JPH06196816A - Laser diode with lens and manufacture thereof - Google Patents

Abstract

PURPOSE:To fix a lens array without adjusting the parallelism and clearance of a laser diode chip and the lens array by forming the clearance avoiding the contact of the outgoing section of laser beams and the lens array between the outgoing section of the laser beams of at least the laser diode chip and the lens array. CONSTITUTION:An indentation 14 is formed as a clearance avoiding the contact of the outgoing section of the laser beams of a laser diode chip with a lens array. Since a laser diode array 1 and the lens array 13 with the indentation are fixed with the small clearance, a distance between the light-emitting point of the laser diode array 1 and the principal point of a lens can be set at an optimum value in an unadjusted manner by properly selecting the substrate thickness of the lens array 13 with the indentation when the high refractive index section 15 of the lens array 13 with the indentation is formed on the reverse side to the laser diode array 1. Accordingly, parallelism between the laser diode array and the lens array and a distance in the optical axis direction need not be adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode chip having a plurality of laser beam emitting portions, which is required as a signal light source when transmitting parallel digital data or the like using an optical fiber in a computer, an exchange or the like. The present invention relates to a laser diode with a lens provided with.

[0002]

2. Description of the Related Art FIG. 6, for example, entitled "Prototype of Multi-Channel LD / PD Array Module" by Moriya et al.
69) is a configuration example of a conventional laser diode array with a lens including a laser diode chip having a plurality of laser light emitting portions. In the figure, 1 is a laser diode array, 2 is a laser diode array 1
Of the active layer, 3 is output light, 4 is a lens array, 5 is an optical fiber terminal, 6 is a carrier, 7 is a submount, 8 is a high melting point solder, and 9 is a low melting point solder.

FIG. 7 is a diagram showing a conventional method for assembling a laser diode array with a lens. In the figure,
Reference numeral 10 is a hot plate, 11 is a laser diode array fine movement device, 12 is a lens array fine movement device, and other reference numerals are the same as those in FIG.

Next, the operation will be described. The output light 3 emitted from the active layer 2 provided in parallel with the laser diode array 1 is transmitted by the lens array 4 which is an assembly of condensing optical systems to the incident end face of the optical fiber terminal 5 in front of the lens array 4. Is focused on. The carrier 6 is a metal structural member for fixing the relative positions of the laser diode array 1 and the lens array 4, and the submount 7 is a thermal strain applied to the laser diode array 1 during assembly and use. Is a cushioning member for alleviating the above, and a material having physical properties similar to those of the substrate material of the laser diode array 1 such as silicon is usually used.

[0005]

Since the conventional laser diode array with a lens is constructed and assembled as described above, there are the following problems.

The first problem relates to the complexity of the step of aligning the laser diode array 1 and the lens array 4. In order to collect the output light 3 of the laser diode array 1 with the lens array 4 and efficiently enter it into the optical fiber terminal 5, in order to convert the radiation pattern of the laser diode into the propagation mode of the optical fiber, a predetermined image magnification is used. It is necessary to adjust the positional relationship between the laser diode array 1, the lens array 4 and the optical fiber terminal 5 with high accuracy so as to satisfy the above-mentioned image forming relationship. Usually, this adjustment is
Due to the image magnification, the position of the optical fiber terminal is adjusted so that a predetermined output can be obtained after the adjustment between the laser diode and the lens, which has a narrow adjustment range.

If the laser diode has only one active layer and one lens and one optical fiber terminal, it is sufficient to adjust the distance between them and the position in the direction orthogonal to the optical axis. When condensing the output light 3 of the laser diode array 1 with the lens array 4, the parallelism between the laser diode array 1 and the lens array 4 is also adjusted in order to equalize the distance between all the light sources and the lens. There must be. Therefore, in the configuration of the conventional laser diode array with a lens shown in FIG.
Since the parallelism of the end surface of the laser diode array 1 and the distance in the optical axis direction with respect to the end surface of the lens array 4 must be adjusted, the position of the lens array 4 in the direction orthogonal to the optical axis must be adjusted, resulting in a complicated assembling process.

The second problem relates to stability and reliability of size and characteristics. In the configuration of the conventional laser diode array with a lens shown in FIG. 6, the laser diode array 1 and the lens array 4 are fixed via a carrier 6, and the size of the carrier 6 reduces the size of the laser diode array with a lens. Was restricted. If a material having a high thermal conductivity such as copper is used as the carrier 6 to improve heat dissipation to the laser diode array 1, the thermal expansion coefficient of the carrier 6 is higher than that of the laser diode array 1, the submount 7, and the lens array 4. Is significantly increased, and large thermal strain is applied to the joint between the submount 7 and the carrier 6 and the joint between the lens array 4 and the carrier 6, impairing the stability and reliability of the laser diode array with lenses. Becomes

The third problem relates to the accuracy and time required for the step of aligning the laser diode array 1 and the lens array 4. This will be described with reference to the figure showing the conventional assembling method of FIG. First, after the entire laser diode array with lenses is heated by the hot plate 10 to melt the high melting point solder 8, the laser diode array fine movement device 11 is used to adjust the parallelism and distance to the end face of the carrier 6 of the laser diode array 1. adjust. next,
The temperature of the hot plate 10 is lowered so that the high melting point solder 8 is in the solidified state and the low melting point solder 9 is in the molten state, and the lens array fine movement device 12 is used to move the position of the lens array 4 in the direction orthogonal to the optical axis to the optical fiber terminal 5. The incident light of is adjusted to a predetermined value. After this adjustment is completed, the hot plate 10
Lower the temperature to room temperature and take out the laser diode array with lens.

Conventionally, since the high melting point solder 8 is assembled by the above method, for example, the melting point is 280 ° C.
AuSn solder, low melting point solder 9 has, for example, a melting point of 18
When PbSn solder of 3 ° C. is used, the temperature of the hot plate 10 must be changed by at least 150 degrees with respect to room temperature even after the final alignment, and thermal alignment of the hot plate 10 causes alignment. In addition to the error, it takes a considerable time for heating and cooling.

The present invention has been made in order to solve the above-mentioned problems. The position of the laser diode array 1 and the lens array 4 can be easily and accurately aligned with each other, and the size is small, highly stable, and highly stable. The objective is to realize a reliable laser diode array with a lens.

[0012]

According to a first aspect of the present invention, there is provided a laser diode with a lens, wherein a laser diode chip having a plurality of laser light emitting portions and one end surface of the laser diode chip on the laser light emitting side are aligned. And a mount for holding the laser diode chip, and a plurality of lenses formed on the substrate that is held on the one surface of the mount and transmits the laser light, and each laser light of the laser diode chip is placed at a predetermined position. A lens array for condensing light is provided, and a gap is provided at least between the laser light emitting portion of the laser diode chip and the lens array to avoid contact between the emitting portion and the lens array.

A lens-equipped laser diode according to a second aspect of the present invention is arranged such that a laser diode chip having a plurality of laser light emitting portions and one end face of the laser diode chip on the laser light emitting side are aligned with each other. A mount for holding, and a plurality of lenses that are held on the one surface of the mount and formed by providing a refractive index distribution on a substrate that transmits laser light, and place each laser light of the laser diode chip at a predetermined position. A lens array for condensing light, and the refractive index distribution of the lens array is formed equivalent to a convex lens having a convex surface on the laser diode chip side.

According to a third aspect of the present invention, there is provided a method for manufacturing a laser diode with a lens, wherein a laser diode chip having a plurality of laser light emitting portions and an end face of the laser diode chip on a laser light emitting side are arranged in a plane. A mount that holds the diode chip and a plurality of lenses that are held on the one surface of the mount by solder and are formed on a substrate that transmits the laser light, and collect each laser light of the laser diode chip at a predetermined position. In manufacturing a laser diode with a lens equipped with a lens array for illuminating, a laser diode chip is fixed to the mount by aligning one end of the laser diode emitting side of the laser diode chip with the one surface of the mount, and then mounting the lens array substrate. The transmitted laser light is incident from the side opposite to the mount of the lens array substrate. It was dissolved by heating the solder provided between the lens array and the mount is for fixing the lens array in the mount.

[0015]

According to the invention of claim 1, there is a gap at least between the laser light emitting portion of the laser diode chip and the lens array to avoid contact between the emitting portion and the lens array. The lens array can be fixed directly to the mount without adjusting the parallelism and spacing between the lens array and the lens array.

According to the second aspect of the present invention, since the refractive index distribution of the lens array is formed equivalently to a convex lens having a convex surface on the laser diode chip side, the position of the laser diode chip and the lens array in the direction orthogonal to the optical axis. The precision required for alignment is relaxed, and a high-performance laser diode with a lens can be easily obtained without adjusting the distance between the laser diode chip and the lens array.

According to the invention of claim 3, the laser diode chip is fixed to the mount by aligning the end surface of the laser diode chip on the laser light emitting side with the one surface of the mount, and the laser light transmitted through the substrate of the lens array is passed through the lens. It is incident from the side opposite to the mount of the array substrate, the solder provided between the lens array and the mount is heated and melted, and the lens array is fixed to the mount. Can be efficiently and uniformly heated.

[0018]

EXAMPLES Example 1. FIG. 1 is a configuration diagram of a laser diode with a lens according to the present invention, in which 1 is a laser diode array, 2 is an active layer of the laser diode array 1, and 3 is an active layer.
Is output light, 5 is an optical fiber terminal, 7 is a submount, 8
Is a high-melting-point solder, 9 is a low-melting-point solder, and 13 is a lens array with a depression, and a depression 14 is provided as a gap for avoiding contact between the laser light emitting portion of the laser diode chip and the lens array.

The basic operation of this laser diode with lens is the same as that of the conventional example shown in FIG. 6, and the output light 3 emitted from the active layer 2 provided in parallel with the laser diode array 1 is output. Is condensed on the incident end face of the optical fiber terminal 5 by the lens array 13 with a depression which is an assembly of condensing optical systems.

Next, the reason why it becomes unnecessary to adjust the parallelism between the laser diode array and the lens array and the distance in the optical axis direction will be described. FIG. 2 is a side view of the configuration of the laser diode with lens according to the present invention. In the figure, 15 is a high refractive index portion formed in the lens array 13 with depressions, and other reference numerals are the same as those in FIG.

In the assembling of the laser diode with a lens shown in FIG. 2, when the high melting point solder 8 is in a molten state, the laser diode array 1 and the submount 7 are lightly pressed against a flat jig and then cooled. The array 1 and the submount 7 can be fixed so that the end faces thereof are aligned with each other. Then, the lens-equipped laser diode is completed by adjusting and then fixing the position of the lens array 13 with depressions in the direction orthogonal to the optical axis with respect to the laser diode array 1.

In the laser diode with lens assembled by the above method, the laser diode array 1
Since the lens array 13 with recesses is fixed with an extremely small gap, the high refractive index portion 15 of the lens array 13 with recesses is provided on the opposite side of the laser diode array 1 as shown in FIG. For example, by appropriately selecting the substrate thickness of the lens array with depressions 13, the distance between the light emitting point of the laser diode array 1 and the principal point of the lens can be set to an optimum value without adjustment. Therefore, it is not necessary to adjust the parallelism between the laser diode array and the lens array and the distance in the optical axis direction.

Next, the function of the recesses 14 provided in the lens array 13 with recesses will be described. A laser diode generally uses cleavage planes at both ends of the chip as a reflection surface of a resonator, and even if the shape and characteristics of the cleavage plane are slightly changed, the characteristics of the laser diode are deteriorated. Also, if there is a reflection point outside the laser diode through a gap similar to the wavelength, interference between the cleavage surface of the laser diode and this reflection point effectively changes the reflectance of the laser diode resonator. The characteristics of the laser diode become unstable. As described above, in the laser diode with lens according to the present invention, since the laser diode array 1 and the lens array with depression 13 are fixed with an extremely small gap, they contact each other and damage the cleavage surface of the laser diode. In order to prevent the laser diode from deteriorating or destabilizing the characteristics of the laser diode due to the interference between the surface of the lens array and the cleavage surface of the laser diode, the surface of the lens array near the active layer of the laser diode is prevented. It is desirable to maintain a constant distance between the laser diode array and the laser diode array. The depression 14 is provided for these reasons. It is desirable that the bottom of the recess 14 be coated with a non-reflective coating because the interference between the surface of the lens array with recess 13 and the cleavage plane of the laser diode can be further reduced.

Next, the relationship between the recesses 14 provided in the recessed lens array 13 and the high refractive index portion 15 will be described.
The lens array of this embodiment is made by implanting refractive index-enhancing ions into a glass substrate through a mask having regular holes. At this time, depending on the type of ions, the ion concentration of the glass substrate may have a distribution upon completion of the ion implantation process, which may cause a concentric refractive index distribution inside the high refractive index portion 15. Depression 1
When 4 reaches the high-refractive-index portion 15 into which the ions are implanted, the refractive index distribution is abruptly disturbed, so that the condensing characteristics of the lens array are deteriorated. Therefore, it is necessary to set the depth of the depression 14 within a range that does not cover the high refractive index portion 15.

Next, the relationship between the shape of the high refractive index portion 15 provided on the lens array with depressions 13 and the fixing position of the optical fiber terminal 5 will be described. FIG. 3 shows a coupling optics having spherical aberration, which was presented by Tachikawa et al. In the “Communication Study of Spherical Aberration in Semiconductor Laser Multimode Fiber Coupling System” at the IEICE Communication Systems Research Group (Announcement No. CS83-177). It is the optical axis direction position dependency of the optical fiber terminal of the optical axis orthogonal allowable axis shift amount of the optical fiber terminal in the system. In the figure, 20 is a laser diode, 21 is a coupling lens having spherical aberration, and 5 is an optical fiber terminal.
In this figure, the absolute value of the optical output is reduced by moving the optical fiber terminal slightly away from the position where the maximum optical output is obtained, but the amount of change in the optical output with respect to the positional deviation of the optical fiber terminal in the direction orthogonal to the optical axis is small. Has been shown to be less.

As shown in FIG. 2, in the laser diode with lens according to the present invention, the high refractive index portion 15 of the lens array with depressions 13 is provided on the opposite side of the laser diode array 1 and has a refractive index distribution. Is equivalent to a plano-convex lens having a convex surface on the laser diode array 1 side.

Generally, in a coupling system of a laser diode and an optical fiber, since the radiation angle of the laser diode is larger than the light receiving angle of the optical fiber, it is constructed with a magnification of about 3 to 5 times. Spherical aberration of the plano-convex lens becomes larger when the convex surface is directed rather than when the convex surface is directed toward the laser diode array 1 side, because the steeply bent ray becomes larger.

In the laser diode with a lens according to the present invention, the optical axis direction positional dependency of the optical fiber terminal of the above-mentioned permissible optical axis orthogonal displacement amount of the optical fiber terminal remarkably appears, and the optical fiber terminal has the maximum optical power. By moving away from the position where the output is obtained, the absolute value of the optical output decreases, but the amount of change in the optical output with respect to the positional deviation of the optical fiber terminal in the direction orthogonal to the optical axis decreases, and the allowable axis deviation can be increased.

Since a transmission distance is short in a computer or a switchboard, a small light output may be used as a signal light source when transmitting parallel digital data or the like using an optical fiber. On the other hand, a large tolerance for positional deviation of the optical fiber terminal in the direction orthogonal to the optical axis simplifies the assembly process, so it is not possible to fix the optical fiber terminal at a position away from the position where the maximum optical output is obtained. It is useful.

Example 2. FIG. 4 is an explanatory view showing a method for aligning and fixing the lens array in the method for manufacturing a laser diode with a lens according to the present invention. The laser diode with a lens having the configuration of the first embodiment will be described. In the figure, 16 is a YAG laser device that generates a laser beam that passes through the substrate of the lens array 13 with depressions, 17 is a YAG laser beam, 18 is a laser beam condenser lens, and other reference numerals are the same as in FIG. .

In order to position and fix the recessed lens array 13 to the laser diode array 1 and the submount 7 which are fixed so that their respective end faces coincide with each other by the method described above, the YAG laser device 16 emits light. The YAG laser beam 17 to be used is a laser beam condensing lens 18
Is used to focus light on the low melting point solder 9 provided between the lens array with depressions 13 and the submount 7, and the low melting point solder 9 is brought into a molten state. The position of 13 in the direction orthogonal to the optical axis is adjusted so that the incident light on the optical fiber terminal 5 has a predetermined value, and then the YAG laser beam 17 is blocked and the low melting point solder 9 is solidified.

In the method of aligning and fixing the lens array in the laser diode with a lens according to the present invention, since the YAG laser beam 17 can be irradiated from a direction in which all of the low melting point solder 9 can be seen, the low melting point solder 9 can be efficiently and uniformly distributed. Can be heated. Further, since the low melting point solder 9 can be locally heated, the thermal deformation of the assembling apparatus is small, and the alignment error caused by this is small. Further, unlike the conventional case, since there is no portion having a large heat capacity such as a hot plate, the temperature can be raised and cooled in a short time, and the assembling time can be shortened.

Example 3. In addition, in the above-described embodiment, the lens array with depressions 13 has been described by taking as an example a glass substrate into which ions for increasing the refractive index are implanted.
As shown in, a lens array equivalent to a plano-convex lens having a convex surface on the side opposite to the laser diode array 1 was processed on a flat plate made of a transparent material at a target wavelength such as glass or silicon to give a lens effect, You may use the convex lens array 19 with a depression.

In the above embodiment, the recessed lens array 13 has a recess 1 as a gap for avoiding contact between the laser light emitting portion of the laser diode chip and the lens array.
Although the example in which 4 is provided is shown, the present invention is not limited to this, and the substrate of the lens array may be cut out or a recess may be formed in the laser diode chip.

[0035]

According to the first aspect of the present invention, the lens array can be directly fixed to the mount without adjusting the parallelism and the distance between the laser diode chip and the lens array. According to the invention of claim 2, the required accuracy of alignment between the laser diode chip and the lens array in the direction perpendicular to the optical axis is relaxed, and a high-performance laser diode with a lens is provided without adjusting the distance between the laser diode chip and the lens array. Is easily obtained. According to the invention of claim 3, the solder provided between the lens array and the mount can be efficiently and uniformly heated.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a side view of the configuration of a laser diode with a lens according to the present invention.

FIG. 3 is a diagram showing the position dependency of the optical axis direction allowable axis deviation amount of the optical fiber terminal in the optical axis direction of the optical fiber terminal in the coupling optical system having spherical aberration.

FIG. 4 is an explanatory diagram showing a method of aligning and fixing a lens array in the method of manufacturing a laser diode with a lens of the present invention.

FIG. 5 is a configuration diagram showing a third embodiment of the present invention.

FIG. 6 is a configuration diagram of a conventional laser diode array with a lens.

FIG. 7 is an explanatory diagram showing a conventional method for assembling a laser diode array with a lens.

[Explanation of symbols]

 1 Laser Diode Array 2 Active Layer 3 Output Light 4 Lens Array 5 Optical Fiber Terminal 6 Carrier 7 Submount 8 High Melting Point Solder 9 Low Melting Point Solder 10 Hot Plate 11 Laser Diode Array Fine Moving Device 12 Lens Array Fine Moving Device 13 Dimpled Lens Array 14 Recess 15 High refractive index portion 16 YAG laser device 17 YAG laser beam 18 Laser beam condensing lens 19 Convex lens array with recess

Claims (3)

[Claims] 1. A laser diode chip having a plurality of laser light emitting portions, a mount that is arranged flush with an end face of the laser diode chip on the laser light emitting side, and holds the laser diode chip. A lens array that is held on one surface and that has a plurality of lenses formed on a substrate that transmits laser light, and that has a lens array that focuses each laser light of the laser diode chip at a predetermined position, and at least the laser diode chip A lens-equipped laser diode having a gap between a laser light emitting portion and a lens array for avoiding contact between the laser emitting portion and the lens array. 2. A laser diode chip having a plurality of laser beam emitting portions, a mount which is arranged flush with an end face of the laser diode chip on the laser beam emitting side, and holds the laser diode chip, and the mount described above. A lens array that is held on one surface and has a plurality of lenses formed by providing a refractive index distribution on a substrate that transmits laser light, and that collects each laser light of the laser diode chip at a predetermined position. A lens-equipped laser diode, wherein the refractive index distribution of the lens array is formed equivalent to a convex lens having a convex surface on the laser diode chip side. 3. A laser diode chip having a plurality of laser light emitting portions, a mount that is arranged flush with an end face of the laser diode chip on the laser light emitting side, and holds the laser diode chip, and the mount described above. A lensed laser that has a plurality of lenses formed on a substrate that is held by solder on one surface and that transmits laser light, and that has a lens array that focuses each laser light of the laser diode chip at a predetermined position When manufacturing a diode, the laser diode chip is fixed to the mount by aligning the laser light emitting side end face of the laser diode chip with the mount surface, and the laser light that passes through the lens array substrate is mounted on the lens array substrate. Light from the side opposite to, and apply solder provided between the lens array and mount. A method of manufacturing a laser diode with a lens, which comprises heating and melting to fix a lens array to a mount.