JP2003298171A - Laser module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-reliability laser module by efficiently suppressing deterioration of laser characteristics. <P>SOLUTION: A hermetic sealing member is provided with a sealing space which is filled with an inert gas containing oxygen in a concentration of 1 ppm or more and at least one of a halogen family gas and a halogen compound gas in its inside. Several semiconductor lasers emitting laser light in a range of wavelength of 350-450 nm, a side part combining optical fibers and a condensing optical system are hermetically sealed in the space. By containing oxygen in a concentration of 1 ppm or more in a sealing atmosphere, hydrocarbon deposits are reduced by oxidative decomposition and deposits of a silicon compound are reduced by decomposition and removal by the halogen family gas. Consequently, deterioration of laser characteristics is efficiently suppressed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser module, and more particularly to a laser module in which constituent members including a semiconductor laser having an oscillation wavelength of 350 to 450 nm are hermetically sealed.

[0002]

2. Description of the Related Art Conventionally, in an optical module that irradiates or generates ultraviolet rays having a wavelength of 400 nm or less, the optical loss of the optical components included in the optical module increases due to the radiated or generated ultraviolet rays and the characteristics of the optical components deteriorate. There was a problem of doing. It is considered that such optical loss occurs because moisture or oil (organic matter) in the atmosphere is decomposed by ultraviolet rays and the decomposed matter is deposited on the surface of the optical component.

Therefore, in the ultraviolet irradiation optical system and the like described in Japanese Patent Laid-Open No. 11-167132, the atmosphere (sealing atmosphere) in which the optical parts are placed is 99.9% or more of high purity nitrogen, 99.9. % Or more of high-purity dry air, gas with a water content of 0.1% or less, or gas with a hydrocarbon compound of 0.1% or less, etc. to prevent the accumulation of decomposition products and prevent the output of ultraviolet laser light from decreasing. ing. In addition, JP-A-11-167
Japanese Patent Publication No. 132 describes that a good deterioration preventing effect can be obtained in a system in which oxygen such as air exists.

Further, in US Pat. No. 5,392,305, oxygen is mixed in a sealing gas at a concentration of 100 ppm or more to oxidatively decompose a substance generated by decomposition of an organic substance by an ultraviolet laser beam to decompose the substance. Techniques for preventing deposition on the surface of optical components are described.

Further, in the method of extending the life of the laser resonator disclosed in Japanese Patent Laid-Open No. 11-87814, contaminants such as oil adhered to components such as a holder constituting the laser resonator are degreased with a solvent or the like. By cleaning, the long-term reliability of the laser resonator is improved.

Further, Japanese Patent Laid-Open No. 11-5482 discloses that
It is disclosed that a low-molecular-weight siloxane reacts with oxygen in a photochemical reaction by ultraviolet rays and is deposited and adhered to an optical glass window component in the form of SiOx. For this reason, it is recommended to regularly replace the "window" members that come into contact with the atmosphere.

[0007]

However, according to the research conducted by the present inventors, in a module including a semiconductor laser having an oscillation wavelength of 350 to 450 nm, if the oxygen concentration in the sealing atmosphere becomes too high, the laser characteristics are rather increased. Was found to deteriorate.

A semiconductor laser used in a laser module has its oscillation wavelength changed to 410 nm, 810 nm and 980 nm, and a laser module which has been subjected to a cleaning process described in Japanese Patent Laid-Open No. 11-87814 is used in a sealed atmosphere. When the reliability change with respect to the oxygen concentration was evaluated, in the module using the semiconductor laser with the wavelength of 410 nm, the dependency of the deterioration rate of the module over time on the oxygen concentration was determined by using the semiconductor laser with the infrared wavelength of 810 nm and 980 nm. The module was different from the conventional module, and the effect of improving the laser characteristics with the increase in oxygen concentration, which was found in the module using the semiconductor laser of infrared wavelength, was not seen.

That is, with respect to laser light of infrared wavelengths of 810 nm and 980 nm, decomposition of hydrocarbon-based organic compounds deposited on the surface of optical components existing on the laser optical path, such as the in-module fiber incident end face and lens. The reaction becomes more active as the oxygen concentration increases, and the reliability over time is improved. On the other hand, for laser light having a wavelength of 410 nm, when the oxygen concentration is 100 ppm or more, the reliability is deteriorated.

This is because the deposition of the silicon compound in the light collecting portion of the fiber end surface becomes apparent in the region where the oxygen concentration is 100 ppm or more. Like the hydrocarbon deposit, the deposit of the silicon compound also causes optical absorption, so that the reliability over time in continuous oscillation is significantly impaired.

That is, the hydrocarbon deposit produced by the reaction of the laser beam and the hydrocarbon gas is carbon dioxide (CO ₂ ) and water (H ₂ O) under a gas atmosphere containing a certain amount of oxygen or more.
It is decomposed into and removed. However, not only hydrocarbon but also silicon compound is contained in the deposit. The deposit of the silicon compound cannot be decomposed / removed only by containing oxygen in the atmosphere. The deposited silicon compound is an organic compound gas containing a silicon (silicon) atom such as a siloxane bond (Si-O-Si) or a silanol group (-Si-OH) (hereinafter referred to as "organic silicon compound gas") and a laser. It is generated by a photochemical reaction with light. Moreover, the presence of oxygen in the atmosphere accelerates the reaction rate of the photochemical reaction.

The term "silicon compound" as used herein refers to a compound having any structure containing a silicon atom, whether organic or inorganic, such as inorganic silicon oxide (SiOx), an organic silicon compound,
Silicon carbide compounds, organic silicon carbide compounds and the like are included. In addition, the organosilicon compound gas is a gas emitted from a silicone-based material used at any place during the module manufacturing process, and when it adheres to the surface of each component in the module, it seals it. When used as such, a small amount of organosilicon compound gas is contained in the sealed atmosphere.

The gas components existing in these manufacturing processes cannot be completely removed only by installing an ordinary clean room or a sealed gas purifier. To eliminate this, a large capital investment is required. Further, as described in Japanese Patent Application Laid-Open No. 11-87814, even if degreasing and cleaning of oil and the like are performed, it is inevitable that the organosilicon compound gas is mixed from the atmosphere of the manufacturing process.

Therefore, as described above, even if oxygen is contained in the sealed atmosphere in order to prevent the hydrocarbon compound from being deposited, if the oxygen content is too large, the deposition of the silicon compound increases. The laser characteristics are deteriorated and the reliability is deteriorated. Optical components such as the fiber incident end surface and the lens inside the module are fixed inside the module with an adhesive or a brazing material, and cannot be replaced as in the case described in JP-A-11-5482. .

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to effectively suppress the deterioration of the laser characteristics and provide a highly reliable laser module. It is in.

[0016]

To achieve the above object, the laser module of the present invention comprises a plurality of semiconductor lasers for emitting laser light in the wavelength range of 350 to 450 nm.
Optical fiber, and a combined laser having a condensing optical system that condenses the laser beam emitted from each of the plurality of semiconductor lasers and couples it to the optical fiber, and oxygen having a concentration of 1 ppm or more in an inert gas. A sealed space filled with a sealed gas containing at least one of a halogen group gas and a halogen compound gas is provided inside, and the semiconductor laser, the coupling side portion of the optical fiber, and the condensing optical system are provided in the sealed space. And an airtight sealing member that is airtightly sealed.

In the laser module of the present invention, the hermetic sealing member is a sealed gas containing therein oxygen of a concentration of 1 ppm or more in the inert gas and at least one gas of the halogen group gas and the halogen compound gas. A filled sealing space is provided, and a plurality of semiconductor lasers that emit laser light in the wavelength range of 350 to 450 nm, a coupling side portion of an optical fiber, and a condensing optical system are hermetically sealed in this space. . As described above, when oxygen is contained in the sealed atmosphere at a concentration of 1 ppm or more, hydrocarbon deposits are oxidatively decomposed and reduced, and silicon compound deposits are decomposed and removed by the halogen-based gas to be reduced. The deterioration of the laser characteristics is effectively suppressed. This makes it possible to provide a highly reliable laser module.

In the laser module of the present invention, the oxygen concentration in the inert gas is preferably 1 to 100 ppm. The halogen group gas and the halogen compound gas preferably contain a fluorine atom, and when the halogen compound gas is contained in the inert gas, the halogen compound gas contains carbon, nitrogen, sulfur and xenon fluorine. It is preferably at least one selected from the group consisting of a compound and chlorides of carbon, nitrogen, sulfur, and xenon.

Further, since the halogen-based gas has high reactivity, the cavity end face of the semiconductor laser to be hermetically sealed, the coupling side portion of the optical fiber, and the outermost surface layer covering the condensing optical system are provided with the halogen group gas and the halogen gas. It is preferable to use a material that is inert to the compound gas. The inert material is
For example, it can be selected from the group consisting of oxides of indium, gallium, aluminum, titanium, and tantalum and nitrides of gallium, aluminum, titanium, and tantalum.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Module Configuration] The laser module according to the present embodiment includes the combined laser light source shown in FIG. This combined laser light source is composed of a plurality (for example, 7) of chip-shaped lateral multimode GaN-based semiconductor lasers LD1, LD2, LD3, LD arranged and fixed on a heat block 10.
4, LD5, LD6, and LD7, and collimator lenses 11, 12, 13, 14, 15, 16, and 17 provided corresponding to the GaN-based semiconductor lasers LD1 to LD7, respectively, and one condenser lens 20. And one multimode optical fiber 30.

The GaN semiconductor lasers LD1 to LD7 are
The oscillation wavelengths are all common (for example, 405 nm), and the maximum outputs are also all common (for example, 100 mW). The GaN semiconductor lasers LD1 to LD7 are 3
405 nm above in the wavelength range of 50 nm to 450 nm
Lasers having oscillation wavelengths other than can be used.

As shown in FIGS. 2 and 3, the above-mentioned combined laser light source is housed together with other optical elements in a box-shaped package 40 having an upper opening. Package 40
A base plate 42 is fixed to the bottom surface of the base plate 42. On the upper surface of the base plate 42, the heat block 10, a condenser lens holder 45 for holding the condenser lens 20, and an incident end portion of the multimode optical fiber 30. And a fiber holder 46 for holding Further, a collimator lens holder 44 is provided on the side surface of the heat block 10.
Is attached, and the collimator lenses 11 to 17 are held. An opening is formed in the lateral wall surface of the package 40, and the GaN semiconductor laser LD1 is formed through this opening.
A wiring 47 for supplying a drive current to the LD 7 is drawn out of the package.

In FIG. 2, only the GaN-based semiconductor laser LD7 of the plurality of GaN-based semiconductor lasers is numbered and only the collimator lens 17 of the plurality of collimator lenses is shown in order to avoid complication of the drawing. Numbered.

FIG. 4 shows the collimator lenses 11-17.
2 shows the front shape of the attachment part of FIG. Each of the collimator lenses 11 to 17 is formed in a shape in which a region including the optical axis of a circular lens having an aspherical surface is elongated and cut out in parallel planes. The elongated collimator lens can be formed by molding resin or optical glass, for example. Collimator lens 1
1 to 17 are GaN-based semiconductor lasers LD1 to LD1 in the length direction.
The LD 7 is closely arranged in the arrangement direction of the light emitting points so as to be orthogonal to the arrangement direction of the light emitting points of the LD 7 (left and right direction in FIG. 4).

On the other hand, GaN semiconductor lasers LD1 to LD
7 includes an active layer having an emission width of 2 μm, and the divergence angle in the direction parallel to the active layer and the divergence angle in the direction perpendicular to the active layer are, for example, 10
Lasers which emit laser beams B1 to B7 in the respective states of 30 ° and 30 ° are used. These GaN-based semiconductor lasers LD1 to LD7 have an emission point of 1 in the direction parallel to the active layer.
It is arranged so as to line up in a row.

Therefore, the laser beams B1 to B7 emitted from the respective light emitting points diverge with respect to the elongated collimator lenses 11 to 17 in the direction in which the divergence angle is large coincide with the length direction. The light enters in a state in which the direction with a small angle coincides with the width direction (direction orthogonal to the length direction). That is, each collimator lens 11 to 17 has a width of 1.1 mm and a length of 4.6 mm, and the laser beams B1 to B7 incident on them have horizontal and vertical beam diameters of 0.9 mm and 2. It is 6 mm. Also,
Each of the collimator lenses 11 to 17 has a focal length f ₁ =
3 mm, NA = 0.6, lens arrangement pitch = 1.25 m
m.

In the condenser lens 20, a region including the optical axis of a circular lens having an aspherical surface is cut into long and slender parts in parallel planes, and the collimator lenses 11 to 17 are arranged in a long direction, that is, in a horizontal direction and at a right angle thereto. It has a short shape. This condenser lens 20 has a focal length f ₂ = 12.
5 mm and NA = 0.3. This condenser lens 20 also
For example, it is formed by molding resin or optical glass.

The multimode optical fiber 30 may be any one of a step index type optical fiber, a graded index type optical fiber and a composite type optical fiber.
For example, a graded index type optical fiber manufactured by Mitsubishi Cable Industries, Ltd. can be used. In this optical fiber, the central part of the core has a graded index and the outer peripheral part has a step index, the core diameter = 25 μm,
NA = 0.3, transmittance of end face coat = 99.5% or more.

The package 40 is provided with a package lid 41 formed so as to close the opening thereof. By introducing a sealing gas after the degassing process described later and closing the opening of the package 40 with the package lid 41, Package 4
The combined laser light source is hermetically sealed together with other optical elements in a closed space (sealing space) formed by 0 and the package lid 41.

Here, in order to suppress the deterioration of the module, oxygen and a halogen group gas or a halogen compound gas (hereinafter referred to as "halogen-based gas") having a concentration of 1 ppm or more in the inert gas is used in the sealed space. It is hermetically sealed so as to be filled with a filling gas containing and. To this end, a gas containing oxygen and a halogen-based gas having a concentration of 1 ppm or more is filled in an inert gas to carry out hermetic sealing.

The inert gas is a gas inert to the optical elements contained in the sealed atmosphere, and for example, a rare gas such as dry nitrogen or argon can be used.

When the sealed atmosphere contains oxygen at a concentration of 1 ppm or more, deterioration of the laser module can be suppressed. The reason why such a deterioration suppressing effect is obtained is that oxygen contained in the sealed atmosphere oxidatively decomposes the solid matter generated by the photolysis of the hydrocarbon component. On the other hand, if the oxygen concentration is less than 1 ppm, the deterioration suppressing effect cannot be obtained. If the oxygen concentration is too high, the photochemical reaction of the organosilicon compound gas is rather promoted. Therefore, the oxygen concentration in the sealed atmosphere is preferably in the range of 1 to 800 ppm,
The range of 100 ppm is particularly preferred.

The halogen group gas is chlorine gas (C
l ₂ ), fluorine gas (F ₂ ) and the like, and the halogen compound gas means a halogen atom such as chlorine atom (Cl), bromine atom (Br), iodine atom (I), fluorine atom (F), etc. It is a gaseous compound containing.

As the halogen compound gas, CF ₃ C is used.
1, CF ₂ Cl ₂ , CFCl ₃ , CF ₃ Br, CCl ₄ , C
_{Cl 4 -O 2, C 2 F} 4 Cl 2, Cl-H 2, CF 3 Br, P
Cl ₃ , CF ₄ , SF ₆ , NF ₃ , XeF ₂ , C ₃ F ₈ , CH
F _{3 and the} like can be mentioned, but fluorine or chlorine and carbon (C),
Compounds with nitrogen (N), sulfur (S) and xenon (Xe) are preferable, and compounds containing a fluorine atom are particularly preferable.

The halogen-based gas exerts the deterioration suppressing effect from a very small amount, but in order to obtain the remarkable deterioration suppressing effect, the content concentration of the halogen-based gas is preferably 1 ppm or more. The reason why such a deterioration suppressing effect is obtained is that the halogen-based gas contained in the sealing atmosphere decomposes the deposit generated by the photolysis of the organosilicon compound gas.

As the material of the outermost surface layer for coating the optical parts, halogen-based materials such as oxides or nitrides of silicon (Si), molybdenum (Mo), chromium (Cr), tin (Sn) or zirconium (Zr) are used. If a material reactive with gas is used, the outermost surface layers of these optical components are etched, which reduces the reliability of the module.

Therefore, the cavity of the GaN semiconductor laser,
Exposing the components of the combined laser light source such as the collimator lens, the condenser lens, and the incident side end of the multimode optical fiber, and the optical atmosphere that is hermetically sealed together with the combined laser light source such as the optical mirror. The outermost surface layer to be formed is, for example, indium (In), gallium (Ga), aluminum (Al), titanium (Ti), or tantalum (Ta).
It is preferable to use a material which is inert to a halogen-based gas, such as the oxide or the nitride.

Before carrying out the hermetic sealing by sealing the sealing gas, a degassing process for exhausting the atmosphere in the sealing space is performed.
From the viewpoint of not impairing the mechanical properties of the adhesive, it is usually 200 ° C.
This degassing process is performed below. Even if an organic adhesive is used to fix the optical system in the module, degassing treatment is performed after fixing each component with the adhesive and before sealing, thereby suppressing outgas from the organic adhesive. can do. By setting the amount of organic adhesive used for fixing optical parts to 1.0 g / ml or less, the saturation concentration of the outgas component in the module during degassing is 1000 ppm.
Can be less than.

[Module Operation] Next, the operation of the laser module will be described.

Each of the laser beams B1, B2, B3, B4, B5, B6, and B7 emitted in a diverging state from each of the GaN-based semiconductor lasers LD1 to LD7 constituting the combined laser light source, corresponds to a corresponding collimator lens. 11-17
Is collimated by. The parallel laser beams B1 to B7 are condensed by the condenser lens 20 and converged on the incident end face of the core 30a of the multimode optical fiber 30.

In this example, the collimator lenses 11 to 17 and the condenser lens 20 constitute a condenser optical system, and the condenser optical system and the multimode optical fiber 30 constitute a multiplexing optical system. That is, the laser beams B1 to B7 condensed by the condenser lens 20 as described above.
Of the multi-mode optical fiber 30 enters the core 30 a of the multi-mode optical fiber 30, propagates in the optical fiber, is combined into one laser beam B, and is emitted from the multi-mode optical fiber 30.

In the above laser module, the coupling efficiency of the laser beams B1 to B7 to the multimode optical fiber 30 is 0.9. Therefore, the GaN semiconductor laser LD
When each output of 1 to LD7 is 100 mW, output 63
A combined laser beam B of 0 mW (= 100 mW × 0.9 × 7) can be obtained.

[0043]

Next, the present invention will be described in more detail based on specific examples.

Using the laser module having the configuration shown in FIGS. 1 to 4, under the four conditions (levels) shown in Table 1 below, the oxygen concentration and the halogen-based gas concentration in the sealed atmosphere and the deterioration rate of the module are shown. I investigated the relationship. Results are shown in FIG.

[0045]

[Table 1]

The deterioration rate k of the module is represented by the amount of drive current increase per hour required to drive all the elements when the APC drive is performed so that each light emitting point of the laser module outputs 30 mW. . Nitrogen gas was used as the inert gas and carbon tetrafluoride (CF ₄ ) was used as the halogen-based gas in the sealed atmosphere. The hydrocarbon concentration in the sealed atmosphere is about 100 ppm.

As can be seen from FIG. 5, at the level (1),
For low concentration (0.1ppm) oxygen atmosphere in the module
From the hydrocarbon gas present in high concentration in the atmosphere
The decomposition of hydrocarbon deposits is not complete. Elapsed time and
Light loss due to increasing hydrocarbon deposits in both cases
Occurs predominantly, which leads to a high module deterioration rate.
Yes. Naturally CF_FourDependence of deterioration rate on concentration
Absent. Oxygen gas is used in the decomposition of hydrocarbon gas.
Since most of the gas is used, the acceleration of deposition of organosilicon compound gas
Is not deposited and the organosilicon compound gas is not deposited.
It That is, CF _FourEven if the concentration of
The surface of the optical component is covered with a hydrocarbon compound.
And CF seen under the conditions described below_FourOf optical components by gas
No deterioration due to etching phenomenon is observed.

In Level (2), Level (3), and Level (4), the remarkable deterioration suppressing effect is exhibited by introducing CF ₄ into the module. As the oxygen concentration increases, the amount of silicon oxide compound produced also increases.
When the oxygen concentration is high as in level (2), the effect of introducing CF ₄ gas is small. The effect of introducing CF ₄ gas is more remarkable when the oxygen concentration is low. In addition, CF is used as the outermost surface layer.
_When SiO ₂ having reactivity with ₄ is used, SiO ₂ forming the outermost surface layer of the optical component reacts with CF ₄ to start vaporization at a certain concentration of CF ₄ or more regardless of the oxygen concentration. , The optical components and the end face of the fiber are significantly deteriorated, and the deterioration speed is rapidly increased.

As can be seen from the above results, 1 p
If a CF ₄ gas (halogen-based gas) is introduced into the sealing atmosphere containing a concentration of pm or more, a remarkable deterioration suppressing effect can be obtained.

As described above, in the laser module of the present embodiment, hydrocarbon is contained by hermetically sealing by containing oxygen at a concentration of 1 ppm or more and an inert gas containing a halogen-based gas. Not only the deposits but also the deposits of silicon compounds are decomposed and removed to be reduced, and the deterioration of the module is significantly suppressed. That is, the reliability of the laser module is improved and high output can be maintained for a long time.

[0051]

According to the present invention, it is possible to effectively suppress the deterioration of laser characteristics and provide a highly reliable laser module.

[Brief description of drawings]

FIG. 1 is a plan view showing a configuration of a combined laser light source of a laser module according to an embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of a laser module according to an embodiment of the present invention.

FIG. 3 is a side view showing the configuration of the laser module shown in FIG.

FIG. 4 is a partial side view showing the configuration of the laser module shown in FIG.

FIG. 5 is a graph showing the relationship between the oxygen concentration and the halogen-based gas concentration in the sealed atmosphere and the deterioration rate of the module at each level.

[Explanation of symbols]

10 heat block 11-17 Collimator lens 20 Condensing lens 30 multimode optical fiber 30a core 40 packages 41 package lid LD1 to LD7 GaN semiconductor laser

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuhiko Nagano             798 Miyadai, Kaisei-cho, Ashigarakami-gun, Kanagawa Prefecture             Shishi Film Co., Ltd. (72) Inventor Teruhiko Kuramachi             798 Miyadai, Kaisei-cho, Ashigarakami-gun, Kanagawa Prefecture             Shishi Film Co., Ltd. F-term (reference) 2H037 BA03 BA32 CA13 CA16 DA03                       DA04 DA05 DA36 DA38                 5F073 AA84 AB15 AB27 AB28 CA07                       CB20 FA07 FA08 FA29

Claims (6)

[Claims] 1. A plurality of semiconductor lasers for emitting laser light in a wavelength range of 350 to 450 nm, one optical fiber,
And a multiplexing laser having a condensing optical system for condensing a laser beam emitted from each of the plurality of semiconductor lasers and coupling it to the optical fiber; oxygen and a halogen gas having a concentration of 1 ppm or more in an inert gas; A sealed space filled with a sealed gas containing at least one gas of a halogen compound gas is provided inside, and the semiconductor laser, the coupling side part of the optical fiber, and the condensing optical system are hermetically sealed in the sealed space. A laser module including: 2. The oxygen concentration in the inert gas is set to 1 to 100.
The laser module according to claim 1, wherein the ppm is set. 3. The laser module according to claim 1, wherein the halogen group gas and the halogen compound gas contain a fluorine atom. 4. The halogen compound gas is carbon, nitrogen,
4. The laser module according to claim 1, wherein the laser module is at least one selected from the group consisting of fluorides of sulfur and xenon and chlorides of carbon, nitrogen, sulfur, and xenon. 5. The resonator end face of the semiconductor laser, the coupling side portion of the optical fiber, and the outermost surface layer covering the condensing optical system are made of a material inert to the halogen group gas and the halogen compound gas. The laser module according to any one of claims 1 to 4, 6. The inert material is at least one selected from the group consisting of oxides of indium, gallium, aluminum, titanium and tantalum and nitrides of gallium, aluminum, titanium and tantalum. The laser module according to claim 5, which is present.