JP4919463B2 - Silica glass for laser media - Google Patents

Description

  The present invention relates to a silica glass for a laser medium containing a rare earth metal element and aluminum and intended for laser amplification and laser oscillation, and a laser apparatus using the same.

  In recent years, various functional materials have been developed in which functional elements are contained in glass, ceramics, single crystals, etc., and optical properties such as wavelength conversion, laser amplification, laser oscillation, and hole burning are imparted. Among these materials, silica glass has high light transmission from the near infrared to the ultraviolet region, is resistant to thermal shock, is chemically stable, and is relatively easy to increase in size. It is attracting attention as a material.

  As one of functional materials using silica glass as a host material, a silica glass for a laser medium containing a rare earth metal element has been proposed. The laser medium glass used today is a material in which a rare earth metal element is contained in a phosphate glass, but the phosphate glass has a small thermal shock constant of 0.43 W / cm. There is a drawback in that it can not withstand the thermal shock and breaks. Silica glass has a thermal shock constant of 14.5 W / cm, which is two orders of magnitude higher than phosphoric acid-based glass. Therefore, silica glass doped with rare earth metal elements has been attracting attention and researched as a laser glass material capable of high repetition oscillation.

  However, when doping silica glass with only a rare earth metal element at a high concentration, the rare earth metal elements often associate with each other to cause concentration quenching, so that there is a problem that high concentration doping cannot be performed. Concentration quenching is a phenomenon in which the light emission efficiency is lowered due to the short distance between the doped rare earth metal elements, which significantly deteriorates the laser oscillation efficiency.

As rare earth metal element-doped silica glass in which concentration quenching is suppressed, glass co-doped with Al ₂ O ₃ and P ₂ O ₅ together with rare earth metal elements is known (Patent Document 1). Further, as a functional silica glass in which the association of rare earth metal elements is further suppressed, a silica glass obtained by sintering a zeolite in which a rare earth metal element is stably fixed and a silica raw material has been proposed (Patent Document 2).

In Patent Document 3, and SiO ₂ of the main component, at least one metal oxide of the respective metal elements of atomic numbers 3～6,11～13,19～32,37～51,55～84 and 87-108 0.01 to 30% and additive material as active substance was added, Al ₂ O ₃ or any one or mole both with respect to the active substance P ₂ O ₅ molar ratio objects to the main component SiO ₂ It is a laser glass containing a supplementary additive substance added in a ratio of 0 to 30 times, and the homogeneity indicated by at least the fluctuation range of the refractive index per unit volume of the CGS unit system is 1 × 10 ⁻⁵ or less A doped quartz glass characterized by a glass body in which additive substances are distributed is shown.
JP 60-11245 JP-A-9-86952 JP-A-64-76933

  However, in the glasses described in Patent Documents 1 and 2, no consideration is given to bubbles in the glass and minute refractive index fluctuations, that is, a granular structure. If bubbles or granular structures are present, light scattering occurs inside the glass, resulting in loss of light. In addition, bubbles in the glass play a role like a lens to collect light and cause damage such as cracks to the glass. For this reason, the glass described in Patent Documents 1 and 2 cannot perform laser amplification and laser oscillation, or even if it can, the efficiency is remarkably deteriorated. In addition, Patent Document 3 describes that, when using a physical property value of refractive index, it is necessary to have no granular structure or bubbles, but from the viewpoint of light loss, attention is paid to granular structures and bubbles. In addition, the evaluation method is insufficient. Actually, the doped quartz glass described in Patent Document 3 has a low oscillation efficiency and is insufficient.

  Further, in these glasses, no consideration is given to the OH group concentration in the glass. In laser media, an inversion distribution is formed by excitation, and laser amplification and laser oscillation are performed by emitting light with the same wavelength, phase, and direction by stimulated emission. However, when there are many OH groups in the laser glass, the laser medium is excited. The non-radiative transition in which the electrons relax to the lower level without emitting light through the lattice vibration level of the OH group occurs, and the amplification and oscillation efficiency are remarkably deteriorated. Therefore, it is very important to control the OH group concentration in the glass.

  In view of the above-mentioned problems, the present inventors have earnestly worked on the invention of a laser glass suitable for performing high-efficiency and stable laser amplification and laser oscillation so that the rare earth metal element concentration and the aluminum concentration are within appropriate ranges. By making the light loss coefficient at a wavelength other than the absorption wavelength in the visible to infrared region below a certain value, having less bubbles, and keeping the OH group concentration below a certain value, highly efficient and stable laser amplification and laser oscillation are possible. The present inventors have found that laser glass can be obtained and completed the present invention.

  A first object of the present invention is a silica for a laser medium which is doped with a rare earth metal element and aluminum at an appropriate concentration, has low scattering and low absorption, has few bubbles and has a low OH concentration, and is capable of laser oscillation with high efficiency. To provide glass.

  A second object of the present invention is to provide a laser device using rare earth metal element-doped silica glass.

The present invention can also provide a fiber laser device using a rare earth metal element-doped silica glass as a core .

In order to achieve the above object, the silica glass for laser medium of the present invention contains a rare earth metal element and aluminum, the rare earth metal element concentration is 0.2 wt% or more and 5 wt% or less, [number of moles of aluminum] / [rare earth]. The molar ratio of aluminum and the rare earth metal element represented by [number of moles of metal element] is 2 or more and less than 10, and the light loss coefficient at wavelengths other than the absorption wavelength in the visible to infrared region is 0.02 cm ⁻¹ or less, 100 cm. the total cross-sectional area of per ³ foam 0.10 mm ² or less, OH group concentration of Ri der less 20 ppm, the rare earth metal elements and aluminum is introduced using a zeolite with a rare earth metal element is fixed by ion exchange, The rare earth metal element is Nd .

As the rare earth metal element, one selected from the group consisting of Yb, Er, Tm and Ho can be applied in addition to Nd .

  It is preferable that the rare earth metal element and aluminum are introduced using zeolite in which the rare earth metal element is fixed by ion exchange.

  The laser apparatus of the present invention uses the silica glass for a laser medium of the present invention.

  This fiber laser apparatus uses the silica glass for a laser medium of the present invention as a core.

  According to the silica glass for a laser medium of the present invention, a great effect that a highly efficient and stable laser amplification and laser oscillation can be performed is achieved.

  Embodiments of the silica glass for laser medium of the present invention will be described below, but these are exemplarily shown, and it goes without saying that various modifications are possible without departing from the technical idea of the present invention. .

  In the silica glass for laser medium of the present invention, the rare earth metal element concentration in the glass is 0.2 wt% or more and 5 wt% or less. If the rare earth metal element concentration is too low, the laser amplification and oscillation efficiency will be very poor. Therefore, it should be 0.2 wt% or more, and more preferably 0.5 wt% or more. Further, when the rare earth metal element concentration is too high, crystallization called devitrification occurs when heated and melted, and the translucency is lost. Therefore, the rare earth metal element concentration needs to be 5 wt% or less, and more preferably 4 wt% or less.

  Moreover, in the silica glass for laser medium of the present invention, Al plays a role of preventing concentration quenching by dispersing rare earth metal elements and is an essential element. As for the ratio of aluminum to the rare earth metal element, [mole number of aluminum] / [mole number of rare earth metal element] needs to be 2 or more and less than 10. If the Al content is too small relative to the rare earth metal element, clustering of the rare earth metal element cannot be sufficiently prevented, and concentration quenching occurs and laser amplification and laser oscillation efficiency are remarkably deteriorated. It is necessary to be 2 times or more, and 3 times or more is more preferable because concentration quenching can be almost completely prevented. On the other hand, if there is too much Al relative to the rare earth metal element, devitrification is likely to occur. Therefore, Al needs to be less than 10 times that of the rare earth metal element, and more preferably less than 8 times.

In the silica glass for laser medium of the present invention, it is essential that the light loss coefficient at wavelengths other than the visible to infrared absorption wavelength is 0.02 cm ⁻¹ or less.

The light loss coefficient represents the loss of light in the laser medium due to scattering and absorption. If the light loss coefficient at a wavelength other than the absorption wavelength in the visible to infrared region is larger than 0.02 cm ⁻¹ , the loss of light is too large, and the efficiency of laser oscillation and laser amplification is remarkably deteriorated. Since light loss that affects strongly the laser oscillation efficiency, the laser amplification efficiency, preferable to be 0.005 cm ^-1 or less, and more preferably 0.001 / cm ^-1 or less.

  In the present specification, the wavelength other than the absorption wavelength in the visible to infrared region refers to a wavelength that is not absorbed by silica glass and a doped metal element in a wavelength region of 400 nm to 3000 nm. For example, when Nd and Al are doped, the wavelength is in the range of 1000 nm to 1200 nm, and when measured at 1040 nm to 1080 nm, which is near the laser amplification and oscillation wavelength, it can be directly compared with the amplification and oscillation performance. Is particularly preferred. When Yb and Al are doped, measurement is performed in the range of 1060 nm to 1100 nm, and when Er and Al are doped, measurement is performed in the range of 1530 nm to 1580 nm.

In the silica glass for laser medium of the present invention, the total cross-sectional area of bubbles per 100 cm ³ is required to be 0.10 mm ² or less. This is because if there are bubbles in the laser medium, the amplification and oscillation efficiency decrease due to the scattering. In addition, bubbles in the glass may act as a lens to collect light and damage the glass. Therefore, it bubbles in the glass is necessary that the total cross-sectional area of bubbles per 100 cm ³ is 0.10 mm ² or less, desirably When it is 0.01 mm ² or less.

  In the silica glass for laser medium of the present invention, the OH group concentration needs to be 20 ppm or less. Since the OH group in the laser glass causes a non-radiative transition in which excited electrons relax without emitting light, thereby reducing the light emission efficiency, it is necessary to lower the OH group concentration. In order to perform high-efficiency laser amplification and laser oscillation, the OH group concentration needs to be 20 ppm or less, and if it is 5 ppm or less, very high-efficiency laser amplification and laser oscillation have almost no effect on the light emission efficiency. Can do.

  Moreover, in the silica glass for laser media of the present invention, it is more preferable that the rare earth metal element and aluminum to be doped are doped as ion-exchanged zeolite. This is because, as shown in Patent Document 2, the association of rare earth metal elements can be sufficiently suppressed, and the silica glass for a laser medium becomes more efficient.

Further, the silica glass for laser medium of the present invention preferably has a refractive index distribution at a wavelength of 632 nm of 5 × 10 ⁻⁶ or less and a birefringence of 10 nm / cm or less. The refractive index distribution and the amount of birefringence affect the laser beam quality. Therefore, the refractive index distribution is 5 × 10 ⁻⁶ or less, more preferably 3 × 10 ⁻⁶ or less, and the birefringence is 10 nm / cm or less, more preferably 5 nm / cm or less.

  The silica glass for laser medium of the present invention is preferably free of striae. The striae in the glass refract light and thereby degrade the beam quality of the laser. Therefore, it is preferable that there is no striae when viewed from the optical axis direction of the laser, and it is more preferable that the three-way striae is free.

  The laser device of the present invention includes a laser amplification device and a laser oscillation device. As shown in FIG. 1, the laser amplification device 10 of the present invention is basically the same as a conventional laser amplification device, and includes a pumping light source 12 such as a flash lamp or a laser diode, and a laser medium 14. This is a device for increasing the intensity of laser light oscillated by another device. The feature of the laser amplifying apparatus 10 of the present invention is that the silica glass for laser medium of the present invention is used as the laser medium 14. As shown in FIG. 2, the laser oscillation device 20 of the present invention is basically the same as a conventional laser oscillation device, and includes an excitation light source 22 such as a flash lamp and a laser diode, a laser medium 24, and light reflection. The apparatus includes a mirror 26 and a partial reflection mirror 28, and oscillates laser light. The laser oscillator 20 of the present invention is characterized in that the silica glass for laser medium of the present invention is used as the laser medium 24.

  The fiber laser device of the present invention includes a fiber laser oscillation device, a fiber laser amplification device, and a fiber laser used in these devices. As shown in FIG. 3, the fiber laser 30 of the present invention is the same as the conventional fiber laser in the basic structure, and a laser medium glass 32 is provided in the portion corresponding to the core of the optical fiber, and the laser is provided in the portion corresponding to the clad. A silica glass 34 having a refractive index lower than that of the medium is used, and indicates a fiber-like laser medium. The feature of the fiber laser 30 of the present invention is that the silica glass for laser medium of the present invention is used as the laser medium glass 32. The fiber laser amplifying apparatus 40 of the present invention is the same as the conventional laser oscillation apparatus in the basic structure, and as shown in FIG. 4, a laser diode 42, a WDM coupler 44, a fiber laser 30, and an input side connector 46. And an output side connector 48. A feature of the fiber laser amplifying apparatus 40 of the present invention is that the fiber laser 30 of the present invention is used as a fiber laser.

Example 1
Nd ion exchanged zeolite was prepared by the following steps. 2000 g of X-type zeolite having a molar ratio of silicon to aluminum of Si: Al = 4: 3 was immersed in 10 L of an aqueous neodymium nitrate solution having a concentration of 150 g / L, and heated at 100 ° C. for 5 days while refluxing. Thereafter, the zeolite is separated by suction filtration, and the washing step of pouring pure water into the zeolite and stirring and then separating by filtration is repeated three times, followed by drying at 300 ° C. using a dryer. An ion exchange zeolite was obtained. When the composition of this zeolite was measured with a fluorescent X-ray analyzer, the Nd concentration was 15 wt% and the Al concentration was 18 wt%.

  1000 g of Nd ion-exchanged zeolite obtained by the above method, 6000 g of silica glass powder and 2000 g of alumina balls having a diameter of 10 mm are placed in an alumina ball mill, and the ball mill is rotated at 120 rpm for 48 hours to obtain a mixed powder of silica powder and zeolite powder. Got the body.

This mixed powder is put into a stainless steel mold (outer diameter 240 mm × inner diameter 200 mm × thickness 15 mm bottom plate) 50 shown in FIG. 7, and a pressure of 100 kgf / cm ² is applied to make a powder of diameter 200 mm × height 140 mm. A body molded body was obtained. This was taken out of the mold and placed in a heating furnace, heated in the atmosphere at 1300 ° C. for 100 hours, then placed in a carbon crucible with an inner diameter of 220 mm, and the whole carbon crucible was placed in a vacuum heating furnace and placed under vacuum. And heated at 1800 degrees for 1 hour to obtain a Nd-containing silica glass having a diameter of 220 mm and a height of 80 mm.

  A glass of 80 mm × 80 mm × 180 mm is cut out from this, the zone melt shearing method described in JP-A-7-267762, that is, the glass to be processed is heated and welded to a quartz glass rod held by a lathe and heated by a burner. Then, the glass was homogenized by moving the burner while changing the rotational speed of the left and right lathes. When the Nd concentration and Al concentration of the homogenized glass were examined with a fluorescent X-ray analyzer, they were Nd 2.14 wt% and Al 2.57 wt%. From this result, [aluminum mole number] / [neodymium mole number] is calculated to be 6.4.

When the bubbles in the quartz glass were examined, it was very small as 0.01 mm ² per 100 cm ³ . The OH group concentration was 1 ppm.

A sample rod having a diameter of 10 mm was cut from this glass, and both end surfaces were polished with high precision to a length of 100 mm. The sample rod had a refractive index distribution Δn in the longitudinal direction of 2 × 10 ⁻⁶ and a birefringence of 1.5 nm / cm. Further, antireflection films were attached to both end faces of this sample rod, and the light loss coefficient at a wavelength of 1064 nm was measured. As a result, it was 0.001 cm ⁻¹ and the light loss was extremely small.

  When this sample rod was subjected to an amplification test using the optical system shown in FIG. 5, laser amplification was confirmed. The laser amplifying apparatus 10A shown in FIG. 5 has the same structure as the laser amplifying apparatus 10 shown in FIG. 1, except that a CW laser 16 and a power meter 18 are added, and the sample rod is used as a laser medium. 15 is used. When this sample rod was subjected to an oscillation test using the optical system shown in FIG. 6, laser oscillation could be achieved at a wavelength of 1064 nm, which was extremely suitable as silica glass for a laser medium. The laser oscillation device 20A shown in FIG. 6 has the same structure as the laser oscillation device 20 shown in FIG. 2, but a power meter 29 is added, and the sample rod 15 is used as a laser medium. ing. In FIGS. 5 and 6, the symbol L is a laser beam.

  In addition, the measuring method of various physical properties is shown below.

Chemical composition: measured by fluorescent X-ray analysis.
OH group concentration: Calculated from the intensity of an OH stretching vibration band of 2.7 μm using a Fourier transform infrared spectrometer (AVATOR360 manufactured by Nicolet).
Optical loss coefficient measurement: Calculated by the following equation using laser incident light intensity I ₀ [mW], outgoing light intensity I _T [mW], and sample thickness d [cm]. A laser having a wavelength of 1064 nm was used for Nd-doped glass, a wavelength of 1080 nm was used for Yb-doped glass, and a wavelength of 1540 nm was used for Er-doped glass.

Refractive index distribution: A refractive index distribution at 632.8 nm was measured by an oil-on-plate method using a ZYGO MARK GPI-XP (Fizeau interferometer).
Birefringence: Birefringence measuring apparatus manufactured by Hinds, Inc. Measure birefringence at 632.8 nm using EXICOR350AT.
Amplification test: The configuration of the test apparatus is the same as that shown in FIG. The laser used for the test was a CW (continuous oscillation) laser with a wavelength of 1064 nm when the doping element is Nd, a laser with a wavelength of 1080 nm when Yb, and a laser with a wavelength of 1540 nm when Er. First, the power of the laser beam after passing through the sample was measured with a power meter in a state where the sample was not excited, that is, in a state where the xenon flash lamp was not turned on. Subsequently, when the sample is excited, that is, with the xenon flash lamp turned on, the power of the laser beam after passing through the sample is measured with a power meter, and compared with the state where it is not excited, the value of the power meter Amplification is considered to be amplification.
Oscillation test: The configuration of the test apparatus is the same as that shown in FIG. The transmittance of the laser output mirror was 20%, and the output at the time of excitation (when the flash lamp was lit) was measured with a power meter. The measurement wavelength used was a CW (continuous oscillation) laser with a wavelength of 1064 nm when the doping element was Nd, a laser with a wavelength of 1080 nm when Yb, and a laser with a wavelength of 1540 nm when Er.

(Example 2)
Nd ion-exchanged zeolite was prepared in the same manner as in Example 1. When the composition of this zeolite was confirmed with a fluorescent X-ray analyzer, the Nd concentration was 15 wt% and the Al concentration was 18 wt%.

  1500 g of Nd ion-exchanged zeolite obtained by the above method, 5500 g of silica glass powder and 2000 g of alumina balls having a diameter of 10 mm are placed in an alumina ball mill, and the ball mill is rotated at 120 rpm for 48 hours to obtain a mixed powder of silica powder and zeolite powder. Got the body. Using this mixed powder as a raw material, a powder molded body was prepared, fired, vacuum melted, and homogenized in the same manner as in Example 1 to prepare silica glass containing Nd and Al.

  When the Nd concentration and Al concentration of the homogenized glass were examined by fluorescent X-ray, they were Nd 3.21 wt% and Al 3.86 wt%. From this result, [aluminum mole number] / [neodymium mole number] was found to be 6.4.

When the bubbles in the quartz glass were examined, it was very small as 0.01 mm ² per 100 cm ³ . The OH group concentration was 1 ppm.

A sample rod having a diameter of 10 mm was cut from this glass, and both end surfaces were polished with high precision to a length of 100 mm. The sample rod had a refractive index distribution Δn in the longitudinal direction of 4 × 10 ⁻⁶ and a birefringence of 5 nm / cm. Further, antireflection films were attached to both end faces of this sample rod, and the light loss coefficient at a wavelength of 1064 nm was measured. As a result, it was 0.002 cm ⁻¹ and the light loss was extremely small.

  When this sample rod was subjected to an amplification test in the same manner as in Example 1, laser amplification was confirmed. Further, when an oscillation test was conducted in the same manner as in Example 1, laser oscillation could be achieved at a wavelength of 1064 nm, which was extremely suitable as silica glass for a laser medium.

(Example 3)
Nd ion-exchanged zeolite was prepared in the same manner as in Example 1. When the composition of this zeolite was confirmed with a fluorescent X-ray analyzer, the Nd concentration was 15 wt% and the Al concentration was 18 wt%.

  250 g of Nd ion-exchanged zeolite obtained by the above method, 6750 g of silica glass powder and 2000 g of alumina balls having a diameter of 10 mm are placed in an alumina ball mill, and the ball mill is rotated at 120 rpm for 48 hours to obtain a mixed powder of silica powder and zeolite powder. Got the body.

  Using this mixed powder as a raw material, a powder molded body was prepared, fired, vacuum melted, and homogenized in the same manner as in Example 1 to prepare silica glass containing Nd and Al.

  When the Nd concentration and Al concentration of the homogenized glass were examined by fluorescent X-rays, they were Nd 0.54 wt% and Al 0.64 wt%. From this result, [aluminum mole number] / [neodymium mole number] was determined to be 6.2.

When the bubbles in the quartz glass were examined, it was very small as 0.01 mm ² per 100 cm ³ . The OH group concentration was 3 ppm.

A sample rod having a diameter of 10 mm was cut from this glass, and both end surfaces were polished with high precision to a length of 100 mm. The sample rod had a refractive index distribution Δn in the longitudinal direction of 1 × 10 ⁻⁶ and a birefringence of 1 nm / cm. Further, antireflection films were attached to both end faces of this sample rod, and the light loss coefficient at a wavelength of 1064 nm was measured. As a result, it was 0.0005 cm ⁻¹ and the light loss was extremely small.

  When this sample rod was subjected to an amplification test in the same manner as in Example 1, laser amplification was confirmed. Further, when an oscillation test was conducted in the same manner as in Example 1, laser oscillation could be achieved at a wavelength of 1064 nm, which was extremely suitable as silica glass for a laser medium.

( Experimental example 1 )
150 g of neodymium oxide powder, 300 g of aluminum oxide powder, 6550 g of silica powder, and 2000 g of alumina balls having a diameter of 10 mm were placed in an alumina ball mill, and the ball mill was rotated at 120 rpm for 48 hours to obtain silica powder, neodymium oxide, and aluminum oxide. A mixed powder was obtained.

  Using this mixed powder as a raw material, a powder molded body was prepared, fired, vacuum melted, and homogenized in the same manner as in Example 1 to prepare silica glass containing Nd and Al.

  When the Nd concentration and Al concentration of the homogenized glass were examined by fluorescent X-ray, they were Nd 1.84 wt% and Al 2.27 wt%. From this result, [aluminum mole number] / [neodymium mole number] was found to be 6.6.

When the bubbles in the quartz glass were examined, it was very small as 0.01 mm ² per 100 cm ³ . The OH group concentration was 1 ppm.

A sample rod having a diameter of 10 mm was cut from this glass, and both end surfaces were polished with high precision to a length of 100 mm. The sample rod had a refractive index distribution Δn in the longitudinal direction of 2 × 10 ⁻⁶ and a birefringence of 2 nm / cm. Further, antireflection films were attached to both end faces of this sample rod, and the light loss coefficient at a wavelength of 1064 nm was measured. As a result, it was 0.001 cm ⁻¹ and the light loss was extremely small.

  When this sample rod was subjected to an amplification test in the same manner as in Example 1, laser amplification was confirmed. Further, when an oscillation test was conducted in the same manner as in Example 1, laser oscillation could be achieved at a wavelength of 1064 nm, which was extremely suitable as silica glass for a laser medium.

( Experimental example 2 )
150 g of neodymium oxide powder, 150 g of aluminum oxide powder, 6700 g of silica powder, and 2000 g of alumina balls having a diameter of 10 mm are placed in an alumina ball mill, and the ball mill is rotated at 120 rpm for 48 hours to obtain silica powder, neodymium oxide, and aluminum oxide. A mixed powder was obtained.

  Using this mixed powder as a raw material, a powder molded body was prepared, fired, vacuum melted, and homogenized in the same manner as in Example 1 to prepare silica glass containing Nd and Al.

  When the Nd concentration and Al concentration of the homogenized glass were examined by fluorescent X-rays, they were Nd 1.84 wt% and Al 1.13 wt%. From this result, when [number of moles of aluminum] / [number of moles of neodymium] was determined, it was 3.3.

When the bubbles in the quartz glass were examined, it was very small as 0.01 mm ² per 100 cm ³ . The OH group concentration was 1 ppm.

A sample rod having a diameter of 10 mm was cut from this glass, and both end surfaces were polished with high precision to a length of 100 mm. The sample rod had a refractive index distribution Δn in the longitudinal direction of 3 × 10 ⁻⁶ and a birefringence of 4 nm / cm. Further, antireflection films were attached to both end faces of this sample rod, and the light loss coefficient at a wavelength of 1064 nm was measured. As a result, it was 0.003 cm ⁻¹ and the light loss was extremely small.

  When this sample rod was subjected to an amplification test in the same manner as in Example 1, laser amplification was confirmed. Further, when an oscillation test was conducted in the same manner as in Example 1, laser oscillation could be achieved at a wavelength of 1064 nm, which was extremely suitable as silica glass for a laser medium.

( Experimental example 3 )
150 g of neodymium oxide powder, 400 g of aluminum oxide powder, 6450 g of silica powder, and 2000 g of alumina balls having a diameter of 10 mm are placed in an alumina ball mill, and the ball mill is rotated at 120 rpm for 48 hours to obtain silica powder, neodymium oxide, and aluminum oxide. A mixed powder was obtained.

  Using this mixed powder as a raw material, a powder molded body was prepared, fired, vacuum melted, and homogenized in the same manner as in Example 1 to prepare silica glass containing Nd and Al.

  When the Nd concentration and Al concentration of the homogenized glass were examined by fluorescent X-rays, they were Nd 1.84 wt% and Al 3.02 wt%. From this result, [aluminum mole number] / [neodymium mole number] was determined to be 8.5.

When the bubbles in the quartz glass were examined, it was very small as 0.01 mm ² per 100 cm ³ . The OH group concentration was 1 ppm.

A sample rod having a diameter of 10 mm was cut from this glass, and both end surfaces were polished with high precision to a length of 100 mm. The sample rod had a refractive index distribution Δn in the longitudinal direction of 5 × 10 ⁻⁶ and a birefringence of 7 nm / cm. Antireflection films were attached to both end faces of this sample rod, and the light loss coefficient at a wavelength of 1064 nm was measured. As a result, it was 0.0005 cm ⁻¹ and the light loss was extremely small.

  When this sample rod was subjected to an amplification test in the same manner as in Example 1, laser amplification was confirmed. Further, when an oscillation test was conducted in the same manner as in Example 1, laser oscillation could be achieved at a wavelength of 1064 nm, which was extremely suitable as silica glass for a laser medium.

( Experimental example 4 )
150 g of ytterbium oxide powder, 300 g of aluminum oxide powder, 6550 g of silica powder, and 2000 g of alumina balls having a diameter of 10 mm are placed in an alumina ball mill, and the ball mill is rotated at 120 rpm for 48 hours. A mixed powder was obtained.

  Using this mixed powder as a raw material, a powder molded body was prepared, fired, vacuum melted, and homogenized in the same manner as in Example 1 to prepare silica glass containing Yb and Al.

  When the Yb concentration and Al concentration of the homogenized glass were examined by fluorescent X-rays, they were Yb 1.88 wt% and Al 2.27 wt%. From this result, [aluminum moles] / [ytterbium moles] was determined to be 7.7.

When the bubbles in the quartz glass were examined, it was very small as 0.01 mm ² per 100 cm ³ . The OH group concentration was 1 ppm.

A sample rod having a diameter of 10 mm was cut from this glass, and both end surfaces were polished with high precision to a length of 100 mm. The sample rod had a refractive index distribution Δn in the longitudinal direction of 2 × 10 ⁻⁶ and a birefringence of 2 nm / cm. Further, antireflection films were attached to both end faces of this sample rod, and the light loss coefficient at a wavelength of 1080 nm was measured. As a result, it was 0.001 cm ⁻¹ and the light loss was extremely small.

  When this sample rod was subjected to an amplification test in the same manner as in Example 1 except that the oscillation wavelength of the laser used was 1080 nm, laser amplification was confirmed. Further, when an oscillation test was performed in the same manner as in Example 1, laser oscillation could be achieved at a wavelength of 1080 m, which was extremely suitable as a silica glass for a laser medium.

( Experimental example 5 )
150 g of erbium oxide powder, 300 g of aluminum oxide powder, 6550 g of silica powder, and 2000 g of alumina balls having a diameter of 10 mm were placed in an alumina ball mill, and the ball mill was rotated at 120 rpm for 48 hours to obtain silica powder, erbium oxide, and aluminum oxide. A mixed powder was obtained.

  Using this mixed powder as a raw material, a powder molded body was prepared, fired, vacuum melted, and homogenized in the same manner as in Example 1 to prepare silica glass containing Er and Al.

  When the Er concentration and Al concentration of the homogenized glass were examined by fluorescent X-rays, they were Er 1.87 wt% and Al 2.27 wt%. From this result, the [number of moles of aluminum] / [number of moles of erbium] was determined to be 7.5.

When the bubbles in the quartz glass were examined, it was very small as 0.01 mm ² per 100 cm ³ . The OH group concentration was 1 ppm.

A sample rod having a diameter of 10 mm was cut from this glass, and both end surfaces were polished with high precision to a length of 100 mm. The sample rod had a refractive index distribution Δn in the longitudinal direction of 2 × 10 ⁻⁶ and a birefringence of 2 nm / cm. Further, antireflection films were attached to both end faces of the sample rod, and the light loss coefficient at a wavelength of 1540 nm was measured. As a result, it was 0.001 cm ⁻¹ and the light loss was extremely small.

  When this sample rod was subjected to an amplification test in the same manner as in Example 1 except that the oscillation wavelength of the laser used was 1540 nm, laser amplification was confirmed. Further, when an oscillation test was conducted in the same manner as in Example 1, laser oscillation could be achieved at a wavelength of 1540 nm, which was extremely suitable as silica glass for a laser medium.

(Comparative Example 1)
Nd ion-exchanged zeolite was prepared in the same manner as in Example 1. When the composition of this zeolite was confirmed with a fluorescent X-ray analyzer, the Nd concentration was 15 wt% and the Al concentration was 18 wt%.

  20 g of Nd ion-exchanged zeolite obtained by the above method, 6980 g of silica glass powder and 2000 g of alumina balls having a diameter of 10 mm are placed in an alumina ball mill, and the ball mill is rotated at 120 rpm for 48 hours to obtain a mixed powder of silica powder and zeolite powder. Got the body.

  Using this mixed powder as a raw material, a powder molded body was prepared, fired, vacuum melted, and homogenized in the same manner as in Example 1 to prepare silica glass containing Nd and Al.

  When the Nd concentration and Al concentration of the homogenized glass were examined with fluorescent X-rays, they were Nd 0.04 wt% and Al 0.05 wt%. From this result, the [number of moles of aluminum] / [number of moles of neodymium] was determined to be 6.7.

When the bubbles in the quartz glass were examined, it was very small as 0.01 mm ² per 100 cm ³ . The OH group concentration was 1 ppm.

A sample rod having a diameter of 10 mm was cut from this glass, and both end surfaces were polished with high precision to a length of 100 mm. The sample rod had a refractive index distribution Δn in the longitudinal direction of 1 × 10 ⁻⁶ and a birefringence of 1 nm / cm. Antireflection films were attached to both end faces of this sample rod, and the optical loss coefficient at a wavelength of 1064 nm was measured. As a result, it was 0.0005 cm ⁻¹ and the absorption and scattering were very small.

  This sample rod was subjected to an amplification test in the same manner as in Example 1. However, laser amplification could not be confirmed. Further, an oscillation test was conducted in the same manner as in Example 1. However, laser oscillation was not possible, and this was insufficient as silica glass for a laser medium.

(Comparative Example 2)
Two batches of Nd ion-exchanged zeolite were prepared in the same manner as in Example 1. When the composition of this zeolite was confirmed with a fluorescent X-ray analyzer, the Nd concentration was 15 wt% and the Al concentration was 18 wt%.

  3000 g of Nd ion-exchanged zeolite obtained by the above method, 4000 g of silica glass powder and 2000 g of alumina balls having a diameter of 10 mm are placed in an alumina ball mill, and the ball mill is rotated at 120 rpm for 48 hours to obtain a mixed powder of silica powder and zeolite powder. Got the body.

  Using this mixed powder as a raw material, a powder molded body was prepared, fired, vacuum melted, and homogenized in the same manner as in Example 1 to produce silica glass containing Nd and Al, but it was milky white. When the Nd concentration and Al concentration were examined by fluorescent X-ray, they were Nd of 6.43 wt% and Al of 7.71 wt%, and [aluminum mole number] / [neodymium mole number] was 6.4.

  Foam, light loss coefficient, OH group concentration, refractive index distribution, and birefringence could not be measured due to emulsion. Moreover, neither an amplification test nor an oscillation test could be performed, which was insufficient as a silica glass for a laser medium.

(Comparative Example 3)
150 g of neodymium oxide powder, 50 g of aluminum oxide powder, 6800 g of silica powder, and 2000 g of alumina balls having a diameter of 10 mm are placed in an alumina ball mill, and the ball mill is rotated at 120 rpm for 48 hours to obtain silica powder, neodymium oxide, and aluminum oxide. A mixed powder was obtained.

  Using this mixed powder as a raw material, a powder molded body was prepared, fired, vacuum melted, and homogenized in the same manner as in Example 1 to produce silica glass containing Nd and Al, but it was milky white. The Nd concentration and Al concentration were examined by fluorescent X-ray. As a result, Nd was 1.84 wt% and Al was 0.38 wt%, and [aluminum mole number] / [neodymium mole number] was 1.1.

  Foam, light loss coefficient, OH group concentration, refractive index distribution, and birefringence could not be measured due to emulsion. Moreover, neither an amplification test nor an oscillation test could be performed, which was insufficient as a silica glass for a laser medium.

(Comparative Example 4)
150 g of neodymium oxide powder, 550 g of aluminum oxide powder, 6300 g of silica powder, and 2000 g of alumina balls having a diameter of 10 mm were placed in an alumina ball mill, and the ball mill was rotated at 120 rpm for 48 hours to obtain silica powder, neodymium oxide, and aluminum oxide. A mixed powder was obtained.
Using this mixed powder as a raw material, a powder molded body was prepared, fired, vacuum melted, and homogenized in the same manner as in Example 1 to produce silica glass containing Nd and Al, but it was milky white. When the Nd concentration and Al concentration were examined by fluorescent X-rays, they were Nd 1.84 wt% and Al 4.16 wt%, and [aluminum mole number] / [neodymium mole number] was 12.1.

  Foam, light loss coefficient, OH group concentration, refractive index distribution, and birefringence could not be measured due to emulsion. Moreover, neither an amplification test nor an oscillation test could be performed, which was insufficient as a silica glass for a laser medium.

(Comparative Example 5)
In the same manner as in Example 1, zeolite ion exchange, mixing, pulverization, powder molding production, firing, and vacuum melting were performed to produce silica glass containing Nd and Al that were not homogenized.

  When the Nd concentration and Al concentration of this glass were examined by fluorescent X-ray, they were Nd 2.14 wt% and Al 2.57 wt%. From this result, [aluminum mole number] / [neodymium mole number] was found to be 6.4.

When the bubbles in the quartz glass were examined, it was 0.2 mm ² per 100 cm ³ . The OH group concentration was 1 ppm.

A sample rod having a diameter of 10 mm was cut from this glass, and both end surfaces were polished with high precision to a length of 100 mm. The sample rod had a refractive index distribution Δn in the longitudinal direction of 2 × 10 ⁻⁵ and a birefringence of 15 nm / cm. Antireflection films were attached to both end faces of this sample rod, and the light loss coefficient at a wavelength of 1064 nm was measured. As a result, it was 0.05 cm ⁻¹ and the loss of light was large.

  Using this sample rod, an amplification test was conducted in the same manner as in Example 1. However, laser amplification could not be confirmed. Further, an oscillation test was conducted in the same manner as in Example 1. However, laser oscillation was not possible, and this was insufficient as silica glass for a laser medium.

(Comparative Example 6)
Nd ion-exchanged zeolite was prepared in the same manner as in Example 1. When the composition of this zeolite was confirmed with a fluorescent X-ray analyzer, the Nd concentration was 15 wt% and the Al concentration was 18 wt%.

  1000 g of Nd ion-exchanged zeolite obtained by the above method and 6000 g of silica glass powder were mixed for 8 hours using a V-type mixer. The obtained mixed powder was introduced into an oxyhydrogen flame and melted and deposited to obtain an ingot having a diameter of 10 cm and a length of 30 cm. This ingot was homogenized in the same manner as in Example 1 to prepare a silica glass containing Nd and Al.

  When the Nd concentration and Al concentration of this glass were examined by fluorescent X-ray, they were Nd 2.14 wt% and Al 2.57 wt%. From this result, [aluminum mole number] / [neodymium mole number] was found to be 6.4.

When the bubbles in the quartz glass were examined, it was 0.08 mm ² per 100 cm ³ . The OH group concentration was 50 ppm.

A sample rod having a diameter of 10 mm was cut from this glass, and both end surfaces were polished with high precision to a length of 100 mm. The sample rod had a refractive index distribution Δn in the longitudinal direction of 6 × 10 ⁻⁶ and a birefringence of 15 nm / cm. Antireflection films were attached to both end faces of this sample rod, and the light loss coefficient at a wavelength of 1064 nm was measured. As a result, it was 0.01 cm ⁻¹ and there was little light loss.

    Using this sample rod, an amplification test was conducted in the same manner as in Example 1. However, laser amplification could not be confirmed. Further, an oscillation test was conducted in the same manner as in Example 1. However, laser oscillation was not possible, and this was insufficient as silica glass for a laser medium.

It is explanatory drawing which shows an example of a structure of the laser amplifier of this invention. It is explanatory drawing which shows an example of a structure of the laser oscillation apparatus of this invention. It is explanatory drawing which shows an example of a structure of the fiber laser of this invention. It is explanatory drawing which shows an example of a structure of the fiber laser apparatus of this invention. 1 is an explanatory diagram illustrating a configuration of a laser amplification device according to Embodiment 1. FIG. FIG. 3 is an explanatory diagram illustrating a configuration of a laser oscillation device according to the first embodiment. It is explanatory drawing which shows the structure of the metal mold | die used in Example 1. FIG.

Explanation of symbols

  12, 22: Light source for excitation, 14: Laser medium, 15: Sample rod, 16: Laser, 18: Power meter, 20: Laser oscillator, 20A: Laser oscillator, 24: Laser medium, 26: Light reflector, 28: partial reflection mirror, 29: power meter, 30: fiber laser, 32: laser medium glass, 34: silica glass, 40: fiber laser amplifier, 42: laser diode, 44: coupler, 46: input side connector, 48 : Output side connector, 50: mold, L: laser beam.

Claims (2)

The rare earth metal element and aluminum are contained, and the rare earth metal element concentration is 0.2 wt% or more and 5 wt% or less, and the molar ratio of aluminum and rare earth metal element represented by [aluminum mole number] / [rare earth metal element mole number] is 2 to less than 10, optical loss coefficient at wavelengths other than visible to infrared absorption wavelength is 0.02 cm ⁻¹ or less, total cross-sectional area of bubbles per 100 cm ³ is 0.10 mm ² or less, OH group concentration Ri der but 20ppm or less, the rare earth metal elements and aluminum is introduced using a zeolite with a rare earth metal element is fixed by ion exchange, and laser medium for silica, wherein the rare earth metal element is Nd Glass. A laser apparatus comprising the silica glass for a laser medium according to claim 1 .

Images