JPS5810705A - Photocoupler - Google Patents

Abstract

PURPOSE:To make it possible that an optical waveguide itself functions as an optical directional coupler or an optical switch, by arranging plural optical waveguides in parallel on the surface of a substrate and forming a transparent material having the optically induced refractive index changing characteristics instead of a part of the clad layer interposed between core layers of adjacent optical waveguide. CONSTITUTION:A part of a clad layer 12 interposed between core layers 11 and 14 of two optical waveguides provided on a substrate 10 is eliminated, and a transparent material 13 having the optically induced refractive index changing characteristics is formed in this part. When a signal light A is made incident to the core layer 11, the light A is led out partially as an output light A' as it is but the light propagated through the core layer 11 is coupled to the core layer 14 of the adjacent waveguide partially by the transparent material 13 to lead out an output light B. Since the refractive index of the transparent material 13 is changed by the light irradiation, the degree of coupling to the adjacent waveguide 14 is controlled by a light C' irradiated to the transparent material 13.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical coupler applied to an optical directional coupler or an optical switch.

Conventionally, optical directional couplers include those in which two leading waveguides with similar propagation constants are adjacent to each other at a very close interval, as shown in Figure 1 (5), and coupling by a Y-branch as shown in Figure 1). There is a vessel. However, in the case of FIG. 1A, the adjacent spacing must be set to the wavelength of the incident light, and the coupling efficiency depends on the propagation constant of the O optical waveguide and the adjacent distance e, respectively.

This optical directional coupler has the disadvantage that it is difficult to maintain the above-mentioned adjacent spacing. Furthermore, in the case of FIG. 1), there is a drawback that the coupling efficiency of the branch where the angle θ shown in FIG. 1 becomes large becomes small.

On the other hand, there are almost no known useful optical switches used in optical waveguides.

One of the few switches for optical waveguides is shown in FIG. This optical switch includes a waveguide formed by forming a film 2 having light-induced refractive index change characteristics on a substrate 1, a rutile prism 6, and a means for irradiating light 4 that causes a refractive index change. The incidence of the optical signal 4 is adjusted at the interface between the prism 5 and the film 2 based on the relative relationship between the refractive index and the change in the refractive index of the film 2. This optical switch uses a prism and is difficult to array.
Another drawback is that the optical waveguide itself does not have an optical switch function.

The present invention eliminates the drawbacks of the conventional optical directional couplers and optical switches described above, and allows the optical waveguide to function as an optical directional coupler or an optical switch. Moreover, it is an object of the present invention to provide an optical coupler capable of forming an array of these elements.

In order to achieve the above object, the optical coupler of the present invention has a plurality of optical waveguides, each consisting of a core layer and a cladding layer, arranged in parallel on a substrate surface, and the cladding layer is sandwiched between the core layers of adjacent optical waveguides. A transparent body having a light-induced refractive index change characteristic is formed in place of a part of the optical waveguide, and this transparent body is irradiated with excitation light to optically couple adjacent optical waveguides.

The present invention will be described in detail below with reference to an embodiment shown in the drawings.

FIG. 3 is a sectional view of an optical directional coupler showing an embodiment of the present invention. A core layer 11, a cladding layer 12. Core layer 14. The cladding layers 15 are sequentially stacked to form two stacked optical waveguides. In each laminated layer, the refractive index of the core layer is adjusted to be greater than the refractive index of the cladding layer. Also, a part of the cladding layer 12 sandwiched between the core layers of the two optical waveguides is removed,
In place of this, a transparent body 15 having light-induced refractive index change characteristics
is formed. The refractive index of this transparent body 13 changes when irradiated with light.

In FIG. 6, when the signal light A is incident on the core layer 11,
Some of the light rays are directly led out as output light A', but due to the transparent body 13, part of the propagating light A of the core layer 11 is also coupled to the core layer 14 of the adjacent waveguide, and output light B is led out. The degree of coupling to adjacent waveguides is adjusted by C irradiated onto the transparent body 16. Note that the excitation light may be irradiated onto the transparent body 13 by making it perpendicular to the waveguide as shown in C.

Currently, chalcogen elements S, Ss
, As-S as a compound containing Te.

As-8e-Ge, As-8e-8-Ge, etc. are well known.

Furthermore, it has been confirmed that PLZT represented by (Pb, L2) (Zr, Ti)0+ also exhibits the same characteristics.

FIG. 2 shows the refractive index change characteristics of materials having these photo-induced refractive index change characteristics.

The refractive index of a material that has not undergone any history is set to no, and the bandcap of this material is set to E! shall be. Here hw≧E!
Band-capped light BGL is defined as light having a photon energy of
If we define Ky light as non-bandgap light LBGL, then
When a material with a refractive index of no. Also, LBGL is a material with a refractive index of no.
When irradiated with n, the refractive index increases and reaches n2.

In this case, the relationship is n 1) n 2. When a material that has reached a refractive index n1 is irradiated with LBGL, the refractive index decreases to n2. Conversely, when a material with a refractive index of n2 is irradiated with BGL, the refractive index increases to nl. Note that the refractive index n1 decreases to n3 when the light irradiation is stopped and left as is. These refractive indexes n3 and nl
, n2 is n2<n3<nl.

From the above, by irradiating light, the refractive index n can be dynamically changed in the range of n 2 (n (n i), and in the static state, the refractive index can be changed in the range of n 2 (n (n Steady state.

You can maintain your condition. Furthermore, by alternately irradiating LBGL and BGL, the refractive index can be reversibly adjusted within the range n 2 < n < nl. Furthermore, LBGL and BG
By simultaneously irradiating L, a refractive index intermediate between n2 and n3 can be obtained from K.

In FIG. 5, if the refractive index of the core layer 11.14 is n4, this refractive index n4 is set so that n2 (n4<n3) with respect to the refractive index characteristics shown in FIG. If the refractive index direction of the portion 13 is n2 (n (n4), the optical waveguide satisfies the waveguide condition, so as mentioned earlier, the light ray A transmitted through the core layer 11 is guided like the light ray A'. On the other hand, when n4×n, the waveguide conditions are no longer defined.

The light propagating through the core layer 11 is divided into a component guided through the core layer 11 like a light ray A' and a component guided like a light ray B from the core layer 11 to the core layer 14 of the adjacent waveguide. In addition, the waveguide condition defined by the critical angle θC of the optical waveguide is expressed as follows. As the refractive index n of the transparent body 13 changes, θC changes, so the amount of transmitted light within the core layer 11 also changes. do. Note that the relationship n(n4 can be achieved by irradiating the transparent body 13 with LBGL as the ray C, as shown on the left, and the relationship +n4<n can be achieved by irradiating BGI as the ray C. Then, LBGL and B
By irradiating the transparent body 13 with a constant amount of GL and adjusting the irradiation time of the LBGL and BGL, an arbitrary intermediate refractive index can be obtained, and the amount of optical coupling can be adjusted.

FIG. 5 is a plan view of an optical directional coupler showing another embodiment of the present invention, and FIG. 6 is a sectional view thereof.

In the optical directional coupler shown in FIGS. 5 and 6, two optical waveguides each consisting of a core layer 21, 24 and a cladding layer 22.25 are provided on the same plane on a substrate 20. Of course, both waveguides are coupled by a transparent body 23 having a light-induced refractive index change characteristic. Since the operation can be considered similar to that shown in FIG. 3, the explanation will be omitted.

Next, as an example, a case of configuring an optical switch array will be described. In the directional coupler shown in FIG. 5, if the amount of transmitted light of the derived light A becomes 0, it can be used as an optical switch. However, in the case of FIG. 5, it is difficult to make the output light A completely zero. Therefore, it is desirable to use the optical switches shown in FIGS. 7 to 9.

The optical switch shown in FIG. 7 has a bent part in one of the two core layers 31 and 34, and a light-induced refractive index change characteristic is created between both core layers including this bent part. A transparent body 33 having a transparent body 33 is disposed. When this transparent body 33 is irradiated with excitation light, the light ray A incident on the core layer 31 is transmitted as a light ray B to the core layer 34 . Furthermore, when the light propagates through the core layer 31, most of it becomes opaque light and goes out of the core layer.

Furthermore, the light ray A propagated through the core layer 31 undergoes multiple reflections due to the bending portion, so that the light ray A is lost and is not transmitted to the end of the core layer 31. Eventually, the propagation of the rays can be switched from the core layer 31 to the core layer 34.

In the optical switch shown in FIG. 8, the core layer 31 is provided with a bent portion, and the core layer 34 is also provided with a bent portion with a larger radius than the bent portion of the core layer 31, and includes one and both bent portions.
．． A transparent body 33 having a light-induced refractive index change characteristic is provided between 34 and 34. Core layer! Since +4 also has a bent portion, the incident light beam A of the core layer 51 is easily taken into the core layer 34.

The optical switch in FIG. 9 shows an example in which two bent core layers are laminated. One end of the substrate 40 is polished and squared, and then a core layer 41. Cladding layer 42. Core layer 44.
The cladding layers 45 are sequentially laminated. Further, 43 is a transparent body which has a 1-segment when the refractive index changes due to light induction. By squaring one side of the substrate 40 in this way, the seventh
It is possible to obtain the same effect as the optical switch shown in FIGS. In the above embodiment, two optical waveguides are installed in parallel, but two optical waveguides may be installed in parallel.

Further, in the above embodiment, the leading waveguide for optical signals and the optical waveguide for excitation light are used together, but a waveguide for excitation light may be provided in addition to the waveguide for optical signals.

As described above, according to the optical coupler of the present invention, a plurality of optical waveguides are arranged in parallel on the substrate surface, and instead of a part of the cladding layer sandwiched between the core layers of adjacent optical waveguides, optically induced refraction A transparent body with rate change characteristics is formed, and this transparent body is irradiated with excitation light to optically couple adjacent optical waveguides, so if this is applied as an optical directional coupler or optical switch, Since the optical coupler itself can function as an optical directional coupler or optical switch, it is possible to downsize it, and
It can also be formed into an array and can be used as a functional element of an optical IC circuit.

[Brief explanation of the drawing]

Fig. 1 shows a conventional optical directional coupler, Fig. 2 shows an optical switch using the conventional prism coupling method, and Fig. 3 shows an optical directional coupler according to an embodiment of the present invention. A cross-sectional view of
FIG. 4 is a diagram showing the refractive index change characteristics of a transparent body having light-induced refractive index change characteristics used in the embodiment shown in FIG. 3, and FIG. 5 is an optical directional coupler showing an embodiment of the present invention. Figure 6 is a cross-sectional view of the optical directional coupler in Figure 5, Figures 7 and 8 are
9 and 9 respectively show other embodiments of the present invention. It is a diagram showing an optical switch. 10, 20, 30; board, 11, 14, 21, 24
・51, 34, 41, 44 turmeric core layer. 12, 15, 22, 25, 42, 45; cladding layer,
13/26/56/43i A transparent body with light-induced refractive index change characteristics. Patent Applicant Tateishi Electric Co., Ltd. Agent Patent Attorney Shigeru Nakamura Shin No. 1 (A) '11211 11! ! 3 Fig. 4 Fig. 5 Fig. 6 Fig. J4゜l189

Claims (2)

[Claims] (1) A plurality of optical waveguides consisting of a core layer and a cladding layer are arranged in parallel on the substrate surface, and a part of the cladding layer sandwiched between the core layers of adjacent optical waveguides is replaced with a light-induced refractive index change. An optical coupler is characterized in that it forms a transparent body having a characteristic, and optically couples adjacent optical waveguides by irradiating this diluent with excitation light. (2) At least one of the optical waveguides arranged in parallel. 2. The optical coupler according to claim 1, wherein the transparent body is formed by providing a bent portion and including the bent portion.