JP2007317871A - Laser apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate a light axis adjustment work in a laser apparatus including an external resonator. <P>SOLUTION: The laser apparatus includes: a laser light source 1, the external resonator 14 having an input coupled element 9, an optical detection element 6, and light axis adjustment tools. A specified position between the light axis adjustment tools 4a, 4b arranged at the side of the laser light source 1 and the light receiving surface of the optical detection element 6 are disposed in geometrical optics conjugate relation. For example, when a pair of mirrors is defined as the light axis adjustment tools so as to obtain a conjugate point between them, a spot position change amount is suppressed on the optical detection element 6. Then, the light axis is adjusted without moving the optical detection element 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser device having a laser light source and converting a wavelength in an external resonator.

  A laser device that couples a laser beam from a laser light source to an external resonator and resonates is well known, and is mainly used for wavelength conversion by a nonlinear optical crystal disposed inside the resonator, particularly for a second harmonic generation device. (See, for example, Patent Document 1).

On the other hand, in recent years, photodynamic therapy (PDT) has attracted attention in the medical field. In this method, a tumor-affinity photosensitizer that is more easily absorbed into cancer cells than normal cells and has an action of generating active oxygen by light absorption and killing cancer cells is administered to a patient by intravenous injection, The cancer cells are killed by irradiating a laser beam having a wavelength that is easily absorbed by the sensitizer. PDT has been shown to have therapeutic effects on early superficial cancers, such as lung cancer, esophageal cancer, stomach cancer, and uterine cancer, by combining or substituting with conventional cancer therapies. There are the following features.
(1) Cancer cells can be destroyed with minimal damage to normal cells.
(2) The function of organs after treatment can be maintained, and the “quality of life (QOF)” after treatment can be maintained.
(3) Re-treatment as necessary is possible.
(4) Applicable to patients with weak physical strength.
A light source suitable for PDT is a continuous wave laser having a wavelength of around 650 nm. This wavelength is advantageous in that it corresponds to the absorption wavelength of the photosensitive substance used for the treatment, and the continuous wave has a smaller peak power than the pulse wave, so that damage to normal cells can be reduced.
JP-A-8-116122

  Conventionally, a red semiconductor laser is known as a continuous wave laser having a wavelength near 650 nm, but the output of the red semiconductor laser is too small. Moreover, since the light emitted from the red semiconductor laser has a wide oscillation line width over a wide wavelength range, the absorption efficiency to the photosensitive material is low, and much light is not absorbed by the photosensitive material. The energy of light that is not absorbed by the photosensitizer usually damages the cells. Therefore, a laser having a narrow oscillation line width is demanded.

  On the other hand, lasers with a narrow line width are well known in the wavelength band of 1000 nm or more, so in order to create a wavelength near 650 nm with a narrow line width, a 1300 nm laser is guided to an external resonator and placed in the resonator. The second harmonic may be generated from the nonlinear optical crystal. However, when manufacturing a laser device that converts the wavelength of light in such a wavelength band using an external resonator, there are problems as described below.

  In such assembly adjustment work of the laser device, in order to achieve resonance of the external resonator, it is indispensable to adjust the optical axis of the laser light from the laser light source 101 and make mode matching with the external resonator. The optical axis adjustment is usually performed by a mirror disposed between the laser light source and the external resonator. Since the optical axis has two components, an angle and a parallel movement, at least two mirrors are required as an optical axis adjuster for setting these components arbitrarily.

  An example of the adjustment procedure will be described with reference to FIG. 12 showing a schematic configuration of an example of a laser apparatus having an external resonator. As shown in FIG. 12, this laser device includes a laser light source 101, a phase modulator 102, a lens 103, a pair of adjustment mirrors 104a and 104b as optical axis adjusters, an external resonator 114, a collimator lens 105, and a light detection device. The element 106 is configured. The external resonator 114 includes an input coupling mirror 109, a mirror 110, and resonator mirrors 111a and 111b, and a nonlinear optical crystal 112 is disposed between the resonator mirrors 111a and 111b. Further, the output from the light detection element 106 is output to the control circuit 107 and the oscilloscope 108.

In such a configuration, the laser light emitted from the laser light source 101 is reflected by the adjustment mirrors 104 a and 104 b through the lens 103 and guided to the external resonator 114 through the input coupling mirror 109. The mirror 110 constituting the external resonator 114 is reciprocated back and forth by the actuator 113 to change the resonator length minutely, while receiving the reflected light from the input coupling mirror 109 by the light detection element 106 and receiving the output signal thereof. Monitor with oscilloscope 108.
If mode matching, that is, optical axis adjustment is not performed at all, a constant signal level is detected as shown in FIG. 13A. When the optical axis is adjusted by adjusting the angles of the adjusting mirrors 104a and 104b and the mode matching rate is gradually increased, light is drawn into the resonator when the resonator length becomes an integral multiple of the wavelength. As shown by being surrounded by a broken line _SD in FIG. 13B, a signal called a dip in which the current value decreases appears. As shown in FIG. 13C, the mode matching adjustment is finished when the dip is deepest. In this operation, the optical axis of the beam is changed by adjusting the angle of the mirror, and at the same time, the direction of the beam reflected by the input coupling mirror 109 and directed to the light detection element 106 is also changed.
In addition, as shown in FIG. 12, by arranging the phase modulator 102 between the laser light source 101 and the lens 103, the monitor sideband light (the wavelength of the light source) in the use state after the mode matching. light having a wavelength of ± Δλ with respect to λ) can be generated, and the conversion light rate of the light of wavelength λ in the external resonator 114 can be monitored using these lights. Based on this result, for example, by adjusting an actuator 113 such as a VCM (Voice Coil Motor) attached to the mirror 110 constituting the external resonator 114, for example, variations in the output of the second harmonic due to the nonlinear optical crystal 112 are suppressed. be able to.

  In the current laser apparatus, the light receiving surface of the light detection element 106 is positioned near the back focal position of the collimator lens 105 disposed between the input coupling mirror 109 and the light detection element 106. For this reason, the laser beam on the light receiving surface moves in a direction perpendicular to the optical axis due to the change of the optical axis accompanying the adjustment, and is deviated from the inside of the light receiving surface. An example of the change of the signal at this time is schematically shown in FIGS. The laser light deviates from the light receiving surface, and the signal level decreases as shown by solid lines d1 and d2 in FIGS. 14A and 14B, or no signal can be obtained as shown by the solid line d3 in FIG. 14C. In such a case, it is necessary to perform an operation of shifting the position of the light detection element by an amount corresponding to the shift of the light receiving position from the optical axis.

On the other hand, in the light detection element, there is a problem that the light response speed of the InGaAs photodiode, which is a light detection element having sensitivity at 1300 nm which is near infrared, is slow.
FIG. 15 is a diagram showing a change in the cut-off frequency with respect to the diameter of the light receiving portion in the silicon photodiode and the InGaAs photodiode used for visible light. Note that the higher the cutoff frequency, the faster the optical response speed. As can be seen from FIG. 15, it can be seen that the InGaAs photodiode has a much slower optical response speed than the silicon photodiode when compared with the same light receiving portion diameter. When the light response speed of the light detection element is slow, servo locking becomes unstable, resulting in a noisy laser. As an example, when output monitoring is performed using sideband light as described above, a response speed of 20 MHz or higher, preferably about 50 MHz is required. Therefore, in order to obtain an optical response speed equivalent to that of a silicon photodiode using an InGaAs photodiode, a light receiving portion having a very small diameter must be used.
As described above, when the InGaAs photodiode is used as a light detection element and the light receiving portion diameter is reduced in order to increase the response speed, as described above, the number of times the position of the light detection element 106 is shifted during the optical axis adjustment is extremely large. This increases the difficulty of adjustment work. Moreover, even if the adjustment is possible, there is a problem that the work takes time and the cost becomes enormous. Such an optical axis adjustment is necessary even when the nonlinear optical crystal 112 disposed in the external resonator 114 is replaced due to deterioration or the like. Therefore, not only in the manufacturing process of the apparatus but also in maintenance and repair work. Therefore, it is strongly desired to shorten the time for such adjustment work.
In recent years, laser devices are increasingly used in semiconductor factories due to miniaturization of semiconductor design rules. It is essential to replace the laser light source incorporated in these laser devices according to its life. However, in the semiconductor factory, since the downtime of the apparatus is directly related to the manufacturing cost of the semiconductor device, replacement and maintenance work in a short time is required.

  In view of the above problems, it is an object of the present invention to simplify the optical axis adjustment work in a laser apparatus including an external resonator as described above.

In order to solve the above problems, the present invention provides a laser light source, an external resonator having an input coupling element, a light detection element, and a laser light source to the external resonator based on a light output detected by the light detection element. And an optical axis adjuster for aligning the optical axis of the laser beam, and a specific position between the optical axis adjuster arranged on the light source side and the input coupling element of the external resonator, The light receiving surface is arranged in a geometric optical conjugate relationship.
According to the present invention, in the above laser apparatus, the optical axis adjuster is a pair of mirrors.
Furthermore, the present invention is characterized in that the specific position is provided between the pair of mirrors in the laser apparatus described above.

According to the above-described present invention, in the laser device having the external resonator, the optical axis adjuster for aligning the optical axis of the laser light from the laser light source to the external resonator and the input coupling element of the external resonator. The specific position is arranged in a geometric optical conjugate relationship with the light receiving surface of the light detection element.
By adopting such a configuration, as will be described later, when the optical axis is deflected or moved by the optical axis adjuster, the amount of movement of the spot position of the laser beam on the light receiving surface of the light detection element is reduced. Can do. Therefore, the optical axis adjustment work can be simplified.
In particular, by using a pair of mirrors as an optical axis adjuster and placing a specific position in a conjugate relationship with the light receiving surface of the light detection element between them, the amount of movement of the laser beam spot position can be reliably reduced. it can. Therefore, it is possible to avoid the light spot from deviating from the light receiving region of the light detection element, and the optical axis can be adjusted without moving the light detection element. Can be greatly simplified.

  ADVANTAGE OF THE INVENTION According to this invention, in a laser apparatus provided with an external resonator, simplification of an optical axis adjustment work can be achieved.

Examples of the best mode for carrying out the present invention will be described below, but the present invention is not limited to the following examples.
First, in the case where the optical axis is adjusted by two mirrors in the laser device, how much the optical axis position on the light detection element changes with respect to the displacement amount of the two mirrors is shown in FIG. This will be described with reference to the schematic configuration diagram.
The laser apparatus shown in FIG. 1 includes an example including a laser light source 101 that oscillates a continuous wave, a pair of adjustment mirrors 104 a and 104 b as optical axis adjustment tools, an external resonator 114, an optical lens 115, and a light detection element 106. Show. The external resonator 114 includes an input coupling mirror 109 and mirrors 110, 111a, and 111b. In this example, the nonlinear optical crystal 112 is disposed between the mirrors 111a and 111b that serve as resonator mirrors. Incidentally, it is shown dashed A'an optical axis of the front optical axis adjustment, the optical axis after the optical axis adjustment by the solid line A ₀ in FIG.

In such a configuration, the angular displacement amounts of the adjustment mirrors 104a and 104b are (α1, β1) and (α2, β2), respectively. Here α is a mirror 104a, a plane along the reflective surface and the optical axis _{A 0} of 104b, that is, angular displacement, one-dot chain line β is along the reflecting surface of the adjustment mirror 104a and 104b s1 and s2 in the plane of FIG. 1 It is assumed that the angular displacement with the direction in the drawing of FIG. In FIG. 1, arrows α1, α2, β1, and β2 indicate + directions of this angular displacement, respectively. At this time, the amount of movement in the plane perpendicular to the optical axis on the light receiving surface of the photodetecting element 106 is expressed by the following equations (1) and (2). In the plane perpendicular to the optical axis, the displacement in the direction along the paper surface of FIG. 1 (indicated by an arrow h) is denoted by Dh, and the direction orthogonal to the paper surface of FIG. f is the focal length of the optical lens 115.

Dh = 2f × tan (α1 + α2) (1)
Dv = 2f × tan (β1 + β2) (2)

  According to the present invention, for example, among the adjustment mirrors used as the optical axis adjustment tool, an arbitrary point between the one close to the light source and the input coupling element of the external resonator, particularly preferably between the two adjustment mirrors. The specific position and the light receiving surface of the light detection element are arranged so as to be geometrically conjugate with each other. By setting the conjugate position, the amount of movement of the laser beam on the light receiving surface of the photodetecting element when the optical axis is adjusted by angularly displacing the adjusting mirror can be reduced as described below.

  FIG. 2 is a schematic configuration diagram of an example of a laser apparatus according to an embodiment of the present invention. In this example, a laser light source 1 that oscillates a continuous wave, an external resonator 14 having an input coupling element 9, an optical lens 5, a light detection element 6, and a light output detected by the light detection element 6. Based on this, an example in which an optical axis adjusting tool for adjusting the optical axis of the laser beam from the laser light source 1 to the external resonator 14 and so-called mode matching, in this case, the adjustment mirrors 4a and 4b is shown. In this example, the specific position C1 between the adjustment mirror 4a on the light source 1 side and the optical coupling element 9 is arranged so as to be a geometrical conjugate position with the light receiving surface of the light detection element 6. In this example, the specific position C1 is arranged between the adjustment mirrors 4a and 4b. In FIG. 2, the optical axis before adjustment of the optical axis is indicated by a broken line A1, and the optical axis after adjustment of the optical axis is indicated by a solid line A.

  Here, as shown in FIG. 2, the distances from the adjustment mirrors 4a and 4b to the specific position C1 which is a geometrically conjugate position with the light receiving surface of the light detecting element 6 are P1 and P2, respectively. In addition, a code | symbol makes the advancing direction of light +. Further, the lateral magnification at which the conjugate specific position C1 is imaged on the light receiving surface of the light detecting element 6 is k, and the angular displacement amounts of the adjustment mirrors 4a and 4b are (α1, β1), (α2, β2), respectively. In this case (the signs of α and β are the same as those in the example shown in FIG. 1), the movement amount D of the spot position on the light receiving surface of the light detecting element 6 is expressed by the following equations (3) and (4). Is done. Also in this case, the displacement in the direction (indicated by the arrow h) along the plane of FIG. 2 in the plane perpendicular to the optical axis A is indicated as Dh, and the direction orthogonal to the plane of the paper in FIG. 2 (indicated by arrow v) is indicated as Dv.

Dh = 2k × {P1 × tan α1-P2 × tan (α2-α1)} (3)
Dv = 2k × {P1 × tan β1-P2 × tan (β2-β1)} (4)

  As described above, when adjusting the optical axis using the two adjustment mirrors 4a and 4b, if the optical axes are rotated in the same direction, the change in the angle of the optical axis is canceled out. Therefore, the optical axes are rotated in opposite directions. There are many cases. If there is a conjugate point between the adjustment mirrors 4a and 4b, the sign of P1 is positive and the sign of P2 is negative, which cancels each other, thereby reducing the absolute values of the movement amounts Dh and Dv. There is. On the other hand, if there is no conjugate point between the adjustment mirrors 4a and 4b, P1 and P2 have the same sign, and the absolute value of the movement amount increases.

Therefore, it can be seen that the specific position that is geometrically conjugate with the light receiving surface of the light detection element 6 is preferably between the two adjustment mirrors. In particular, when the rotation angles α1, α2, β1, and β2 are substantially the same, the fluctuation amount D of the light spot position can be minimized by being positioned at the intermediate point between the adjustment mirrors 4a and 4b.
Even when the specific position C1 is disposed between the adjustment mirror 4b and the optical coupling element 9, the amount of movement of the spot on the light receiving surface of the light detection element 6 can be suppressed as compared with the conventional case. The optical axis adjustment work can be simplified.

The required amount of optical axis adjustment basically varies depending on the mechanical accuracy when the input coupling element 9 of the external resonator 14 is arranged. In addition, when the nonlinear optical crystal 12 is replaced, the optical axis adjustment amount varies depending on the surface accuracy of the incident / exit surface of each nonlinear optical crystal 12.
Therefore, it is generally unclear where the specific position C1 is preferably arranged, but when using a pair of adjustment mirrors 4a and 4b, when using mirrors having substantially the same shape, these will be described later. It can be said that it is desirable to set the range to a quarter of the distance between the mirrors 4a and 4b from the midpoint between the mirrors 4a and 4b.
On the other hand, when the distance and size of the adjustment mirrors 4a and 4b and the curvature are provided, and the optical axis adjustment amount of one adjustment mirror is large, the optical axis adjustment amount is increased. It can be said that it is desirable to arrange the specific position C1 in the vicinity of the adjustment mirror.

Next, an example in which a wedge plate 21 as shown in FIG. 3 is used as an optical axis adjustment tool instead of the adjustment mirror will be described.
As shown in FIG. 3, when the wedge angle formed by the entrance surface and the exit surface of the wedge plate 21 is θ and the refractive index is n, the deflection angle δ of the light beam passing through the wedge plate 21 is
δ = (n−1) × θ
It becomes.
In the single wedge plate, when the wedge plate is rotated about the optical axis, the light beam draws a circle. On the other hand, when two identical wedge plates are faced to each other and rotated by an appropriate angle around the optical axis, an arbitrary three-dimensional deviation angle of 2 × (n−1) × θ to 0 is obtained. The light beam can be polarized in the direction, and an optical axis adjusting action equivalent to that of two mirrors can be obtained.
This will be described below with reference to the drawings.
4A and 4B are schematic cross-sectional configuration diagrams of a pair of wedge plate units 22a and 22b in which two wedge plates having a surface orthogonal to the optical axis are prepared and the surfaces orthogonal to the optical axis are opposed to each other.
4A shows a state where the optical axis B of the incident light is substantially translated, and FIG. 4B shows a case where the wedge plates 22a and 22b are rotated to deflect the optical axis B of the incident light downward.

FIGS. 5A to 5E show states in which each wedge plate is rotated to deflect or translate the optical axis at various angles. 5A to 5E show the movement of the optical axis by the coordinates of the x-axis (horizontal direction) and the y-axis (vertical direction). FIG. 5A shows a case where the optical axis B is arranged so as to be perpendicular to the origin of the xy coordinates after passing through the wedge plates 22A and 22B. As shown in FIG. 5B, when the wedge plates 22a and 22b are rotated 90 ° rightward and leftward in the light traveling direction as indicated by arrows wa and wb, respectively, the optical axis B is positive in the x-axis direction. The angle θ _{x0 is} deflected to the side. As shown in FIG. 5C, when the wedge plates 22a and 22b are further rotated by 90 ° as indicated by arrows wa and wb, the optical axis B moves y ₀ parallel to the y axis direction negative side. As shown in FIG. 5D, when the wedge plates 22a and 22b are further rotated by 90 °, the optical axis B is deflected by the angle θ _{x0 to the} negative side in the x-axis direction. As shown in FIG. 5E, when the wedge plates 22a and 22b are further rotated by 90 °, the optical axis B returns to the original position shown in FIG. 5A.
Further, when the wedge plates 22a and 22b shown in FIG. 5B are rotated by 90 ° in the same direction, the angle can be deflected in the y-axis direction, and the deflection angle can be adjusted by adjusting the rotation angle. Further, when the wedge plates 22a and 22b shown in FIG. 5C are rotated in the same direction, parallel movement into the xy plane is possible.

5A to 5E, the amount of parallel movement can be adjusted by making the distance between the wedge plates 22a and 22b adjustable. In this case, the optical axis adjuster can be configured with only two wedge plates.
On the other hand, by providing two sets of wedge plate units each consisting of two similar wedge plates, the angle and parallel movement can be adjusted only by the rotation mechanism of each wedge plate.

  In FIG. 6, the schematic block diagram of an example of a structure which uses two sets of wedge board units as an optical-axis adjustment tool in the laser apparatus which concerns on the embodiment of this invention is shown. In FIG. 6, parts corresponding to those in FIG. In this example, the wedge plate units 22 and 23 having the configuration described with reference to FIGS. 5A to E are used, and the light receiving surface of the light detection element 6 is positioned at a specific position C2 between the wedge plate units 22 and 23. A point that is geometrically conjugate is provided. In this example, an example is shown in which the specific position C2 is arranged at a substantially intermediate position between the wedge plate units 22 and 23. The amount of variation in the position of the light spot on the light receiving surface of the light detecting element 6 due to the deflection and translation of the optical axis by the wedge plate units 22 and 23 is the same as in the case of using the pair of mirrors (3) and (4). Is applicable. Therefore, by adopting such a configuration, it is possible to reduce the movement amount D of the light spot position on the light receiving surface of the light detecting element 6 as in the example shown in FIG.

  In addition, when the wedge board units 22 and 23 are comprised from the combination of the wedge board of the same shape, it is preferable to arrange | position the specific position C2 which becomes conjugate in the substantially middle position of the wedge board units 22 and 23. FIG.

FIG. 7 is a schematic configuration diagram of an example of a laser apparatus according to another embodiment of the present invention. In FIG. 7, parts corresponding to those in FIG.
In this example, a case where light emitted from the laser light source 1 is incident on a collimator lens 34 used as an optical axis adjuster via an optical fiber 32 is shown. The collimator lens 34 is disposed in a collimator lens unit 35 having a tilt rotation mechanism and a parallel movement mechanism (not shown). The optical coupling element 33 at the output end of the optical fiber 32 is fixed to one end of the collimator lens unit 35. By the tilt rotation mechanism and the parallel movement mechanism of the collimator lens unit 35, the emission angle deflection and the optical axis translation of the collimator lens 34 can be performed in the rotation direction indicated by the arrow t and also in the directions indicated by the arrows m1 and m2. In this way, by making the light emitted from the light source 1 incident on the collimator lens 34 by the optical fiber 32, the light can be incident on the rotation and translation of the collimator lens 34 without impairing the coupling efficiency. Has the advantage of being able to

  In this example, the rotation center C3 of the tilt rotation mechanism is disposed so as to be geometrically conjugate with the light receiving surface of the light detection element 6. By adopting such a configuration, it is possible to reduce the movement amount D of the light spot position on the light receiving surface of the light detection element 6 as in the example shown in FIGS. 1 and 6 described above. In particular, since the rotation center C3 of the tilt rotation adjustment is at a position conjugate with the light receiving surface of the light detection element 6, there is no movement of the light spot on the light receiving surface depending on the tilt adjustment. Since only the shift due to the parallel movement adjustment in the plane perpendicular to the optical axis is related to the spot movement, the optical axis adjustment work can be greatly simplified.

  As described above, according to the present invention, it is not necessary to move the position of the light detection element at the time of mode matching to the external resonator, that is, the optical axis adjustment, and the adjustment work time can be greatly shortened. It becomes. Further, adjustment is possible even if not necessarily a skilled worker. Therefore, it is possible to reduce both the time and personnel required for adjustment work including assembly and maintenance, and it is possible to greatly reduce the cost.

Next, the first to fifth embodiments in which more specific dimensions and shapes are studied for the laser device in the above-described embodiment will be described.
[1] First Embodiment FIG. 8 shows a schematic configuration diagram of a laser apparatus according to a first embodiment of the present invention. In FIG. 8, parts corresponding to those in FIG. In this example, a continuous wave laser having a beam waist having a wavelength of 1300 nm, M ² = 1, and a diameter of 1 mm at the exit is used as the laser light source 1. An optical lens 2 is disposed on the emission light path of the laser light source 1. The optical lens 2 is a plano-convex lens having a convex surface facing the laser light source 1, a curvature radius of 151.1 mm, a thickness of 2.5 mm, a material of BK7 (manufactured by Schott Co., Ltd., trade name), and a focal length of 300 mm, and has an effect of mode matching the laser light from the laser light source 1 to the external resonator 14 described later. In this example, a pair of adjustment mirrors 4a and 4b is used as an optical axis adjustment tool. At the incident position of the laser beam of the external resonator 14, an input coupling element 9 such as an input coupling mirror made of a semi-transparent mirror is arranged. A semi-transmissive film is formed on the surface of the input coupling element 9 on the external resonator 14 side. The optical lens 5 disposed between the input coupling element 9 and the light detection element 6 is a plano-convex lens having a convex surface facing the input coupling element 9 side. In this case, the radius of curvature is 23.4 mm, the thickness is 2.5 mm, the material is BK7 (trade name, manufactured by Schott Co., Ltd.), the focal length is 46.5 mm, and the light is condensed on the light receiving surface of the light detecting element 6. Have the effect of The light detecting element 6 is a PIN (P-Intrinsic-N) photodiode made of InGaAs, and the size of the light receiving surface is 0.8 mm in diameter. C4 indicates a specific position conjugate with the light receiving surface of the light detecting element 6 by the optical lens 5.

The external resonator 14 includes an input coupling element 9 and other mirrors 10, 11a, and 11b. The input coupling element 9 is flat on both sides, the material is synthetic quartz, and the thickness is 3 mm. The mirror 10 is a plane mirror, and the mirrors 11a and 11b are concave mirrors having a curvature radius of 125 mm. The incident angles to the input coupling element 9 and the mirrors 10, 11a and 11b are set to 10 °, respectively. Further, a BBO (β-BaB ₂ O ₄ ) crystal having a thickness of 4 mm, for example, is disposed between the mirrors 11 a and 11 b as the nonlinear optical crystal 12.
Here, the distance and optical path length of each part are set as follows.

Distance from the exit of the laser light source 1 to the lens 2 a1 = 300 mm
Distance from lens 2 to mirror 4a a2 = 18.3mm
Distance from mirror 4b to resonator side surface of input coupling element 9 a3 = 74 mm
Distance from the resonator-side surface of the input coupling element 9 to the lens 5 a4 = 100 mm
Distance from lens 5 to light receiving surface of light detecting element 6 a5 = 55.7 mm
Distance from mirror 4a to C4 p1 = 70mm
Distance from mirror 4b to C4 p2 = -70mm
Optical path length between input coupling element 9 and mirror 10 w1 = 132 mm
Optical path length between mirror 10 and mirror 11a w2 = 150 mm
Optical path length between mirrors 11a and 11b w3 = 150mm
Optical path length between the mirror 11b and the input coupling element 9 w4 = 150 mm

In the above configuration, the diameter of the laser beam at the specific position C4 is 0.43 mm, and the magnification k at which the position C4 forms an image on the light receiving surface of the light detecting element 6 is −0.23. The laser beam diameter at is 0.1 mm.
In the first embodiment, the amount of beam movement on the light receiving surface of the light detection element 6 when the mode matching adjustment is performed using the adjustment mirrors 4a and 4b is calculated. When the adjustment mirror 4a on the light source 1 side is tilted 0.5 ° clockwise in the plane of FIG. 8 and the adjustment mirror 4b on the resonator side is tilted 0.5 ° counterclockwise in the plane of FIG. From the above equation (3), the moving amount of the laser beam is 0.28 mm. If the laser beam is positioned at the center of the light receiving surface of the light detecting element 6 before the adjustment is started, it can be understood that the laser beam stays within the light receiving surface even by the adjustment. Therefore, in this case, the mode matching adjustment can be performed without moving the position of the light detection element 6.

  On the other hand, when the arrangement is the same as the conventional arrangement in which the light receiving surface of the light detection element 6 is arranged at the rear focal position of the optical lens 5 without using the configuration of the present invention, the amount of movement is calculated as the above formula ( Due to 1), the distance becomes 0.8 mm, and the laser beam deviates from the light receiving surface of the light detecting element 6. In this case, the distance between the optical lens 5 and the light receiving surface of the light detection element 6 is a5 = 44.8 mm.

The case where the specific position C4 is shifted from the middle of the adjustment mirrors 4a and 4b to the adjustment mirror 4b side on the resonator 14 side is as follows. The distance of each part is set as follows.
Distance from lens 5 to light receiving surface of light detecting element 6 a5 = 57.7 mm
Distance from mirror 4a to C4 p1 = 100mm
Distance from mirror 4b to C4 p2 = -40mm
When the above settings are made and the distances and optical path lengths of the other components are the same as in the above example, the beam diameter at the specific position C4 is 0.39 mm, and the magnification k at which the position C4 forms an image on the light receiving surface is −0.28. Therefore, the beam diameter on the light receiving surface of the photodetecting element 6 is 0.11 mm. At this time, similarly to the above example, the adjustment mirror 4a on the light source 1 side is 0.5 ° clockwise in the plane of FIG. 8, and the adjustment mirror 4b on the resonator 14 side is counterclockwise in the plane of FIG. When tilted around 0.5 °, the amount of movement of the laser beam is 0.10 mm according to the above equation (3), and the same as in the above example, that is, when the specific position C4 is arranged between the adjustment mirrors 4a and 4b. The laser beam stays within the light receiving surface of the light detecting element 6.

On the other hand, the case where the specific position C4 is moved to the other adjustment mirror 4a side will be described. In this example, the distance of each part is set as follows.
Distance from lens 5 to light receiving surface of light detecting element 6 a5 = 54.3 mm
Distance from mirror 4a to C4 p1 = 40mm
Distance from mirror 4b to C4 p2 = -100mm
When the above settings are made and the distances and optical path lengths of the other components are the same as in the above example, the diameter of the laser beam at the specific position C4 is 0.47 mm, and the magnification k at which the position C4 forms an image on the light receiving surface is −0. .20, the diameter of the laser beam on the light receiving surface of the light detecting element 6 is 0.09 mm. Similar to the above example, the adjustment mirror 4a on the light source 1 side is 0.5 ° clockwise in the plane of FIG. 8, and the adjustment mirror 4b on the resonator 14 side is 0.5 counterclockwise in the plane of the paper. When tilted, the amount of movement of the laser beam is 0.56 mm according to the above equation (3), and similarly, the laser beam stays within the light receiving surface of the light detection element 6.
Therefore, from these results, the specific position is set to a range of about a quarter of the distance between them from the intermediate position between the adjustment mirrors 4a and 4b. The movement of the laser beam within the light receiving surface can be sufficiently suppressed, and the mode matching adjustment can be performed without moving the position of the light detection element 6.

[2] Second Embodiment In this example, the laser light source 1 and the optical lenses 2 and 5 are changed as shown in FIG. As the laser light source 1, a continuous wave laser having a wavelength of 532 nm, M ² = 1, and a beam waist having a diameter of 1 mm at the exit is used. The optical lens 2 is a plano-convex lens having a convex surface facing the laser light source 1, and has a curvature radius of 249.35 mm, a thickness of 2.5 mm, a material BK7 (trade name, manufactured by Schott), and a focal length of 480 mm. The external resonator 14 has a function of mode matching the laser light from the laser light source 1. The optical lens 5 is a plano-convex lens having a convex surface facing the input coupling element 9, and has a curvature radius of 34.1 mm, a thickness of 2.5 mm, a material BK7 (trade name, manufactured by Schott Co., Ltd.), and a focal length of 65.6 mm. And has a function of condensing the laser beam on the light receiving surface of the light detecting element 6. The size of the light receiving surface of the photodetecting element 6 is 2 mm in diameter.
The other configurations, in particular, the materials, configurations, and dimensions of the mirrors 9, 10, 11a, and 11b and the nonlinear optical crystal 12 that constitute the external resonator 14 are the same as those in the first embodiment.
That is, the input coupling element 9 is flat on both sides, the material is synthetic quartz, and the thickness is 3 mm. The mirror 10 is a plane mirror, and the mirrors 11a and 11b are concave mirrors having a curvature radius of 125 mm. The incident angles to the input coupling element 9 and the mirrors 10, 11a and 11b are set to 10 °, respectively. Further, a BBO (β-BaB ₂ O ₄ ) crystal having a thickness of 4 mm, for example, is disposed between the mirrors 11 a and 11 b as the nonlinear optical crystal 12.
Here, the distance and optical path length of each part are set as follows.

Distance from the exit of the laser light source 1 to the lens 2 a1 = 480 mm
Distance from lens 2 to adjustment mirror 4a a2 = 200mm
Distance from mirror 4b to resonator side surface of input coupling element 9 a3 = 74 mm
Distance from the resonator-side surface of the input coupling element 9 to the lens 5 a4 = 100 mm
Distance from lens 5 to light receiving surface of light detecting element 6 a5 = 88.2 mm
Distance from mirror 4a to C4 p1 = 70mm
Distance from mirror 4b to C4 p2 = -70mm
Optical path length between input coupling element 9 and mirror 10 w1 = 132 mm
Optical path length between mirror 10 and mirror 11a w2 = 150 mm
Optical path length between mirrors 11a and 11b w3 = 150mm
Optical path length between the mirror 11b and the input coupling element 9 w4 = 150 mm

In this case, the diameter of the laser beam at the specific position C4 is 0.54 mm, and the magnification k at which C4 forms an image on the light receiving surface of the light detecting element 6 is −0.37. The beam diameter is 0.2 mm.
In the second embodiment, the amount of movement of the laser beam on the light receiving surface of the light detecting element 6 when the mode matching is adjusted using the adjusting mirrors 4a and 4b is calculated. When the adjustment mirror 4a is tilted 0.5 ° clockwise in the plane of FIG. 8 and the adjustment mirror 4b is tilted 0.5 ° counterclockwise in the plane of FIG. The moving amount D of the beam is 0.45 mm. If the laser beam is positioned at the center of the light receiving surface of the light detecting element 6 before the adjustment is started, the laser beam stays within the light receiving surface of the light detecting element 6 even by the adjustment. Therefore, it can be seen that it is not necessary to change the position of the light detection element 6 and that the optical axis can be easily adjusted.

  If the light receiving surface of the light detection element 6 is arranged at the rear focal position of the optical lens 5 without using the configuration of the present invention, the amount of movement is 2.3 mm according to the above equation (1), and light detection is performed. The position of the laser beam deviates from the light receiving surface of the element 6. At this time, the distance from the lens 5 to the light detection element 6 is a5 = 65 mm.

[3] Third Embodiment FIG. 9 shows a schematic configuration diagram of an example of a laser apparatus according to a third embodiment of the present invention. In FIG. 9, parts corresponding to those in FIG. In this example, an example in which the optical lens 2 is disposed between the adjustment mirror 4 b and the input coupling element 9 of the external resonator 14 is shown. In this example, the laser light source 1 is a continuous wave laser having a wavelength 532 nm, M ² = 1, and a beam waist having a diameter of 1 mm at the exit. The optical lens 2 is a plano-convex lens having a convex surface facing the adjustment mirror 4b, and has a curvature radius of 249.35 mm, a thickness of 2.5 mm, a material BK7 (trade name, manufactured by Schott Corp.), and a focal length of 118. 5 mm, and has a function of mode-matching the laser light from the light source 1 to the input coupling element 9 of the external resonator 14 and the external resonator 14 described later. The input coupling element 9 is a semi-transparent mirror in which a semi-transmissive film is formed on the external resonator 9 side, as in the first and second embodiments described above. The optical lens 5 is a plano-convex lens having a convex surface facing the input coupling element 9, and has a curvature radius of 34.1 mm, a thickness of 2.5 mm, a material BK7 (trade name, manufactured by Schott Co.), and a focal length of 108.2 mm. And has the effect of condensing on the light detecting element 6. The light detection element 6 is a photodiode having a light receiving surface with a diameter of 2 mm. Here, C5 is a specific position that is conjugated with the light receiving surface of the light detection element 6 by the optical lens 2 and reflection by the semi-transparent surface of the input coupling element 9.

The material configuration of the mirrors 10, 11a and 11b of the external resonator 14, the material and dimensions of the nonlinear optical crystal 12 are the same as those in the first and second embodiments described above.
That is, the input coupling element 9 is flat on both sides, the material is synthetic quartz, and the thickness is 3 mm. The mirror 10 is a plane mirror, and the mirrors 11a and 11b are concave mirrors having a curvature radius of 125 mm. The incident angles to the input coupling element 9 and the mirrors 10, 11a and 11b are set to 10 °, respectively. Further, a BBO (β-BaB ₂ O ₄ ) crystal having a thickness of 4 mm, for example, is disposed between the mirrors 11 a and 11 b as the nonlinear optical crystal 12.
Here, the distance and optical path length of each part are set as follows.

Distance from the exit of the laser light source 1 to the lens 2 b1 = 330 mm
Distance from mirror 4b to optical lens 2 b2 = 50mm
Distance from lens 2 to resonator side surface of input coupling element 9 b3 = 66.3 mm
Distance from the resonator-side surface of the input coupling element 9 to the lens 5 b4 = 141 mm
Distance from lens 5 to light receiving surface of light detecting element 6 b5 = 88.2 mm
Distance from mirror 4a to C5 p1 = 60mm
Distance from mirror 4b to C5 p2 = -60mm
Optical path length between input coupling element 9 and mirror 10 w1 = 150 mm
Optical path length between mirror 10 and mirror 11a w2 = 150 mm
Optical path length between mirrors 11a and 11b w3 = 132mm
Optical path length between the mirror 11b and the input coupling element 9 w4 = 150 mm

The input coupling element 9 has a focal length of −271.3 mm for the light transmitted from the optical lens 2 side to the mirror 10 side, and the light reflected from the optical lens 2 side to the optical lens 5 side. Acts as a lens with a focal length of -42.8 mm.
Since the diameter of the laser beam at the specific position C5 is 1.02 mm and the magnification k at which the position C5 forms an image on the light receiving surface of the light detecting element 6 is −0.49, the beam diameter on the light receiving surface of the light detecting element 6 is 0.5 mm.
In the third embodiment, the amount of movement of the laser beam on the light receiving surface of the light detection element 6 when the mode matching adjustment is performed using the adjustment mirrors 4a and 4b is calculated. When the adjustment mirror 4a is tilted 0.5 ° clockwise in the plane of FIG. 9 and the adjustment mirror 4b is tilted 0.5 ° counterclockwise in the plane of FIG. 9, the laser beam is expressed by the above equation (3). The amount of movement is 0.51 mm. If the beam is positioned at the center of the light receiving surface of the light detection element 9 before the adjustment is started, the beam stays within the light receiving surface even after adjustment.

  On the other hand, when the laser beam movement amount in the case where the light receiving surface of the light detection element 6 is arranged at the focal position of the optical lens 5 without using the configuration of the present invention, it is 3.8 mm according to the above equation (1). The light detection element 6 is detached from the light receiving surface. At this time, the distance between the optical lens 5 and the light receiving surface of the light detection element 6 is b5 = 106.2 mm.

[4] Fourth Embodiment FIG. 10 shows a schematic configuration diagram of a laser apparatus according to a fourth embodiment of the present invention. In this example, a case where two sets of wedge plate units each made up of two wedge plates are used as the optical axis adjuster is shown. 10, parts corresponding to those in FIG. 6 are given the same reference numerals, and redundant description is omitted.
In this example, a continuous wave laser having a beam waist having a wavelength of 532 nm, M ² = 1, and a diameter of 1 mm at the exit is used as the laser light source 1. The optical lens 2 disposed between the light source 1 and the wedge plate unit 22 is a plano-convex lens having a convex surface directed toward the laser light source 1, and has a radius of curvature of 249.35 mm, a thickness of 2.5 mm, and a material BK7 (Schott ( The product has a focal length of 480 mm, and has an effect of mode matching the laser light from the laser light source 1 to the external resonator 14. The input coupling element 9 of the external resonator 14 is configured by a semi-transparent mirror in which a semi-transmissive film is formed on the surface on the resonator 14 side. The optical lens 5 disposed between the input coupling element 9 and the light detection element 6 is a plano-convex lens having a convex surface facing the input coupling element 9 side. The optical lens 5 has a curvature radius of 34.1 mm, a thickness of 2.5 mm, a material BK7 (trade name, manufactured by Schott Co., Ltd.), and a focal length of 65.6 mm, and condenses laser light on the light detection element 6. Has an effect. The light detection element 6 is a photodiode, and the size of the light receiving surface is 2 mm in diameter. C6 indicates a specific position conjugate with the light receiving surface of the light detection element 6 by the optical lens 5.

The material configuration of the mirrors 10, 11a and 11b of the external resonator 14, the material and dimensions of the nonlinear optical crystal 12 are the same as those in the first and second embodiments described above.
That is, the input coupling element 9 is flat on both sides, the material is synthetic quartz, and the thickness is 3 mm. The mirror 10 is a plane mirror, and the mirrors 11a and 11b are concave mirrors having a curvature radius of 125 mm. The incident angles to the input coupling element 9 and the mirrors 10, 11a and 11b are set to 10 °, respectively. Further, a BBO (β-BaB ₂ O ₄ ) crystal having a thickness of 4 mm, for example, is disposed between the mirrors 11 a and 11 b as the nonlinear optical crystal 12.
Here, the distance and optical path length of each part are set as follows.

Distance from the exit of the laser light source 1 to the lens 2 c1 = 480 mm
Distance from lens 2 to wedge plate unit 22 c2 = 200 mm
Distance from wedge plate unit 23 to resonator side surface of input coupling element 9
c3 = 74mm
Distance from the resonator-side surface of the input coupling element 9 to the lens 5 c4 = 100 mm
Distance from lens 5 to light receiving surface of light detecting element 6 c5 = 88.2 mm
Distance from wedge plate unit 22 to C6 p3 = 70mm
Distance from wedge plate unit 23 to C6 p4 = -70mm
Optical path length between input coupling element 9 and mirror 10 w1 = 132 mm
Optical path length between mirror 10 and mirror 11a w2 = 150 mm
Optical path length between mirrors 11a and 11b w3 = 150mm
Optical path length between the mirror 11b and the input coupling element 9 w4 = 150 mm

In this case, the diameter of the laser beam at the specific position C6 is 0.54 mm, and the magnification k at which the position C6 forms an image on the light receiving surface of the light detecting element 6 is −0.37. The laser beam diameter is 0.2 mm.
In the fourth embodiment, the movement amount of the laser beam on the light receiving surface of the light detecting element 6 when the mode match adjustment is performed using the wedge plate units 22 and 23 is calculated. When the wedge plate unit 22 tilts the optical axis by 1 ° clockwise in the plane of FIG. 10 and the wedge plate unit 23 tilts the optical axis by 1 ° counterclockwise in the plane of FIG. 0.45 mm. If the laser beam is positioned at the center of the light receiving surface of the light detecting element 6 before the adjustment is started, the laser beam stays within the light receiving surface of the light detecting element 6 even by the adjustment. Therefore, it is not necessary to move the position of the light detection element 6 when adjusting the optical axis, and the optical axis adjustment work can be simplified.

  On the other hand, when the light receiving surface of the light detecting element 6 is arranged at the rear focal position of the optical lens 5 without using the configuration of the present invention, the amount of movement is 2.3 mm, and the light receiving surface of the light detecting element 6 is obtained. It will come off. At this time, the distance c5 between the optical lens 5 and the light detection element 6 is 65 mm.

[5] Fifth Embodiment FIG. 11 is a schematic configuration diagram of a laser apparatus according to a fifth embodiment of the present invention. In this example, an example in which a collimator lens and a collimator lens unit in which the collimator lens can be rotated and adjusted by a tilt rotation mechanism and a parallel movement mechanism are shown as an optical axis adjustment tool. In FIG. 11, parts corresponding to those in FIG.
In this example, a continuous wave laser having a wavelength of 532 nm is used as the light source 1. The laser light is transmitted by a single mode optical fiber 32 having a core diameter of 3.5 μm. The optical coupling element 33 at the fiber exit end is fixed to the light input end of the collimator unit 35. The collimator lens 34 is a plano-convex lens having a flat surface on the emission end side of the fiber 33 and a convex surface on the resonator 14 side, a curvature radius of 1.56 mm, a thickness of 1 mm, and a material BK7 (trade name, manufactured by Schott Co., Ltd.). The focal length is 3 mm, and the external resonator 14 has a function of mode matching the laser light from the light source 1. The input coupling element 9 is a semi-transparent mirror having a semi-transmissive film formed on the surface on the resonator 14 side. The optical lens 5 is a plano-convex lens having a convex surface facing the input coupling element 9, and has a curvature radius of 34.1 mm, a thickness of 2.5 mm, a material BK7 (trade name, manufactured by Schott Co., Ltd.), and a focal length of 65.6 mm. And has the effect of condensing on the light detecting element 6. The light detection element 6 is a photodiode, and the size of the light receiving surface is 2 mm in diameter. C7 is a specific position conjugate with the light receiving surface of the light detecting element 6 by the optical lens 5, and is positioned at the apex of the convex surface of the collimator lens 34. The collimator unit 35 includes a horizontal and vertical tilt rotation mechanism with the specific position C7 as the rotation center, and a horizontal and vertical translation mechanism in a plane perpendicular to the optical axis. CM2, CM3, and CM4 are total reflection mirrors, and together with CM1, constitute an optical resonator.

The material configuration of the mirrors 10, 11a and 11b of the external resonator 14, the material and dimensions of the nonlinear optical crystal 12 are the same as those in the first and second embodiments described above.
That is, the input coupling element 9 is flat on both sides, the material is synthetic quartz, and the thickness is 3 mm. The mirror 10 is a plane mirror, and the mirrors 11a and 11b are concave mirrors having a curvature radius of 125 mm. The incident angles to the input coupling element 9 and the mirrors 10, 11a and 11b are set to 10 °, respectively. Further, a BBO (β-BaB ₂ O ₄ ) crystal having a thickness of 4 mm, for example, is disposed between the mirrors 11 a and 11 b as the nonlinear optical crystal 12.

Here, the distance and optical path length of each part are set as follows.
Distance from fiber 32 exit end to lens 34 d1 = 2.4 mm
Distance from the lens 34 to the resonator side surface of the input coupling element 9 d2 = 167 mm
Distance from the resonator side surface of the input coupling element 9 to the lens 5 d3 = 77 mm
Distance from lens 5 to light receiving surface of light detecting element 6 d4 = 88.2 mm
Optical path length between input coupling element 9 and mirror 10 w1 = 132 mm
Optical path length between mirror 10 and mirror 11a w2 = 150 mm
Optical path length between mirrors 11a and 11b w3 = 150mm
Optical path length between the mirror 11b and the input coupling element 9 w4 = 150 mm

Since the diameter of the laser beam at the specific position C7 is 0.58 mm and the magnification k at which the position C7 forms an image on the light receiving surface of the light detecting element 6 is −0.37, the laser beam diameter on the light receiving surface of the light detecting element 6 is Is 0.21 mm.
In the fifth embodiment, when the mode matching adjustment to the external resonator 14 is performed by the tilt adjustment of the collimator unit 35, the center of rotation of the collimator unit 35 coincides with the point C7 that is conjugate with the light receiving surface of the light detecting element 6. Therefore, the laser beam does not move on the light receiving surface of the light detecting element 6.

  On the other hand, when the light receiving surface of the light detecting element 6 is arranged at the rear focal position of the optical lens 5 without using the configuration of the present invention, the tilt rotation mechanism of the collimator lens unit 35 causes the laser beam to be 0.9 ° or more. When the deflection is performed, the laser beam is deviated from the light receiving surface of the light detecting element 6. At this time, the distance between the optical lens 5 and the light detection element 6 is d4 = 65 mm.

As described above, according to the present invention, it is not necessary to change the position of the light detection element during the optical axis adjustment operation of the laser apparatus, and the optical axis adjustment can be performed with an extremely simple operation.
In particular, in a laser device having an external resonator that performs wavelength conversion from a wavelength of 1300 nm to a wavelength of 650 nm, which has been very difficult to adjust in the past, a photodiode such as InGaAs that can be applied to the wavelength band is used as a light detection element. In addition, even if the area of the light receiving surface is as small as about 1 mm in diameter, the optical axis can be adjusted without changing the position of the photodetecting element as described above. It is possible to greatly simplify the axis adjustment work.
On the other hand, since the amount of movement of the light spot on the light receiving surface of the light detecting element is reduced, it is possible to use light detection with a smaller light receiving area compared to the conventional laser device. Since the photodiode is generally cheaper as the light receiving area is smaller, a cheaper photodetecting element can be used, which is effective for cost reduction.
Also, by adopting the configuration of the present invention in a laser device used in a semiconductor manufacturing process, it is possible to simplify assembly adjustment and repair maintenance work. For this reason, it is possible to shorten the stop period of the manufacturing apparatus in the semiconductor factory, and to avoid an adverse effect on the cost of semiconductor manufacturing.

  The present invention is not limited to the examples shown in FIGS. 1 to 11 described above, and various materials, dimensions, arrangements, functions, and the like of the respective optical components can be used without departing from the configuration of the present invention. Needless to say, modifications and changes are possible. Also, in a laser apparatus using a pulse laser light source, the optical axis adjustment work can be simplified by applying the present invention to, for example, adjusting a mirror by rotating a mirror when receiving a pulse laser beam by a photodiode. Can be achieved.

It is a schematic block diagram with which it uses for description of the optical axis adjustment of a laser apparatus. 1 is a schematic configuration diagram of a laser apparatus according to an embodiment of the present invention. It is a section lineblock diagram of a wedge board. A and B are schematic cross-sectional configuration diagrams for explaining the optical axis deflection by the wedge plate unit. A to E are schematic cross-sectional configuration diagrams for explaining the optical axis deflection by the wedge plate unit. 1 is a schematic configuration diagram of a laser apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of a laser apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of a laser apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of a laser apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of a laser apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram of a laser apparatus according to an embodiment of the present invention. It is a schematic block diagram of an example of the conventional laser apparatus. FIGS. 8A to 8C are diagrams illustrating an example of a change in output during an optical axis adjustment operation in the laser apparatus. FIGS. 8A to 8C are diagrams illustrating an example of a change in output during an optical axis adjustment operation in the laser apparatus. It is a figure which shows the relationship between the light-receiving area and cutoff frequency in a silicon photodiode and an InGaAs photodiode.

Explanation of symbols

  1. 3. laser light source; Optical axis adjuster, 4a, 4b. 4. Adjustment mirror, Optical lens, 6; 8. a light detection element; Input coupling element, 10. Mirror, 11a, 11b. Mirror, 12. Nonlinear optical crystal, 14. External resonator, 21. Wedge plates, 22a, 22b, 23a, 23b. Wedge plate, 22, 23. Wedge plate unit, 32. Optical fiber, 33. Optical coupling element, 34. Collimator lens, 35. Collimator lens unit

Claims (11)

In order to align the optical axis of the laser light from the laser light source with the external resonator based on a laser light source, an external resonator having an input coupling element, a light detection element, and a light output detected by the light detection element With an optical axis adjuster,
A specific position between the optical axis adjuster arranged on the light source side and the input coupling element of the external resonator, and a light receiving surface of the photodetecting element are arranged in a geometric optical conjugate relationship. A laser device characterized by the above.   The laser apparatus according to claim 1, wherein the optical axis adjuster is a pair of mirrors.   The laser device according to claim 2, wherein the specific position is provided between the pair of mirrors.   4. The laser device according to claim 3, wherein the specific position is arranged within a range of a quarter of a distance between the mirrors from an intermediate position between the pair of mirrors.   2. The laser device according to claim 1, wherein the optical axis adjuster is provided with one or more sets of wedge plate units including a pair of wedge plates. Two sets of the wedge plate units are provided,
6. The laser device according to claim 5, wherein the specific position is provided between the two sets of wedge plate units. The optical axis adjuster is a collimator lens;
2. The laser device according to claim 1, wherein the collimator lens includes a tilt rotation mechanism and a parallel movement mechanism.   The laser device according to claim 7, wherein the specific position is a rotation center of the tilt rotation mechanism of the collimator lens.   The laser apparatus according to claim 7, wherein an optical fiber is disposed between the laser light source and the collimator lens.   2. The laser device according to claim 1, wherein a nonlinear optical crystal is disposed in the external resonator.   The laser device according to claim 1, wherein the laser light source is a laser light source that oscillates a continuous wave.

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