JPS63240091A - Free-electron laser device - Google Patents

Abstract

PURPOSE:To generate a laser regardless of the direction of electron beams by mounting an optical fiber and an electron beam source irradiating the optical fiber with relativistic electron beams and emitting Cerenkov beams in the optical fiber. CONSTITUTION:The title laser device consists of an electron accelerator 3 outputting electron beams having high energy and having a large aperture and an optical fiber 1 arranged so that relativistic electron beams 20 emitted from the electron accelerator 2 are applied, and the angle of the direction of the electron beams 20 and the longitudinal direction of the optical fiber 1 is brought to a value such as a right angle. Mirrors 4a, 4b for resonance are evaporated at both ends of the optical fiber 1, and the reflectivity of one mirror 4b for resonance is brought to 100%, and the reflectivity of the other mirror 4a for resonance is made slightly lower than that of the mirror 4b and a laser- beam output is acquired from the mirror 4a side. That is, Cerenkov beams are generated in the optical fiber 1 by the irradiation of free electrons, but they are propagated into the optical fiber 1 without leaking to the outside and stimulated emission is induced. Accordingly, laser beams can be extracted from a terminal.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a free electron laser device.

[Prior art]

Free electron lasers are known as new lasers. A free electron laser excites a light-emitting medium by irradiating it with free electrons, and laser oscillation is performed in the same direction as the traveling direction of the electron beam. This is no exception for devices that generate light using the Cherenkov effect. That is, this Cerenkov free electron laser irradiates free electrons into a vacuum, slows down the phase velocity of the light using a slow wave structure in the vacuum, and attempts to perform laser oscillation in the same direction as the electron direction.

(Problem to be solved by the invention) To enable such laser oscillation, electrons with a speed equal to the speed of light in the light-emitting medium are required, so the energy purity conditions for free electrons are extremely strict for practical use. development is being prevented.

The present invention has been made in order to solve such problems, and it is an object of the present invention to provide a free electron laser device that solves the constraint on energy purity by utilizing the property of an optical fiber to confine and propagate light. With the goal.

[Means for solving problems]

A free electron laser device according to the present invention includes an optical fiber and an electron beam source that irradiates the optical fiber with a relativistic electron beam, and emits Cerenkov light within the optical fiber, and outputs a laser beam from the optical fiber terminal. It is characterized by being designed to obtain the following.

[Effect]

Cherenkov light is generated in the optical fiber by free electron irradiation. The emission direction of this light has a certain angle with respect to the irradiation direction of the electron beam, but since this direction is larger than the total reflection angle of the optical fiber, it is propagated within the optical fiber without leaking to the outside. This means that laser light can be extracted from the terminal.

[Principle of the invention]

First, the principle of the invention will be explained below.

Now, as shown in FIG. 1, free electrons 2 are irradiated onto the optical fiber 1 at right angles to the longitudinal direction of the optical fiber 1. If the free electron energy is higher than a predetermined value, the optical fiber 1
Cerenkov light is generated inside. The angle θ between the direction of emission of Cherenkov light and the direction of free electron irradiation is θ = cos 'c/v ・where C: speed of light in vacuum V: speed of free electrons ε: expressed as the refractive index of the optical fiber. be done. Now y −+ (then ε−1,45 in the core 1a of the quartz optical fiber 1, so θ#46.
The light at this angle is 4° and enters the interface between the core la and the cladding 1b at the same angle θ, but the total reflection angle at this interface is 46°, so the Cherenkov light does not go out but enters the core. will be propagated. Therefore, by irradiating an electron beam in the same direction over a suitable length, light having the same angular component will be generated within the optical fiber, thereby generating stimulated emission within the core la. In order to improve stimulated emission, it is desirable to use a material having a crystal structure, such as a quartz-based optical fiber. Further, the optical fiber may have only a core without a cladding. This is because total reflection only needs to occur on the core surface.

Note that the irradiation angle of the electron beam may not be perpendicular to the optical fiber, but may be inclined. If it is inclined, θ becomes larger, so there is no problem.

〔Example〕

FIG. 2 is a schematic diagram showing an embodiment of a free electron laser according to the present invention. The laser device of the present invention is composed of a large-diameter electron accelerator 2 that outputs a high-energy electron beam, and an optical fiber 1 arranged to be irradiated with a relativistic electron beam 20 emitted from the electron accelerator 2. The angle between the direction of the electron beam 20 and the longitudinal direction of the optical fiber 1 is a right angle.

Resonant mirrors 4a and 4b are deposited on both ends of the optical fiber 1, and the reflectance of one of the resonant mirrors 4b is set to 10.
0%, and the reflectance of the other resonant mirror 4a is made slightly lower than that to obtain laser light output from the mirror 4a side.

Since the optical fiber l can be bent freely outside the projection area of the electron beam 20 without any problem in laser generation, the output end side may be placed at any position.

Note that the resonant mirror may be provided outside the optical fiber, that is, the light emitted from the end face of the optical fiber to the outside may be received by a resonant mirror made of a concave mirror, and then enter the end face of the optical fiber again.

Needless to say, in this case as well, the reflectance of the mirror on the output side is set to be less than 100%.

FIG. 3 is a schematic diagram showing another embodiment of the laser device of the present invention.

The optical fiber 10 is arranged in a spiral plane, and the electron beam source that irradiates the relativistic electron beam from the direction perpendicular to this plane (the front and back sides of the drawing) is the same as that shown in Fig. 2. It is.

In such an embodiment, the electron beam emitted from the electron beam source is irradiated onto the optical fiber 20 without waste, and the emitted light is an integral of the electron beam, resulting in high energy utilization efficiency. In this embodiment, since the light emission angle at each part of the optical fiber 20 in the spiral circumferential direction is slightly different, it takes time for stimulated emission, that is, for laser oscillation.

However, although it will still output incoherent light,
This incoherent light is high-intensity white light and is useful as a high-intensity point light source.

〔effect〕

As described above, in the case of the present invention, a laser can be generated regardless of the direction of the electron beam, so there are few restrictions on use.

Further, even when V is small, if θ is in a range equal to or greater than the total reflection angle of the optical fiber, Cerenkov light does not exit from the optical fiber and laser oscillation is possible, and the requirement for energy purity is relaxed. Further, the present invention has excellent effects such as being able to select output light by the mode selection effect of the optical fiber.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle of the present invention, and FIGS. 2 and 3 are schematic diagrams of the laser device of the present invention. 1... Optical fiber 3... Electron accelerator 4a, 4b
...Resonance mirror patent Applicant: 1) Ken - 1 other representative Patent attorney Noboru Kono Figure 3 procedural amendment (voluntary) April 10, 1986

Claims (1)

[Claims] 1. An optical fiber comprising an electron beam source for irradiating the optical fiber with a relativistic electron beam, emitting Cerenkov light within the optical fiber, and obtaining a laser output from the optical fiber terminal. A free electron laser device characterized by: 2. The free electron laser device according to claim 1, wherein resonance mirrors are arranged at both ends of the optical fiber. 3. The free electron laser device according to claim 1, wherein the optical fiber is arranged spirally in the electron beam irradiation area.