二维光子晶体腔及通路加/减滤波器

Mode of execution

The present inventors first survey 2D is not characteristic of the photonic crystal by fig. 12 shown in a voltage of the cavity of the defect, but is a point defect donor the cavity. As mentioned above, the defect donor comprising one or a plurality of lattice point, and perforation in scattered in these lattice point.

The study of so far includes only a single lattice point is a point defect, in view of its structure from the point of view of simplicity, their easy electromagnetic decomposition and has minimum size. This means that for donor , the point defect comprising a large number of lattice point so far has not been extensive research. In such cases the inventors have studied the donor include a large amount of lattice point of the characteristic of a point defect.

Figure 13 is partial plan view of one of the lattice point comprising a large number of point defect donor 2D photonic crystal. In the 2D in photonic crystal, the perforation 2 is arranged in the form of the section 1 of the lattice at the vertex of the triangle. Figure 13A in the point defect 4 comprising a line segment form of the three lattice point adjacent to each other, in these lattice point disposition in the perforation 2. At the same time, Figure 13B in the point defect 4 comprises in a triangular geometry of the three lattice point adjacent to each other, in these lattice point disposition in the perforation 2. In other words, the point defect can be formed 4 includes a large number of adjacent lattice point one-dimensional each other, or may be formed of the point defect 4 includes a large number of adjacent lattice point two-dimensional to each other.

The use of the limited bad time domain (FDTD) method known (see Japanese pending Patent application JP2001-272555), the present inventors to include a large amount of lattice point of the point defect donor electromagnetic analysis, and it was found that among them comprising one or two lattice point of a point defect donorthe cavity compares , utilize and include three or more lattice point of a point defect donor cavity obtain higher Q value. Needless to say, if the number of lattice point in the point defect is too many, the number of the oscillation mode is not ideal, the quantity of the good lattice point is six or less.

For example, the chart 13A the cavity is shown, in the basic structure in a simple, Q=5200, and when combined with a waveguide, filter can produce approximately 2600 of the Q factor, the light output from the cavity in the FWHM is about 0.6 nm. Furthermore, by taking into account the approximately 100GHz, wavelength peak spacing of approximately 0.8 nm of the multi-channel signal crosstalk in WDM optical communication , to further improve the Q factor.

Figure 1 is plan view of the invention used for explanation in the cavity is limited. In Figure 1 the shown 2D photonic crystal of the triangle vertices defined in the two-dimensional lattice, lattice point place formed in the same shape and the smooth tubular perforated 2. The triangular lattice in the interval between the adjacent lattice point (lattice constant) for said a. Figure 1 show in donor comprising a point defect of the line segments adjacent to each other in the form of the three lattice point within the range; in these lattice point spread in the perforation 2.

According to the invention the main point defect donor is characterized in that at least one of the most close to the point defect to form a perforation 2 away from its corresponding lattice point a predetermined distance. In Figure 1 in, at right angles to each other the Г-X and Г-J shaft said perforation 2 and is separated from its corresponding direction of the lattice point. In the Figure 1 also use the identification l, m and n mark closest to the point defects of the perforations of the correspondingly formed in lattice point 2 from the direction of the lattice point. Should know that, because Figure 1 shown in the direction of displacement of the is only for the purpose of the representation, so perforation 2, will naturally move on any selected direction.

The following the most close to the perforations of the point defect 2 leave their corresponding to the state of the original lattice point expressed as "displacement = (l, m, n)". For example, "displacement = (0.1a, 0 . 2a, 0.3a)" means that the corresponding to the representation of the perforation of the arrow indexed l of the lattice point removed from their corresponding 0.1a, also means that the same corresponding to the perforation of the arrow mark m of the lattice point removed from their corresponding 0.2a, and corresponds to the n-indexed of the perforation of the arrow away from their corresponding lattice point 0.3a.

By fig. 1 shown in the defect donor spot 4 Q factor of the cavity and the electric field pattern (radiation pattern) excited by the FDTD method. The slice excitation parameters the same as the silicon, the wavelength is set to approximately 1.55 the λ  m (is usually used for optical communication); the lattice constant is set to a the 0.42  m; slice 1 is set to the thickness of the 0.6a; perforation 2 is the cross-sectional radius 0.29a.

For the simulation under these conditions (l, m, n) = (0, 0, 0) of the case, access to 5200 Q factor of; Figure 2 that this case perpendicular to the slice 1 looks from the cavity in the direction of 4 the radiation pattern of the light emitted. For similar analog (l, m, n) = (0, 0, 0 . 15a) of the case, access to 43,000 Q factor of; Figure 3 mark in this case from the cavity in the radiation pattern of the light emitted.

From these analog experiment can know, in the form of line segments adjacent to each other of the three lattice point in the point defect donor , the two ends of the line adjacent the perforations of the leave from its corresponding lattice point 0.15a the distance from Q factor of 5200 rapid increase to 43,000, at the same time, from Figure 2 and 3 can know of the comparison of, reducing the radiation angle of the light.

In another case, by making the (l, m, n) = (0, 0, 0 . 20a) and the displacement n is relatively large, can obtain more high Q=100,000; Figure 4 expressed in this case from the cavity in the radiation pattern of the light emitted. With the Figure 3 compared with, in the Figure 4 in relatively large radiation angle of the light, and Figure 4 in the main emission of the centre above or below level of the light beam (first beam) is very significant. This means that with the increase of the distance, wherein the increase of the distance, the most close to the point defect 4 perforation 2 away from its corresponding lattice point, also tending to increase the Q factor, but considering the from cavity 4 in the radiation angle of the light emitted, the displacement should not be very large.

See Figure 5, is a graph in said Figure 1, the pilot the defect J Г the displacement of the direction between the n the relation curve of the Q factor. In this curve, the horizontal axis represents the displacement of the lattice constants a calibration of n, while the vertical axis expresses Q factor. From Figure 5 can know, to increase the displacement by increasing the Q factor of n there is a limit. Specifically, when the displacement n is increased to 0.20a time, Q factor also index increase, reaching the maximum value 100,000; but if displacement n further increased, the Q factor is on the contrary is dramatically reduced.

In Figure 6 is shown in the curve of the displacement n the side emitted light beam with host the relationship between the power of the, such as Figure 4 clearly seen in. In this curve, the horizontal axis represents the displacement of the lattice constants a calibration of n, while the vertical axis denotes the transmit power level of the transmitted beam. In Figure 6 it is obvious that in the, comprising level in the radiation angle of the emitted beam displacement for n 0.15a under the condition of the minimum, and the bit shift n 0.25a the maximum under the condition.

Removed from the perforation of the lattice point (l, m, n) = (0, 0, 0) compared with the displacement (l, m, n) = (0.11a, 0 . 11a, 0) is obtained under the condition of high Q=11,900; Figure 7 represents in this case from the cavity pattern of radiation of the light emitted. From the Figure 3 condition shown in (l, m, n) = (0, 0, 0) can be compared with known, in fig. 7 in the radiation angle of emission of light is relatively small.

See Figure 8, this Figure is similar to Figure 1, said at least one not only corresponding to the closest to the point defect 4 of the perforations of the lattice point 2, and at least one close to the lattice point corresponding to the time of perforation 2 have left lattice point the situation of the predetermined distance. Although the Q factor of the cavity is the most effective means of the as described above corresponds to the close to the point defect 4 away from the perforations of the lattice point of its corresponding lattice point a predetermined distance, but the amount of the corresponding to the time the field is close to the perforations of the lattice point 2 from its corresponding lattice point a predetermined distance also produces the effect of the replacement of the Q factor.

See Figure 9, a scanning electron photomicrograph (SEM) represent the actual manufacturing 2D a portion of the photonic crystal. The 2D photonic crystal structure parameter-comprises a section 1 of the material, two-dimensional lattice constant, the perforation 2 and the diameter of the point defect 4 includes the number of the lattice point of the front-and the layout of the analog case, while the displacement is set as (l, m, n) = (0, 0, 0 . 15a).

Adopt the electron beam to photo-etching and reactive ion etching (see the Japanese pending Patent application JP2001-272555) manufacturing Figure 9 to the photonic crystal as shown in, and, in addition to point defect 4 outside, also includes a linear waveguide 3. This means that from the point defect 4 cavity sum linear waveguide 3 of a predetermined wavelength of light transmission between, to thereby allow the device used as a channel add/drop filter.

In Figure 10 is shown in the curve of the said containing different wavelengths of light actually entering the Figure 9 the waveguide 3 is shown under the condition of, from the cavity 4 in the vertical of the light emitted in the section 1 in the direction of the relationship between intensity and wavelength. Specifically the horizontal axis represents wavelength (nm), the vertical axis represents the light intensity (arbitrary units). From Figure 10 it is apparent that, included in the fig. 9 is shown in a channel add/drop filter cavity 4 enters the waveguide 3 from the wavelength of the light in the wavelength peak separation of approximately 1578.2 nm, with the greatest halfwidth (FWHM) of about 0.045 nm emission of the light, and has the above-mentioned simulation test as expected is about 35,100 high-Q factor. Can know, this inventor high wave length can provide a resolution of the channel add/drop filter.

Should know that, although in fig. 9 the channel add/drop filter in a near a waveguide only set up a cavity, but can be in the optical communication processing a plurality of different wavelengths with each other channel of the multi-channel add/drop filter by the approximation to natural can be along a single waveguide is provided with a plurality of different oscillation frequency of a cavity. Furthermore, through the optical fiber is arranged on the end surface of the cavity is similar to the face 4, the perpendicular to the slice 1 from the cavity in the direction of 4 the launch place light entering the optical fiber. Furthermore, the photoelectric sensor is set to a substantially face the cavity 4, can be received from the cavity as the modulation of the light emitted by the light intensity. Those of skill in the art will understand, can be in the cavity 4 and the optical fiber end face or a photoelectric sensor is inserted in between the collimating lens (collimator).

See Figure 11, this Figure is another embodiment of the present invention in a channel add/drop filter of the strabismus Figure. Although Figure 11 the channel add/drop filter and Figure 9 similar shown, in the Figure 11 intermediate cavity 4 is disposed adjacent the 1st linear waveguide 3a, and 2nd waveguide 3b is disposed adjacent the cavity 4. In this case, as mentioned above, can be in the cavity 4 optical signal of a specific wavelength in the waveguide 1st 3a separating the optical signal in, but for neighbouring cavity 4 is set to be the 2nd waveguide 3b, separate optical signal from the cavity 4 does not enter the section 1 of the vertical plane, but enter the 2nd waveguide 3b. This means that in adopting 2D photonic crystal channel add/drop filter, passes through a waveguide of a given optical signal of wavelength in the optical signal can be selectively into another waveguide.

Relatively large refractive index can be ideally used as the material of the section of the photonic crystal, because it must limit the light along its thickness. In the above is shown in this embodiment, the slice Si (silicon), but can be adopted in which other than the material of the: group IV semiconductor, such as Ge, Sn, and SiC C; III-V group semiconductor compound, such as GaAs, InP, GaN, GaP, AlP, AlAs, GaSb, InAs, AlSb, InSb, and InGaAsP AlGaAs; II-VI group semiconductor compound, such as ZnS, CdS, ZnSe, HgS, MnSe, CdSe, ZnTe, MnTe, HgTe and CdTe; oxide, such as SiO₂, Al₂ O₃ and TiO₂; silicon nitride; various types of glass, such as soda lime glass; and organic matter, such as Alq₃ (C₂₇ H₁₈ AlN₃ O₃). These sliced and formed in the photonic crystal of the magnification of the optical signal in the case of ideal Er can be incorporated.

Preferably, the slice 1 the refractive index of the refractive index greater than that of air, in particular to 2.0 or more, more preferably 3.0 or more. Those of skill in the art will know that, although in the above-mentioned embodiment the perforation 2 there is air within, but of course can also be in the perforation 2 is filled in the section 1 of a material of low refractive index. Such substances such as the conductor gathers thiopheneglyoxylic can be used as the low refractive index material. Furthermore, slice 1 is provided with a two-dimensional lattice is not limited to the triangular lattice, can also be configured to any other selected regular two-dimensional lattice. Perforation 2 smooth shape the cross section is not limited to, can also be other shape; or can be along the shape of the slice thickness change section.

As previously stated, the invention in 2D photonic crystal is provided in the cavity of the Q factor is increased, and the combination of such cavity and the waveguide, which makes it possible to obtain better with high wavelength resolution channel add/drop filter.

Although some embodiments has selected only the interpretation of this invention, however, the field of the technical personnel from the front side can be in the description it is apparent that, without departing from the invention defined by the scope of the claim can be carried out on the premise of various changes and modifications. Furthermore, according to the implementation of the invention for only the purpose of illustration, does not constitute a limit of this invention, the scope of the present invention is attached to the right of the defined requirements and their equivalents.