JPS6326604A - Polarization beam splitter - Google Patents

Abstract

PURPOSE:To eliminate the need for a prism which requires vapor deposition or sticking by charging a material whose refractive index is nearly equal to the ordinary or extraordinary light refractive index of a birefringent medium in at least recessed parts of the formed surface projection and recess grating of the birefringent medium. CONSTITUTION:When calcite 1 is used as the birefringent medium, the photoresist pattern of the grating is formed on the surface of the calcite 1 by photolithography and the surface projection and recess grating is formed by ion etching. Then, acrylic resin 2 which has the refractive index N=1.49 almost equal to the extraordinary light refractive index Ne=1.485 is applied as the filling material in grating grooves and the surface is flattened. When a polarization beam splitter is irradiated with incident light 3, a phase grating with a 0.005 refractive index difference to extraordinary light is obtained, so almost no diffracted light is generated and nearly all of extraordinary light components become 0th-order light 4. The refractive index difference to ordinary light, on the other hand, becomes No-N=1.6544-1.49=0.1644, so this grating operates as the phase grating, so that ordinary light components generate refracted light 5. The diffraction efficiency, however, is not 100%, so the ordinary light components generate 0th-order light 4 as well.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polarizing beam splitter, which is used in particular for optical pickup for video discs, digital audio discs (compact discs), and optical discs, and as an analyzer for optical isolators. This type of polarized beam splitter is concerned.

(Prior Art) Conventional pick-up tubes for video disks, digital audio disks, and optical disks use a polarizing beam splitter in which two right-angle prisms are bonded together and the bonded surfaces are coated with a dielectric multilayer film. or,
An analyzer made of calcite is used as an analyzer for the optical isolator. Examples of use in optical disk optical systems can be found, for example, in the following documents.

Kanmoto, Ojima, and Tateno, “Optics” magazine, Vol. 11, No. 6, No. 62
The paper published on pages 9 to 633, "Characteristics of semiconductor lasers in optical disk optical systems" (Problems to be solved by the invention) The above-mentioned conventional technology does not require the steps of 1i) T-polishing, multilayer film deposition, and bonding. Therefore, there were problems in that it was difficult to mass produce and was expensive. Another problem is that it is difficult to make it thinner because it uses the same amount as a prism.

(Means for Solving the Problems) The polarizing beam sparitor of the present invention has at least the concave portions of the surface unevenness grating formed by the birefringent medium that is approximately equal to the ordinary refractive index or the extraordinary refractive index of the birefringent medium. It is filled with a material with a -1 refractive index.

(Function) If the concave portions of a surface uneven grating formed on a birefringent medium are filled with, for example, a substance with a refractive index approximately equal to the refractive index of the ordinary light, this grating will match the refractive index for ordinary light and will no longer function as a grating. First, it simply becomes a medium whose refractive index is the ordinary refractive index. On the other hand, for extraordinary light, it acts as a phase grating consisting of the refractive index of the extraordinary light and the refractive index of the filling material, diffracts the extraordinary light, and effectively changes the optical path. The above is the principle of operation of the present invention. In this way, since the present configuration uses the diffraction phenomenon, the thin grating near the surface of the element has a beam splitter function, thereby realizing a thin element without using a prism. Also, for the filling material,
As described in later examples, by using resin, vapor deposition,
After all, it can be manufactured by a simple process such as Subinko 1-, regardless of alignment, and mass productivity and cost can be improved.

(Embodiment) FIG. 1 is a perspective sectional view showing the basic configuration of an embodiment of the present invention. In this example, Calcite 1 was used as the birefringent medium. A lattice photoresist 1-pattern was formed on the surface of Calci I-1 by photolithography, and using this as a mask, a surface uneven lattice was first formed by I6 ion etching.

Next, acrylic resin 2 having a refractive index N=1.49, which is approximately equal to the extraordinary light refractive index Ne-1,485, was applied as a filling material to the grating grooves to flatten the surface. When the completed leakage beam splitter is irradiated with incident light 3, it becomes a phase grating with a refractive index difference of 0.005 for extraordinary light, so almost no diffracted light is generated, and most of the extraordinary light components are It is generated as zero-order light 4. - For lightning, the refractive index difference is No-N=1.6544-1.49=0.1644, so it acts as a phase grating, and the ordinary light component produces diffracted light 5. However, since the diffraction efficiency is not 100%, zero-order light 4 is also generated as the ordinary light component. In order to increase the diffraction efficiency, the vortex depth must be increased so that the grating acts as a Brass-Soget diffraction grating, and the Bragg arrangement must be arranged so that the grating has a mirror surface relationship with the incident light and diffracted waves. It goes without saying that it can be used as

In this embodiment, as shown in FIG. 1, the convex portions of the birefringent medium were also covered with acrylic resin, but the essence remains the same even if only the concave portions are filled with resin instead of such a structure. Furthermore, the same effect can be obtained by filling only the recesses with resin and then covering the entire surface with a birefringent medium.

(Effects of the Invention) The present invention eliminates the need for prisms that require expensive vapor deposition and gluing as in the past. Furthermore, since the ordinary beam splitter of the present invention can be constructed in the form of a thin plate, it has the effect of being thinner and lighter than a prism.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a perspective sectional view of an embodiment of the present invention. 1... Birefringent medium 2... Filling material 3... Incident light 4... 0th order diffracted light -゛-...,. 5...1st order diffracted light ■Knee Z-
Agent: Susumu Uchiatsu, Patent Attorney - Figure 1: Birefringent medium

Claims (1)

[Claims] A polarizing beam splitter, characterized in that at least the concave portions of a surface uneven grating formed on a birefringent medium are filled with a material having a refractive index substantially equal to the ordinary or extraordinary refractive index of the birefringent medium.