JP2006317628A - Optical multiplexing circuit and laser beam condensing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam condensing apparatus in which the attenuation of light amount is reduced and the quality of the light beam is improved. <P>SOLUTION: The laser beam condensing apparatus comprises: a semiconductor laser bar 10; an optical multiplexing circuit 12 provided with a plurality of optical waveguides 12B in which respective light incident parts are arranged along a side of a substrate 12A and respective light emission parts are so formed on the substrate to be laminated in the thickness direction of the substrate and respective optical waveguides are composed of a single optical waveguide having no branch; and an optical fiber 14 which is optically connected to the light emission part so formed to be laminated in the thickness direction of the optical multiplexing circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical multiplexing circuit and a laser beam condensing device, and particularly condenses an optical multiplexing circuit suitable for combining laser beams emitted from a semiconductor laser bar, and a laser beam emitted from a semiconductor laser bar. The present invention relates to a laser beam condensing device.

  As a laser beam condensing device, the light emitted from the semiconductor laser bar is coupled to a plurality of optical fibers provided corresponding to each condensing point through a rod lens arranged in parallel with the semiconductor laser bar. A light collecting device that bundles all these optical fibers at the end is known (Patent Document 1).

  In the technique of Patent Document 1, since a plurality of optical fibers are used, the positions of the incident ends of the plurality of optical fibers are not accurately defined, and the optical axes of the laser light emitting part of the semiconductor laser bar and the optical fiber are not aligned. Accurate alignment is extremely difficult.

  Further, as the number of laser beam emitting portions of the semiconductor laser bar increases, the number of optical fibers increases, so that the diameter of the bundle portion of the optical fiber increases, and the intensity density of the laser beam cannot be increased.

  Also, a semiconductor laser bar having a plurality of laser beam emitting portions, and a Y-branch optical waveguide having the same number of input ports as the laser beam emitting portions of the semiconductor laser bar and having one output port on the other end surface are formed on the substrate. A semiconductor laser condensing device using an optical splitter has also been proposed (Patent Document 2).

In the laser condensing device of Patent Document 2, since the waveguide formed on the substrate is used, the problem of Patent Document 1 can be solved.
JP-A-5-93828 JP-A-7-168040

  However, since the technique of Patent Document 2 uses a Y-branch waveguide, there is always a merge part (Y-branch part) in the optical waveguide pattern, and light is emitted every time it propagates through this merge part. However, there arises a problem that the amount of light gradually attenuates. That is, at the Y branch portion where two waveguides are merged into one, the optical waveguide has a tapered shape, and light propagates through the optical waveguide while being totally reflected, but each time the light is reflected by the tapered portion, the reflection angle is increased. Eventually, the incident angle exceeds the critical angle and is emitted outside the waveguide.

  Further, in the optical waveguide of Patent Document 2, the beam quality of the laser light emitted from the output port is poor, and therefore it is difficult to narrow the emitted light small. The reason for the poor beam quality is that the aspect ratio of the output port is very large. The reason why the aspect ratio becomes large is that the semiconductor laser bar usually has a high aspect ratio at its emission part because of its high output oscillation. Therefore, in order to optically efficiently couple such a laser bar and an optical waveguide, the optical waveguide also needs to have a cross-sectional shape with a large aspect ratio, and the output port also needs to have a cross-sectional shape with a large aspect ratio. Because there is.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical multiplexing circuit and a laser beam condensing device capable of reducing the attenuation of light amount and improving the beam quality of light. And

  To achieve the above object, according to the present invention, a substrate and a light incident portion are arranged along one side of the substrate, and each of the light emitting portions overlaps the substrate in the thickness direction. And a plurality of optical waveguides each formed of a single optical waveguide that does not have a branch path in the middle.

In the present invention, when each of the light incident portions is arranged along one side of the substrate, it can be arranged in a direction inclined with respect to the surface of the substrate, and each of the light emitting portions is arranged in the thickness direction of the substrate. In the case where the light emitting portions are stacked, the light emitting portions can be arranged in a direction substantially perpendicular to the surface of the substrate.
Further, each of the light emitting parts can be arranged in a direction substantially perpendicular to the surface of the substrate so that light is emitted from each of the light emitting parts in the same direction.

  Since each of the optical waveguides of the present invention is composed of a single optical waveguide that does not have a branch path in the middle, light propagating through the optical waveguide radiates out of the optical waveguide beyond the critical angle at the branch path. In other words, the attenuation of the light amount can be reduced.

  In addition, since each of the light emitting portions of the optical waveguide is formed on the substrate so as to overlap in the thickness direction of the substrate, the aspect ratio of the light emitting portion does not increase even if each aspect ratio of the optical waveguide increases. Thereby, the beam quality of the light can be improved.

  The optical waveguide of the present invention can be formed by sandwiching the core portion between clad layers, and when the substrate is made of glass, one of the core portions can be directly formed on the substrate.

  Further, the shape of the side surface of the optical waveguide is more preferably formed so as not to exceed the critical angle of the propagating light.

  By arranging the core portion of a single optical fiber so as to face the light emitting portion of the optical multiplexing circuit, for example, the laser beam emitted from the semiconductor laser bar and multiplexed by the optical multiplexing circuit is the target portion. It can be configured as a laser beam condensing device that transmits up to.

  As described above, according to the present invention, each of the optical waveguides is composed of one optical waveguide that does not have a branch path in the middle, and each of the light emitting portions of the optical waveguide is in the thickness direction of the substrate. Since they are formed on the substrate so as to overlap, the effects of reducing the attenuation of the amount of light and improving the light beam quality can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings by applying the present invention to a laser condensing device that condenses laser light at one point using the photosynthesis circuit of the present invention.

  As shown in FIG. 1, the laser condensing apparatus of the present embodiment includes a semiconductor laser bar 10 having a plurality (five in the drawing) of laser emitting portions 10A and the same number of incident portions as the number of laser emitting portions (five in the drawing). ), And an optical multiplexing circuit 12 having a plurality of optical waveguides laminated so that the emission part is overlapped in the thickness direction of the substrate, and a single optical fiber having a core diameter that encompasses the emission part of the optical multiplexing circuit 12 14.

  As shown in FIGS. 1 and 5, the plurality of laser beam emitting portions 10A of the semiconductor laser bar 10 are arranged in a straight line, and each emits laser beams in the same direction. Since the semiconductor laser bar 10 is manufactured by a photo process, the position of the laser beam emitting portion is accurately defined.

  As shown in FIG. 2, the optical multiplexing circuit 12 includes a single substrate 12A formed of a glass substrate or the like, and a layered core portion 12B having the same number (5 in the drawing) as the number of laser light emitting portions of the laser bar. The optical waveguide is formed by being laminated on the substrate 12A with the clad layer 12C interposed therebetween. The laser light incident portions of the respective optical waveguides are spaced apart by a thickness dc of the cladding layer 12C in the thickness direction of the substrate, and are arranged at a predetermined interval D in the width direction. In addition, each optical waveguide except the central optical waveguide is formed so as to be bent symmetrically with respect to the central optical waveguide from the laser light incident portion to the laser light incident portion. Are arranged in a direction inclined with respect to the surface of the substrate along one side of the substrate, and each of the laser beam emitting portions of the optical waveguide is laminated with the clad layer 12C sandwiched in the thickness direction of the substrate. They are arranged in a direction substantially perpendicular to the surface.

  Therefore, the positional relationship of each core part 12B is located in the same position as the laser beam emitting part of the semiconductor laser bar in the laser beam incident part, and is positioned so as to overlap vertically in the emitting part. The pattern of each core part is formed in a simple single shape with no branch part on the way from the incident part to the emission part. Accordingly, each optical waveguide is formed independently so that laser light does not propagate between adjacent optical waveguides. By setting it as such a pattern, the optical loss which arises by the combined pattern comprised by optical waveguides, such as the Y branch shape produced by one layer as usual and a rake type shape, can be made almost zero.

  In the present embodiment, the central optical waveguide is formed in a straight line, and each of the outermost optical waveguides is an arc-shaped optical waveguide having a radius of curvature R (for example, 10 mm) from the incident portion to the outgoing portion. It is configured to be connected so as to be on the opposite side across the optical waveguide. Each of the optical waveguides positioned between the central optical waveguide and the outermost optical waveguide is formed so that the curvature radius R is larger than the curvature radius of the outermost optical waveguide. By forming the shape of the optical waveguide, i.e., the pattern, with the radius of curvature as described above, the incident angle of the laser light propagating in the optical waveguide can be prevented from exceeding the critical angle.

  Further, the cross-sectional dimension of each optical waveguide is formed slightly larger than the area of the laser light emitting portion 10A of the semiconductor laser bar, so that highly efficient coupling with the laser light is facilitated. For example, when the shape of the incident portion of the optical waveguide is a rectangular shape having a width of 110 μm and a height of 10 μm, the laser light emitted from the semiconductor laser bar can be efficiently incident on the optical multiplexing circuit.

  Such an optical multiplexing circuit can be manufactured in the order of steps shown in FIG. Here, a case where a glass substrate is used as the substrate will be described as an example. A core layer is formed on one glass substrate, and is patterned into the shape of a waveguide by photolithography and etching, thereby forming one outermost core portion 12B of a predetermined pattern. Next, a cladding layer 12B having a refractive index smaller than that of the core portion 12B is formed so as to cover the core portion and the glass substrate 12A. Next, a core layer is formed on the clad layer, and the core layer is patterned into a waveguide shape, thereby forming a core portion adjacent to the outermost core portion.

  The process of forming the core layer 12B and then forming the cladding layer 12C thereon is repeated a number of times corresponding to the number of laser light emitting portions of the semiconductor laser bar, thereby corresponding to the number of laser light emitting portions of the semiconductor laser bar. As many optical waveguides as possible are produced. In this case, the core portion is formed so as to increase in height from the outermost one core portion to the outermost other core portion, and each of the core portions is arranged in a straight line.

  The reason why the glass substrate is used here is that the core layer may be formed by forming the core layer at the beginning of the production process. In addition to the glass substrate, a substrate made of a polymer material such as Si, polyimide, or PMMA can also be used. However, when using a substrate having a refractive index higher than that of the core layer to be used or a non-transparent substrate, the cladding is used. After the layer is first made, it is necessary to make a core on it.

  The core portion and the clad layer can be made of various materials such as polymers such as PMMA and polyimide, and glass, but polymer materials are suitable because they are easy to produce. As a method for producing the core layer and the clad layer, a spin coating method, a dip coating method, or the like can be used. When a glass material is used, the core layer and the cladding layer can be produced by a flame volume method, a sputtering method, an ion exchange method, or the like.

  Since the optical multiplexing circuit 12 produced as described above is produced by a photo process, the position of the laser light incident portion is accurately defined. The optical multiplexing circuit 12 is optically connected to the semiconductor laser bar, but the core portion of the optical multiplexing circuit incident portion has the same distance D as the laser light emitting portion of the semiconductor laser bar, but the height gradually increases. Is different. Therefore, at the time of connection, as shown in FIG. 5, it is necessary to align the optical axes by arranging either the optical multiplexing circuit or the semiconductor laser bar at an angle of θc.

  In the present embodiment, the fact that the incident efficiency is not impaired will be described with specific numerical values. A general semiconductor laser bar is configured by arranging a plurality (for example, five) of laser light emitting portions (light emitting portions) having a width of 0.1 mm and a height of 1 μm at intervals of 100 μm. The most efficient optical multiplexing circuit for such a semiconductor laser bar has a core part having a width of 110 μm and a height of 10 μm stacked in the same number as the semiconductor laser bar with a cladding layer having a thickness of 5 μm interposed therebetween. It is. In order to optically connect them, one of them is tilted by θc so that the laser beam emitting portion and the core portion of the semiconductor laser bar overlap each other. Here, the case where the optical multiplexing circuit is tilted will be described as an example. In this case, the angle θc is expressed by the following equation (1).

Here, do is the thickness of the core portion, dc is the thickness of the cladding layer, D is the interval between the core portions, and D is the same as the interval between the laser beam emitting portions of the laser bar. In this example, θc is about 4.3 deg. At this time, the coupling loss between the semiconductor laser bar and the optical multiplexing circuit occurs when the cross section of the laser light emitting portion of the semiconductor laser bar deviates from the cross section of the optical multiplexing circuit core, and the angle θ _loss at which coupling loss starts to occur is expressed by the following equation (2) Is required.

  Here, h is the thickness of the laser beam emitting portion of the semiconductor laser bar, and We is the width of the laser beam emitting portion of the semiconductor laser bar.

The angle θ _{loss at} which coupling loss starts to occur is 5.1 deg in the above example, and even if the core part is inclined by 4.3 deg, the core part cross-section completely includes the light-emitting part cross-section, and therefore laser light emission All the laser beams emitted from the unit can be received.

The optical fiber 14 can receive all of the emitted laser light by using the one having a core part with a diameter that encompasses all the core laminated parts laminated on the emitting part of the optical multiplexing circuit 12, Further, the laser beam can be transmitted with almost no loss to the optical fiber emitting portion. As such an optical fiber, it is possible to use an optical fiber made of general SiO ₂ or plastic.

  As described above, according to the present embodiment, the waveguide pattern of the optical multiplexing circuit is constituted by a single simple pattern having no joining portion. Laser light is not emitted outside the optical waveguide in the middle of the optical waveguide, and a plurality of laser lights can be condensed with low loss.

  Moreover, since the core part is laminated | stacked and the core lamination | stacking part is formed in the output part of an optical multiplexing circuit, an aspect ratio becomes small and the light beam quality after condensing can be made high.

  In the present embodiment, when each of the laser beam emitting portions is arranged in a direction substantially perpendicular to the surface of the substrate, the laser beam is emitted so that light is emitted in the same direction from each of the laser beam emitting portions. It is preferable to arrange each of the light emitting portions. By arranging in this way, the optical fiber is optically coupled to the emission part of the optical multiplexing circuit 12 so that the axis of the optical fiber and the direction of the laser light emitted from each of the laser light emission parts are substantially parallel. Can do. As a result, when the laser beam emitted from the optical multiplexing circuit enters the optical fiber, it enters at an angle less than the critical angle, and the optical loss due to the incident laser beam exceeding the critical angle can be suppressed. it can.

  Next, a modification of the present embodiment will be described. FIG. 6 shows a first modified example in which a rod lens 16 is disposed between the semiconductor laser bar 10 and the optical multiplexing circuit 12 in order to efficiently enter the laser light emitted from the semiconductor laser bar 10 by the optical multiplexing circuit 12. It is shown. In this modification, the laser light is condensed by the rod lens 16 in a direction orthogonal to the length direction of the rod lens, so that the laser light can be efficiently incident on each core portion of the optical multiplexing circuit.

  FIG. 7 shows a second modification in which light emitted from the optical fiber array 20 is condensed at one point by an optical multiplexing circuit instead of the semiconductor laser bar, and FIG. 8 shows an m × n Y-branch optical waveguide. 3 shows a third modification in which the light emitted from the optical circuit 22 having light is condensed at one point by the optical multiplexing circuit 12.

It is a top view of the laser beam condensing device of an embodiment of the invention. It is incident part side sectional drawing of the photosynthesis circuit of embodiment of this invention. It is an emission part side sectional view of a photosynthesis circuit of an embodiment of the invention. It is process drawing which shows the production method of the photosynthesis circuit of embodiment of this invention. It is a figure explaining the optical connection state of a semiconductor laser bar and a photosynthesis circuit. It is a top view which shows the 1st modification of embodiment of this invention. It is a top view which shows the 2nd modification of embodiment of this invention. It is a top view which shows the 3rd modification of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor laser bar 12 Optical multiplexing circuit 14 Optical fiber

Claims (8)

A substrate,
Each of the light incident portions is arranged along one side of the substrate, and each of the light emitting portions is formed on the substrate so as to overlap in the thickness direction of the substrate, and each has a branch path in the middle. A plurality of optical waveguides composed of a single optical waveguide,
Including optical multiplexing circuit.   The optical multiplexing circuit according to claim 1, wherein the optical waveguide is formed by sandwiching a core portion between clad layers.   The optical multiplexing circuit according to claim 2, wherein the substrate is made of glass, and one of the core portions is formed directly on the substrate.   The optical multiplexing circuit according to any one of claims 1 to 3, wherein the optical multiplexing circuit is formed in a shape that does not exceed a critical angle of light propagating through a shape of a side surface of the optical waveguide.   5. Each of the light incident portions is arranged in a direction inclined with respect to the surface of the substrate, and each of the light emitting portions is arranged in a direction substantially perpendicular to the surface of the substrate. The optical multiplexing circuit according to any one of the above.   6. Each of the light emitting portions is arranged in a direction substantially perpendicular to the surface of the substrate so that light is emitted in the same direction from each of the light emitting portions. 2. An optical multiplexing circuit according to item 1. The optical multiplexing circuit according to any one of claims 1 to 6,
A single optical fiber disposed such that the core portion faces the light emitting portion of the optical multiplexing circuit;
A laser beam condensing device. A semiconductor laser bar;
The optical multiplexing circuit according to any one of claims 1 to 6, wherein each of the light incident portions is disposed so as to face a laser light emitting portion of the semiconductor laser bar,
A single optical fiber disposed such that the core portion faces the light emitting portion of the optical multiplexing circuit;
A laser beam condensing device.

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