JP2011129778A - Laser medium, laser amplifier, and laser device including the same, and laser amplifying method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an amplifier for a laser beam, which is optically excited with sunlight etc. <P>SOLUTION: A laser medium includes a neodium salt solution containing neodium (Nd) ions and, preferably, further contains chromium (Cr) ions. A laser amplifier uses the laser medium, and a laser device includes the laser amplifier. A laser amplifying method uses the laser medium and uses a natural solar beam as an excitation light beam source, wherein the laser medium is circulated to a laser cell while cooled by a cooling device within a predetermined temperature range and the laser cell is irradiated with excitation light from the natural solar beam. The laser amplifying method using the laser medium includes adjusting an amplification factor by adjusting the concentration of a liquid laser medium in accordance with the size of the laser cell where the laser medium is encapsulated or circulated and supplied. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a laser medium, a laser amplifier, a laser apparatus that amplifies laser light using the amplifier, and a laser amplification method, and relates to a technique for amplifying laser light with a liquid laser medium containing metal ions in an aqueous solution. More specifically, for example, a laser cell that contains an aqueous solution containing neodymium (Nd) ions, an optical system that focuses light from the sun on the laser cell, and an oscillator of laser seed light that transmits the aqueous solution in the laser cell. The present invention relates to a technique that can be disposed and amplifies laser light outdoors.
“Neodymium” is also referred to as “neodymium”, but in this specification the term “neodymium” is used in a unified manner.

Laser light has been put to practical use and is being developed widely from daily necessities to fusion reactors, utilizing its properties as a light beam with excellent directivity and convergence and properties as a high-density energy source. . For example, using CD / DVD reading, laser printer, incision scalpel, skin treatment, laser treatment equipment such as eye treatment, cutting of metal, ceramics, laser processing such as drilling, welding, etc., using the linearity of laser, Measurements using lasers that determine high-accuracy positions have been put into practical use, and attempts have been made to use them for inertial fusion using extremely high-power lasers.
Conventionally, laser devices mainly generate laser light by converting electrical energy into light (lamp lighting) or discharge form and exciting a laser medium. This method includes a plurality of energy conversion processes, and is known to have low energy efficiency (efficiency of several percent or less). The reason for this is that originally good quality electrical energy is converted into light through low-efficiency energy conversion. In this regard, if sunlight or the like is used as a light source, an excitation light source for laser oscillation can be obtained without using a low-efficiency electro-optical conversion process.

For example, sunlight is demultiplexed by a dichroic mirror, infrared light is used for temperature difference power generation by a semiconductor thermoelectric element, red light is used for solar cell power generation, and the electric power obtained from these is lasered via coolant silicone oil or water. It is used as a power source for the Peltier refrigeration element for rod cooling. Furthermore, ultraviolet light is converted into visible light by a phosphor, and the laser medium is excited together with the directly incident visible light. An apparatus for oscillating a laser (see Patent Document 1),
High-density sunlight collected in a rectangular or elliptical shape by a toroidal biconvex lens or mirror with a large diameter and different curvature, paralleled by a biconcave toroidal lens in a via barrel cooling water tank that is a biconvex toroidal surface A homogeneous, high-output, high-efficiency solar-pumped laser device (see Patent Document 2) by allowing sunlight to be incident perpendicularly to the pumped light incident surface of the solid laser medium cooled by
A laser generator that can transmit the light energy of the sun from outer space to the ground by converting it into laser light in a wavelength band that is not affected by water vapor components in the atmosphere, and making the launch weight the lightest (Patent Document 3) For example, a solar-excited laser device has been proposed.

  There are many applications that require a large laser output, for example, an output of 100 W or more, and the demand for such a large output laser is necessary as a heat source for laser processing machines such as metal welding. Laser light when used as a heat source for high-temperature processing is required to have a high average output as well as peak energy, such as when making a high-power laser processing machine, or as a plasma light source when separating metals, In order to secure a powerful energy source when creating a high temperature and high pressure field, a system combining multistage lasers is made, and a simple and powerful laser amplifier is also required.

  Conventionally, as a laser amplifier, a rod type in which the seed of laser light is incident from one direction of the rod, stimulates stimulated emission in the process of passing through the rod, and is several times the incident light when emitted from the rod Laser light is amplified by arranging a plurality of amplifiers. In addition, the crystal plane is a parallelepiped shape, and the optical path that travels through the medium (in the rod) is made long, and it propagates through the medium in a zigzag manner, eliminating thermal bias and improving efficiency and quality. Known are slab type amplifiers that can produce a high-power laser, and disk-type amplifiers that increase the diameter of the laser beam by gradually increasing the diameter of a large-diameter disk-shaped medium (rod) arranged in a Brewster angle. ing.

  For example, it is a solid laser amplifier that increases the degree of polarization by using a slab-like Nd: YAG laser crystal of the solid-state laser amplification unit whose entrance and exit surfaces are cut at a Brewster angle, and obtains a high output, Vertically polarized laser light from the solid-state laser oscillator passes through the polarizing element, rotates 45 degrees counterclockwise by the polarization rotating element, and rotates 45 degrees clockwise by the Faraday rotating element, and is incident on the laser crystal as vertically polarized light and is amplified. Is done. The laser light is reflected by a mirror, amplified by a laser crystal, rotated 45 degrees counterclockwise by a Faraday rotator, and further rotated 45 degrees counterclockwise by a polarization rotator to become horizontally polarized light, which is reflected by the polarizing element 20. An amplifier (see Patent Document 4) that can be taken out is proposed.

By the way, a linear pattern in which a substrate and a + 3-valent asymmetric rare earth ion complex containing Nd3 + are introduced into at least one of a transparent resin, a transparent inorganic material, and a transparent organic-inorganic hybrid material are placed on the substrate. And amplifying spontaneous emission from excitation light having an intensity of 0.05 mJ or more irradiated on the linear pattern, and amplifying the amplified spontaneous emission in the linear pattern and emitting from the end face of the linear pattern A laser oscillation device is known (see claims 1 and 3 of Patent Document 5).
However, conventionally, there has been no laser medium made of an aqueous neodymium salt solution containing neodymium (Nd) ions. Non-Patent Document 2 states that “Neodymium (III) is known as an emitter of an Nd (III) -YAG laser, and its excitation energy in the near infrared region is close to energy transfer to OH and CH vibrations. There is also a statement that luminescence is never obtained in an environment such as water, an organic solvent, or plastics because it rapidly deactivates with energy transfer between Nd (III) ions.

JP 2008-210999A JP 2007-227406 A JP 2002-33537 A JP-A-9-181378 JP 2007-251186 A

Authored by Junpei Kanno and Watanabe Urano, “Development of Elemental Technology for 1kW Class Laser System for Demonstration of Space Solar Pumped Lasers” IEICE Technical Report TECHNICAL REPORT OF IEICE SPS2009-02 (2009-04 p5-12) Liang Munenori and Yuji Wada, “Neozeolitic as a Rare Earth Light-Emitting Element Host-Controlling Near-Infrared Photoluminescence” (2004 P2-10)

  A solid laser medium is mainly used for the oscillation and amplification of conventional laser light. During operation, the temperature of the laser medium rises and the stable oscillation is hindered, so cooling is necessary to suppress thermal distortion of the laser medium. Development of efficient and efficient cooling technology was required. In addition, the solid laser medium may need to change the density of the solid laser medium depending on the characteristics of the required laser beam. To do so, it is necessary to create and replace the material that oscillates the necessary laser beam. was there. However, it is not easy to produce a solid-state laser medium, and it is difficult to prepare various media in advance from the viewpoint of cost and work load. Furthermore, since the solid laser medium needs to be uniform, it is very difficult to increase the size of the solid laser medium.

  The present invention has been made in view of the various problems of the prior art as described above, and the object of the present invention is to easily increase the size of the amplifying device and to efficiently increase the amplification factor. An object of the present invention is to provide a laser device capable of obtaining optical excitation, a laser amplifier constituting the laser device, a laser medium, and the like. In addition, an attempt is made to provide a laser device that can suppress an increase in manufacturing cost, power consumption, and heat generation and realize a stable pulse oscillation operation, a laser amplifier that constitutes the laser device, a laser medium, and the like. To do. It is another object of the present invention to provide a laser apparatus capable of adjusting pulse energy as desired with a simple configuration, a laser amplifier, a laser medium, and the like.

A method has been devised that converts solar energy into laser light with high efficiency, increases the concentration of energy due to the coherent nature of the laser, achieves high energy density, and converts it into hydrogen or an energetic chemical compound. At this time, conversion efficiency of solar energy into a laser becomes a problem. Conventionally, there has been a sunlight-excited laser as one means of using visible light, and it has been reported that when a YAG crystal doped with Cr3 + ions and Nd3 + ions is excited with sunlight, 1064 nm laser light can be extracted with an efficiency of 40%. The present inventor paid attention to the fact that Nd ions oscillating in a solid state may exhibit a laser action (amplification or oscillation) in a liquid. The invention has been reached.
Nd3 + ions exhibit absorption in a wavelength band of 900 nm or less. In order to efficiently convert sunlight into laser light, it is advantageous that light having a wider range of wavelengths can be used as excitation light, but Nd can absorb light having a longer wavelength than Cr or Ti. The laser action was examined focusing on Nd ions having such characteristics. In addition, Cr ions exhibit large absorption in the visible light region from ultraviolet rays, and their excitation levels are slightly higher in energy level than the laser upper levels of Nd ions. Moreover, since the lifetime is as long as several milliseconds, it is considered that energy may be transferred from Cr ions to Nd ions by collision of Cr ions and Nd ions. Non-Patent Document 1 reports this process in a solid.
The present inventor has found that the problems of the prior art can be solved by using an aqueous solution of a metal salt, and has found out the possibility of laser light amplification technology using an aqueous solution of a metal salt by accumulating ingenuity. By further research and development, a liquid laser medium, a laser amplifier using the medium, a laser cell containing the medium, and an excitation beam for exciting ions by irradiating the ions in the cell with light. The present invention has led to an invention relating to a laser amplifier provided with a laser source oscillator that transmits a light source and an aqueous solution in a laser cell.

The present invention for solving the above problems is summarized as the following laser medium.
[1] A laser medium comprising a neodymium salt aqueous solution containing neodymium (Nd) ions.
[2] The laser medium according to [1], wherein the neodymium ion concentration is 0.2 to 28% by weight.
[3] The laser medium according to [1] or [2], further comprising chromium (Cr) ions.
[4] The laser medium according to [3], wherein the chromium ion concentration is 0.01 to 9% by weight.

The gist of the present invention is the following laser amplifier.
[5] A laser amplifier using the laser medium according to any one of [1] to [4].
[6] The laser amplifier according to [5], wherein the laser medium is sealed or supplied to the laser cell.
[7] The laser amplifier according to [6], further comprising: an optical system that irradiates the laser cell with excitation light from an excitation light source from a predetermined direction.
[8] A laser cell in which a laser medium is circulated and supplied, an optical system that enters excitation light from an excitation light source into the cell from a predetermined direction, and a circulation device that circulates and supplies the laser medium to the cell. [7] The laser amplifier according to [7].
[9] The laser amplifier according to [8], wherein the circulation device includes a solution tank having a deaeration pump, and a pump that sucks a laser medium in the laser cell and sends it to a container tank.
[10] In the laser cell, the portion where the excitation light is incident is made of a material that transmits light of 300 to 900 nm, and the portion where the laser light passes is made of a material that transmits light of 1000 to 1100 nm [6] ] The laser amplifier according to any one of [9].
[11] The laser amplifier according to [10], comprising a cooling device that is made of quartz, glass, or plastic resin and that cools the laser medium to a predetermined temperature range.
[12] The laser amplifier according to any one of [7] to [11], wherein the excitation light source is selected from natural sunlight, artificial light, and light obtained by removing light having a wavelength of 900 nm or more from these light.

The gist of the present invention is the following laser device.
[13] A laser device provided with the laser amplifier according to any one of [5] to [12].

The gist of the present invention is the following laser amplification method.
[14] A laser amplification method using the laser medium according to any one of [1] to [4], wherein the excitation light source is natural sunlight, and the laser medium is brought into a predetermined temperature range by a cooling device. A laser that circulates in a laser cell made of quartz, glass, or plastic resin while cooling and irradiates the laser cell with excitation light from natural sunlight from a direction substantially perpendicular to the laser seed light that passes through the laser cell. Amplification method.
[15] A laser amplification method using the laser medium according to any one of [1] to [4], wherein the liquid medium is a liquid laser medium according to a size of a laser cell in which the laser medium is enclosed or circulated. A laser amplification method, wherein the amplification factor is adjusted by adjusting the concentration.

  According to the present invention, it is easy to increase the size of an amplification device, and it is possible to provide a laser device that enables optical excitation to obtain a large amplification factor efficiently, a laser amplifier that constitutes the laser device, a laser medium, and the like. Also, to provide a laser device capable of suppressing an increase in manufacturing cost, power consumption, and heat generation and realizing a stable pulse oscillation operation, a laser amplifier constituting the laser device, a laser medium, and the like. Can do. Furthermore, it is possible to provide a laser device that can adjust the pulse energy as desired with a simple configuration, a laser amplifier that constitutes the laser device, a laser medium, and the like.

More specifically, the present invention provides the following effects.
(1) Since the laser medium is an aqueous solution, it is safe and easy to handle, the installation location of the laser device is not limited, and an increase in manufacturing cost, power consumption, and heat generation can be suppressed.
(2) Since the liquid of the laser medium is water having a large heat capacity, the temperature rise during amplification is moderate.
(3) Since the size of the cell and the diameter of the condensing lens can be easily increased, it is easy to increase the size of the amplifying device, and it is possible to perform optical excitation that efficiently obtains a large amplification factor.
(4) By circulating the aqueous solution, photoexcitation with a new laser medium is always possible, and the material is not deteriorated and easy to handle.
(5) It is easy to control the temperature of the laser medium by adding a device for cooling the aqueous solution.
(6) The laser medium can be easily produced and the concentration can be adjusted, and an optical amplification effect according to desired conditions can be exhibited.
(7) When the size of the laser cell is increased, the transmittance can be easily adjusted by adjusting the concentration.
(8) A laser medium can be easily produced in a short time by simply dissolving a predetermined amount of a water-soluble metal salt in water.
(9) Even if the temperature of the aqueous solution in the laser cell changes, the transmittance of the laser light hardly changes and stable amplification is possible.
(10) It is environmentally friendly and enables amplification of laser light using sunlight obtained anywhere as an energy source. In addition, since the laser medium is an aqueous solution and does not contain an organic solvent, the laser medium is not altered and is suitable for long-term operation under sunlight.

It is a graph which shows the transmittance | permeability characteristic of chromium sulfate (3+) aqueous solution and neodymium sulfate (3+) aqueous solution. It is a graph which shows the relationship between a metal ion concentration and the transmittance | permeability. It is a graph which shows the transmittance | permeability characteristic of chromium 1.0% and neodymium 2.0% liquid mixture. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram of an amplification factor measurement experimental apparatus according to Example 1. It is a graph which shows the laser amplification factor with respect to the condensing illumination intensity (light quantity of a cell surface) of an artificial solar lamp. It is a graph which shows the amplification factor of 1064 nm with respect to artificial solar lamp illumination intensity (before light collection). It is a graph which shows the gain of 1064nm which considered absorption. The gain and gain estimated from the experimental results are shown (the solar intensity is the light intensity on the surface of the Fresnel lens). 6 is a schematic configuration diagram of a laser amplifier according to Embodiment 2. FIG. It is drawing explaining the optical system of FIG. It is a general | schematic whole block diagram of the laser amplifier provided with the laser amplifier which concerns on Example 2. FIG. It is a graph which shows the laser signal waveform which passed Nd3 + (2.0%) aqueous solution. It is a graph which shows the laser signal waveform which passed the mixed aqueous solution of Nd3 + (1.0%) and Cr3 + (0.25%). It is a graph which shows the laser signal waveform which passed the mixed aqueous solution of Nd3 + (2.0%) and Cr3 + (1.0%). It is a graph which shows the amplification factor in Nd3 + (2.0%) aqueous solution. It is a graph which shows the amplification factor of the mixed aqueous solution of Nd3 + (1.0%) and Cr3 + (0.25%). It is a graph which shows the laser transmission signal waveform of the mixed aqueous solution of Nd3 + (2.0%) and Cr3 + (1.0%). It is a graph which shows the relationship between the temperature of the mixed aqueous solution of Nd3 + (2.0%) and Cr3 + (0.5%), and a 1064 nm transmission signal intensity | strength. It is a graph which shows the relationship between the temperature of the mixed aqueous solution of Nd3 + (2.0%) and Cr3 + (1.0%), and a 1064 nm transmission signal intensity | strength. It is a graph which shows the relationship between sunlight intensity and the absorptivity of Nd3 + (2.0%) aqueous solution and the mixed aqueous solution of Nd3 + (2.0%) and Cr3 + (1.0%).

  The present invention relates to a laser cell containing an aqueous solution containing an aqueous solution of neodymium (Nd) ions, an excitation light source for irradiating the ions in the cell with light to excite the ions, and transmitting the aqueous solution in the laser cell. A laser light amplifier provided with a laser oscillator that oscillates laser seed light, wherein a laser amplification action is performed by irradiating light to an aqueous solution of a metal salt. Sunlight can also be used as the excitation light source. The solar spectrum on the earth's surface is on the longer wavelength side than 280 nm, and about 50% of light is expected with ultraviolet rays, visible rays, and infrared rays of 950 nm or less. The intensity of sunlight on the ground surface is 1 kW / m 2. If 50% (500 w / m 2) of visible light is used, energy of 100 J / s can be used even if the efficiency is 20%. The present invention is also an excellent technique in terms of effective use of sunlight.

[Characteristics of metal ion aqueous solution]
An aqueous solution containing neodymium ions is an aqueous solution of neodymium salts such as neodymium carbonate, neodymium chloride, neodymium bromide, neodymium iodide, neodymium nitrate, neodymium perchlorate, neodymium bromate, neodymium acetate, neodymium sulfate, neodymium phosphate, etc. Used.
As the aqueous solution containing chromium ions, an aqueous solution of a chromium salt such as chromium carbonate, chromium chloride, chromium bromide, chromium iodide, chromium nitrate, chromium perchlorate, chromium acetate, chromium sulfate, or chromium phosphate is used.
Regarding the concentration of the metal ion aqueous solution constituting the liquid laser medium, a suitable concentration range is experimentally determined by first examining the absorbance data of the aqueous solution.
The preferred concentration of the aqueous metal ion solution varies depending on the size of the laser cell, but in general, the neodymium ion concentration of the aqueous solution is preferably 0.2 to 28% by weight.
Here, the upper limit of 28% by weight is the neodymium ion concentration determined from the solubility of neodymium chloride.
The basis for the lower limit of 0.2% by weight is as follows.
Looking at d and e (wavelength with large absorption) in FIG. 2, the transmittance per cm is about 60% at a concentration of 0.5%. When the excitation length (in the depth direction) is 2 cm, the transmittance is 36% (= 0.6 * 0.6 * 100), and the transmittance is almost the same as that when the excitation length is 1 cm at a concentration of 1%. Considering an actual excitation length of 5 cm, the transmittance is 80% (approximately 0.2% of the concentration in the case of d and e in FIG. 2), and the overall transmittance is about 33%. Since this corresponds to (cell length of 1 cm and Nd concentration of 1%), this value was set as the lower limit.

The aqueous solution containing neodymium ions preferably contains chromium (Cr) ions. This is because the absorption rate of the solution is increased as shown in FIG. In general, the chromium ion concentration is preferably 0.01 to 9% by weight, more preferably 0.5 to 2.0% by weight, although it varies depending on the size of the laser cell.
Here, the upper limit of 9% by weight is the chromium ion concentration determined from the solubility of chromium chloride.
The basis for the lower limit of 0.1% by weight is as follows.
Similar to the neodymium ion concentration, the lower limit was set from FIG. 2a and FIG. 13 (Cr addition amount 0.25%).
In FIG. 2A, a Cr concentration of 1% (transmittance of 0%), a Cr concentration of 0.5% (transmittance of 10%), and a Cr concentration of 0% (transmittance of 100%) are approximated by a second-order polynomial approximation. The transmittance when the Cr addition amount of 0.25% in which the amplification effect was confirmed is 45%. When the excitation length is 5 cm, the Cr concentration at which the transmittance is 45% is 0.06%. Confirmation of the amplifying action at a low concentration was not performed below the mixed concentration of Nd3 + (1.0%) and Cr3 + (0.25%), so 0.01% of the same order was set as the lower limit.

Pure water has no absorption below 800 nm and absorbs at 973 nm. However, since the transmittance around 1050 nm is about 90%, it is excellent in the transmittance of laser light having this wavelength. In order to examine the transmittance of an aqueous solution of neodymium and chromium, a predetermined concentration of sulfate was dissolved in water and the transmittance was examined. The result shown in FIG. 1 was obtained. From FIG. 1, it was found that the chromium aqueous solution has absorption at 600 nm and 415 nm, and the neodymium aqueous solution has absorption at 864 nm, 794 nm, 740 nm, 576 nm, 521 nm, and 353 nm.
It was also found that the transmittance of chromium and neodymium tended to decrease with increasing concentration. That is, the relationship between the transmittance and the solution concentration of an aqueous solution containing chromium and an aqueous solution containing neodymium is as shown in FIG. Moreover, the transmittance shown in FIG. 3 was shown for an aqueous solution (1.0% Cr, 2.0% Nd mixed aqueous solution) containing chromium and neodymium simultaneously.

From the above results, it became clear that the mixed aqueous solution of chromium and neodymium absorbs light in the range of 300 to 900 nm. As for chromium, there was little absorption at 650 to 900 nm, and no significant difference was observed between 1.0% and 2.0% at 600 nm or less where the absorption was large. As for neodymium, there are absorption lines at 740 nm, 794 nm, and 864 nm in the wavelength range of 650 to 900 nm where chromium does not exhibit absorption, the amount of absorption increases with concentration, and absorption tends to saturate at a concentration of 2.0% or more. It is in.
In order to efficiently absorb near-infrared rays from ultraviolet rays, the chromium ion concentration in the aqueous solution is preferably 0.5 to 1.5% by weight, and the concentration of neodymium ions in the aqueous solution is 0.4 to 2.5% by weight was found to be a preferred range.
Further, it is preferable to increase the transmittance by adjusting the concentration when the size of the laser cell is increased.

  In order to prepare the aqueous metal ion solution of the present invention, it is sufficient to dissolve a predetermined amount of metal salt in water. Any water can be used as long as it is transparent without impurities such as distilled water and deionized water. The metal salt is selected from water-soluble salts capable of preparing an aqueous solution in which about 0.2 to 5% by weight of the metal salt is completely dissolved, and examples thereof include sulfates and chlorides.

[Excitation light source]
The excitation light source is preferably selected from natural sunlight, artificial light, and light obtained by removing light having a wavelength of 900 nm or more from these light rays, but includes a lot of light having a wavelength of 900 nm or less. Any light source can be used as the light source, but for example, natural sunlight, an artificial solar light, or another light source is used. With these light sources, infrared light of 900 nm or more does not absorb Nd3 + or Cr3 + ions and does not contribute to excitation of the laser medium. Also, since it includes the laser oscillation wavelength of Nd3 + ions, it self-oscillates and loses energy. It is unsuitable for use, and since it is a heat ray, the solution in the laser cell may be heated excessively. Therefore, it is preferable to use it after cutting with a filter or the like. Further, since it is necessary to concentrate a strong light beam on the laser cell, it is desirable to collect and irradiate the light with a convex lens (for example, Fresnel convex lens). The excitation light beam is preferably irradiated so as to be perpendicular to the optical axis of the laser seed light.

[Laser cell]
A laser cell (hereinafter also simply referred to as “cell”) in which a metal salt aqueous solution is stored is made of a material that can transmit a laser seed light and an excitation light source such as artificial sunlight or natural sunlight. Specifically, plastics such as quartz glass, glass, and polyacrylate are exemplified. Since the neodymium aqueous solution in the laser cell can be cooled to, for example, about 40 ° C. by circulating cooling, plastics having low heat resistance can be used. The size of the laser cell is appropriately selected according to conditions such as the type of laser light, the amplification factor, the amount of aqueous solution required in the cell, and the temperature control of the cell. For example, an analytical quartz cell, an inner diameter of 19 mm, Examples include a quartz cell (CV-Q-100; manufactured by Ocean Optics) having an outer diameter of 22 mm and a length of 102 mm. When circulating cooling is not performed, the cell is made of a heat-resistant material because intense light rays are concentrated and the temperature cannot be increased. However, even in a heat-resistant cell, if water vapor is generated by boiling water in the cell, voids are generated in the cell and the uniform passage of laser light is hindered. It is preferable to control so that it does not occur.
Utilizing the characteristic that the laser amplification medium of the present invention is a liquid, an aqueous solution that has become hot in the cell is taken out of the cell, cooled, and then circulated through the cell for reuse. The circulation device supplies a laser medium to the cell, collects the laser medium supplied to the cell, and supplies the laser medium to the cell again. The cell is equipped with an aqueous solution inlet and outlet, and the aqueous solution in the storage tank is circulated to the cell through the inlet and outlet, allowing easy maintenance of the aqueous solution in the cell. To be done. In the present invention, since the liquid is used as the laser amplification medium, it is possible to solve the cooling problem in the conventional apparatus using the solid laser amplification medium by a simple method.
The aqueous solution storage tank is provided with a cooling device and / or a deaeration pump. The cooled aqueous solution controls the inside of the cell to an optimum temperature, and a deaeration pump is installed to allow gas to enter the cell. Try not to mix.

  As described above, the present invention relates to a laser cell containing an aqueous solution containing neodymium (Nd) ions, an excitation light source for exciting the ions by irradiating the ions in the cells, and the laser cell. This is a laser light amplifier provided with an oscillator that oscillates a laser seed beam that transmits an aqueous solution of Nd3 +. The aqueous solution contains Nd3 + or Cr3 + and Nd3 + (for example, an aqueous solution in which chromium sulfate or neodymium sulfate is dissolved). However, the present invention relates to an apparatus that performs laser amplification by irradiating a cell with light, and the wavelength of laser light that serves as seed light to be amplified is preferably approximately 1040 to 1080 nm, for example, 1060 and 1047 nm. .

In the present invention, since an aqueous solution is used as a laser beam amplification medium, the temperature of the aqueous solution in the cell where light energy is concentrated rises to the boiling point, and is always cooled to an appropriate temperature so that bubbles are not generated. Is preferably supplied to the cell and used as a laser medium. Cooling may be either forced cooling or natural cooling. A large amount of aqueous solution should be stored in the storage tank and circulated to the cell, but it is preferable to install a deaeration device in the storage tank to prevent the generation of bubbles and the flow into the laser cell. . Since bubbles are generated when the aqueous solution is pumped and circulated, it is preferable to circulate the aqueous solution by sucking it with the pump. Even if the temperature of the aqueous solution changes, the light transmittance is hardly affected, but the laser cell can be made of a non-heat-resistant material by keeping the temperature of the aqueous solution below a certain level.
In addition, a filter or wavelength selective mirror that cuts infrared rays is arranged in the condensing system so that the aqueous solution in the cell is not as hot as possible so that light of 900 nm or less is condensed and irradiated on the aqueous solution (laser medium). It is preferable to reduce the temperature rise of the aqueous solution. From the practical aspect, it is desirable to stabilize the output by saturation amplification of the solar light pumped laser medium.

  The solar light excitation amplification system of the present invention can supply all energy to be used from solar energy. For example, a laser beam oscillator that becomes seed light to be amplified, a liquid feed pump for an aqueous solution to a cell, a deaeration pump, and an aqueous solution cooling device are driven by storing electricity generated by a solar cell in the battery. It is preferable to use an electrical oscillator as a laser beam oscillator to be amplified seed light.

  Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the examples.

In Example 1, a light amplification test using an artificial solar lamp was performed. A schematic configuration diagram of the experimental apparatus according to Example 1 is shown in FIG.
A laser oscillator capable of irradiating a mixed aqueous solution of neodymium sulfate and chromium sulfate (Nd: 2.0 wt%, Cr: 1.0 wt%) with a light source 1 and irradiating a 1064 nm pulsed Nd: YAG laser beam The amplification factor was measured by 5.
The laser light emitted from the laser oscillator 5 passes through the polarization beam splitter (PBS) 6 and the infrared transmission filter 7, and then enters the metal salt aqueous solution of the laser cell 4, and the amplified laser light has a transmission wavelength. After passing through the 1050 ± 5 nm transmission filter 8, the light is received by the light receiver 9, and the light intensity is measured by the oscilloscope 10.
An optical filter 3 having a different transmittance in the wavelength range of 300 nm to 900 nm was disposed between the convex lens 2 and the aqueous solution cell 4 to change the irradiation intensity of the artificial solar lamp to the aqueous solution cell. Further, in order to block the leakage light of the excitation lamp from the laser oscillator 5, an infrared transmission (visible light and ultraviolet ray cut) filter 7 having a wavelength of 900 nm or more is disposed between the laser oscillator 5 and the aqueous solution cell 4.

The configuration of each device used in the optical amplification test is as follows.
The light source 1 is a direct-current-lit artificial solar lamp (100 W, XC-100; manufactured by Celix).
The convex lens 2 is an acrylic (Acrylite # 000; manufactured by Mitsubishi Rayon Co.) Fresnel lens having a focal length of 30 cm. The light intensity on the Fresnel lens surface of artificial solar lighting measured with a sunshine meter (ML020V; manufactured by Eiko Seiki Co., Ltd.) is 16 Wh / m 2, and the intensity on the cell surface is 1.8 kWh / m 2.
The optical filter 3 is a reflective ND filter manufactured by Sigma Koki Co., Ltd.
The aqueous solution cell 4 is a quartz cell (T-23-UV-10; manufactured by Nippon Quartz Glass Co., Ltd.), and its optical path length is 1 cm. In order to examine the amplification factors of different wavelengths, the same measurement was performed using Nd: YLF (oscillation wavelength: 1047 nm, Explorer; manufactured by Spectra Physics).
The laser oscillator 5 uses the Ultra of Cantel, and the polarization beam splitter 6 is 05BC15PH. 9 was used.
The infrared transmission filter 7 was Hoya Glass IR-85, and the transmission filter 8 was Andover 105FS10-50.
The photoreceiver 9 was a pin photodiode S1722-01 manufactured by Hamamatsu Photonics, and the oscilloscope 10 was a TDS3054B manufactured by Tektronix.

FIG. 5 shows the condensing irradiation intensity (light intensity on the surface of the aqueous solution cell condensed by the convex lens) of the artificial solar illumination and the amplification factor of the laser light. From the figure, it was confirmed that the amplification factor of the laser worker increased as the irradiation intensity of artificial solar illumination increased. FIG. 6 shows the relationship of the amplification factor with respect to the irradiation intensity of the artificial solar lamp before focusing.
As a result of the above experiment, there is a correlation between an increase in the amount of light emitted from the light source 1 and an increase in the laser amplification factor. Thus, it was confirmed that the laser amplification action was obtained by the aqueous solution in the aqueous solution cell 4.

  By the way, the aqueous solution shows an absorption of about 10% at the experimental laser wavelength. Therefore, the true amplification as a laser needs to exceed this absorption. FIG. 7 shows the amplification factor considering the absorption of the aqueous solution. In this experiment, the maximum amplification factor was 0.99. When the amplification factor is 1 or more, the laser beam can be amplified. Therefore, an estimated value of the amplification factor was obtained by calculation based on the data in this experiment. FIG. 8 shows a calculation result assuming that sunlight is condensed to 1 cm 2 using a Fresnel lens (focal length 50 cm) having a diameter of 50 cm as calculation conditions. In the calculation, the amplification factor is 1 when the sunlight intensity is 1 Wh / m 2, and the amplification factor of 110 times can be expected at 1 kWh / m 2 in fine weather. Actually, with laser, when the intensity increases, the tendency of saturation appears, so the amplification factor can be expected to be only about 70%. However, if the saturation phenomenon of the amplification factor is used, a laser beam having a stable output can be extracted. FIG. 8 shows the gain and gain estimated from the experimental results in relation to the sunlight intensity on the surface of the Fresnel lens.

In Example 2, a light amplification test was performed using a sunlight concentrating laser amplification device.
In this apparatus, sunlight is collected by the lenses A21 to C23, passes through the infrared absorption filter 11, and is then applied to the laser cell 4. On the other hand, the laser light emitted from the YAG laser oscillator 5 is transmitted through the metal salt aqueous solution in the laser cell 4 through the PBS 6, the infrared transmission filter 7 and the YAG laser attenuation filter 12, and is received through the interference filter 8. The oscilloscope 10 observes the electric signal generated there.

The configuration of the laser amplifier of this embodiment is as shown in FIGS. (In FIG. 9, the lens B22 and the lens C23 are not shown.)
The lens A21 is a Fresnel convex lens having an effective diameter of 500 mmφ and a focal length of 500 mm, the lens B22 is a Fresnel concave lens having an effective diameter of 170 mmφ and a focal length of −76 mm, and the lens C23 is a Fresnel cylindrical lens having an 83 × 102 mm focal length of 76 mm. .
The infrared absorption filter 11 is a heat ray absorption filter HA-50 manufactured by Hoya Glass Co., Ltd., which transmits light of 300 nm to 900 nm and absorbs and blocks heat rays of 900 nm or more. It was arranged between the Fresnel cylindrical lens C23 and the laser cell 4.
The condensing area of sunlight at the position of the laser cell 4 is about 7 cm in the horizontal direction and about 3 cm in the vertical direction. Since this device is not provided with a solar tracking device, the light collection area was widened and the experiment time was lengthened.

The YAG laser oscillator 5 uses the Ultra of Cantel, and PBS6 is 05BC15PH. 9 was used.
The infrared transmission filter 7 was ITF-50S-85IR manufactured by Sigma Koki Co., Ltd., and the YAG laser attenuation filter 12 was ANDY-50S-50 manufactured by Sigma Koki Co., Ltd.
The interference filter 8 was Andover 105FS10-50, and the light receiving element 9 was Hamamatsu Photonics pin photodiode S1722-01. The oscilloscope 10 used was Tektronix TDS3054B.

  The laser cell 4 is a quartz cell having an inner diameter of 19 mm, an outer diameter of 22 mm, and a length of 26 mm. The laser cell 4 is provided with an aqueous solution inlet and outlet. However, for the data collection shown in FIGS. 12 to 15 described later, the analysis cell having an optical path length of 1 cm used in Example 1 was used. The reason is to compare with the data of the artificial solar lamp according to Example 1.

FIG. 11 is a schematic overall view of a laser amplification device equipped with the above laser amplifier. (In FIG. 11, the lens B22, the lens C23, the PBS 6, and the filters 7 and 12 are not shown.)
This laser amplifying apparatus is constructed so that all electric power can be obtained from solar energy. Necessary electric power is stored in the storage battery from the electric power generated by the solar cell and used for a cooler, a liquid pump, a deaeration pump, and a laser oscillator. Light energy necessary for amplifying the laser light is collected by the Fresnel lens 21. Obtained by sunlight. This laser amplifier can be operated with solar energy alone.

The amplification test using the laser amplification apparatus was performed on a sunny summer day.
The laser medium is a 2.0 wt% neodymium salt aqueous solution of Nd3 +. This aqueous solution of neodymium salt was prepared by obtaining a Nd2 (SO4) 3.8H2O reagent (molecular weight: 720, Nd of 288) and putting 0.53 g of the reagent in 10 g of pure water. (Reference: 0.53 * (288/720) / (10 + 0.53) * 100 = 2%)
FIG. 12 shows the results of an amplification test using a 2.0 wt% metal salt aqueous solution of Nd3 + having an optical path length of 1 cm. The amount of solar radiation was 0.72 kWh / m 2 on the lens A surface and 32 kWh / m 2 on the cell surface. As can be seen from the results of FIG. 12, the amplification factor when irradiated with sunlight was 1.47 times.

An optical amplification test was performed using the same laser amplification apparatus as in Example 2.
The laser medium is an aqueous metal salt solution containing 1.0% by weight of Nd3 + and 0.25% by weight of Cr3 +. Among these metal salt aqueous solutions, a neodymium salt aqueous solution was prepared by the method of Example 2, and a chromium salt aqueous solution obtained a reagent of Cr2 (SO4) 3 (molecular weight: 392, of which Cr was 104), and 10 g of pure water. The sample was prepared by adding 0.095 g of reagent. (Reference: 0.095 * (104/392) / (10 + 0.095) * 100 = 0.25%)
In a test using an aqueous metal salt solution containing 1.0% by weight of Nd3 + and 0.25% by weight of Cr3 +, the solar radiation was irradiated to the cell at 0.77 kWh / m2 on the lens A surface (34 kWh / m2 on the cell surface). As a result, an optical amplification factor of 1.69 times was obtained as compared with the case of shielding light. The result is shown in FIG.

  An optical amplification test was performed using the same laser amplification apparatus as in Example 2. In a test using a mixed aqueous solution containing 2.0% by weight of Nd3 + and 1.0% by weight of Cr3 + produced in the same manner as in Example 3, the amount of solar radiation was 0.77 kWh / m2 on the lens A surface (34 kWh / m2 on the cell surface). The light amplification factor was 2.42 times that of the case where light was blocked by irradiating the cell with sunlight. The result is shown in FIG.

  FIG. 15 (Nd3 + 2.0 wt% aqueous solution) and FIG. 16 (Nd3 + 1.0 wt% and Cr3 + 0.25 wt%) show the relationship between the input laser beam intensity (Input) and the output intensity (Output). When the laser intensity is increased, the tendency that the amplification factor (Amp) reaches saturation is observed, and it is considered that the laser light output by the amplification is stabilized. In a mixed aqueous solution of Nd3 + 2.0% by weight and Cr3 + 1.0% by weight, the amplification factor could not be measured because the temperature rose and boiled in a short time. An example of the signal waveform over time is shown in FIG. Immediately after irradiation from the top, cooling / re-irradiation, continuous irradiation (boiling), and light shielding are illustrated in this order. When the sunlight was continuously irradiated, the amplification factor decreased. When the sample was cooled and shielded from light, the amplification factor recovered when it was irradiated again, but it did not return to the original state. The cause of these is unknown.

  When the transmittance at a wavelength of 200 to 900 nm with respect to the temperature of the Nd and Cr mixed aqueous solution was measured, the absorption did not change with temperature in this wavelength region within a temperature range of 25 to 75 ° C.

  The temperature of the mixed aqueous solution and the transmittance of 1064 nm laser light were measured. FIG. 18 and FIG. 19 show the received light signal intensity when a mixed aqueous solution having an optical path length of 1 cm is allowed to pass a 1064 nm laser beam by adjusting the temperature by hot water bathing. No significant difference in signal intensity due to temperature change was observed.

  The laser amplification device according to the present invention is not limited to the enlargement of the laser cell, and the condensing device is a laser because there are few technical restrictions in adopting the enlargement or continuation of many devices. The amplification device can be easily increased in size. Therefore, it is widely used for the construction of high-power laser equipment, and is also suitable for high peak power laser equipment, high average power laser equipment, ultrashort pulse laser equipment, waste treatment and other high-temperature treatment, high-density plasma source, laser A wide range of applications such as nuclear fusion can be expected. The laser amplifier according to the present invention enables construction of a laser system using sunlight as an energy source.

DESCRIPTION OF SYMBOLS 1 Light source 2 Convex lens 3 ND filter 4 Laser cell (aqueous solution cell)
5 Laser oscillator 6 Polarization beam splitter (PBS)
7 Infrared transmission filter 8 Interference filter 9 Light receiver (light receiving element)
DESCRIPTION OF SYMBOLS 10 Oscilloscope 11 Infrared absorption filter 12 Absorption type fixed ND filter 13 for YAG Liquid feed pump 14 Deaeration pump 15 Cooler 16 Storage battery 17 Solar cell 21 Lens A
22 Lens B
23 Lens C

Claims (15)

  A laser medium comprising an aqueous neodymium salt solution containing neodymium (Nd) ions.   The laser medium according to claim 1, wherein the neodymium ion concentration is 0.2 to 28% by weight.   The laser medium according to claim 1, further comprising chromium (Cr) ions.   The laser medium according to claim 3, wherein the chromium ion concentration is 0.01 to 9% by weight.   A laser amplifier using the laser medium according to claim 1.   6. The laser amplifier according to claim 5, wherein the laser medium is sealed or circulated and supplied to the laser cell.   The laser amplifier according to claim 6, further comprising an optical system that irradiates the excitation light from the excitation light source into the laser cell from a predetermined direction.   A laser cell in which a laser medium is circulated and supplied, an optical system that makes excitation light from an excitation light source incident into the cell from a predetermined direction, and a circulation device that circulates and supplies the laser medium to the cell are provided. The laser amplifier according to claim 7.   9. The laser amplifier according to claim 8, wherein the circulation device includes a solution tank having a deaeration pump and a pump that sucks a laser medium in the laser cell and sends it to a container tank.   10. The laser cell is configured such that a portion where excitation light is incident is made of a material that transmits light of 300 to 900 nm, and a portion where laser light passes is formed of a material that transmits light of 1000 to 1100 nm. The laser amplifier according to any one of the above.   The laser amplifier according to claim 10, comprising a cooling device made of quartz, glass, or plastic resin, for cooling the laser medium to a predetermined temperature range.   The laser amplifier according to any one of claims 7 to 11, wherein the excitation light source is selected from natural sunlight, artificial light, and light obtained by removing light having a wavelength of 900 nm or more from these light.   13. A laser device provided with the laser amplifier according to claim 5. A laser amplification method using the laser medium according to any one of claims 1 to 4, wherein an excitation light source is natural sunlight,
The laser medium is circulated in a laser cell made of quartz, glass, or plastic resin while being cooled to a predetermined temperature range by a cooling device, and from natural sunlight to the laser cell from a direction substantially perpendicular to the laser seed light passing through the laser cell. A laser amplification method characterized by irradiating with excitation light.   5. A laser amplification method using the laser medium according to claim 1, wherein the concentration of the liquid laser medium is adjusted in accordance with a size of a laser cell in which the laser medium is enclosed or circulated. A method for amplifying a laser, characterized in that the amplification factor is adjusted by the method described above.