JP2003114397A - Optical recording device using optical waveguide array - Google Patents

Abstract

(57) Abstract: Provided is an optical recording device using an optical waveguide array with improved coupling efficiency when connecting optical fibers having different mode field diameters to an optical waveguide. A normal line of an incident surface of the waveguide in the optical waveguide array includes a substrate, a waveguide formed on the substrate, and a clat layer formed on the substrate and the waveguide. The angle θ ₂ between the optical fiber and the light traveling axis of the waveguide, and the angle between the normal to the exit surface of the optical fiber in the optical fiber array coupled to the incident surface of the optical waveguide array and the light traveling axis of the optical fiber θ ₁ , the refractive index n _{2 of the} waveguide, and the refractive index n ₁ of the core of the optical fiber satisfy a predetermined relationship, and the normal to the incident surface of the waveguide, the light traveling axis of the waveguide, and the The normal line of the exit surface of the optical fiber and the light traveling axis of the optical fiber are on the same plane, and the obtuse angle formed by the entrance surface of the waveguide and the side surface of the waveguide is the exit surface of the optical fiber. The optical waveguide so that a side surface of the optical fiber overlaps an acute angle side formed by the optical fiber; Ray and was connected to the optical fiber array.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording device such as an electrophotographic device or an optical disc device which performs optical recording by scanning a photosensitive material with a plurality of laser beams using an optical waveguide array.

[0002]

2. Description of the Related Art In a laser printer typified by an optical recording apparatus, when a plurality of laser beams are simultaneously scanned by a rotary polygon mirror to perform optical recording, the number of beams is increased even if the rotation speed of the rotary polygon mirror cannot be increased. It is possible to speed up by a minute. As a method of generating a plurality of laser beams, there is a method of using an optical fiber array. An optical recording device for performing optical recording by scanning a plurality of laser beams on a photosensitive material using an optical fiber array is disclosed in, for example, Japanese Patent Laid-Open No. 9-146023.
It is known from the publication.

[0003]

In order to further increase the speed and resolution of the laser printer, it is necessary to increase the number of scanning laser beams and narrow the pitch. For that purpose, it becomes necessary to use an optical waveguide array as the multi-beam generating element. However, when coupling the optical fiber array to the optical waveguide array, if the mode field diameter of the optical fiber and the mode field diameter of the waveguide are different, the coupling loss when coupling the optical fiber array and the optical waveguide array. Will become bigger.

An object of the present invention is to increase the coupling efficiency when connecting an optical waveguide array and an optical fiber array having different mode field diameters.

[0005]

SUMMARY OF THE INVENTION The present invention is an optical recording device for modulating and scanning a plurality of laser beams emitted from an optical waveguide array to scan on a photosensitive material, which is formed on a substrate and the substrate. An angle θ ₂ formed by the normal line of the incident surface of the waveguide in the optical waveguide array formed of the waveguide and the substrate and the clat layer formed on the waveguide and the light traveling axis of the waveguide. , An angle θ ₁ formed by the normal line of the exit surface of the optical fiber in the optical fiber array coupled to the entrance surface of the optical waveguide array and the optical fiber optical axis, the refractive index n _{2 of the} waveguide, the optical fiber And the refractive index n ₁ of the core satisfy the relationship of the equation (1), and the normal line of the incident surface of the waveguide, the light traveling axis of the waveguide, the normal line of the emission surface of the optical fiber, and the optical fiber. The light traveling axis of By connecting the optical waveguide array and the optical fiber array so that the obtuse angle formed by the incident surface and the side surface of the waveguide overlaps with the acute angle side formed by the emitting surface of the optical fiber and the side surface of the optical fiber. The above objective was achieved.

The mode field diameter D _{w ∥} of the waveguide in the plane direction in which the normal line of the incident surface of the waveguide and the light traveling axis of the waveguide exist is configured to satisfy the condition of the expression (2). To be done. Further, the mode field diameter D _{W ⊥} of the waveguide in the direction perpendicular to the plane in which the normal line of the incident surface of the waveguide and the light traveling axis of the waveguide exist satisfy the relation of the expression (3). Is configured as follows.

[0007]

[Equation 4]

[0008]

[Equation 5]

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The refractive index of the core of an optical fiber is n ₁
= 1.6, the refractive index of the waveguide is n ₂ = 1.45, and the mode field diameter of the waveguide in the plane direction in which the normal line of the exit surface of the waveguide and the optical traveling axis of the waveguide are present is D _{W ∥} = 2.36 (μ
m), the mode field diameter in the direction perpendicular to the plane in which the normal line of the exit surface of the waveguide and the optical propagation axis of the waveguide are present is D
_{When W⊥} = 4 (μm) and the mode field diameter of the optical fiber is D _f = 4 (μm), the angle between the normal line of the incident surface of the waveguide and the light traveling axis is θ, as shown in FIG. ₂ = 0 °,
The angle between the normal line of the exit surface of the optical fiber and the light traveling axis is θ
_{When 1} = 0 ° and the waveguide and the optical fiber are coupled so that the central axes coincide with each other, the coupling efficiency η becomes (4)
It can be calculated from the formula and is 87.5%. However, as shown in FIG. 8, in order to satisfy the equations (1) and (2), the exit end face and the waveguide entrance end face of the optical fiber are polished so that θ ₁ = 60 ° and θ ₂ = 72.87 °. However, the normal line of the incident surface of the waveguide, the optical traveling axis of the waveguide, the normal line of the outgoing surface of the optical fiber and the optical traveling axis of the optical fiber exist on the same plane, and the incident surface of the waveguide and the waveguide When the waveguide and the optical fiber are connected so that the obtuse angle formed by the side surface overlaps the acute angle side formed by the emission surface of the optical fiber and the side surface of the optical fiber, the coupling efficiency becomes 100% and the coupling efficiency becomes 12.5%. Can also be increased.

[0010]

[Equation 6]

Under the above conditions, D _f = D _{W ⊥} = 4 (μ
m), which satisfies the equation (3), but D _f = 4 (μ
m) and D _{W ⊥} = 3 (μm), when the condition (3) is not satisfied, the coupling efficiency is 96%, which is lower than when the formula (3) is satisfied.

An embodiment of an optical recording device using the optical waveguide array of the present invention will be described below. FIG. 1 shows an optical recording device of the present invention. The light emitted from the semiconductor laser 6 is passed through the lens in the LD module 7 to the single mode optical fiber 5
Lead to. A plurality of laser module parts are prepared, and the emission end faces of the respective optical fibers are arrayed and connected to the incident end face of the optical waveguide array 8. A plurality of laser beams emitted from the optical waveguide array are guided onto the polygon mirror 3 by the lens 4. The beam reflected on the polygon mirror 3 passes through the Fθ lens 2 and then is imaged on the photosensitive drum 1 and scanned.

The details of the structure of the LD module section are shown in FIG. The semiconductor laser 6 is welded to the LDM holder 10 by means of laser welding. The light emitted from the semiconductor laser 6 is imaged on the end face 14 of the single mode optical fiber 5 by the lens 11. Single mode optical fiber 5
Removes the covering, and exposes the 125 μm diameter clad portion, inserts it into the ferrule 13, and adheres it. The ferrule 13 is further adhered to the ferrule holder 12. The ferrule holder 12 integrated with the single mode optical fiber 5 and the ferrule 13 is welded to the LDM holder 10 by laser welding.

FIG. 3 shows a detailed structure of the optical fiber array section. The diameter of the end of the clat portion excluding the outer cover of the single mode optical fiber is a good circular shape of about 125 (μm). On the other hand, the diameter of the core portion 17 through which light is guided is about 4 (μm) in the case of a single mode optical fiber, and the core portion 17 is accurately arranged at the center of the clat portion 18. Therefore, as shown in FIG. 3, a plurality of single mode optical fibers excluding the outer cover are sandwiched by the flat glass 15 from above and below, and the pressing plates 16 are pressed from both sides so that the clats 18 are in close contact with each other. After that, the optical fiber array portion is fixed with an adhesive, and the output end face of the optical fiber array is polished at an angle θ ₁ that satisfies the expressions (1) and (2).

The structure of the optical waveguide array portion is shown in FIG. The waveguide 19 is formed of a mixed substance of SiO ₂ and TiO ₂ , and has a refractive index higher by 1 to 8% than the quartz glass substrate 20 and the cladding layer 22 made of pure SiO ₂ . Quartz glass substrate 20, cladding layer 2 on waveguide 19
A SiO ₂ film to be ₂ is deposited. Further, the incident surface 23 of the waveguide is polished at an angle θ ₂ that satisfies the expressions (1) and (2).

The structure of the connecting portion between the exit end face of the optical fiber array and the entrance end face of the optical waveguide array will be described with reference to FIGS. The waveguide entrance surface 23 and the optical fiber exit surface 24 are connected to each other by connecting the waveguide entrance surface normal line 28, the waveguide light advancing axis 29, the optical fiber exit surface normal line 26 and the optical fiber light. The traveling axis 25 is on the same plane, and the obtuse angle 31 formed by the waveguide entrance surface 23 and the waveguide side surface 30 is an acute angle 32 formed by the optical fiber exit surface 24 and the optical fiber side surface 27.
The optical waveguide array 8 and the optical fiber array 9 are brought into close contact with each other so as to overlap with each other, and after aligning so as to maximize the coupling efficiency, they are adhered using a UV resin.

[0017]

As described above, according to the present invention, the coupling efficiency between the optical waveguide array and the optical fiber array having different mode field diameters can be increased.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical system of an optical recording device using an optical waveguide array of the present invention.

FIG. 2 is a diagram showing an LD module section of an optical recording device using the optical waveguide array of the present invention.

FIG. 3 is a diagram showing an optical fiber array section of an optical recording device using the optical waveguide array of the present invention.

FIG. 4 is a diagram showing an optical waveguide array portion of an optical recording device using the optical waveguide array of the present invention.

FIG. 5 is a diagram showing a connecting portion between an optical fiber array section and an optical waveguide array section of the optical recording device of the present invention.

FIG. 6 is a diagram showing a connecting portion between a waveguide and an optical fiber of an optical recording device using the optical waveguide array of the present invention.

FIG. 7 is a diagram showing a state in which an entrance surface of a waveguide and an exit surface of an optical fiber of an optical recording device using the optical waveguide array of the present invention are coupled so that their central axes coincide with each other.

FIG. 8 is a diagram when an incident surface of a waveguide and an emission surface of an optical fiber of an optical recording device using the optical waveguide array of the present invention are coupled.

[Explanation of symbols]

1 ... Photosensitive drum, 2 ... Fθ lens, 3 ... Polygon mirror,
4 ... Lens, 5 ... Optical fiber, 6 ... Semiconductor laser, 7 ...
LD module, 8 ... Optical waveguide array, 9 ... Optical fiber array, 10 ... LDM holder, 11 ... Lens, 12 ... Ferrule holder, 13 ... Ferrule, 15 ... Flat glass, 16 ... Pressing plate, 17 ... Core part, 18 ... Clat portion, 19 ... Waveguide, 20 ... Quartz glass, 21 ... Waveguide exit surface, 22 ... Clut layer, 23 ... Waveguide entrance surface, 2
4 ... Emitting surface of optical fiber, 25 ... Optical traveling axis of optical fiber, 26 ... Normal line of emitting surface of optical fiber, 27 ... Side surface of optical fiber, 28 ... Normal line of incident surface of waveguide, 29 ... Waveguide Optical axis, 30 ... Side surface of waveguide, 31 ... Obtuse angle, 32 ...
acute angle

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Claims (3)

[Claims] 1. An optical recording device for modulating and scanning a plurality of laser beams emitted from an optical waveguide array to scan on a photosensitive material, a substrate, a waveguide formed on the substrate, the substrate and the substrate. The angle θ ₂ formed by the normal line of the incident surface of the waveguide and the light advancing axis of the waveguide in the optical waveguide array, which is composed of a clatt layer formed on the waveguide, and the incident surface of the optical waveguide array. Angle θ ₁ formed by the normal line of the exit surface of the optical fiber in the optical fiber array coupled to the optical fiber and the light traveling axis of the optical fiber, the refractive index n _{2 of the} waveguide, and the refractive index n ₁ of the core of the optical fiber. And satisfy the relationship of the following formula, the normal line of the incident surface of the waveguide, the light traveling axis of the waveguide, the normal line of the exit surface of the optical fiber and the light traveling axis of the optical fiber on the same plane And the side surface of the waveguide is That obtuse angle is, the optical fiber of the emission surface and the optical recording apparatus being characterized in that connected to said optical fiber array and the optical waveguide array to overlap the acute angle side of the side surface make of the optical fiber. [Equation 1] 2. A mode field diameter D _{w ∥ of the} waveguide in a plane direction in which a normal line of the incident surface of the waveguide and an optical traveling axis of the waveguide exist, and a mode field diameter D of the optical fiber.
The optical recording device according to claim 1, wherein the relationship of _f satisfies the following condition. [Equation 2] 3. The mode field diameter D _{W ⊥ of the} waveguide in the direction perpendicular to the plane in which the normal line of the incident surface of the waveguide and the light traveling axis of the waveguide exist are _expressed by the following equation. The optical recording device according to claim 1, wherein the optical recording device is satisfied. [Equation 3]