JPH0894973A - Laser beam synthesizer - Google Patents

Abstract

PURPOSE: To facilitate the adjustment of the synthesis of many laser beams while obtaining high output by synthesizing these laser beams. CONSTITUTION: This laser beam synthesizer has a first laser beam source 1 for generating the laser beam which is longitudinally polarized light, a second laser beam source 2 which generates the laser beam which is transversely polarized light, an optical synthesizer 4 which synthesizes both laser beams by reflecting one of the laser beam of the longitudinally polarized light and the laser beam of the transversely polarized light and allows the transmission of the other and means (a first reflection mirror 3, a piezo element 8, a photodetector 6, a lock-in stabilizer 7) for controlling the optical path length between the first laser beam source 1 and the optical synthesizer 4 and the optical path length between the second laser beam source 2 and the optical synthesizer 4 so as to equalize these optical path lengths. The respective laser beams synthesized in this optical synthesizer 4 by this means are aligned in phases and are, therefore, outputtable as linearly polarized light and the further synthesis of the output laser beam is made possible. The higher output of the laser beam is thus obtd. by enabling the synthesis of the many laser beams.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam synthesizing device for synthesizing a plurality of laser beams to achieve high output.

[0002]

2. Description of the Related Art For example, microorganisms in seawater, such as plankton, are removed by irradiation with a high-power laser beam in order to remove deposits on the inner wall of a seawater supply pipe. For this, an output of about 100 W is required,
In addition, the wavelength needs to be in the green band to reduce laser absorption loss due to seawater. However, at present, green band lasers are limited to Ar lasers, copper vapor lasers, and solid green lasers, and it is difficult to obtain a high output of 100W. Therefore, it has been attempted to increase the output by synthesizing a green laser of about several tens W.

An example of such a laser synthesizing apparatus is disclosed in Japanese Patent Application Laid-Open No. 1-146748. This technique relates to a laser beam recording apparatus, as shown in FIG. 8, in which a laser beam emitted from a laser diode 51 is condensed by a condenser lens 52,
The light is adjusted to be vertically polarized by the wavelength plate 53 and is incident on the front surface of the polarization beam splitter 54. This polarization beam splitter 5
Since 4 transmits the vertically polarized light, the laser light goes straight.

On the other hand, the laser light emitted from the laser diode 55 is condensed by a condenser lens 56, adjusted to be laterally polarized by a half-wave plate 57, and incident on one side surface of the polarization beam splitter 54. . Polarization beam splitter 54
Reflects laterally polarized light, so that the laser beams overlap,
It is combined into a laser output.

However, in this technique, since the vertically polarized laser beam and the horizontally polarized laser beam in the polarization beam splitter 54 do not have the same frequency (wavelength) or phase, the laser beam obtained by synthesizing them is linearly polarized. Randomly polarized light such as elliptically polarized light. For this reason, it is difficult to combine laser light by a method similar to this combined laser light. Therefore, in this technique, the combination of two beams of laser light is limited, and the output is further increased. It is difficult.

On the other hand, there has been proposed a technique capable of synthesizing laser beams of three beams or more. For example, FIG. 9 is disclosed in Japanese Patent Laid-Open No. 2-139526. A plurality of (here, three) laser diodes 61A to 61C
Are respectively condensed by condensing lenses 62A to 62C, and the phase adjustment plates 63A to 63C align the phases of the mutual laser lights and enter the biaxial crystal 64. The biaxial crystal body 64 has a conical refractive index distribution, and each laser beam is combined at one point by making it incident from the bottom surface.

[0007]

With the technique of FIG. 9,
It is more advantageous than the above-mentioned ones in that a large number of laser beams can be combined and a high output can be obtained. However,
In this technology, unless the frequency and phase of each laser light are matched, an output proportional to each laser output cannot be obtained,
It is necessary to make adjustments to match the positions of each laser beam with high accuracy, and by equipping the adjustment mechanism for that, the structure of the device becomes complicated, and the frequencies and phases of many laser beams all match. Adjustment becomes extremely complicated and difficult, and it is extremely difficult to actually configure this kind of device.

[0008]

It is an object of the present invention to combine a large number of laser beams to obtain a high output, while avoiding the complication of its structure and obtaining a high output. It is an object of the present invention to provide a laser beam synthesizing device capable of automatically performing such adjustment.

[0009]

A laser beam synthesizing apparatus according to the present invention comprises a first laser light source for generating vertically polarized laser light, a second laser light source for generating horizontally polarized laser light, and the vertical laser light source. An optical combiner for reflecting one of the polarized laser light and the laterally polarized laser light and transmitting the other laser light to combine the two laser lights, and an optical path length between the first laser light source and the optical combiner And a means for controlling the optical path length between the laser light source and the photosynthesizer so as to be equal to each other.

In this case, each of the first laser light source and the second laser light source is provided with means for controlling the frequency of the generated laser light to a specific frequency, and controls the frequency of this laser light. The means is a piezo element for displacing a resonance mirror that constitutes a laser resonator, a light receiving element configured to maximize the output when the generated laser light has a specific frequency, and an output of the light receiving element. It is composed of a lock stabilizer which controls the voltage applied to the piezo element so as to maximize the voltage.

The means for controlling the length of each optical path between the first and second laser light sources and the optical combiner is a reflecting mirror arranged in the optical path of one of the laser lights and reflecting the laser light. It is composed of a piezo element for displacing the reflection mirror, a light receiving element for receiving the combined laser beam, and a lock stabilizer for controlling the voltage applied to the piezo element so that the output of the light receiving element is maximized. .

Another laser beam synthesizing device of the present invention is provided with two sets of the above laser beam synthesizing devices, and one of the laser beams output from each laser beam synthesizing device is a means for longitudinally polarizing the other, and the other is A means for laterally polarized light, and an optical combiner for reflecting one and transmitting the other for combining both laser beams,
It is characterized in that it is provided with means for controlling the optical path length between one of the laser beam synthesizing devices and the light synthesizing device and the optical path length between the other laser beam synthesizing device and the optical synthesizing device to be equal.

[0013]

The frequency of the laser light generated by the first laser light source and the frequency of the laser light generated by the second laser light source are matched, and the optical path length from each light source to the photosynthesizer is matched so that the phases of both laser lights are matched. Then, the vertically polarized laser light and the horizontally polarized laser light combined in the optical combiner have spatial and temporal coherence, and the combined laser light is output as linearly polarized light. For this reason, it becomes possible to further combine the output laser beams, to combine a large number of laser beams to increase the output of the laser beams, and to automatically match the frequency and phase of the laser beams. It can be done and simplifies its adjustment work.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a configuration diagram of a first embodiment of the present invention, and the outline of the present embodiment will be described with reference to the same drawing. Reference numeral 1 is a first Ar laser light source that outputs vertically polarized laser light, and 2 is a second Ar laser light source that outputs horizontally polarized laser light. Then, the laser light from the first Ar laser light source 1 is reflected by the first reflection mirror 3
And is incident on one surface of the photo-combiner 4 configured as a half mirror with zinc selenide. In addition,
The first reflection mirror 3 is mounted and supported by the piezo element 8. Further, the laser light from the second Ar laser light source 2 is directly incident on the other surface of the photosynthesizer 4. In this case, the first and second Ar laser light sources 1, 2
The respective arrangement positions are set so that the optical path lengths from the to optical combiner 4 are equal.

In the optical combiner 4, the laser beams from the first and second Ar laser light sources 1 and 2 are combined, and the combined laser beam is a second reflecting mirror 5 which is configured as a semi-transmissive mirror. It is reflected by and used as the laser light output. Further, a part of the laser light is transmitted through the second reflection mirror 5 and is received by the light receiving element 6. A lock instabilizer 7 is connected to the light receiving element 6, and the lock instabilizer 7 controls the piezo element 8 that supports the first reflection mirror 3 to cause the optical combiner 4 to operate.
The phases of the laser light from the Ar laser light sources 1 and 2 are adjusted.

The first and second Ar laser light sources 1,
2 has the same configuration, which is shown in FIG. In the figure, 11 is an Ar laser tube, 12 is a resonance mirror, and 13 is an output mirror, and these constitute a laser optical resonator.
The resonance mirror 12 having a semi-transparent structure is mounted on the piezo element 14 on the back surface thereof, and a filter 15 and a light receiving element 16 for selecting a specific wavelength light from a part of the laser light are provided behind it. This light receiving element 1
6 and the piezo element 14 are connected to the lock stabilizer 17.

The lock stabilizer 17 is, for example, LASING RESERCH CHRP, MODE.
L80 and 215 are provided, and the voltage applied to the piezo element 14 is controlled according to the detection output of the laser light in the light receiving element 16 to control the piezo element 14
Shifts the position of the resonance mirror 12 on the optical axis, thereby adjusting the distance from the output mirror 13 to change the resonance length of the laser light resonator and controlling the frequency of the output laser light. In this case, the frequency of the laser light in the laser optical resonator can be set to the single-wavelength transmission frequency of the filter 15 by feedback controlling the piezo element 14 so that the output of the light receiving element 16 becomes maximum.
The piezo element 14 causes a slight distortion when a voltage is applied,
This displaces the mounted resonant mirror 12.

In the light combiner 4, the horizontally polarized light is transmitted and the vertically polarized light is reflected, and as a result, both polarized laser lights are combined and emitted. FIG. 3A is a graph obtained by calculating the beam intensity reflectance (square of the amplitude reflectance) with respect to the laser beam incident angle. Since the beam intensity reflectance depends on the polarization direction (electric field vector direction), the characteristics are different between vertically polarized light and horizontally polarized light. In the figure, the incident angle at which the beam intensity reflectance of laterally polarized light is 0 is called Brewster's angle. Therefore, if the optical combiner 4 is set to have the Brewster angle with respect to the optical axis of the second Ar laser light source 2, it is possible to transmit the horizontally polarized light and reflect the vertically polarized light as described above.

The characteristic of quartz is shown in FIG. 3 (b). From this characteristic, quartz can be used for the photosynthesizer. In addition, cadmium sulfide, bromine arsenic glass, etc. can be used. Further, as described above, when the photosynthesizer made of zinc selenide is set to Brewster's angle,
There is no loss in the horizontally polarized light, but a reflection loss of 10% or more occurs in the vertically polarized light. Therefore, it is preferable that the actual set angle is about the Brewster angle and an average value of 90 degrees. The optimum value can be obtained by the following procedure.

That is, if the incident angle is ψ and the transmission angle is χ, the horizontal polarization loss Loss (1) and the vertical polarization loss Loss (2) are as follows. Loss (1) = tan ² (ψ−χ) / tan ² (ψ + χ) Loss (2) = sin2ψ · sin2χ / sin ² (ψ +)
χ) The sum of these becomes the total loss Loss (ψ). from now on,
The extremum that causes the minimum loss between Brewster's angle and 90 degrees is 1
Since there exists one, if you solve dLoss (ψ) / dψ = 0,
This is the set angle.

The laser light combined by the light combiner 4 is reflected by the second reflecting mirror 5 and used as high-power laser light. Further, a part of the laser light is transmitted through the second reflecting mirror 5 and is received by the light receiving element 6. The lock stabilizer 7 connected to the light receiving element 6 feedback-controls the piezo element 8 mounting the first reflecting mirror 3 so that the light receiving output of the light receiving element 6 is maximized, and the first reflecting mirror 3 The position of the reflection surface of is displaced. Due to the displacement of the first reflection mirror 3, the optical path length of the laser light from the first Ar laser light source 1 is changed, and the phase with the laterally polarized laser light from the second Ar laser light source 2 is matched in the optical combiner 4.

Therefore, according to the laser beam synthesizing apparatus having this structure, first, in the first and second Ar laser light sources 1 and 2, the lock instabilizer 17 is used as the filter 1.
In order to control the voltage applied to the piezo element 14 so that the output received by the light receiving element 16 through 5 becomes maximum, the resonance mirror 13 is displaced by this piezo element 14 and set at a predetermined position. As a result, the distance between the output mirror 12 and the resonance mirror 13 is set, the resonance length of the laser light resonator is set, and the frequency of the laser light is set equal to the transmission frequency of the filter 15. Therefore, the frequencies of the vertically polarized laser light and the horizontally polarized laser light output from the first and second Ar laser light sources 1 and 2 are locked to a constant frequency, and both are matched.

In this embodiment, the filter 15 is A
It is arranged to accommodate multi-lines of 488 nm, etc. other than the output wavelength of 514 nm of the r laser. For example, 5
If only the output of 14 nm is detected and the frequency of 514 nm is stabilized, the oscillating 488 nm signal is also locked to that frequency and stabilized.

The laser lights having the same frequency are incident on the photosynthesizer 4, the vertically polarized light is reflected, and the horizontally polarized light is transmitted, whereby both laser lights are combined. At this time, when the laser lights from the Ar laser lights are combined to obtain the maximum output, it is necessary to consider the spatial coherence and the temporal coherence of both laser lights. In order to enhance the spatial coherence, the frequencies of the laser beams should be matched,
Therefore, as described above, the frequencies of the laser beams are controlled by the Ar laser light sources 1 and 2, so that the frequencies can be matched.

On the other hand, the temporal coherence is the photosynthesizer 4
In, the phase of each laser beam may be aligned, and for that purpose, the optical paths from the Ar laser light sources 1 and 2 to the photosynthesizer 4 may be equalized. Therefore, the second reflection mirror 5
The laser light transmitted through the light receiving element 6 is received by the light receiving element 6, and the voltage applied to the piezo element 8 is controlled by the lock stabilizer 7 so that the light receiving output becomes maximum, and the first reflecting mirror 3 is displaced by the piezo element 8. ing. This allows
The optical path of the laser light from the first Ar laser light source 1 is finely changed, and the second Ar laser light source 2
It is possible to adjust the phase with the laser light from the.

By thus increasing the spatial coherence and the temporal coherence, as shown in the vector diagram of FIG. 4, the vertically polarized laser light and the horizontally polarized laser light are kept in the linearly polarized state in the photosynthesizer. It can be synthesized as it is. Here, since the laser intensity of each polarized light is equal, it becomes a linearly polarized light having an angle of 45 degrees.

FIG. 5 is a block diagram of an embodiment to which the laser beam synthesizing apparatus of the above embodiment is applied. In the figure, the configuration of the portion surrounded by the broken line is the same as that of the laser beam synthesizing apparatus of the above-described embodiment, and two laser beam synthesizing apparatuses 100 and 200 having the same configuration are arranged and output from each apparatus. The laser light is synthesized again. A first Faraday rotator 21, an optical combiner 23 made of zinc selenide, and a third reflecting mirror 24 are arranged in the optical path of the laser light output from the first laser beam combiner 100. Further, the second Faraday rotator 22 is provided in the optical path of the laser light output from the second laser beam combining device 200.
The fourth reflection mirror 25 is provided, and the laser light reflected by the reflection mirror 25 is made incident on the photosynthesizer 23.

The fourth reflecting mirror 25 is mounted on the piezo element 26, and the piezo element 26 is constructed so as to be controlled by the lock instabilizer 27. The lock stabilizer 27 is a light receiving element 28 for receiving the laser light transmitted through the third reflecting mirror 24.
The piezo element 26 is controlled according to the received light output of
The control for displacing the reflection mirror 25 is the same as in the case of the above embodiment.

Here, the first and second Faraday rotators 21 and 22 have a function of rotating the polarization direction of light passing therethrough by applying a magnetic field to a crystal having magnetic flash, such as YAG. Have. In this example, the first Faraday rotator 21 rotates the laser light from the first laser beam combiner 100 by 45 degrees to the right to make it laterally polarized, and the second Faraday rotator 22.
Rotates the laser beam from the second laser beam synthesizing device 200 to the left by 45 degrees to make it vertically polarized.

Therefore, according to this configuration, the first laser beam A and the second laser beam A are emitted from the second laser beam combining device 200.
A laser beam obtained by combining the laser beams of the r laser light sources 1 and 2 is output, is vertically polarized by the second Faraday rotator 22, is reflected by the fourth reflecting mirror 25, and is input to the optical combiner 23. Further, the first laser beam synthesizing apparatus 100 outputs a laser beam obtained by synthesizing the laser beams of the first and second Ar laser light sources 1 and 2, which is photosynthesized by the first Faraday rotator 21 as laterally polarized light. Input to the container 23.

In the light combiner 23, the vertically polarized light is reflected and the horizontally polarized light is transmitted as described above, so that both laser lights are combined and the output thereof is further increased. The laser beam having the increased output is reflected by the third reflecting mirror 24 and output. At this time, the maximum output can be obtained by matching the spatial and temporal coherences of the two laser beams in the optical combiner 23, which is also the same as in the above-mentioned embodiment. Therefore, the lock instabilizer 27 operates as the third reflection mirror. The piezo element 26 is controlled according to the output of the light receiving element 28 that receives the laser beam that has passed through 24, and the fourth reflecting mirror 25 is displaced to control the phases of the two laser beams to match.

As described above, according to the present invention, since the laser beams synthesized by the first and second laser beam synthesizing devices 100 and 200 are linearly polarized, it is possible to synthesize these laser beams again. Become. Then, since the re-synthesized laser light is also linearly polarized, it is possible to further synthesize the laser light. Therefore, by constructing this multiplex, it is possible to combine extremely high-power laser light. Further, even in this case, since the frequency and phase of the laser light to be combined are automatically adjusted in each combining device, it is possible to easily realize the combination of laser lights.

Here, in each of the above embodiments, an example in which a laser resonator is configured as a laser light source is shown, but it goes without saying that the present invention can be implemented in the same manner even if it is configured by a laser oscillator. .

In the present invention, the structure shown in FIG. 6 is also possible. The first laser light oscillator 31, the second laser light oscillator 32, the reflection mirror 33, and the filter 34.
Composed of and. The laser light (ω1) emitted from the first laser light oscillator 31 enters the filter 34. on the other hand,
The laser light (ω) emitted from the second laser light oscillator 32
2) is reflected by the reflection mirror 33 and enters the filter 34. The filter 34 is provided with a coating that transmits ω1 and reflects ω2. With this configuration, it is possible to combine the laser beams from the first and second laser beam oscillators 31 and 32 in the filter 34.

In this example, since the wavelengths of the two laser beams are different, there is no concern about the output reduction due to interference when the two waves are combined. Therefore, the laser beams can be easily combined without the need for a complicated system such as fixing the frequency and phase of the laser light (piezo element for phase adjustment, lock instabilizer, etc.). .

The configuration shown in FIG. 7 is also possible. First
Laser light oscillator 41 and second laser light oscillator 42
And a third laser light oscillator 43 and three optical fibers 4
4 to 46. In this configuration, the laser lights emitted from the laser light oscillators 41 to 43 enter the optical fibers 44 to 46, respectively. This optical fiber 44-46
By bundling the emission ends of the laser beams, it is possible to easily realize laser beam synthesis, although not perfect beam synthesis. This configuration is advantageous because it can be easily designed if an Ar laser with a coagulator optical fiber used for medical purposes is handled.

[0037]

As described above, according to the present invention, the means for controlling the optical path length between the light combiner for synthesizing the vertically polarized laser light and the horizontally polarized laser light and the light source of each laser light to be equal. Since it is provided, the phases of the two laser beams can be matched in the optical combiner, and the laser beams combined in the optical combiner can be output as linearly polarized light.
For this reason, this output laser light can be further combined, a large number of laser lights can be combined to increase the output power of the laser light, and the phases of the laser lights can be automatically matched. There is an effect that the adjustment work can be simplified.

Further, since the laser light source for generating each laser beam is provided with a means for controlling each laser beam to have a specific frequency, the coherence of each laser beam in the photosynthesizer is enhanced and synthesized. It is possible to secure the linear polarization of the laser light.

Further, another laser beam synthesizing apparatus of the present invention comprises two sets of the above laser beam synthesizing apparatuses,
A means for vertically polarizing one of the laser beams output from each laser beam synthesizing device, a means for horizontally polarizing the other, and an optical synthesizer for synthesizing both laser beams by reflecting one and transmitting the other, Means for controlling the optical path length between the laser beam synthesizing device and the optical synthesizer and the optical path length between the other laser beam synthesizing device and the optical synthesizer to be equal, thereby synthesizing in a linearly polarized state. The generated laser beams can be further combined, and a large number of laser beams can be combined to easily obtain an extremely high-power laser beam.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a laser beam synthesizing apparatus of the present invention.

FIG. 2 is a configuration diagram showing a configuration of an Ar laser light source used in the present invention.

FIG. 3 is a diagram showing transmission / reflection characteristics of an optical combiner.

FIG. 4 is a vector diagram for explaining the action of photosynthesis.

FIG. 5 is a configuration diagram showing a configuration of an application example of the present invention.

FIG. 6 is a configuration diagram of another embodiment of the present invention.

FIG. 7 is a configuration diagram of still another embodiment of the present invention.

FIG. 8 is a configuration diagram of an example of a conventional laser beam combining device.

FIG. 9 is a configuration diagram of another example of a conventional laser beam combining device.

[Explanation of symbols]

 1, 2 Ar laser light source 3 First reflection mirror 4 Photosynthesis device (zinc selenide) 5 Second reflection mirror 6 Light receiving element 7 Lock stabilizer 8 Piezo element 11 Ar laser tube 12 Resonance mirror 13 Output mirror 14 Piezo element 15 Filter 16 Light receiving element 17 Lock instabilizer 100 First laser beam synthesizing device 200 Second laser beam synthesizing device

Claims (6)

[Claims] 1. A first laser light source for generating vertically polarized laser light, a second laser light source for generating horizontally polarized laser light, and one of the vertically polarized laser light and the horizontally polarized laser light. In a laser beam synthesizing device including a light synthesizing device that reflects and transmits the other laser light, the optical path length between the first laser light source and the light synthesizing device and the second laser light source and the light synthesizing device. A laser beam synthesizing device comprising means for controlling the optical path lengths between them to be equal. 2. The laser beam synthesizing apparatus according to claim 1, wherein the first laser light source and the second laser light source each include means for controlling the frequency of the generated laser light to be a specific frequency. 3. The means for controlling the frequency of laser light is configured so that the output is maximum when the generated laser light has a specific frequency and a piezo element that displaces a resonant mirror that constitutes the laser resonator. And a lock instabilizer for controlling the voltage applied to the piezoelectric element so that the output of the light receiving element is maximized.
Laser beam synthesizer. 4. A means for controlling the length of each optical path between the first and second laser light sources and the light combiner is a reflection mirror arranged in the optical path of one of the laser lights and reflecting the laser light.
It is composed of a piezo element for displacing the reflection mirror, a light receiving element for receiving the combined laser beam, and a lock stabilizer for controlling the voltage applied to the piezo element so that the output of the light receiving element is maximized. The laser beam synthesizing device according to claim 1. 5. A laser beam synthesizer having two sets, each laser beam synthesizer comprising a first laser light source for generating a vertically polarized laser beam and a second laser light source for generating a horizontally polarized laser beam. A light source, means for controlling the frequency of the laser light generated in each laser light source to be a specific frequency, and one of the longitudinally polarized laser light and the laterally polarized laser light is reflected and the other is transmitted to both. An optical combiner for combining the laser beams, and a means for controlling the optical path length between the first laser light source and the optical combiner to be equal to the optical path length between the second laser light source and the optical combiner. The laser beam output from each of the laser beam synthesizing devices is provided with a unit for vertically polarizing one of the laser beams, a unit for horizontally polarizing the other, and one of the laser beams is reflected and the other is transmitted to synthesize both laser beams. Photosynthesizer and one laser bee A laser beam synthesizing device, comprising means for controlling the optical path length between the optical synthesizing device and the optical synthesizing device to be equal to the optical path length between the other laser beam synthesizing device and the optical synthesizing device. 6. The laser beam synthesizing apparatus according to claim 5, wherein the means for converting the laser light output from the laser beam synthesizing layer into vertically polarized light or horizontally polarized light is a Faraday rotator.