JPH03501431A - Surface pump type phased array laser oscillator using a looped fiber bundle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] name of invention Surface pump type phased array laser oscillator using a looped fiber bundle Technical field The present invention is characterized in that two optically polished end faces are stacked together to form one output aperture. Oscillation of loop-shaped fiber laser and phased array laser an amplification system, with a single When a laser mirror is arranged or a laser amplifier is configured, the output opening is An optical window index-aligned with the mouth is placed near the aperture. The laser medium made by bundling the fibers is placed in the frame constituting the opening of the valve. The present invention relates to what is optically excited through the image tip of the fiber. When configured as a shaker, a single laser mirror connects individual fiber lasers. partially propagates all of the tip output as a weighted, phase-locked beam. At least the output of the laser beam. When configuring the present invention as a laser amplifier is coated with anti-reflective material on the outside surface and has an anti-reflective coating on the opposite side between it and the output aperture. The input beam is amplified through an index-matched optical window. It enters the vessel and passes through it as a polarized beam.

The present invention is useful for producing g1 countable laser beams in the industrial, medical and defense fields. It is used as a

Overview of conventional technology In the prior art, phased array laser devices based on fiber bundles It is composed of optical fiber laser oscillators stacked on top of each other. The entire fiber laser oscillator is pumped or the pumped light is excited in that particular part by the optocoupler to be partially excited by This is also known as the so-called lateral excitation method. They used direct excitation using laser oscillation technology.

These conventional phased array, or fiber bundle based, lasers The technique of excitation via the output aperture in the device can excite efficiently. I can't. This is because most of the sheathing material on one end of the fiber is occupies the cross-sectional area, and the proportion of the area occupied by the doped fiber becomes smaller. It is. How to efficiently inject excited light into the end face of a fiber laser using conventional equipment Phased array lasers, which are used as a coupling means for Lenses arranged on each end face are used, and the excited light is directed to the corresponding lens. It is converged to match the fiber core. Conventional phased array laser system The device is also multiplied by its output beam being disturbed and scattered by the semiconductor. In the case of conventional equipment configured with laser diodes stacked together, the input Since more than 60% of the electrical energy is consumed in the array body, the output aperture The heating conditions become stricter.

In the present invention, these drawbacks and operational issues can be resolved by adjusting the diameter of the fiber core to the sheathing material. This was overcome by using fibers with a thickness approximately equal to or greater than .

Ideally, an optical fiber would contain multiple cores within its outer sheath. are constructed in such a way that the diameter of their core is greater than the distance separating them from each other. It is preferable that Furthermore, in a preferred embodiment, the present invention emits laser light. A multicore fiber doped with ions is used. In such a configuration The aperture formed by the optically polished end face of these fibers Most of the projected laser light can pass through the fiber core. for example , the excited light in a well-standardized narrow visible band is phase controlled by temperature control. If emitted from synchronized stacked laser diodes, the end of the device according to the invention It becomes possible to inject from the surface with high efficiency.

In the present invention, similarly, the polarization plane of the laser light inside the fiber is magnetically changed. It is also possible to propagate while rotating.

Background of the invention Pioneering research on fiber bundle lasers was conducted at the Royal Radar Institute in the UK in 1963. optical fiber bundles with commercial utility at that time. was revealed to propagate laser light. The initial goal was to create an early laser Coherently couples laser rod media to flexible coatings in laser systems The objective was to form a group of optical fibers into a fiber bundle and connect them to an aperture. death However, these experiments suggest that early optical fibers were used to transmit laser light. It has been shown that this method is not suitable at all. Hayabusa made in the 1970s With the advent of optical fiber technology in Details of some of the research were published in Optics, USA Vol. 18, No. 13, 2098. Published July 1979) Then, in 1984, the patent offices of the United Kingdom and the United States classified it with key elements. It was. for developing a phased array laser device based on fiber bundles. Based on pioneering efforts, the first invention intended for sale was published in the patent literature. (Hughes, U.S. Pat. No. 4,682,335, 1987) July 21).

This invention encompasses important aspects of the development of phase-locked fiber laser bundles. A system in which excited light is incident through the end face of a laser oscillation system. By modularizing the opening, laser emission that switches the loop-shaped laser fiber bundle is possible. An oscillator is realized, which enables lateral excitation at the threshold of laser oscillation. This is a laser oscillation system. When this invention is used as a laser pulse amplifier, If the pulse excitation at the end face is in the form of a traveling wave, which is excited prior to the passage of the laser pulse to be amplified. It is also a process that consumes the energy stored in the amplifier.

This invention is basically a glass laser, and the solution is that Severe operational challenges encountered when using body restraints and flat glass laser media It is. Firstly, in order to easily cool glass with low thermal conductivity, Thin glass fibers are used, and the glass fibers used are mutually exclusive. Due to its relative length, the thermal load on the entire gain path is minimized.

Second, the radiation caused by the self-destruction of the laser beam that occurs in the laser medium The problem with self-focusing is that the thickness of the fiber core increases the amplification of the laser light. This can be avoided by making it approximately equal to the wavelength.

When used as an amplifier, the invention is based on the Faraday effect. It is possible to rotate the plane of polarization of the laser beam that passes through the core of the bar. This makes it possible to place the body or parts of it in a magnetic field. This farah The Day rotation effect always acts in the same rotational direction, so in the present invention, the plane of polarization can be rotated. This is an effective technique for The polarization plane of the input laser beam is rotated in this way. Therefore, if the amplifiers of this invention are connected in series and optically coupled, multi-stage The present invention can be configured as an oscillator and as an amplifier. When configured as (scalar pull).

Purpose of invention The object of the present invention is to optically excite a loop-shaped fiber bundle laser from its end face. The goal is to provide the means to do so. In addition, pulsed excited light incident on the end face providing a looped fiber bundle oscillator optically switched by is also one purpose.

Another object of the present invention is to provide a fiber laser for this inventive device by means of side pumping of a fiber laser. This is to cause the fiber bundle body to oscillate as a laser at a threshold value.

Another object of the invention is to provide a laser structure that minimizes the heat load per unit area/volume. It is to provide.

Yet another objective is to minimize the chance of self-focusing within the laser gain medium. The purpose is to provide the configuration of the user media.

The object of the invention is to provide a talading medium whose diameter is larger than the mutual separation distance. The purpose is to provide a fiber laser core protected by shared power.

Providing a magnetic field forming means for rotating the polarization plane of the propagating laser beam, Similarly, it is an object of the present invention.

According to the invention, the optical output of the diode laser array determines its operating threshold. Its output is then side-pumped by the optical output of the diode laser array until Gigahertz (101o-10” per second) that quickly exceeded the threshold from the opening <7 pulses with a high repetition rate reaching the range of (response). In this invention, file By simply adding many fiber lasers to the original bundle of bar lasers, high output levels can be reached and excited them.

By increasing the intensity of the laser beam at the core of a particular fiber laser, A threshold, which is a nonlinear optical effect on frequency tuning, can be overcome.

The loop length of the individual fiber lasers as a whole is for the output of this invention. They do not need to be the same in order to ensure phase synchronized operation at the apertures. Output aperture Phase locking in It is also realized on the condition that it is large. In practice, this means that the fiber - Let's say that the length of the loop is several meters and the wavelength of the laser beam is 10-'cms. . By index matching on the output mirror, this mirror is optically Medium for index matching when polished to eye wave or higher fiber through either fiber loop to the surface of the mirror. The path length of the light from Accurately match the wavelength within the path. In addition to these conditions, doped Glass fibers have a relatively wide gain curve in the present invention, so A wide range of wavelengths is maintained around the wavelength of the peak. This situation means that the peak wavelengths are equal The fact that the wavelength of the laser does not change due to the fact that the fiber laser medium has suppresses the supermode wavelength even though it matches the peak of the gain curve make it possible to Similarly, the following points should be noted: In other words, The permode need not be sustained for the entire length of the fiber in this invention. However, it reaches several kilometers per unit cross-sectional area (cm), and the above level is If the length of the individual loops of the fiber is exceeded, i.e. several meters at the same time It is sufficient if it is of a certain extent.

Brief description of the drawing The invention will be better understood from the following description in conjunction with the drawings. However, these drawings are not intended to limit the scope of the invention in any way.

Figure 1 shows a bundle of looped fiber lasers connected to the output of a laser diode array. FIG. 2 schematically shows the arrangement of the present invention in the configuration of an oscillator that is more end-pumped. .

Figure 2 shows a thin-walled fabric whose core constitutes most of the cross-sectional area of the fiber bundle. A bundle of cut optical fibers is shown.

FIG. 1 shows a cross-section of one fiber in a bundle of fiber lasers;

FIG. 4 shows the basic building blocks of the loop-shaped fiber bundle of the present invention. A stacked orthogonal cross-section of the fiber is shown.

FIG. 5 shows the basic building blocks shown in FIG. 4 with their phase-locked outputs. Each layer is shown stacked so as to be phase-synchronized as a whole.

FIG. 6 shows the configuration of an amplifier chain in which a plurality of devices of the present invention are combined. centre Faraday rotation changes the polarization plane of the laser beam inside the bundle of fiber lasers mentioned above. is rotated through 90°, thereby reflecting the respective polarized beams. It passes through the mirror and becomes an output beam that can be propagated.

Detailed description of the invention In FIG. 1, 1 is a bundle of ion-doped loop lasers; multiple single-mode optical fibers whose core diameter is greater than their separation distance Consists of - 2 is a loop-shaped laser with each tip optically polished. A group of fibers is shown which collectively constitute a single output aperture of the present invention. 3 indicates the medium for matching the index, from the optically polished mirror 4 The light passes through any of the above loop-shaped laser fiber groups and returns to the mirror 4. This mirror 4 is provided to adjust the optical distance, and this mirror 4 is provided to adjust the optical distance. and serves as a Q switch in the configuration of the laser oscillator of the present invention.

In FIG. 1, 5 is a light emitting diode array, which is connected to the fibers of bundle 1. - Narrow optical absorption IF range that matches the optical absorption IF range of the laser-emitting ions added to the laser core. In order to irradiate light in the optical IF range to the fiber laser bundle 1 through the aperture 2, It has been established. The power supply to give energy to diode array 5 is , is indicated by the number 6, while F indicates the light output of the array 5, and this light F is reflected and bent by the tilted reflector indicated by number 8. This reflecting mirror 8 is configured to be able to transmit the wavelength of the laser beam. A phase-locked output beam from this inventive device is output as indicated by No. 9. It makes it possible.

In FIG. 2, the number 10 indicates a cross section of the bundle 1 of fiber lasers, where the number 11 with a diameter greater than the thickness of its cladding. The core of the fiber is shown.

In Figure 3, number 12 is an optical fiber with multiple cores; The wicks indicated by 3 are surrounded by a common jacket 12 and each wick 13 have a diameter greater than the distance by which they are separated from each other within the common envelope 12 .

In Figure 4, number 14 indicates an orthogonal section of the fiber bundle, where number 15 indicates There are multiple fiber cores shown and they are separated from each other by a certain distance. It has a larger diameter. The orthogonal cross section 14 brings these fiber modules into close proximity. This makes it possible to bundle them tightly.

In FIG. 5, number 16 indicates the laminated fiber formed by unit 14. Showing a bunch. Each unit 14 emits a coherent laser beam. The stacked portions of this unit 1 are also phase-locked to the final output beam. phase-locked pressure to form the beam 9 into a group of phase-locked laser beams. Fire a beam at each.

Figure 6 shows a device using the device of the present invention as an amplifier chain, which is larger than the previous device. This shows a cross section of a system in which the following are sequentially combined into one system.

In FIG. 6, number 1 indicates the laser input beam to be amplified; 8 reflects the given polarization state of the laser beam irradiated into the bundle 1 through the aperture 2. A reflector is shown tilted to reflect the light. Number 19 indicates the magnetic field This magnetic field 19 is caused by a 90° polarization shift between the input and output beams. The output beam is amplified so that it is transmitted by the reflector 18. The laser beam moves 45 degrees into each fiber each time the laser beam passes through it. Number 20, which rotates the polarization plane of the laser beam, is a magnifying lens that expands the laser beam. This is a lens system that transmits the expanded laser beam 21 to the next stage amplification module. It is made to match the diameter of This expanded laser beam is first The polarized beam shown at number 23 is passed through the splitter of the polarized beam shown by . It also passes through a light beam splitter, in which the light beam is designated by the number 25. It reflects the excited light 7 from the diode array 24 which is driven by a power source.

Number 26 is the amplification of the extended fiber laser indicated by number 28. Apply an index-adjusted anti-reflective agent between the bundle and the second layer of media. The window 8 number 29 is used to rotate the polarization plane of the laser beam 21. This shows the magnetic field generated by the magnetic field.

Number 30 brings the fiber laser to the operating threshold and the amplification of the present invention. The number 31 shows the excited light shining sideways into the vessel, while the number 31 The amplified output from this amplifier 28 is sent to the next stage amplifier which is It shows.

This invention can be used for both continuous wave and pulsed laser beams. High output levels can be achieved using multiple modules or multiple modules in a chain. It can be used to generate and amplify a laser beam to be examined by wrapping it with . The present invention is useful for the industrial, medical and defense fields of powerful and high quality laser beams. This is useful when you need a system.

The actual output level that can be achieved with the present invention is achieved by phase synchronization when the area of the output aperture is small. The conditions necessary for In order to match that of water, it can be made virtually as high as possible.

The device of the present invention allows the excited light to pass through the doped aperture with good coupling efficiency. It is highly efficient because it is fully absorbed by the fiber that has been absorbed and then output again. .

The device of the present invention has both a continuous wave output mode and a pulse mode with a high repetition rate. It can be operated even if there is a difference.

When the laser beam reaches high intensity within the individual fibers of the present invention, the carp is exposed to non-linear The level of excitation of the present invention exceeds the threshold of shape, and the fundamental laser wavelength is The state of coating on the output aperture surface 2, which extracts the output of the necessary wavelength from the reflecting mirror. Depending on the You have to be careful about what happens.

The present invention has a structure for use in separating isotopes by selective excitation in the gas phase. It is possible to change the configuration.

Various modifications may be made to the subject matter described above within the spirit and gist of the invention. It is Noh.

Figure I Figure 2 Figure 5 international search report

Claims (8)

[Claims] 1. A laser oscillation system is a bundle of loop-shaped fiber lasers that are excited at the tip. , comprising: (a) a countable fiber laser bundle, the fiber laser having a The diameter of the wicks is larger than the distance between the wicks, and each loop-shaped flange The length of the fiber is several orders of magnitude longer than the output wavelength of the laser beam. Both tips of the above optically polished loop-shaped fiber laser are integrated. are stacked to form a single aperture, which in turn produces a single, partially laser beam. The one that is index-adjusted and combined with the mirror for the output that propagates. (b) a source of optically excited light with a narrow optical bandwidth, the output wave of which is The fiber length is matched to the absorption band of the fiber laser constituting the fiber bundle. , this source of light consists of an array of semiconductor diodes connected to a power supply. The excited wavelength is reflected and the other laser oscillated wavelengths are A non-reflective reflector directs the excited light inside the fiber laser bundle. The output of the laser beam is phase-synchronized so that it can enter from the end face of the laser. The fiber is connected so that the output beam of light, which is extracted through the lever reflector, travels in a straight line. – arranged at an angle with respect to the output face of the laser bundle. 2. Individual fiber lasers have a directivity greater than the spacing separating their cores from each other. 2. The system of claim 1, wherein the system has a plurality of cores of different diameters. 3. A fiber laser bundle consists of a series of smaller bundles, each with a Saito fires a phase-locked laser beam, and a single laser beam that is phase-locked as a whole. Claim 1, characterized in that the beam is emitted from the output aperture. Laser system as described in section. 4. The excitation light source consists of a phase-locked array of laser diodes. A laser system according to claim 1, characterized in that: 5. The fiber laser bundle is pumped from the side and lased up to a threshold The system according to claim 1, characterized in that: 6. A laser amplification system is a bundle of loop-shaped fiber lasers that are excited at the tip. , comprising: (a) a countable fiber laser bundle, the fiber laser having a The diameter of the wicks is larger than the distance between the wicks, and each loop-shaped flange The length of the fiber is several orders of magnitude longer than the output wavelength of the laser beam. Both tips of the above loop-shaped fiber laser are optically polished; Their tips are stacked together to form a single aperture, and this aperture , an optically polished window with good propagation efficiency, which has a laser beam and a laser beam on the output surface of the window. Anti-reflective material is coated for both wavelengths of excitation light, and the index is adjusted. what is connected. (b) a source of optically excited light with a narrow optical bandwidth, the output wave of which is The length matches the absorption band of the fiber laser that makes up the amplification fiber bundle above. The source of this light is a semiconductor diode connected to a switchable power supply. It is made up of rays, and further reflects the wavelength of the excited light to generate other wavelengths. A reflector that does not reflect the laser wavelength directs the excited light into the fiber laser bundle. The laser beam can be accessed from one end of the bundle and is phase-locked. The output beam of light extracted through this rotating reflector as the output of the beam travels straight. The fiber laser is positioned at an angle relative to the output face of the bundle, so that the (c) Polarization plane of the laser beam that is placed on the tip of the input side of the amplifier and transmitted. A coil for forming a magnetic field that rotates 90 degrees. (d) lasing it around the body of the fiber bundle which is the amplifier; A light source that excites up to the threshold of oscillation. 7. constitute an amplifier chain coupled to each other by a lens system for beam expansion, Amplified laser beam for other amplifier modules with further increased cross-sectional area Claim 6, characterized in that it includes a polarized laser beam reflecting mirror that irradiates a polarized laser beam. system. 8. The optical fiber is characterized by being doped with rare earth ions. A system according to claims 1 and 6.