JPH0638546B2 - Light storage ring - Google Patents

Description

The present invention relates to an optical storage ring using a synchrotron radiation light generator.

[Prior Art] Conventionally, a charged particle is moved along an orbit having a predetermined curvature at a velocity close to the speed of light to generate synchrotron radiation in the tangential direction of the orbit, and the synchrotron radiation is arranged so as to surround the outer periphery of the orbit. There has already been proposed a light storage ring having a reflection means for reflecting the synchrotron radiation light and a light extraction means for taking out the synchrotron radiation light accumulated in the reflection means as outgoing light. (Japanese Patent Application No. 62-228
See specification No. 543. [Problems to be Solved by the Invention] However, in the conventional optical storage ring, the synchrotron radiation light (SOR light) is simply stored in the optical storage ring to effectively use the synchrotron radiation light (SOR light). However, the stored light is not amplified or lased. Therefore, the emitted light collected by the light extraction means is
As shown in FIG. 4 (a), it has continuous wavelengths.

An object of the present invention is to provide an optical storage ring having means for amplifying the light stored in the optical storage ring and causing laser oscillation to dramatically increase the intensity of emitted light. By this means, the emitted light is not corrected, and it is shown in FIG.
As shown schematically in (b), it is expected that light with a specific wavelength λ will be amplified.

[Means for Solving the Problem] The light storage ring according to the present invention generates synchrotron radiation in the tangential direction of an orbit by moving charged particles along an orbit having a predetermined curvature at a velocity close to the speed of light. Then
In a light accumulating ring having a reflecting means arranged to surround the outer circumference of the orbit and reflecting the synchrotron radiation, and a light extracting means for taking out the synchrotron radiation accumulated in the reflecting means as outgoing light, It has an oscillating means that amplifies light having a specific wavelength and causes laser oscillation by interacting the accumulated synchrotron radiation with charged particles that orbit under a special condition.

The component of the oscillation means may be a selection means for selectively reflecting a specific wavelength of the accumulated synchrotron radiation.

As the selection means, for example, a part or all of the reflection means may be made of a diffraction grating.

Further, it can be constituted by means for injecting laser light into the reflecting means as a constituent element of the oscillating means.

[Embodiment 1] Referring to FIG. 1, a light storage ring to which the present invention is applied has a synchrotron radiation light generation device, a reflecting mirror 2 surrounding the outer periphery thereof, and a light extraction port 3. Here, an electron will be described as an example of the charged particle, but the charged particle may be a positron, an ion, or the like. The electron beam orbit (electron orbit) 1 and the reflecting mirror 2 are configured such that their centers of curvature are the same.

In the first embodiment of the present invention, the radius of curvature of the reflecting mirror 2 and the radius of curvature of the electron orbit 1 will be described later in order to use the synchrotron radiation light and electron beams accumulated in the light accumulating ring for laser oscillation. The diffraction grating 8 is arranged in a part of the reflecting mirror 2 in order to set a certain value and to cause laser oscillation.

The radius of curvature of the reflecting mirror 2 is calculated as follows. The radiant light emitted from the electron orbit 1 in the tangential direction is reflected by the reflecting mirror 2 that is concentric with the electron orbit 1 and contacts the electron orbit 1 again. In the light storage ring, the electrons circulate on the electron orbit 1 in the form of a pulse (bunches). Therefore, a special relationship is required between the radius of curvature of the electron orbit 1 and the radius of curvature of the reflecting mirror 2 in order for the reflected light to re-associate with the electrons to cause stimulated emission of light from the electrons.

By the way, since the speed of electrons and the speed of light are almost equal, a second bunch 7 other than the first bunch 6 that emitted light orbits the electron orbit 1 and rejoins the light. Is possible.

From the generation point A on the electron orbit 1 where the SOR light is generated, the SOR light is reflected at the reflection point B of the reflecting mirror 2 and the electron orbit 1
The distance that the SOR light travels up to the arrival point C that contacts with is 2d. A straight line O connecting the center of curvature O of the electron orbit 1 and the reflection point B
The included angle between B and the straight line OA connecting the curvature center O and the generation point A, and the included angle between the straight line OB and the straight line OC connecting the curvature center O and the reaching point C are set to θ as shown in the figure. Then, the condition for the SOR light generated from the first bunch 6 to be reunited with the second bunch 7 after being reflected by the reflecting mirror 2 is obtained.

The SOR light generated from the first bunch 6 at the generation point A is reflected at the reflection point B of the reflecting mirror 2, and this reflected light is reflected by the electron orbit 1
And reach at reaching point C. At this time, the second bunch 7 may also be at the reaching point C. That is, during this period, the SOR light travels a distance of 2d with its speed being c, and the second bunch 7 travels by 2rθ + nπr with its speed being v. 2d = 2
Since rtan θ, the condition for oscillating the light storage ring is that light and electrons first meet again at an accurate period.
Then, the condition for reuniting is simply expressed by the following equation.

(2rθ + nπr) / v− (2r tanθ) / c = 0 ...
(1) Here, electron orbit 1 is assumed to be a perfect circle. And 2
It is assumed that the vehicle is driven by two bunches (first bunch 6 and second bunch 7). n (≧ 1) is an integer and means that it is a bunch that is n behind. However, in Eq. (1), the point where the phase advances by half a wavelength due to reflection is neglected, and θ is not strictly defined as described later.

The following relationship exists between the radius R of the reflecting mirror 2 and the radius r of the bunch trajectory 1.

R = r / cos θ (2) When the SOR light is operated so as to rejoin the bunch in this way, it is expected to generate a very powerful laser light having a short pulse width. More specifically, it is generally known that when light interacts with electrons, such as SOR light, it is absorbed by the light or induces the emission of light from the electron, and the light is amplified. There is. Whether light is absorbed by an electron or amplified depends on the relative positional relationship between the electron and the phase of light.

However, the above-mentioned re-meeting condition between the light and the bunch is a necessary condition for causing laser oscillation, but this alone does not cause laser oscillation. When laser oscillation occurs in the optical storage ring, the bunch in the orbit must have electron density corresponding to the wavelength of the oscillating light. On the contrary, the grown laser beam forms electron density, and if it is not continued, laser oscillation does not occur. However, the density of the electron density is formed for a specific wavelength, and the density of the specific electron density is not formed when light of various wavelengths interacts with the bunch.
In other words, the wavelength of this light is not specified by the above equation (1). Then, at any wavelength, Eq. (1) is satisfied. Furthermore, the density of electrons cannot be maintained unless the phase relationship between the bunch and the oscillating light is always constant.

In order for electrons and light to re-associate and light of a specific wavelength to maintain the acceleration or deceleration phase, it is necessary that the phase of this density and the phase of light match each time.

Next, description will be given with reference to FIG.

FIG. 3 is a diagram showing how electrons approach when viewed from the light when the light path is taken along the z axis. Spontaneous emission light (SOR light) emerges from the peak of the orbit 1 of the radius r of the electron in FIG. 3 and then rejoins the electron at that peak. However, when the light and the electron interact at the contact point, the electric field created by the light is perpendicular to the traveling direction of the electron, so the electron is not affected by the electric field created by the light. Therefore, in this case, the electrons are neither decelerated nor accelerated. However, when the electron and the light meet again at an angle, the electric field created by the light has a component in the traveling direction of the electron, so that the electron is decelerated or accelerated. The stimulated emission of light from electrons occurs
It's time for the electrons to slow down. Therefore,
The condition under which stimulated emission of light repeatedly occurs and lasing occurs is when light interacts with electrons through the inner orbit z'in FIG. That is, in the state of laser oscillation,
It goes through a path slightly inside the orbit 1 of the radius r of the light electron. By the way, since the laser beam passes through the z'orbit, it goes without saying that the reassociation condition shown in the equation (1) is changed accordingly.

By the way, if light and electrons are in the deceleration phase in the first quadrant of FIG. 3 and enter the second quadrant at the same phase, in the second quadrant, x which is orthogonal to the z-axis direction of the traveling direction of the electron is assumed. It changes to the acceleration phase because the direction of the component is reversed. That is, during the change of the quadrant, more strictly speaking, from the point where the light and the electron intersect in the first quadrant to the point where the light and the electron intersect in the second quadrant, the phase of the light and the density of the electron If the phase shifts by half a wavelength, the deceleration phase will continue. The condition for the laser oscillation to occur is that the deceleration phase continues.

However, in reality, there are many lights having wavelengths that satisfy the condition that the phase of light and the phase of density of electrons deviate from each other by half a wavelength while proceeding from the first quadrant to the second quadrant. In particular, since the z'axis orbit can be arbitrarily drawn, the wavelength of light is not determined in that sense either.

In order to cause the laser oscillation, it is necessary to select a specific wavelength and form the sparse and dense bunches as described above. When laser oscillation occurs, it is necessary to satisfy the following equation, where λ is the wavelength at that time.

L × (c−v ₂ ) / v _z = λ / 2 (3) where L is the length of the path through which the light passes inside the circumferential orbit of the bunch with radius r, and v _z is the axial direction of the electron. Is the average speed of.

In more precise terms, when stimulated emission of light from an electron occurs, light has a somewhat longer wavelength due to recoil of the electron, so Eq. (3) must be considered accordingly. For example, the research report of Electronic Technology Research Institute (published by Electronic Technology Research Institute in May, 1979) The equation (7.1) listed in 29 may be used.

By the way, when the laser is oscillating, it must have a specific wavelength, but since L in equation (3) can take various values by changing the z'axis orbit, the oscillation wavelength is unique from this equation. Is not decided. Normally, in a free electron laser using an undulator, the oscillation wavelength is uniquely determined by the period of the magnetic field whose polarity alternates,
In oscillation by the light storage ring, the wavelength of light is not determined because magnetic fields with different polarities are not used.

As mentioned above, in order to use the optical storage ring to cause laser oscillation, a mechanism for selecting light with a spectrum as narrow as possible is required. As one method for this, in the first embodiment, the diffraction grating 8 is arranged in a part of the reflecting mirror 2 as described above. It is known that the diffraction grating 8 selectively reflects only a specific wavelength in a predetermined direction. It is possible to cause laser oscillation in the light storage ring by using light having a specific wavelength selected by the diffraction grating 8 as a seed. It is needless to say that the predetermined direction is a direction in contact with the electron orbit 1, specifically, a direction in contact with an orbit slightly inside the electron orbit 1. Also,
The diffraction grating 8 is arranged so that the predetermined direction does not coincide with the connection direction of the light extraction port 3 direction. This is because, when arranged in this way, the light of the specific wavelength selected by the diffraction grating 8 is not amplified in the light storage ring. In this way, the diffraction grating 8 plays a role of selecting a specific wavelength.

The entire reflecting mirror 2 may be replaced with the diffraction grating 8.

Now, as described above, the oscillation wavelength is determined in advance, the optical path is determined, and stimulated emission starts, but in order to grow oscillation, Eq. (1) needs to be modified, strictly speaking, according to the difference in the optical path. .

Referring to FIG. 5, the optical path of the oscillating laser light is e,
On the other hand, let f be the optical path of the spontaneous emission light and + α be the angle formed by e with respect to f. Light is emitted to -α, but the orbit of this light is g. Note that α is about several mrad. Light emitted in the directions of ± α with respect to the radius r of the electron orbit 1 is circumscribed on a circle 9 having a radius q. The relationship between r and q is shown by the following equation.

q = r * cos (α) (4) Next, the point where the light of e, f, g is emitted from the first bunch is A, the point where the light of e is reflected is B, and e is in the electron orbit. Let C be the point of contact. It is geometrically clear that the light of g is reflected by D, but also contacts the electron orbit at C.
However, the path f of the natural synchrotron radiation is different at the point C ', the electron orbit 1
Touch. As described above, the stimulated emission of light is performed at the optical path e of the laser light at the point A and then at the point E crossing the electron orbit. It is a condition for continuing the oscillation that the laser light on the optical path e intersects with the second bunch at the point C at the correct phase, which is expressed by the following equation.

First, let F and G be the points where the circle 9 is in contact with the laser light on the optical path e, and let the angle between OF and OG be 2ψ. In this case, T1 = (2ψr + nπr) / v (5) is the time required for the second bunch located at the point symmetry with point A to come to point C, where v is the velocity of the electron. T2 = 2 * q * tan (ψ) / c (6) This time difference between T1 and T2 is correct for the wavelength λ of the oscillating light, where T2 is the speed of light. In order to deal with the phase difference, | T1−T2 | = ± μλ / c (7). Here, μ is for correcting that the phase is shifted by μλ due to reflection by the reflecting mirror 2. What should be noted here is that the light passing through the optical path g also intersects with the electron at the point C, but since the optical path length is the same as that of the laser light on the optical path e, they also intersect at the same phase. That is, it is considered that the light passing through the optical path g is actually oscillated light, and therefore, according to the present invention, laser oscillation can be performed very well.

[Embodiment 2] FIG. 2 is a schematic plan view for explaining the principle of an optical storage ring according to a second embodiment of the present invention.

In the embodiment shown in FIG. 2, the diffraction grating 8 is not arranged in a part of the reflecting mirror 2 as in the first embodiment described above, but a laser beam having a specific wavelength is input from the laser device 5. The laser input port 4 is provided in the reflecting mirror 2 to input the laser light along the tangential direction of the electron orbit 1 (more accurately, an orbit slightly inside the electron orbit 1), but otherwise the first It is similar to the embodiment. It is possible to cause laser oscillation in the light storage ring by using the injected laser light as a nucleus.

The light storage ring is constructed as described above, and a part or all of the reflecting means is replaced with a diffraction grating as shown in FIGS. 1 and 2, or laser light is injected into the reflecting means. Therefore, if a light of a specific wavelength is selected, the bunch has a density corresponding to that wavelength. The phase of the bunch density and the phase of the light are half wavelength when the peak of the electron orbit 1 in FIG. 3 is exceeded. Since it is configured to shift, the deceleration phase continues and light amplification occurs. That is, it can be seen that laser oscillation can be performed. And further, such a condition must be met anywhere on the light storage ring. As shown in FIGS. 1 and 2, the light emitted from the two points a and b on the electron orbit 1 emerges at different times, passes the same time, and rejoins the same bunch at different times. After reuniting at the point a ', there is a lapse of time until another light reunites at the point b', and at the point b ', the light and the electron can have the same phase condition again. In this way, if some or all of the reflecting means is replaced with a diffraction grating, or if laser light is input to the reflecting means, it is considered that all SOR light accumulated in the light accumulating ring is converted into coherent laser light. To be Then, this laser light is continuously emitted from the light outlet 3.

[Effects of the Invention] As is clear from the above description, according to the present invention, a part or all of the SOR light reflecting means arranged so as to surround the outer periphery of the trajectory of charged particles having a predetermined curvature is diffracted. It is possible to cause laser oscillation in the optical storage ring by replacing with a grating or by providing a laser input port for inputting laser light to the reflecting means and inputting laser light from the laser light input port. There is an effect. Therefore, there is an effect that, of the light emitted from the light storage ring, the light having a specific wavelength increases and becomes monochromatic.

[Brief description of drawings]

FIG. 1 is a schematic plan view for explaining the principle of the light storage ring according to the first embodiment of the present invention, and FIG. 2 is a second plan view of the present invention.
3 is a schematic plan view for explaining the principle of the light storage ring according to the embodiment of the present invention, FIG. 3 is a view for explaining the conditions when the light storage ring of the present invention oscillates, and FIG. 4 is for the conventional and the present invention. FIG. 5 is a diagram showing the relationship between the wavelength and the intensity of emitted light, and FIG. 5 is an explanatory diagram in the case where the present invention has a different optical path. 1 ... Circular orbit of electron beam, 2 ... Reflector, 3 ... Light extraction port, 4 ... Laser input port, 5 ... Laser device, 6 ...
… First bunch, 7 …… Second bunch, 8 …… Diffraction grating, 9 …… Circle.

Claims (4)

[Claims] 1. A synchrotron radiation beam is generated in the tangential direction of the orbit by moving a charged particle along an orbit having a predetermined curvature at a velocity close to the speed of light, and is arranged so as to surround the outer periphery of the orbit. Accumulated synchrotron radiation in a light storage ring having reflection means for reflecting the synchrotron radiation light and light extraction means for taking out the synchrotron radiation light accumulated in the reflection means as outgoing light. An optical storage ring comprising an oscillating means that amplifies light having a specific wavelength to cause laser oscillation by interacting light with charged particles that orbit the orbit. 2. The light storage ring according to claim 1, wherein the component of the oscillation means is a selection means for selectively reflecting a specific wavelength of the stored synchrotron radiation. 3. The light storage ring according to claim 2, wherein a part or all of the reflecting means as the selecting means is made of a diffraction grating. 4. The light storage ring according to claim 1, wherein the constituent element of the oscillating means is means for introducing laser light into the reflecting means.