JP2006323059A - Structural birefringent wavelength plate and wavelength plate combined structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structural birefringent wavelength plate, having high zeroth-order light transmittance and ensuring improved stability of the zeroth-order light transmittance with respect to structural height errors by processing, and to provide a wavelength plate combined structure. <P>SOLUTION: The structural birefringent wavelength plate 1 has a peak-valley periodic structure, formed by periodically repeating a columnar portion 6 and a groove 6', where at least one of the tip of the columnar portion and the bottom of the groove is formed into a trapezoid with a flat part 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a structural birefringent wave plate having a concavo-convex periodic structure and a wave plate combination structure.

  Conventionally, the structural birefringent wave plate generally has a structure in which rectangular gratings are periodically arranged. However, according to such a rectangular lattice shape, when the structural period is not sufficiently small with respect to the wavelength, first-order or higher-order diffracted light is generated, so that a high zero-order light transmittance is obtained. Was difficult. Further, since the 0th-order light transmittance at this time periodically varies with the change in the structure height, it is a problem that the transmittance is greatly reduced due to a structure height error generated during processing. It was.

Patent Document 1 below proposes a structure in which the structural period is ½ or less of the wavelength and the groove width of the grating is widened toward the surface at the top of the groove (Claim 6). A groove having a sawtooth cross section is formed on the surface opposite to the surface on which the light is formed with a period of 1/2 or less of the wavelength, thereby preventing light reflection and improving the transmittance (Claim 7). . However, Patent Document 1 listed below does not describe periodic fluctuations associated with changes in the structural height of transmittance.
JP 2004-133290 A (FIG. 8)

  In view of the above-mentioned problems of the prior art, the present invention has a structural birefringence wavelength that has a high zero-order light transmittance and has improved stability of the zero-order light transmittance with respect to a structural height error caused by processing. An object is to provide a plate and wave plate combination structure.

  In order to achieve the above object, a structural birefringent wave plate according to the present invention has an uneven periodic structure in which a columnar portion and a groove portion are periodically repeated, and is formed at the tip of the columnar portion and the bottom of the groove portion. At least one is configured in a trapezoidal shape having a flat portion.

  According to this structural birefringent wave plate, the 0th-order light transmittance is high, and the periodic fluctuation accompanying the change in the structural height of the 0th-order light transmittance is small. Even if an error occurs, the 0th-order light transmittance does not vary with respect to the structural height error, and is stabilized.

  In the structural birefringent wavelength plate, a tip of the columnar part has a flat part, and the groove part has a substantially triangular shape so as to gradually narrow from the flat part toward the bottom part.

  Further, the bottom portion of the groove portion has a flat portion, and the columnar portion can be configured to have a substantially triangular shape so as to gradually narrow from the flat portion toward the tip.

  Moreover, it can comprise so that the front-end | tip of the said columnar part and the bottom part of the said groove part may have a flat part, respectively.

Further, when the structure period of the concave-convex periodic structure is P, the structure height is H, and the width of the flat part of the columnar part is L1, the following expressions (1) and (2) are satisfied. The light transmittance is 98% or more.
When P ≦ λ / n, 0.16 ≦ H / λ and 0 <L1 / P ≦ 0.55 (1)
When P> λ / n, 0.85 ≦ H / λ and 0 <L1 / P ≦ 0.55 (2)
However, P <λ
λ: wavelength used n: refractive index of wave plate material at wavelength λ used

Furthermore, when the following expressions (3) and (4) are satisfied, the average 0th-order light transmittance is 99% or more.
When P ≦ λ / n, 0.22 ≦ H / λ ≦ 3.7 and 0 <L1 / P ≦ 0.35 (3)
When P> λ / n, 1.15 ≦ H / λ ≦ 3.7 and 0 <L1 / P ≦ 0.35 (4)
However, P <λ

Further, when the structure period of the concavo-convex periodic structure is P, the structure height is H, and the width of the flat portion of the groove is L2, the following expressions (5) and (6) are satisfied. The transmittance is 98% or more.
When P ≦ λ / n, 0.17 ≦ H / λ and 0 <L2 / P ≦ 0.2 (5)
When P> λ / n, 1.00 ≦ H / λ and 0 <L2 / P ≦ 0.2 (6)
However, P <λ
L1 + L2 <P
λ: wavelength used n: refractive index of wave plate material at wavelength λ used

Furthermore, when the following expressions (7) and (8) are satisfied, the average 0th-order light transmittance is 99% or more.
When P ≦ λ / n, 0.23 ≦ H / λ ≦ 3.7 and 0 <L2 / P ≦ 0.1 (7)
When P> λ / n, 1.28 ≦ H / λ ≦ 3.7 and 0 <L2 / P ≦ 0.1 (8)
However, P <λ
L1 + L2 <P
λ: wavelength used n: refractive index of wave plate material at wavelength λ used

  Moreover, it is preferable that the said uneven | corrugated periodic structure is formed by imprinting to resin using a shaping die.

  The combined wave plate combination structure according to the present invention is characterized in that a plurality of the above-described structural birefringent wave plates are combined.

  According to this wave plate combination structure, when a desired phase difference is obtained by combining a plurality of structural birefringent wave plates, each structural birefringent wave plate is substantially constant at any structural height and has a high zero-order light transmittance. Therefore, the structural dimension of each structural birefringent wave plate can be determined only by a combination of phase differences, and the degree of freedom in design is improved. In particular, if two structural birefringent wave plates that can obtain a phase difference that is half the desired phase difference are combined, the two structural plates having the same structural dimensions can be used, which is advantageous in terms of manufacturing cost.

  In the structural birefringent wave plate, the shape of the triangular birefringence plate is substantially triangular. In addition to the fact that the columnar portion and groove portion are triangular, the tip of the triangular columnar portion and the bottom portion of the triangular groove portion are rounded. It means you may be tinged.

  According to the structural birefringent wave plate of the present invention, it has a high 0th-order light transmittance and can improve the stability of the 0th-order light transmittance against a structural height error due to processing.

The best mode for carrying out the present invention will be described below with reference to the drawings.
1 to 3 are side cross-sectional views of the main parts of the structural birefringent wave plates 1 to 3 according to the present embodiment.

  The structural birefringent wave plate 1 shown in FIG. 1 is periodically formed with a concavo-convex shape composed of a trapezoidal columnar portion 6 having a flat portion 13 at the tip and a triangular groove portion 6 ′ having a bottom portion 14. The structure has an irregular periodic structure having a structural period P and a structural height H. The trapezoidal columnar portion 6 has side portions 11 and 12 whose widths are gradually narrowed toward the flat portion 13 at the tip, and the lengths are substantially equal. The bottom 14 of the groove 6 'has a sharp shape.

  The structural birefringent wave plate 2 of FIG. 2 is formed periodically with a concavo-convex shape comprising a triangular columnar portion 7 having a tip 15 and a trapezoidal groove portion 7 ′ having a flat portion 16 at the bottom. The structure has an irregular periodic structure having a structural period P and a structural height H. The triangular columnar portion 7 has a width that gradually decreases toward the tip 15, has side portions 11 and 12 that are substantially equal in length, and has a pointed tip 15.

  The structural birefringent wave plate 3 in FIG. 3 has a periodic uneven shape composed of a trapezoidal columnar portion 8 having a flat portion 13 at the tip and a groove portion 8 ′ recessed in a trapezoidal shape having a flat portion 16 at the bottom. Are provided with an uneven periodic structure having a structure period P and a structure height H. The trapezoidal columnar portion 8 has side portions 11 and 12 whose width is gradually narrowed toward the flat portion 13 and whose lengths are substantially equal.

  The lattice structure of the conventional structural birefringent wave plate has a rectangular shape as shown in FIG. 4, where the structure period P, the column width L, and the structure height H are shown in FIG. By making the trapezoidal shape as shown in FIG. 3, light reflection can be reduced, and a higher transmittance than that of the conventional rectangular shape can be obtained.

  Further, in the structural birefringent wave plate 1 having the structural period P (μm), the structural height H (μm), and the width L1 (μm) of the flat portion 13 of the columnar portion in FIG. 1, the wavelength used is λ (μm). When the refractive index of the material of each structural birefringent wave plate 1 at the used wavelength λ is n, the average 0th order light transmittance of 98% or more is satisfied by satisfying the above formulas (1) and (2). Further, by satisfying the above expressions (3) and (4), an average 0th-order light transmittance of 99% or more can be realized.

  Further, in the structural birefringent wave plate 2 having the structural period P (μm), the structural height H (μm), and the width L2 (μm) of the flat portion 16 of the groove in FIG. 2, the wavelength used is λ (μm). When the refractive index of the material of the structural birefringent wave plate 2 at the operating wavelength λ is n, the average 0th order light transmittance of 98% or more is realized by satisfying the above formulas (5) and (6). Further, by satisfying the above formulas (7) and (8), an average zero-order light transmittance of 99% or more can be realized.

  Furthermore, the structural birefringence shown in FIG. 3 is the structural period P (μm), the structural height H (μm), the width L1 (μm) of the flat part 13 of the columnar part, and the width L2 (μm) of the flat part 16 of the groove part. In the wave plate 3, when the use wavelength is λ (μm) and the refractive index of the material of the structural birefringence wave plate 3 at the use wavelength λ is n, the above formulas (1), (2), (5), By satisfying (6), an average 0th-order light transmittance of 98% or more can be realized, and by satisfying the above formulas (3), (4), (7), and (8), 99% The above average 0th order light transmittance can be realized.

  FIG. 5 shows the relationship between H / λ and average zero-order light transmittance when λ / P is changed in the structural birefringent wave plate of FIG. FIG. 21 shows the relationship between H / λ and the average zero-order light transmittance when λ / P is changed in the structural birefringent wave plate of FIG. As can be seen from the graphs of FIGS. 5 and 21, the behavior of the average 0th-order light transmittance differs depending on the refractive index n of λ / P, particularly when H / λ is small. From FIG. 5 and FIGS. 6 to 8 to be described later, it is understood that the above formulas (1) to (4) are established, and from FIGS. 21 and 10 to 12 to be described later, the above formulas (5) to (8) are established. I understand that The refractive index n was set to 1.5062662 (λ: 435.8 nm), 1.489400 (λ: 650 nm), and 1.486174 (λ: 780 nm).

  Each of the structural birefringent wave plates 1 to 3 in FIGS. 1 to 3 is effective as a broadband wave plate because it has an effect of improving the transmittance with respect to any wavelength of 435.8 nm, 650 nm, and 780 nm. .

  Also, by making the concave-convex periodic structure into a trapezoidal shape, when manufacturing this structural birefringent wave plate by imprint molding using a molding die produced by dry etching, for example, the column width is gradually reduced. The releasability during imprint molding is improved, which is preferable.

EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples. PMMA resin is used as the material of the structural birefringent wave plate of the present embodiment, and the refractive index is as follows.
n = 1.502662 (λ: 435.8 nm)
n = 1.490400 (λ: 650 nm)
n = 1.486174 (λ: 780 nm)

  <Examples 1, 2, and 3 (FIG. 1)>

  Example 1 has a trapezoidal lattice structure similar to that of FIG. 1, the structural period P is 300 nm, and the width of the flat portion of the columnar portion (also referred to as “column tip width”, hereinafter the same) L1 is 105 nm (L1 / FIG. 6 shows the relationship between the structural height H (μm), the TE 0th order light transmittance, the TM0th order light transmittance, and the phase difference when the wavelength λ is 435.8 nm.

  Example 2 is the same conditions as Example 1 except that the width L1 of the flat part of the columnar part is 165 nm (L1 / P = 0.55). The structure height H (μm) and the TE0 order light FIG. 7 shows the relationship between the transmittance, the TM0-order light transmittance, and the phase difference.

  Example 3 is the same conditions as Example 1 except that the width L1 of the flat part of the columnar part is 250 nm (L1 / P = 0.833). The structure height H (μm) and the TE0 order light FIG. 8 shows the relationship between the transmittance, the TM0-order light transmittance, and the phase difference.

  Comparative Example 1 is the conventional rectangular lattice structure of FIG. 4, where the structural height H is 300 nm, the structural period P is 300 nm, the L / P (filling factor) is 0.4, and the wavelength λ is 435.8 nm. FIG. 9 shows the relationship between (μm), TE0th order light transmittance, TM0th order light transmittance, and phase difference.

  As can be seen from FIGS. 6, 7, 8, and 9, in the first, second, and third embodiments, the 0th-order light transmittance is higher than that of the conventional rectangular shape of FIG. 4 by adopting the trapezoidal shape of FIG. 1. Obtainable. Moreover, if the trapezoid degree prescribed | regulated by L1 / P of FIG. 1 is 0.55 or less, an average 0th-order light transmittance will be about 98% or more, and if it is 0.35 or less, an average 0th-order light transmittance will be. It can be seen that becomes 99% or more.

  <Examples 4, 5, and 6 (FIG. 2)>

  Example 4 has a trapezoidal lattice structure similar to that shown in FIG. 2. The structural period P is 300 nm, the width of the flat portion of the groove (also referred to as “groove bottom width”, the same applies hereinafter), and L2 is 30 nm (L2 / P). = 0.1) When the wavelength λ is 435.8 nm, FIG. 10 shows the relationship between the structural height H (μm), the TE 0th-order light transmittance, the TM0th-order light transmittance, and the phase difference.

  Example 5 is the same conditions as Example 4 except that the width L2 of the flat portion of the groove is 60 nm (L2 / P = 0.2). The structure height H (μm) and the TE0 order light transmission FIG. 11 shows the relationship between the transmittance, TM0th-order light transmittance, and phase difference.

  Example 6 is the same conditions as Example 4 except that the width L2 of the flat portion of the groove is 90 nm (L2 / P = 0.3). The structure height H (μm) and the TE0 order light transmission are the same. FIG. 12 shows the relationship between the transmittance, TM0th-order light transmittance, and phase difference.

  As can be seen from FIG. 10, FIG. 11, FIG. 12, and FIG. 9, in the fourth, fifth, and sixth embodiments, the 0th-order light transmittance is higher than the conventional rectangular shape of FIG. Obtainable. Further, if the trapezoidal degree defined by L2 / P in FIG. 2 is 0.2 or less, the average 0th-order light transmittance is approximately 98% or more, and if it is 0.1 or less, the average 0th-order light transmittance is It can be seen that becomes 99% or more.

  <Examples 7 and 8 (λ: 435.8 nm)>

  Example 7 has a trapezoidal lattice structure similar to that of FIG. 1, the structural period P is 300 nm, the width L1 of the flat part of the columnar part is 60 nm (L1 / P = 0.2), and the wavelength λ is 435.8 nm. FIG. 13 shows the relationship between the structural height H (μm), the TE0th order light transmittance, the TM0th order light transmittance, and the phase difference.

  Example 8 has a trapezoidal lattice structure similar to that shown in FIG. 3, the structural period P is 300 nm, the flat part width L1 of the columnar part is 60 nm (L1 / P = 0.2), and the flat part width L2 of the groove part. Is the relationship between the structural height H (μm), TE0th order light transmittance, TM0th order light transmittance and phase difference when the wavelength is 60 nm (L2 / P = 0.2) and the wavelength λ is 435.8 nm. 14 shows.

  <Examples 9 and 10 (λ: 650 nm)>

  Example 9 has a trapezoidal lattice structure similar to that shown in FIG. 1. When the structural period P is 300 nm, the width L1 of the flat part of the columnar part is 60 nm (L1 / P = 0.2), and the wavelength λ is 650 nm. FIG. 15 shows the relationship between the structural height H (μm), the TE0th order light transmittance, the TM0th order light transmittance, and the phase difference.

  Example 10 has a trapezoidal lattice structure similar to that in FIG. 3, the structural period P is 300 nm, the flat part width L1 of the columnar part is 60 nm (L1 / P = 0.2), and the flat part width L2 of the groove part. 16 represents the relationship between the structural height H (μm), the TE0th order light transmittance, the TM0th order light transmittance, and the phase difference when the wavelength λ is set to 60 nm (L2 / P = 0.2) and the wavelength λ is 650 nm. Show.

  Comparative Example 2 is the conventional rectangular lattice structure of FIG. 4, where the structural height H (μm) when the structural period P is 300 nm, L / P (filling factor) is 0.4, and the wavelength λ is 650 nm. ), The TE0th order light transmittance, the TM0th order light transmittance, and the phase difference are shown in FIG.

  <Examples 11 and 12 (λ: 780 nm)>

  Example 11 has a trapezoidal lattice structure similar to that shown in FIG. 1. When the structural period P is 300 nm, the width L1 of the flat part of the columnar part is 60 nm (L1 / P = 0.2), and the wavelength λ is 780 nm. FIG. 18 shows the relationship between the structural height H (μm), the TE0th order light transmittance, the TM0th order light transmittance, and the phase difference.

  Example 12 has a trapezoidal lattice structure similar to that shown in FIG. 3, the structural period P is 300 nm, the flat portion width L1 of the columnar portion is 60 nm (L1 / P = 0.2), and the flat portion width L2 of the groove portion. 19 represents the relationship between the structural height H (μm), the TE0th order light transmittance, the TM0th order light transmittance, and the phase difference when the wavelength λ is 60 nm (L2 / P = 0.2) and the wavelength λ is 780 nm. Show.

  Comparative Example 3 is the conventional rectangular lattice structure of FIG. 4, where the structural height H (μm) when the structural period P is 300 nm, L / P (filling factor) is 0.4, and the wavelength λ is 780 nm. ), The TE0th order light transmittance, the TM0th order light transmittance, and the phase difference are shown in FIG.

  As can be seen from the above Examples 7 and 8, Comparative Example 1, Examples 9 and 10, Comparative Example 2, Examples 11 and 12, and Comparative Example 3, Examples 7 to 12 are as shown in FIG. By adopting the trapezoidal shape, it is possible to obtain higher zero-order light transmittance than the conventional rectangular shape of FIG. 4 at each wavelength of 435.8 nm, 650 nm, and 780 nm.

  In addition, as in Comparative Examples 1 to 3, the conventional rectangular lattice structure of FIG. 4 has a 0th-order light transmittance that periodically varies considerably with changes in the structure height, whereas Examples 1 to 12 In the trapezoidal grating structure of FIG. 5, it can be seen that a periodic plate with a high structural error of the 0th-order light transmittance is considerably small, so that it is possible to realize a wavelength plate that is resistant to structural height errors due to processing.

  Furthermore, when two structural birefringent wave plates are used in a configuration, in order to obtain a desired phase difference, it is necessary to select a structural dimension that can achieve the desired phase difference and obtain a high transmittance in order to obtain the desired phase difference. However, in the case of the wave plates of Examples 1 to 12, since a high transmittance can be obtained at almost any structural height, the structural dimensions can be selected only by a combination of phase differences. In particular, if two wave plates capable of obtaining a phase difference that is half of the desired phase difference are combined, both can be used with the same structural dimensions, which is advantageous in terms of manufacturing cost.

  As described above, the best mode for carrying out the present invention has been described. However, the present invention is not limited to these, and various modifications are possible within the scope of the technical idea of the present invention. For example, in FIGS. 1 to 3, one side surface portion 11 or 12 may be configured to be longer than the other side surface portion 12 or 11, and the same effect can be obtained.

It is principal part side sectional drawing of the structural birefringence wavelength plate 1 by this Embodiment. It is principal part side sectional drawing of the structural birefringent wavelength plate 2 of another structure by this Embodiment. It is principal part side sectional drawing of the structural birefringent wavelength plate 3 of another structure by this Embodiment. It is principal part side sectional drawing of the conventional structural birefringent wavelength plate. 2 is a graph showing the relationship between H / λ and average zero-order light transmittance when λ / P is changed in the structural birefringent wave plate of FIG. 1. It is a graph which shows the relationship between structural height H (micrometer) in Example 1, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in Example 2, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in Example 3, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between the structural height H (micrometer) in the comparative example 1, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in Example 4, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in Example 5, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in Example 6, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in Example 7, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in Example 8, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in Example 9, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in Example 10, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in the comparative example 2, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in Example 11, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structural height H (micrometer) in Example 12, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. It is a graph which shows the relationship between structure height H (micrometer) in Comparative Example 3, TE0th-order light transmittance, TM0th-order light transmittance, and a phase difference. 3 is a graph showing the relationship between H / λ and average zero-order light transmittance when λ / P is changed in the structural birefringent wave plate of FIG. 2.

Explanation of symbols

1, 2, 3 Structural birefringent wave plate 6 Columnar portion 6 'Groove portion 7 Columnar portion 7' Groove portion 8 Columnar portion 8 'Groove portion 11, 12 Side surface portion 13 Columnar portion flat portion 14 Bottom portion 15 Tip 16 Groove portion flat portion H Structure height P Structure period L1 Width of flat portion 13 L2 Width of flat portion 16

Claims (10)

It has a concavo-convex periodic structure in which the columnar part and the groove part are periodically repeated,
The structural birefringent wavelength plate, wherein at least one of the tip of the columnar part and the bottom of the groove part is formed in a trapezoidal shape having a flat part.   2. The structural birefringent wave plate according to claim 1, wherein a tip of the columnar part has a flat part, and the groove part is substantially triangular so that the groove part gradually narrows from the flat part toward the bottom part.   The structural birefringent wave plate according to claim 1, wherein the bottom of the groove has a flat portion, and the columnar portion has a substantially triangular shape so as to gradually narrow from the flat portion toward the tip.   The structural birefringent wave plate according to claim 1, wherein the tip of the columnar part and the bottom of the groove part each have a flat part. 5. Any one of claims 1 to 4 satisfying the following expressions (1) and (2), where P is a structural period of the uneven periodic structure, H is a structural height, and L <b> 1 is a width of a flat part of the columnar part. 2. The structural birefringent wave plate according to item 1.
When P ≦ λ / n, 0.16 ≦ H / λ and 0 <L1 / P ≦ 0.55 (1)
When P> λ / n, 0.85 ≦ H / λ and 0 <L1 / P ≦ 0.55 (2)
However, P <λ
λ: wavelength used n: refractive index of wave plate material at wavelength λ used The following formulas (3) and (4) are satisfied, where P is the structural period of the irregular periodic structure, H is the structural height, and L1 is the width of the flat portion of the columnar portion. 2. The structural birefringent wave plate according to item 1.
When P ≦ λ / n, 0.22 ≦ H / λ ≦ 3.7 and 0 <L1 / P ≦ 0.35 (3)
When P> λ / n, 1.15 ≦ H / λ ≦ 3.7 and 0 <L1 / P ≦ 0.35 (4)
However, P <λ
λ: wavelength used n: refractive index of wave plate material at wavelength λ used The structure according to any one of claims 1 to 6, wherein when the structure period of the concave-convex periodic structure is P, the structure height is H, and the width of the flat portion of the groove is L2, the following expressions (5) and (6) are satisfied. The structural birefringent wave plate according to Item.
When P ≦ λ / n, 0.17 ≦ H / λ and 0 <L2 / P ≦ 0.2 (5)
When P> λ / n, 1.00 ≦ H / λ and 0 <L2 / P ≦ 0.2 (6)
However, P <λ
L1 + L2 <P
λ: wavelength used n: refractive index of wave plate material at wavelength λ used The following formula (7) or (8) is satisfied, where P is the structural period of the irregular periodic structure, H is the structural height, and L2 is the width of the flat portion of the groove. The structural birefringent wave plate according to Item.
When P ≦ λ / n, 0.23 ≦ H / λ ≦ 3.7 and 0 <L2 / P ≦ 0.1 (7)
When P> λ / n, 1.28 ≦ H / λ ≦ 3.7 and 0 <L2 / P ≦ 0.1 (8)
However, P <λ
L1 + L2 <P
λ: wavelength used n: refractive index of wave plate material at wavelength λ used   The structural birefringent wave plate according to claim 1, wherein the concave-convex periodic structure is formed by imprinting on a resin using a molding die. A waveplate combination structure comprising a combination of a plurality of structural birefringent waveplates according to any one of claims 1 to 9.

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