Immersion Diffraction Elements

Abstract

To provide an immersion diffraction element that can suppress diffraction defect and in which a diffraction part hardly breaks.SOLUTION: An immersion diffraction element 1 includes: a diffraction part 4; a main body part 2 including a rib 5 provided around the diffraction part 4; and a lid part 6 provided on the rib 5.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an immersion diffraction element. [Background technology]

[0002] In the past, immersion diffraction elements have been proposed that can achieve both improved wavelength resolution and compactness. With the recent advances in microfabrication and material technology, it has become possible to realize immersion diffraction elements, and immersion diffraction elements have attracted attention.

[0003] The immersion diffraction element has a configuration in which, for example, a prism is provided with a diffraction section. A plurality of diffraction grooves are periodically provided in the diffraction section. When the immersion diffraction element disperses light, the light passes through the prism and is reflected and dispersed at the diffraction section. The dispersed light is then emitted from the prism.

[0004] If the refractive index of a prism is n, the wavelength of light becomes 1 / n when it passes through a prism. Therefore, the pitch of the diffraction grooves required for dispersion becomes 1 / n. Therefore, even if the immersion diffraction element is made small, a large number of diffraction grooves can be provided, and the wavelength resolution can be improved.

[0005] The following Patent Document 1 discloses a diffraction grating as an example of an immersion diffraction element. In this diffraction grating, grating grooves are provided in a crystal material of InP or InAs. The grating grooves include a surface that is a (110) crystal orientation surface of the crystal material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-121605 A Summary of the Invention [Problem to be solved by the invention]

[0007] When an optical device using an immersion diffraction element is used, foreign matter may adhere to the surface of the diffractive portion of the immersion diffraction element. In this case, there is a risk of a problem with the diffraction of light by the immersion diffraction element. Furthermore, there is a risk of the diffractive portion being damaged when the foreign matter is removed from the surface of the immersion diffraction element.

[0008] An object of the present invention is to provide an immersion diffraction element that can suppress diffraction defects and has a diffractive portion that is less susceptible to damage. [Means for solving the problem]

[0009] The immersion diffraction element according to the present invention is characterized by comprising a main body portion having a diffractive portion and a rib provided so as to surround the diffractive portion, and a lid portion provided on the rib.

[0010] The absolute value of the difference in thermal expansion coefficient between the material that constitutes the rib and the material that constitutes the lid is 170 x 10 -7 / °C or less.

[0011] The diffractive portion is preferably made of amorphous glass.

[0012] Preferably, the ribs are made of glass.

[0013] The lid is preferably made of glass, ceramic, metal or resin.

[0014] It is preferable that the diffractive portion and the rib are integrally provided on the main body portion.

[0015] It is preferable that the main body portion includes a prism portion, and the prism portion and the diffraction portion are provided integrally. Alternatively, it is preferable that the main body portion includes a prism portion having a main surface, and the diffraction portion is provided on the main surface of the prism portion. Effect of the Invention

[0016] According to the present invention, it is possible to provide an immersion diffraction element that can suppress diffraction defects and has a diffractive portion that is less likely to be damaged. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view of an immersion diffraction element according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a view of the main body of the immersion diffraction element according to the first embodiment of the present invention, viewed from the normal direction of the first surface of the prism portion. [Diagram 3] FIG. 3 is a schematic cross-sectional view, with ribs omitted, for explaining light dispersion in the main body of the immersion diffraction element of the present invention. [Figure 4] FIG. 4 is an enlarged view of the diffractive portion in FIG. [Diagram 5] FIG. 5 is a cross-sectional view of an immersion diffraction element according to a modified example of the first embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view of an immersion diffraction element according to the second embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view of an immersion diffraction element according to the third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Preferred embodiments will be described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[0019] (First embodiment) Fig. 1 is a cross-sectional view of an immersion diffraction element according to a first embodiment of the present invention, taken along line II in Fig. 2, which will be described later.

[0020] The immersion diffraction element 1 has a main body 2. The main body 2 includes a prism portion 3, a diffraction portion 4, and a rib 5. In the main body 2 of this embodiment, the prism portion 3, the diffraction portion 4, and the rib 5 are provided as an integral unit. However, the prism portion 3, the diffraction portion 4, and the rib 5 may each be provided as a separate body.

[0021] The prism portion 3 has a triangular prism shape. The prism portion 3 has a first surface 3a, a second surface 3b, and a third surface 3c. These surfaces correspond to the side surfaces of the triangular prism shape. A plurality of diffraction grooves 4d are periodically provided on the first surface 3a of the prism portion 3. This constitutes the diffraction portion 4. More specifically, the plurality of diffraction grooves 4d are provided so that the diffraction portion 4 has a stepped shape. Each diffraction groove 4d has a fourth surface 4a and a fifth surface 4b. In this embodiment, the fourth surface 4a and the fifth surface 4b are perpendicular to each other.

[0022] FIG. 2 is a view of the main body of the immersion diffraction element according to the first embodiment, viewed from the normal direction of the first surface of the prism portion.

[0023] A rib 5 is provided on the first surface 3a of the prism portion 3 so as to surround the diffraction portion 4. The rib 5 has a frame shape when viewed from the normal direction of the first surface 3a. More specifically, the rib 5 has an opening 5a and an open end surface portion 5b. The diffraction portion 4 is disposed within the opening 5a.

[0024] Returning to FIG. 1, a lid portion 6 is provided on the rib 5 of the main body portion 2. More specifically, the lid portion 6 is provided on the open end surface portion 5b of the rib 5 so as to close the opening portion 5a of the rib 5. In this embodiment, the lid portion 6 is joined to the entire surface of the open end surface portion 5b of the rib 5. However, the open end surface portion 5b of the rib 5 may have a portion that is not joined to the lid portion 6. It is sufficient that the opening portion 5a of the rib 5 is closed by the lid portion 6.

[0025] The lid portion 6 has a plate-like shape. When viewed from the thickness direction of the lid portion 6, the shape of the lid portion 6 is rectangular. However, the shape of the lid portion 6 viewed from the above direction is not limited to a rectangle, and may be a circle, an ellipse, or a polygon other than a rectangle. The lid portion 6 may be configured to close the opening 5a of the rib 5.

[0026] Fig. 3 is a schematic cross-sectional view, with ribs omitted, for explaining light separation in the main body of the immersion diffraction element. Fig. 4 is an enlarged view of the diffraction part in Fig. 3. No hatching is applied in Figs. 3 and 4.

[0027] As shown in FIG. 3, the second surface 3b of the prism portion 3 is the entrance portion of the immersion diffraction element 1. The diffraction portion 4 includes a bottom point portion 4c shown in FIG. 4. More specifically, the diffraction portion 4 includes a plurality of bottom points 4c. As shown in FIG. 3, the light A enters from the second surface 3b, passes through the prism portion 3, and reaches the diffraction portion 4. The light A is then reflected and diffracted at each of the fourth surfaces 4a and each bottom point portion 4c in the diffraction portion 4, and is dispersed. The dashed arrow and the dashed arrow in FIG. 3 show an example of dispersed light. The dispersed light is output from the prism portion 3. As shown by the wavy line in FIG. 3, the wavelength of the light A inside the prism portion 3 is shorter than the wavelength of the light A outside the prism portion 3. Therefore, the pitch of the diffraction groove 4d required for dispersion can be shortened. Therefore, in the immersion diffraction element 1, it is possible to achieve both improved wavelength resolution and miniaturization.

[0028] Returning to FIG. 1, the feature of this embodiment is that the rib 5 is provided so as to surround the diffractive portion 4, and the lid portion 6 is provided on the rib 5. Since the diffractive portion 4 is protected by the lid portion 6 and the rib 5, foreign matter is unlikely to adhere to the surface of the diffractive portion 4. Therefore, even over a long period of use, problems are unlikely to occur in the diffraction by the immersion diffraction element 1. Furthermore, since foreign matter is unlikely to adhere to the surface of the diffractive portion 4, it is unlikely that a member for removing foreign matter will come into contact with the diffractive portion 4, or that foreign matter will peel off from the diffractive portion 4. Therefore, the diffractive portion 4 is unlikely to be damaged. In addition, when the immersion diffraction element 1 is used in an optical device or the like, the rib 5 and the lid portion 6 can also protect the diffractive portion 4 from contact with other elements. In this way, the diffractive portion 4 is even less likely to be damaged.

[0029] Examples of materials for each member of the immersion diffraction element 1 are given below.

[0030] The prism portion 3 may be made of, for example, Si or glass. When glass is used for the prism portion 3, amorphous glass may be used. In this specification, the term "amorphous glass" refers to glass that shows no crystal peak and has a halo pattern specific to glass in a powder X-ray diffraction measurement. As the amorphous glass, for example, chalcogenide glass may be used. The composition of the amorphous glass preferably contains, in molar percentage, Te 4% to 80%, Ge 0% to 50% (but not including 0%), and Ga 0 to 20%. Alternatively, the composition of the amorphous glass preferably contains, in molar percentage, S 50% to 80%, Sb 0% to 40% (but not including 0%), Ge 0% to 18% (but not including 0%), Sn 0% to 20%, and Bi 0% to 20%.

[0031] For the diffraction portion 4, for example, the same glass as the glass given as an example of the material of the prism portion 3 can be used. Note that, for the diffraction portion 4, it is preferable to use amorphous glass similar to the amorphous glass given as an example of the material of the prism portion 3.

[0032] For example, glass, ceramic, metal, or resin can be used for the rib 5. For the rib 5, glass is preferably used, and amorphous glass similar to the amorphous glass given as an example of the material for the prism portion 3 is more preferably used.

[0033] The lid 6 may be made of, for example, glass, ceramic, metal or resin.

[0034] The absolute value of the difference in thermal expansion coefficient between the material constituting the rib 5 and the material constituting the lid portion 6 is 170×10 -7 / ℃ or less, and 150×10 -7 / ° C. or less, it is more preferable. This makes it difficult for the lid portion 6 to peel off from the rib 5 due to the difference in the amount of thermal expansion or contraction when a temperature change occurs.

[0035] As in this embodiment, it is preferable that the prism section 3 and the diffraction section 4 are provided integrally. In this case, the immersion diffraction element 1 does not have an interface between the prism section 3 and the diffraction section 4. Therefore, light is not reflected at the interface, and the light utilization efficiency can be effectively improved.

[0036] It is preferable that the diffraction portion 4 and the rib 5 are provided as one piece. This allows the diffraction portion 4 and the rib 5 to be formed simultaneously, thereby improving productivity. Specifically, for example, the diffraction portion 4 and the rib 5 may be formed by mold press molding on a surface of the prism, which is the base material of the main body portion 2, that corresponds to the first surface 3a shown in FIG. 1. In particular, when the immersion diffraction element 1 is made small, the distance between the diffraction portion 4 and the rib 5 becomes narrow. Therefore, when the diffraction portion 4 and the rib 5 are provided separately, high-precision positioning is required. In contrast, when mold press molding is used as described above, positional deviation between the diffraction portion 4 and the rib 5 is unlikely to occur. In this way, the immersion diffraction element 1 can be easily made small.

[0037] The rib 5 and the lid 6 are preferably bonded by a room temperature bonding method such as optical contact or surface activation bonding. This makes it difficult for residual stress to occur at the bonded portion between the rib 5 and the lid 6, and makes it difficult for the lid 6 to peel off. In the above case, the rib 5 and the lid 6 are bonded without using any other member. However, the rib 5 and the lid 6 may also be bonded by an adhesive or the like.

[0038] As described above, the diffractive portion 4 and the rib 5 may be provided as separate bodies. This example is shown as a modified example.

[0039] (Modification) 5, a rib 15 is provided on the first surface 13a of the prism portion 13. The rib 15 is provided so as to surround the diffraction portion 4. In this modification, similar to the first embodiment, problems are unlikely to occur in the diffraction by the immersion diffraction element, and the diffraction portion 4 is unlikely to be damaged.

[0040] It is preferable that the prism portion 13 and the rib 15 are bonded by a room temperature bonding method such as optical contact or surface activation bonding. This makes it difficult for residual stress to occur at the bonded portion between the prism portion 13 and the rib 15, and makes it difficult for the rib 15 to peel off. In the above case, the prism portion 13 and the rib 15 are bonded without using any other member. However, the prism portion 13 and the rib 15 may also be bonded by an adhesive or the like.

[0041] Second embodiment FIG. 6 is a cross-sectional view of an immersion diffraction element according to the second embodiment of the present invention.

[0042] This embodiment differs from the first embodiment in that the prism portion 23 is provided as a separate body from the diffraction portion 24 and the ribs 5. Except for the above, the immersion diffraction element 21 of this embodiment has the same configuration as the immersion diffraction element 1 of the first embodiment.

[0043] The diffraction section 24 of the immersion diffraction element 21 has a plate-shaped member 27. The plate-shaped member 27 has a diffraction-section forming surface 27a and a bonding surface 27b. The diffraction-section forming surface 27a and the bonding surface 27b face each other. A plurality of diffraction grooves 4d are periodically provided on the diffraction-section forming surface 27a. This forms the diffraction section 24. The shape of the diffraction grooves 4d is the same as in the first embodiment.

[0044] The diffractive portion 24 and the rib 5 are provided integrally. More specifically, the rib 5 is provided so as to surround a portion where the plurality of diffraction grooves 4d are provided on the diffractive portion forming surface 27a of the plate-shaped member 27. The diffractive portion 24 and the rib 5 in this embodiment can be obtained by, for example, mold press molding.

[0045] On the other hand, the prism portion 23 has a first surface 23a, a second surface 3b, and a third surface 3c. The second surface 3b and the third surface 3c are configured in the same manner as in the first embodiment. The first surface 23a is the main surface of the prism portion in the present invention. The diffraction portion 24 is provided on the first surface 23a. More specifically, the first surface 23a and a bonding surface 27b of the plate-like member 27 are bonded to each other.

[0046] The prism section 23 and the diffraction section 24 may be bonded by a room temperature bonding method such as optical contact or surface activation bonding. It is preferable that the prism section 23 and the diffraction section 24 are bonded by optical contact. This makes it possible to more reliably prevent the generation of a gap between the prism section 23 and the diffraction section 24. Therefore, reflection is less likely to occur between the prism section 23 and the diffraction section 24, and the light utilization efficiency can be more reliably improved.

[0047] In this embodiment, the prism portion 23 and the diffraction portion 24 are bonded together without any other member. A base film may be provided between the prism portion 23 and the diffraction portion 24. The base film may be used as a bonding member. The base film may be made of, for example, Si.

[0048] 6, in the present embodiment, as in the first embodiment, the rib 5 is provided so as to surround the diffractive portion 24, and the lid portion 6 is provided on the rib 5. Since the diffractive portion 24 is protected by the lid portion 6 and the rib 5, problems are unlikely to occur in the diffraction by the immersion diffraction element 21, and the diffractive portion 24 is unlikely to be damaged.

[0049] The absolute value of the difference in thermal expansion coefficient between the material constituting the prism portion 23 and the material constituting the diffraction portion 24 is 170×10 -7 / ℃ or less, and 150×10 -7 / ° C. or less. This makes it difficult for the diffraction section 24 to peel off from the prism section 23 even when a temperature change occurs.

[0050] The absolute value of the refractive index difference at a wavelength of 10 μm between the material constituting prism section 23 and the material constituting diffractive section 24 is preferably 0.3 or less, and more preferably 0.25 or less. In this case, light reflection at the interface between prism section 23 and diffractive section 24 is suppressed, thereby improving the light utilization efficiency.

[0051] (Third embodiment) FIG. 7 is a cross-sectional view of an immersion diffraction element according to the third embodiment of the present invention.

[0052] This embodiment differs from the first embodiment in that an anti-reflection film 38 is provided on the second surface 3b of the prism portion 3, and the surface of the diffraction portion 4 is covered with a reflective film 39. Specifically, the reflective film 39 covers the fourth surface 4a and the fifth surface 4b of the diffraction portion 4. Except for the above points, the immersion diffraction element 31 of this embodiment has the same configuration as the immersion diffraction element 1 of the first embodiment.

[0053] The second surface 3b of the prism portion 3 is an incident portion of the immersion diffraction element 31. By providing the anti-reflection film 38 on the incident portion, the incident light is less likely to be reflected. This can improve the light utilization efficiency. The anti-reflection film 38 is preferably made of at least one selected from Ge, Si, fluoride, ZnSe, ZnS, and diamond-like carbon.

[0054] As described above, the surface of the diffraction section 4 is covered with the reflective film 39. This allows the light incident on the prism section 3 to be more reliably reflected by the diffraction section 4, and more reliably split. For the reflective film 39, a metal such as Au can be used, and Si may be used as an undercoat film for Au. In this case, the reflection and splitting of the incident light can be performed easily and more reliably.

[0055] Additionally, in the present embodiment, similarly to the first embodiment, the rib 5 is provided so as to surround the diffractive portion 4, and the lid portion 6 is provided on the rib 5. Since the diffractive portion 4 is protected by the lid portion 6 and the rib 5, problems are unlikely to occur in the diffraction by the immersion diffraction element 31, and the diffractive portion 4 is unlikely to be damaged. [Explanation of symbols]

[0056] 1...Immersion diffraction element 2…Main body 3...Prism section 3a~3c...1st~3rd sides 4...Diffraction section 4a, 4b...4th and 5th sides 4c…Bottom point part 4d…Diffraction groove 5…Rib 5a...Opening 5b...Opening end face part 6…Lid part 13...Prism section 13a…First side 15…Rib 21...Immersion diffraction element 23...Prism section 23a…First side 24...Diffraction section 27...Plate-shaped member 27a...diffraction portion forming surface 27b...joint surface 31...Immersion diffraction element 38…Anti-reflection film 39...Reflection film

Claims

1. A main body portion having a diffractive portion and a rib provided so as to surround the diffractive portion; A lid portion that is separate from the rib and is provided on the rib; Equipped with the main body portion includes a prism portion having a main surface, the diffraction portion and the rib are provided on the main surface of the prism portion, When viewed from a normal direction of the main surface of the prism portion, the rib is located inside an outer circumferential edge of the main surface, An immersion diffraction element, wherein the prism portion, the diffraction portion, and the ribs are integrally provided.

2. The absolute value of the difference in thermal expansion coefficient between the material constituting the rib and the material constituting the lid is 170×10 －７ 2. The immersion diffraction element according to claim 1, wherein the temperature is 0.15 to 1.0° C. or less.

3. 3. The immersion diffraction element according to claim 1, wherein the diffractive portion is made of amorphous glass.

4. 4. The immersion diffraction element according to claim 1, wherein the ribs are made of amorphous glass.

5. 5. The immersion diffraction element according to claim 1, wherein the cover portion is made of glass, ceramic, metal or resin.

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