case where the cylinder 22 is hollow, ε2 = 1. In FIG. 2, a represents a lattice constant, and r represents a radius of the cylinder.
[0003]
A diagram showing the relationship between the frequency and frequency of light propagating through a photonic crystal is called a photonic band diagram. FIG. 3 shows the structure of FIG. ^1/2 FIG. 4 is a diagram showing photonic band diagrams for the TM mode and the TE mode when = 3.5, ε2 = 1, and r / a = 0.45. Here, the TM mode refers to a mode in which the electric field is perpendicular to the paper surface, and the TE mode refers to a mode in which the electric field is parallel to the paper surface. The vertical axis represents the normalized frequency (ωa / 2πc), and the horizontal axis represents the wave vector (ka / 2π) normalized in the first Brillouin zone. c represents the speed of light in vacuum, ω represents the angular frequency of light, and k represents the wave number. The triangular lattice of FIG. 2 corresponds to hexagonal symmetry, and the formed Brillouin zone has a regular hexagonal structure illustrated in FIG. The vertex of the regular hexagon is the K point, the midpoint of each side is the M point, and the point where the wave number is 0 is the Γ point.
[0004]
As indicated by hatching in FIG. 3, there is no band across the entire first Brillouin zone in a specific (normalized) frequency region. This means that light having a frequency corresponding to this band cannot propagate through the photonic crystal. Such a frequency band in which propagation is prohibited is called a photonic band gap. When this photonic band gap is used, it is possible to control light, which is impossible with conventional devices, and is attracting attention.
[0005]
Photonic crystals with such characteristics are expected to be applied in various fields, but researches aimed at application to optical parts are particularly active. Introducing linear or point-like defects in two-dimensional photonic crystals to produce waveguides and other optical functional elements is said to have a significant effect on miniaturization and high performance. Devices have been proposed and studied.
[0006]
For example, Patent Document 1 shows an example of a wavelength demultiplexing circuit using a photonic crystal. In this element, a two-dimensional photonic crystal is formed on a substrate, and wavelength-multiplexed optical pulses are demultiplexed by utilizing the anisotropy of refractive index dispersion. [Patent Document 2] shows an example of optical signal control using a photonic crystal. In this device, a beam is provided on the upper surface of the two-dimensional photonic crystal formed on the substrate, and the optical signal propagating through the two-dimensional photonic crystal is controlled by attracting or separating the beam from the upper surface of the crystal.
[0007]
Further, in an optical functional element such as an optical switch or an intensity modulator, the propagation of light is controlled by changing the refractive index / reflectance of the material and other physical constants by applying an external voltage. The same applies to the case of using a photonic crystal, and some external control is required to make the device functional. With this external control, an optical switch using a photonic crystal, an intensity modulator, and the like have been proposed.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-271541
[Patent Document 2]
US Patent Application Publication No. 2002/0021878
[Patent Document 3]
JP 09-166606 A
[Patent Document 4]
JP-A-11-330619
[Non-Patent Document 1]
Journal of Microelectromechanical Systems, Vol. 6, no. 1, 1997 PP. 10-17
[0009]
[Problems to be solved by the invention]
As a control method from the outside of the element as described above [Patent Document 1], conventionally, the refractive index of a material is generally changed. As a combination of photonic crystal materials, a semiconductor such as silicon (Si) or gallium arsenide (GaAs) is used as a high refractive index medium, and air or silicon dioxide (SiO2) is used as a low refractive index medium. ₂ ) Is generally used. In order to obtain a change in refractive index, for example, electric field application to a semiconductor can be considered. However, in that case, a complicated electrode structure is required for effective electric field application. Further, in order to obtain a change in refractive index enough to constitute an optical functional element, it is necessary to apply a very large voltage. As another method for obtaining a change in refractive index, there is a method for obtaining a refractive index control using the thermo-optic effect of a semiconductor. However, this method also requires a large change in temperature in order to obtain an effective refractive index change with the disclosed device configuration, and is difficult to realize.
[0010]
In addition, as in [Patent Document 2], in signal control by providing a beam on the upper surface of a two-dimensional photonic crystal and controlling its position, a guideline for constructing a practical device if the control mechanism is not clear. Cannot be obtained.
[0011]
An object of the present invention is to provide a configuration and a method for effectively performing external control on a photonic crystal with a relatively simple configuration, for example, a high-performance optical functional device that operates at a low operating voltage, and its manufacture It is to provide a method.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, a structure constituting a photonic crystal, that is, a photonic crystal slab (a plate-like photonic crystal structure in which the thickness direction of a two-dimensional photonic crystal is finite) is formed. Pay attention to the fact that the band structure of the photonic crystal changes when another structure is placed close to the top surface, analyze the change in detail, and provide a guideline for controlling the relative positional relationship between them. Propose concretely.
[0013]
FIG. 1 is a perspective view showing a basic configuration of an optical functional element of the present invention. In the present invention, the photonic crystal slab 11 and the flat plate 12 are arranged in parallel to the upper surface of the photonic crystal slab 11. In the photonic crystal slab 11, a periodic structure of a cylinder 22 is formed. Here, the upper surface refers to the surface on which the end surface of the cylinder 22 forming the periodic structure of the photonic crystal slab 11 appears. In the photonic crystal slab 11, when light is incident on one end thereof, the light propagates through the photonic crystal slab 11 according to the band structure unique to the photonic crystal, and finally the light propagated from the opposite end face is emitted. However, the flat plate 12 is moved closer to or away from the upper surface of the photonic crystal slab 11 via the operation rod 14 operated by the driving device 13, and the propagation of light in the photonic crystal slab 11 is controlled. To do. In FIG. 1, the flat plate 12 moves perpendicularly to the upper surface of the photonic crystal slab 11, but this moves to the left and right at a position away from the upper surface by a predetermined distance. May be. Further, the driving device 13 and the operating rod 14 are not limited to those that are mechanically driven, and include, for example, a case where the driving force is generated by an electric field acting between the crystal slab 11 and the flat plate 12. 12 means that some force is applied between the two.
[0014]
4A and 4B are diagrams showing examples of the band structure of the photonic crystal slab 11 obtained by simulation. In this example, the medium of the photonic crystal slab 11 is Si, its refractive index is 3.5, it is composed of a triangular lattice of holes, a is a lattice constant, the hole radius is 0.3a, and the thickness of the slab is 0.5a. The medium of the flat plate 12 arranged in parallel to the upper surface of the photonic crystal slab 11 was Si, and its thickness was 0.5a.
[0015]
When the propagating light is in the TE mode, the light propagates through the photonic crystal slab 11 according to the dispersion curve 42 existing below the light line 41.
[0016]
4A shows the band structure of the photonic crystal slab 11 when the flat plate 12 is not present, and FIG. 4B shows the second structure on the upper surface of the photonic crystal slab 11 that is the first structure. The band structure of the photonic crystal slab 11 is shown when the flat plate 12 as an object is arranged in the vicinity of 1/10 (= 0.1a) of the lattice constant of the photonic crystal. As can be seen by comparing FIG. 4A and FIG. 4B, the band structure is significantly changed. That is, the characteristics of light propagating through the photonic crystal slab change greatly.
[0017]
For example, as a typical example, the medium of the photonic crystal slab 11 is Si, the refractive index thereof is 3.5, the lattice constant a is 1 μm, the hole triangular lattice, the hole radius is 300 nm, and the thickness of the slab is Even if the distance between the upper surface of the photonic crystal slab 11 and the flat plate 12 is changed to a very small value of 100 nm when the thickness of the flat plate 12 is Si and the thickness thereof is 0.5 a, the photonic crystal is 500 nm. It has been confirmed that the intensity of light propagating through the crystal slab 11 varies greatly from about 1.0 to about 0.1.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0019]
Example 1
FIG. 5A is a plan view showing the concept of the configuration of an embodiment of the optical functional element according to the present invention, and FIG. 5B is a cross-sectional view seen in the arrow direction at the AA position. In this embodiment, a photonic crystal slab 11 is prepared as a first structure made of a photonic crystal, and a periodic structure of a cylinder 22 is formed. The cylinder 22 was specifically a hole. As a second structure, a flat plate 12 made of a dielectric is provided close to the upper surface of the photonic crystal slab 11, and the distance between the photonic crystal slab 11 and the flat plate 12 is changed, whereby the intensity and phase of propagating light are changed. It is the structure which changes. As shown in the figure, light enters from the left side of the figure and exits from the right side.
[0020]
In this example, the medium of the photonic crystal slab 11 is Si, and its refractive index is 3.5, the thickness is 175 nm, the lattice spacing is 350 nm, and the hole 22 has a radius of 105 nm. The periphery of the slab 11 is composed of air. The direction of light incidence is the Γ-M direction of the triangular lattice, and the wavelength is 1.55. μm It is. The flat plate 12 was made of Si having a refractive index of 3.5, and its thickness was 175 nm.
[0021]
FIG. 6 shows the result of obtaining the transmittance and phase change of light propagating through the photonic crystal slab 11 by simulation by changing the distance between the upper surface of the photonic crystal slab 11 and the flat plate 12 in the configuration shown in FIG. FIG. The horizontal axis in FIG. 6 is the distance d between the upper surface of the photonic crystal slab 11 and the flat plate 12, the left axis is the normalized transmittance, and the right axis is the phase change. As can be seen from the figure, the light transmittance decreases from around d = 250 nm as the distance d decreases. Thereafter, a minimum value is taken near d = 80 nm, and thereafter, the light transmittance is increased and the light transmittance is increased. It can be seen that at d = 0 nm where the flat plate and the photonic crystal slab are in close contact, the light transmittance almost returns to the light transmittance at d> 250 nm, that is, the light transmittance without the flat plate. This phenomenon occurs in a wavelength region where a change in transmittance that can be put to practical use is obtained when the distance d between the flat plate and the photonic crystal slab is changed.
[0022]
This is a newly discovered point and has a very important meaning. That is, the light transmittance cannot be changed by simply bringing the flat plate into close contact with the photonic crystal slab. In the configuration in which the result of FIG. 6 is obtained, it is shown that efficient modulation of light transmittance cannot be controlled unless the flat plate and the photonic crystal slab are separated from each other by at least d = 50 nm. In this way, it is essential that the flat plate 12 and the photonic crystal slab 11 are kept in close contact with each other without being brought into close contact with each other. Of course, the value of d = 50 nm shown here depends on the structure and material of the flat plate and the photonic crystal slab.
[0023]
On the other hand, it can be seen that the phase of the emitted light changes greatly when the distance d is in the range of 50 to 80 nm, and the phase changes by π before and after this. In this way, both the light transmittance and the phase can be significantly changed by slightly changing the distance d.
[0024]
FIG. 7 is a diagram in which the transmittance of light propagating through the photonic crystal slab 11 is obtained by simulation in order to clarify the cause of the large change described above. The solid line in FIG. 7 is the result when the flat plate 12 is not present, and the wavy line in FIG. 7 is the result when the flat plate 12 is installed at a distance d = 0.1a (a is the lattice constant). The photonic crystal slab 11 is composed of a triangular hole lattice, the hole radius r = 0.3a, the slab thickness t = 0.5a, the slab refractive index 3.5, and the flat plate 12 has a refractive index 3. 5. The thickness is 0.5a, and the length is 6a. From FIG. 7, it can be seen that the light propagating through the photonic crystal slab 11 is greatly affected by the presence of the flat plate 12 and its characteristics are greatly changed. A particularly characteristic point is that a transmission peak appears in a band gap existing in the vicinity of a normalized frequency of 0.22 to 0.32 due to the presence of a flat plate. Thus, it can be seen that the presence of the flat plate 12 creates a new level in the band gap. This corresponds to a change in the band structure of the photonic crystal. Thus, it was shown that it is important that the state of propagation of light propagating through the photonic crystal is significantly changed by changing the band structure of the photonic crystal.
[0025]
FIG. 8 is a perspective view showing the structure of the produced optical functional element based on the structure corresponding to FIG. The photonic crystal slab 11 is composed of Si having a refractive index of 3.5, a hole triangular lattice with holes 22 having a lattice interval of 350 nm, a hole radius of 105 nm, and a thickness of 175 nm. The periphery of the slab 11 is composed of air. The photonic crystal slab 11 is formed on the substrate 71. In order to form an appropriate gap between the photonic crystal slab 11 and the substrate 71 and to electrically insulate, the photonic crystal slab 11 is made of SiO2. ₂ Formed through layer 72. In addition, in order to efficiently introduce incident light from an optical fiber (not shown) into the photonic crystal slab 11, and to guide the outgoing light from the photonic crystal slab 11 to the optical fiber (not shown), the photonic crystal Ridge-type waveguides 75 are provided on both sides of the slab 11. This ridge-type waveguide 75 has the same thickness as the photonic crystal slab layer 11 and a width of 3 μm.
[0026]
The thickness of the flat plate 12 is 175 nm, and the refractive index is 3.5. Moreover, both ends of the flat plate 12 are made of SiO. ₂ It arrange | positions so that the upper surface of the photonic crystal slab 11 may be opposed through the layer 74. FIG. This is to electrically insulate the photonic crystal slab 11 and the flat plate 12 and to keep the distance between the photonic crystal slab 11 and the flat plate 12 at a predetermined value in a steady state. In this example, this is 0.5 μm It was. Further, notches 12 a and 12 b are provided in portions near both ends of the flat plate 12. This is because the flat plate 12 is deformed while being kept parallel to the upper surface of the photonic crystal slab 11. Easy to do It is to do. It should be noted that the flat plate 12 is spatially formed on the lower surface of the photonic crystal slab 11 on the lower surface. ₂ There is no layer, it can move freely in a certain range, and the distance between the photonic crystal slab 11 and the flat plate 12 can be changed.
[0027]
The photonic crystal slab 11 and the flat plate 12 are n-type doped with phosphorus (P) in order to have conductivity. Electrodes 77 and 76 are formed, respectively, and lead wires 79 and 78 are drawn out from the electrodes.
[0028]
The wavelength of the photonic crystal slab 11 is 1.55 from the Γ-M direction of the triangular lattice. μm Of light. At this time, if no voltage is applied to the photonic crystal slab 11 and the flat plate 12, the distance between them is 0.5. μm Thus, as can be seen with reference to FIG. 6, the normalized transmittance is approximately 1.0. On the other hand, when a voltage is applied to the photonic crystal slab 11 and the flat plate 12 via the lead wires 79 and 78, the flat plate 12 is attracted to the upper surface of the photonic crystal slab 11 by an attractive force between static electricity generated between the two. Now, when a voltage of 10 V is applied from the lead wires 78 and 79, the light transmittance between the optical fibers connected to the incident side and the outgoing side of the element is reduced by 9 dB as compared with the case where the voltage is not applied. This result corresponds to the fact that by applying the voltage, the distance between the photonic crystal slab and the flat plate is reduced, and the light transmission characteristics are reduced as predicted by the simulation.
[0029]
As described above, the optical functional element according to the present invention is not only a light intensity modulator having a function of changing the intensity of an optical pulse, but also has a function as an optical phase modulator. When a voltage of 15 V was applied from the lead wires 78 and 79, the phase of light at the output end of the element changed by approximately π compared to the case where no voltage was applied. At this time, the change of the light transmittance before and after the voltage application is as small as about 20%, and only the phase can be changed. This can be explained qualitatively from FIG. 6 which is the result of the simulation. That is, before the voltage is applied, the distance d between the photonic crystal slab 11 and the flat plate 12 is large, the light transmittance is almost 100%, and the phase is almost zero. As the light transmittance approaches, the light transmittance returns to almost 100%, while the phase remains changed by almost π. That is, the element according to the present invention functions as a low-loss and ultra-small phase modulator.
[0030]
FIGS. 9A to 9F are cross-sectional views (including a partial plan view) showing a main part of an example of a process for realizing the structure of the optical functional element shown in FIG. These cross-sectional views are cross sections viewed in the direction of the arrow at the position BB in FIG.
[0031]
First, as shown in FIG. 9A, SiO is formed on the Si substrate 71 for forming the substrate 71. ₂ A film 72 is formed, and an SOI (Silicon on Insulator) having the Si layer 11 for forming the photonic crystal slab 11 is prepared thereon. SiO ₂ The thickness of the membrane 72 is 0.5 μm The thickness of the Si layer 11 is 175 nm. The Si layer 11 is doped with P.
[0032]
Next, as shown in FIG. 9B1, vacancy 22 is formed in Si layer 11 with vacancy 22 having a lattice spacing of 350 nm and vacancy radius of 105 nm by electron beam exposure and vapor phase etching. The nick crystal slab 11 is produced. FIG. 9B2 shows this plan view.
[0033]
Thereafter, as shown in FIG. 9C, the photonic crystal slab 11 is embedded in the SiO 2 by bias sputtering. ₂ A film 74 is formed. At this time, SiO ₂ The film 74 is 0.5 mm from the upper surface of the photonic crystal slab 11. μm It was made to become the thickness of.
[0034]
After this step, as shown in FIG. ₂ On the film 74, the Si layer 12 for forming the flat plate 12 is formed with a thickness of 175 nm. The Si layer 12 is doped with P.
[0035]
Next, as shown in FIG. 9 (E1), the flat plate 12 and the notches 12a and 12b are formed by the electron beam exposure method and the vapor phase etching method. FIG. 9E2 shows this plan view.
[0036]
After that, as shown in FIG. ₂ Film 74 and SiO ₂ The film 72 is removed to form the structure shown in FIG. At this time, the ridge-type waveguide 75 portion of the SiO 2 that supports the photonic crystal slab 11 is SiO 2. ₂ SiO for supporting the side portions parallel to the optical path of the film 72 and the photonic crystal slab 11 and the end portions of the flat plate 12 supporting the flat plate 12 ₂ The film 74 is made of SiO. ₂ The etching time is adjusted to leave the layer. Actually, the waveguide 75 portion and the end region of the flat plate 12 are overwhelmingly larger than the region where the light of the photonic crystal slab 11 propagates, so that the etching time can be easily adjusted. In addition, SiO for supporting the end of the flat plate 12 ₂ Since the film 74 is removed at the cross-sectional position, hatching indicating the cross-section is not attached. Finally, electrodes are formed on the Si layers 11 and 12, and lead wires 79 and 78 are attached.
[0037]
As can be seen from the characteristics of FIG. 6, the distance between the photonic crystal slab 11 and the flat plate 12 is extremely small in the suction state, so that after the structure shown in FIG. 8 is formed in the process shown in FIG. , SiO on the photonic crystal slab 11 ₂ The fine particles (particle size of about 80 nm) are preferably dispersed to form a spacer.
[0038]
(Example 2)
In Example 1, an optical functional element was manufactured by the process shown in FIG. 9, but another manufacturing method is illustrated here. FIG. 10 is a diagram showing a manufacturing process in the case where GaAs is used as the material of the photonic crystal slab that is the first structure and Si is used as the flat plate that is the second structure.
[0039]
First, as shown in FIG. 10A, an AlAs layer 92 and a GaAs layer 93 that will eventually become a photonic crystal slab are epitaxially grown on a GaAs substrate 91. The thickness of the AlAs layer 92 is 0.5. μm The thickness of the GaAs layer 93 is 175 nm. The GaAs layer 93 is doped with Si.
[0040]
Next, as shown in FIG. 10B, a triangular lattice of holes 22 having a lattice interval of 350 nm and a hole radius of 105 nm is formed in the GaAs layer 93 by an electron beam exposure method and a gas phase etching method, and a photonic crystal is formed. The slab 11 is produced.
[0041]
Thereafter, as shown in FIG. 10C, the AlAs layer 92 between the photonic crystal slab 11 and the GaAs substrate 91 is removed using an etchant that selectively etches only AlAs. Also in this case, as in the first embodiment, the waveguide 75 portion and the end region of the AlAs layer 92 serving as the support portion of the photonic crystal slab 11 are overwhelming as compared with the region where the light of the photonic crystal slab 11 propagates. Therefore, it can be easily left by adjusting the etching time.
[0042]
On the other hand, as shown in FIG. 10D, SiO 2 is formed on the surface of the Si substrate 95 for forming the flat plate 12 as the second structure. ₂ Layer 96 is formed. The Si substrate 95 is doped with P. SiO ₂ The thickness of layer 96 is 0.5. μm It was.
[0043]
Next, as shown in FIG. 10 (E), SiO 2 that supports the flat plate 12 on the photonic crystal slab 11 by a normal light exposure method and hydrofluoric acid etching. ₂ Layer 96 is formed.
[0044]
Thereafter, as shown in FIG. 10 (F1), the back surface 99 of the Si substrate 95 is shaved by a back etching method, and the Si layer 98 is left with a thickness of 175 nm. This Si layer 98 corresponds to the flat plate 12 shown in FIG. Here, both side surfaces of the Si substrate 95 are left and used as a holding portion for the bonding operation. Therefore, after this process, notches 98a and 98b are formed on both sides of the Si layer 98 in the same manner as the notches 12a and 12b. Of course, notches 12a and 12b shown in FIG. 8 are also formed in the Si layer 98. FIG. 10F2 shows a view from the bottom.
[0045]
Thereafter, as shown in FIG. 10G, a flat plate as the second structure shown in FIG. 10F1 is formed on the photonic crystal slab 11 as the first structure shown in FIG. 10C. 98 is turned upside down and pasted together. Finally, electrodes and the like were formed, and the element structure shown in FIG. 8 was produced.
[0046]
According to the second embodiment, the process of producing the photonic crystal slab 11 on the GaAs substrate 91 and the process of producing the Si layer 98 corresponding to the flat plate 12 can be separated. Although necessary, each can be created with high accuracy. Moreover, the freedom degree of each material and structure becomes high.
[0047]
If both side surfaces of the Si substrate 95 used as a holding portion for the bonding operation are formed in a plane parallel to the notches 12a and 12b, the Si layer 98 of Example 2 has a notch 98a. 98b is no longer necessary.
[0048]
Example 3
In Example 2, the case where GaAs was used as the material of the photonic crystal slab 11 serving as the first structure and Si was used as the flat plate 12 serving as the second structure was illustrated. Then, the photonic crystal slab 11 and the flat plate 12 are separately formed and pasted. Here, as shown in FIG. 11, the case where the GaAs substrate 91 itself for forming the photonic crystal slab 11 is used as the second structure is shown. Therefore, in this example, the photonic crystal slab 11 moves relative to the substrate 91.
[0049]
First, as shown in FIG. 11A, on the GaAs substrate 91, an AlAs layer 92 that becomes an insulating layer and a GaAs layer 93 that finally becomes a photonic crystal slab are epitaxially grown. The thickness of the AlAs layer 92 is 0.5. μm The thickness of the GaAs layer 93 is 175 nm. The GaAs substrate 91 and the GaAs layer 93 are doped with Si.
[0050]
Next, as shown in FIG. 11B, a triangular lattice of holes 22 having a lattice interval of 350 nm and a hole radius of 105 nm is formed in the GaAs layer 93 by an electron beam exposure method and a gas phase etching method, and a photonic crystal is formed. The slab 11 is produced.
[0051]
Thereafter, as shown in FIG. 10C, the AlAs layer 92 between the photonic crystal slab 11 and the GaAs substrate 91 is removed using an etchant that selectively etches only AlAs. Also in this case, as in the first embodiment, the waveguide 75 portion and the end region of the AlAs layer 92 serving as the support portion of the photonic crystal slab 11 are overwhelming as compared with the region where the light of the photonic crystal slab 11 propagates. Therefore, it can be easily left by adjusting the etching time.
[0052]
With such a configuration, when an electrode is provided on each of the substrate 91 and the photonic crystal slab 11 and a voltage is applied, the photonic crystal slab 11 itself is bent and the distance from the substrate 91 can be changed. . As a result, a change in the intensity of light propagating through the photonic crystal slab 11 is observed, and even when the substrate is the second structure, the relative positions of the first structure and the second structure are determined. It has been shown that it is possible to change the properties of the first structure. In this case, since the ridge-type waveguide 75 is not deformed, there is no problem in introducing light from a fiber (not shown).
Example 4
Example 4 is an example of manufacturing an element structure by a bonding method similar to Example 2, but realized in another form. Similarly to Example 2, a manufacturing process in the case where GaAs is used as the material of the photonic crystal slab that is the first structure and Si is used as the flat plate that is the second structure will be described.
[0053]
First, as shown in FIG. 12A, an AlAs layer 92 and a GaAs layer 93 that will eventually become a photonic crystal slab are epitaxially grown on a GaAs substrate 91. The thickness of the AlAs layer 92 is 0.5. μm The thickness of the GaAs layer 93 is 175 nm. The GaAs layer 93 is doped with Si.
[0054]
Thereafter, as shown in FIG. 12B, SiO for supporting the flat plate 12 to be the second structure body. ₂ The layer 96 is formed on the epitaxially grown GaAs layer 93 by vapor phase chemical growth.
[0055]
Further, as shown in FIG. 12C, the region where the photonic crystal slab 11 is formed is etched to a predetermined thickness by a light exposure method and a vapor phase etching method. At this time, SiO supporting the flat plate 12 on the photonic crystal slab 11 ₂ Layer 96 is also patterned and formed simultaneously. Since the portion left for supporting the flat plate 12 is in a position corresponding to both end portions of the flat plate 12, hatching indicating a cross section is not given in this drawing.
[0056]
Next, as shown in FIG. 12 (D1), holes having a lattice spacing of 350 nm and a hole radius of 105 nm are formed in the region of the GaAs layer 93 where the photonic crystal slab 11 is formed by electron beam exposure and vapor phase etching. A triangular lattice is formed, and the photonic crystal slab 11 is produced. A plan view is shown in FIG. In the plan view, the GaAs layer 93 left for supporting the flat plate 12 is SiO 2. ₂ Under layer 96, it does not appear in the drawing.
[0057]
Thereafter, as shown in FIG. 12E, the lower surface of the photonic crystal slab 11 is made an air layer by using an etching solution that selectively etches only the AlAs layer 92. At this time, the region that becomes the support portion of the photonic crystal slab 11 is left as in the first and second embodiments.
[0058]
On the other hand, as shown in FIG. 12F, a Si substrate 95 is prepared for forming the flat plate 12 as the second structure. The Si substrate 95 is doped with P.
[0059]
Thereafter, as shown in FIG. 12G, the back surface 99 of the Si substrate 95 is removed by a back etching method, and the Si layer 98 is left with a thickness of 175 nm. After this process, notches 98a and 98b are created. This Si layer 98 corresponds to the flat plate 12 shown in FIG. Here, although not shown in the figure, notches 12a and 12b are formed in the Si layer 98. Note that if both side surfaces of the Si substrate 95 used as a holding portion for the laminating operation are formed in a plane parallel to the notches 12a and 12b, the Si layer 98 of Example 4 also has the notches 98a, It is no longer necessary to create 98b.
[0060]
Thereafter, as shown in FIG. 12H, a flat plate as a second structure shown in FIG. 12G is formed on the photonic crystal slab 11 as a first structure shown in FIG. 98 is turned upside down and the two are attached. Finally, electrodes and the like were formed, and the element structure shown in FIG. 8 was produced.
[0061]
According to the fourth embodiment, the process of manufacturing the photonic crystal slab 11 on the GaAs substrate 91 and the process of forming the Si layer 98 corresponding to the flat plate 12 can be separated. Although necessary, each can be created with high accuracy. Moreover, the freedom degree of each material and structure becomes high.
[0062]
(Example 5)
Example 5 is an element structure manufactured by a bonding method similar to Example 4, but shows an example in which the flat plate 12 as the second structure is realized in another form. 12A to 12E, the process is the same as that of the fourth embodiment until the process of manufacturing the portion for holding the photonic crystal slab 11 and the flat plate 12 on the GaAs substrate 91.
[0063]
First, as shown in FIG. ₂ An SOI substrate having a film 92 and a Si layer 97 is prepared. SiO ₂ The thickness of the membrane 92 is 0.5 μm The thickness of the Si layer 97 is 175 nm. The Si layer 97 is doped with P.
[0064]
Next, as shown in FIG. 13B, notches 97a and 97b corresponding to the notches 98a and 98b of Example 4 are formed in the Si layer 97 by the electron beam exposure method and the vapor phase etching method. This Si layer 97 corresponds to the flat plate 12 shown in FIG. Here, although not shown in the figure, notches 12a and 12b are formed in the Si layer 97 after this process.
[0065]
Next, as shown in FIG. ₂ Layer 92 is etched except for support at both ends. FIG. 13C2 shows a side view. Remaining SiO ₂ The layer 92 does not exist at the position of the cross-sectional view, but is displayed at both ends in the side view.
[0066]
Thereafter, as shown in FIG. 13D, the back surface 99 of the Si substrate 95 is shaved by a back etching method, and the Si layer 98 is left with an appropriate thickness. Note that if both side surfaces of the Si substrate 95 used as a holding portion for the laminating operation are formed in a plane parallel to the notches 12a and 12b, the Si layer 97 of Example 5 also has the notch 98a, It is no longer necessary to create 98b.
[0067]
After that, as shown in FIG. 13E, it is joined to a portion having the photonic crystal slab 11 separately manufactured as shown in FIG.
[0068]
In Example 5, the number of steps is increased compared to Example 4. However, since the Si layer 97 corresponding to the flat plate 12 is formed on the basis of the SOI substrate, the thickness can be precisely controlled. Moreover, the freedom degree of each material and structure becomes high.
[0069]
In Example 5, the distance between the photonic crystal slab 11 and the plate portion 98 may be changed by applying a voltage between the plate portion 98 that is a flat plate and the Si substrate 95 that is a holding portion. good
(Example 6)
Example 6 is the production of an element structure by a bonding method similar to Example 4, but shows an example in which the flat plate 12 as the second structure is realized in a form different from Example 5. 12A to 12E, the process is the same as that of the fourth embodiment until the process of manufacturing the portion for holding the photonic crystal slab 11 and the flat plate 12 on the GaAs substrate 91.
[0070]
First, as shown in FIG. ₂ A film 92 is formed. SiO ₂ The thickness of the membrane 92 is 0.5 μm It is.
[0071]
Next, as shown in FIG. 14 (B1), the portion corresponding to the central movable portion of the flat plate 12 remains so that the portion corresponding to the movable portion remains. ₂ The film 92 is patterned. A plan view is shown in FIG. That is, only the portion with a thin dot in the broken line corresponding to the pattern of the flat plate 12 is SiO. ₂ The membrane 92 is left.
[0072]
Next, as shown in FIG. ₂ A Si layer 97 is formed on the film 92 by sputtering so that the Si layer 97 including the exposed surface of the Si substrate 95 becomes flat. The resulting Si layer 97 has a thickness of SiO ₂ 175 nm on film 92. The Si layer 97 is doped with P.
[0073]
Next, notches 97a and 97b corresponding to the notches 98a and 98b of the fourth embodiment are formed in the Si layer 97 by electron beam exposure and vapor phase etching. This Si layer 97 corresponds to the flat plate 12 shown in FIG. Here, although not shown in the figure, notches 12a and 12b are formed in the Si layer 97 after this process.
[0074]
Next, as shown in FIG. ₂ Layer 92 is etched away. Further, the back surface 99 of the Si substrate 95 is scraped by a back etching method, and the Si layer 98 is left with an appropriate thickness. Note that if both side surfaces of the Si substrate 95 used as a holding portion for the laminating operation are formed in a plane parallel to the notches 12a and 12b, the Si layer 97 of Example 6 also has the notches 98a, It is no longer necessary to create 98b.
[0075]
After that, as shown in FIG. 14E, it is joined to a portion having the photonic crystal slab 11 separately manufactured as shown in FIG.
[0076]
As can be seen by comparing FIG. 14 (D) and FIG. 13 (D), the sixth embodiment is different from the fifth embodiment in that only the position corresponding to the movable portion of the flat plate 12 is SiO. ₂ Since the layer 92 is left, the other parts differ only in that they become the Si layer 97.
[0077]
In the sixth embodiment, as in the fifth embodiment, the number of processes is increased as compared with the fourth embodiment. However, since the Si layer 97 corresponding to the flat plate 12 is separately formed, the thickness can be accurately controlled. Moreover, the freedom degree of each material and structure becomes high.
[0078]
(Example 7)
In the first embodiment, there is one each of the first structure made of the photonic crystal and the second structure close to the first structure, but even when there are a plurality of both structures. Characteristics as an effective optical functional element can be obtained. FIG. 15 is a perspective view illustrating an example of the seventh embodiment.
[0079]
In FIG. 15, a flat plate 12 made of a dielectric as a second structure is formed on the photonic crystal slab 11 on the basis of the structure shown in FIG. ₁ , 12 ₂ Is formed in a cascade. In FIG. 15, the same reference numerals are given to the main elements corresponding to those in FIG. 8, and two elements having the same function are identified by subscripts 1 and 2. The data of each element of the optical functional element shown in FIG. 15 may be the same as those described in FIG.
[0080]
In the seventh embodiment, the first flat plate 12 ₁ The light transmittance can be reduced by the second flat plate 12. ₂ It was revealed that the light intensity can be further greatly reduced. The attenuation factor of the light transmitted through both is as large as 20 dB, and the characteristics are greatly improved by the presence of the plurality of second structures. Thus, the use of a plurality of structures is particularly effective when restrictions are imposed on the shape and size of a single second structure. It goes without saying that the use of a plurality of structures is also effective when there are various restrictions on the first structure made of a photonic crystal. In addition to limiting the shape and size of the first structure, the presence of a plurality of structures is effective when different functions are derived, particularly when light of different wavelengths is turned on and off independently.
[0081]
(Example 8)
The optical functional element according to the present invention can be realized regardless of whether the first structure is a one-dimensional photonic crystal, a two-dimensional photonic crystal including a photonic crystal slab, or a three-dimensional photonic crystal. Examples 1 to 7 describe the case where the first structure is a photonic crystal slab, which is a two-dimensional photonic crystal. FIG. 16 is a perspective view showing an embodiment in which the first structure is a one-dimensional photonic crystal.
[0082]
In FIG. 16, 161 is SiO. ₂ It is a substrate, and the region 162 is composed of an Si layer and SiO. ₂ Layer is SiO ₂ A one-dimensional photonic crystal in which 10 layers are alternately stacked on a substrate 161. Si layer thickness is 0.2a, SiO ₂ The layer thickness was 0.8a. a is a lattice constant. The uppermost layer was a Si layer. The second structure is disposed on the uppermost surface of the one-dimensional photonic crystal layer. This structure is the same as that described with reference to FIG. 8, and is given the same reference numerals. The flat plate 12 is made of Si and has a thickness of a. The uppermost Si layer and the flat plate 12 of the one-dimensional photonic crystal layer are doped with P. In the uppermost Si layer and the flat plate 12 of the one-dimensional photonic crystal layer, the distance between the one-dimensional photonic crystal 162 and the flat plate 12 before voltage application is a.
[0083]
Light enters and exits in the direction of the arrow in the figure. 1.55 wavelength μm Is incident, a is 0.54. μm In this case, a transmittance of 50% was obtained. Next, when a voltage of 10 V was applied to control the distance between the one-dimensional photonic crystal 162 and the flat plate 12 to 80 nm, the transmittance was greatly reduced to 2.5%. Thus, an optical modulator capable of turning on and off the light intensity by applying a voltage was obtained.
[0084]
Example 9
FIG. 17 is a perspective view showing the concept of the embodiment when the present invention is realized by a three-dimensional photonic crystal. FIG. 17 shows the element shown in FIG. 8 in which the photonic crystal slab 11 is replaced with a three-dimensional square material laminated photonic crystal 171. In the figure, the relationship between the portion of the flat plate 12 and the three-dimensional square material laminated photonic crystal 171 is not specifically disclosed, but the structural part of the photonic crystal slab 11 is represented by a three-dimensional square material laminated photonic crystal as in FIG. Substituting with the crystal 171 and arranging the flat plate 12 on the periphery thereof may be performed.
[0085]
In the three-dimensional square material laminated photonic crystal 171, one fine square material constituting the three-dimensional square material is extracted, and light propagates through the extracted portion. In addition, only one square layer was formed on the layer from which the fine square rods were removed so that an evanescent wave was present on the top of the three-dimensional square layered photonic crystal 171. The period of the three-dimensional square-stacked photonic crystal is 0.7 μm The width and thickness of the square are 0.2 μm The square bar was made of Si. Also in this case, Si was doped with P so that the light transmittance could be controlled by applying a voltage to the device. Modulation was observed by applying voltage to the device, indicating that it functions as an optical modulator.
[0086]
(Example 10)
The optical functional element according to the present invention can be realized with various characteristics by providing defects in the photonic crystal. Example 10 is an example in which a two-dimensional photonic crystal slab 11 including a line defect 181 as a defect is formed on the basis of the structure shown in FIG.
[0087]
FIG. 18 is a plan view of the two-dimensional photonic crystal slab 11 including the line defect 181. The medium of the two-dimensional photonic crystal slab 11 is Si, and a line defect 181 is formed by removing one row of the holes 22. The flat plate 12 is produced so as to be exactly on the line defect 181, but the display of the flat plate 12 is omitted in the figure. Light enters from the direction of the left arrow and exits in the direction of the right arrow.
[0088]
The characteristics of the optical functional element having the structure of the two-dimensional photonic crystal slab 11 shown in FIG. 18 were measured. As a result, when a voltage of 10 V was applied, the light transmittance between the optical fibers connected to the incident side and the outgoing side of the element was reduced by 12 dB compared to the case where the voltage was not applied. This result corresponds to a decrease in the light transmission characteristics by applying a voltage and reducing the distance between the photonic crystal slab 11 and the flat plate 12 to 80 nm.
[0089]
FIG. 19 shows a plan view of the two-dimensional photonic crystal slab 11 when the line defect is different from FIG. In this example, a photonic crystal slab in the case where a point defect 182 is formed in a part of the above-described line defect 181 is shown.
[0090]
The characteristics of the optical functional element having the structure of the two-dimensional photonic crystal slab 11 shown in FIG. 19 were measured. As a result, when a voltage of 8 V was applied, the light transmittance between the optical fibers connected to the incident side and the outgoing side of the element was reduced by 12 dB compared to the case where the voltage was not applied. This result corresponds to the reduction of the light transmission characteristics by applying a voltage and reducing the distance between the photonic crystal slab 11 and the flat plate 12 to 80 nm as in the case of the line defect.
[0091]
As described above, also in the case of a photonic crystal including a defect such as a line defect or a point defect, the position of the first structure formed of the photonic crystal and the second structure close to the first structure are determined. By approaching to a predetermined value, the characteristics of the first structure can be changed.
[0092]
(Example 11)
In the optical functional element according to the present invention, in the above-described embodiment, the second structure is described as an example of Si doped with P or GaAs doped with Si. However, these are other semiconductors having conductivity. For example, in the case of a semiconductor such as Ge, InP, and GaN, the same characteristics as in the above-described embodiment can be obtained. Instead of semiconductor, SiO ₂ Glass, LiNbO _Three It may be a dielectric such as. Further, it may be a metal, a magnetic material, or a composite thereof including a semiconductor and a dielectric.
[0093]
In the above-described embodiment, however, since the displacement of the second structure is controlled by the potential between the first structure and the dielectric that cannot be energized, it is necessary to devise. For example, the position can be controlled by sticking a flat plate made of a dielectric, which is the second structural body, under a conductive flat plate. That is, the electrostatic force between the semiconductor flat plate and the first structure photonic crystal Therefore A change in both positions can be caused, and the position of the dielectric flat plate attached to the semiconductor flat plate can be changed accordingly.
[0094]
Furthermore, in the case of using a metal as the second structure, the amount of light absorption is very large compared to other semiconductors and dielectrics. For this reason, when used as a light intensity modulator, a large extinction ratio can be obtained. As a result of the study, when Al was used as the flat plate 12 in the element structure shown in FIG. 8, it was connected to the incident side and the emission side of the element as compared with the case where no voltage was applied to 10 V applied voltage. The light transmittance between the optical fibers showed a very large decrease of 18 dB.
[0095]
The materials shown above are only a part of applicable materials, and it goes without saying that other dielectrics, semiconductors, and metal materials can be applied.
[0096]
(Example 12)
The optical functional element shown in Example 12 is characterized in that the second structure is made of a photonic crystal.
[0097]
FIG. 20 is a perspective view showing the configuration of the optical functional element of Example 12. This Example 12 is basically the same as the optical functional element shown in FIG. 8, and differs in that the flat plate 12 as the second structure is composed of a photonic crystal slab. In this case, the photonic crystal slab of the flat plate 12 has the same thickness, the same lattice constant, and the same hole radius as the photonic crystal slab 11 as the first structure.
[0098]
The characteristics of the optical functional device of Example 12 were as follows. When a voltage of 5 V was applied from the lead wires 78 and 79, the light transmittance between the optical fibers connected to the incident side and the outgoing side of the element was reduced by 10 dB compared to the case where the voltage was not applied. This result corresponds to the fact that by applying a voltage, the distance between the photonic crystal slab and the flat plate is reduced, and the light transmission characteristics are reduced. In addition, this result is operated at a lower voltage than the result shown in Example 1, and the flat plate as the second structure is a photonic crystal slab, so that the first structure and the second structure This means that the interaction between the two is maintained even if the distance between the structures is relatively large. That is, the twelfth embodiment can be controlled with a lower voltage than the structure of the first embodiment.
[0099]
(Example 13)
The optical functional element shown in Example 13 is characterized in that the relative positions of the first and second structures are changed using a microactuator using comb-tooth electrodes.
[0100]
FIG. 21A1 is a plan view showing an example in which a Mach-Zehnder type optical modulator is configured by the optical functional element of Example 13. FIG. A photonic crystal slab 11 is formed on the upper surface of the right side portion of the substrate 71, and a microactuator 220 using comb electrodes is formed on the upper surface of the left side portion. FIG. 21 (A2) shows this side view for reference.
[0101]
The photonic crystal slab 11 is made of Si, and is composed of a hole square lattice of holes 22 having a lattice interval of 350 nm and a hole radius of 105 nm, and has a thickness of 175 nm. As shown in the figure, a Mach-Zehnder type line defect waveguide is formed in the hole square lattice. Light enters and exits as indicated by arrows. Of the two line defect waveguides of the Mach-Zehnder type waveguide, control is performed so that the flat plate 12 as the second structure exists or does not exist on one of the waveguides. FIG. 21A1 shows the case where the flat plate 12 does not exist on the waveguide, and FIG. 21B shows the case where the flat plate 12 exists. The flat plate 12 is made of Si and has a thickness of 175 nm. The distance between the flat plate 12 and the photonic crystal slab 11 was 150 nm.
[0102]
The microactuator 220 using the comb-tooth electrode for controlling the movement of the flat plate 12 is the electrostatic actuator disclosed in Japanese Patent Application Laid-Open No. H10-228707. A fixed electrode 223 supported by the frame portion 221 is formed, and plate springs 225 and 227 having the frame portion 221 as a fixed portion are also formed. A movable shaft 229 is coupled to the movable portions of the leaf springs 225 and 227. The free end at the tip of the movable shaft 229 is a flat plate 12. A movable electrode 224 is also coupled to the movable shaft 229. Since the driving force acting between the interdigitated comb electrodes provided on the fixed electrode 223 and the movable electrode 224 deflects the leaf springs 225 and 227, respectively, the flat plate 12 at the tip of the movable shaft 229 is shown in the figure. Move to the right. As a result, as shown in FIG. 21B, the flat plate 12 exists on the waveguide.
[0103]
At this time, the voltage between the fixed electrode 223 and the movable electrode 224 is controlled so that both the two line defect waveguides of the Mach-Zehnder type waveguide are used as shown in FIGS. 21A1 and 21B. The light output when the flat plate 12 is not applied is different from that when the flat plate 12 exists right above one of the waveguides. That is, as shown in FIG. 21A1, compared to the light output when the flat plate 12 is completely shifted from the upper portion of the waveguide, the flat plate 12 is directly above one of the waveguides as shown in FIG. The light output when is present is reduced by 10 dB. This indicates that the phase of light propagating through one of the waveguides is changed by π due to the presence of the flat plate. In this way, it is possible to change the output characteristics of the optical functional element by moving not only in the vertical direction but also in the horizontal direction as the flat plate 12 as the second structure.
[0104]
Since the microactuator 220 using the comb electrode of Example 13 can be formed as an independent one as disclosed in [Patent Document 3], the left side portion of the substrate 71 corresponds to the thickness thereof. For example, the distance between the flat plate 12 and the photonic crystal slab 11 can be easily managed.
[0105]
(Example 14)
In the above-described thirteenth embodiment, the case where the flat plate 12 is provided at the tip of the movable shaft 229 of the microactuator 220 and this is moved in the lateral direction is shown. Example 14 shows an example of an optical functional element in which the comb teeth themselves function as the flat plate 12. FIG. 22A is a perspective view of the optical functional element of Example 14 in an uncontrolled state, and FIG. 22B is a perspective view of a state in which voltage is applied to the comb teeth of the actuator for control. In FIG. 22B, the frame of the actuator is omitted for easy understanding of the hole square lattice of the photonic crystal slab 11.
[0106]
In FIG. 22A, reference numeral 71 denotes a substrate, on which the photonic crystal slab 11 is formed. 22 is a hole. Here, the SiO described in FIG. ₂ The layer 72 and the like are not shown. The photonic crystal slab 11 as the first structure is made of Si, and is formed of a hole square lattice having a lattice interval of 350 nm and a hole radius of 105 nm, and has a thickness of 175 nm. As shown in FIG. 22 (B), this hole square lattice forms a linear coupling defect waveguide, but in FIG. 22 (A), it becomes invisible due to the frame portion of the actuator. The defects corresponded to the state without the holes 22, and the coupling defect waveguide was formed at a ratio of one defect for every three holes. Light enters and exits as shown by arrows.
[0107]
An actuator is formed on the upper surface of the substrate 71. Reference numeral 231 denotes a frame portion of the actuator, and a support portion 233 for the fixed electrode 235 is provided on the left side. A support portion 237 between the movable electrodes 239 is provided on the opposite portion of the frame portion 231. The support portion 237 is separated from the substrate 71 and is coupled to the frame portion 231 by springs 237a and 237b. The fixed electrode 235 and the movable electrode 239 are comb teeth interlaced with each other. It is installed so that the comb electrode portion is just above the defective portion of the waveguide. Both comb electrodes were made of Si doped with phosphorus and had a thickness of 175 nm. When a voltage was applied between the two, the movable electrode 239 moved upward as shown in FIG. 22B, and the distance from the photonic crystal slab 11 was increased. That is, the movable electrode 239 corresponds to the flat plate 12. here,
Naturally, the fixed electrode 235 and the movable electrode 239 should be devised so as not to be short-circuited by the frame portion 231, as described in Japanese Patent Application Laid-Open No. H11-228707. As a result, the wavelength dependence of the group velocity of the propagating light changed, and the group velocity dispersion changed by about 10 ps / nm / mm. Thus, the functional element of Example 14 has a function as a dispersion compensating element with variable group velocity dispersion.
[0108]
The dispersion compensation element using the vertical movement of the comb teeth can vary the amount of dispersion, and there is a function of shortening the time width of an optical pulse incident on the element, that is, a pulse compression function. There is also a function of restoring the original pulse width by using this functional element for an optical pulse signal that has propagated through a long-distance optical fiber and whose pulse has spread.
[0109]
(Example 15)
FIG. 23 shows another example in which the flat plate 12 is moved up and down the photonic crystal slab 11 by a microactuator.
[0110]
FIG. 23 is a sectional view showing the structure of the fifteenth embodiment. SiO on the upper surface of the substrate 71 ₂ A photonic crystal slab 11 is formed through the layer 72. On the other hand, a plate 241 serving as a holding means for the microactuator 220 is provided on the upper surface of the substrate 71. The microactuator 220 is held by a plate 241 so that the movable shaft 229 of the microactuator 220 moves perpendicularly to the upper surface of the photonic crystal slab 11, and the flat plate 12 is provided at the tip of the movable shaft 229.
[0111]
As described in the fourteenth embodiment, the microactuator 220 using the comb electrode can be formed as an independent one as disclosed in [Patent Document 3]. It can be easily attached to the plate 241. Therefore, management of the space | interval of the flat plate 12 and the photonic crystal slab 11 can also be performed easily.
[0112]
(Example 16)
Next, as another example of the microactuator, a case where a scratch actuator is used will be exemplified. FIG. 24 is a perspective view showing the configuration of the sixteenth embodiment. The scratch actuator adopted in Example 16 is conductive on a conductive substrate as introduced in the paper “Scratch Drive Actuator with Mechanical Links for Self-Assembly of Three-Dimensional MEMS” in [Non-Patent Document 1]. A movable plate made of polysilicon is insulated and installed. Further, a claw that engages with the substrate is provided at one end of the movable plate. Then, by applying a rectangular wave voltage that changes positively and negatively between the substrate and the movable plate, the movable plate moves in a certain direction. When the voltage is stopped, it is pulled back in the direction opposite to the direction in which it is moved by the restoring force of the spring acting on the movable plate.
[0113]
Referring to FIG. 24, photonic crystal slab 11 is formed on the upper right side surface of substrate 71. The photonic crystal slab 11 is made of Si, and is composed of a hole square lattice including holes 22 having a lattice interval of 350 nm and a hole radius of 105 nm, and has a thickness of 175 nm. Also here, like the thirteenth embodiment, it has two line defect waveguides of Mach-Zehnder type waveguides. Light enters and exits as indicated by arrows in the figure. On the other hand, a scratch actuator 250 that controls the movement of the flat plate 12 above the waveguide is disposed on the upper left surface of the substrate 71. The flat plate 12 had a width of 5 μm and a thickness of 1 μm, and the distance between the flat plate 12 and the photonic crystal slab 11 was 300 nm. As described above, the scratch actuator 250 includes the conductive substrate 251 and the conductive movable plate 253. Although an insulating layer is formed on the upper surface of the conductive substrate 251, the illustration is omitted. A claw 255 is formed at one end of the movable plate 253. The flat plate 12 is connected to the free end side of the claw 255. As described above, when a rectangular wave voltage that changes between positive and negative is applied between the conductive substrate 251 and the conductive movable plate 253, the movable plate 253 moves to the right side of the figure. When the voltage application is stopped, although not shown, it is pulled back to the initial position on the left side of the drawing by the spring force acting on the movable plate 253.
[0114]
At the initial position of the movable plate 253, the flat plate 12 is located at a position close to one of the two waveguides of the Mach-Zehnder type waveguide. When a rectangular wave voltage that changes between positive and negative is applied between the conductive substrate 251 and the conductive movable plate 253 for a short time, the flat plate 12 moves to a position that completely covers one of the waveguides. When the voltage is turned off, the movable plate 253 returns to the initial position by the force of the spring, so that the flat plate 12 also returns to a position close to one of the waveguides.
[0115]
By applying such a rectangular wave voltage, the flat plate 12 is moved onto one waveguide of the Mach-Zehnder type waveguide or controlled so as to be in a position close to the waveguide, thereby outputting the output light. Could be changed by 11 dB. This indicates that the optical functional element shown in Example 16 has a function as an optical modulator.
[0116]
(Example 17)
The optical functional element according to the present invention is a wavelength separator that spatially separates only a specific wavelength optical signal from the wavelength multiplexed optical signal, or a wavelength multiplexed optical signal. It can have a function of a wavelength multiplexer to be added.
[0117]
FIG. 25 is a top view of an embodiment of the photonic crystal slab 11 made of P-doped Si that constitutes the wavelength separator. Although the figure is simplified and only the photonic crystal slab 11 is shown, the overall configuration is equivalent to the structure of the optical functional element shown in FIG. 8, and the size of the holes 22 and the lattice constant are the same. The photonic crystal slab 11 of Example 17 is a photonic crystal in which the holes 22 form a square lattice.
[0118]
The photonic crystal slab 11 has a waveguide 261 made of a line defect. The optical pulse signal wavelength-multiplexed from the arrow 263 is incident on the waveguide 261 and is emitted to the arrow 264. The wavelength-multiplexed optical pulse is introduced from an optical fiber (not shown) that forms an optical communication network, passes through the photonic crystal slab, and is guided to the optical fiber again. The photonic crystal slab 11 has another waveguide 262 made of a line defect. Light can enter from the arrow 265 and light can exit from the arrow 266. Here, a broken line 12 indicates a position at which the flat plate 12 is disposed in proximity. At this position, the waveguide 262 passes through a position close to the waveguide 261 where only one layer of the hole 22 is separated.
[0119]
Wavelengths 1.5, 1.6 and 1.7 from arrow 263 μm When a voltage of 10 Gb / s was incident, when no voltage was applied between the photonic crystal slab 11 and the flat plate 12, light pulses of all wavelengths were emitted from the arrow 264. Next, when a voltage of 9 V was applied between the photonic crystal slab 11 and the flat plate 12 to bring the photonic crystal slab 11 and the flat plate 12 close to each other, the wavelength 1.5 μm Only the light pulse from the arrow 264 was emitted. This is due to the fact that the two line defect waveguides 261 and 262 function as directional couplers in the region where they are close to each other, and the coupling length is changed by the presence of the flat plate 12.
[0120]
As described above, in Example 17, the line defect waveguides 261 and 262 of the photonic crystal slab 11 are close to each other in the region of the flat plate 12 as shown in FIG. 25, and the flat plate 12 is brought close to the photonic crystal slab 11. By separating or separating, it is shown that it works as an ultra-small wavelength separator that selects only light pulses of a specific wavelength from the wavelength-multiplexed light pulses and spatially separates them or simply passes them.
[0121]
The structure of the seventeenth embodiment also functions as a wavelength multiplexer. This will be described with reference to FIG. In this case, a case will be described where pulse trains of different wavelengths incident from the arrow 265 are added to the optical signal pulse train incident from the arrow 263 and emitted from the arrow 264. In fact, from the arrow 263, the wavelengths 1.5, 1.6 and 1.7 μm When a light pulse of 10 Gb / s was incident, when no voltage was applied between the photonic crystal slab 11 and the flat plate 12, light pulses of all wavelengths were emitted from the arrow 264. Next, a voltage of 12 V is applied between the photonic crystal slab 11 and the flat plate 12 to bring the flat plate 12 close to the photonic crystal slab 11, and the wavelength 1.4 incident from the arrow 265 is entered. μm Was added to the light emitted from the arrow 264. That is, from the arrow 264, the original wavelengths 1.5, 1.6 and 1.7. μm In addition to a 10 Gb / s optical pulse, a wavelength of 1.4 μm The light pulse was emitted. Thus, Example 17 is that the element having the structure shown in FIG. 25 also functions as an ultra-small wavelength multiplexer that adds an optical signal pulse of a specific wavelength to an optical signal pulse that has been wavelength-multiplexed. Show. This can be controlled by the degree of proximity between the wavelength photonic crystal slab 11 and the flat plate 12 of incident light.
[0122]
(Example 18)
FIG. 26 shows another embodiment relating to the wavelength separator. The overall configuration is the same as that of the wavelength separator shown in FIG. 25, and the photonic crystal slab 11 is a photonic crystal in which the holes 22 form a square lattice.
[0123]
As can be seen by comparing FIG. 25 and FIG. 26, also in Example 18, the photonic crystal slab 11 has two waveguides 261 and 262 made of line defects. The optical pulse signal wavelength-multiplexed from the arrow 263 is incident on the waveguide 261 and is emitted to the arrow 264. The optical pulse signal wavelength-multiplexed from the arrow 265 enters the waveguide 262 and is emitted to the arrow 266. The wavelength-multiplexed optical pulse is introduced from an optical fiber (not shown) that forms an optical communication network, passes through the photonic crystal slab, and is guided to the optical fiber again. In the photonic crystal slab 11, an optical resonator 271 due to a point defect exists at a position indicated by a broken line 12 sandwiched between waveguides composed of two line defects. Here, a broken line 12 indicates a position at which the flat plate 12 is disposed in proximity.
[0124]
Wavelengths 1.5, 1.6 and 1.7 from arrow 263 μm When a 10 Gb / s optical pulse is incident and no voltage is applied between the photonic crystal slab 11 and the flat plate 12, the wavelength is 1.6. μm Only light pulses are emitted to arrow 266 and the other wavelengths 1.5 and 1.7. μm The light pulse is emitted from the arrow 264. This is because the point wavelength optical resonator 271 has a resonance wavelength of just 1.5. μm This is because. Next, when a voltage of 9 V was applied between the photonic crystal slab 11 and the flat plate 12 to bring the photonic crystal slab 11 and the flat plate 12 close to each other, this time, a wavelength of 1.6. μm Only the optical signal of the light is emitted from the arrow 266, and other waves Long light The signal exited from arrow 264. This is because the resonance wavelength of the point defect optical resonator 271 is shifted by the presence of the flat plate 12.
[0125]
Thus, in Example 18, the line defect waveguides 261 and 262 of the photonic crystal slab 11 have a structure having the point defect optical resonator 271 in the region of the plate 12 as shown in FIG. It is shown that it works as an ultra-compact wavelength separator that selects and spatially separates only light pulses having a specific wavelength from the wavelength-multiplexed light pulses by bringing them close to or away from the crystal slab 11. .
[0126]
Similarly to the structure of the seventeenth embodiment functioning as a wavelength multiplexer, the structure of the eighteenth embodiment similarly applies a voltage between the photonic crystal slab 11 and the flat plate 12 or applies a voltage. By controlling the distance between the photonic crystal slab 11 and the flat plate 12 such as not being used, it also functions as a wavelength multiplexer.
[0127]
(Example 19)
The optical functional element according to the present invention can function as an optical switch having a switching function of switching an optical signal transmission path spatially, temporally, or wavelength. FIG. 27 is a perspective view showing an example of the relationship between the photonic crystal slab 11 and the flat plate 12 in the form of an embodiment of the optical switch. The specifications of the photonic crystal slab 11 shown in FIG. 27 are almost the same as those shown in FIG. 8, but in Example 19, a square lattice is used. In the photonic crystal slab 11, a defect waveguide 281 for introducing incident light is formed, which is a coupled defect waveguide coupled to two defect waveguides 282 and 283 that are bent at a right angle. . The flat plate 12 is disposed on the upper surface of the defective waveguide 282.
[0128]
When no voltage is applied between the photonic crystal slab 11 and the flat plate 12, the flat plate 12 is moved away from the photonic crystal slab 11. At this time, the incident light introduced into the defect waveguide 281 is emitted from the respective exits of the two defect waveguides 282 and 283 as emitted light 1 and emitted light 2 with substantially the same intensity. On the other hand, in a state where a voltage is applied, the flat plate 12 approaches the photonic crystal slab 11, so that the light output of the emitted light 1 emitted from the defect waveguide 282 decreases to 10% or less, and along with this, the defect conduction is reduced. The light output of the emitted light 2 emitted from the waveguide 283 increased.
[0129]
This is because when the flat plate 12 approaches the photonic crystal slab 11, the optical coupling of the coupled defect waveguide 282 is weakened, and as a result, the optical output of the emitted light 1 from the defect waveguide 282 side is reduced. Conceivable. This decrease is because reflection occurs at a portion where the optical coupling is weakened, and thus the output on the defect waveguide 283 side increases. Thus, the optical functional device of Example 19 can spatially switch the optical pulse propagating through the defect waveguide. Further, the flat plate 12 is also arranged on the upper surface of the defect waveguide 283 to reduce the light output of the emitted light 2 from the defect waveguide 283 and increase the light output of the emitted light 1 from the defect waveguide 282 side. You can also That is, it is possible to switch to either one of the two defect waveguides. In the nineteenth embodiment, the case of a spatial switch has been described. However, an optical pulse can be switched in terms of time and wavelength by a similar mechanism.
[0130]
(Example 20)
The optical functional element according to the present invention can function as a light emitter or a laser that emits light. FIG. 28 is a perspective view showing the basic configuration of the photonic crystal slab 11 and the flat plate 12 of the optical functional element that functions as a laser. The photonic crystal slab 11 has an active layer 291 composed of 10 quantum well layers made of InP / InGaAsP each having a thickness of 10 nm in the center layer, a P-InP layer 292 on the upper surface, and an N-InP layer 293 on the lower surface. The structure. The central wavelength of light emission from this quantum well is 1.55 μm. Further, the photonic crystal is a hole triangular lattice with holes 22 having a refractive index of 3.5, a lattice interval of 500 nm, a hole radius of 150 nm, and a thickness of 250 nm. The periphery of the slab is composed of air. The flat plate 12 has a refractive index of 1.5, a size of 2 × 1.85 μm, and a thickness of 250 nm. The photonic crystal slab 11 that is the first structure includes a point defect, and the flat plate 12 that is the second structure is provided on the upper surface of the point defect. Since this cross-sectional structure is the same as that described with reference to FIG.
[0131]
When the photonic crystal slab 11 was irradiated with light having a wavelength of 1.1 μm from the outside, light emission from the photonic crystal slab 11 was observed. In the twentieth embodiment, the resonance wavelength of the point defect is controlled by the presence of the flat plate 12, and for example, a wavelength variable light source is realized. At this time, the number of point defects is not necessarily one, and a plurality of point defects may be used.
[0132]
FIG. 29 is a diagram showing the result of detailed calculation of the characteristics by simulation in relation to the light intensity and the wavelength. As shown in the figure, the laser obtained by Example 20 has sharp peaks corresponding to the first resonance and the second resonance. Of particular note is that when the distance d between the photonic crystal slab 11 and the flat plate 12 is changed to 25, 75, and 225 nm, the peak position changes greatly.
[0133]
FIG. 30 is a diagram showing how the peak position changes depending on the distance d between the photonic crystal slab 11 and the flat plate 12. In the figure, the horizontal axis represents the distance d, and the vertical axis represents the resonance wavelength. From the figure, it can be seen that by changing the distance d from 2 to 300 nm, tuning of a very large resonance wavelength of about 15 nm can be performed in both the first resonance and the second resonance.
[0134]
The results shown in FIG. 29 and FIG. 30 were when the thickness of the flat plate 12 was 250 nm, but even if the thickness of the flat plate was increased to 375 nm, no difference was seen in the distance d dependency of the resonance wavelength. A great effect was obtained as well. Further, the results shown in FIGS. 29 and 30 were obtained when the size of the flat plate was 2 × 1.85 μm. However, even if the size of the flat plate is increased to 5 × 1.85 μm, FIG. 29 and FIG. Similar to the results shown in FIG. 30, the resonance wavelength could be greatly changed by changing the distance d between the photonic crystal slab 11 and the flat plate 12. Further, the results shown in FIGS. 29 and 30 were obtained when the refractive index of the flat plate 12 was 1.5, but even when the refractive index of the flat plate was 3.5, the results shown in FIGS. 29 and 30 were obtained. Similarly to the above, by changing the distance d between the photonic crystal slab 11 and the flat plate 12, the resonance wavelength could be greatly changed. Thus, it can be seen that the resonance wavelength can be controlled effectively in any case regardless of the size, thickness and refractive index of the flat plate 12 as the second structure.
[0135]
Furthermore, when a voltage was applied between the photonic crystal slab 11 and the flat plate 12 of this element, the emission wavelength continuously increased from 1.54 μm to 1.55 μm. This is because the distance between the photonic crystal slab 11 and the flat plate 12 is decreased by applying a voltage, thereby increasing the resonance wavelength of the defect. As described above, it is shown that the photonic crystal slab 11 as the first structure includes a point defect, and the flat plate 12 as the second structure is disposed on the photonic crystal slab 11 to form a wavelength-tunable light emitting element. It was.
[0136]
Here, an example of a light emitting element using an optical pump is shown as the light emitting element. However, this configuration is also effective in the case of a current injection type light emitting element. Although the light emitting element is generally described here, the present configuration is sufficiently effective in the case of a laser element that can obtain coherent light.
[0137]
In Example 20 shown above, the size of the flat plate 12 as the second structure was larger than the unit cell including the point defect of the photonic crystal slab 11. When the size of the flat plate 12 is approximately the same as the size of the unit cell including point defects, the resonance wavelength does not change even if the distance d is changed, and the resonance line width increases rather as the distance d is decreased. The result to be obtained. FIG. 31 is a diagram showing the characteristics of the light emitting device when the size of the flat plate 12 is approximately the same as the size of the unit cell including point defects. The vertical axis represents the normalized light intensity, and the horizontal axis represents the wavelength (μm).
[0138]
The structure obtained as a result of FIG. 31 is a hole triangular lattice having a lattice spacing of 440 nm, a hole radius of 150 nm, and a thickness of 220 nm of the photonic crystal slab 11. The flat plate 12 has a refractive index of 3.5, a size of 880 nm × 880 nm, and a thickness of 220 nm. Thus, when the flat plate 12 covers the lattice defect of the photonic crystal slab 11 about twice as large as the lattice spacing of the photonic crystal slab 11, just as shown in FIG. This corresponds to the fact that the Q value of the resonator due to the defect can be controlled by changing d. First, when the distance d between the flat plate and the photonic crystal slab was set to a sufficiently large value of 200 nm or more, by injecting current into this quantum well, laser oscillation occurred at the point defect portion, and coherent light was obtained. . Next, the laser oscillation stopped when the flat plate was brought close to the photonic crystal and the distance d was set to 100 nm. This is because by reducing the distance d, the Q value is reduced and laser oscillation cannot be performed. Thus, it was shown that laser oscillation can be turned on and off by changing the distance between the flat plate and the photonic crystal slab. In addition, an element using the Q value of the resonator due to the defect, such as control of the propagation speed of the coupled defect waveguide made of a photonic crystal using this, can be manufactured.
[0139]
Although a laser using a photonic crystal is introduced in [Patent Document 4], an example of controlling the characteristics of the light emitting element by controlling the flat plate 12 as in the present invention is not disclosed.
[0140]
(Example 21)
As described above, the present invention has a first structure made of a photonic crystal and a second structure close to the first structure, and by changing the relative positions of the two, In the following, specific application forms in an optical communication system or an optical application system will be described.
[0141]
FIG. 32 is a diagram for explaining an optical module introduced into an optical communication system in which an optical functional element of the present invention and a mechanism for controlling the function are simultaneously provided. The module shown in FIG. 32 includes the element 331 shown in FIG. 8, and the fiber 332 and the lens 333 disposed on both sides of the element 331 on the optical axis. Further, the device 334 includes a device 334 for applying a voltage between the photonic crystal slab 11 of the element 331 and the flat plate 12 (not shown). In this example, a control signal is sent from a receiving device (not shown) that receives an optical signal after passing through the module, and a voltage is applied to the device from a device 334 that applies a voltage to the device 331, and the optical signal is turned on / off. I do.
[0142]
FIG. 33 is a diagram for explaining an optical transmission system in which the optical functional element of the present invention is used in any one or a plurality of locations of a transmitter, a repeater, and a receiver. This is a wavelength division multiplexing optical transmission system of 40 Gbps / channel using the optical functional element exemplified in the first embodiment. This system includes a transmitter 341, a transmission fiber path 342, and a receiver 343. The transmission apparatus 341 includes an electric-optical converter 344, a wavelength multiplexer 345, and an optical transmission amplifier 346 for each wavelength (channel). However, these are sufficient as usual. The wavelength used is a band centered at 1.55 μm. A dispersion shifted fiber 342 is used for the transmission fiber path, and the transmission distance is 80 km. The receiving device 343 includes an optical receiving amplifier 347, a wavelength separator 348, a dispersion compensator 349, and an optical-electrical converter 340. The multiplexed optical pulse is divided into wavelengths by a wavelength demultiplexer 348, and optimum dispersion compensation is performed in each channel by a dispersion compensator 349.
[0143]
In this configuration, the wavelength multiplexer 345 is configured by using the wavelength multiplexer described in Example 17 or Example 18 in multiple stages. The wavelength separator 348 is also configured by using the wavelength separator described in Example 17 or Example 18 in multiple stages. As a result, the wavelength multiplexer 345 and the wavelength separator 348 can be configured to be very small, and the system can be configured compactly.
[0144]
FIG. 34 is a diagram for explaining an example in which an optical recording apparatus and system are configured using the optical functional element of the present invention.
[0145]
The optical bit writing / reading apparatus and system using the wavelength tunable semiconductor laser 351 manufactured by the current injection type described in Example 20 are illustrated. In the figure, the light from the laser 351 is condensed via a lens 352 onto a rotating disk 353 that records an optical bit. The disk is rotated by a drive motor 354. This disk is coated with a material having a hole burning effect, and wavelength multiplex writing is possible by changing the wavelength. A material having a hole burning effect is a material that can record optical signals having different wavelengths in the same place. That is, for example, when light beams with wavelengths λ1 and λ2 are irradiated to the same place of a film made of a material having a hole burning effect, the light transmittances of the wavelengths λ1 and λ2 of the film at that place change. For this reason, by changing the wavelength at the same place, optical recording corresponding to each wavelength becomes possible, and wavelength multiplex writing can be performed.
[0146]
With such an apparatus configuration, a system capable of efficiently and compactly performing wavelength division multiplexing writing and reading by signal control from the control system 355 was constructed. This is because the semiconductor laser 351 is made of a photonic crystal, so that the apparatus can be miniaturized.
[0147]
【The invention's effect】
As described above, according to the present invention, it is possible to realize an optical functional element using an ultra-compact and highly functional photonic crystal with a relatively simple configuration. Further, according to the present invention, an inexpensive and highly reliable optical transmission system or optical recording system can be constructed.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a basic configuration of an optical functional element of the present invention.
FIG. 2 is a diagram showing an example of what is called a two-dimensional photonic crystal among photonic crystals.
3 is (ε1) in the structure of FIG. ^1/2 The figure which shows the photonic band figure with respect to TM mode and TE mode when setting = 3.5, (epsilon) 2 = 1, and r / a = 0.45.
FIGS. 4A and 4B are diagrams showing examples of a band structure of a photonic crystal slab 11 obtained by simulation. FIGS.
5A is a plan view showing the concept of the configuration of an embodiment of an optical functional element according to the present invention, and FIG. 5B is a cross-sectional view taken in the direction of the arrow at the AA position.
FIG. 6 shows the results obtained by simulating the transmittance and phase change of light propagating through the photonic crystal slab 11 by changing the distance between the upper surface of the photonic crystal slab 11 and the flat plate 12 in the configuration shown in FIG. FIG.
FIG. 7 is a diagram in which the transmittance of light propagating through the photonic crystal slab 11 is obtained by simulation.
8 is a perspective view showing the structure of the produced optical functional element based on the structure corresponding to FIG.
9A to 9F are cross-sectional views (including a partial plan view) showing a main part of an example of a process for realizing the structure of the optical functional element shown in FIG.
FIGS. 10A to 10G are diagrams showing a manufacturing process in the case where GaAs is used as a material of a photonic crystal slab which is a first structure and Si is used as a flat plate which is a second structure. .
FIGS. 11A to 11C are cross-sectional views showing a main part of an example of a process when a GaAs substrate 91 itself for forming a photonic crystal slab 11 is used as a second structure. FIGS.
FIGS. 12A to 12H show other processes of the manufacturing process when GaAs is used as the material of the photonic crystal slab as the first structure and Si is used as the flat plate as the second structure. The figure which shows an example.
FIGS. 13A to 13E are diagrams showing an example in which an element structure is manufactured by a bonding method similar to that in FIG. 12, but the flat plate 12 which is the second structure is realized in another form.
FIGS. 14A to 14E are examples of manufacturing a device structure by a bonding method similar to that in FIG. 12, but realizing the flat plate 12 as the second structure in another form. FIG.
15 is a perspective view showing an example of Example 7. FIG.
FIG. 16 is a perspective view showing an embodiment in which the first structure of the optical functional element according to the present invention is a one-dimensional photonic crystal.
FIG. 17 is a perspective view showing a concept of an embodiment when the present invention is realized by a three-dimensional photonic crystal.
18 is a plan view of a two-dimensional photonic crystal slab 11 including a line defect 181. FIG.
FIG. 19 is a plan view of the two-dimensional photonic crystal slab 11 when the line defect is different from FIG.
20 is a perspective view showing a configuration of an optical functional element according to Example 12. FIG.
FIGS. 21A and 21B are diagrams illustrating an example of an optical functional element that changes a relative position of a first structure and a second structure using a microactuator using a comb-tooth electrode; FIGS. .
22A to 22B are diagrams showing examples of optical functional elements in which comb teeth themselves function as a flat plate 12; FIG.
FIG. 23 is a view showing another example in which the flat plate 12 is moved up and down the photonic crystal slab 11 by a microactuator.
FIG. 24 is a perspective view showing the configuration of Example 16 employing a scratch actuator.
FIG. 25 is a top view of an embodiment of the photonic crystal slab 11 made of P-doped Si that constitutes the wavelength separator.
FIG. 26 is a top view of a photonic crystal slab 11 showing another embodiment relating to a wavelength separator.
FIG. 27 is a perspective view showing an example of the relationship between the photonic crystal slab 11 and the flat plate 12 in the form of an embodiment of the optical switch.
FIG. 28 is a perspective view showing the basic configuration of a photonic crystal slab 11 and a flat plate 12 of an optical functional element that functions as a laser.
29 is a graph showing the result of detailed calculation of the characteristics of the laser shown in FIG. 28 by simulation in relation to the light intensity and the wavelength.
30 is a diagram showing how the peak position changes depending on the distance d between the photonic crystal slab 11 and the flat plate 12 of the laser shown in FIG. 28;
31 is a graph showing characteristics of a light-emitting element when the size of a flat plate 12 of the laser shown in FIG. 28 is approximately the same as the size of a unit cell including point defects.
FIG. 32 is a view for explaining an optical module introduced into an optical communication system in such a manner that the optical functional element of the present invention and a mechanism for controlling the function are simultaneously provided.
FIG. 33 is a diagram illustrating an optical transmission system in which the optical functional element of the present invention is used in any one or a plurality of locations of a transmitter, a repeater, and a receiver.
FIG. 34 is a diagram illustrating an example in which an optical recording apparatus and system are configured using the optical functional element of the present invention.
[Explanation of symbols]
11: Photonic crystal slab, 12: Flat plate, 12a, 12b: Notch, 13: Drive device, 14: Operating rod, 22: Hole, 41: Light line, 42: Dispersion curve, 71: Substrate, 72, 74 : SiO ₂ Layer: 75: Ridge type waveguide, 76, 77: Electrodes 77, 78, 79: Lead wire, 91: GaAs substrate, 92: AlAs layer, 93: GaAs layer, 95: Si substrate, 96: SiO ₂ Layer, 99: back surface of Si substrate 95, 97, 98: Si layer, 98a, 98b: notch, 161: SiO ₂ Substrate, 162: Si layer and SiO ₂ 1-dimensional photonic crystal in which layers are laminated, 171: three-dimensional square material laminated photonic crystal, 181 and 182: line defects in the photonic crystal, 220: microactuator using comb electrodes, 221: frame portion, 223 : Fixed electrode, 224: movable electrode, 225, 227: leaf spring, 229: movable shaft, 237a, 237b: spring piece, 241: plate, 250: scratch actuator, 251: conductive substrate, 253: conductive movable Plates 253, 255: claws, 261, 262: waveguide, 263, 265: incident light, 264, 266: outgoing light, 271: optical resonator, 281, 282, 283: defect waveguide, 291: active layer 291 292: P-InP layer, 293: N-InP layer, 331: element, 332: fiber, 333: lens, 334: applying voltage 340: optical-electrical converter, 341: transmitting device, 342: transmission fiber path, 343: receiving device 343, 344: electric-optical converter, 345: wavelength multiplexer, 346: optical transmission amplifiers 346, 347: Optical receiver amplifier, 348: wavelength separator, 349: dispersion compensator, 349, 351: wavelength tunable semiconductor laser, 352: lens, 353: rotating disk, 354: drive motor.

Claims (15)

A first structure composed of a photonic crystal, a second structure composed of a photonic crystal adjacent to the first structure, and a relative position of the first structure and the first structure Means for controlling the distance to the second structure to a predetermined value, wherein the photonic crystal is composed of a plurality of media having different refractive indexes, and the plurality of media constituting the first structure And the region composed of the plurality of mediums constituting the second structure are always separated from each other , and the change in the relative position is a photo constituting the first structure. An optical functional element characterized in that the characteristic of the first structure is changed by changing the band structure of the nick crystal . The optical functional element according to claim 1, wherein a plurality of second structures are arranged with respect to the first structure and each is controlled independently. The first structure, the one-dimensional photonic crystals, according to claims 1 is either two-dimensional photonic crystal and a three-dimensional photonic crystal including a photonic crystal slab in any one of claims 2 Optical functional element. 4. The optical functional element according to claim 1, wherein the photonic crystal including a defect in the photonic crystal is the first structure. 5. The optical function element according to any one of claims 1 to 4, wherein the second structure is a dielectric, a semiconductor, a metal, or a composite thereof. The optical functional element according to any one of claims 1 to 5, wherein the relative position of the first and second structures is changed by a microactuator including a micromechanical electrical system. A two-dimensional photonic crystal slab including a plurality of line defects formed in the first structure and the second structure are disposed close to each other, and the second structure is disposed between the plurality of line defects. By controlling the wavelength, a wavelength separator that selects only an optical signal of a specific wavelength from the wavelength-multiplexed optical signals that propagate through one line defect and spatially transfers to another line defect or propagates through one line defect any one of claims 1 to function as a wavelength multiplexer to the optical signal wavelength-multiplexed optical signal specific optical signal having a wavelength propagating other line defect in the optical signal in addition to the optical signal of claim 6 1 The optical functional element according to Item. Dispersion compensation element for shaping optical pulse shape using wavelength dependency of group velocity of light corresponding to distance between first structure and second structure close to first structure The optical functional element according to claim 1, which functions as: 2. The optical modulator having a function of changing an intensity or a phase of an optical signal corresponding to a distance between the first structure and a second structure close to the first structure. The optical functional element according to claim 6 . 2. The optical signal transmission line functions as switching for spatially, temporally, or wavelength-switching corresponding to the distance between the first structure and the second structure adjacent to the first structure. The optical functional element according to claim 6 . In the two-dimensional photonic crystal slab containing the point defects in the first structure is formed, a laser using the optical functional device disposed proximate the second structure on the upper surface of the two-dimensional photonic crystal slab The two-dimensional photonic crystal slab includes an active layer for functioning as a laser, and the distance between the upper surface of the two-dimensional photonic crystal slab and the second structure is controlled to oscillate the laser. The laser comprising the optical functional element according to any one of claims 1 to 6, wherein the wavelength is controlled. The distance between the upper surface of the two-dimensional photonic crystal slab and the second structure is controlled by setting the point defects formed in the first structure and the second structure to be approximately the same size. The laser according to claim 11, wherein the Q value of the resonator due to defects is controlled. The optical functional element according to any one of claims 1 to 10, having a function corresponding to a distance between the first structure and a second structure close to the first structure. An optical module comprising a mechanism for controlling functions. The optical functional element according to any one of claims 1 to 10, having a function corresponding to a distance between a first structure and a second structure close to the first structure. An optical transmission system characterized by being used in one or a plurality of locations of a transmitter, a repeater, and a receiver. The optical functional element according to any one of claims 1 to 10, which has a function corresponding to a distance between the first structure and a second structure close to the first structure. An optical recording apparatus and system.

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