JPH07263785A - Etalon, single longitudinal mode laser and manufacture of etalon - Google Patents

Abstract

PURPOSE:To acquire a single longitudinal mode laser which is free from problems such as rise of oscillation threshold value and output deterioration caused thereby and which does not cause strain of beam profile. CONSTITUTION:Etalon 15 whose longitudinal mode coincides with a gain peak wavelength of an Nd:YAG crystal 13 is inserted into a resonator constituted of an edge face 13a of the Nd:YAG crystal 13 which is a solid laser medium and a resonator mirror 14 making two mutually parallel light transmission edge faces 15a, 15b form a specified angle to a resonator axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser, and more particularly to a laser in which an etalon is arranged in a laser resonator to make an oscillation mode a single longitudinal mode.

The present invention also relates to the above etalon and a method for producing the same.

[0003]

2. Description of the Related Art As disclosed in, for example, Japanese Patent Laid-Open No. 62-189783, there is known a solid-state laser in which a solid-state laser rod doped with a rare earth element such as neodymium is pumped by a semiconductor laser (laser diode) or the like. .

In this type of solid-state laser and the like, for example, Optics Letters Vol.
As described in (1993) p.420, in order to suppress the generation of mode-competitive noise, an etalon is placed in the resonator to select the wavelength and make the oscillation mode a single longitudinal mode. Has been.

[0005]

However, in the conventional laser for achieving the single longitudinal mode by using the etalon as described above, the threshold of pumping power for the laser to oscillate remarkably increases, and as a result, However, problems such as a decrease in laser output may occur. This threshold rise is because the etalon longitudinal mode interval is set to the above oscillation in order to avoid that multiple etalon longitudinal modes exist within the lasing wavelength range of the laser medium and it becomes impossible to make a single longitudinal mode. This is due to the setting being sufficiently large with respect to the possible wavelength width.

That is, in such a structure, generally, unless the etalon thickness is controlled on the order of submicrons, the etalon longitudinal mode and the gain peak wavelength of the laser medium do not coincide with each other. And the gain is not used effectively, which raises the oscillation threshold.

It is not practical to control the etalon thickness on the order of submicrons by polishing, because it is extremely difficult, and even if possible, it requires a huge cost. Therefore, conventionally, an attempt has been made to adjust the optical path length of the etalon by adjusting the inclination of the etalon inserted in the resonator with respect to the resonator axis so that the etalon longitudinal mode and the gain peak wavelength of the laser medium match.

However, when the inclination of the etalon becomes too large, the insertion loss of the etalon increases, which again raises the oscillation threshold value and the accompanying problems such as output reduction. On the contrary, when the inclination of the etalon becomes too small, although the output is produced, there arises a problem that the single longitudinal mode property is deteriorated. Also, especially when mass-producing laser devices,
Since it is necessary to adjust the angle of the etalon for each unit, there is a problem that productivity is reduced and specifications such as an oscillation threshold and output are different for each unit. Furthermore, when it is necessary to tilt the etalon largely for adjusting the optical path length, by tilting the etalon in that way,
There is also a problem that the profile of the oscillation beam is distorted.

The present invention has been made in view of the above circumstances, and has problems such as an increase in the oscillation threshold value and a decrease in output accompanying it, a problem of beam profile distortion, and a single longitudinal mode property. It is intended to provide a single longitudinal mode laser without deterioration problem.

It is another object of the present invention to provide an etalon for realizing the above-described single longitudinal mode laser, and a method for manufacturing the etalon relatively easily and at low cost. .

[0011]

An etalon according to the present invention comprises two parallel etalons arranged in a resonator of a laser device for converting a laser beam into a single longitudinal mode as described in claim 1. It is characterized in that the longitudinal mode thereof coincides with the gain peak wavelength of the laser medium when the laser beam is incident on the light passage end face at a predetermined angle.

On the other hand, the single longitudinal mode laser according to the present invention uses the etalon having the above-mentioned structure. That is, as described in claim 2, the etalon has two light passing end faces which are parallel to each other and which are the resonator axes. Is arranged in the resonator in a state of forming a predetermined angle with respect to.

In the single longitudinal mode laser according to the present invention, preferably, as described in claim 3, the etalon is arranged such that two light passing end faces parallel to each other are substantially perpendicular to the cavity axis. It is arranged in the resonator.

The first etalon manufacturing method according to the present invention for obtaining the above etalon is, as described in claim 4, a etalon substrate having a larger area than the desired etalon, from one surface side thereof, Interference fringes formed by irradiating a single longitudinal mode laser beam having a wavelength equal to the gain peak wavelength of the laser medium of the laser device in which the etalon is arranged, and the single longitudinal mode laser beam passing through the etalon substrate at that time. Is observed, and the substrate portion on which a portion having a predetermined brightness is formed in this interference fringe is subdivided into etalons.

A second method for producing an etalon according to the present invention for obtaining the etalon is that an etalon substrate having a larger area than a desired etalon is arranged on the etalon, as described in claim 5. The laser device for evaluation having the same laser medium as that of the laser device for evaluation is inserted into the resonator, and the etalon substrate is two-dimensionally scanned by the laser beam for evaluation emitted from the laser device for evaluation.
At that time, the oscillation wavelength of the laser beam transmitted through the etalon substrate is measured, and a map showing the oscillation wavelength is created at each position of the etalon substrate. The map shows that the oscillation wavelength is the gain peak wavelength of the laser medium. It is characterized in that the etalon substrate portion which is equal to is divided into etalons.

According to a third etalon manufacturing method of the present invention for obtaining the above etalon, as described in claim 6, an etalon substrate having a larger area than the desired etalon is subdivided to form a plurality of strips. Then, these strips are sequentially inserted into the resonator of the evaluation laser device equipped with the same laser medium as the laser device in which the etalon is arranged,
The lasing wavelength of the laser beam in that case is measured for each strip, and the strip whose oscillation wavelength is equal to the gain peak wavelength of the laser medium of the laser device is selected and used as the etalon. It is what

[0017]

The large-area etalon substrate used in the first, second, and third etalon manufacturing methods has two surfaces (surfaces that become light passage end surfaces when made into etalons) that are completely parallel to each other. It is almost impossible to polish it to the following condition. In other words, this etalon substrate always has a thickness distribution, and when it is subdivided into etalons, the etalon longitudinal mode usually has a specific thickness such that the etalon longitudinal mode is equal to the gain peak wavelength of the laser medium. Also includes.

The etalon substrate portion having such a specific thickness can be specified as a portion (that is, a bright portion or a dark portion) where the interference fringe has a predetermined brightness in the first etalon manufacturing method. Therefore, in the first method, if the substrate portion in which the interference fringes have a predetermined brightness is subdivided into an etalon, the etalon has a longitudinal mode that matches the gain peak wavelength of the laser medium. .

In the second etalon manufacturing method,
When the evaluation laser beam passes through the etalon substrate portion having the above-described specific thickness, its oscillation wavelength becomes equal to the gain peak wavelength of the laser medium. Therefore,
In the second method, if the etalon substrate portion whose oscillation wavelength is equal to the gain peak wavelength of the laser medium when the evaluation laser beam is transmitted is subdivided into etalons, the etalon has a longitudinal mode of the laser medium. It becomes the same as the gain peak wavelength of.

Further, if the etalon substrate has a portion having a specific thickness as described above, the plurality of strips obtained from the substrate in the third etalon manufacturing method will have this specific thickness. Those that are included will be included. Therefore, if the etalon is selected from a plurality of strips that have an oscillation wavelength equal to the gain peak wavelength of the laser medium when the laser beam for evaluation is transmitted, the etalon has a longitudinal mode of the laser medium. It becomes the same as the gain peak wavelength of.

As described above, the first to third etalon manufacturing methods according to the present invention do not strictly polish an etalon to a predetermined thickness and finish the etalon. In order to obtain a desired etalon by utilizing a portion of such a substrate having a specific thickness, the following is taken into consideration according to each of these methods.
An etalon whose longitudinal mode is equal to the gain peak wavelength of the laser medium can be manufactured relatively easily and at low cost.

On the other hand, in the single longitudinal mode laser of the present invention having the above structure, since the etalon longitudinal mode and the gain peak wavelength of the laser medium coincide with each other, the gain can be effectively utilized and therefore the oscillation threshold value Is low, and it is possible to prevent a problem such as a decrease in output due to an increase in oscillation threshold.

Further, since the single longitudinal mode laser according to the present invention does not need to adjust the inclination of the etalon for adjusting the optical path length, the insertion loss of the etalon can be suppressed to be low and high efficiency can be realized. The problem that the profile of the oscillation beam is distorted can be prevented, and the single longitudinal mode property is also improved. Further, the means for adjusting the etalon for adjusting the optical path length is not required, and the effect of cost reduction can be obtained.

In the single longitudinal mode laser according to the present invention, the etalon is arranged such that the two light passing end faces parallel to each other form a predetermined angle with respect to the cavity axis. A suitable angle is, for example, about 90 ° ± 30 '.

The first to third etalon manufacturing methods according to the present invention can be applied to the case of manufacturing an etalon arranged so as to be inclined by a predetermined angle. That is, in the first etalon manufacturing method, when the etalon substrate is irradiated with the single longitudinal mode laser beam, the etalon substrate may be tilted by the predetermined angle with respect to the incident direction of the laser beam. In the second etalon manufacturing method, the etalon substrate may be tilted by the predetermined angle with respect to the resonator axis of the evaluation laser device. Further, in the third etalon manufacturing method, the strip of the etalon substrate may be tilted by the predetermined angle with respect to the resonator axis of the evaluation laser device.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. FIG. 1 shows a laser diode pumped solid state laser according to a first embodiment of the present invention. This laser diode pumped solid-state laser is a semiconductor laser (phased array laser) 11 that emits a laser beam 10 as pumping light, and a condenser lens that focuses the laser beam 10 that is divergent light.
12, YAG crystal (hereinafter referred to as Nd: YAG crystal) 13 which is a solid-state laser medium doped with neodymium (Nd) 13, and is arranged in front of the Nd: YAG crystal 13 (right side in the figure). Resonator resonator 14 and an etalon 15 disposed between the resonator mirror 14 and the Nd: YAG crystal 13.
Consists of. The above elements are mounted and integrated in a common casing (not shown). Further, the phased array laser 11 is kept at a predetermined temperature by a Peltier element and a temperature control circuit (not shown).

As the phased array laser 11, a laser emitting a laser beam 10 having a wavelength of 809 nm is used. The Nd: YAG crystal 13 has an Nd concentration of 1 atm%.
The thickness is 1 mm. This Nd: YAG crystal
When the neodymium atom is excited by the incident laser beam 10, the laser beam 13 emits a laser beam 16 having a wavelength of 946.2 nm.

Here, both end faces 13a and 13b of the Nd: YAG crystal 13 and the light passing end faces 15a and 15b of the etalon 15 are used.
And the mirror surface 14a of the resonator mirror 14 and the light emitting end surface 14
The wavelengths of b mentioned above and the reflectance or transmittance of the Nd: YAG crystal 13 with respect to the other oscillation lines 1064 nm and 1300 nm are adjusted as shown in the table below by applying an appropriate coating. In this table, R is the reflectance and T is
Indicates the transmittance, and the unit of these numerical values is%.

13a 13b 15a 15b 14a 14b 809 nm T ≧ 85 R ≦ 2 − − − − 946.2 nm R ≧ 99.9 R ≦ 0.1 R = 15 R = 15 R ≧ 98 R ≦ 0.2 1064 nm T ≧ 30 R ≦ 10 − −T ≧ 30 R ≦ 10 1300 nm T ≧ 70 R ≦ 25 − − T ≧ 70 R ≦ 25 In the above configuration, both end surfaces 15a and 15b of the etalon 15 are arranged.
A standing wave with a wavelength of 946.2 nm is generated between
m laser beam 16 is the only Nd: YAG crystal end face 13a.
Strongly resonates between the mirror surface 14a and the mirror surface 14a, and a part thereof is emitted from the light emitting end surface 14b of the resonator mirror 14. It was confirmed that this laser beam 16 oscillated in a single longitudinal mode.

The etalon 15 is a parallel plate whose both end surfaces 15a and 15b are parallel to each other, and has both end surfaces 15a and 15b with respect to the axis of the resonator constituted by the Nd: YAG crystal end surface 13a and the mirror surface 14a. The normals are arranged at an angle of 30 '.

In this device, as shown in FIG. 2, the gain peak wavelength of the Nd: YAG crystal 13 which is the laser medium is 946.2 nm, and the full width at half maximum W of the 946 nm band is 0.8 nm. . On the other hand, F of Etalon 15
SR (Free Spectral Range) is N above
d: 0.8 to match full width at half maximum W of YAG crystal 13
nm, and one of the etalon longitudinal modes coincides with the gain peak wavelength of the Nd: YAG crystal 13 and is set to 946.2 nm.

In this device, since the etalon longitudinal mode and the gain peak wavelength of the Nd: YAG crystal 13 match each other in this way, the gain can be effectively used, and therefore the oscillation threshold value is low and the oscillation threshold value is low. It is possible to prevent problems such as output reduction due to value increase, and also to improve single longitudinal mode property. Further, since this device does not require a means for adjusting the inclination angle of the etalon 15 for adjusting the optical path length, it can be manufactured at a relatively low cost.

The FSR of the etalon 15 is changed to Nd: YAG.
It is not always necessary to match the full width at half maximum W of the crystal 13, but in order to prevent the oscillation of the etalon 15 in the second longitudinal mode (adjacent mode) more reliably, the FSR of the crystal is Nd: YAG crystal. It is preferable to set the gain full width at half maximum W of 13 or more.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 3, elements that are the same as the elements in FIG. 1 are given the same numbers, and duplicated description thereof is omitted (the same applies below).

The laser diode pumped solid-state laser of the second embodiment is basically different from the device of the first embodiment in that an optical wavelength conversion element 20 is arranged in the resonator. The light wavelength conversion element 20 is, for example, made of a bulk crystal of MgO-doped LiNbO ₃ having a periodic domain inversion structure. Even in this configuration, the action of the etalon 15 makes it possible to obtain a single longitudinal mode laser beam 16 having a wavelength of 946.2 nm. The laser beam 16 has a wavelength of 1/2, that is,
Converted to 473.1 nm blue second harmonic 21.

Here, both end surfaces 13a and 13b of the Nd: YAG crystal 13, both end surfaces 15a and 15b of the etalon 15, the mirror surface 14a of the resonator mirror 14 and the light emitting end surface 14b,
The reflectance or transmittance for each wavelength is adjusted as shown in the table below by applying an appropriate coating.
In this table, R indicates reflectance and T indicates transmittance, and the unit of these numerical values is%.

13a 13b 15a 15b 14a 14b 809 nm T ≧ 85 R ≦ 2 − − − − 946.2 nm R ≧ 99.9 R ≦ 0.1 R = 15 R = 15 R ≧ 99.9 R ≦ 0.2 1064 nm T ≧ 30 R ≦ 10 − − T ≧ 30 R ≦ 10 1300 nm T ≧ 70 R ≦ 25 − − T ≧ 70 R ≦ 25 473.1 nm R ≧ 98 R ≦ 10 R ≦ 1 R ≦ 1 T ≧ 93 R ≦ 0.3 Further, the optical wavelength conversion element 20 The reflectances of both end faces 20a, 20b of the are as follows. Laser beam with a wavelength of 946.2 nm in the above configuration
Reference numeral 16 hardly transmits the mirror surface 14a of the resonator mirror 14, while part of the second harmonic wave 21 having a wavelength of 473.1 nm passes through the mirror surface 14a and is emitted from the light emitting end surface 14b. It was confirmed that this second harmonic 21 is also a single longitudinal mode.

Also in the second embodiment, the etalon is used.
Since the longitudinal mode of 15 and the gain peak wavelength of the Nd: YAG crystal 13 coincide with each other, the same effect as in the first embodiment device described above can be obtained.

Next, a third embodiment of the present invention will be described with reference to FIG. The laser diode pumped solid-state laser according to the third embodiment is different from the device according to the second embodiment only in that the arrangement order of the optical wavelength conversion element 20 and the etalon 15 is changed, and the other configurations are the same as those of the second embodiment. It is basically similar to the apparatus of the embodiment.

Even in this configuration, the action of the etalon 15 causes the laser beam 16 of a single longitudinal mode with a wavelength of 946.2 nm to be emitted.
Is obtained. Then, the laser beam 16 is converted into a blue second harmonic wave 21 having a wavelength of 1/2, that is, 473.1 nm by the light wavelength conversion element 20. It was confirmed that this second harmonic 21 is also a single longitudinal mode.

Further, in this embodiment, as compared with the device of the second embodiment, since the optical wavelength conversion element 20 is arranged at a position where the beam diameter of the laser beam 16 is smaller, the wavelength conversion efficiency is further enhanced, A higher second harmonic output can be obtained.

Next, a method for producing the etalon 15 in which the gain peak wavelength of the Nd: YAG crystal 13 and the longitudinal mode match as described above will be described. FIG. 4 shows an example of an apparatus for producing the etalon 15 by applying the first etalon producing method of the present invention. In this device, a laser beam 31 of a single longitudinal mode is emitted from a solid-state laser 30 having a laser medium of Nd: YAG crystal as in the laser diode-pumped solid-state laser of FIGS. 1 and 3, and this laser beam 31 is a beam. Threaded through expander 32. The laser beam 31 whose beam diameter has been expanded by the beam expander 32 passes through the beam splitter 33 and is applied to the etalon substrate 5.

As an example, the etalon substrate 5 is made of fused silica having a refractive index of 1.45 and has a thickness of about 0.38 mm.
In this case, it is formed in a square with one side of 50 mm. The area of the etalon substrate 5 is sufficiently large as compared with the etalon 15 which is, for example, a 3 mm square.

Further, both surfaces 5a, 5 of the etalon substrate 5 are
b (the surface which becomes the light passing end faces 15a and 15b of the etalon 15) has a proper Finesse (strength of longitudinal mode selectivity) when it is later cut into the etalon 15.
A predetermined coating is applied in advance. This coating is for example an etalon applied to the laser device of FIG.
When 15 is manufactured, the reflectance R is 15% for the light of 946.2 nm as described above.

A part of the laser beam 31 applied to the etalon substrate 5 from the one surface 5a side is part of the surface 5a.
After being transmitted through the substrate 5, the rest is reflected on the surface 5b. The laser beam 31 thus reflected is reflected by the beam splitter 33 and is converged by the condenser lens 34. A two-dimensional photodetector 35 composed of a CCD image pickup device or the like is arranged at this convergence position, and the image formation state of the laser beam 31 is photographed by the two-dimensional photodetector 35. This photographed image is displayed on the display means 36 such as a CRT display device.
It is enlarged and reproduced in.

Although the etalon substrate 5 is polished to be a parallel plate, it is generally impossible to polish both surfaces 5a and 5b in parallel. That is, the etalon substrate 5 always has a thickness distribution.
Therefore, the laser beam 31 reflected by the surface 5a of the etalon substrate and the laser beam 31 reflected by the surface 5b are
The interference fringes cause interference fringes as shown in FIG. 5, for example. The image enlarged and reproduced on the display means 36 shows this interference fringe.

In this example, since the reflection type interferometer is constructed, when the etalon 15 is subdivided into the etalon 15, the etalon longitudinal mode has the gain peak wavelength 946.2 of the Nd: YAG crystal 13.
A portion of the etalon substrate 5 having a thickness equal to nm is a portion corresponding to the dark portion of the interference fringe.
Therefore, the substrate portion corresponding to the dark portion of the interference fringe is subdivided into an etalon 15, which is used as both ends 15a and 15b with respect to the resonator axis in the laser device of FIG. 1, FIG. 3 or FIG.
If the etalon 15 is arranged in a vertical direction, the longitudinal mode of the etalon 15 will match the gain peak wavelength of the Nd: YAG crystal 13.

On the other hand, when a transmission type interferometer is used, if the substrate portion corresponding to the bright part of the interference fringes is subdivided into etalons 15, the etalon 15 has a longitudinal mode of N.
It is the same as the gain peak wavelength of the d: YAG crystal 13.

According to this method, when the etalon substrate 5 is a 50 mm square and the etalon 15 is cut into a 3 mm square as described above, the longitudinal mode is Nd: YAG crystal.
10 etalons 15 at a time that match the gain peak wavelength of 13
It is possible to manufacture 0 or more sheets.

It should be noted that how to cut the etalon substrate 5 is determined in advance, and the cutting line (indicated by a one-dot chain line in FIG. 5) is superimposed on the interference image on the display means 36 by a method such as superimposing. If they are also displayed together, it becomes clear that, for example, the number of columns from the right and the number of cut pieces from the top can be used as the etalon 15 because they are in the dark part of the interference fringes, and the efficiency of the etalon production work is improved.

Next, another method for producing the etalon 15 in which the gain peak wavelength of the Nd: YAG crystal 13 and the longitudinal mode match will be described. FIG. 6 shows an example of an apparatus for producing the etalon 15 by applying the second etalon producing method of the present invention. In this apparatus, a semiconductor laser (phased array laser) 41 that emits a laser beam 40 as pumping light, a condenser lens 42 that focuses the laser beam 40 that is divergent light, and Nd: YAG
An evaluation laser device including a crystal 43 and a resonator mirror 44 is used.

The Nd: YAG crystal 43 is the Nd: YAG crystal 13 that constitutes the laser device shown in FIGS. 1, 3 and 10.
Similarly, the gain peak wavelength is 946.2 nm.
The resonator of this evaluation laser device is composed of the Nd: YAG crystal 43 and the resonator mirror 44, and the etalon substrate 5 similar to the one described above is arranged therein.

The etalon substrate 5 acts as an etalon in this evaluation laser device, whereby the laser beam 45 is made into a single longitudinal mode. This laser beam 45
Is condensed by the condenser lens 46, enters the inside of the optical fiber 47, propagates there, and is transmitted to the optical spectrum analyzer 48.
Be led to. The optical spectrum analyzer 48 measures the oscillation wavelength of the laser beam 45 and inputs the signal S1 indicating the measurement result to the computer 49.

This computer 49 has an etalon substrate 5
Drive control signal S to the two-dimensional movement stage 50 holding
Enter 2. The two-dimensional moving stage 50 is driven based on this drive control signal S2, and moves the etalon substrate 5 two-dimensionally with respect to the laser beam 45, that is, in the vertical direction in the figure and the direction perpendicular to the paper surface. Thereby, the etalon substrate 5 is two-dimensionally scanned by the laser beam 45.

Since the etalon substrate 5 has a thickness distribution as described above, its oscillation wavelength changes depending on the scanning position of the laser beam 45 on the etalon substrate 5. The computer 49 receives the signal S3 indicating the movement position (that is, the scanning position of the laser beam 45 on the etalon substrate 5) from the two-dimensional movement stage 50, and associates the signal S1 and the signal S3 input at that time with each other. , A map showing the oscillation wavelength of the laser beam 45 is created for each position on the etalon substrate 5.

This map is, for example, as shown in FIG. 7, and is displayed on the display means 51 such as a CRT display device. So if you look at this displayed map,
It is possible to know which part of the etalon substrate 5 is cut to form the etalon 15, and the longitudinal mode of the etalon coincides with the gain peak wavelength of the Nd: YAG crystal 13. For example, in the case of FIG. 7, the error of the etalon longitudinal mode is ±± with respect to the gain peak wavelength 946.2 nm of the Nd: YAG crystal 13.
If 0.2 nm is allowed, the etalon 15 may be obtained by cutting the shaded portion of the etalon substrate 5. The etalon 15 thus obtained also has an etalon longitudinal mode that matches the gain peak wavelength of the Nd: YAG crystal 13.

According to this method, when the etalon substrate 5 is a 50 mm square and the etalon 15 is cut into a 3 mm square as described above, the longitudinal mode is Nd: YAG crystal.
It is possible to fabricate more than 100 etalons 15 that match the gain peak wavelength of 13 (within an error of ± 0.2 nm) at one time.

Also in this method, how to cut the etalon substrate 5 is determined in advance, and the cutting line (shown by the one-dot chain line in FIG. 5) is superimposed on the map on the display means 51. From the table, it becomes clear that, for example, the cut piece from the top of the right column and the cut piece from the top can be used as the etalon 15, and the efficiency of the etalon production work is improved.

Next, another method for producing the etalon 15 in which the gain peak wavelength of the Nd: YAG crystal 13 and the longitudinal mode match will be described. FIG. 8 shows an example of an apparatus for producing the etalon 15 by applying the third etalon producing method of the present invention. This device is basically different from the device shown in FIG. 6 above in that a jig 60 holding a plurality of substrate strips 5P is arranged in place of the etalon substrate 5, and that the two-dimensional moving stage 50 has The difference is that a one-dimensional moving stage 61 is used instead.

The substrate strip 5P is obtained by cutting the etalon substrate 5 having a relatively large area as described above into an etalon size. As shown in the front view of FIG. Are held side by side in one row. And jig 60
Are held by the one-dimensional moving stage 61 in a direction in which the solid-state laser beam (laser beam for evaluation) 45 is incident on both surfaces of the held substrate strip 5P.

The substrate strip 5P acts as an etalon in this evaluation laser device, whereby the laser beam 45 is made into a single longitudinal mode. The oscillation wavelength of the laser beam 45 is measured by the optical spectrum analyzer 48 in the same manner as in the device of FIG. Then, the signal S1 output from the optical spectrum analyzer 48 and indicating the oscillation wavelength is input to the computer 49. The one-dimensional moving stage 61 is driven based on the drive control signal S2 output from the computer 49 to intermittently move the jig 60 in the vertical direction in the drawing at the same pitch as the mounting pitch of the board strips 5P.

By moving the jig 60 in this way,
The plurality of substrate strips 5P attached thereto are sequentially arranged in the resonator at positions where they are irradiated with the laser beam 45. Since the etalon substrate 5 has a thickness distribution as described above, a plurality of substrate strips 5P formed by cutting the etalon substrate 5 are formed.
Are not necessarily the same thickness. Therefore, the oscillation wavelength of the laser beam 45 changes according to the thickness of the substrate strip 5P arranged in the resonator.

The computer 49 is a one-dimensional moving stage
Every time 61 is moved by one pitch, that is, each substrate strip 5P is arranged at the position where the laser beam 45 is irradiated,
The oscillation wavelength of the laser beam 45 indicated by the signal S1 input at that time is the gain peak wavelength of the Nd: YAG crystal 13 946.
It is determined whether or not they match with 2 nm with a tolerance of ± 0.2 nm, for example. The determination result is displayed as a list on the display means 51. This list is, for example, "No. 1 = O
K No. 2 = OK No. 3 = NG ... ...... ”and the like, and are described in association with the order of arrangement in the resonator of each substrate strip 5P. Since this order corresponds to the order of arranging the board strips 5P in the jig 60, as shown in FIG.
Can be displayed at.

Therefore, if the substrate strip 5P with the number OK in the above list is selected and used as the etalon 15 and is used in the laser device of FIG. 1, FIG. 3 or FIG. The gain peak wavelength of the Nd: YAG crystal 13 is matched within an error of ± 0.2 nm.

According to this method, when the etalon substrate 5 is a 50 mm square and the etalon 15 is a 3 mm square as described above, the longitudinal mode is Nd: YAG crystal.
It is also possible to fabricate an etalon 15 having a gain peak wavelength of 13 (within an error of ± 0.2 nm) with a yield of about 50%.

It should be noted that, without using the one-dimensional movement stage 61 equipped with the drive source and the computer 49 as described above, each substrate strip 5P is laser beam 45 by manual operation.
May be sequentially arranged at a position where it is irradiated, and the oscillation wavelength of the laser beam 45 displayed by the optical spectrum analyzer 48 may be read each time to determine whether each substrate strip 5P can be used as the etalon 15. Absent.

[Brief description of drawings]

FIG. 1 is a side view showing a solid-state laser device according to a first embodiment of the present invention.

2 is a graph showing the relationship between the gain of the laser medium and the etalon longitudinal mode in the device of FIG.

FIG. 3 is a side view showing a solid-state laser device according to a second embodiment of the present invention.

FIG. 4 is a side view showing an example of an apparatus for carrying out the first etalon manufacturing method of the present invention.

5 is a schematic diagram showing the positional relationship between interference fringes and the etalon substrate that occur in the apparatus of FIG.

FIG. 6 is a side view showing an example of an apparatus for carrying out the second etalon manufacturing method of the present invention.

7 is a schematic diagram of a map showing the positional relationship between the oscillation wavelength of the evaluation laser beam and the etalon substrate in the apparatus of FIG.

FIG. 8 is a side view showing an example of an apparatus for carrying out a third etalon manufacturing method of the present invention.

9 is an enlarged front view of a part of the apparatus shown in FIG.

FIG. 10 is a side view showing a solid-state laser device according to a third embodiment of the present invention.

[Explanation of symbols]

 5 Etalon substrate 5P Etalon substrate strip 10 Laser beam (pumping light) 11,41 Semiconductor laser 12,34,42,46 Condensing lens 13,43 Nd: YAG crystal 14,44 Resonator mirror 15 Etalon 15a, 15b Light passing end face 16 Solid-state laser beam 20 Optical wavelength conversion element 21 Second harmonic wave 30 Solid-state laser 31 Single longitudinal mode laser beam 32 Beam expander 33 Beam splitter 35 Two-dimensional photodetector 36, 51 Display means 45 Evaluation laser beam 47 Optical fiber 48 Optical spectrum analyzer 49 Computer 50 Two-dimensional movement stage 60 Jig 61 One-dimensional movement stage

Claims (6)

[Claims] 1. An etalon arranged in a resonator of a laser device for converting a laser beam into a single longitudinal mode,
An etalon characterized in that the longitudinal mode thereof coincides with the gain peak wavelength of the laser medium in a state where the laser beam is incident on two light passing end faces which are parallel to each other at a predetermined angle. 2. An etalon having a gain peak wavelength of a laser medium and a longitudinal mode matched with each other is arranged in a resonator such that two parallel light passing end faces form a predetermined angle with respect to the resonator axis. A single longitudinal mode laser characterized in that 3. The single longitudinal mode laser according to claim 2, wherein the predetermined angle is approximately 90 °. 4. A method for producing an etalon arranged in a resonator of a laser device for converting a laser beam into a single longitudinal mode, wherein an etalon substrate having a larger area than a desired etalon is provided from one surface side thereof. Irradiation with a single longitudinal mode laser beam having a wavelength equal to the gain peak wavelength of the laser medium of the laser device, at that time, the interference fringes formed by the single longitudinal mode laser beam passing through the etalon substrate are observed. An etalon manufacturing method, characterized in that a substrate portion on which a portion having a predetermined brightness is formed is subdivided into etalons. 5. A method for producing an etalon arranged in a resonator of a laser device for converting a laser beam into a single longitudinal mode, wherein an etalon substrate having a larger area than a desired etalon is the same as the laser device. The etalon substrate is two-dimensionally scanned by the laser beam for evaluation, which is inserted into the resonator of the laser device for evaluation provided with the laser medium, and the oscillation of the laser beam transmitted through the etalon substrate at that time. The wavelength is measured, and a map showing the oscillation wavelength is created for each position of the etalon substrate. The map shows the portion of the etalon substrate where the oscillation wavelength is equal to the gain peak wavelength of the laser medium. A method for producing an etalon, which comprises producing an etalon. 6. A method for producing an etalon arranged in a resonator of a laser device for converting a laser beam into a single longitudinal mode, the etalon substrate having a larger area than a desired etalon is subdivided into a plurality of fine etalon substrates. Pieces are formed, and these strips are sequentially inserted into the resonator of the evaluation laser device equipped with the same laser medium as the laser device, and the oscillation wavelength of the laser beam in that case is measured for each strip. Then, a etalon manufacturing method is characterized in that a strip having an oscillation wavelength equal to a gain peak wavelength of a laser medium of the laser device is selected and used as an etalon.