JPH0743552A - Optical waveguide element for coupling semiconductor laser diode and waveguide type module using the same - Google Patents

Abstract

PURPOSE:To provide the novel single mode optical waveguide element for coupling a semiconductor laser diode which is greatly improved in coupling efficiency with the semiconductor laser diode by having a tapered part gradually increased in the width and thickness of a clad with distance from the end face in continuation with an exposed core. CONSTITUTION:This optical waveguide element 1 for coupling the semiconductor laser diode is composed of the core 3 having a large refractive index and the clad 4 having the refractive index smaller than this refractive index and has nearly the same spot size as the spot size of an optical fiber. This optical waveguide element 1 for coupling the semiconductor laser diode has a structure formed by etching away a part of the clad glass 4 near the end face 6 of the waveguide in a required amt. to expose the core 3 by the required length. Further, the clad glass 4 continuous with the exposed core 3 is tapered in its transverse direction and thickness direction to form the tapered part 5 of the optical waveguide element for coupling the semiconductor laser diode, by which an electric field distribution is gradually converted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide device, particularly a single mode optical waveguide device for coupling a semiconductor laser diode and a waveguide type module using the same.

[0002]

2. Description of the Related Art In optical fiber communication, the optical fiber to be used is large-scaled because it has many advantages such as large capacity, low loss, no crosstalk, no induction, and light weight as a transmission medium for various signals, and has a large economic effect. It has been introduced, but further use and development is expected.

In order to introduce and propagate laser light from a laser light source into the optical fiber, it is necessary to efficiently couple the laser light source and the optical fiber.

FIG. 3 is a view for explaining respective electric field distributions in coupling the semiconductor laser diode 22 which is a laser light source and the optical waveguide device 20. Reference numeral 23 is a core of the optical waveguide device 20.

[0005] As shown in FIG. 3, the electric field distribution of the semiconductor laser diode 22 generally has a Gaussian type, (radius a 1 / e- ² peak power) the spot size is about 1 [mu] m.

On the other hand, the ordinary optical waveguide device 20 used for optical fiber communication is designed and manufactured so that the spot size is about 10 μm in consideration of the compatibility with the optical fiber.

Therefore, as shown in FIG. 3, the semiconductor laser diode 2 is used without using means for converting the spot size.
When 2 is directly coupled to the optical waveguide element 20, the laser light from the semiconductor laser diode 22 is radiated to the portion other than the core 23 which is the optical waveguide due to the mismatch of the electric field distribution, and the coupling loss is about 10 dB. And a big value.

FIG. 4 shows a conventional spot size conversion optical waveguide for eliminating the above coupling loss. Figure 4
4A is an external view, and FIG. 4B is a diagram for explaining an electric field distribution.

In FIG. 4, 22 is a semiconductor laser diode, 20 is an optical waveguide element, 23 is a core of the optical waveguide element 20, and 26 is a core having a high refractive index.

The spot size conversion optical waveguide shown in FIG. 4 is formed by forming a core 26 having a high refractive index in the core 23 of the ordinary optical waveguide device 20.

The width of one end of the high-refractive index core 26 is tapered and narrowed so that the electric field distribution gradually changes and can approach the electric field distribution propagating through the core 23.

As described above, with the structure having the spot size converting optical waveguide, the coupling between the semiconductor laser diode 22 and the optical waveguide element 20 can be made a loss of about 3 dB.

In the above-mentioned conventional example, Si ₃ N ₄ is used as the material of the high refractive index core 26 for spot size conversion, and silica glass to which P ₂ O ₅ is further added is used as the material of the core 23. ing.

[0014]

However, the conventional spot size converting optical waveguide has the following drawbacks.

(1) The spot size conversion is one-dimensional, and the spot size is not converted two-dimensionally. That is, the tapered shape of the high-refractive-index core 26 is only in the width direction of the core, and is not tapered in the thickness direction of the core, so that it cannot be perfectly matched with the electric field distribution propagating through the core 23. . Therefore, it has a coupling loss of about 3 dB.

(2) In the process of manufacturing the waveguide for spot size conversion, it is necessary to form the tapered core 26 having a high refractive index and then form the core 23, which complicates the manufacturing process.

(3) High refractive index core 26 material Si ₃ N
_{No. 4} has a large refractive index (n ₁ = 2.1), but has a large Fresnel reflection loss with air (refractive index n ₂ = 1.0) (Fresnel reflection loss is proportional to the square of the difference between the two refractive indices). Fresnel reflection loss = (n ₁ −n ₂ ) ² / (n ₁ + n ₂ ).
² ).

An object of the present invention is to provide a novel single mode optical waveguide device for semiconductor laser diode coupling, which can solve the above-mentioned drawbacks of the prior art and can greatly improve the coupling efficiency with the semiconductor laser diode. Especially.

[0019]

In order to achieve the above object, the present invention comprises a semiconductor laser diode having a core having a large refractive index and a clad having a smaller refractive index, and having a spot size almost the same as that of an optical fiber. In the coupling optical waveguide device, a required amount of cladding close to the end face of the semiconductor laser diode coupling optical waveguide device is removed to expose a core of a required length, and the cladding of the cladding is continuously removed from the end face to the exposed core. The width and thickness are gradually increased to have a tapered portion.

[0020]

The required amount of cladding close to the end face of the semiconductor laser diode coupling optical waveguide element is removed to expose the core of the required length, and the width and thickness of the cladding are reduced continuously with the exposed core away from the end face. By gradually increasing and having a tapered portion, the electric field distribution is gradually converted with good coupling efficiency.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an external view of a semiconductor laser diode coupling optical waveguide device according to the present invention, and FIG. 2 shows an electric field distribution explanatory diagram seen from above and a side electric field distribution explanatory diagram seen from above.

In FIG. 1, 1 is an optical waveguide element for coupling a semiconductor laser diode, 3 is a core made of silica glass, 4 is a cladding made of silica glass, 5 is a tapered portion of the cladding continuous with the core 3, and 6 is a cladding portion. It is an end face.

As shown in FIG. 1, a semiconductor laser diode coupling optical waveguide device 1 according to the present invention has a waveguide end face 6
A part of the nearby clad glass 4 is removed by a required amount of etching to expose the core 3 by a required length. Furthermore, the clad glass 4 continuous with the exposed core 3 is tapered in the width direction and the thickness direction to form the tapered portion 5, so that the electric field distribution is gradually converted.

As shown in FIG. 2, the exposed core 3 of the semiconductor laser diode coupling optical waveguide device 1 according to the present invention.
By continuously providing the tapered portion 5 in the x-axis direction as shown in FIG. 2A and in the y-axis direction as shown in FIG. 2B, the electric field distribution of the laser light is gradually converted. There is.

The spot size R ₀ of the light propagating in the core 3 is given by the following equation.

[0026] _{R 0 1 / (2 × 1nV} ) 1/2 ······· (1) where, V is a normalized frequency, is given by the following equation.

[0027] V = 2π · n · a ( 2Δ) 1/2 ······ (2) where, n is the refractive index of the core, a is the core width, delta is the relative refractive index difference between the core and the cladding Represent

In the portion where the clad 4 is removed, the air becomes the clad, so that the value of V becomes large according to the equation (2).

Therefore, according to the equation (1), the spot size can be reduced and the matching of the electric field distribution with the semiconductor laser diode can be improved.

Further, by making a part of the clad 4 tapered and having a structure having the tapered portion 5, the electric field distribution of the laser light is gradually widened, and the laser light from the semiconductor laser diode is low in loss. Can convert spot size.

In the present invention, even in the thickness direction (y-axis direction) of the cladding 4, the thickness is tapered so that it has a two-dimensional spot size conversion function.
The optimization enables a coupling loss close to 0 dB.

The manufacturing method can be easily processed by a conventional dry etching technique (reactive etching method, ion milling, etc.).

[0033]

The optical waveguide device for semiconductor laser diode coupling according to the present invention is easy to manufacture because of its simple structure, and is continuous with the core in the waveguide width direction (x-axis direction).
Since the taper shape is formed in both the depth direction (y-axis direction), the coupling efficiency with the semiconductor laser diode can be significantly improved and the economic effect is large.

[Brief description of drawings]

FIG. 1 is an external view showing a semiconductor laser diode coupling optical waveguide device according to the present invention.

FIG. 2 is a diagram for explaining an electric field distribution of a semiconductor laser diode coupling optical waveguide device according to the present invention.

FIG. 3 is an explanatory diagram of an electric field distribution of a semiconductor laser device and an optical waveguide device.

FIG. 4 is an external view showing a conventional spot size conversion optical waveguide and a view for explaining an electric field distribution.

[Explanation of symbols]

1 semiconductor laser diode coupling optical waveguide element 3 core 4 clad 5 semiconductor laser diode coupling optical waveguide element taper portion 6 semiconductor laser diode coupling optical waveguide element end face

Claims (2)

[Claims] 1. A semiconductor laser diode coupling optical waveguide element comprising a core having a large refractive index and a clad having a refractive index smaller than that, and having a spot size substantially the same as that of an optical fiber. A required amount of clad near the end face of the device is removed to expose a core of a required length, and the width and thickness of the cladding are gradually increased to have a tapered portion as the exposed core continues away from the end face. An optical waveguide device for coupling a semiconductor laser diode characterized by the above. 2. A waveguide type module characterized in that the semiconductor laser diode coupling optical waveguide element according to claim 1 and the semiconductor laser diode are optically coupled.