JP2004022918A - Method for manufacturing laser module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain superior characteristics and reliability by removing contaminants in a container, in a laser module constituted by installing a semiconductor laser element in a sealed container. <P>SOLUTION: A heat sink 4 in which the semiconductor laser element 6 is bonded to a sub-mount 5 and a monitoring photodiode 10 are installed on a stem 1. The stem is installed on a fixed table 65 in a vacuum tank 60 of a plasma irradiation device. After discharging air (63) until an initial degree of a vacuum becomes 1×10<SP>-2</SP>Torr or below from the atmosphere, a microwave 62 and an argon gas 61 of 1×10<SP>-2</SP>-1×10<SP>-1</SP>Torr are introduced, and a power of about 10-1,000 W is applied to generate plasma 64, for performing plasma irradiation for about 60 minutes or less. Lastly, a dry air (N<SB>2</SB>= 80%, O<SB>2</SB>= 20%) atmosphere is ring-weld-sealed with the container 2 provided with a glass window 3 to which nonreflective coating is applied. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a laser module in which a semiconductor laser element is installed in a container and hermetically sealed.
[0002]
[Prior art]
A laser module in which a semiconductor laser element, a collimator lens, a condensing lens, an optical fiber, and the like are sealed in a sealed container is known. In this laser module, contaminants remaining in the sealed container are semiconductor lasers. There is a problem in that it adheres to optical components such as the emission end face of the element, lens and optical fiber, and deteriorates laser characteristics. Examples of the pollutant include hydrocarbons mixed in from the atmosphere of the production process, and it is known that the hydrocarbons are polymerized or decomposed by laser light and adhered.
[0003]
In order to solve this problem, various methods shown below have been proposed. For example, in JP-A-11-167132, in order to prevent a decrease in the output of laser light of 400 nm or less, it is effective to reduce the amount of hydrocarbon in the container to 0.1% or less. It is described that deposition on an optical component or the like due to photolysis can be prevented. It has also been proposed that the sealed atmosphere be dry air, and a deposit removal effect is expected by a photochemical reaction between oxygen in the atmosphere and deposited hydrocarbon.
[0004]
In US Pat. No. 5,392,305, in order to prevent the adhesion of contaminants to the end face of the semiconductor laser element due to the photolysis of an organic gas such as hydrocarbon, 100 ppm or more of oxygen intended to decompose this gas is sealed. It is described that it is mixed into the stop gas.
[0005]
Japanese Patent Laid-Open No. 11-87814 describes that long-term reliability can be ensured by degreasing and washing away contaminants such as oil.
[0006]
On the other hand, in Japanese Patent Application No. 2000-336850, the present applicant has proposed a laser module using a GaN-based semiconductor laser element having an oscillation wavelength of 350 to 450 nm. However, short-wavelength laser light has high energy. The hydrocarbon polymerized or decomposed in the module has a high probability of adhering to the end face of the semiconductor laser element or the optical component, which is a particular problem.
[0007]
[Problems to be solved by the invention]
As shown in the above-mentioned US Pat. No. 5,392,305, the deposition of pollutants generated by the reaction between the laser beam and the hydrocarbon is decomposed into CO ₂ and H ₂ O in a gas atmosphere containing a certain amount or more of oxygen. It is solved by.
[0008]
However, in this type of deposit, not only hydrocarbons but also silicon compounds have been confirmed, and it has been found that the silicon compounds cannot be decomposed and removed only by containing oxygen in the atmosphere. Since the deposits of hydrocarbons and silicon compounds generate optical absorption, there is a problem that reliability over time in continuous oscillation is significantly impaired. The silicon compound to be deposited is a photochemical reaction between an organic compound gas containing Si such as a siloxane bond (Si—O—Si) or a silanol group (—Si—OH) (hereinafter referred to as an organosilicon compound) and laser light. And the presence of oxygen in the atmosphere has the effect of increasing the reaction rate. The silicon compound as used herein refers to a compound having any structure including silicon regardless of organic or inorganic, and includes inorganic SiOx and organic silicon compounds.
[0009]
The generation source is a gas emitted mainly from a silicone-based material used in an arbitrary place in the laser module manufacturing process. This may be adhered to the surface of each component in the laser module, and when the module is used in a sealed state, it is contained in a small amount in the sealing gas. In order to manage the gas components during the manufacturing process, it cannot be completely removed by installing a normal clean room or a sealed gas purifier, and a large capital investment is required. In addition, it is unavoidable that the above compound is mixed from the manufacturing process atmosphere as described above, even through a degreasing or washing process of oil or the like as disclosed in JP-A-11-87814. Since cleaning uses liquid organic substances, it is necessary to manage impurities in the drying process. In addition, it is necessary to select a cleaning agent that does not dissolve the adhesive used to fix the semiconductor laser element, optical member, etc. in the container, and this often contradicts the maintenance of the cleaning ability of organic substances adhering to the component surface. .
[0010]
Hydrocarbon compounds, silicon compounds and the like adhering to the components in the laser module can be removed by decomposition and evaporation by heat treatment at a temperature of 200 ° C. or higher, preferably 300 ° C. or higher. However, heat treatment requires several to several tens of hours of processing time, and when fixing the components in the module with an organic adhesive, the mechanical properties due to the thermal deterioration of the adhesive deteriorate, so this method should be used. I can't.
[0011]
In view of the above circumstances, the present invention manufactures a highly reliable laser module in which contaminants in a container are satisfactorily removed in a laser module manufacturing method in which a semiconductor laser element is disposed in a container and hermetically sealed. It is intended to provide a way to do this.
[0012]
[Means for Solving the Problems]
A first laser module manufacturing method of the present invention is a laser module manufacturing method in which a semiconductor laser element is installed in a container and hermetically sealed. At least the container and the semiconductor laser are sealed before the container is hermetically sealed. The element is irradiated with plasma.
[0013]
In a second laser module manufacturing method of the present invention, a semiconductor laser element, an optical fiber, and an optical member for inputting laser light emitted from the semiconductor laser element into the optical fiber are installed in a container. A method for manufacturing a hermetically sealed laser module, wherein plasma is irradiated to at least the container, the semiconductor laser element, the optical fiber, and the optical member before the container is hermetically sealed.
[0014]
It is desirable that the gas enclosed in the container is at least one of an inert gas, nitrogen, and oxygen.
[0015]
The oscillation wavelength of the semiconductor laser element may be 450 nm or less.
[0016]
The plasma irradiation is described as “before airtight sealing”, but may be performed after the semiconductor laser element or the like is installed in the container, that is, in a state where each component is installed in the container. Alternatively, it may be performed in the state of parts before installation. Furthermore, plasma irradiation may be performed in the state of the component, and plasma irradiation may be performed after the component is further installed in the container.
[0017]
【The invention's effect】
According to the first laser module manufacturing method of the present invention, at least the container and the semiconductor laser element are irradiated with plasma before the container is hermetically sealed. Therefore, hydrocarbons and silicon compounds attached to the container and the semiconductor laser element Etc., and further, contaminants present in the atmosphere in the container can be satisfactorily decomposed and removed by plasma irradiation. Therefore, it is possible to obtain a highly reliable laser module from which contaminants are well removed. In addition, since the plasma irradiation can be performed by an existing semiconductor manufacturing apparatus such as a dry etching apparatus or a plasma stripping apparatus, it is not necessary to use a new apparatus and it is possible to remove contaminants with high accuracy by a simple method. is there.
[0018]
Further, according to the second laser module manufacturing method of the present invention, as in the first laser module manufacturing method, the contaminants adhering to the container, the semiconductor laser element, the optical member, and the optical fiber can be improved with plasma. Can be removed. Since contaminants are likely to be deposited on the surface of the optical member and the input end of the optical fiber, it is effective to apply the present invention.
[0019]
In particular, in the case of a semiconductor laser element having an oscillation wavelength of 450 nm or less, the deposition rate and amount of contaminants by these short wavelength laser beams are larger than those in the case of long wavelength laser beams. Is.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
A method for manufacturing a can-type sealed laser module according to the first embodiment of the present invention will be described. FIG. 1 shows a schematic configuration diagram of the laser module. A schematic cross-sectional view of the plasma irradiation apparatus is shown in FIG.
[0022]
As shown in FIG. 1, a heat sink 4 in which a semiconductor laser element 6 is bonded to a submount 5, an electrode terminal 8 connected from the semiconductor laser element 6 by a wire 9, and an electrode terminal 11 by a wire 12. And a monitoring photodiode 10 connected to each other, which are provided with dry air (N ₂ = 80%, O ₂ = 20%) by a container 2 provided with a glass window 3 provided with a non-reflective coating. ) Ring weld sealed in an atmosphere. The internal volume of the container 2 is 67.5 mm ³ .
[0023]
Note that FIG. 1 does not describe the front half of the cylindrical container 2 in order to facilitate understanding of the component configuration in the container.
[0024]
In the laser module according to the present embodiment, laser light 7 which is forward emission light of the semiconductor laser element 6 is emitted from the window glass 3 coated with non-reflective coating, and the backward emission light of the semiconductor laser element 6 is emitted from the monitor photodiode. The amount of emitted light is sensed by 10, and the current is automatically controlled so that the output of the laser beam 7 is constant.
[0025]
Next, a method for manufacturing the laser module according to this embodiment will be described.
[0026]
On the stem 1, the heat sink 4 having the semiconductor laser element 6 bonded to the submount 5 and the photodiode 10 are fixed, connected to the electrode terminal 8 from the semiconductor laser element 6 by the wire 9, and further from the photodiode 10 to the electrode Connect to the terminal 11 with a wire 12.
[0027]
Next, plasma irradiation is performed on the stem 1 on which each component is installed. As shown in FIG. 2, the stem 1 on which each of the components is fixed is set on a fixed base 65 in the vacuum chamber 60, and exhaust 63 is performed. After evacuating from the atmosphere until the initial vacuum is 1 × 10 ⁻² Torr or less, microwave 62 and argon gas 61 of 1 × 10 ^{−2 to} 1 × 10 ⁻¹ Torr is introduced and about 10 to 1000 W is introduced. Is applied to generate plasma 64, and plasma irradiation is performed in about 60 minutes or less.
[0028]
As the gas to be introduced, pollutants composed of hydrocarbons and organosilicon compounds can be sufficiently removed even with argon alone, but a gas such as nitrogen, oxygen, hydrogen, or chlorofluorocarbon should be appropriately mixed with argon gas. However, it is more desirable in order to decompose and remove the contaminants well. For example, when it is desired to positively remove hydrocarbons, a mixed gas of oxygen and argon is preferable, and when it is desired to positively remove organic silicon compounds, a mixed gas of argon and Freon such as CF ₄ is preferable. Note that the mixing ratio of each gas in the mixed gas is preferably adjusted as appropriate in consideration of the configuration of the laser module, irradiation conditions, and the like.
[0029]
Thereafter, the stem 1 on which each component is installed is taken out from the plasma irradiation apparatus, and is placed in a dry air (N ₂ = 80%, O ₂ = 20%) atmosphere with a container 2 equipped with a window glass provided with an antireflection coating. , Ring weld sealed.
[0030]
In plasma irradiation, if the irradiation time is too long or the input power is too large, the damage by the plasma may be large. In such a case, the optical component or the like is physically or chemically etched, the surface of the optical component on the optical path is roughened, and an optical loss occurs. Such over-etching can be suppressed by adjusting the irradiation time or the input power so that the residue of etching gas such as argon physically adsorbed on the surface of the component becomes a certain amount or less.
[0031]
Next, the reliability over time of the laser module of the present invention and the conventional laser module was evaluated. FIG. 3 shows changes in the drive current of the conventional laser module over time, and FIG. 4 shows changes in the drive current of the laser module of the present invention over time. The vertical axis of the graph is a value obtained by normalizing the drive current with the initial drive current.
[0032]
As the laser module according to the present invention, the laser module according to the first embodiment, in which the oscillation wavelength of the semiconductor laser element 6 is 405 nm, is used. The configuration of the laser module of the conventional example is the same as that of the above embodiment, and plasma irradiation is not performed. Both the conventional example and the sealing atmosphere in the laser module of the present invention are dry air (N ₂ = 80%, O ₂ = 20%). The drive conditions were evaluated by adjusting the drive current so that the optical output was 30 mW at an environmental temperature of 25 ° C.
[0033]
In the laser module of the conventional example, as shown in FIG. 3, a change in driving current is seen over time, but in the laser module of the present invention, as shown in FIG. 4, no increase in driving current is seen and stable over time. doing. From this, it can be confirmed that contaminants such as hydrocarbons and silicon compounds are well removed by plasma irradiation.
[0034]
Next, a laser module according to the second embodiment of the present invention will be described. FIG. 5 shows a schematic side view and a plan view of the laser module.
[0035]
In the laser module according to the present embodiment, as shown in FIG. 5A, a base plate 42 is fixed to the bottom surface of the container 40, and seven GaN-based semiconductor laser elements LD 21 to LD 21 on the base plate 42. Heat block 20 to which LD 27 is bonded, collimator lenses 31 to 37 held by collimator lens holder 44 attached to heat block 20, condensing lens 43 held by condensing lens holder 45, and fiber holder A multimode optical fiber 30 held by 46 is fixed. An opening is formed in the wall surface of the container 40, and a wiring 47 for supplying a driving current to the GaN-based semiconductor laser elements LD21 to LD27 is drawn out of the container through the opening. The internal volume of the container 40 is about 8160 mm ³ .
[0036]
Moreover, as shown in FIG.5 (b), each of the collimator lenses 31-37 is formed in the shape which cut off the area | region containing the optical axis of the circular lens provided with the aspherical surface in the parallel plane. This elongated collimator lens can be formed, for example, by molding resin or optical glass. The collimator lenses 31 to 37 are closely arranged in the arrangement direction of the light emitting points so that the length direction is orthogonal to the arrangement direction of the light emitting points of the GaN-based semiconductor laser elements LD21 to LD27.
[0037]
In FIG. 5, in order to avoid complication of the figure. Of the plurality of GaN-based semiconductor laser elements, only the semiconductor laser elements LD21 and LD27 are denoted by reference numerals, and only the collimator lenses 31 and 37 among the plurality of collimator lenses are denoted by numerals.
[0038]
On the other hand, each of the GaN-based semiconductor laser elements LD21 to LD27 includes an active layer having a light emission width of 2 μm, and each laser has a divergence angle in a direction parallel to and perpendicular to the active layer, for example, 10 ° and 30 °, respectively. A laser that emits beams B21 to B27 is used. These semiconductor laser elements LD21 to LD27 are arranged so that the light emitting points are aligned in a direction parallel to the active layer.
[0039]
Therefore, in the laser beams B21 to B27 emitted from the respective light emitting points, the direction in which the divergence angle is large matches the length direction with respect to the elongated collimator lenses 31 to 37 as described above, and the direction in which the divergence angle is small. Is incident in a state that coincides with the width direction (direction orthogonal to the length direction). That is, each collimator lens 31 to 37 has a width of 1.1 mm and a length of 4.6 mm, and each of the laser beams B21 to B27 incident thereon has a focal length f ₁ = 3 mm, NA = 0.6, Lens arrangement pitch = 1.25 mm.
[0040]
The condensing lens 43 has a shape in which a region including the optical axis of a circular lens having an aspheric surface is cut out in a parallel plane and is long in the arrangement direction of the collimator lenses 31 to 37, that is, in the horizontal direction and short in the direction perpendicular thereto. Is formed. The condenser lens 43 has a focal length f ₂ = 12.5 mm and NA = 0.3. This condensing lens 43 is also formed by molding resin or optical glass, for example.
[0041]
The multimode optical fiber 30 may be any of a step index type optical fiber, a graded index type optical fiber, and a composite type optical fiber. For example, a graded index optical fiber manufactured by Mitsubishi Cable Industries, Ltd. can be used. This optical fiber has a graded index at the center of the core and a step index at the outer periphery, the core diameter = 25 μm, NA = 0.3, and the transmittance of the end coat = 99.5% or more.
[0042]
In the laser module according to the present embodiment, each of the laser beams B21, B22, B23, B24, B25, B26 and B27 emitted in a divergent light state from each of the GaN semiconductor laser elements LD21 to LD27 constituting the combined laser light source is Are collimated by the corresponding collimator lenses 31 to 37. The collimated laser beams B <b> 21 to B <b> 27 are collected by a condenser lens and converge on the incident end face of the multimode optical fiber 30.
[0043]
In the present embodiment, a condensing optical system is configured by the collimator lenses 31 to 37 and the condensing lens. It is combined with the beam and emitted from the multimode optical fiber.
[0044]
In the laser module, the coupling efficiency of the laser beams B21 to B27 to the multimode optical fiber is 0.9. Therefore, when the outputs of the GaN-based semiconductor laser elements LD21 to LD27 are 100 mW, a combined laser beam with an output of 630 mW (= 100 mW × 0.9 × 7) can be obtained.
[0045]
Next, a method for manufacturing the laser module according to this embodiment will be described.
[0046]
As shown in FIG. 5, a base plate 42 is fixed to the bottom surface of the container 40, and a heat block 20 in which seven GaN-based semiconductor laser elements LD <b> 21 to LD <b> 27 are bonded to the base plate 42, and the heat block 20. The collimator lenses 31 to 37 held by the collimator lens holder 44 attached to the lens, the condenser lens 43 held by the condenser lens holder 45, and the multimode optical fiber 30 held by the fiber holder 46 are fixed. To do. Next, as in the first embodiment, in the plasma irradiation apparatus shown in FIG. 2, the container 40 in which the respective components are fixed is set on the fixed base 65 in the vacuum chamber 60, and the exhaust 63 is performed. . After evacuating from the atmosphere until the initial vacuum is 1 × 10 ⁻² Torr or less, microwave 62 and argon gas 61 of 1 × 10 ^{−2 to} 1 × 10 ⁻¹ Torr is introduced and about 10 to 1000 W is introduced. Is applied to generate plasma 64, and plasma irradiation is performed in about 60 minutes or less.
[0047]
Further, in the laser module shown in FIG. 5, the degassing treatment described in Japanese Patent Application No. 2002-101714 is performed at 90 ° C. for 192 hours in order to remove an outgas component (organic gas or the like) from the adhesive, and then the present invention. In the case of performing the plasma treatment by the above method, it was possible to obtain a high reliability with time as described above.
[0048]
In the first and second laser module manufacturing methods, plasma irradiation is performed after the semiconductor laser element and other components are installed. However, these components are installed on a fixed base in the state of the components before installation. Plasma irradiation may be performed. In addition, plasma irradiation may be performed in the state of the component, and plasma irradiation may be performed after the plasma is installed in the container.
[0049]
In the laser module manufacturing method of the present invention, after plasma irradiation, argon, oxygen, or chlorofluorocarbon gas contained in the plasma atmosphere may remain in the container, but none of these can cause contamination. It does not degrade the laser characteristics.
[0050]
According to the present invention, it is possible to satisfactorily remove contaminants such as hydrocarbon compounds and silicon compounds present in a container in which a semiconductor laser element is sealed, so that a highly reliable laser module can be provided. it can.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a laser module according to a first embodiment of the present invention. FIG. 2 is a schematic sectional view showing a plasma irradiation apparatus. FIG. FIG. 4 is a graph showing a change in drive current with time in the laser module according to the first embodiment of the present invention. FIG. 5 is a schematic configuration diagram showing a laser module according to the second embodiment of the present invention. Explanation of]
DESCRIPTION OF SYMBOLS 1 Stem 2 Container 3 Window glass 4 Heat sink 5 Submount 6 Semiconductor laser element 7 Laser beam 8, 11 Electrode terminal 9, 12 Wire 10 Monitor photodiode

Claims (4)

A method for manufacturing a laser module, wherein a semiconductor laser element is installed in a container and hermetically sealed,
A method for manufacturing a laser module, comprising: irradiating at least the container and the semiconductor laser element with plasma before the container is hermetically sealed. A method of manufacturing a laser module in which a semiconductor laser element, an optical fiber, and an optical member for inputting laser light emitted from the semiconductor laser element into an optical fiber are installed in a container and hermetically sealed. And
A method for manufacturing a laser module, comprising: irradiating at least the container, the semiconductor laser element, the optical fiber, and the optical member with plasma before the container is hermetically sealed. 3. The method of manufacturing a laser module according to claim 1, wherein the gas sealed in the container is at least one of an inert gas, nitrogen, and oxygen. 4. The method of manufacturing a laser module according to claim 1, wherein an oscillation wavelength of the semiconductor laser element is 450 nm or less.

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