JP4037244B2 - Laser oscillation method and laser apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser oscillation method and a laser apparatus, and more particularly to a laser oscillation method and a laser apparatus using a laser medium that is excited by excitation light and oscillates.
[0002]
[Prior art]
Conventionally, gadolinium vanadate (GdVO) to which neodymium (Nd) is added as a laser active ion (hereinafter appropriately referred to as “dope”).₄) Neodymium-doped gadolinium vanadate (hereinafter referred to as “Nd: GdVO”)₄As appropriate. ) The crystal is expected to be useful as a laser medium.
[0003]
However, Nd: GdVO₄Crystals are difficult to make and Nd: GdVO₄At present, crystal growth of crystals is only performed in the research stage, and commercialization has hardly been performed.
[0004]
On the other hand, Nd: GdVO sold as a product₄It has been pointed out that crystals have a neodymium addition concentration of 1% or less in terms of the number of atoms, and the neodymium addition concentration is low. In addition, none of them ensured sufficient optical characteristics.
[0005]
For this reason, Nd: GdVO₄A neodymium-doped yttrium aluminum garnet (hereinafter referred to as “Nd: YAG” as appropriate) crystal or neodymium-doped yttrium vanadate, which has the same lasing wavelength region as that of a crystal and currently occupies the center of the market as a solid-state laser medium. (Hereafter, “Nd: YVO₄As appropriate. ) Nd: GdVO compared to crystals₄The current situation is that the superiority of crystals has not been fully utilized and has not yet spread to the market.
[0006]
[Patent Document 1]
JP 2001-223423
[0007]
[Non-Patent Document 1]
Tomohiro Shonai et al.
Materials Research Bulletin
35 (2000) 225-232
For example, Patent Document 1 discloses an Nd: YAG crystal to which neodymium is added at a high concentration by a TGT (Temperature Gradient Technique) method.
[0008]
Non-Patent Document 1 discloses Nd: YVO to which neodymium is added by a floating zone method.₄Crystals are disclosed.
[0009]
Conventionally, Nd: GdVO₄When making crystals, it was difficult to add neodymium as a laser active ion at a high concentration exceeding 1% in terms of the number of atoms, so Nd: GdVO₄Laser oscillation by excitation of excitation light in a wavelength band other than the wavelength of 808 nm, which is the main absorption band of the crystal, has not been put into practical use until now.
[0010]
That is, Nd: GdVO with a low addition concentration of neodymium currently on the market₄Since the absorption of excitation light is generally low in crystals, excitation outside the main absorption band having a wavelength of 808 nm is difficult, and even if laser oscillation is performed by excitation, the energy that can be absorbed is small. The efficiency was poor and the output could not be obtained effectively.
[0011]
Therefore, Nd: GdVO in which neodymium is added as a laser medium at a high concentration exceeding 1% in terms of the number of atoms.₄Crystal production method and Nd: GdVO with neodymium added at a high concentration exceeding 1% in terms of the number of atoms₄A laser oscillation method using a crystal as a laser medium, or Nd: GdVO in which neodymium is added at a high concentration exceeding 1% in terms of the number of atoms.₄A proposal of a laser device using a crystal as a laser medium has been strongly desired.
[0012]
In this specification, Nd: GdVO in which neodymium is added as a laser active ion at a high concentration exceeding 1% in terms of the number of atoms.₄Collectively, crystals are simply “high-concentration Nd-added GdVO.₄Crystal "or" High concentration Nd: GdVO₄It will be referred to as “crystal” as appropriate.
[0013]
Also, from the same background as described above, it is a single crystal to which Tm, Ho, Er, Cr ions or the like which are laser active ions are added as a laser medium at a high concentration, for example, Tm: YVO₄And Tm: GdVO₄There has been a strong demand for a production method such as the above, a laser oscillation method using the single crystal as a laser medium, and a laser device using the single crystal as a laser medium.
[0014]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described demand for the prior art, and an object of the present invention is to provide a laser oscillation method using a laser medium made of a crystal to which laser active ions are added at a predetermined concentration. And to provide a laser device.
[0015]
[Means for Solving the Problems]
  In order to achieve the above object, the invention according to claim 1 of the present invention is a laser oscillation method in which a laser medium is excited by excitation light and laser oscillation is performed.GdVO added so that the concentration of Nd as a laser active ion exceeds 1% in terms of the number of atoms ₄ Crystal Nd: GdVO ₄ A laser medium made of crystal oscillates by exciting excitation light having a wavelength band of 880 nm, which is different from the main absorption band of wavelength 808 nm.It is what I did.
[0016]
  The invention according to claim 2 of the present invention is a laser oscillation method in which a laser medium is excited by excitation light and laser oscillation is performed.GdVO added so that the concentration of Nd as a laser active ion is 2% to 15% in terms of the number of atoms. ₄ Crystal Nd: GdVO ₄ A laser medium made of crystal oscillates by exciting excitation light having a wavelength band of 880 nm, which is different from the main absorption band of wavelength 808 nm.It is what I did.
[0017]
  Moreover, invention of Claim 3 among this invention is the following.In the invention according to any one of claims 1 and 2, the excitation light having a wavelength of 880 nm is excitation light having a wavelength of 879 nm.It is what I did.
[0018]
  Moreover, invention of Claim 4 among this invention is the following.In the invention according to any one of claims 1, 2, and 3, the excitation light having a wavelength of 880 nm band may cause Nd ions from a ground level. ⁴ F _3/2 Excited to levelIt is what I did.
[0019]
  Moreover, invention of Claim 5 among this invention is the following.The invention according to any one of claims 1, 2, 3 and 4, wherein the Nd: GdVO ₄ The crystal is made by the floating zone methodIt is what I did.
[0020]
  According to a sixth aspect of the present invention, a laser medium is disposed in the resonator, and excitation light is incident on the laser medium to cause laser oscillation in the resonator, thereby causing the resonance. Equipment that emits laser light from a vesselIn the laser medium, GdVO added so that Nd as a laser active ion has a concentration exceeding 1% in terms of the number of atoms. ₄ Crystal Nd: GdVO ₄ It is a crystal, and the excitation light is excitation light in a wavelength band of 880 nm which is a wavelength band different from the wavelength band of 808 nm which is a main absorption band.It is a thing.
[0021]
  According to a seventh aspect of the present invention, a laser medium is disposed in the resonator, and excitation light is incident on the laser medium to cause laser oscillation in the resonator, thereby causing the resonance. Equipment that emits laser light from a vesselIn the laser medium, GdVO added so that Nd as a laser active ion has a concentration of 2% to 15% in the ratio of the number of atoms. ₄ Crystal Nd: GdVO ₄ It is a crystal, and the excitation light is excitation light in a wavelength band of 880 nm which is a wavelength band different from the wavelength band of 808 nm which is a main absorption band.It is a thing.
[0022]
  In addition, the invention according to claim 8 is the invention.Claim6 or7Any one ofIn the invention described in item 3, the excitation light having the wavelength of 880 nm is such that the excitation light having the wavelength of 879 nm.It is a thing.
[0023]
  In addition, the invention according to claim 9 of the present invention is claimed in the invention.6,In the invention according to any one of 7 and 8,Nd: GdVO ₄ Crystal produced by floating zone methodIt is a thing.
[0024]
  Further, the invention described in claim 10 among the present invention is claimed in the present invention.6, 7, 8 or9Any one ofIn the invention described inThe excitation light is incident by semiconductor laser excitation.It is what I did.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of a laser oscillation method and a laser apparatus according to the present invention will be described in detail with reference to the accompanying drawings.
[0028]
First, in FIG. 1, a floating zone method (Floating Zone Method: hereinafter referred to as “FZ method” as appropriate) is a method for producing a laser medium according to an example of the embodiment of the present invention. The schematic diagram of is shown.
[0029]
That is, in the present invention, a high concentration neodymium-added gadolinium vanadate crystal or a single crystal added with Tm, Ho, Er, Cr ions, which are laser active ions, at a predetermined concentration by a technique called FZ method. Tm: YVO₄And Tm: GdVO₄The laser medium is created.
[0030]
Here, the FZ method condenses infrared light from a halogen lamp 14 as an infrared light source (Infrared Source) on a raw material rod 12 sintered in a furnace 10 at high temperature and high pressure. In this method, a melting zone (floating zone) 16 is formed between the seed crystal and the raw material rod 12, and a crystal is formed by moving the melting zone 16 in one direction. is there.
[0031]
Therefore, when a high-concentration neodymium-added gadolinium vanadate crystal is prepared by the FZ method, first, a raw material rod 12 obtained by sintering neodymium, gadolinium, and vanadate at high temperature and high pressure is prepared. Next, infrared light from the halogen lamp 14 is condensed and melted on the raw material rod 12 to form a melting zone 16 between the seed crystal and the raw material rod 12, and the melting zone 16 is moved in one direction. As a result, a high concentration neodymium-added gadolinium vanadate crystal is formed.
[0032]
According to this FZ method, for example, high concentration neodymium-added gadolinium vanadate, in which neodymium is added as a laser active ion so as to have a concentration exceeding 1% in terms of the number of atoms, as a high concentration neodymium-added gadolinium vanadate crystal. A crystal can be obtained. For example, a high-concentration neodymium-added gadolinium vanadate crystal in which neodymium is added as a laser active ion so as to have a concentration of 2% to 15% in terms of the number of atoms can be obtained.
[0033]
The above-described concentration can be controlled to an arbitrary concentration by, for example, sintering the raw material rod 12 with a predetermined concentration of Nd.
[0034]
Further, according to this FZ method, for example, a high concentration neodymium-added gadolinium vanadate crystal having a diameter of 3 mm and a length of 50 mm could be prepared.
[0035]
As the halogen lamp 14 for irradiating the raw material rod with infrared light, for example, a halogen lamp with an output of 1.5 kW can be used.
[0036]
By the way, conventionally, in producing a neodymium-added gadolinium vanadate crystal, a pulling method such as a chocolate lasky method (hereinafter referred to as “Cz method” as appropriate) has been used.
[0037]
However, as a feature of neodymium-added gadolinium vanadate crystals, the melting point of vanadate, which is a raw material, is as high as about 1700 ° C., so there are limitations on the crucible and the growing atmosphere, and it has been difficult to produce high-quality crystals.
[0038]
For this reason, in the conventional neodymium-doped gadolinium vanadate crystal in which the concentration of neodymium added is 1% or less in terms of the number of atoms, the peak of the absorption coefficient capable of laser oscillation only in the main absorption band of the wavelength of 808 nm band. Did not exist. Therefore, in order to cause laser oscillation using a conventional neodymium-doped gadolinium vanadate crystal having a concentration of neodymium as low as 1% or less in terms of the number of atoms as a laser medium, a wavelength of 808 nm is the main absorption band. It was necessary to excite with excitation light by a laser diode having a combined oscillation wavelength of 808 nm.
[0039]
On the other hand, in the FZ method according to the present invention, the crucible is not used and the growth atmosphere is not limited, so the limitations of the crucible and the growth atmosphere, which were the conventional problems, are eliminated, and it is possible to grow high-concentration and high-quality crystals. became.
[0040]
Therefore, the high-concentration neodymium-doped gadolinium vanadate crystal prepared according to the present invention has a main absorption band with the maximum absorption coefficient in the wavelength of 808 nm band, but also has a peak of absorption coefficient capable of laser oscillation around it. There is an absorption band. Therefore, in the high-concentration neodymium-added gadolinium vanadate crystal prepared according to the present invention, it becomes possible to cause laser oscillation even when using excitation light having an oscillation wavelength matched to an absorption band other than the main absorption band. .
[0041]
By the way, in a laser, an output larger than the ratio (quantum conversion efficiency) between the wavelength of incident light and the wavelength of outgoing light cannot be obtained.
[0042]
When the high-concentration neodymium-doped gadolinium vanadate crystal prepared according to the present invention is used as a laser medium, even when light of the same wavelength is oscillated, excitation light that can maximize the quantum change efficiency from a plurality of absorption bands. This makes it possible to select a wavelength of 1 and to perform highly efficient oscillation.
[0043]
Here, among the high concentration neodymium-added gadolinium vanadate crystals prepared by using the FZ method described above, the concentration of neodymium is 2%, 5%, 10%, that is, the ratio of the number of neodymium atoms is 2%, FIG. 2 shows the measurement results of the absorption spectra of three types of crystals of 5% and 10%. In FIG. 2, the horizontal axis indicates the wavelength (Wavelength) in [nm] units, and the vertical axis indicates [cm.^-1] Absorption coefficient (absorption coefficient) is taken in units.
[0044]
As apparent from FIG. 2, the absorption of the excitation light greatly increases as the concentration of added neodymium increases. For example, in a high-concentration neodymium-added gadolinium vanadate crystal in which the concentration of neodymium added is 5%, the absorption coefficient is 100 [cm at 808 nm.^-1That's it.
[0045]
As shown in FIG. 2, the high-concentration neodymium-added gadolinium vanadate crystal has a wavelength around 750 nm as an absorption band capable of laser oscillation, in addition to a main absorption band at a wavelength of 808 nm generally used for excitation by a laser diode. There is an absorption band having a peak in the region and an absorption band having a peak around the wavelength of 880 nm.
[0046]
Focusing on the absorption band having a peak around the wavelength of 880 nm among these, the quantum conversion efficiency at the time of excitation in the absorption band of the wavelength of 880 nm is “0.83 (880/1060 = 0.83)”, and the absorption at the wavelength of 808 nm. Compared with “0.75 (808/1060 = 0.75), which is the quantum conversion efficiency at the time of excitation in the band, it is possible to prevent a decrease in output due to the loss corresponding to heat being changed to heat. .
[0047]
In FIG. 3, the concentration of neodymium, that is, the ratio of the number of atoms of neodymium is 5% with excitation light having a wavelength of 879 nm in a wavelength of 880 nm band, using a laser apparatus according to the present invention described later with reference to FIG. 4. High concentration neodymium added gadolinium vanadate crystal (Nd 5% added Gd: VO₄The input / output characteristics of the experimental results of exciting the crystal) are shown.
[0048]
In FIG. 3, the horizontal axis represents the power absorbed in [W] units (Absorbed Power), that is, the input power of the pumping light, and the vertical axis represents output power (Output Power) in units of [W]. Nd 5% added Gd: VO₄The output power of the laser beam oscillated from the crystal is taken.
[0049]
Next, a concentration exceeding 1% in terms of the number of atoms of neodymium as a laser active ion, such as a high concentration neodymium-doped gadolinium vanadate crystal doped with 2%, 5%, or 10% of neodymium in terms of the number of atoms. A laser apparatus constructed using the high-concentration neodymium-added gadolinium vanadate crystal added in step 1 as a laser medium will be described.
[0050]
First, FIG. 4 shows a laser device that performs a pulse oscillation operation among laser devices configured using a high-concentration neodymium-added gadolinium vanadate crystal as a laser medium.
[0051]
The laser apparatus 100 shown in FIG. 4 includes a high-concentration neodymium-doped gadolinium vanadate crystal 102 as a laser medium, a titanium sapphire laser 104 for generating excitation light, total reflection mirrors 106 and 108, and a condensing lens 110. And an output mirror 112.
[0052]
Here, the titanium sapphire laser 104 is an excitation laser as an excitation light source for generating excitation light for pulse oscillation operation, has a wavelength of 880 nm, an average maximum output power of 40 mW, and a pulse width. This is a titanium sapphire laser of 1 ns repetition of 80 ns.
[0053]
The high-concentration neodymium-added gadolinium vanadate crystal 102 is cut to a size of “vertical 5 mm × horizontal 5 mm × thickness 1 mm”, and the first surface 102 a facing the titanium sapphire laser 104 has a wavelength of 1063 nm. The coating is applied so that the light is totally reflected and the light having a wavelength of 880 nm is not reflected, and the second surface 102 b facing the output mirror 112 is not reflected by the light having a wavelength of 1063 nm. Has been coated.
[0054]
Furthermore, the exit mirror 112 has a surface facing the high-concentration neodymium-added gadolinium vanadate crystal 102 formed as a concave surface 112a having a curvature radius of 50 mm, and the other surface formed as a flat surface 112b. Further, the concave surface 112a is coated so that the reflectance of light having a wavelength of 1064 nm is 90%, and is configured as a concave mirror. The flat surface 112b is not coded.
[0055]
The condenser lens 110 is made of fused silica glass and has a focal length of 100 mm.
[0056]
Therefore, in the laser device 100, a resonator is constituted by the first surface 102a and the concave surface 112a, and a high-concentration neodymium-added gadolinium vanadate crystal 102 is disposed as a laser medium in the resonator. It will be. The cavity length of the resonator is set to 3 cm.
[0057]
In the above configuration, when the excitation light emitted from the titanium sapphire laser 104 enters the condenser lens 110 through the total reflection mirrors 106 and 108, the condenser lens 110 converts the excitation light into a high-concentration neodymium-doped gadolinium vanadate crystal. The light is condensed and incident on 102.
[0058]
In this way, laser oscillation is generated in the resonator, and laser light is emitted from the flat surface 112b of the emission mirror 112.
[0059]
As described above, FIG. 3 is a graph showing experimental results by the inventors of the present application. In the laser device 100 shown in FIG. 4, 5% neodymium is doped as a high-concentration neodymium-added gadolinium vanadate crystal 102 in terms of the number of atoms. A graph of input / output characteristics when the high concentration neodymium-added gadolinium vanadate crystal is used is shown. As shown in FIG. 3, the slope efficiency is 50%.
[0060]
Next, FIG. 5 shows a laser device that performs a CW (continuous wave) oscillation operation in a laser device that uses a high-concentration neodymium-added gadolinium vanadate crystal as a laser medium. The laser apparatus shown in FIG. 5 is configured as a semiconductor laser excitation solid-state laser apparatus.
[0061]
In the configuration of the laser apparatus shown in FIG. 5, the same or corresponding configuration as the configuration of the laser apparatus 100 shown in FIG. 4 is indicated using the same reference numerals as those used in FIG. A description of the configuration and operation is omitted.
[0062]
A laser device 200 shown in FIG. 5 heats the high-concentration neodymium-added gadolinium vanadate crystal 102 as a laser medium, a laser diode 202 as an excitation light source for generating a beam as excitation light, and the laser diode 202. Heat sink 204, a gradient index lens 206 for converging and entering a high-concentration neodymium-added gadolinium vanadate crystal 102 as an excitation light beam emitted from the laser diode 202, and an output mirror 208. ing.
[0063]
Here, the laser diode 202 is a GaAs / GaAlAs 200 μm single stripe laser diode having a wavelength of 880 nm at 25 ° C. and a maximum output power of 2 W.
[0064]
The heat sink 204 is made of a copper block, but is cooled by water cooling.
[0065]
Further, the exit mirror 208 has a surface facing the high-concentration neodymium-added gadolinium vanadate crystal 102 formed as a concave surface 208a having a curvature radius of 750 mm, and the other surface formed as a flat surface 208b. The concave surface 208a is coated so that the reflectance of light having a wavelength of 1064 nm is 95%, and is configured as a concave mirror. The flat surface 208b is not coded.
[0066]
The gradient index lens 206 has a diameter of 1.8 mm.
Therefore, in this laser apparatus 200, a resonator is constituted by the first surface 102a and the concave surface 208a, and the high-concentration neodymium-added gadolinium vanadate crystal 102 is disposed as a laser medium in the resonator. It will be. The cavity length of the resonator is set to 3 cm.
[0067]
Further, semiconductor laser excitation in this laser device 200 is longitudinal excitation in which excitation light is incident on the high-concentration neodymium-doped gadolinium vanadate crystal 102 as a laser medium from a direction substantially coincident with the optical axis of light reciprocating through the resonator by laser oscillation. It is.
[0068]
In the above configuration, when the beam as the excitation light emitted from the laser diode 202 is incident on the gradient index lens 206, the gradient index lens 206 condenses and enters the beam on the high-concentration neodymium-added gadolinium vanadate crystal 102. .
[0069]
In this way, laser oscillation occurs in the resonator, and laser light is emitted from the flat surface 208b of the emission mirror 208.
[0070]
As described above, Nd: GdVO in which neodymium is added at a high concentration exceeding 1% in terms of the number of atoms.₄By using a crystal, laser oscillation can be performed by performing excitation in an absorption band of a wavelength band other than the main wavelength band of 808 nm (for example, a wavelength of 880 nm band).
[0071]
That is, by adding neodymium at a high concentration, Nd: GdVO₄Since the absorption coefficient of crystals dramatically increases, Nd: GdVO in which neodymium prepared by conventional techniques is added at a low concentration₄Excitation in a wavelength region having a small absorption coefficient, which was difficult with crystals, has become possible.
[0072]
Also, Nd: GdVO added with neodymium at a high concentration exceeding 1% in terms of the number of atoms.₄By selecting and exciting an absorption band having a wavelength other than the main absorption band of wavelength 808 nm (for example, the wavelength of 880 nm band) using a crystal, the main absorption band of wavelength 808 nm is selected. As a result, it is possible to improve the quantum conversion efficiency as compared with the excitation, and to obtain highly efficient laser oscillation.
[0073]
Furthermore, Nd: GdVO in which neodymium is added at a high concentration exceeding 1% in terms of the number of atoms.₄When crystals are used, it is possible to select and excite an absorption band in a wavelength band other than the main absorption band of the wavelength 808 nm band (for example, the wavelength of 880 nm band). Although limited to laser diodes having an oscillation wavelength of 808 nm, which is the absorption band, the latitude of selection of the excitation light source can be expanded.
[0074]
Next, FIG. 6 shows a high-concentration neodymium-added gadolinium vanadate crystal (Nd 2%) in which neodymium is added at a concentration of 2% in terms of the number of atoms using a laser apparatus according to the present invention described later with reference to FIG. Addition Gd: VO₄The input / output characteristics of the comparative experiment results when the crystal is excited with excitation light with a wavelength of 808 nm and excitation light with a wavelength of 879 nm in the wavelength 880 nm band are shown.
[0075]
In FIG. 6, the horizontal axis represents the power absorbed in [mW] units (Absorbed Power), that is, the input power of the excitation light, and the vertical axis represents the output power (Output Power) in units of [mW]. Nd: 2% added Gd: VO₄The output power of the laser beam oscillated from the crystal is taken.
[0076]
As understood from FIG. 6, Nd 2% added Gd: VO₄Since neodymium was added to the crystal at a high concentration, very high laser oscillation efficiency was obtained. Specifically, the slope efficiency of laser oscillation was 67% in the case of excitation light having a wavelength of 808 nm, and 78% in the case of excitation light having a wavelength of 879 nm in the wavelength 880 nm band.
[0077]
That is, when excited at a wavelength of 879 nm, which is a wavelength of 880 nm, the slope efficiency is improved by about 10% as compared to the excitation at a wavelength of 808 nm, almost the same as the difference in energy conversion efficiency.
[0078]
Next, the laser device shown in FIG. 7 will be described. The laser device shown in FIG. 7 includes a high-concentration neodymium-added gadolinium vanadate crystal 302 in which neodymium as a laser medium is added at a concentration of 2% in terms of the number of atoms. Titanium sapphire laser 304 as an excitation laser as an excitation light source for generating excitation light for pulse oscillation operation, total reflection mirrors 306 and 308, a λ / 2 wavelength plate 320 for adjusting the intensity and polarization of excitation light, and It has a Grand laser prism 322, a condenser lens 310, and an exit mirror 312.
[0079]
Here, the titanium sapphire laser 304 can be arbitrarily selected in a wavelength range from 700 nm to 950 nm by computer control, the maximum output power is 200 mW on average, and the pulse width is 100 ns and a repetition 1 kHz laser. is there.
[0080]
In the experiment that obtained the experimental results shown in FIG. 6, light having a wavelength of 808 nm or 879 nm was selected and used as excitation light by computer control.
[0081]
The high-concentration neodymium-added gadolinium vanadate crystal 302 is cut to a size of “diameter 8 mm × thickness 1 mm”, and the first surface 302 a facing the titanium sapphire laser 304 all emits light having a wavelength of 1063 nm. The second surface 302b facing the exit mirror 312 is coated so as to be non-reflective with respect to the light having a wavelength of 1063 nm. It has been subjected.
[0082]
Further, the exit mirror 312 has a surface facing the high-concentration neodymium-added gadolinium vanadate crystal 302 as a concave surface 312a having a curvature radius of 200 mm, and the other surface is formed as a flat surface 312b. The concave surface 312a is coated so that the reflectance of light having a wavelength of 1064 nm is 80%, and is configured as a partially reflecting concave mirror. The flat surface 312b is not coded.
[0083]
The condenser lens 310 is made of fused silica glass and has a focal length of 120 mm.
[0084]
Accordingly, in the laser device 300, a resonator is constituted by the first surface 302a and the concave surface 312a, and a high-concentration neodymium-added gadolinium vanadate crystal 302 is disposed as a laser medium in the resonator. It will be. The cavity length of the resonator is set to 3 mm.
[0085]
In the above configuration, when the excitation light emitted from the titanium sapphire laser 304 enters the condenser lens 110 via the total reflection mirrors 306 and 308, the λ / 2 wavelength plate 320, and the Glan laser prism 322, the condenser lens 310 is obtained. Condenses the excitation light and condenses it on the high-concentration neodymium-added gadolinium vanadate crystal 302.
[0086]
In this way, laser oscillation is generated in the resonator, and laser light is emitted from the flat surface 312 b of the emission mirror 312.
[0087]
Since the Glan laser prism 322 transmits only light polarized in a certain direction, the amount of excitation light transmitted through the Glan laser prism 322 can be changed by rotating the λ / 2 wavelength plate 320. Thereby, the power of the excitation light incident on the high concentration neodymium-added gadolinium vanadate crystal 302 was adjusted.
[0088]
In addition, as described above, laser oscillation occurs when excitation light having a wavelength of 880 nm is incident on a high-concentration neodymium-doped gadolinium vanadate crystal.⁴F_3/2It means to be excited to the level.
[0089]
The embodiment described above may be modified as shown in (1) to (4) described below.
[0090]
(1) In the above-described embodiment, the case where neodymium is added to the gadolinium vanadate crystal at a concentration of 2%, 5%, or 10% in terms of the number of atoms has been described in detail. However, the present invention is not limited to this. Needless to say, the concentration of neodymium added to the gadolinium vanadate crystal may be a high concentration such as a concentration exceeding 1% in terms of the number of atoms, preferably a concentration of 2% or more. More preferably, the concentration is 2% to 15%.
[0091]
(2) In the above-described embodiment, the semiconductor laser excitation is based on end face excitation. However, the present invention is not limited to this, and the axis of the optical axis of light that reciprocates through the resonator by laser oscillation. Semiconductor laser excitation may be performed by side excitation in which excitation light is incident on the laser medium from a direction substantially orthogonal to the direction.
[0092]
(3) In the above-described embodiment, the gadolinium vanadate crystal added with neodymium at a high concentration has been described as the laser medium. However, the laser medium to which the present invention can be applied is not limited to this. Of course. For example, it is a single crystal to which Tm, Ho, Er, Cr ions, etc., which are laser active ions, are added at a high concentration as a laser medium, for example, Tm: YVO₄And Tm: GdVO₄The present invention can also be applied to such as. In this case, it is preferable to control the concentration of the sintered body.
[0093]
(4) The above-described embodiment and the modifications shown in (1) to (3) above may be used in appropriate combination.
[0094]
【The invention's effect】
Since the present invention is configured as described above, it has an excellent effect that it can provide a laser oscillation method and a laser apparatus using a laser medium made of a crystal added with laser active ions at a predetermined concentration. Play.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a floating zone method (Floating Zone Method: hereinafter appropriately referred to as “FZ method”), which is a method for producing a laser medium according to an example of an embodiment of the present invention. It is.
FIG. 2 is a graph showing experimental results by the inventors of the present invention, and among the high concentration neodymium-added gadolinium vanadate crystals according to the present invention, the concentration of neodymium is 2%, 5%, 10%, that is, the number of neodymium atoms. Is a graph showing the measurement results of absorption spectra of three types of crystals having a ratio of 2%, 5%, and 10%. The horizontal axis indicates the wavelength (Wavelength) in [nm] units, and the vertical axis indicates [cm.^-1] Absorption coefficient (Absorption coefficient) in units.
FIG. 3 is a graph showing experimental results by the inventors of the present application. In the laser device shown in FIG. It is a graph of the input-output characteristic at the time of using a gadolinium vanadate crystal. The horizontal axis indicates the power absorbed in [W] units (Absorbed Power), and the vertical axis indicates the output power (Output Power) in [W] units.
FIG. 4 is a schematic configuration explanatory diagram showing a laser device that performs a pulse oscillation operation among laser devices configured using a high-concentration neodymium-added gadolinium vanadate crystal as a laser medium.
FIG. 5 is a schematic configuration explanatory diagram showing a laser device that performs a CW (continuous wave) oscillation operation in a laser device configured using a high-concentration neodymium-added gadolinium vanadate crystal as a laser medium.
6 is a graph showing experimental results by the inventors of the present application. In the laser apparatus shown in FIG. 7, high-concentration neodymium addition doped with 2% neodymium in a ratio of the number of atoms as a high-concentration neodymium-added gadolinium vanadate crystal. It is a graph of the input-output characteristic at the time of using a gadolinium vanadate crystal. The horizontal axis indicates the power absorbed in [W] units (Absorbed Power), and the vertical axis indicates the output power (Output Power) in [W] units.
FIG. 7 is a schematic configuration explanatory diagram showing a laser device that performs a pulse oscillation operation among laser devices configured using a high-concentration neodymium-added gadolinium vanadate crystal as a laser medium.
[Explanation of symbols]
10 furnaces
12 Raw material stick
14 Halogen lamp
16 Melting zone (floating zone)
100, 200, 300 Laser equipment
102,302 High concentration Nd-doped YAG single crystal
102a, 302a first surface
102b, 302b second surface
104, 304 Titanium sapphire laser
106, 108, 306, 308 Total reflector
110, 310 condenser lens
112, 208, 312 Output mirror
112a, 208a, 312a Concave surface
112b, 208b, 312b Flat surface
202 laser diode
204 heat sink
206 Gradient index lens
320 λ / 2 wave plate
322 Gran laser prism

Claims (10)

In a laser oscillation method in which a laser medium is excited by excitation light and oscillated,
A laser medium composed of a Nd: GdVO ₄ crystal, which is a GdVO ₄ crystal added so that Nd as a laser active ion has a concentration exceeding 1% in terms of the number of atoms, is different from a wavelength of 808 nm which is a main absorption band. Oscillates by excitation of excitation light with a wavelength of 880 nm.
A laser oscillation method characterized by the above . In a laser oscillation method in which a laser medium is excited by excitation light and oscillated,
A laser medium composed of a Nd: GdVO ₄ crystal, which is a GdVO ₄ crystal added so that Nd as a laser active ion has a concentration of 2% to 15% in terms of the number of atoms, is a wavelength of 808 nm which is a main absorption band. Laser oscillation by excitation of excitation light in a wavelength band of 880 nm which is a different wavelength band
A laser oscillation method characterized by the above . In the laser oscillation method of any one of Claim 1 or 2,
The excitation light of the wavelength 880 nm band is excitation light of wavelength 879 nm.
A laser oscillation method characterized by the above. In the laser oscillation method according to any one of claims 1, 2, and 3,
Excitation light of the wavelength 880nm band, to excite Nd ions from the ground state to the ⁴ F _3/2 level
A laser oscillation method characterized by the above . In the laser oscillation method according to any one of claims 1, 2, 3, or 4,
Nd: GdVO ₄ The crystal is made by the floating zone method
A laser oscillation method characterized by the above. The laser medium disposed in the resonator to bring about lasing within the cavity by incident excitation light to the laser medium, a laser device which emits laser light from the resonator,
The laser medium is a Nd: GdVO ₄ crystal which is a GdVO ₄ crystal added so that Nd as a laser active ion has a concentration exceeding 1% in terms of the number of atoms.
The excitation light is excitation light in a wavelength band of 880 nm that is different from the wavelength band of 808 nm that is the main absorption band.
A laser device characterized by that . A laser device in which a laser medium is disposed in a resonator, and excitation light is incident on the laser medium to cause laser oscillation in the resonator and emit laser light from the resonator;
The laser medium includes GdVO added so that Nd as a laser active ion has a concentration of 2% to 15% in terms of the number of atoms. ₄ Crystal Nd: GdVO ₄ Crystal
The excitation light is excitation light having a wavelength band of 880 nm that is different from the wavelength band of 808 nm that is the main absorption band.
A laser device characterized by that. In the laser apparatus of any one of Claim 6 or 7,
The excitation light of the wavelength 880 nm band is excitation light of wavelength 879 nm.
A laser device characterized by that. The laser apparatus according to any one of claims 6, 7 and 8,
Nd: GdVO ₄ The crystal is made by the floating zone method
A laser device characterized by that. The laser apparatus according to any one of claims 6 , 7, 8 or 9 ,
The excitation light is incident by a semiconductor laser excitation
A laser device characterized by that .

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