Optical module and its manufacturing method

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an optical module that operates in a high frequency region used for optical communication and measurement, and more particularly to a structure of an optical module for mass production at low cost using a thin package and a method for manufacturing the same.

【0002】

[Conventional technology]

Figure 3 shows an example of the structure of a conventional high speed photodiode (PD) module. Here, 1 is a planar PD element (PD chip), 2 is a submount, 3 is a high frequency line, 4 is a metal carrier, 5 is a mirror, 6 is a metal package with a high frequency coaxial connector, and 7 is a lens for optical coupling. , 8 is a ferrule with an optical fiber internally fixed, and 9 is a lid for airtight sealing.

【0003】

To assemble this, first mount the PD element 1, submount 2, and high-frequency line 3 on the carrier 4 with a solder material such as gold tin. The mirror 5 is fixed to the upper part of the PD element 1 by an adhesive or YAG laser welding on the carrier 1 via a member for holding the mirror (omitted in this figure) having an appropriate shape. The lens 7 is aligned with the optical fiber of the ferrule 8 arranged at a predetermined position by optical axis alignment and welded and fixed to the carrier 4. After that, the carrier 4 is fixed to the package 6 with solder or the like. Then, the lid 9 is seam welded to the package 6 and hermetically sealed. Finally, the ferrule 8 is aligned and welded to the package 6.

【0004】

If an electric preamplifier (preamplifier) is mounted instead of the high-frequency line 3 in the above process, a module with a built-in preamplifier can also be used.

【0005】

[Problems to be Solved by the Invention]

In the conventional structure of FIG. 3 described above, in order to insert the mirror 5 between the optical element 1 and the lens 7, the working distance (WD) of the lens 7 needs to be a certain length. Therefore, as the optical coupling lens 7, an aspherical lens having a low image magnification and a large aperture is mainly used.

【0006】

However, since the light receiving diameter is generally small in the high-speed PD element 1, the image magnification must be increased, and in order to secure WD there, the lens diameter of the lens 7 must be increased.

【0007】

On the other hand, it is required to reduce the height of the module as much as possible in order to improve the mounting density, but there is a point that the thickness of the module cannot be reduced if the lens diameter is large.

【0008】

Further, in this conventional structure, the manufacturing process is complicated and the number of parts is large, which is disadvantageous for mass production.

【0009】

The present invention has been made in view of the above points, and an object of the present invention is a surface optical element module for high-speed operation, which is low cost, thin, and excellent in productivity and mountability. It is an object of the present invention to provide a suitable optical module and a method for manufacturing the same.

【0010】

[Means for solving problems]

In order to achieve the above object, the invention of the optical module according to claim 1 is an optical module that optically couples a planar optical element that inputs and outputs an optical signal in a direction perpendicular to an element substrate and an optical fiber. The planar optical element and the optical fiber are arranged in a direction parallel to the bottom surface of the module package, and an optical lens for optically coupling the optical fiber and the planar optical element to each other is integrated with the optical lens. It is characterized by having a mirror surface that bends an optical path passing through the optical lens in a direction perpendicular to the planar optical element.

【0011】

Here, the optical lens is used for packaging the package via the mirror surface formed on the back side of the optical lens or the mirror surface formed on the slope of the protrusion on the back side of the lid for sealing the package. It can be characterized in that it is integrally fixed to the slope of the protrusion of the lid.

【0012】

Further, the optical lens can be characterized by being a hemispherical lens.

【0013】

Further, the optical lens can be characterized by being a refractive index distribution type lens in which a high refractive index layer is distributed in a hemisphere.

【0014】

Further, the optical lens can be characterized by being an aspherical lens with a mirror in which the mirror surface is formed inside and the light entering / exiting directions are at right angles.

【0015】

Further, instead of the lid for sealing the package, a lens fixing plate arranged and fixed inside the module package may be used.

【0016】

In order to achieve the above object, the invention of the method for manufacturing an optical module according to claim 7 is a step of fixing an optical fiber in a direction parallel to the bottom surface of a module package and inputting / outputting an optical signal in a direction perpendicular to an element substrate. A step of mounting a planar optical element on the element substrate at a predetermined position of the module package in a direction parallel to the bottom surface of the module package, and optics for optically coupling the optical fiber and the planar optical element with each other. It is characterized by having a step of finely adjusting and fixing a lens and a mirror surface that bends an optical path passing through the optical lens in a direction perpendicular to the planar optical element in a direction parallel to the bottom surface of the module package. And.

【0017】

Here, the optical lens is attached to the package sealing lid via the mirror surface formed on the back side of the optical lens or the mirror surface formed on the inclined surface of the protrusion on the back side of the package sealing lid. The step of integrally fixing to the slope of the protrusion and the optical axis alignment of the planar optical element and the optical fiber by finely adjusting the lid for sealing the package in a direction parallel to the bottom surface of the module package. It is possible to have a step of fixing the lid for sealing the package to the module package.

【0018】

(Action) With the above configuration, in the present invention, a thin high-speed PD module and a surface light emitting element module can be easily realized at low cost.

【0019】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

【0020】

(First Embodiment) FIG. 1 schematically shows the configuration of a hemispherical lens PD module according to the first embodiment of the present invention. Here, 1-1 is a planar PD element as a planar optical element that inputs and outputs optical signals in the direction perpendicular to the element substrate, 2-1 is a submount as an element substrate, and 5-1 is an optical path. Mirror surface that bends in the direction perpendicular to the PD element 1-1, 6-1 is a ceramic package with high-frequency wiring as a module package, and 7-1 is an optical fiber and surface PD element 1-1 that are optically coupled to each other. 8-1 is a ferrule with its optical fiber fixed inside, 9-1 is a metal lid for airtight sealing, and 10-1 is a preamplifier IC (integrated circuit).

【0021】

The following steps are used to assemble the optical module shown in Fig. 1. First, ferrule 8-1 is fixed to package 6-1 with low melting point glass or brazing material. Next, the PD element 1-1 is fixed on the package 6-1 with AuSn solder. Next, the hemispherical lens 1 is fixed to the protrusion (triangular block) of the lid with solder or an adhesive. Furthermore, the lid 9-1 with a lens is aligned at the position where the current output of PD1-1 is maximized by entering light from an optical fiber with an external light source, and the lid 9-1 is put into package 6-1 with a YAG laser. Fix it. Finally, the lid 9-1 and the package 6-1 are hermetically sealed with resin.

【0022】

Here, the hemispherical lens 7-1 with a non-reflective coating all around is cut in half and used to suppress reflection on a spherical surface.

【0023】

The optical axis of the optical fiber of PD element 1-1 and ferrule 8-1 is aligned by sliding the lens fixed to the lid 9-1 in the horizontal direction with respect to the bottom surface of package 6-1. Therefore, since the optical fiber can be fixed to the package 6-1 in advance, it can be made thinner and the number of parts is small, which is suitable for cost reduction by mass production. Since the optical axis adjustment is only in the horizontal XY direction, the process is simple and automation is easy.

【0024】

A spherical lens is cheaper and easier to obtain than an aspherical lens, but in principle, a long WD cannot be obtained, so it is impossible to insert a mirror between the spherical lens and the planar optical element. On the other hand, in the present invention, this is solved by forming a mirror surface in the lens. The mirror surface 5-1 can be easily realized by fixing the lens 5-1 to the gold-plated lid 9-1 with optical adhesive, but in order to obtain complete total reflection, the dielectric film is placed on the lens 7-1 side. It can also be formed by vapor deposition.

【0025】

In this embodiment, the airtight seal is made of resin, but a lens fixing plate (not shown) is housed inside the package, and an airtight lid 9-1 is placed on the upper part of the package to resist the lid. It is also possible to make a structure that tightly seals by welding or the like.

【0026】

In addition, the ferrule portion 8-1 can be configured as a small optical connector in a modular configuration in which the optical fiber is not directly emitted.

【0027】

Further, an array module can be manufactured by using a bar-shaped (rod-shaped) PD array element in which a plurality of PD elements are formed in the lateral direction and an array fiber. In this case, the lens includes a rod lens (which is also cut in half and contains a mirror surface), an aspherical lens array, and a refractive index distribution lens in which a high refractive index layer is distributed hemispherically according to the element pitch. It will be adopted. In array modules, the requirements for mounting angle accuracy of PD elements and optical fibers become stricter, but basic assembly is possible in exactly the same process.

【0028】

(Second Embodiment) FIG. 2 schematically shows the configuration of the aspherical lens VCSEL module in the second embodiment of the present invention. Here, 1-2 is a surface emitting laser diode element (VCSEL element), 2-2 is a submount, 5-2 is a mirror surface, 6-2 is a ceramic package with high frequency wiring, and 7-2 is an aspherical lens. , 8-2 is a ferrule with an optical fiber fixed inside, 9-2 is a metal lid, and 10-2 is a laser driver IC. The aspherical lens 7-2 is an optical lens with a mirror that has a pair of aspherical lenses and forms a mirror surface 5-2 on the inside so that the light entering and exiting directions are at right angles.

【0029】

This embodiment is an example in which the surface emitting laser diode (VCSEL) element 1-2 is modularized. An aspherical lens 7-2 is used in order to obtain a high optical coupling, but the assembly procedure is basically the first of the present invention described above, except that the surface emitting laser diode element 1-2 is made to emit light for adjustment. It is the same as the embodiment of 1.

【0030】

The aspherical lens 7-2 has a special shape with the lens surface 5-2 in the direction perpendicular to it, but once the mold is raised, the manufacturing method is the same as the normal one, so the module is mass-produced. If this happens, cost reduction can be expected. The aspherical lens 7-2 in FIG. 2 is like a dice cut diagonally, and an optimally designed lens is formed on the two surfaces. Depending on the optical design, one side may be flat.

【0031】

Of course, as long as the requirements for optical coupling efficiency are not strict, a hemispherical lens may be used as in the first embodiment of the present invention described above.

【0032】

[Effect of the invention]

As described above, according to the present invention, since the optical path conversion element and the lens are integrated, the module can be simplified, and the high-speed photodiode module and the surface emitting laser diode module can be significantly reduced in cost and made smaller and thinner. Forming can be realized.

[Simple explanation of drawings]

[Figure 1]

It is sectional drawing which shows typically the structure of the photodiode module of 1st Embodiment of this invention.

[Figure 2]

It is sectional drawing which shows typically the structure of the surface emitting laser diode module of 2nd Embodiment of this invention.

[Fig. 3]

It is sectional drawing which shows typically the structural example of the conventional photodiode module.

[Explanation of symbols]

1, 1-1 PD element 1-2 VCSEL element 2,2-1, 2-2 submount 3 High frequency line 4 carrier 5 mirror 5-1 and 5-2 Mirror surface 6 packages 6-1, 6-2 Ceramic package with high frequency electrode 7 Aspherical lens 7-1 Hemispherical lens 7-2 Aspherical lens with mirror 8, 8-1, 8-2 ferrules 9, 9-1, 9-2 lid 10-1 preamplifier circuit 10-2 Laser driver IC