JPS61203402A - Functional optical element - Google Patents

Abstract

PURPOSE:To function effectively the title element for light having optional polarization characteristics by forming a grating of the boundary face between an optically isotropic material and optically anisotropic material and exerting simultaneously a diffraction effect to the polarization components intersecting orthogonal with each other of incident light. CONSTITUTION:The functional optical element forms the triangular wave-like grating consisting of the optically anisotropic material 1 and the optically isotropic material 2. The element is so formed as to satisfy simultaneously equations I and II when the wavelength of the incident light is designated as lambda0, the individual refractive indices which the polariation components 4, 4' intersecting orthogonally with each other of the incident light sense with the material 1 are designated as n1, n2, the refractive index of the above-mentioned isotropic material is designated as ng and the thickness of the above-mentioned grating as T. More specifically, the polarization component 4 is parallel in the direction thereof with the axial direction of the material and senses the refractive index n1. The polarization component 4' has the direction intersecting orthogonally with the axial direction of the material 1 and senses the refractive index n2 and therefore the equations I, II are satisfied in the case when the incident light 3 is made to incident to this element, by which the emission of the zero order transmitted and diffracted light is obviated and the incident light 3 is fully made into the diffracted light 5, 5' of + or -1 order.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field The present invention relates to a functional optical element suitable as a device for various apparatuses such as optical recording, optical coupling, optical communication, and optical calculation.

For example, it is used as a single spectrometer, a demultiplexer/combiner, or a reflector. Recently, in applications in semiconductor lasers and optical integrated circuits, irregularities are formed on the surface as a means of imparting a phase change, and the medium used therefor is usually composed of an optically isotropic material. Increasingly, the use of anisotropic substances such as crystals that polarize the light is increasing, and unless a laser or other light source is used as a light source and linearly polarized light is used, the It was necessary to polarize the light, and the efficiency of light use was greatly reduced at this stage.

(3) Summary of the invention The purpose of the present invention is to provide a functional optical element that eliminates the drawbacks of the conventional technology and functions effectively even for light having arbitrary polarization characteristics despite using an optically anisotropic material. It's about doing.

In order to achieve the above object, the functional optical element according to the present invention forms a grating at the interface of an optically isotropic material and an optically anisotropic material, so that incident light having arbitrary polarization characteristics can be The above-mentioned arbitrary It is characterized in that the grating diffracts incident light having polarization characteristics.

The relationship between the refractive indices n1, n2, and ng differs depending on the shape of the grating and also depends on the function given to the functional optical element.If the grating thickness is T and the wavelength of the incident light is 0, then lnz-ng|・・Tamt containing 0 (ml=1,2,
3. -----)ln2-ng｜・*T=m2entero (
m2=1.2,3. -----) The first substance is, for example, glass.

SiO2, MgO, KCI, NaCl, KBr.

Srτi 03, PMMA (polymethyl e-methacrylate), polystyrene, polycarbonate, PV
K (polyvinyl◆carbazole), epoxy resin, photoresist, etc. are suitable.

Further, the second substance is, for example, liquid crystal, PLZT, B
aTiO3, LiTaO2, Gd2 (M.

04) 3, B i 4T3012, B 11
2s t Ozo.

5bSI, PbTiO3, NaNO2, Ba2Na
N b s Ozs , Cu Cl , Ti
Examples include O2, MgF2, and the like.

The shape of the grating can be rectangular, triangular, sinusoidal, etc., and as mentioned above, it is determined by the function provided to the device, ease of production, and conditions related to specifications. .

This functional optical element can be used as a transmissive type and a reflective type when using two polarization elements that are perpendicular to each other to polarize light with arbitrary polarization characteristics, that is, light with random polarization components emitted from a normal light source. In the case of a transmission type, it is necessary to make the constituent members transparent to the light used, and in the case of a one-reflection type, it is necessary to use a reflective material or provide a reflective film for a predetermined member.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

(4) Example Figures 1 (A) to (C) are examples of the basic configuration of this functional optical element, where l is an optically anisotropic material, 2 is an optically isotropic material,
T indicates the grating thickness.

In the element shown in FIG. 1A, an optically anisotropic material 1 and an optically isotropic material 2 form a rectangular grating. Input the wavelength of incident light having arbitrary polarization characteristics as 0, and let the individual refractive indexes felt by the two mutually orthogonal polarization components of the incident light with respect to the optically anisotropic material 1 be n1, n2, and optically isotropic. In one element, when the refractive index of the magnetic substance 2 is ng.

lrD-ng l *”r= (”+sentence 1) Enter Q (
Jlt=0.1.2.3----)I n2-ngI
・Ta (”+12) Input Q (fL2=o, 1.2.
3----) are satisfied.

In the element shown in FIG. 1(B), a triangular wave grating is formed by an optically anisotropic material 1 and an optically isotropic material 2.

|n1-ng|...1 with THml (ml=1.2
．． -----)In2-ng｜・・T≧m2λ2
(m2=1, 2.---) is satisfied. Further, in the element shown in FIG. 1(C), a sinusoidal grating is formed by an optically anisotropic material 1 and an optically isotropic material 2.

1 0.050661 1nl-n, gl*T=in o (1 at kl-4+-41
-=Go (k1=1, 2, 3, ---1) 1 0.050661 1 n2 1g l'' T=Enter 0 (k2 4'' -
41ζ1-=1-(k2= 1 , 2 , 3,----
) are satisfied.

When light with arbitrary polarization characteristics is incident on the elements shown in FIGS. 2 is an optically anisotropic material, 2 is an optically isotropic material with a refractive index of ng, 3 is an incident light having arbitrary polarization characteristics, 4.4' is an incident light 3 mutually, and ■ marks are materials 1 and 3. The groove direction of the grating formed by 2 (perpendicular to the paper surface).

The ← mark indicates the direction in which the gratings are arranged (left and right direction in the paper).

The functional optical elements used in this principle explanatory diagram are shown in Figure 1 (A
) is an element having a rectangular grating as shown in FIG.

However, the optical axis direction of the optically anisotropic material 1 is directed toward the grating groove direction. The optical axis direction may be any direction as long as it does not actually face the traveling direction of the incident light.

When the incident light 3 is incident on this element, the direction of the polarized light component 4 is parallel to the optical axis direction of the optically anisotropic material 1 among the two mutually orthogonal polarized components of the incident light 3, and therefore, Feel the extraordinary refractive index ne of the optically anisotropic material 1. Further, the polarized light component 4' has a direction perpendicular to the optical axis direction of the optically anisotropic material 1, and senses the ordinary refractive index no of the optically anisotropic material 1. Therefore, polarization components 4 and 4' have refractive indices ne and ng, respectively.
, no and ng.

It can be expressed by equation (1).

First, the condition for only the high-order beam 5.5' to be emitted is Δn.
T=(++Jl)λO(1=0.1,2,3.----
)-1--(2). Therefore, polarization components 4 and 4'
Ins−ng｜・=(++ix) enter o
(il=o, 1, 2.----) lne-ng |・=
(4+L2) entering o (1t=0.1,2.----
) is satisfied, η0=Q, and no zero-order transmitted diffracted light is emitted.

An example of fabrication of the functional optical element shown in FIG. 2 and the results of performance evaluation will be described below.

CaCO3 crystal along crystal axis 50X50X1 mm
Prepare a transparent substrate that has been sliced into 3 size pieces, polished and cleaned on both sides, and place the RD-200ON on this transparent substrate.
(Negative type resist manufactured by Hitachi, Ltd.) was coated with a spinner, and after pre-baking to a predetermined extent, a grating made of the resist was formed with a pitch of 1.6 g, m and a thickness of 4000 by mask exposure and development. However, the direction of the grating is the crystal axis direction. continue.

The substrate surface was etched to a depth of 5.197 zm by reactive ion etching using a CF4-O2 mixed gas. Thereafter, the resist was removed using a resist remover to produce a transparent substrate having a rectangular grating.

Next, place EPOTECH 3 on the rectangular grating surface.
01-2 (a two-component epoxy resin manufactured by Epotec) was applied by spin coating, and after curing treatment at 80° C. for 1.5 hours, a flat surface was formed so as to fill the grating grooves. Incidentally, the ordinary refractive index no of CaCO3 for light with a wavelength of 8300 is 1.64.
The extraordinary refractive index ne is 1.48, which is the refractive index of epoxy resin (
3) It can be expressed by the formula.

The light used to evaluate the performance of the zero-function optical element has a wavelength input Q=
There are 8300 random polarization directions.

When light 3 (input Q = 8300 people) having a random polarization direction is perpendicularly incident on this functional optical element, polarization component 4 whose polarization direction is equal to the groove direction of the rectangular grating is CaC.
O3 crystal ne(-1,64) and epoxy resin 17)
I felt a rectangular grating consisting of ng (=1.56).

The polarization component 4' whose polarization direction is equal to the alignment direction of the rectangular grating is no (=1.48) of the C&CO3 crystal!
You can feel the rectangular grating made of poxy resin (=1.56). At this time, each of the polarization components 4.4' satisfies the above equation (2), and in the above equation (1), η(14
It becomes 0.

The overall light utilization efficiency is over 80%, and the S/N ratio is 100.
: It was 1 or more.

The functions of this functional optical element shown in Figure 2 are just examples of the functions that a single functional optical element has, and various functions can be provided by changing the grating shape, optical axis direction, refractive index of each member, etc. things are possible. It goes without saying that the present invention can also be used in Fresnel lenses, curved gratings, grating couplers, DFB lasers, etc.

(5) As described in detail of the invention, the functional optical element according to the present invention functions effectively with respect to light having arbitrary polarization characteristics, even though it is made of an optically anisotropic material, and It is an optical element with multiple functions.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating an example of the configuration of a functional optical element according to the present invention. l -111 optically anisotropic material 2-111 optically isotropic material 3 - 111 rays of light

Claims (4)

[Claims] (1) A grating is formed at the interface of an optically isotropic material and an optically anisotropic material, and two mutually orthogonal polarization components of incident light having arbitrary polarization characteristics are formed in the optically anisotropic material. By providing a predetermined relationship between the individual refractive indices n_1, n_2 felt for the object and the refractive index n_g of the optically isotropic material, it is possible to cause the incident light having the arbitrary polarization characteristics to be diffracted by the grating. Features functional optical elements. (2) When the grating has a triangular wave shape, its thickness is T, and the wavelength of the incident light is λ_0, |n_1-n_
g|・T≧m_1λ_0 (m_1=1, 2, 3, ---
−) |n_2−n_g|・T≧m_2λ_0(m_2=
1, 2, 3, -----) The functional optical element according to claim 1, wherein the functional optical element satisfies the following conditions simultaneously. (3) When the grating has a rectangular shape, its thickness is T, and the wavelength of the incident light is λ_0, |n_1−n_g
|・T≧[(1/2)+l_1]λ_0(l_1=0,
1, 2, 3----) | n_2-n_g |・T≧[(1
/2)+l_2]λ_0(l_2=0, 1, 2, 3--
--) The functional optical element according to claim 1, characterized in that it simultaneously satisfies the following. (4) When the grating has a sinusoidal shape, its thickness is T, and the wavelength of the incident light is λ_0, |n_1-n_
g|・T≧λ_0(k_1−(1/4)+[0.050
661/(4k_1-1)]-[0.053041/(
4k_1-1)^3]+[0.262051/(4k_
1-1)^5]------) (k_1=1, 2, 3, -
---) |n_2-n_g|・T≧λ_0(k_2-(1/4)
+[0.050661/(4k_2-1)]-0.05
3041/(4k_2-1)^3+(0.262051
/(4k_2-1)^5+----)(k_2=1,
Claim No. 2, 3, -----) is characterized in that the following conditions are simultaneously satisfied:
) Functional optical element described in item 2.