JP2002062458A - Optical module, its assembling method, and image display device using optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an optical module that optically couples a semiconductor laser having a thin and wide emitting end with an optical waveguide with a low loss. SOLUTION: In mounting a semiconductor laser 12 and an optical waveguide 13 on an optical module base plate 11, recessed parts 14a, 14b and projected parts 16a, 16b are respectively formed on the base plate 11 along the optical axis direction, with variation given in the height direction along the optical axis to the recessed and the projected parts 14a, 14b, 16a, 16b, and with alignment performed in the width direction of the optical waveguide 13 while these parts are fitted to each other; besides, since positional transfer is made possible for the optical waveguide 13 in the thickness direction after it is mounted on the optical module base plate 11, high precision alignment can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser, an optical waveguide, and an optical waveguide for performing high-precision alignment required for optically coupling an edge-emitting semiconductor laser and an optical waveguide with low loss. The present invention relates to an optical module on which an optical element such as a fiber is mounted, a mounting method thereof, and a video display device using the optical module.

[0002]

2. Description of the Related Art When an optical element is mounted on an optical module, it is required that loss of optical coupling between the optical elements is small. As an implementation example, there is a method called active alignment. In this method, for example, when mounting a semiconductor laser and an optical waveguide, the semiconductor laser emits light, light is coupled from the semiconductor laser to the optical waveguide, and the optimum position of the optical waveguide is determined while observing the power at the emission end of the optical waveguide. Find and fix.

In this case, it is necessary to move the optical waveguide in a three-dimensional direction to drive the optical waveguide to an optimum position, and the trouble of this step causes a high cost of the optical module. Therefore, it is desirable that the mounting be automated (passive alignment).

[0004] Automation methods include a visual method using image processing, a mechanical method using fitting of members, and a flip-chip method using the self-alignment effect of molten solder bumps (for example, "Electronics" July 1999, pp42-). 44 ohm). With this method, a mounting accuracy of about 1 μm can be obtained.

[0005] However, depending on the configuration of the optical element, there is a case where a more precise alignment is required. In general, the emission end of an edge-emitting semiconductor laser has a thickness of about 1 μm, and when this semiconductor laser and an optical waveguide are optically coupled, an accuracy of sub-μm is required in the thickness direction. In general, even if the output power of a semiconductor laser is high, the width of the semiconductor laser remains wide at about 1 μm, so that the accuracy of sub-μm is still required in the thickness direction. Thus, the passive alignment method cannot couple the semiconductor laser and the optical waveguide with low loss.

[0006]

The edge emitting semiconductor laser described above has a thickness of about 1 μm at the emitting end, and when the semiconductor laser and the optical waveguide are optically coupled, an accuracy of sub-μm is required in the thickness direction. However, the conventional method cannot couple the semiconductor laser and the optical waveguide with low loss.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical module for optically coupling a semiconductor laser having a narrow and wide emission end with a wide optical waveguide with low loss, a method of mounting the same, and a video display device using the optical module. It is in.

[0008]

According to the present invention, there is provided an optical module having a semiconductor laser and an optical waveguide mounted on a substrate, wherein a concave portion or a convex portion is provided on an opposing surface of the optical waveguide and the substrate. By forming any of the portions, by fitting these uneven portions, the optical waveguide and the substrate are held in a fixed positional relationship, at least one of the depth of the concave portion and the height of the convex portion The optical coupling between the semiconductor laser and the optical waveguide can be adjusted.

A step of mounting the semiconductor laser; a step of aligning the optical waveguide in a width direction of the emitting end of the semiconductor laser; and a step of mounting the optical waveguide on the substrate. A step of causing the semiconductor laser to emit light in the state of the optical waveguide, and aligning the optical waveguide in the thickness direction of the emission end of the semiconductor laser while measuring an optical output coupled to the optical waveguide from the semiconductor laser; It is characterized by consisting of.

Further, in an image display device for displaying the light emitted from the semiconductor laser by spatially modulating the light using a spatial modulation element, the optical module mounting the semiconductor laser and the optical waveguide on a substrate comprises the optical waveguide. And, on the facing surface of the substrate, either a concave portion or a convex portion is formed, and by fitting these concave and convex portions, the optical waveguide and the substrate are held in a fixed positional relationship, and the depth of the concave portion and the It is characterized in that at least one of the heights of the projections is changed to enable adjustment of optical coupling between the semiconductor laser and the optical waveguide.

According to the above-mentioned means, when the thickness of the emitting end of the semiconductor laser is small and wide, passive alignment can be performed with a precision of μm in the width direction, and active alignment can be performed with a precision of sub-μm in the thickness direction. Becomes Thereby, a good optical module can be obtained, and a simple and reliable assembling method can be realized when assembling the optical module. Further, when used in an image display device using this optical module, the volume of the light source unit can be reduced, and the layout of the components of the optical system can be given a degree of freedom.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an exploded perspective view of an optical module for describing a first embodiment of the present invention, and FIG. 2 is a side view thereof.

1 and 2, 11 is an optical module substrate, 12 is a semiconductor laser, 13 is an optical waveguide, and 14a,
14b is a concave portion, 15 is a V groove, and 16a and 16b are convex portions. Step portions 11a and 11b are formed on both sides of the optical module substrate 11 in the longitudinal direction. The semiconductor laser 12 is attached to the step 11a. Concave portions 14a and 14b parallel to the longitudinal direction are formed in the central upper surface 11c of the optical module substrate 11. The V-groove 15 is formed in the step 11b. V
The groove 15 is formed so as to reach the side surface 11 d of the optical module substrate 11.

The optical waveguide 13 comprises a core 13a and a clad 13b formed around the core. Core part 13
In the figure, a is a tapered shape in which the width of the incident end 13a1 is wide in the horizontal direction and narrow in the vertical direction. It is.

On the lower surface of the waveguide 13, concave portions 14a, 14
The projections 16a and 16b are formed substantially parallel to each other along the light emission direction of the waveguide 13 that can be fitted to the projection b. Convex part 16a, 1
6b are inclined portions 16a1, 16a2 whose height gradually increases from both ends in the longitudinal direction toward the center.
16b1 and 16b2 are formed. Reference numeral 17 denotes an optical fiber whose one end is attached to the V groove 15.

FIG. 3 shows how laser light is generated from the semiconductor laser 12. Emission end 121 of semiconductor laser 12
The light having a small thickness and a wide width becomes light that is longer in the thickness direction and narrower in the width direction as the distance from the emission end 121 increases. The light emitted from the semiconductor laser 12 is transmitted to a tapered optical waveguide 13.
It is necessary to match the entrance of the optical waveguide 13 with the exit position of the semiconductor laser 12 in order to couple the light. For example, when the thickness of the emission end 121 is 1 μm, the thickness direction (the y direction in the drawing)
In the case of a width of 100 μm, a positioning accuracy of several μm in the width direction (x direction) is required. Also, since light spreads in the thickness direction as it propagates,
The required positional accuracy in the rotation direction is θx compared to θy
Will be lower.

The method of mounting the optical module will be described again with reference to FIG. First, the concave portions 14a and 14b formed in the central upper surface portion 11c of the optical module substrate 11 can be formed with a precision of about 1 μm by using fine processing such as etching. When forming the concave portions 14a and 14b, the optical waveguide 1 is used when the V-groove 15 is formed so that the semiconductor laser 12 and the end face of the optical waveguide 13 do not come into contact with each other.
The end position of the V-groove 15 may be set so that the optical fiber 17 does not contact the optical fiber 3. Further, the optical module substrate 11
A plurality of grooves other than those used for alignment may be formed in order to absorb deformation due to thermal expansion (not shown).

Next, the semiconductor laser 12 is mounted on the optical module substrate 11 and electric wiring is performed. In mounting the semiconductor laser 12, for example, a marker may be formed on the optical module substrate 11 and the semiconductor laser 12, and alignment may be performed by image matching, or alignment may be performed by a flip chip method using solder bumps. 1 μm
What is necessary is just to implement with the precision of about.

Next, the optical fiber 17 is fitted into the V groove 15 and mounted. Further, the optical waveguide 13 is connected to the optical module substrate 11.
Implement on top. The optical waveguide 13 has protrusions 16a and 16b for fitting into the recesses 14a and 14b. Here, the protrusion 16 has a shape in which the height of the protrusion changes along the optical axis direction. By positioning the optical waveguide 13 by fitting the convex portion 16 to the concave portion 14, the alignment of the optical waveguide 13 in the width direction of the semiconductor laser 12 can be performed with an accuracy of several μm.

Next, positioning of the optical waveguide 13 in the thickness direction is performed. For example, a gonio stage 41 as shown in FIG.
By changing θx, the optical waveguide 13 is moved in the thickness direction. In this state, the semiconductor laser 12 emits light, propagates through the optical waveguide 13, and measures the optical output coupled to the optical fiber 17 with the power meter 42. After moving the optical waveguide 13 to the position where the optical power becomes maximum, it is fixed with an adhesive or the like.

Here, when the optical waveguide 13 is moved in the thickness direction, θx also changes. However, when the thickness of the emission end 121 of the semiconductor laser 12 is small, the influence of the displacement in the θx direction on the optical loss is small. It does not matter. In addition, a displacement occurs between the optical waveguide 13 and the optical fiber 17. For example, when the amount of movement in the thickness direction is 1 μm or less and the core radius of the optical fiber 17 is 10 μm or more, the influence on the optical loss is small, and the problem is raised. No.

In this embodiment, the shape of the convex portion of the optical waveguide 13 is gradually changed. However, the shape of the concave portion of the optical module substrate 11 may be gradually changed. Further, a concave portion may be provided in the optical waveguide 13 and a convex portion may be provided in the optical module substrate 11.

FIGS. 5 and 6 are views for explaining a second embodiment of the present invention. FIG. 15 is an exploded perspective view, and FIG. 6 is a side view. The same components as those in FIG. The description is omitted here by attaching the reference numerals. The difference between this embodiment and the first embodiment is that a V-groove 51 for mounting the optical fiber 17 is formed on the optical waveguide 13.

In this embodiment, when the optical waveguide 13 is moved in the thickness direction as shown in FIG. 6, no displacement occurs between the optical waveguide 13 and the optical fiber 17. Therefore, it is effective when the core diameter of the optical fiber 17 is smaller than the movement amount in the thickness direction.

Next, an application example in which the optical module of the present invention is used as a light source of a projection type video display device will be described with reference to the configuration diagram of FIG.

In FIG. 7, reference numeral 71 denotes an optical module driving unit, 72 denotes an optical module according to the structure of FIG. 1, for example, 73 denotes an optical fiber, 74 denotes a lens, 75 denotes a video input terminal, and 76 denotes a liquid crystal driving unit. , 77 is a liquid crystal panel, 78
Is a projection lens, and 79 is a screen.

The operation of the video display device will be described. The light emitted from the optical module 72 is coupled to the optical fiber 73 with low coupling loss, and propagates through the optical fiber 73 to the vicinity of the lens 74. The light emitted from the end face of the optical fiber 73 near the lens 74 becomes parallel light at the lens 74 and enters the liquid crystal panel 77. On the other hand, a video signal is input from a video signal input terminal 75, and a liquid crystal driving section 76 drives a liquid crystal panel 77 according to the video signal.

Thus, the light incident on the liquid crystal panel 77 is spatially modulated in accordance with the video signal. The spatially modulated light forms an image on a screen 79 via a projection lens 78.

When the light source section is composed of the optical module 72 as compared with the case where a halogen lamp or a xenon lamp is used as the light source of the projection type image display device, the volume of the light source section becomes smaller or the optical fiber There is an advantage that the degree of freedom of layout is increased because light is propagated to the lens 73 by the 73.

[0030]

As described above, according to the present invention, when a semiconductor laser and an optical waveguide are mounted on a substrate, the substrate and the optical waveguide are changed in a direction along the optical axis direction. The position can be moved in the thickness direction after the optical waveguide is mounted, and high-precision positioning can be performed.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view for explaining a first embodiment of the present invention.

FIG. 2 is a side view of the assembled state of FIG. 1;

FIG. 3 is an explanatory diagram for explaining a light emitting state of the semiconductor laser used in FIG. 1;

FIG. 4 is a side view for explaining a method of aligning the optical waveguide in FIG. 1 in a thickness direction of a semiconductor laser emission end;

FIG. 5 is a perspective view for explaining a second embodiment of the present invention.

6 is a side view for explaining a method of aligning the optical waveguide in FIG. 5 in a thickness direction of a semiconductor laser emission end;

FIG. 7 is a configuration diagram for explaining an example to which the present invention is applied.

[Explanation of symbols]

11: optical module substrate, 12: semiconductor laser, 13 ...
Optical waveguides, 14a, 14b: recess, 15: V-groove, 16
a, 16b: convex portion, 16a1, 16a2, 16b1, 1
6b2: inclined section, 17: optical fiber, 41: goniometer, 42: power meter.

Claims (5)

[Claims] 1. An optical module in which a semiconductor laser and an optical waveguide are mounted on a substrate, wherein either a concave portion or a convex portion is formed on a surface facing the optical waveguide and the substrate, and these concave and convex portions are fitted. Then, the optical waveguide and the substrate are held in a fixed positional relationship, and at least one of the depth of the concave portion and the height of the convex portion is changed to adjust the optical coupling between the semiconductor laser and the optical waveguide. An optical module characterized by being made possible. 2. An optical coupling between the optical fiber and the optical waveguide by forming a concave portion on one of the surface of the substrate and the optical waveguide and attaching an optical fiber to the concave portion. The optical module according to claim 1. 3. A step of mounting a semiconductor laser on a substrate;
Aligning the optical waveguide in the emission end width direction of the semiconductor laser, mounting the optical waveguide on the substrate; and causing the semiconductor laser to emit light with the substrate and the optical waveguide being aligned by the process. Performing an alignment of the optical waveguide in a thickness direction of an emission end of the semiconductor laser while measuring an optical output coupled to the optical waveguide from the semiconductor laser. 4. The method for assembling an optical module according to claim 3, further comprising a step of optically coupling an optical fiber to the optical waveguide. 5. An image display device for spatially modulating light emitted from a semiconductor laser by using a spatial modulation element for display, wherein the optical module mounting the semiconductor laser and the optical waveguide on a substrate comprises the optical waveguide. And, on the facing surface of the substrate, either a concave portion or a convex portion is formed, and by fitting these concave and convex portions, the optical waveguide and the substrate are held in a fixed positional relationship, and the depth of the concave portion and the An image display device using an optical module, characterized in that at least one of the heights of the projections is changed to enable adjustment of optical coupling between the semiconductor laser and the optical waveguide.