JP2013015562A - Optical element and antireflection film transmitting carbon dioxide gas laser beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element and antireflection film that transmit a carbon dioxide gas laser beam and is suitable for irradiation of a high output laser such as a carbon dioxide gas laser.SOLUTION: An optical element 1 includes a Ge substrate 2 having a physical film thickness of 2,075-2,293 nm, a first layer 3 made of YOformed on the Ge substrate 2 and having a physical film thickness of 21-23 nm, a second layer 4 made of ZnS formed on the first layer 3 and having a physical film thickness of 265-293 nm, a third layer 5 made of Ge formed on the second layer 4 and having a physical film thickness of 157-173 nm, a fourth layer 6 made of ZnS formed on the third layer 5 and having a physical film thickness of 588-650 nm, a fifth layer 7 made of YFformed on the fourth layer 6 and having a physical film thickness of 861-952 nm, a sixth layer 8 made of ZnS formed on the fifth layer 7 and having a physical film thickness of 161-178 nm, and a seventh layer 9 made of YOformed on the sixth layer 8 and having a physical film thickness of 21-23 nm.

Description

  The present invention relates to an optical element that transmits carbon dioxide laser light and an antireflection film.

  2. Description of the Related Art Conventionally, there has been known an optical element that forms an antireflection film for light from both a carbon dioxide laser and a YAG laser on both surfaces of a ZnSe lens. (See the invention described in claim 5 of Patent Document 1).

International Publication No. 2007/119838

  Since the optical element described in Patent Document 1 described above corresponds to the light of both a carbon dioxide laser and a YAG laser, it is specialized for either a carbon dioxide laser or a YAG laser. Generally, the performance is inferior to that of an optical element.

  Such performance is, for example, light transmittance. Here, the carbon dioxide laser is a very high-power continuous wave laser that generates an infrared beam. Similarly, YAG laser is a high-power laser. An optical element irradiated with such a high output laser is required to have durability against the irradiation.

  Accordingly, an object of the present invention is to provide an optical element and an antireflection film that transmit carbon dioxide laser light suitable for high-power laser irradiation such as a carbon dioxide laser.

In order to achieve the above object, an optical element that transmits carbon dioxide laser light according to the present invention is a Ge substrate and a first layer formed on the Ge substrate and made of Y ₂ O ₃ having a physical film thickness of 21 to 23 nm. And a second layer made of ZnS having a physical film thickness of 265 to 293 nm and a third layer made of Ge having a physical film thickness of 157 to 173 nm formed on the first layer. A fourth layer made of ZnS having a physical film thickness of 588 to 650 nm formed on the third layer and a fifth layer made of YF ₃ having a physical film thickness of 861 to 952 nm formed on the fourth layer. A sixth layer made of ZnS having a physical film thickness of 161 to 178 nm formed on the fifth layer, and Y ₂ O ₃ having a physical film thickness of 21 to 23 nm formed on the sixth layer. And a seventh layer.

  Here, the refractive index of the substrate is 4.0 to 4.2, the refractive index of the first layer is 1.77 to 1.87, and the refractive index of the second layer is 2.0 to 2.4. Yes, the refractive index of the third layer is 4.0 to 4.2, the refractive index of the fourth layer is 2.0 to 2.4, and the refractive index of the fifth layer is 1.28 to 1.51. The refractive index of the sixth layer is preferably 2.0 to 2.4, and the refractive index of the seventh layer is preferably 1.77 to 1.87.

  Moreover, it is preferable that the wavelength of a carbon dioxide laser beam is 8-11 micrometers.

  Further, the transmittance of the specific region in the range where the wavelength of the carbon dioxide laser beam exceeds 9 μm and 10 μm or less, the transmittance of the specific region in the range where the wavelength of the carbon dioxide laser beam exceeds 8 μm and 9 μm or less, and carbon dioxide gas It is preferable that the wavelength of the laser light is smaller than the transmittance of a specific region in the range of more than 10 μm and not more than 11 μm.

  In order to achieve the above object, the antireflection film that transmits the carbon dioxide laser beam of the present invention includes a first layer, a second layer, and a third layer that constitute an optical element that transmits the carbon dioxide laser beam of the present invention. The fourth layer, the fifth layer, the sixth layer, and the seventh layer are laminated in this order.

  Here, the antireflection film has a transmittance of a specific region in the range where the wavelength of the carbon dioxide laser beam exceeds 9 μm and 10 μm or less, and transmits in a specific region in the range where the wavelength of the carbon dioxide laser beam exceeds 8 μm and 9 μm or less. The transmittance and the wavelength of the carbon dioxide laser beam are preferably smaller than the transmittance of a specific region in the range of more than 10 μm and not more than 11 μm.

  The present invention can provide an optical element and an antireflection film that transmit carbon dioxide laser light suitable for high-power laser irradiation such as a carbon dioxide laser.

It is a longitudinal cross-sectional schematic diagram of the optical element which permeate | transmits the carbon dioxide laser beam which concerns on embodiment of this invention. It is a figure which shows the substance name, refractive index, and physical film thickness of each thin film which comprises the optical element which permeate | transmits the carbon dioxide laser beam which concerns on embodiment of this invention as a table | surface. It is a figure which shows the substance name, refractive index, and physical film thickness of each thin film which comprises the optical element of a comparative example as a table | surface. It is a figure which shows the transmittance | permeability of the anti-reflective film which concerns on embodiment of this invention. It is a figure which shows the transmittance | permeability of the antireflection film of a comparative example.

  Hereinafter, the configuration and manufacturing method of an optical element and an antireflection film that transmit carbon dioxide laser light according to an embodiment of the present invention will be described with reference to the drawings. Further, the difference between the antireflection film of the optical element as a comparative example and the antireflection film of the optical element that transmits the carbon dioxide laser light according to the embodiment of the present invention will be described.

(Configuration of optical element and antireflection film for transmitting carbon dioxide laser beam according to embodiment of present invention)
FIG. 1 is a schematic vertical cross-sectional view of an optical element that transmits carbon dioxide laser light (hereinafter referred to as an optical element 1) according to an embodiment of the present invention. The optical element 1 includes a first layer 3, a second layer 4, a third layer 5, a fourth layer 6, a fifth layer 7, a second layer 7, which will be described later, on both surfaces of a substrate 2 made of Ge having a diameter of 25 mm and a plate thickness of 1 mm. The sixth layer 8 and the seventh layer 9 are respectively the first layer 3, the second layer 4, the third layer 5, the fourth layer 6, the fifth layer 7, the sixth layer 8, and the seventh layer 9 in order from the substrate 2 side. Are formed in this order. FIG. 1 shows a longitudinal section on one surface side of the substrate 2, but the longitudinal section on the other surface side of the substrate 2 also appears in the same manner as FIG.

The substrate 2, the first layer 3, the second layer 4, the third layer 5, the fourth layer 6, the fifth layer 7, the sixth layer 8 and the seventh layer 9 will be described in detail. The substrate 2 is made of Ge having a refractive index of 4.00. A first layer 3 made of Y ₂ O ₃ having a physical film thickness of 22 nm and a refractive index of 1.77 is formed on the substrate 2. A second layer 4 made of ZnS having a physical film thickness of 279 nm and a refractive index of 2.31 is formed on the first layer 3. On the second layer 4, a third layer 5 made of Ge having a physical film thickness of 165 nm and a refractive index of 4.00 is formed. On the third layer 5, a fourth layer 6 made of ZnS having a physical film thickness of 619 nm and a refractive index of 2.12 is formed. A fifth layer 7 made of YF ₃ having a physical film thickness of 906 nm and a refractive index of 1.32 is formed on the fourth layer 6. A sixth layer 8 made of ZnS having a physical film thickness of 170 nm and a refractive index of 2.15 is formed on the fifth layer 7. A seventh layer 9 made of Y ₂ O ₃ having a physical film thickness of 22 nm and a refractive index of 1.77 is formed on the sixth layer 8.

  The substrate 2 and the first layer 3, the second layer 4, the third layer 5, the fourth layer 6, the fifth layer 7, the sixth layer 8 and the seventh layer 9 described above are implemented in the present invention. It becomes the optical element 1 which concerns on a form. In addition, the first layer 3, the second layer 4, the third layer 5, the fourth layer 6, the fifth layer 7, the sixth layer 8 and the seventh layer 9 are antireflection films 10 according to the embodiment of the present invention. It becomes.

  FIG. 2 is a table showing the material names, refractive indices, and physical film thicknesses of the elements constituting the optical element 1.

(Method of manufacturing optical element 1 and antireflection film 10 according to an embodiment of the present invention)
The first layer 3, the second layer 4, the third layer 5, the fourth layer 6, the fifth layer 7, the sixth layer 8, and the seventh layer 9 are formed on both surfaces of the substrate 2 in this order by vacuum deposition. Laminated. At the time of film formation, various conditions of vacuum vapor deposition, such as vapor deposition time and vapor deposition temperature, are adjusted so that each thin film has a target film thickness and refractive index.

(About the optical element of the comparative example)
Similar to the optical element 1, the optical element of the comparative example has a first layer of the comparative example and a comparative example in order from the substrate side of the comparative example on both surfaces of the comparative substrate made of Ge having a diameter of 25 mm and a plate thickness of 1 mm. The second layer, the third layer of the comparative example, the fourth layer of the comparative example, the fifth layer of the comparative example, the sixth layer of the comparative example, and the seventh layer of the comparative example are formed in this order. A schematic longitudinal sectional view of the optical element of the comparative example appears in the same manner as FIG. The substrate 2 of FIG. 1 corresponds to the substrate of the comparative example, the first layer 3 corresponds to the first layer of the comparative example, and the second layer 4 corresponds to the second layer of the comparative example. The third layer 5 corresponds to the third layer of the comparative example, the fourth layer 6 corresponds to the fourth layer of the comparative example, and the fifth layer 7 corresponds to the comparative example. The sixth layer corresponds to the sixth layer 8 of the comparative example, and the seventh layer 9 corresponds to the seventh layer of the comparative example.

  FIG. 3 is a table showing the material names, refractive indices, and physical film thicknesses of the elements constituting the optical element of the comparative example. Comparative Example Substrate and Substrate 2, Comparative Example First Layer and First Layer 3, Comparative Example Second Layer and Second Layer 4, Comparative Example Third Layer and Third Layer 5, Comparative Example Fourth Layer And the fourth layer 6, the fifth layer and the fifth layer 7 of the comparative example, the sixth layer and the sixth layer 8 of the comparative example, and the material names of the seventh layer and the seventh layer 9 of the comparative example are those of the optical element 1. The refractive index and the physical film thickness are different (except for the substrate of the comparative example and the substrate 2).

That is, the substrate of the comparative example is a plate-like member made of Ge having a refractive index of 4.00. A first layer of the comparative example made of Y ₂ O ₃ having a physical film thickness of 16 nm and a refractive index of 1.77 is formed on the substrate of the comparative example. And the 2nd layer of the comparative example which consists of ZnS whose physical film thickness is 200 nm and whose refractive index is 2.31 is formed on the 1st layer of the comparative example. On the second layer of the comparative example, a third layer of the comparative example made of Ge having a physical film thickness of 238 nm and a refractive index of 44.00 is formed. On the third layer of the comparative example, a fourth layer of the comparative example made of ZnS having a physical film thickness of 650 nm and a refractive index of 2.12 is formed. On the fourth layer of the comparative example, a fifth layer of the comparative example made of YF ₃ having a physical film thickness of 920 nm and a refractive index of 1.32 is formed. On the fifth layer of the comparative example, a sixth layer of the comparative example made of ZnS having a physical film thickness of 150 nm and a refractive index of 2.15 is formed. On the sixth layer of the comparative example, a seventh layer of the comparative example made of Y ₂ O ₃ having a physical film thickness of 16 nm and a refractive index of 1.77 is formed.

  What provided the board | substrate of the above comparative example and the 1st-7th layer of a comparative example becomes an optical element of a comparative example. Further, the first to seventh layers of the comparative example are antireflection films of the comparative example. In addition, the first to seventh layers of the comparative example also include the first layer 3, the second layer 4, the third layer 5, the fourth layer 6, the fifth layer 7, the sixth layer 8, and the like according to the embodiment of the present invention. As with the seventh layer 9, the film is formed by vacuum deposition.

(Performance comparison between the optical element 1 according to the embodiment of the present invention and the optical element of the comparative example)
The transmittance of each of the antireflection film 10 and the antireflection film of the comparative example was measured using a Fourier transform infrared spectrometer (FT-IR). The wavelength to be measured was in the range of 7 to 13 μm. This measurement is equivalent to the case where the antireflection film 10 and the antireflection film of the comparative example are irradiated with a high-power carbon dioxide laser beam, which is an infrared beam, emitted from a laser processing machine used for welding, cutting, drilling, etc. Can be evaluated. FIG. 4 is a diagram showing the transmittance of the antireflection film 10 according to the embodiment of the present invention. FIG. 5 is a diagram showing the transmittance of the antireflection film of the comparative example. Here, when the carbon dioxide laser is irradiated to the optical element 1 or the optical element of the comparative example, the substrate 2 or the substrate of the comparative example transmits most of the light and absorbs a part thereof. Specifically, the substrate 2 or the substrate of the comparative example absorbs more light having a wavelength of 10 μm than 8 μm, and further absorbs light having a wavelength of 12 μm from 10 μm. Therefore, the optical element 1 or the optical element of the comparative example has a large decrease in absorption and transmittance. Therefore, the transmittance when the light emitted from the laser processing machine is irradiated to the optical element 1 or the optical element of the comparative example is lower by about 2% than the graphs shown in FIGS. In addition, the curve shape of the graph equivalent to FIG. 4 and FIG. 5 at the time of irradiating the light emitted from a laser processing machine with respect to the optical element 1 or the optical element of a comparative example is the graph shown in FIG. 4 and FIG. The curved shape is generally maintained.

  In the antireflection film 10 according to the embodiment of the present invention, the transmittance of the carbon dioxide laser beam was 0.5 to 1% better in the wavelength range of 9 to 10 μm than the antireflection film of the comparative example. This is because the antireflection film 10 has a thickness of the third layer 5 made of Ge, which is a substance having a large light absorption rate, smaller than that of the third layer of the comparative example of the antireflection film of the comparative example. It is considered that the light absorption rate of the entire film 10 is lowered. Further, when limited to the wavelength range of 8 to 11 μm of the carbon dioxide laser light, the carbon dioxide laser light transmittance of the antireflection film according to the comparative example is the carbon dioxide laser of the antireflection film 101 according to the embodiment of the present invention. It turns out that it is inferior to the light transmittance about 0.2 to 1%.

  Moreover, as shown in FIG. 4, the antireflection film 10 showed a particularly high value in the wavelength range of 8 to 11 μm of the carbon dioxide laser beam, and a value close to about 100% was obtained. Here, as shown in FIG. 4, the transmittance of the specific region A within the range where the wavelength of the carbon dioxide laser beam exceeds 9 μm and 10 μm or less is within the range where the wavelength of the carbon dioxide laser beam exceeds 8 μm and 9 μm or less. It turns out that the transmittance | permeability of the specific area | region B and the wavelength of the carbon dioxide laser beam are smaller than the transmittance | permeability of the specific area | region C in the range which exceeds 10 micrometers and is 11 micrometers or less. The presence of the specific areas A, B, and C shown in FIG. 4 is observed in the same manner as in FIG. 4 when the optical element 1 is irradiated with a carbon dioxide laser.

  Here, the specific region A has a wavelength in the range of 9.2 to 9.9 μm, and the transmittance in the range is 99.7 to 99.8%. The specific region B has a wavelength in the range of 8.4 to 8.9 μm, and the transmittance in that range is 99.9%. The specific region C has a wavelength in the range of 10.6 to 10.8 μm, and the transmittance in the range is 99.9%.

  In addition, when the carbon dioxide laser light is transmitted for a long time to the optical element 1 according to the embodiment of the present invention, the initial performance can be maintained for a long time without being damaged or deteriorated. all right.

(Main effects obtained by the embodiment of the present invention)
The optical element 1 and the antireflection film 10 according to the embodiment of the present invention have high transmittance of carbon dioxide laser light, and have durability that is not damaged or deteriorated even when the carbon dioxide laser light is transmitted for a long time. It was suitable for high-power laser irradiation. In particular, the optical element 1 exhibited a transmittance of 98% or more (not shown) in the wavelength range of 9 to 10.6 μm, and was suitable for the use of transmitting carbon dioxide laser light used in a laser processing machine.

  If only the substrate 2 is irradiated with carbon dioxide laser light having a wavelength in the range of 8 to 11 μm, the transmittance is about 46%. On the other hand, when the optical element 1 is irradiated with a carbon dioxide laser beam having a wavelength in the range of 8 to 11 μm, the transmittance exceeds 97%. Therefore, it can be seen that the antireflection film 10 greatly contributes to suppression of the reflection of the carbon dioxide laser beam.

  Further, the optical element 1 and the antireflection film 10 according to the embodiment of the present invention were able to obtain the performance that the transmittance was particularly high when the wavelength of the carbon dioxide laser beam was in the range of 8 to 11 μm. In particular, at a wavelength of 10.6 μm used in many laser processing machines, the transmittance of the antireflection film 10 is as high as 99.9%.

  Further, the antireflection film 10 according to the embodiment of the present invention and the optical element 1 using the same have a transmittance of the specific region A within the range where the wavelength of the carbon dioxide laser beam exceeds 9 μm and is 10 μm or less. The transmittance of the specific region B within the range where the wavelength of the laser beam exceeds 8 μm and 9 μm or less, and the transmittance of the specific region C within the range where the wavelength of the carbon dioxide laser beam exceeds 10 μm and 11 μm or less. In this way, the presence of the two specific regions B and C having high transmittance can increase the transmittance of the specific region A between the specific regions B and C, and the carbon dioxide laser beam in a wide wavelength region. The antireflection film 10 suitable for transmitting light and the optical element 1 using the same can be provided.

(Other forms)
The optical element 1 and the antireflection film 10 according to the embodiment of the present invention described above are examples of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications are possible without departing from the scope of the present invention. Can be implemented.

An optical element 1 according to an embodiment of the present invention includes a first layer 3, a second layer 4, a third layer 5, a fourth layer 6, a fifth layer 7, and a sixth layer on both surfaces of a plate-like substrate 2. 8 and 7th layer 9 are formed, respectively. A first layer 3 made of Y ₂ O ₃ having a physical thickness of 22 nm is formed on the substrate 2, and a second layer 4 made of ZnS having a physical thickness of 279 nm is formed on the first layer 3. The third layer 5 made of Ge with a physical film thickness of 165 nm is formed on the second layer 4, and the fourth layer 6 made of ZnS with a physical film thickness of 619 nm is formed on the third layer 5. A fifth layer 7 made of YF ₃ having a physical film thickness of 906 nm is formed on the fourth layer 6, and a sixth layer 8 made of ZnS having a physical film thickness of 170 nm is formed on the fifth layer 7. On the sixth layer 8, a seventh layer 9 made of Y ₂ O ₃ having a physical film thickness of 22 nm is formed.

  However, the first layer 3 may have a physical film thickness in the range of 21 to 23 nm. The second layer 4 may have a physical film thickness in the range of 265 to 293 nm. The third layer 5 may have a physical film thickness in the range of 157 to 173 nm. The fourth layer 6 may have a physical film thickness in the range of 588 to 650 nm. The fifth layer 7 may have a physical film thickness in the range of 861 to 952 nm. The sixth layer 8 may have a physical film thickness in the range of 161 to 178 nm. The seventh layer 9 may have a physical film thickness in the range of 21 to 23 nm.

  Within these ranges, a high transmittance and high durability optical element and antireflection film equivalent to those of the optical element 1 and the antireflection film 10 can be obtained. Hereinafter, the substrate 2, the first layer 3, the second layer 4, the third layer 5, the fourth layer 6, the fifth layer 7, the sixth layer 8, and the seventh layer 9 which are each element constituting the optical element 1 In this case, each means one of these physical film thickness ranges. In addition, the optical element 1 or the antireflection film 10 refers to a combination of any one of these elements.

  Moreover, although the board | substrate 2 uses the thing of 25 mm in diameter, the diameter dimension of the board | substrate 2 can be changed suitably. For example, the diameter can be 1 mm to 30 cm, specifically 30 cm, 15 cm, 7 cm, 5 cm, 3 cm, 2 cm, 1 cm, etc. Similarly, the substrate 2 having a plate thickness of 1 mm is used, but the thickness dimension of the substrate 2 can be changed as appropriate. For example, the thickness may be 0.5 mm to 3 cm, specifically 0.5 mm, 2 mm, 5 mm, 1 cm, 2 cm, 3 cm, or the like.

  In the optical element 1 according to the embodiment of the present invention, the refractive index of the substrate 2 is 4.00, the refractive index of the first layer 3 is 1.77, and the refractive index of the second layer 4 is 2. .31, the refractive index of the third layer 5 is 4.00, the refractive index of the fourth layer 6 is 2.12, the refractive index of the fifth layer 7 is 1.32, and the sixth layer The refractive index of 8 is 2.15, and the refractive index of the seventh layer 9 is 1.77.

  However, it is preferable if the refractive index of the substrate 2 is in the range of 4.0 to 4.2. The refractive index of the first layer 3 is preferably in the range of 1.77 to 1.87 (1.79 etc.). The refractive index of the second layer 4 is preferably in the range of 2.0 to 2.4 (2.15, 2.2, 2.3, etc.). The refractive index of the third layer 5 is preferably in the range of 4.0 to 4.2. The refractive index of the fourth layer 6 is preferably in the range of 2.0 to 2.4 (2.15, 2.2, 2.3, etc.). The refractive index of the fifth layer 7 is preferably in the range of 1.28 to 1.51 (1.32, 1.37, etc.). The refractive index of the sixth layer 8 is preferably in the range of 2.0 to 2.4 (2.15, 2.2, 2.3, etc.). The refractive index of the seventh layer 9 is preferably in the range of 1.77 to 1.87 (1.79 etc.).

  Even when the refractive index is out of the range, if the physical film thickness of the substrate 2 and each layer satisfies the above range, an optical element with high transmittance and high durability substantially equivalent to the optical element 1 can be obtained. Can be obtained. However, better optical transmittance with higher transmittance and higher durability can be obtained when these refractive index ranges are satisfied. Hereinafter, the substrate 2, the first layer 3, the second layer 4, the third layer 5, the fourth layer 6, the fifth layer 7, the sixth layer 8, and the seventh layer, which are elements constituting the optical element 1, are described. Each of 9 refers to any one of these refractive index ranges. The optical element 1 or the antireflection film 10 refers to a combination of any one of these refractive index ranges for each element.

  For example, in the example in which the refractive index of the substrate 2 and each layer is suitable, the refractive index of the substrate 2 is 4.10, the refractive index of the first layer 3 is 1.82, and the refractive index of the second layer 4 is 2.20, the refractive index of the third layer 5 is 4.10, the refractive index of the fourth layer 6 is 2.20, the refractive index of the fifth layer 7 is 1.40, and the refraction of the sixth layer 8 is The refractive index is 2.20, and the refractive index of the seventh layer 9 is 1.82.

  In addition, the optical element 1 and the antireflection film 10 according to the embodiment of the present invention can obtain good high transmittance when the wavelength of the transmitted carbon dioxide laser beam is in the range of 8 to 11 μm. However, it can also be used for applications that transmit carbon dioxide laser light having a wavelength of less than 8 μm and a wavelength of more than 11 μm. In an optical element that transmits carbon dioxide laser light having a wavelength of less than 8 μm and a wavelength of more than 11 μm, the thickness or refractive index of each layer is preferably changed from that of the optical element 1 and the antireflection film 10 within the above range. The optical element 1 and the antireflection film 10 exhibit very good high transmittance and high durability in the range of 9.4 to 10.6 μm, which is the main wavelength band of the carbon dioxide gas laser.

  Further, in the optical element 1 and the antireflection film 10 according to the embodiment of the present invention, the transmittance of the specific region A within the range where the wavelength of the carbon dioxide laser beam exceeds 9 μm and is 10 μm or less is the wavelength of the carbon dioxide laser beam. Is less than the transmittance of the specific region B within the range of more than 8 μm and not more than 9 μm, and the transmittance of the specific region C within the range of the wavelength of the carbon dioxide laser beam exceeding 10 μm and not more than 11 μm.

  However, such specific areas A, B, and C are not particularly necessary. For example, you may make it have only one maximum value area | region of the transmittance | permeability like the specific area | regions B and C in the wavelength range of 8-11 micrometers. However, an optical element and an antireflection film having only one maximum value region of such transmittance are difficult to obtain high transmittance over a wide wavelength range. On the contrary, you may make it have the maximum value area | region of the transmittance | permeability like the specific area | regions B and C in the wavelength range 8-11 micrometers in three, four, five, or six. As described above, the optical element and the antireflection film having the maximum value region of three or more transmittances in the wavelength range of 8 to 11 μm can obtain high transmittances over a wider wavelength range.

  The specific region A has a wavelength in the range of 9.2 to 9.9 μm, and the transmittance in the range is 99.7 to 99.8%. The specific region B has a wavelength in the range of 8.4 to 8.9 μm, and the transmittance in that range is 99.9%. The specific region C has a wavelength in the range of 10.6 to 10.8 μm, and the transmittance in the range is 99.9%.

  However, the wavelength ranges of the specific areas A, B, and C may be other values. The specific region A preferably has a wavelength of carbon dioxide laser light in the range of more than 9 μm and not more than 10 μm. For example, the specific region A has a wavelength of carbon dioxide laser light in the range of more than 8 μm and not more than 9 μm. Also good. The specific region B preferably has a carbon dioxide laser beam wavelength in the range of more than 8 μm and less than 9 μm. For example, the specific region B has a wavelength of the carbon dioxide laser beam in the range of more than 7 μm and less than 8 μm. There may be. The specific region C is preferably in the range where the wavelength of the carbon dioxide laser beam is more than 10 μm and 11 μm or less, for example, the wavelength of the carbon dioxide laser beam is in the range of more than 9 μm and 11 μm or less. There may be.

  Further, the transmittance of the specific areas A, B, and C may be other values. The transmittance of the specific area A may be, for example, 99.4 to 99.6%. The transmittance of the specific region B may be 99.7 to 99.8%, for example. The transmittance of the specific area C may be 99.5 to 99.7%, for example.

  As shown in FIG. 4, in the wavelength range of 8 to 11 μm, the specific region A that is the minimum value region of the transmittance is sandwiched between the specific regions B and C that are the maximum value region of the transmittance. However, the maximum value region of the transmittance may be sandwiched between the minimum value regions of the transmittance in the wavelength range of 8 to 11 μm. Further, in the wavelength range of 8 to 11 μm, the number of the transmittance minimum value region and the transmittance maximum value region may be the same. As described above, the adjustment of the number of the minimum value region and the maximum value region of the transmittance, and the adjustment of the wavelength region where the minimum value region of the transmittance and the maximum value region of the transmittance appear, This is possible by adjusting the thickness and refractive index of each constituent layer.

  In the optical element 1, antireflection films 10 are formed (film formation) on both surfaces of the substrate 2. However, when there is no problem in reducing the transmittance of the laser beam depending on the application, the antireflection film 10 is formed only on the surface of the substrate 2 on the side irradiated with the carbon dioxide laser beam or only on the opposite surface. You may make it form. In this way, the transmittance of the carbon dioxide laser beam is slightly reduced, but the degree of the decrease is within an acceptable range.

  In the present embodiment, the first layer 3, the second layer 4, the third layer 5, the fourth layer 6, the fifth layer 7, the sixth layer 8 and the seventh layer 9 constituting the antireflection film 10 are formed ( A vacuum deposition method was employed for film formation. However, an ion-assisted vapor deposition method or the like can be employed instead of the vacuum vapor deposition method.

  In the present embodiment, carbon dioxide laser light emitted from a laser processing machine is transmitted through the optical element 1 to obtain good high transmittance and high durability. However, the optical element 1 can obtain good high transmittance and high durability even when carbon dioxide laser light used in the medical field such as a laser knife is transmitted.

  Further, the optical element 1 and the antireflection film 10 can be used not only for the purpose of transmitting carbon dioxide laser light but also as an optical component using infrared rays such as a sensor and a monitoring camera. With respect to optical parts using infrared rays such as sensors and surveillance cameras, good transmittance can be obtained in a wide band with a light wavelength of 8 to 12 μm.

  The optical element 1 uses Ge for the substrate 2. However, instead of Ge, for example, Si, ZnSe, or cargoogenide glass can be used as the material of the substrate. The material of these substrates can be changed depending on the use of the optical element in which the antireflection film is used.

1 Optical elements (optical elements that transmit carbon dioxide laser light)
2 Substrate 3 1st layer 4 2nd layer 5 3rd layer 6 4th layer 7 5th layer 8 6th layer 9 7th layer 10 Antireflection film A The wavelength of carbon dioxide laser beam is over 9 μm and within 10 μm Specific region B Specific region in the range where the wavelength of the carbon dioxide laser beam exceeds 8 μm and 9 μm or less C Specific region in the range where the wavelength of the carbon dioxide laser beam exceeds 10 μm and 11 μm or less

Claims (6)

In an optical element that transmits carbon dioxide laser light,
A Ge substrate;
A first layer made of Y ₂ O ₃ having a physical film thickness of 21 to 23 nm formed on the Ge substrate;
A second layer made of ZnS having a physical film thickness of 265 to 293 nm, formed on the first layer;
A third layer made of Ge having a physical film thickness of 157 to 173 nm, formed on the second layer;
A fourth layer made of ZnS having a physical film thickness of 588 to 650 nm, formed on the third layer;
A fifth layer made of YF ₃ having a physical film thickness of 861 to 952 nm formed on the fourth layer;
A sixth layer made of ZnS having a physical film thickness of 161 to 178 nm, formed on the fifth layer;
And a seventh layer made of Y ₂ O ₃ having a physical film thickness of 21 to 23 nm, which is formed on the sixth layer. In the optical element which transmits the carbon dioxide laser beam according to claim 1,
The refractive index of the substrate is 4.0 to 4.2,
The refractive index of the first layer is 1.77 to 1.87,
The refractive index of the second layer is 2.0 to 2.4,
The refractive index of the third layer is 4.0 to 4.2,
The refractive index of the fourth layer is 2.0 to 2.4,
The refractive index of the fifth layer is 1.28 to 1.51.
The refractive index of the sixth layer is 2.0 to 2.4,
An optical element that transmits carbon dioxide laser light, wherein the seventh layer has a refractive index of 1.77 to 1.87. In the optical element which permeate | transmits the carbon dioxide laser beam of Claim 1 or 2,
An optical element that transmits carbon dioxide laser light, wherein the carbon dioxide laser light has a wavelength of 8 to 11 μm. In the optical element which permeate | transmits the carbon dioxide laser beam of any one of Claim 1 to 3,
The transmittance of the specific region in the range where the wavelength of the carbon dioxide laser beam exceeds 9 μm and 10 μm or less, the transmittance of the specific region in the range where the wavelength of the carbon dioxide laser beam exceeds 8 μm and 9 μm or less, and the carbon dioxide laser beam An optical element that transmits carbon dioxide laser light, characterized in that the wavelength of is less than the transmittance of a specific region within a range of more than 10 μm and not more than 11 μm.   The first layer, the second layer, the third layer, the fourth layer, the fifth layer, the sixth layer, and the seventh layer according to claim 1 or 2, Are laminated in this order, an antireflection film that transmits carbon dioxide laser light. The antireflection film according to claim 5,
The transmittance of the specific region in the range where the wavelength of the carbon dioxide laser beam exceeds 9 μm and 10 μm or less, the transmittance of the specific region in the range where the wavelength of the carbon dioxide laser beam exceeds 8 μm and 9 μm or less, and the carbon dioxide laser beam An antireflection film having a wavelength less than 10 μm and less than a specific region within a range of 11 μm or less.

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