JP4638697B2 - Wavelength conversion crystal unit - Google Patents

Description

  The present invention relates to a technique for generating a harmonic laser beam, and more particularly, to a wavelength conversion crystal unit used for generating a harmonic light beam.

In recent years, lasers are used in the manufacturing industry, particularly in the fields of welding, cutting and surface treatment. In fact, laser welding technology is becoming more and more important because it can realize high-precision and high-speed machining, low thermal strain on the workpiece, and high degree of automation. At present, the solid-state laser most frequently used for laser welding is a YAG laser that generates laser light having a wavelength of about 1 μm. The YAG laser is a YAG (Y ₃ Al ₅ O ₁₂ ) crystal doped with rare earth active ions (Nd ³⁺ , Yb ^3+, etc.) as a base material. The fundamental wavelength of a typical Nd: YAG laser is 1064 nm. is there. The YAG laser can be operated by continuous oscillation, pulse oscillation, or giant pulse oscillation by a Q switch.

  By the way, in the laser welding method, the optical connectivity between the material to be welded and the laser beam is important. If the optical connectivity is not good, the reflectivity increases, the laser energy absorption rate decreases, and it is difficult to obtain a good weld joint. In this respect, YAG laser light having a fundamental wavelength (for example, 1064 nm) does not have good optical connectivity with copper or gold. For these metals, it is rather known that the second harmonic (532 nm) YAG laser light has high optical coupling.

  In the patent document 1, the present applicant generates a YAG pulsed laser beam having a fundamental wavelength (1064 nm) with the first YAG laser and a second harmonic (532 nm) Q-switched laser beam with the second YAG laser. Disclosed is a different wavelength superposition laser welding method in which both materials are superimposed on the same axis and irradiated onto a material to be welded. Further, the present applicant has proposed a laser welding apparatus that generates a long pulse harmonic laser beam instead of a giant pulse (that is, without using a Q switch) and uses it for laser welding. Here, the long pulse has a variable pulse width and is typically 1 to 3 ms.

In general, a harmonic laser device for generating a harmonic laser beam is a method in which a wavelength conversion crystal is arranged in an optical resonator together with an active medium, and a fundamental wavelength is converted into a harmonic in the optical resonator (inside the resonator). Conversion method). In this method, only a harmonic light beam or a laser beam is taken out of the optical resonator while the light beam having the fundamental wavelength is confined in the optical resonator. In applications such as laser welding as described above, the output or power of the harmonic laser beam is a welding condition that affects the welding process. For this reason, it is necessary to adjust the optical system in the optical resonator so that the output of the harmonic laser beam is as set.
JP 2002-28795 A

  The wavelength conversion crystal as described above is optically coupled with a light beam having a fundamental wavelength in an optical resonator to generate a harmonic light beam by a nonlinear optical effect. For this reason, in order to optimize or stabilize the output or power of the harmonic, alignment or angle adjustment between the optical axis of the fundamental wave and the crystal axis of the wavelength conversion crystal is important.

  Conventionally, a wavelength conversion crystal unit that supports a wavelength conversion crystal at a predetermined position in an optical resonator has an angle adjustment mechanism for adjusting the angle (direction) of the wavelength conversion crystal with respect to the optical axis of the fundamental wave. . However, the angle adjustment mechanism in the conventional wavelength conversion crystal unit has only a uniaxial adjustment function for adjusting the angle of the wavelength conversion crystal in one direction (generally in a horizontal plane). For this reason, adjustment cannot be pursued, and it is difficult to optimize the angle of the wavelength conversion crystal.

  Further, the wavelength conversion crystal is very sensitive not only to the angle formed with the optical axis of the fundamental wave but also to the temperature. In this regard, the conventional wavelength conversion crystal unit adjusts the temperature of the wavelength conversion crystal at room temperature, for example, around 25 ° C. However, in the temperature control at room temperature, the temperature of the wavelength conversion crystal is easily affected by the ambient temperature, and a slight change in the crystal temperature causes a large change in the harmonic output.

  In addition, the conventional wavelength conversion crystal unit includes a thermo module for heating or cooling the wavelength conversion crystal for temperature adjustment, for example, a Peltier element below the wavelength conversion crystal, and the back or bottom surface of the thermo module is the base of the optical resonator. The structure which couple | bonds with a member thermally is taken. However, the layout of such a temperature control mechanism limits the height position of the wavelength conversion crystal, and thus limits the height position of other optical components in the optical resonator, and further, the angle adjustment mechanism as described above. The degree of freedom in the adjustment direction (axis) was also limited.

  The present invention has been made in view of the above-mentioned problems of the prior art, and provides a wavelength conversion crystal unit that can adjust the angle of the wavelength conversion crystal with respect to the optical axis of the fundamental wave as much as possible. For the purpose.

  Another object of the present invention is to provide a wavelength conversion crystal unit capable of easily optimizing the angle of the wavelength conversion crystal with respect to the optical axis of the fundamental wave.

  Another object of the present invention is to provide a wavelength conversion crystal unit that realizes the above object with a compact mechanism.

  Another object of the present invention is to provide a wavelength conversion crystal unit that stabilizes harmonic laser light by reducing the influence of the wavelength conversion crystal on the ambient temperature.

In order to achieve the above object, the wavelength conversion crystal unit of the present invention generates a second light beam of higher harmonics by nonlinear interaction with a first light beam having a fundamental wavelength in an optical resonator. A wavelength conversion crystal unit that supports the wavelength conversion crystal at a predetermined position, a crystal holding unit that holds the wavelength conversion crystal, and a central portion of the wavelength conversion crystal that is held by the crystal holding unit. A first angle adjusting unit that adjusts an angle of the wavelength conversion crystal with a first adjustment sensitivity in a first rotation direction having a first straight line passing through the first optical axis as a rotation axis; and the crystal holding unit. Of the wavelength conversion crystal in a second rotation direction with a second axis passing through the central portion of the wavelength conversion crystal held in the direction perpendicular to the optical axis of the light beam and the first straight line. The second adjusting the angle with the second adjustment sensitivity It possesses a degree adjusting unit, an output of the first adjustment sensitivity and the second light beam with respect to the angle of the wavelength conversion crystal difference in the first rotational direction and the second adjustment sensitivity This corresponds to the difference between the varying sensitivity and the sensitivity with which the output of the second light beam varies with respect to the angle of the wavelength conversion crystal in the second rotation direction.

  In the above configuration, the angle (orientation) of the wavelength conversion crystal with respect to the optical axis of the light beam can be arbitrarily and finely adjusted in two rotation directions that are orthogonal to each other, that is, the two axes. It can be optimized to the limit.

Further, according to the above configuration, the difference between the first adjustment sensitivity and the second adjustment sensitivity is such that the output of the second light beam varies with respect to the angle of the wavelength conversion crystal in the first rotation direction. Since it corresponds to the difference between the sensitivity of the output of the second light beam fluctuating with respect to the angle of the wavelength conversion crystal in the second rotation direction, the user or the operator can output the biaxial harmonics with the same adjustment feeling. Since the fluctuation can be adjusted, the adjustment can be quickly and easily performed.

  In the first angle adjustment unit, preferably, a rotation support unit that supports the crystal holding unit rotatably in the first rotation direction, and a relative position of the crystal support unit with respect to the rotation support unit in the first rotation direction. And a first feed screw mechanism for adjusting the first adjustment sensitivity by the first lead. Preferably, a configuration having a first link for converting the displacement of the linear movement by the first feed screw mechanism into the displacement of the crystal holding portion in the first rotation direction, and the first feed screw mechanism A configuration having a first spring that elastically deforms against forward feed or a configuration having a first fastening screw for fastening and fixing the crystal holding portion at a desired position with respect to the rotation support portion is adopted. Good.

  Also in the second angle adjustment section, preferably, a fixed support section fixed to the base member of the optical resonator to support the rotation support section so as to be rotatable in the second rotation direction, and a second rotation direction. And a second feed screw mechanism for adjusting the relative position of the rotation support portion with respect to the fixed support portion by the second lead, and the second adjustment sensitivity is defined by the second lead. Preferably, a configuration having a second link for converting the displacement of the linear movement by the second feed screw mechanism into the displacement of the crystal holding portion in the second rotation direction, or the second feed screw mechanism A configuration having a second spring that elastically deforms against forward feed or a configuration having a second fastening screw for fastening and fixing the crystal holding portion at a desired position with respect to the rotation support portion is adopted. Good.

  According to a preferred aspect of the present invention, the first straight line is a horizontal line and the second straight line is a vertical line. In addition, a thermo module for heating or cooling the wavelength conversion crystal for temperature adjustment is arranged substantially in parallel on one side in the horizontal direction of the wavelength conversion crystal. This thermo module may be composed of a Peltier element, for example. Such a temperature control layout does not require limiting the height position of the wavelength conversion crystal. In addition, a configuration in which the wavelength conversion crystal is accommodated together with the crystal holding part in a heat insulating housing having an opening on one surface, and a thermo module is provided in the opening is preferable. With such a heat insulating structure, heat dissipation to the surroundings can be prevented, and temperature rise in the optical resonator can be suppressed.

  The crystal temperature controller in the present invention operates so as to keep the temperature of the wavelength conversion crystal within the range of 45 ° C. to 55 ° C., most preferably around 50 ° C. In this way, according to the temperature adjustment at a set temperature that is one step higher than normal temperature, the wavelength conversion crystal temperature is stably maintained at a constant value, that is, the set temperature without being affected by the ambient temperature. The fluctuation of the higher harmonic output can be prevented.

  According to the harmonic conversion crystal unit of the present invention, with the configuration and operation as described above, the angle adjustment of the wavelength conversion crystal with respect to the optical axis of the fundamental wave is driven as much as possible to set the output of the harmonic as set. Can do. Further, the angle of the wavelength conversion crystal with respect to the optical axis of the fundamental wave can be easily optimized, and the biaxial adjustment function can be realized with a compact mechanism. Furthermore, it is possible to stabilize the harmonic laser light by reducing the influence of the wavelength conversion crystal on the ambient temperature.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a top view schematically showing the overall configuration of a harmonic laser apparatus to which a waveform conversion crystal unit according to an embodiment of the present invention can be applied. This harmonic laser device is a folded arrangement type on a base or support base (not shown in FIG. 1) having a substantially flat upper surface, a pair of terminal mirrors 10, 12, a solid-state laser active medium 14, a Q switch 16, a wavelength A conversion crystal 18 and intermediate mirrors 20 and 22 are arranged.

Both end mirrors 10 and 12 are optically opposed via intermediate mirrors 20 and 22 to form an optical resonator. The reflecting surfaces of one terminal mirror 10 and the intermediate mirror 20 are coated with a film that is reflective to the fundamental wave (1064 nm) of the YAG laser. The reflective surface of the other terminal mirror 12 is coated not only with a film reflective to the fundamental wave (1064 nm), but also with a film reflective to the second harmonic (532 nm). Yes. The intermediate mirror 22 is a harmonic separation output mirror, and its reflective surface is coated with a film reflective to the fundamental wave (1064 nm), and is transmissive to the second harmonic (532 nm). The membrane is coated.

  The active medium 14 is made of, for example, an Nd: YAG rod, is disposed between one terminal mirror 10 and the intermediate mirror 20, and is optically pumped by the electro-optic excitation unit 24. The electro-optic excitation unit 24 has an excitation light source (for example, an excitation lamp or a laser diode) for generating excitation light toward the active medium 14, and the excitation light source is controlled under the control of a control unit (not shown). The active medium 14 is continuously or intermittently pumped by being driven to light with an excitation current. In the illustrated configuration example, the side surface of the active medium 14 is irradiated with excitation light from the electro-optic excitation unit 24, but a method of irradiating the end surface of the active medium 14 (end surface excitation method) is also possible. The light beam having the fundamental wavelength generated in the active medium 14 is confined between the terminal mirrors 10 and 12 via the intermediate mirrors 20 and 22 and amplified. As described above, the light beam having the fundamental wavelength (1064 nm) or the fundamental laser beam LB is optically resonated by the both end mirrors (optical resonators) 10 and 12, the intermediate mirrors 20 and 22, the active medium 14, and the electro-optical excitation unit 24. A YAG laser oscillator generated inside is configured.

  The Q switch 16 is composed of, for example, an acousto-optic Q switch, and performs a switching operation in response to a high-frequency electric signal temporarily interrupted at a predetermined cycle from a Q switch driver (not shown). By this Q switching operation, every time a high-frequency electrical signal is interrupted in the optical resonator, a fundamental pulse laser beam LB having a very high peak power is generated.

The wavelength conversion crystal 18 is made of, for example, a prismatic LBO (LiB ₃ O ₅ ) crystal, and is disposed between the harmonic separation output mirror 22 and the termination mirror 12, and is optically converted into a fundamental mode excited by this optical resonator. And a second harmonic (532 nm) light beam SHG is generated on the optical path of the optical resonator by non-linear interaction with the fundamental wavelength.

  The second harmonic light beam SHG emitted from the wavelength conversion crystal 18 toward the terminal mirror 12 is returned by the terminal mirror 12 and passes through the wavelength conversion crystal 18. The second harmonic light beam SHG emitted from the wavelength conversion crystal 18 to the opposite side of the terminal mirror 12 is incident on the harmonic separation output mirror 22 and is transmitted straight through the mirror 22 and output to the outside of the optical resonator. It has become so.

  Outside the optical resonator, as an optical system for transmitting or irradiating the second harmonic light beam SHG extracted from the harmonic separation output mirror 22 toward the workpiece (for example, the workpiece) W, For example, mirrors 26 and 28 are provided. The workpiece W may be made of any metal, but a great advantage can be obtained particularly in the case of copper or gold.

  The wavelength conversion crystal 18 is detachably supported by the wavelength conversion crystal unit 30 in this embodiment. As will be described later, the wavelength conversion crystal unit 30 has an angle adjustment mechanism that can easily optimize the angle (orientation) of the wavelength conversion crystal 18 with respect to the optical axis of the optical resonator, that is, the optical axis of the fundamental wave, by a simple operation. I have.

  Hereinafter, the configuration and operation of the wavelength conversion crystal unit 30 will be described in detail. The structure of the wavelength conversion crystal unit 30 is shown in FIGS. 2 is a longitudinal sectional view, FIG. 3 is a left side view, FIG. 4 is a front view, FIG. 5 is a rear view, and FIG. 6 is a top view.

  The wavelength conversion crystal unit 30 includes a crystal housing 32 that holds the wavelength conversion crystal 18 in a fixed manner, and the orientation of the crystal housing 32 with respect to the optical axis (optical path) of the optical resonator (in particular, the angle of the wavelength conversion crystal 18). First and second angle adjusting mechanisms to be described later for adjusting in the first and second directions with a horizontal line and a vertical line passing through the central portion of the conversion crystal 18 as rotation axes.

  The crystal housing 32 is made of a heat insulating member such as a resin, is formed in a rectangular box shape, and is converted into a rectangular column or rod-like wavelength converter by a dish-shaped crystal holder 34 made of a material having high thermal conductivity such as copper provided in the housing. The crystal 18 is detachably mounted and fixed (FIG. 2). The crystal holder 34 is disposed with its crystal mounting surface facing sideways, and the wavelength conversion crystal 18 is disposed in the center of the crystal housing 32. Openings 32a and 34a for passing light beams (LB and SHG) are formed in the side walls of the crystal housing 32 and the crystal holder 34 facing both end faces of the wavelength conversion crystal 18 (FIG. 6).

  A thermo module 36 made of, for example, a Peltier element is connected to the back surface of the crystal holder 34. Physically, the thermo module 36 is provided in the opening 32b of the crystal housing 32, and the heat dissipation surface faces the inside of the crystal housing 32 (crystal holder 34) and the heat absorption surface faces the outside of the crystal housing 32 ( 2 and 6). Functionally, the thermo module 36 is connected to a power supply circuit for temperature control (not shown) via a cable 38, and from the outside of the crystal housing 32 (an endothermic surface) in accordance with a drive signal from the power supply circuit. It operates to absorb heat and dissipate heat into the crystal housing 32 (crystal holder 34). A temperature sensor 40 for detecting the temperature of the wavelength conversion crystal 18 is attached to the crystal holder 34 (FIG. 2). The output signal of the temperature sensor 40 is sent to a temperature control unit (not shown) via a signal line (not shown) so that the temperature of the wavelength conversion crystal 18 matches the set temperature. The heat absorption / heat radiation operation of the thermo module 36 is controlled through the power supply circuit.

  In this embodiment, the temperature of the wavelength conversion crystal 18 is set to 45 ° C. to 55 ° C. (most preferably 50 ° C.), which is one step higher than normal temperature, and the thermo module 36, the temperature sensor 40, and the control unit as described above. Further, feedback type temperature control is performed by the power supply circuit. Thus, according to the temperature adjustment at a set temperature that is one step higher than normal temperature, the temperature of the wavelength conversion crystal 18 is stably maintained at a constant value, that is, the set temperature without being affected by the ambient temperature (usually 35 ° C. or less). Is done. Thereby, the output fluctuation of the second harmonic SHG caused by the temperature fluctuation can be prevented.

  In addition, in this embodiment, since the crystal holder 34 and the wavelength conversion crystal 18 are thermally shut off from the outside by the resin crystal housing 32, heat radiation to the atmosphere is prevented and temperature rise in the resonator is suppressed. be able to. In addition, since the thermo module 36 is disposed beside the wavelength conversion crystal 18, that is, on one side in the horizontal direction, the height position of the wavelength conversion crystal 18 is not limited in terms of layout.

  The crystal housing 32 is fixed by a plurality of bolts 44 to a plate-like housing support portion 42 that extends in the vertical direction via the thermo module 36 (FIGS. 2 to 4). The housing support portion 42 is made of a material having high thermal conductivity, such as aluminum, and is in close contact with the back surface (heat absorption surface) of the thermo module 36 at its lower end portion.

  The housing support portion 42 is supported by a rotation support portion 46 that can rotate in a horizontal plane, and is attached to the rotation support portion 46 so as to be rotatable within a certain range (for example, ± 3 °) with a horizontal line H as a rotation axis. (Fig. 2). Here, the horizontal line H passes through the central portion of the wavelength conversion crystal 18 mounted on the crystal holder 34 in the crystal housing 32 so as to be orthogonal to the optical axis of the fundamental wave. On this horizontal line H, a round bar (rotary shaft) 42a of the housing support portion 42 is rotatably inserted into a round hole (bearing) 46a on the rotation support portion 46 side.

As shown in FIG. 5, at a position above the rotation axis H, an adjustment feed screw 48 is screwed through a screw hole 46 b formed in the rotation support portion 46, and the tip end portion of this feed screw 48. There has so presses the spring receiving portion 42b of the housing support portion 42 side at a predetermined oblique angle phi _1. On the other hand, the spring receiving portion 42 b is given a restoring force against the forward feed of the adjustment feed screw 48 by the coil spring 50 attached to the rotation support portion 48. By adjusting the screwing amount or the feeding amount of the adjusting feed screw 48, the wavelength conversion crystal accommodated in the orientation of the housing support 42 in the rotational direction θ _Y with the rotational axis H as the center of rotation, and consequently in the crystal housing 32, is obtained. The angle (orientation) of 18 can be adjusted. In this way, a link is formed for converting the displacement of the linear movement by the feed screw 48 into the displacement of the crystal housing 32 in the rotational direction θ _Y (that is, the displacement of the wavelength conversion crystal 18).

In the first angle adjusting mechanism constructed between the rotation support portion 46 and the crystal housing 32 as described above, the bolt 52 is a coil spring 54 that connects the housing support portion 42 and the rotation support portion 46 (FIG. 3). The spring force is adjusted from the back surface side of the rotation support portion 46 to the screw hole 42c (FIG. 4) on the housing support portion 42 side. The bolt 56 is a fastening screw for fixing the housing support portion 42 to the rotation support portion 46. The bolt 56 is tightened after the angle adjustment in the θ _Y direction by the adjustment feed screw 48 is completed, and the rear surface of the rotation support portion 46. It is screwed into the screw hole 42d (FIG. 4) of the housing support part 42 from the side.

Further, a rotation shaft 46c extends vertically downward from the lower surface of the rotation support portion 46, and the rotation shaft 46c is rotatably inserted into a bearing (not shown) formed on the upper surface of the support table 60 of the optical resonator. It is worn. Thereby, the rotation support part 46 can be rotationally displaced (within a horizontal plane on the support base 60) in the rotation direction θ _X with the axis M of the rotation shaft 46c as the rotation center. The rotation axis M is provided at a position that passes through the center of the wavelength conversion crystal 18 held by the crystal holder 34 in the crystal housing 32 in the vertical direction.

On the other hand, the rotation support portion 46 is connected to a fixed support portion 62 fixed to the support base 60 via a spring member. More specifically, as shown in FIGS. 5 and 6, a spring support portion 64 having an inclined surface 64 a is integrally provided at the lower end portion of the rotation support portion 46, and the spring support portion 64 and the fixed support portion are provided. A coil spring 66 is provided between the coil 62 and the coil 62. Then, a feed screw 68 for adjustment is screwed from above through the screw hole 62a formed in the fixed support portion 62, and the tip end portion of the feed screw 68 comes into contact with the inclined surface 64a of the spring receiving portion 64, and the coil spring. The spring receiving portion 64 is pressed in the direction in which 66 is compressed. By adjusting the screwing amount or feeding amount of the feed screw 68, the direction of the rotation support portion 46 in the rotation direction θ _X with the rotation axis M as the rotation center, and consequently the wavelength conversion crystal 18 accommodated in the crystal housing 32. The angle can be arbitrarily adjusted within a certain range (for example, ± 3 °). In this way, a link for converting the displacement of the linear movement by the feed screw 68 into the displacement of the crystal housing 32 in the rotational direction θ _X (that is, the displacement of the wavelength conversion crystal 18) is configured.

In the second rotation mechanism constructed between the rotation support portion 46 and the fixed support portion 62 as described above, the bolt 70 is a fastening screw for fixing the rotation support portion 46 to the support base 60, tightened after adjusting the angle of theta _X direction by the adjustment screw 68 completed is screwed from the rotating support 46 side into the screw hole of the support 60 (not shown). In order to pass the bolt 70, a long hole 46d extending in the rotation direction (θ _X direction) is formed in the rotation support portion 46 (FIG. 6).

As described above, in the wavelength conversion crystal unit 30 of this embodiment, the horizontal rotation axis H passing through the central part of the wavelength conversion crystal 18 mounted on the crystal holder 34 in the crystal housing 32 in the horizontal direction and the vertical direction, respectively. With the vertical rotation axis M as the center of rotation, the angle (direction) of the wavelength conversion crystal 18 with respect to the optical axis of the fundamental wave can be arbitrarily and finely adjusted in two rotation directions θ _Y and θ _X that are orthogonal to each other, that is, two axes. it can. As a result, the angle of the wavelength conversion crystal 18 can be optimized to the limit.

Moreover, in this embodiment, the angle change amount Δθ _Y when the adjustment feed screw 48 is rotated once in the first (θ _Y direction) angle adjustment mechanism is used as the sensitivity of the second harmonic output fluctuation in the same direction. In addition, the angle change amount Δθ ₂ when the adjustment feed screw 68 is rotated once in the second (θ _X direction) angle adjustment mechanism is made to correspond to the sensitivity of the second harmonic output fluctuation in the same direction. Thus, the biaxial adjustment sensitivity is made uniform so that the crystal angle can be easily optimized.

More specifically, this type of wavelength conversion crystal (LBO crystal, KTP crystal, etc.) differs in sensitivity to harmonic output fluctuations with respect to the angle formed with the optical axis of the fundamental wave. For example, in the example shown in FIG. 7, the sensitivity of the harmonic output fluctuation in the θ _Y direction is relatively low, and the sensitivity of the harmonic output fluctuation in the θ _X direction is relatively high. In this embodiment, in the first (θ _Y direction) and second (θ _X direction) angle adjustment mechanisms in correspondence with the difference in sensitivity of harmonic output fluctuations in both directions (θ _X, θ _Y ). The adjustment sensitivity is different. That is, the lead L ₆₈ of the adjustment feed screw 68 in the second (θ _X direction) angle adjustment mechanism is smaller than the lead L ₄₈ of the adjustment feed screw 48 in the first (θ _Y direction) angle adjustment mechanism. For example, L ₄₈ = 0.8 mm and L ₆₈ = 0.5 mm. Further, in the first (θ _Y direction) angle adjusting mechanism, the second angle (θ _X direction) is larger than the inclination angle φ ₁ (FIG. 5) of the adjusting feed screw 48 acting on the spring receiving portion 42b on the housing support portion 42 side. In this angle adjustment mechanism, the inclination angle φ ₂ (FIG. 5) of the adjustment feed screw 68 acting on the spring receiving portion 64 on the rotation support portion 46 side is set to a large value, for example, φ ₁ = 45 °, φ ₂ = 60. Set to ゜. In this way, by giving an appropriate difference in the angle adjustment sensitivity of the two axes, the adjustment sensitivity of the harmonic output fluctuation of the two axes with respect to the unit operation amount (for example, one rotation of the adjustment feed screw) is almost the same. can do. As a result, the user or the operator can adjust the biaxial harmonic output fluctuation with the same adjustment feeling, so that the adjustment can be quickly and easily performed.

In the characteristics of FIG. 7, the optimum crystal angle is adjusted to the angles θ _YM and θ _XM so that the harmonic output becomes the maximum value in each of the first (θ _Y direction) and the second (θ _X direction). It becomes.

Further, the first (θ _Y direction) and second (θ _X direction) angle adjustment mechanisms in the wavelength conversion crystal unit 30 of this embodiment extend to the side of the wavelength conversion crystal 18, that is, to one side in the horizontal direction. The space occupied in the front-rear direction of the wavelength conversion crystal 18 is very small. For this reason, the above two-axis adjustment is realized without increasing the optical path length of the resonator, that is, with a compact configuration.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea.

For example, in the above embodiment, the Peltier element is used for the thermo module for adjusting the temperature of the wavelength conversion crystal 18, but other types of thermo modules such as a type using a medium such as temperature adjusting water or a resistance heating element are used. A type using a heating element is also possible. Moreover, although the above-described embodiment relates to a Q-switch type harmonic laser device, the present invention can also be applied to a long-pulse type harmonic laser device that does not use a Q switch. Further, the present invention is not limited to the harmonic laser device that generates the second harmonic light beam, and other harmonics such as the third harmonic and the fourth harmonic light beam are generated. It is also applicable to.

It is a top view which shows typically the whole structure of the harmonic laser apparatus to which the wavelength conversion crystal unit by one Embodiment of this invention is applied. It is a longitudinal cross-sectional view which shows the structure of the wavelength conversion crystal unit in embodiment. It is a left view which shows the structure of the wavelength conversion crystal unit in embodiment. It is a front view which shows the structure of the wavelength conversion crystal unit in embodiment. It is a rear view which shows the structure of the wavelength conversion crystal unit in embodiment. It is a top view which shows the structure of the wavelength conversion crystal unit in embodiment. It is a figure which shows the angle-harmonic output characteristic of the biaxial direction in a wavelength conversion crystal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,12 Termination mirror 14 Active medium 18 Wavelength conversion crystal 20 Intermediate mirror 22 Harmonic separation output mirror 24 Electro-optic excitation part 30 Wavelength conversion crystal unit 32 Crystal 34 Crystal holding part 36 Thermo module 40 Temperature sensor 42 Housing support part 42a Rotating shaft 42b Spring receiving portion 46 Rotation support portion 46a Bearing 46c Rotating shaft 48 Adjustment feed screw 50 Coil spring 56 Bolt (fastening screw)
60 support base 62 fixed support portion 64 spring receiving portion 66 coil spring 68 feed screw for adjustment 72 bolt (fastening screw)

Claims (15)

A wavelength conversion crystal unit for supporting a wavelength conversion crystal for generating a second light beam of higher harmonics by a nonlinear interaction with a first light beam having a fundamental wavelength in an optical resonator at a predetermined position;
A crystal holding unit for holding the wavelength conversion crystal;
The angle of the wavelength conversion crystal is set in a first rotation direction with a first straight line passing through a central portion of the wavelength conversion crystal held by the crystal holding unit orthogonal to the optical axis of the light beam as a rotation axis. A first angle adjustment unit for adjusting with the first adjustment sensitivity;
In the second rotation direction with the second axis passing through the central portion of the wavelength conversion crystal held by the crystal holding unit orthogonal to the optical axis of the light beam and the first straight line as the rotation axis have a second angle adjusting section for adjusting the angle of the wavelength conversion crystal in the second adjustment sensitivity,
The difference between the first adjustment sensitivity and the second adjustment sensitivity is that the output of the second light beam varies with respect to the angle of the wavelength conversion crystal in the first rotation direction and the second adjustment sensitivity. Corresponding to the difference in sensitivity with which the output of the second light beam varies with respect to the angle of the wavelength converting crystal in the rotation direction;
Wavelength conversion crystal unit. The first angle adjustment unit includes a rotation support unit that rotatably supports the crystal holding unit in the first rotation direction, and a relative relationship between the crystal holding unit and the rotation support unit in the first rotation direction. and a first feed screw mechanism for adjusting the Do position in the first lead, defining the first adjusting sensitivity in the first lead, the wavelength conversion crystal unit according to claim 1. It said first angle adjusting unit has a first link for converting the displacement of the linear movement by the first feed screw mechanism to the displacement of the crystal holding portions in the first rotational direction, to claim 2 The wavelength conversion crystal unit described. Said first angle adjusting portion has a first spring which elastically deforms against the forward feed of the first feed screw mechanism, the wavelength conversion crystal unit according to claim 2 or claim 3. It said first angle adjusting portion has a first fastening screw for fastening and fixing the crystal holder at a desired position with respect to the rotating support, in any one of claims 2-4 The wavelength conversion crystal unit described. The second angle adjusting unit fixed to a base member of the optical resonator to support the rotation support unit rotatably in the second rotation direction; and the second rotation direction. And a second feed screw mechanism for adjusting a relative position of the rotation support portion with respect to the fixed support portion by a second lead, and the second adjustment sensitivity is defined by the second lead. to, the wavelength conversion crystal unit according to any one of claims 1-5. The second angle adjusting unit, a second link for converting the displacement of the linear movement of the second feed screw mechanism to the displacement of the crystal holder in the second rotational direction, in claim 6 The wavelength conversion crystal unit described. The second angle adjusting section has a second spring which elastically deforms against the forward feed of the second feed screw mechanism, the wavelength conversion crystal unit according to claim 6 or claim 7. The second angle adjusting section has a second fastening screws for the fastening and fixing the crystal holder at a desired position with respect to the rotation supporting portion, to any one of claims 6-8 The wavelength conversion crystal unit described. Wherein the first straight horizontal line, said second straight line is a vertical line, the wavelength conversion crystal unit according to any one of claims 1-9. Thermo module is disposed substantially parallel to the horizontal direction on one side of the wavelength conversion crystal, the wavelength conversion crystal unit according to any one of claims 1 to 10 for heating or cooling for temperature regulating the wavelength conversion crystal. It said thermo module has a Peltier element, a wavelength conversion crystal unit according to claim 11. The wavelength conversion crystal unit according to claim 11 or 12 , wherein the wavelength conversion crystal is accommodated in a heat insulating housing having an opening on one surface, and the temperature control module is provided in the opening. The wavelength conversion crystal unit according to any one of claims 1 to 13 , further comprising a crystal temperature control unit for maintaining the temperature of the wavelength conversion crystal within a range of 45 ° C to 55 ° C. The wavelength conversion crystal unit according to claim 14 , wherein the crystal temperature control unit maintains the temperature of the wavelength conversion crystal at around 50 ° C.

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