JP2011210841A - Laser oscillator and method of assembling laser oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a laser output decrease to equal to or less than 1% by suppressing a positional deviation after adjustment during precise fixation of an optical element by soldering with respect to a laser oscillator having the optical element positioned and fixed tightly using solder.SOLUTION: When the optical element constituting the laser oscillator is precisely fixed on an optical plane base via a solder layer, a metallic holding member for the optical element comprises an upper holding member and a lower holding member each made of material having a small coefficient of linear expansion, and the solder layer is provided between the upper holding member and lower holding member, wherein the metallic holding member of a part which supports the optical element and includes the metallic holding member and includes the solder layer, has a height h equal to or less than a predetermined value, in a direction perpendicular to an optical axis of the laser oscillator.

Description

  The present invention relates to a laser oscillator formed from optical parts that are precisely positioned and firmly fixed, and an assembling method thereof.

  In a conventional laser oscillator, an optical element such as a mirror is precisely fixed on a glass flat support plate using an ultraviolet curing adhesive. With such a configuration, the assembly of the oscillator is facilitated, the adjustment mechanism of the optical element is eliminated, the cost is reduced and the size is reduced, and the optical flat base is configured with a glass material having a low coefficient of thermal expansion. Thus, stable laser oscillation is realized (for example, see Patent Document 1).

As another conventional technique, in the configuration in which the output of the semiconductor laser is coupled to the optical fiber, a solder layer is provided on the holding base of the optical fiber in order to accurately position and fix the optical fiber. With such a configuration, a more reliable and robust holding can be realized than using an ultraviolet curable adhesive. If this technology is applied to a laser oscillator, highly reliable and highly stable operation can be realized (see, for example, Patent Document 2).

JP-A-5-152649 US Pat. No. 5,930,600

  In the laser oscillator as in Patent Document 1, each optical element is generally positioned and fixed via a thick UV-curing adhesive layer of 10 to 100 microns or more. In general, a laser oscillator is used in a state where an airtight space is maintained for dust prevention and humidity control. However, if a considerable amount of adhesive is used in the oscillator, outgassing from the adhesive layer may occur, resulting in a loss in laser oscillation operation. is there. Moreover, the adhesive layer that is a resin may deteriorate over time, resulting in a decrease in adhesive force and a change in shape. In addition, the glass base is more expensive than a metal material such as aluminum, and has a problem that the mass is large, the workability is poor, and the freedom of design is limited.

  Further, in the laser oscillator to which the technique as disclosed in Patent Document 2 is applied, a solder layer is provided on the metal holding member of each optical element constituting the laser oscillator, and the PTC or NTC thermistor for controlling the solder temperature is made of the above metal. It is configured to be integrated into the holding member. For this reason, during the positioning adjustment of the optical element, the metal holding member rises to a temperature equal to or higher than the solder melting point, and the metal holding member contracts with the cooling of the metal holding member after positioning and fixing, so that the optical element There was a problem that a positional shift occurred. Furthermore, the number of parts of the metal holding member of each optical element is large, the configuration is complicated, and there are problems in terms of assembly and cost.

  The present invention has been made to solve the above-described problems, and in a laser oscillator having an adjustment mechanism related to installation of an optical element, the optical element is precisely fixed by solder that enables highly reliable joining. In this case, an assembly method capable of suppressing the output drop of the laser oscillator after the adjustment by suppressing the influence of the positional deviation at the time of adjustment is provided, and the optical element is precisely fixed with an inexpensive configuration with a small number of parts. The purpose is to obtain a realized laser oscillator.

  A laser oscillator according to the present invention is a laser oscillator having a laser medium and a plurality of optical elements disposed on an optical plane base, and a metal holding member that supports the optical elements on the optical plane base. The metal holding member includes an upper holding member and a lower holding member that are divided into two in the vertical direction. A solder layer is provided between the upper holding member and the lower holding member, and the metal including the solder layer. The height h of the portion supporting the optical element including the made holding member in the direction perpendicular to the optical axis of the laser oscillator of the metal holding member is set to a predetermined value or less.

On the other hand, a laser oscillator assembly method according to the present invention includes a laser medium having a laser medium disposed on an optical plane base, a plurality of optical elements, and a metal holding member that supports the optical elements on the optical plane base. In the oscillator,
The metal holding member is composed of an upper holding member and a lower holding member that are divided into two vertically, and a solder layer is provided between the upper holding member and the lower holding member, and the metal holding member including the solder layer is provided. On the optical axis of the laser oscillator, the height h from the surface of the optical plane base in the direction perpendicular to the optical axis of the laser oscillator of the part supporting the optical element including the member is not more than a predetermined value, When a plurality of optical elements are precisely fixed, a plurality of precision fixing operations are simultaneously performed.

  According to the present invention, in a laser oscillator that firmly positions and fixes an optical element using solder, by limiting the height of the metal holding member of the optical element, the laser oscillation after precise fixing from the time of adjusting the optical element It is possible to suppress a decrease in output within 1%. In addition, by providing a constant temperature optical flat base, it is possible to realize a laser oscillator assembly method in which a plurality of optical elements included in a laser oscillator in the same oscillator casing are firmly positioned and fixed simultaneously using solder.

1 is an overall configuration diagram showing a laser oscillator according to a first embodiment of the present invention. It is a perspective view which shows the optical element holding | maintenance part by Embodiment 1 of this invention. 4 is a graph showing the relationship between the amount of lens position shift and the laser oscillator output reduction in Embodiment 1 of the present invention. It is a perspective view which shows the optical element holding | maintenance part by Embodiment 2 of this invention. It is a perspective view which shows the optical element holding | maintenance part by Embodiment 3 of this invention. It is a perspective view which shows the optical element holding | maintenance part by Embodiment 4 of this invention. It is a whole block diagram which shows the laser oscillator by Embodiment 5 of this invention. It is a block diagram in the optical element precision fixing operation | work by Embodiment 5 of this invention. It is a block diagram during the laser oscillator assembly adjustment by Embodiment 5 of this invention.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a laser oscillator according to the first embodiment of the present invention. On the optical flat base 2, the laser medium 5 constituting the laser oscillator 1, the acousto-optic Q switch element 7, the resonator mirrors 3a and 3b, the pumping light transmission lenses 4a and 4b, the mode limiting aperture 6, and the pumping light transmission. The fiber connector 17 of the fiber 8 and the oscillation laser light transmission lenses 25a and 25b are fixed. The pumping light is a laser oscillator having an end face pumping configuration in which the pumping light is introduced from the semiconductor laser package 9 into the laser medium 5 through the pumping light transmission fiber 8 with the pumping light transmission lenses 4a and 4b adjusting the pumping light propagation diameter. As the laser medium 5, a solid medium such as Nd: YVO ₄ or Nd: YAG is used. The laser medium 5 and the acousto-optic Q switch element 7 are positioned with mechanical accuracy and fixed to the optical flat base 2. The other resonator mirror 3, the pumping light transmission lens 4, the mode limiting aperture 6, the fiber connector 17 that holds the fiber end, and the metal holding member of the oscillation laser light transmission lens 25 are divided into two parts and include a low melting point solder layer. It has a configuration.

The laser oscillator according to the first embodiment of the present invention has one or more optical elements constituting a Fabry-Perot resonator, and the optical elements are, for example, resonator mirrors and lenses. On the optical flat base of the oscillator housing, it is supported by a metal holding member having a low linear expansion coefficient, for example, a metal holding member made of martensitic stainless steel. The metal holding member is divided into two in the vertical direction, and includes a low melting point solder layer therebetween. The metal holding member is provided with one hole for inserting a heater. The said structure WHEREIN: The height of the metal holding member containing the said low melting-point solder layer shall be 30 mm or less which is a predetermined value, It is characterized by the above-mentioned. Further, when fixing a convex lens having a focal length of 80 mm or less or a concave mirror having a curvature of 160 mm or less, the height of the metal holding member including the low melting point solder layer is set to 15 mm or less which is ½ of a predetermined value. It is characterized by. Alternatively, in order to realize the above height value, a heat sink is provided between the optical flat base at the position where the optical element is installed and the metal holding member. Furthermore, a constant temperature mechanism for making the optical plane base temperature constant during the optical element positioning adjustment is provided.

  FIG. 2 shows an example of an enlarged view of the optical element holding portion including the solder layer. Here, examples of mirrors and lenses installed in the resonator are shown. The optical element 3 is bonded to the member of the upper holding member 10 with a thin epoxy adhesive layer 12 of micron order or less. The epoxy used is a thermosetting adhesive such as Cemedine EP160.

On the other hand, the member of the lower holding member 11 is fastened and fixed to the optical flat base 2 by bolts 21. Both the upper holding member 10 and the lower holding member 11 are made of, for example, martensitic stainless steel SUS440, which has a linear expansion coefficient that is about 1/2 that of a general austenitic stainless steel SUS304.

Further, both the upper and lower metal members used for holding the optical element are plated with nickel, gold, or the like to ensure solder wettability and corrosion resistance. A low melting point solder layer 13 is provided between both members. As the solder to be used, for example, a low melting point solder having a melting temperature of about 140 ° C. of Sn—Bi eutectic alloy is applied.

The lower holding member 11 is provided with a hole for inserting a cartridge heater, and the diameter of the hole is manufactured based on a clearance fit tolerance with respect to the diameter of the cartridge heater to be inserted at the time of manufacture.

Furthermore, the upper holding member 10 and the lower holding member 11 are in contact with each other via solder on a surface inclined by about 20 ° with respect to the surface of the optical flat base 2. The cartridge heater insertion hole may be provided in the upper holding member 10. Here, the combined height of the upper holding member 10 and the lower holding member 11 (value h in FIG. 2) is 30 mm or less.

  According to such a configuration, the upper holding member 10 and the lower holding member 11 including the low melting point solder layer 13 can be constituted by two inexpensive metal members. The surfaces of the upper holding member 10 and the lower holding member 11 have solder wettability ensured by plating. Further, since the upper holding member 10 and the lower holding member 11 are in contact with each other at a surface inclined with respect to the surface of the optical flat base 2, the opposing surfaces of the upper holding member 10 and the lower holding member 11 are shifted in the inclination direction. This makes it possible to adjust the height direction of the optical element equal to or greater than the thickness of the solder layer.

The epoxy 12 for bonding the optical element 3 to the upper holding member 10 is thermosetting and can secure a necessary adhesive force even in a high temperature state during adjustment. Further, the epoxy adhesive layer 12 has a thickness of less than a micron order and is used in a very small amount, and it has been found that the influence of outgas and deformation is negligible according to previous evaluations. Although the solder applied to the solder layer 13 has a low melting point, the temperature of the upper holding member 10 and the lower holding member 11 in contact with the solder layer is increased by about 120 ° C. on average during the optical element positioning adjustment. Therefore, in the process of cooling after positioning and returning to room temperature, the upper holding member 10 and the lower holding member 11 contract, and the position of the optical element deviates from the optimum position.

FIG. 3 shows the relationship between the positional deviation of the optical element and the laser oscillation output in a general single mode oscillator. As shown in FIG. 3, in a convex lens with a focal length of 80 mm or more, it is possible to suppress a decrease in laser oscillation output within 1% by suppressing the positional deviation to 40 microns or less. The linear expansion coefficient of the upper holding member 10 and the lower holding member 11 is 10.2 × 10 ⁻⁶ / ° C. When assuming a temperature change of 120 ° C., the total height of the upper holding member 10 and the lower holding member 11 is 30 mm. Within the range, the positional deviation can be suppressed to 40 microns or less. This positional deviation amount could be confirmed by the actual test. It has been confirmed that the same result is obtained when the upper holding member and the lower holding member are made of a material having a linear expansion coefficient of 12.0 × 10 ⁻⁶ / ° C. or less.

A lens used in a single mode oscillator can generally be configured with a focal length of 80 mm or more. Therefore, if the above range can be realized, a normal oscillator design can be supported. Also, when aiming to reduce the size of the laser oscillator, a special configuration that fixes a convex lens with a focal length of 80 mm or less, or a concave mirror with a curvature of 160 mm or less that has a function equivalent to that of the lens, a position of 20 microns or less from FIG. If the deviation is suppressed, a decrease in laser oscillation output can be similarly suppressed to within 1%. In order to achieve a positional shift amount of 20 microns or less, it is necessary to design the total height of the upper holding member 10 and the lower holding member 11 to be 15 mm or less, which is 1/2 of a predetermined value. By designing in this range, this configuration can be adopted for any lens that can be applied in the laser oscillator.

  In addition to the optical element 3 as shown in FIG. 2, other excitation light transmission lens 4 and oscillation light transmission lens 25 disposed on the laser optical axis in the laser oscillator 1, and a metal mode limiting aperture 6, The same effect can be obtained for the metal fiber connector mounting plate 18 to which the fiber connector 17 is attached by configuring a holding member made of a metal member having a low linear expansion coefficient including a solder layer.

If the element placed on the laser optical axis is made of a metal (aluminum or stainless steel) such as the mode limiting aperture 6 or the fiber connector mounting plate 18, a plating process capable of ensuring solder wettability such as nickel and gold is applied. In addition, it is possible to provide a structure having a joint surface directly with the solder layer, and further reduce the number of parts.

  By adopting the configuration shown in the first embodiment, it is not necessary to integrate a conventional PTC or NTC thermistor into the optical element base, so that the solder precision fixing optical element having a small number of parts and an easily assembled structure can be obtained. The base can be realized. Further, by constructing a laser oscillator by holding this optical element, a laser oscillator that is inexpensive, robust, compact, stable operation and good in assemblability can be realized.

Embodiment 2. FIG.
Another example of the optical element holding unit is shown in FIG. A heat sink 27 is provided under the lower holding member 11. The heat sink 27 is, for example, directly water-cooled, and the temperature rise is suppressed to 5 ° C. or less during the position adjustment of the optical element 3. By adopting such a configuration, the optical element is desired in a state in which the height h of the metal holding member is not increased and the decrease in the output of the laser oscillator due to the positional deviation from the optical element positioning adjustment is suppressed to within 1%. It is possible to arrange at the height.

Embodiment 3 FIG.
FIG. 5 shows another example of the optical element holding structure. In this example, nickel, gold, or the like is deposited on the side surface of the optical glass mirror. Thus, solder wettability may be secured directly on the side surface of the optical element.

  According to this configuration, the upper holding member 10 and the lower holding member 11 shown in FIG. 2 can be integrated, and the number of parts can be reduced. Therefore, the height of the optical axis of the oscillator can be further reduced, and the laser oscillator 1 Can be miniaturized. Moreover, an epoxy adhesive layer can be eliminated and reliability can be improved.

Embodiment 4 FIG.
Furthermore, another example of the optical element holding structure is shown in FIG. In this example, the optical glass mirror 3 is sandwiched and held by an optical element sandwiching holder 26 which has been plated to ensure solder wettability. The optical element sandwiching and holding holder 26 is configured to hold the optical element by directly contacting the lower holding member 11 through the solder layer.

  According to this configuration, the epoxy adhesive for bonding the optical element and the upper holding member shown in FIG. 2 becomes unnecessary, and the reliability can be further improved.

Embodiment 5 FIG.
An operation procedure for precisely fixing an optical element, an aperture, a fiber connector fixing plate and the like arranged on the optical axis in a laser oscillator will be described. A commercially available cartridge heater 14 is inserted into a hole provided in the lower holding member 11 as shown in FIG.
The outer diameter of the cartridge heater 14 and the inner diameter of the optical element base 11 are manufactured on the basis of a clearance fit tolerance, and can be removed and attached as necessary, and efficient heat transfer can be realized. The cartridge heater is connected to a temperature controller 16 that also serves as a heater power source.

On the other hand, a thermocouple is attached to the lower holding member 11 and connected to the temperature controller 16. While maintaining the temperature of the opposing surfaces of the upper holding member 10 and the lower holding member 11 in contact with the solder layer 13 at about 150 ° C., which slightly exceeds the melting point of the solder, the optical element 3 is separately held by the position adjusting jig 24 for positioning. Do. If the position is determined, the solder layer temperature is lowered while the position is completely fixed by the jig 24 to cure the solder layer 13. Thereafter, the adjusting jig 24 and the cartridge heater 14 for gripping the optical element 3 are removed, and the optical element precision fixing is completed.

  When actually manufacturing and adjusting a laser oscillator, it is necessary to adjust a plurality of optical elements simultaneously. As shown in FIG. 9, here, the two pumping light transmission lenses 4 a and 4 b and the two resonator mirrors 3 a and 3 b are simultaneously inserted into the respective lower holding members 11, and the position adjusting jig 24 is inserted. The state which is adjusting the optical element hold | gripped by is shown. In order to adjust the position of a plurality of elements at the same time, the optical flat base must not be distorted. When the optical flat base does not have a sufficient heat capacity and the temperature of the base is expected to change during heating of the heater during element adjustment, an optical flat base 28 having a constant temperature function is applied as shown in FIG. As an example, temperature control is performed by directly cooling the base with water. With this configuration, a plurality of elements can be precisely fixed at the same time without causing mutual positional deviation so as to suppress the laser oscillation output decrease during adjustment to within 1%.

  Further, since the cartridge heater can be used repeatedly, the manufacturing cost of the laser oscillator can be reduced. The number of parts is small, assembly is easy, and simultaneous adjustment of optical elements at a plurality of locations can be easily performed.

  DESCRIPTION OF SYMBOLS 1 Laser oscillator, 2 Optical plane base, 3 Optical element, 4 Excitation light transmission lens, 5 Laser medium, 6 Mode restriction | limiting aperture, 7 Acoustooptic Q switch, 8 Excitation light transmission optical fiber, 9 Semiconductor laser package, 10 Upper holding Member, 11 Lower holding member, 12 Epoxy adhesive, 13 Solder, 14 Cartridge heater, 15 Thermocouple, 16 Temperature controller, 17 Fiber connector, 18 Fiber connector mounting plate, 19 Thermocouple integrated cartridge heater, 20 Cartridge heater insertion Hole, 21 Fixing bolt, 22 Side metal deposition mirror, 23 Heater feed line, 24 Position adjustment jig, 25 Laser oscillation light transmission lens, 26 Optical element pinching holder, 27 Heat sink, 28 Constant temperature optical flat base.

Claims (10)

In a laser oscillator having a laser medium and a plurality of optical elements arranged on an optical plane base, and a metal holding member that supports the optical elements on the optical plane base,
The metal holding member includes an upper holding member and a lower holding member that are divided into two in the vertical direction. A solder layer is provided between the upper holding member and the lower holding member, and the metal including the solder layer. A laser oscillator characterized in that a height h of a portion supporting the optical element including a made holding member in a direction perpendicular to the optical axis of the laser oscillator of the metallic holding member is equal to or less than a predetermined value. The laser oscillator according to claim 1, wherein a height h of the metal holding member in a direction perpendicular to the optical axis of the laser oscillator is set to ½ or less of a predetermined value. 3. The laser oscillator according to claim 1, wherein a heat sink is inserted between a metal holding member and the optical flat base. 3. The laser oscillator according to claim 1, wherein the metal holding member is made of a material having a linear expansion coefficient of 12.0 × 10 ⁻⁶ / ° C. or less. 3. The laser oscillator according to claim 1, wherein a hole for inserting a cartridge heater is provided in the metal holding member. 3. The laser oscillator according to claim 1, wherein a constant temperature mechanism is provided on the optical flat base. The metal element is vapor-deposited on the side surface of the optical element, and the optical element is directly bonded and fixed to the lower holding member fixed on the optical flat base via a solder layer. Or the laser oscillator of 2. An optical element is mechanically sandwiched and fixed by an optical element sandwiching holding holder, and the optical element sandwiching holding holder is bonded and fixed to the lower holding member fixed on the optical flat base via the solder layer. The laser oscillator according to claim 1 or 2, wherein In a laser oscillator having a laser medium and a plurality of optical elements arranged on an optical plane base, and a metal holding member that supports the optical elements on the optical plane base,
The metal holding member is composed of an upper holding member and a lower holding member that are divided into two vertically, and a solder layer is provided between the upper holding member and the lower holding member, and the metal holding member including the solder layer is provided. On the optical axis of the laser oscillator, the height h from the surface of the optical plane base in the direction perpendicular to the optical axis of the laser oscillator of the part supporting the optical element including the member is not more than a predetermined value, A method for assembling a laser oscillator, wherein when a plurality of optical elements are precisely fixed, a plurality of precision fixing operations are simultaneously performed. 10. The laser oscillator assembling method according to claim 9, wherein the optical flat base is provided with a constant temperature mechanism.

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