WO2011016379A1

WO2011016379A1 - Light-source laser utilizing laser compton-scattering

Info

Publication number: WO2011016379A1
Application number: PCT/JP2010/062750
Authority: WO
Inventors: 洋介本田; 順治浦川; 和之坂上
Original assignee: 大学共同利用機関法人高エネルギー加速器研究機構
Priority date: 2009-08-05
Filing date: 2010-07-29
Publication date: 2011-02-10
Also published as: CA2807113C; CA2807113A1; JP2011035331A

Abstract

Provided is a laser oscillation device that can stabilize resonation even when the finesse of an optical resonator is made to be high, and which can generate laser rays stronger than conventional devices by accumulating laser rays within the optical resonator. The laser oscillation device is provided with: an excitation laser light-source that generates laser rays for excitation; a rare-earth fiber that generates laser rays having the desired wavelength, when a laser ray generated by the excitation laser light-source is supplied thereto; an optical resonator that is composed of two concave mirrors arranged facing each other, or composed of a group of mirrors including multiple plane mirrors, and that accumulates laser rays generated by the rare-earth fiber; an optical isolator that is inserted between the optical resonator and the rare-earth fiber, guides laser rays coming out from the rare-earth fiber to one end of the optical resonator, and shuts off laser rays going in the opposite direction; and a circling optical path that takes in laser rays eradiated out from the other end of the optical resonator, returns the laser rays to the optical resonator via the rare-earth fiber and the optical isolator, and promotes the resonation.

Description

Laser for light source using laser Compton scattering

The present invention relates to a laser device that generates strong laser light, and more particularly, to a laser for light source using laser Compton scattering that can oscillate stably even when the finesse of an optical resonator is increased.

In recent years, small light source devices using laser Compton scattering have been developed. The intensity of such a light source device as a light source depends on the intensity of the laser target that can be realized. When a pulsed linear accelerator is used as a base, a high-intensity pulse laser is used as the laser beam, or a method of temporarily amplifying the burst is used.

On the other hand, if the average intensity of the laser is to be increased by a continuous operation system based on a storage ring type device using a Compton scattering as shown in FIG. 7 or a superconducting accelerator, a continuous high intensity laser target is required. It becomes.

For this reason, in a conventional X-ray generator (see, for example, Patent Document 1) that generates X-rays by laser inverse Compton scattering when a laser beam and electrons collide, a known high-intensity mode-locked oscillator, for example, 500 W A strong laser beam is generated by using a laser generator having a high-intensity mode-locked oscillator having a performance of 10 psec / pulse, wavelength “1064 nm”, and repetition frequency “150 MHz” and an optical storage resonator.

Here, the optical storage resonator is a resonator that confines the laser light in a space in which the optical path is closed by a plurality of mirrors, effectively increasing the intensity of light from a relatively low-power laser light source, and continuously increasing the intensity. This is a promising technology that can realize intense laser light.

FIG. 8 shows a configuration example of a conventional laser storage device. The output from the laser oscillator is stored in an external resonator prepared independently. In order for light to accumulate in the resonator, the condition that a standing wave occurs in the resonator, that is, the mirror interval matches an integral multiple of a half wavelength must be satisfied. The resonance width is determined by the reflectivity of the resonator mirror, and becomes narrower as a higher reflectivity mirror is used to obtain a higher increase rate. In a resonator having an increase rate of 1000, the resonance width becomes sub-nanometer in terms of the position accuracy of the resonator mirror, and the resonance state is easily lost due to environmental disturbances such as vibration. In order to control the resonance conditions mechanically and maintain the laser accumulation state, it is necessary to perform advanced feedback control by piezo driving the resonator mirror. At present, the technical limit for stably maintaining resonance is an increase rate of about 1000.

JP 2009-16488 A

However, since the high-strength mode-locked oscillator used in such a conventional laser oscillation apparatus is very expensive, the laser oscillation apparatus itself is also expensive. In addition, in the conventional laser oscillation device, it is difficult to require an advanced technique for controlling the resonance state of the optical resonator with high accuracy, which determines the technical limit of the increase rate. .

Furthermore, in the conventional laser oscillation device, when the laser pulse generated by the high-intensity mode-locked oscillator is guided to the optical storage resonator and stored, unless the feedback control accuracy is considerably high, the laser pulse can be stored stably. There was a problem that I could not. In addition, the conventional laser oscillation apparatus has a problem that it can only store and amplify about 1000 times, and the laser pulse energy in the optical storage resonator is only about 100 μJ / pulse.

Therefore, the present invention can stabilize the resonance even if the finesse (accumulation amplification factor) of the optical resonator is increased, and is stronger than the conventional one by accumulating laser light in the optical resonator. An object of the present invention is to provide a laser oscillation device capable of generating laser light.

In order to achieve the above object, according to a first aspect of the present invention, there is provided a laser oscillation device that generates laser light by using an optical resonator to resonate laser light generated by a rare earth fiber. An excitation laser light source that generates excitation laser light and a rare earth fiber that generates laser light of a desired wavelength when supplied with the laser light generated by the excitation laser light source are disposed opposite to each other. An optical resonator configured to include two concave mirrors or a group of plane mirrors including a plurality of plane mirrors, and stores the laser light generated by the rare earth fiber, and is interposed between the optical resonator and the rare earth fiber. An optical isolator for guiding laser light from the rare earth fiber to one of the optical resonators and blocking laser light in the reverse direction; and from the other of the optical resonators. A laser oscillation device comprising: a circulating optical path that takes in the emitted laser light, returns the optical resonator to the optical resonator via the rare earth fiber and the optical isolator, and promotes resonance. .

Furthermore, the second aspect of the present invention is a laser oscillation apparatus that generates strong laser light by using an optical resonator to resonate laser light generated by a rare earth fiber, which is used for excitation. An excitation laser light source that generates laser light, and a rare earth fiber that generates laser light of a desired wavelength when supplied with the laser light generated by the excitation laser light source, and two concave mirrors arranged opposite to each other, or An optical resonator that is configured by a group of plane mirrors including a plurality of plane mirrors, stores the laser light generated by the rare earth fiber, and is emitted from the optical resonator and supplied via the rare earth fiber. A reflector that reflects laser light and returns the optical resonator to the optical resonator via the rare earth fiber and promotes resonance, and is emitted from the optical resonator. And, there is provided a laser oscillating apparatus characterized by emitting the other laser light to the outside.

Here, the rare earth fiber has a core doped with Yb. In addition, the laser light emitted from the other of the optical resonators is captured, a part of the captured laser light is emitted to the outside, and most of the laser light is passed through the rare earth fiber and the optical isolator, The resonance is promoted by returning to the resonator.

Furthermore, the optical resonator is a Fox Smith interferometer type composed of two concave mirrors and one plane mirror.

As a result, the laser oscillation device according to the present invention can stabilize the resonance even if the finesse of the optical resonator is increased, and can generate a strong laser beam by accumulating the laser beam in the optical resonator. Is made possible.

Furthermore, this device enables stable resonance even when a concave mirror having a reflectivity of “99.99%” or a high finesse optical resonator using a group of plane mirrors is used, and laser light is contained in the optical resonator. This makes it possible to generate strong laser light.

It is a figure which shows the concept of a circular oscillation type optical storage apparatus. 1 shows a configuration of a laser oscillation device based on circular oscillation type light accumulation according to a first embodiment of the present invention. 3 shows a configuration of a laser oscillation device using a folding oscillation type optical storage according to a second embodiment of the present invention. The current and oscillation intensity of the excitation LD in this apparatus are shown. The fluctuation | variation of the light intensity in this apparatus is shown. An application of the present invention to an electron gun driving laser will be described. It is a figure for demonstrating the concept of a Compton light source. It is a figure explaining the structure of the conventional laser storage apparatus.

1. DESCRIPTION OF THE FIRST EMBODIMENT OF THE INVENTION FIG. 1 is a diagram for explaining the concept of a circular oscillation type optical storage device, and FIG. 2 is a laser using a circular oscillation type optical storage according to a first embodiment of the present invention. The structure of an oscillation apparatus is shown.

As shown in FIGS. 1 and 2, in the external resonator of the laser oscillation apparatus according to the first embodiment of the present invention, the laser beam that has resonated and passed is re-input as a seed light to the laser amplification unit and amplified by stimulated emission. After that, it reenters the resonator.

If the gain in the amplification unit exceeds the circulation loss including the resonator unit, the system enters an oscillation state, and the laser light automatically continues to circulate in the optical path. Oscillation begins with the spontaneous emission light noise of the amplifier. Spectral components of the noise light that happen to be accepted by the resonance width of the resonator pass through the resonator, become the seed light after that, and are amplified in the circulation. Finally, the total energy that excites the amplifier is All are concentrated in this component, and the system is in a steady state where the amplifier is saturated.

The difference from the conventional method is that the resonator unit and the amplifier unit form a laser oscillator as a whole. In the conventional method, the resonance condition is canceled due to vibration or the like by using high-speed and high-accuracy feedback technology, whereas in the new method, the oscillation circuit itself automatically follows the resonance condition. The advantage is that the resonance state continues even if not.

In order to compensate for the loss of the complicated optical path that has passed through the resonator, a high gain amplifying unit is required, and a fiber amplifier capable of obtaining a high gain with a single path becomes the key to the development of this system. Therefore, in the present invention, the basic idea of the optical storage resonator and the high-efficiency fiber laser amplification method has led to the idea of a closed optical system (circular oscillation) that caused self-oscillation. In the high finesse type optical resonator according to the present invention, only the resonating laser beam is accumulated, so that the laser beam transmitted through the optical resonator is returned to the high-efficiency fiber laser amplifier, so that stable laser beam amplification is possible. At the same time, laser light accumulation was realized.

And it was confirmed that the laser beam resonated with the optical resonator can be amplified by the high efficiency fiber laser amplifier, and the laser beam obtained by the stable amplification can be accumulated in the optical resonator.

At this time, it was confirmed that laser light having energy more than 10,000 times the energy of laser light incident on the optical resonator was present in the optical resonator.

Then, an optical resonator is arranged in the exit path of the accelerator that accelerates the electron beam, the electron beam sufficiently accelerated by the accelerator is guided to the exit path, and directly collides with the laser light in the optical resonator, It was confirmed that a soft X-ray to a gamma ray beam can be generated.

The laser oscillation apparatus according to the first embodiment of the present invention shown in FIG. 2 includes a laser diode, an optical isolator, a demultiplexer / multiplexer (WDM), a Yb fiber, an optical isolator, and a first optical system. And an optical resonator, a second optical system, and an output coupler. The laser beam obtained by exciting the Yb fiber is circulated and accumulated in the optical resonator to resonate. A strong laser beam is generated in the resonator.

The laser diode is composed of a semiconductor laser element or the like that generates laser light having a wavelength necessary for exciting the Yb fiber. When a driving voltage is applied, the laser diode generates laser light, and laser diode → optical fiber. → Supply to the optical isolator through the path of the optical isolator terminal.

The optical isolator is configured so that the laser beam supplied to the terminal passes through and is emitted from the terminal, and the laser beam supplied to the terminal is blocked and does not exit from the terminal. When supplied, this is taken in through the optical fiber connected to the terminal, passes through, and exits from the terminal, and passes through the path of terminal → optical fiber → demultiplexer / multiplexer to demultiplex / multiplex. Supply to the waver. Further, when the laser beam is emitted from the demultiplexer / multiplexer and supplied to the terminal via the optical fiber, it is blocked to protect the laser diode.

When a laser beam having a first wavelength and a laser beam having a second wavelength are incident from one of the terminals, the demultiplexer / multiplexer synthesizes and emits the light from the other terminal. When the laser beam combined from the terminal is incident, it is demultiplexed, and the demultiplexed laser beam is emitted from the terminal and emitted from the terminal. The laser beam is emitted from the optical isolator. Is output and supplied to the terminal connected to the optical fiber, the laser light is taken in and supplied to the Yb fiber connected to the terminal. Further, when laser light is emitted from the Yb fiber and supplied to the terminal, the laser light is demultiplexed, and laser light having a divided wavelength is emitted from the terminal, and the demultiplexer / multiplexer terminal → light The optical fiber is supplied to the optical isolator through a path from the fiber to the optical isolator.

The Yb fiber is a double clad type fiber having a core doped with Yb. When a laser beam of a predetermined wavelength (excitation laser beam) is supplied from a demultiplexer / multiplexer and excited, Generates laser beams of different wavelengths and supplies them to the demultiplexer / multiplexer terminals and to the output coupler terminals.

In addition, the optical isolator is configured to capture the laser beam supplied to the terminal, pass it through and emit it from the terminal, and block the laser beam supplied to the terminal so that it does not exit from the terminal. / When the laser beam emitted from the demultiplexer / multiplexer is supplied through the path of the multiplexer / terminal → optical fiber → terminal, the laser beam is passed through the path of terminal → optical fiber → first optical system. , Supplied to the first optical system. Further, when laser light is supplied from the first optical system through the path of the first optical system → the optical fiber → the terminal, this is blocked to prevent the laser light from returning to the demultiplexer / multiplexer.

The first optical system includes a terminal connected to an optical isolator through an optical fiber, four mirrors that reflect laser light, a concave lens that adjusts the diameter of the laser light, and a convex lens. While the laser beam supplied to is taken in and reflected, the diameter, the deflection direction, and the like are adjusted, and the laser beam is made incident on an optical resonator arranged in the emission path of the accelerator that accelerates the electron beam.

The optical resonator includes a resonator structure (not shown) disposed in an emission path of an accelerator that accelerates an electron beam, a reflectance of 90% or more, a curvature radius of 250 mm, and a resonator structure. The concave mirror is attached to the resonator structure so that the reflectance is 90% or more, the radius of curvature is 250 mm, the distance from the concave mirror is the distance corresponding to the wavelength of the laser beam, and the concave side is opposed. And a piezo element which is disposed between the back surface of the concave mirror and the resonator structure, and deforms according to the applied voltage to adjust the position of the concave mirror, the mounting angle, and the like. When laser light is supplied from the optical system and the second optical system to the back surface of each concave mirror, the phase is adjusted while transmitting through each concave mirror and confining and accumulating it between the concave mirrors. In parallel with this operation, part of strong laser light accumulated between the concave mirrors is emitted from the concave mirrors and supplied to the first optical system and the second optical system.

The second optical system includes four mirrors that reflect laser light, a concave lens and a convex lens that adjust the diameter of the laser light, and a terminal that is connected to the optical isolator via an optical fiber. While the supplied laser beam is captured and reflected, the diameter, the deflection direction, and the like are adjusted and incident on the optical resonator. Further, the laser light emitted from the optical resonator is captured and reflected, and the diameter, the deflection direction, and the like are adjusted, emitted from the terminal, and supplied to the terminal of the output coupler via the optical fiber.

When the laser beam is supplied to one of the terminals, the output coupler captures this, distributes it to “9: 1”, emits it from each of the other terminals, and supplies the laser light to each of the other terminals. When the laser beam emitted from the Yb fiber is supplied to the terminal, it is configured to take out this, distribute it to “9: 1”, and emit from each terminal. “9: 1” is distributed, and “90%” is emitted from the terminal, and is supplied to the second optical system through a path of terminal → optical fiber → terminal of the second optical system. 10% "is emitted and supplied to an external measuring instrument for oscillation monitoring. Further, when a laser beam having a wavelength is emitted from the terminal of the second optical system and supplied through a route of the terminal of the second optical system → the optical fiber → the terminal, this is captured and distributed to “9: 1” “90%” is emitted from the terminal, and returns to the optical resonator through the loop path of terminal → Yb fiber → demultiplexer / multiplexer → optical isolator → first optical system → optical resonator, and oscillation is maintained. , "10%" is emitted from the terminal and supplied to an external measuring instrument for oscillation monitoring.

As described above, in the first embodiment of the present invention, the laser light generated by the Yb fiber is converted into the path Yb fiber → demultiplexer / multiplexer → optical isolator → first optical system → optical resonator, and Yb fiber → Using the output coupler → second optical system → optical resonator path, the optical resonator guides, accumulates, and resonates, and the laser beam transmitted through one concave mirror constituting the optical resonator is the optical resonator → Since the second optical system-> output coupler-> Yb fiber-> demultiplexer / multiplexer-> optical isolator-> first optical system-> optical resonator, return to the optical resonator and maintain oscillation. Strong laser light can be accumulated in the optical resonator.

Thus, a soft X-ray to a gamma ray beam can be generated by guiding the electron beam sufficiently accelerated by the accelerator to the emission path and directly colliding with the laser beam in the optical resonator.

At this time, the laser energy emitted from the optical resonator is that the laser light emitted from the optical resonator is optical resonator → second optical system → optical fiber → output coupler → Yb fiber → terminal of demultiplexer / multiplexer → light Fiber → optical isolator → first optical system → optical resonator path, which is determined by the circular optical path gain when returning to the optical resonator and the finesse of the optical resonator, so that the two concave mirrors constituting the optical resonator , A strong laser beam can be accumulated only by using a high finesse type that uses a reflectance of “99.99%”.

In addition, since there are no various members and equipment such as Yb fiber in the optical resonator, the optical resonator can be used to maintain stable resonance even when the optical resonator has a high finesse, and a strong laser. Light can be emitted.

In addition, self-oscillation enables stable accumulation of laser light, and the selection of laser light with the required specifications by installing a polarization selector, intensity converter, etc. outside the optical resonator And can be accumulated in the optical resonator.

Furthermore, an optical resonator is disposed in the exit path of the accelerator that accelerates the electron beam, and the electron beam sufficiently accelerated by the accelerator is guided to the exit path to directly collide with the laser beam in the optical resonator. Thus, a soft X-ray to a gamma ray beam can be generated.

At this time, by increasing the laser energy of the laser light in the optical resonator, even a small accelerator can achieve high brightness from soft X-rays to gamma-ray beams. In addition, it becomes possible to examine the characteristics of important materials in detail.

2. Description of Second Embodiment of the Present Invention FIG. 3 shows a configuration of a laser oscillation apparatus using folded oscillation type optical storage according to a second embodiment of the present invention.
As shown in FIG. 3, a laser diode, an optical isolator, a demultiplexer / multiplexer (WDM), a Yb fiber, a reflector, an optical system, and an optical resonator are provided. A strong laser beam is generated by resonating the laser beam obtained by excitation while accumulating it in the optical resonator.

The optical isolator is configured so that the laser beam supplied to the terminal passes through and is emitted from the terminal, and the laser beam supplied to the terminal is blocked so as not to be emitted from the terminal. When a laser beam is supplied from a laser diode through a fiber, it passes through and is emitted from a terminal. A demultiplexer / multiplexer is a path of terminal → optical fiber → demultiplexer / multiplexer. To supply. Further, when the laser beam is emitted from the demultiplexer / multiplexer and supplied to the terminal via the optical fiber, it is blocked to protect the laser diode.

When a laser beam having a first wavelength and a laser beam having a second wavelength are incident from one of the terminals, the demultiplexer / multiplexer synthesizes and emits the light from the other terminal. When the laser light combined from the terminal is incident, it is demultiplexed, and the split laser light is emitted from the terminal and emitted from the terminal, via an optical fiber connected to the terminal. When laser light having a predetermined wavelength is supplied from the optical isolator, it is captured and supplied to the Yb fiber connected to the terminal. When the laser beam is supplied from the Yb fiber connected to the terminal, the laser beam is demultiplexed, and the demultiplexed wavelength laser beam is emitted from the terminal and supplied to the reflector.

In the reflector, the terminal of the demultiplexer / multiplexer is processed by processing the end face, and when the laser beam is emitted from the demultiplexer / multiplexer terminal, this is reflected, Return to the demultiplexer / multiplexer terminal.

A Yb fiber is a double-clad type fiber whose core is doped with Yb, and is excited when a laser beam of a predetermined wavelength (excitation laser beam) is supplied from a demultiplexer / multiplexer and excited. The laser beam is generated and supplied to the demultiplexer / multiplexer terminal and also to the optical system terminal.

The optical system includes a terminal connected to the Yb fiber, four mirrors that reflect the laser beam, and two convex lenses that have a focal length of “+150 m”, collimate the laser beam, and adjust the diameter. While reflecting the laser beam supplied to the terminal, the diameter, the deflection direction, and the like are adjusted, and the laser beam is incident on the optical resonator.

The optical resonator has a reflectivity of 90% or more and a plane mirror disposed at an angle of 45 degrees with respect to the optical axis of the laser beam supplied from the optical system, and a reflectivity of 90% or more and is transmitted through the plane mirror. Is arranged so as to be orthogonal to the optical axis of the laser beam (or the reflected laser beam), reflects the incident laser beam, and emits a part to the outside, and has a reflectivity of 100%, The plane mirror reflected by the plane mirror and reflected again by the plane mirror and returned to the plane mirror, and placed on one plane mirror, for example, the back of the plane mirror, deformed according to the applied voltage, and the position of the plane mirror And a piezo element that adjusts the mounting angle, etc., when laser light is supplied from the optical system to the back surface of the plane mirror, it is transmitted through the plane mirror and is not confined and accumulated between the plane mirrors. Et al., To adjust the phase.

In parallel with the above operation, a part of the strong laser beam accumulated between these plane mirrors is emitted from the plane mirror, and when an external laser beam utilization device, for example, an electron and a laser beam collide with each other The inverse Compton effect is used to supply an X-ray generator that generates strong X-rays.

Thus, in the present invention, when considering application as a laser target for a Compton light source, if the oscillation can be made a mode-lock pulse, a higher peak intensity can be obtained even with the same average power, which is attractive. At present, it is considered to be multi-longitudinal mode oscillation in which multiple resonance conditions of the resonator oscillate simultaneously, and after inserting a saturable absorber mirror in a part of the peripheral circuit, the optical path length of the entire system is changed to the optical path of the resonator section If adjusted to an integral multiple of the length, the phases of a number of longitudinal modes can be made uniform, and harmonic mode locking can be achieved.

Also, if a SHG crystal is installed in the resonator part after making it a mode-locked pulse, there is a possibility that a high-efficiency high-repetition double-wave laser can be constructed. If the loss of the resonator is mainly determined by wavelength conversion, the pumping light power is all shifted to the second harmonic, and thus the efficiency is high. If the optical path length of the resonator section is matched to the number of accelerators and the entire circumference is adjusted to an integral multiple of that, it can be applied as a drive laser for a photocathode electron gun.

3. Explanation of Verification Experiment of Principle of the Present Invention Next, the result of the verification test of the principle of the present invention will be described.
For the purpose of verifying the principle of the device according to the present invention, a verification experiment was conducted with a low power system. A core-pumped Yb-doped single mode fiber was used as an amplifier, and a maximum of 500 mW pumping light from a laser diode having a wavelength of 976 nm was introduced from a WDM coupler. The gain of this amplifier is 38 (measurement with a 1064 nm wavelength laser). Waveguides other than the amplification fiber are also composed of a single mode fiber. After exiting from the fiber into the space, it enters the resonator via a lens system for matching and a mirror pair for adjusting the position angle. After the emission from the resonator, the light is again input to the fiber via the matching system. After adjustment using established procedures, the fiber input / output efficiency is 60% or more, which does not cause a large loss. A 9: 1 coupler was installed in the middle of the fiber optical path, and a part of the circulating light was monitored. The light circulation direction is limited by an isolator installed in the middle of the fiber optical path.

FIG. 4 shows the result of changing the output of the excitation LD while measuring the power from the monitor port in the apparatus of the present invention.

The resonator used in the above measurement is a finesse 30000 (increase rate 20000) composed of a resonator mirror having a reflectivity of 99.99%. It is shown that the oscillation starts when the LD current exceeds 350 mA, and the circulating light increases in proportion to the excitation power. From the light intensity measured at the monitor port, the light intensity realized in the resonator was estimated to be 440 W. When the resonator is observed with an IR viewer, it can be seen that high-intensity light is certainly accumulated as shown in FIG. It was shown that a 440 W laser beam can be realized without any control with a low power excitation laser of only about 500 mW.

FIG. 5 shows the result of examining the stability of oscillation on a short time scale by observing output light with a photodiode in the apparatus of the present invention.
FIG. 5 shows a state in which a resonator mirror having a reflectivity of 90% (increase rate of 20) is used and a resonator mirror having a reflectivity of 99.99% (increase rate of 20000) is used. In the case of a high finesse resonator, fine oscillation is observed in the oscillation light intensity. This seems to be because the system is always in a transient state as a result of an increase in the sensitivity of resonance conditions due to environmental vibrations as the resonance width becomes narrower. In this state, the resonance state is fluctuated by vibration, but the resonance is being recovered by spontaneous oscillation. It can be expected that this variation can be improved to some extent by increasing the rigidity of the resonator structure.

When considering application as a laser target for a Compton light source, if the oscillation can be mode-locked, higher peak intensity can be obtained even with the same average power, which is attractive. At present, it is considered to be multi-longitudinal mode oscillation in which multiple resonance conditions of the resonator oscillate simultaneously, and after inserting a saturable absorber mirror in a part of the peripheral circuit, the optical path length of the entire system is changed to the optical path of the resonator section If it is adjusted to an integral multiple of the length, the phases of a number of longitudinal modes can be aligned, and it is determined that harmonic mode locking is possible.

FIG. 6 shows an application example of the present invention to an electron gun driving laser. FIG. 6 shows the possibility that a high-efficiency, high-repetition double-wave laser can be configured by forming a mode-locked pulse and then installing an SHG crystal in the resonator section. If the loss of the resonator is mainly determined by wavelength conversion, the pumping light power is all shifted to the second harmonic, and thus the efficiency is high. If the optical path length of the resonator section is adjusted to the number of accelerators and the entire circumference is adjusted to an integral multiple of it, it can be applied as a drive laser for a photocathode electron gun.

4). Summary There is a laser storage technology as a technique for realizing continuous and high intensity laser light with high efficiency. By combining this with a high gain amplifier, the system can be brought into a self-oscillation state, and the technical difficulty of resonator control can be solved. This method is not only effective for a laser Compton light source, but it can be expected to be applied in various ways by combining with pulsing and SHG.

The present invention relates to a laser device that generates strong laser light, and more particularly, to a laser for a light source using laser Compton scattering that can oscillate stably even when the finesse of an optical resonator is increased, Has industrial applicability.

Claims

A laser oscillation device that generates laser light by using an optical resonator to resonate laser light generated by a rare earth fiber,
An excitation laser light source for generating excitation laser light;
A rare earth fiber that generates laser light of a desired wavelength when supplied with the laser light generated by the excitation laser light source;
An optical resonator configured to store two laser beams generated by the rare earth fiber, each of which is constituted by two concave mirrors arranged opposite to each other, or a plane mirror group including a plurality of plane mirrors;
An optical isolator that is interposed between the optical resonator and the rare earth fiber, guides laser light from the rare earth fiber to one of the optical resonators, and blocks laser light in the reverse direction;
A laser beam that is emitted from the other of the optical resonators, returns to the optical resonator via the rare earth fiber and the optical isolator, and a circulating optical path that promotes resonance;
A laser oscillation device comprising:
A laser oscillation device that generates strong laser light by using an optical resonator to resonate laser light generated by a rare earth fiber,
An excitation laser light source for generating excitation laser light;
A rare earth fiber that generates laser light of a desired wavelength when supplied with the laser light generated by the excitation laser light source;
An optical resonator configured to store two laser beams generated by the rare earth fiber, each of which is constituted by two concave mirrors arranged opposite to each other, or a plane mirror group including a plurality of plane mirrors;
A reflector that reflects one of the laser beams emitted from the optical resonator and supplied via the rare earth fiber, returns the laser light to the optical resonator via the rare earth fiber, and promotes resonance. ,
A laser oscillation apparatus, wherein the other laser beam emitted from the optical resonator is emitted to the outside.
3. The laser oscillation device according to claim 1, wherein the rare earth fiber has a core doped with Yb.
The output coupler captures a laser beam emitted from the other of the optical resonators, emits a part of the captured laser beam to the outside, and most of the laser beam via the rare earth fiber and the optical isolator. 4. The laser oscillation device according to claim 3, wherein resonance is promoted by returning to the optical resonator.
The laser oscillation device according to claim 2 or 4, wherein the optical resonator is of a Fox Smith interferometer type including two concave mirrors and one plane mirror.