KR19990012392A - Integrated optical switch - Google Patents

Abstract

The present invention relates to an integrated optical optical switch, the integrated optical optical switch comprises: an input waveguide formed on a substrate of a predetermined material; A refractive region connected to the input waveguide and formed to have a predetermined angle of incidence satisfying Snell's law with respect to the direction in which light is guided; An electrode formed on the refractive region; And at least two output waveguides that are switched by a change in the refractive index of the refractive region according to the voltage of the electrode to guide the incident light to the input waveguide.

According to the present invention, since the structure is simple compared to the conventional optical switch, device fabrication and alignment are easy. In addition, Snell's law can be used to design easily by knowing only the change in refractive index according to the applied electric field. Also, the manufacturing process is easy and the tolerance of the process is high.

Description

Integrated optical switch

The present invention relates to an optical switch, and more particularly, to an integrated optical optical switch using Snell's law.

In general, integrated optics refers to a technology for fabricating various optical devices based on an optical waveguide in one substrate. Integrated optics can reduce the manufacturing cost because the alignment between the optical elements is very easy and many functional devices can be manufactured in a narrow area. In addition, an electrode is manufactured near the optical waveguide to concentrate the electric field only in the optical waveguide region, thereby controlling the flow of the optical wave with a low driving voltage. As an integrated optical substrate material, silica, ferroelectrics, semiconductors, polymers, and the like are used.

Among the integrated optical substrate materials, a substrate having an electrooptic effect of changing an index by applying an electric field or a thermooptic effect of changing a refractive index by changing a temperature is used for fabricating an optical switch. Since the optical switch is a device for switching the route of the optical signal, a material without such an electro-optic or thermo-optic effect is not used. Representative ferroelectric materials include lithium naobate (LiNbO ₃ ). Silica is used as a thermo-optic material. There are two types of polymers, electro-optic polymers and thermo-optic polymers, or polymers containing both effects.

FIG. 1A is a plan view of a waveguide of a conventional 1x2 optical switch. The optical switch waveguide according to FIG. 1 is formed by two input waveguides 104 and 106 with one input waveguide 100 branched at a branch point 102.

FIG. 1B is a view in which electrodes 112 and 114 are formed on two waveguides branched from FIG. 1A. In the optical switch according to FIG. 1B, when an electric field is not applied to the two electrodes 112 and 114, power is applied at the branch point 102. Two optical signals divided in half are output to the output waveguides 104 and 106, respectively. However, when the voltages V ₁ and V ₂ are applied to the electrodes, if the substrate material is a material having a thermo-optic effect, the resulting electric field generates heat to the electrodes themselves, causing the electrodes to act as heaters and thus the The refractive index changes. When the refractive index of one waveguide is increased by using the variable refractive index, the light in progress proceeds to the waveguide having a high refractive index. Therefore, if the intensity of the applied electric field is well adjusted and the refractive index of each waveguide is adjusted by the thermooptic effect, the light is output to the waveguide of 104 or 106 to act as an optical switch.

FIG. 1C is an extension of the 1x2 optical switch shown in FIG. 1B to a 1x4 optical switch. The 1x4 optical switch according to FIG. 1C includes the input waveguide 100, the first branch point 102, the first and second electrodes of FIG. 1B. In the 1x2 optical switch consisting of (112, 114), each waveguide branches at the second and third branch points 120 and 122, and each electrode 124, 126, on each branched waveguide 132, 134, 136 and 138. 128 and 130), and the refractive index is controlled by differentially applying an electric field.

However, these optical switches are complicated in structure and many curves, and are difficult to manufacture and process. If the structure is complicated, the yield of the device may be low because the process becomes difficult and the tolerance of the process for maintaining the uniformity of the waveguide shape is small. As the number of output channels increases, the number of electrodes increases, so there is a need to pay attention to various areas during alignment. In addition, the conventional optical switch has to reduce the branching angle at the branching point, in order to reduce the branching angle, there is a problem that the length of the device must be long.

The technical problem to be achieved by the present invention is to simplify the design and to remove the curves on the waveguide to reduce the loss and manufacturing difficulties to the simple structure of the applied electric field and to select the waveguide using the well-known Snell's law An optical optical switch is provided.

Figure 1a is a plan view of the waveguide shape of a conventional 1x2 optical switch.

FIG. 1B is a plan view of the 1 × 2 optical switch of FIG. 1A. FIG.

Figure 1c is a plan view of a conventional 1x4 optical switch.

Figure 2a is a plan view of the waveguide shape of the 1x2 optical switch according to the present invention.

FIG. 2B is a plan view of the 1 × 2 optical switch of FIG. 2A. FIG.

FIG. 2C is a plan view of the 1 × 4 optical switch in which FIG. 2B is expanded.

3 shows the refraction of light according to Snell's law.

In order to achieve the above technical problem, the integrated optical optical switch according to the present invention comprises an input waveguide formed on a substrate of a predetermined material; A refractive region connected to the input waveguide and formed to have a predetermined angle of incidence that satisfies Snell's law with respect to the direction in which light is guided; An electrode formed on the refractive region; And at least two output waveguides switched by a change in refractive index of the refractive region according to the voltage of the electrode to guide the incident light to the input waveguide.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. Figure 2a is a plan view of the waveguide shape of the 1x2 optical switch according to the present invention, the waveguide of the optical switch according to Figure 2a, the input waveguide 200, the refractive region 202, the first and second output waveguides (204, 206) ) The substrate may be any substrate having an electro-optic effect or a thermo-optic effect. FIG. 2B is a view in which the electrode 212 is formed in the refractive region of FIG. 2A. In the 1 × 2 optical switch according to FIG. 2B, the light incident through the input waveguide 200 is not refracted in the refractive region 202 unless the voltage V is applied. Instead, it is guided to the first output waveguide 204 in line with the input waveguide 200. When the voltage V is applied, the refractive index of the refractive region 202 is increased, and the light incident through the input waveguide 200 is refracted by the refractive region 202 to the second output waveguide 206 below the first output waveguide. It is waved.

FIG. 2C illustrates the 1 × 4 optical switch extending from FIG. 2B. The optical switch according to FIG. 2C operates similarly to the optical switch shown in FIG. 2B, but the refractive index of the refractive region 202 is changed according to the intensity of the applied electric field. The light is then guided to one of the first to fourth output waveguides 204, 206, 222, and 224.

In the case of a material having an electro-optic effect, its refractive index varies as follows depending on the intensity of the applied electric field.

here, n _i Is the refractive index change, n is the refractive index, r _ij is the electro-optic coefficient and E _j is the intensity of the applied electric field. n and r _ij are material dependent.

In the case of a material having a thermo-optic effect, heat is generated in the electrode itself according to the intensity of the applied electric field so that the electrode acts as a heater to induce a temperature change, and the refractive index varies according to the induced temperature change as follows.

here, n _i The refractive index change, Silver thermo-optic coefficient, T (x, y) Is the induced temperature distribution and I _{norm, j} (x, y) is the light intensity distribution in the waveguide mode.

The refractive regions 202 of FIGS. 2A to 2C are manufactured to give incident light according to Snell's law to incident light. Figure 3 shows the direction of light travel according to Snell's law. Snell's law states that when light travels from material 1 with effective refractive index n ₁ to material 2 with effective refractive index n ₂ , as shown in FIG. 3, the light is refracted at the interface between material 1 and material 2. Determined by the equation.

n ₁ sin ₁ = n ₂ sin ₂

Where θ ₁ is the angle of incidence of light in material 1 and θ ₂ is the angle of refraction of light in material 2. According to Equation 3, when n ₂ is larger than n ₁ , light is refracted because θ ₂ has a value smaller than θ ₁ . In addition, when n ₁ and θ ₁ are fixed and n ₂ is increased, θ ₂ becomes smaller, so that light is more refracted.

The width of the refractive region 202 should be designed in consideration of the spreading phenomenon when light travels from the input waveguide 200 to the refractive region 202.

According to the present invention, since the number of electrodes and the overall structure is simple as compared with the conventional optical switch, device fabrication and alignment are easy. In addition, Snell's law can be used to design easily by knowing only the change in refractive index according to the applied electric field. Also, the manufacturing process is easy and the tolerance of the process is high.

Claims (3)

An input waveguide formed on a substrate made of a predetermined material; A refractive region connected to the input waveguide and formed to have a predetermined angle of incidence that satisfies Snell's law with respect to the direction in which light is guided; An electrode formed on the refractive region; And And at least two output waveguides which are switched by a change in the refractive index of the refractive region according to the voltage of the electrode to guide the incident light to the input waveguide. The method of claim 1, wherein the material of the substrate An integrated optical optical switch characterized in that the material having an electro-optic effect of changing the refractive index according to the intensity of the applied electric field. The method of claim 1, wherein the material of the substrate An integrated optical optical switch characterized in that the thermo-optic material is a temperature change is induced according to the intensity of the applied electric field, the refractive index is changed in accordance with the induced temperature change.