JPS6011802A - Transmission surface relief grating - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a holographic ink grating in a Holographic 11 scanner, and more particularly to a transmission type surface relief diffraction grating.

[Recitation] U1 right There has not yet been a sufficient theoretical analysis of the diffraction efficiency of conventional transmission type surface relief diffraction gratings, and the diffraction efficiency that has been experimentally achieved is less than 30%. The value of 34% is known to be theoretically predicted, but this theory assumes that the surface relief diffraction grating is a plane grating and applies the theory of plane gratings, so it has sufficient basis. It's not a thing.

Furthermore, the polarization direction of the light incident on the diffraction grating and the shape of the grating are
There is a problem that higher diffraction efficiency (approximately 60% or more) cannot be obtained.

1. The present invention has been made to solve the above problems, and an object of the present invention is to provide a transmission type surface relief diffraction grating having a diffraction efficiency of 60% or more.

The configuration of the present invention will be described below based on specific examples.

FIG. 1 is a sectional view of a transmission type surface relief diffraction grating to which the present invention is applied.

1 is transparent deck glass, and 2 is transparent resin.

In No. 1191, a transparent resin 2 whose thickness changes periodically is formed on a transparent glass 10 and acts as a diffraction grating.

Such gratings are generally used for transmission surface relief diffraction 1
It is called 8-r-. In the present invention, a lattice in which the lattice-r shape is approximately bilaterally symmetrical will be explained.

Figure 2 shows the state of diffraction in the diffraction grating of the present invention. l-diagram. Here, d is the grating spacing, the depth of the grating, 0 is the incident angle, λ is the wavelength, ψ0 is the diffraction angle of the 0th-order light, and ψf is the diffraction angle of the 1st-order diffracted light.

21st” (Incoming n・I light amount P entering from the direction at I
1) 16 is diffracted (diffracted in the direction of C by the octad).

This diffracted light is called transmitted first-order diffracted light, and the amount of light is expressed as Pl.

The diffraction equation in this case is ψm
If the order of diffraction is m, then sinO=mλ/d+nosinψn1.

In FIGS. 3 to 6, the grid shape is sinusoidal and ll0=1.
It represents the diffraction efficiency of the first-order diffracted light transmitted through the 66 gratings. Fig. 3 shows the grating depth ratio i+/d=0.5, Fig. 6 shows h/
This is the case when d=2.0.

The solid lines in the figure represent the incidence of linearly polarized light (referred to as '1'E polarized light) parallel to the grating grooves, and the broken lines represent the incidence of linearly polarized light (referred to as TM polarized light) perpendicular to the grating grooves.

The incident angle is an angle (Bragg incident angle) that satisfies 0=sin-'(λ/2d). Figure 7 shows λ/d21.414/
0=/15° grating L: When TIE polarized light is input, the diffraction efficiency of the transmitted first-order diffracted light is shown when the grating depth ratio h/d changes. The refraction u no of the grating medium is set to 1.50.1-66.2.00 (solid line no =
1.66° broken line no ” 1-50 + dotted line no = 2
．． 00).

Now, from Figures 3 to 7, the transmission first-order diffraction effect is 60%.
The above conditions are l) Linearly polarized light parallel to the grating grooves: 0.5≦λ/d<2.0 1.0< h/d <2.75: 1) Linearly polarized light perpendicular to the grating grooves If 0.5≦λ/d
<1.4 1.0≦b/d≦2.5.

Figure 8 shows λ/8 and h/, which give a diffraction efficiency of 60% or more.
Indicates the range of d.

FIG. 9 is a diagram showing an optical system for producing the transmission type surface relief diffraction grating of the present invention. In the figure, 5 is a laser light source, 6 is a convex lens, 7 is a condensing lens, 8 is a pinball, 9 is a convex lens, 10 is a distribution correction vapor deposition filter, r filter, 11 is a beam splitter, and 12 and 13 are reflecting mirrors.

In FIG. 9, the amount of light from the laser light source 5 is converted into parallel light by a lens 6, and the objective lens 7 converts it into a focused beam through a pinhole 8.
lead to. The solo light that passes through the pinhole 8 becomes divergent light and becomes parallel light by the lens 9.

Here, the parallel light has a Gaussian intensity distribution due to the ruttering effect of the pinhole 8.

The evaporation correction filter IO has a transmission skewer with an inverse Gaussian distribution, and when parallel light with a Gaussian intensity distribution passes through it, it becomes parallel light with a uniform distribution. After passing through the parallel light filter, the parallel light is split into two lights by the beam splitter 11.
One is the reflecting mirror 12, which irradiates the photoresist 2 coated with (electric power (reflected by the main mirror 13, both beams of light onto the glass plate) so as to overlap with each other).

Therefore, on the photoresist 2, two light beams (± interference occur,
Light and dark stripes are formed, and the photoresist 2It is exposed to light according to the light and dark stripes. When a positive type photoresist is used as a photoresist, if it is developed after being irradiated with light,
The exposed part was removed 4L.

A sinusoidal groove as shown in FIG. 1 is formed. In this case, AZ1350 (manufactured by Cable Co., Ltd.) is used as a photoresist, and a He-Cd laser beam (λ"4) is used as a light source 5.
41.6 nm) and 80 mW. Exposure i, 60m
, J/c++Y.

With a development time of 1 minute, a grating with a grating depth l+==o of 7 μm and an interstitial space 's%d=0.45 μm was obtained. He-
When the grating was irradiated with an Nc laser at an incident angle θ=45°, it was possible to achieve a diffraction efficiency of 90% for the transmitted first-order diffracted light.

According to the transmission type surface relief diffraction t8 element of the present invention, an extremely high diffraction efficiency of 60% or more can be obtained.

-F In the explanation, the grating shape is sinusoidal, but the grating shape is not limited to a sinusoidal shape, and various grating waveforms can be adopted as long as the shape is approximately bilaterally symmetrical. It should be noted that the present invention is not limited to the specific embodiments listed in 1. It goes without saying that various modifications can be made within the technical scope of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a holographic diffraction grating to which the present invention is applied, FIG. 2 is a diagram showing the diffraction of the present invention, and FIGS. 3 to 7 show that the grating shape is a sine wave and no==1 FIG. 3 is a diagram showing the diffraction efficiency of transmitted first-order diffracted light of a .66 grating. Here, 5 Figure 3 is the grating depth ratio, /(1-0, 5 + Figure 4 is
h'/d=1.0. Figure 5 shows h/d = 1.51
FIG. 6 shows h/d=2.0. In Figure 7, λ/d=1.414
This is a case of 0-45°. Figure 8 shows that the diffraction efficiency is 60
It is a figure which shows the range of (lambda)/8 and h/d which become % or more. FIG. 9 is a diagram showing an optical system for creating a transmission type surface relief diffraction grating of the present invention. 1. Transparent flat glass 2, translucent resin 3, transmission type surface relief diffraction grating 4, sinusoidal diffraction grating 5, laser light source 6, convex lens 7, condensing lens 8, pinhole 9, convex lens 10, distribution correction vapor deposition filter 11, Beam splitter - 12, 13 Reflector Patent applicant Ricoh Co., Ltd. - ■A shaku ■Jiku ~ /73C ~

Claims (1)

[Claims] The wavelength of the incident light that enters the diffraction grating is λ. The depth of the diffraction grating is h, the grating interval is d, and when the incident light is linearly polarized light parallel to the grating grooves, 0.5≦λ
/ d < 2.0 1.0 < h / d < 2.75 If the incident light is linearly polarized light perpendicular to the grating groove, 0.5≦λ
A transmission type surface relief diffraction grating characterized by satisfying the following conditions: / d < 1.4 1.0 < h / d < 2.5 and having a substantially bilaterally symmetrical grating shape.