JP2008147394A - Laser medium for dye laser, dye laser oscillating device, and laser light - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dye laser medium having a slow deterioration rate without affected by a nonflammable solvent even though the liquid can be cooled in circulation, and to provide a device for oscillating the laser light using it. <P>SOLUTION: The laser medium for the dye laser includes a colloidal dispersion substance of a silica particle including a fluorescent dye. The dye laser oscillating device uses the laser medium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser medium for dye laser, a dye laser oscillation apparatus, and laser light, and more specifically, a laser medium for dye laser using a colloidal dispersion of silica particles containing a fluorescent dye, and dye laser oscillation using the laser medium. The present invention relates to an apparatus and laser light emitted from the dye laser oscillation apparatus.

Conventionally, dye lasers using organic fluorescent dyes as a laser medium have the advantage of a high degree of freedom in design of the oscillation wavelength, but compared with lasers of the type that use lanthanide ions or rare gas gas atoms as the laser medium, There was a problem that the deterioration was likely to proceed due to the temperature rise caused by the excitation light. In order to suppress the deterioration of the fluorescent dye molecules, conventionally, in a high-power type laser oscillation device, a method is adopted in which the fluorescent dye molecules are dispersed in an appropriate medium and the solution is circulated and cooled. Furthermore, as described in Patent Document 1, a fluorescent dye solution is jet-jetted at a portion where laser oscillation is performed to shorten the time of exposure to excitation light as much as possible.
Conventionally, dye lasers basically perform pulse oscillation. Compared with CW excitation, the intensity of excitation is about two orders of magnitude higher in the pulse laser, and the short product life due to deterioration of the excited dye has been a problem of the dye laser.

In order to implement anti-deterioration measures for the above-mentioned laser medium dye, the laser medium must be in a liquid state. In this case, the medium molecule or a variant thereof has a harmful interaction with the dye molecule, It was a factor that promoted deterioration. In particular, water is not suitable as a solvent for stably dispersing dye molecules because radicals having strong oxidizing power are easily generated by irradiation with strong excitation light. Therefore, as pointed out in Patent Document 2 or the like, it is necessary to select an organic solvent (ethanol or the like) having a small action of deteriorating the dye. Generally, the organic solvent is flammable and has a high temperature like a laser oscillation system. When used in a device having a part, there is a problem that there is a risk of causing a fire due to a failure or the like.
JP 09-275235 A JP-A-11-204892

  Provided are a dye laser medium which is in a liquid state capable of circulating cooling and has a slow deterioration rate regardless of a solvent to be used, and a device and a laser beam that oscillate laser light using the dye laser medium.

The present invention
(1) a laser medium for a dye laser comprising a colloidal dispersion of silica particles containing a fluorescent dye;
(2) The laser medium for a dye laser according to (1), wherein the fluorescent dye is a fluorescein compound, a stilbene compound, a coumarin compound, a rhodamine compound, an oxazine compound, a DOTC compound, or a HITC compound,
(3) The laser medium for a dye laser according to (1) or (2), wherein water or an aqueous solvent (mixture of water-soluble organic solvent and water) is used as the dispersion medium,
(4) The laser medium for a dye laser according to any one of (1) to (3), wherein the silica particles have an average particle diameter of 10 nm to 100 nm,
(5) The laser for a dye laser according to any one of (1) to (4), wherein the silica particles have a core-shell structure including a core having a dye and a shell having no dye. medium,
(6) A dye laser oscillation device using the laser medium for a dye laser according to any one of (1) to (5), and laser light emitted from the device according to (7) (6) It is.

The laser medium for a dye laser of the present invention can suppress the deterioration rate without being influenced by the solvent, while being in a liquid state that can be circulated and cooled. In addition, low-cost, harmless and nonflammable water can be used as the dispersion medium. Further, the entire Si sensitivity wavelength region (visible + near infrared) of 400 to 950 nm can be covered depending on the type of dye molecule used. Further, the dye laser oscillation device of the present invention can suppress the deterioration of the dye used, and can extend the life of the product.
Since the laser beam of the present invention can cover the visible light wavelength range, it can be suitably used as a light source for optical decoration, a light source for visual decoration, and a light source for hologram photography.

The laser medium for the dye laser of the present invention comprises a colloidal dispersion of silica particles containing a fluorescent dye.
Although it does not specifically limit as fluorescent dye for dye laser, For example, a fluorescein compound, a stilbene compound, a coumarin compound, a rhodamine compound, an oxazine compound, a DOTC (diethyl oxatricarbocyanine iodide) compound, HITC (hexa) Methylindotricarbocyanine iodide) compounds and the like.

  In the present invention, “a colloidal dispersion of silica particles” refers to those in which silica particles containing silica (silicon dioxide) as a main component (usually a content of 50% by mass or more) are colloidally dispersed in a liquid as colloidal particles. It is. In the present invention, the “colloidal silica particles” mean colloidal particles contained in the colloidal dispersion of silica particles. In the present invention, the colloidal silica particles contain a fluorescent dye. In the present invention, the colloidal silica particles are preferably particles formed by chemically binding or adsorbing a fluorescent substance and a silica component. In the colloidal silica particles, the fluorescent material may be distributed throughout the colloidal silica particles from the inside to the surface of the colloidal silica particles, or particles formed by chemically binding or adsorbing the light-absorbing material and the silica component, It may have a core-shell structure coated with a silica component, and preferably has a core-shell structure consisting of a core having a dye and a shell having no dye.

In the present invention, the colloidal silica particles are preferably in a state in which a fluorescent substance is immobilized, and it is preferable that 10 ¹ to 10 ³ or more fluorescent dye molecules are contained per colloidal silica particle.

In the present invention, the dispersion medium molecules usually do not penetrate into the silica particles, and the dispersion medium does not adversely affect the dye molecules. Therefore, the most easy-to-handle dispersion medium can be selected. Water or an organic solvent is preferably used, and the dispersion medium is more preferably water that is low-cost, harmless and nonflammable, and particularly preferably pure water.
As the organic solvent, any organic solvent used as a medium of a conventional dye laser medium can be used. In particular, it is desirable to use an aqueous solvent obtained by mixing a water-soluble organic solvent and water. For example, when a water-soluble organic solvent such as ethyl alcohol, methyl alcohol, ethylene glycol monomethyl ether, or acetone is used, the organic solvent can be diluted with water to a level at which there is no risk of fire or the like.
In the present invention, if the silica particles are dispersed in the liquid in the form of a colloid, they can be used in the existing circulation cooling mechanism for a dye laser system without any special design change. The method for dispersing the silica particles is not particularly limited, and any conventionally used dispersion method can be used.

The average particle diameter of the colloidal silica particles used in the present invention is preferably 10 nm or more and 100 nm or less. If the particle diameter of the colloidal silica particles is 100 nm or less, Rayleigh scattering with respect to excitation light or fluorescence in the visible light wavelength band is small, and it is preferable that there is no problem of a decrease in laser oscillation efficiency due to normal light loss. Moreover, it is preferable that the lower limit of the average particle diameter of a silica particle is 10 nm or more. The reason is that when the particle size of the silica particles is too small, the dispersibility of the particles is reduced, the particles are easily aggregated, and the light loss due to aggregation is increased.
In addition, the intensity of the above Rayleigh scattering is, for example, as shown in the [Rayleigh scattering] section of the Riken dictionary (5th edition),

Because it can be given by. Here, I is the scattered light intensity, I ₀ is the incident light intensity, θ is the scattering angle, N is the number of scatterers per unit volume, α is the polarizability of the scatterers, and γ is the observation point from the scatterer group. The distance, λ, is the wavelength of light. When the scatterer has volume V

Therefore, the intensity of Rayleigh scattering is proportional to the sixth power of the size (particle diameter) of the scatterer. Therefore, from the viewpoint of suppressing a decrease in laser oscillation efficiency due to light loss, it is preferable that the particle size is smaller. FIG. 4 shows a light scattering spectrum of 0.2 mg / ml silica colloid aqueous solutions having different average particle diameters. In FIG. 4, curve 31 is a light scattering spectrum of an aqueous silica colloid solution in which silica particles are dispersed, each having an average particle diameter of 50 nm, curve 32 is an average particle diameter of 100 nm, and curve 33 is an average particle diameter of 200 nm. As shown in FIG. 4, it can be seen that the light loss decreases as the particle size of the silica particles decreases.

  However, when the particle size is reduced, the ratio of the particle surface portion (preferably having a thickness of about the size of the dye molecule) that interacts with the dispersion medium molecule increases, and the deterioration of the dye due to the influence of the dispersion medium molecule occurs. The effect will be greater. For this reason, after synthesizing the silica particles containing the fluorescent dye, a silica shell layer not containing the dye is formed on the particle surface, and the dye molecule and the solvent molecule contained in the surface portion are formed by forming a core-shell structure. It is preferable to break the interaction.

  Conventionally, when a dye molecule is dispersed in a dispersion medium as it is, a phenomenon called energy transition occurs, so when a plurality of dyes having different fluorescence wavelengths are mixed, generally only the longest wavelength fluorescence can be extracted. In the present invention, the energy transition can be suppressed by confining the dye molecules in the colloidal silica particles, and fluorescence with different wavelengths can be extracted simultaneously. Therefore, by using the laser medium of the present invention, laser oscillation of a plurality of wavelengths can be realized with a single resonator system. For example, a combination of sufficiently separated wavelengths such as a combination of stilbene, coumarin, and rhodamine. If the three primary colors of fluorescence obtained are laser-oscillated, it becomes possible to oscillate a white laser with a single resonator.

  The colloidal silica particles used in the present invention include, for example, one or more silanes on a product obtained by reacting a fluorescent dye with a silane compound and covalently bonding, ionic bonding or other chemical bonding or adsorption. It can be prepared by polymerizing the compound. As a method for preparing the colloidal silica particles used in the present invention, N-hydroxysuccinimide (NHS) ester group, maleimide group, isocyanate group, isothiocyanate group, aldehyde group, paranitrophenyl group, diethoxymethyl group, epoxy group The fluorescent dye having an active group such as a cyano group is reacted with a silane coupling agent having a substituent (for example, an amino group, a hydroxyl group, or a thiol group) that reacts corresponding to the active group to form a covalent bond. It is preferable to prepare the product obtained by polymerizing one or more silane compounds.

  For example, a fluorescent dye molecule having an NHS ester group can be prepared by an esterification reaction between the fluorescent dye molecule and NHS. However, it is also possible to obtain a commercially available product. The silane coupling agent having an amino group is not particularly limited, and examples thereof include γ-aminopropyltriethoxysilane (APS) and 3- [2- (2-aminoethylamino) ethylamino] propyl-triethoxysilane. N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane. Of these, APS is preferable.

  Next, it is preferable to produce silica particles by reacting the fluorescent dye / silane coupling agent composite compound with a silica compound. The silica compound is not particularly limited, but includes tetraethoxysilane (TEOS), γ-mercaptopropyltrimethoxysilane (MPS), γ-mercaptopropyltriethoxysilane, γ-aminopropyltriethoxysilane (APS), 3 -Thiocyanatopropyltriethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3- [2- (2-aminoethylamino) ethylamino] propyl-triethoxysilane be able to. Among these, TEOS, MPS, or APS is preferable.

  Silica obtained by washing the solution containing silica particles synthesized as described above by centrifugation or ultrafiltration to remove various silane coupling agents (including fluorescent dye / silane coupling agent composite compounds) as solutes The particles may be dispersed in a solvent such as water by a conventional method to form the laser medium of the present invention. However, as described above, the silica particles are again charged with a silane coupling agent of silica raw material without adding a fluorescent dye. Thus, it is preferable to resume the synthesis and prepare a silica particle having a core-shell structure in which a silica shell structure that protects fluorescent dye molecules located near the surface of the particle is formed, and use it as colloidal silica particles. As the silane coupling agent at this time, TEOS, MPS or APS is preferable. FIG. 5 shows a scanning electron micrograph of an example of colloidal silica particles having a core-shell structure used in the laser medium of the present invention. The colloidal silica particles shown in FIG. 5 are silica nanocolloid particles having an average particle size of 30 nm.

Next, the dye laser oscillation apparatus of the present invention will be described. The dye laser oscillation device of the present invention is not particularly limited as long as it uses a laser medium for a dye laser made of a silica colloid solution containing the above-described fluorescent dye, but it is adapted to the light absorption band of the fluorescent dye. When laser light is used as an excitation light source, it is desirable to use a laser oscillator having a ring resonator structure as shown in FIG. In the laser oscillation device shown in FIG. 3, the resonator includes four mirrors M ₁ (11), M ₂ (12), M ₃ (13), and M ₄ (14). Here, the flow of the laser medium 17 excited by the laser beam reflected by the mirror 16 from the argon ion laser 15 is in the middle of the resonance optical system constituted by the _four mirrors M ₁ (11) to M ₄ (14). A part of the resonating laser beam is transmitted through the mirror M ₄ (14) whose reflectance is lowered, and is extracted to the outside. An optical isolator 18 is disposed in the middle of the resonance optical system, and the optical resonance is limited to one direction to improve the laser light extraction efficiency. In addition, a cavity type resonator composed of a thin Fabry-Perot etalon 19, a thick Fabry-Perot etalon 20, and a birefringent filter 21 is disposed in the middle of the resonant optical system, and multimode oscillation is suppressed to provide a single laser beam. The mode is oscillating. Furthermore, by arranging a pair of transparent dielectric plates 22 in the middle of the resonant optical system and changing the angle with respect to each optical axis in a mirror-symmetric manner, the resonator length can be changed, and the laser oscillation wavelength can be made continuous. It is possible to make changes. In FIG. 3, black arrows indicate the flow of light.

The laser medium for a dye laser of the present invention is preferably stored and sold in a sealed cartridge in the form of a high-concentration colloidal dispersion (dispersion). Further, the cartridge is preferably made of a light-shielding material in order to suppress light fading during storage.
An example when the user uses the laser medium for dye laser of the present invention will be described. First, the tank of the laser oscillation device is filled with pure water, and the colloidal dispersion liquid taken out from the cartridge is added therein. After the laser medium solution is circulated for a while to sufficiently agitate the colloidal dispersion, laser light is emitted by irradiating excitation light. When replacing the laser medium to discolor the dye or to use another dye, first remove the colloidal dispersion to be replaced filling the tank of the device, and then circulate pure water through the device to circulate the colloid in the device. The particles are washed and removed, and finally a new pigment colloid dispersion is circulated in the apparatus in the manner described above. Thereby, a laser beam can be emitted from the apparatus. The laser beam of the present invention can cover the entire Si sensitivity wavelength region (visible + near infrared) of 400 to 950 nm depending on the type of dye molecule.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to this.

Example 1
2 mg of NHS-fluorescein and 1 μl of APS were reacted in 1 ml of N, N-dimethylformamide (DMF) at room temperature for 1 hour to obtain a fluorescein dye / silane coupling agent complex solution.
Fluorescein / silane coupling agent complex solution 40 μl, 14% aqueous ammonia solution 0.8 ml, ethanol 3.2 ml and TEOS 40 μl were added and reacted at room temperature for 24 hours.

  The reaction solution was centrifuged at 10,000 × g for 60 minutes, and the supernatant was removed. Washing with ethanol and pure water was performed twice in the same manner to remove TEOS, the fluorescein / silane coupling agent complex, and the organic solvent to obtain fluorescein-containing silica particles having an average particle diameter of 60 nm. A colloidal dispersion of silica particles was prepared by dispersing 1 mg of the fluorescein-containing silica particles (in terms of dry weight) in 10 ml of water. A change in photoluminescence (PL) intensity with time was measured for the prepared silica colloid dispersion. The results are shown in FIG. In addition, the time-dependent change in the photoluminescence intensity of a 1 μM (M is mol / l) aqueous solution of fluorescein molecules was measured and shown in FIG. FIG. 1 shows the PL intensity ratio when the horizontal axis is the elapsed time and the photoluminescence (PL) intensity at the start is 1. Curve 1 shows the photobleaching property of the silica colloid aqueous solution, and curve 2 shows the photobleaching property of the molecular aqueous solution.

  As shown by the curve 2 in FIG. 1, the aqueous fluorescein molecule solution has poor light fading resistance and has not been conventionally used as a laser medium for a dye laser. On the other hand, the silica colloid dispersion liquid has excellent light fading resistance as shown by curve 1 and emits laser light having a wavelength of 520 nm when used as a laser medium of a laser resonator having a ring resonator structure shown in FIG. I was able to.

Example 2
2.23 mg NHS-rhodamine (TAMRA) and 1 μl of APS were reacted in 1 ml of N, N-dimethylformamide (DMF) at room temperature for 1 hour to obtain a rhodamine / silane coupling agent complex solution. .
Rhodamine / silane coupling agent complex solution (40 μl), 14% aqueous ammonia solution (0.8 ml), ethanol (3.2 ml), and TEOS (40 μl) were added, and the reaction was performed at room temperature for 24 hours.

  The reaction solution was centrifuged at 10,000 × g for 60 minutes, and the supernatant was removed. Washing with ethanol and pure water was performed twice in the same manner to remove TEOS, rhodamine / silane coupling agent complex and organic solvent to obtain fluorescein-containing silica particles having an average particle diameter of 60 nm. A colloidal dispersion of silica particles was prepared by dispersing 1 mg of the fluorescein-containing silica particles (in terms of dry weight) in 10 ml of water. A change in photoluminescence (PL) intensity with time was measured for the prepared silica colloid dispersion. The results are shown in FIG. In addition, the change with time of the photoluminescence intensity of a 1 μM (M is mol / l) aqueous solution of rhodamine B molecules was measured and is shown in FIG. FIG. 2 shows the PL intensity ratio when the horizontal axis is the elapsed time and the photoluminescence (PL) intensity at the start is 1. Curve 3 shows the photobleaching characteristics of the silica colloid aqueous solution and curve 4 shows the rhodamine B molecule aqueous solution.

  As shown by curve 3 in FIG. 2, the colloidal silica dispersion is excellent in light fading resistance even after 40 minutes from the start of the molecular aqueous solution, and the laser having the ring resonator structure shown in FIG. When used as a laser medium of the oscillation device, a laser beam having a wavelength of 580 nm could be emitted.

3 is a graph showing the photobleaching property of the laser medium for the dye laser of Example 1. 6 is a graph showing the photobleaching property of a laser medium for a dye laser of Example 2. It is a schematic explanatory drawing of an example of the laser oscillation apparatus of this invention. It is a graph which shows the light-scattering spectrum of a silica colloid dispersion liquid. It is a scanning electron micrograph of the colloidal silica particle used for the laser medium for dye lasers of this invention.

Explanation of symbols

1 Curve showing the PL intensity ratio of a laser medium for dye laser comprising a fluorescein-containing silica colloid dispersion liquid 2 Curve showing the PL intensity ratio of a fluorescein molecular aqueous solution 3 PL intensity ratio of a laser medium for dye laser comprising a rhodamine-containing silica colloid dispersion liquid Curve 4 showing the PL intensity ratio of the rhodamine molecule aqueous solution 11 Mirror M ₁
12 mirror M ₂
13 Mirror M ₃
14 Mirror M ₄
DESCRIPTION OF SYMBOLS 15 Argon ion laser 16 Mirror 17 Laser medium 18 Isolator 19 Thin Fabry-Perot etalon 20 Thick Fabry-Perot etalon 21 Birefringence filter 22 Transparent dielectric plate 31 Light scattering spectrum of silica colloid dispersion liquid with average particle diameter of 50 nm 32 Average particle diameter Light scattering spectrum of 100 nm silica colloid dispersion liquid 33 Light scattering spectrum of silica colloid dispersion liquid with average particle diameter of 200 nm

Claims (7)

  A laser medium for a dye laser comprising a colloidal dispersion of silica particles containing a fluorescent dye.   The laser medium for a dye laser according to claim 1, wherein the fluorescent dye is a fluorescein compound, a stilbene compound, a coumarin compound, a rhodamine compound, an oxazine compound, a DOTC compound, or a HITC compound.   3. The laser medium for dye laser according to claim 1, wherein water or an aqueous solvent is used as the dispersion medium.   The laser medium for a dye laser according to any one of claims 1 to 3, wherein an average particle diameter of the silica particles is 10 nm or more and 100 nm or less.   The laser medium for a dye laser according to any one of claims 1 to 4, wherein the silica particles have a core-shell structure including a core having a dye and a shell having no dye.   A dye laser oscillating device using the laser medium for a dye laser according to claim 1.   Laser light emitted from the apparatus according to claim 6.