JPH05181013A - Polarized light conversion device - Google Patents

Abstract

PURPOSE:To convert a linearly polarized luminous flux to a substantially circularly polarized luminous flux without using a transmission type quarter- wavelength made of a rock crystal. CONSTITUTION:An Si substrate 51 is coated with SiN and MgF layers 52, 53 having an adequate refractive index and thickness to form a reflection plate. The polarized light of a specific wavelength is made incident on the substrate 51 by utilizing the polarization characteristic in the diagonal incident reflection thereof, by which the reflected light is polarized to the circularly polarized light. The substrate 51 which is the reflection plate is so formed as to have a relation n0>n1>n2 where the refractive index of the Si to the wavelength to be used is designated as n0, the refractive index of the 1st layer 52 as n1 and the refractive index of the 2nd layer 53 as n2.

Description

Detailed Description of the Invention

[0001]

[Industrial application] There are cases where it is desired to convert linearly polarized light into circularly polarized light in various measurements using polarized light. In addition, the laser emission light is polarized, which may be inconvenient in measurement, and it may be desired to make it circularly polarized. The present invention relates to a polarization circular polarization conversion device used in such a case.

[0002]

2. Description of the Related Art In the above-described case, conventionally, a transmission type quarter-wave plate made of quartz is used to convert original polarized light into circularly polarized light. However, since the crystal transmission type quarter-wave plate is expensive, such a polarization conversion device is also expensive.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a means for converting linearly polarized light into circularly polarized light without using an expensive transmission type quarter wave plate made of quartz.

[0004]

A linearly polarized light is obliquely incident on a reflecting surface formed by forming a layer of a material having an appropriate refractive index on the mirror-like substrate and having an appropriate refractive index with respect to the substrate.

[0005]

When a thin layer is formed on the surface of the substrate and light is incident on the substrate, the light reflected from the surface of the thin layer and the reflected light from the boundary surface between the thin layer and the substrate interfere with each other, so that the light is incident on the substrate surface. Linearly polarized light is generally elliptically polarized light. Therefore, when light of a specific wavelength is incident on the surface of the substrate at a specific incident angle, the reflected light becomes circularly polarized light, and the purpose is achieved.

[0006]

FIG. 2 shows an embodiment of the present invention. This embodiment is a device for converting linearly polarized light emitted from a YAG (yttrium, arsenic, gallium) laser into circularly polarized light. Two laser beams emitted from two lasers are alternately circularly polarized and placed on the same optical path. It is an optical system that can be mounted.
On the x-axis, reference numerals 1 and 2 denote the above-mentioned lasers, respectively, which emit laser beams along the x-axis. These laser beams are reflected obliquely upward in the xz plane (vertical plane) by the mirror surfaces 3 and 4 so as to meet at the z axis. Reflecting plates 5 and 6 are alternately put in and out of this meeting point, the light emitted from the laser 1 is reflected in the y-axis direction by the reflecting plate 5, and when the reflecting plate 5 is replaced with the reflecting plate 6, the light emitted from the laser 2 is generated. Light emitted from the two lasers 1 and 2 reflected in the y-axis direction is alternately placed on the same optical path. With this optical system, mirrors 3, 4
Are ordinary mirrors, and 5 and 6 are reflectors having a function of converting linearly polarized light into circularly polarized light.

FIG. 1 shows the optical path of the emitted light of the laser 1 sent in the y-axis direction via the mirrors 3 and 5 of the optical system shown in FIG.
The laser beam is incident on the reflector 5 at an angle of 45 °,
It is reflected at an angle of °. In order to reflect such incident light as circularly polarized light, a double thin layer is formed on the surface of the reflection plate 5. The specifications of this thin layer are shown in FIG. The light emitted by the YAG laser is of two types having wavelengths of 1064 nm and 532 nm. FIG. 3A is for a wavelength of 1064 nm, and FIG. 3B is for a wavelength of 532 nm. The substrate 51 of the reflector 5 (same for the reflector 6) is made of Si and has a refractive index of no for the specified wavelength,
The refractive index of the first layer F52 is n2, the refractive index of the second layer 53 is n
If it is 2, the relation of no>n1> n2 is satisfied. Therefore, the first layer contains Si
N was used and MgF ₂ was used for the second layer. These refractive indices and layer thicknesses are listed in Figures 3A and 3B.

[0008]

EFFECTS OF THE INVENTION According to the present invention, an expensive crystal transmission type 1 /
It is possible to convert linearly polarized light into circularly polarized light with a reflecting element having a surface thin film formed without using a four-wave plate.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical configuration of the present invention.

FIG. 2 is a perspective view of an embodiment of the present invention.

FIG. 3 is a configuration diagram of a surface film of the reflection plates 5 and 6 in the above embodiment.

[Explanation of symbols]

 1, 2 YAG laser 3, 4 Mirror 5, 6 Reflective plate coated with surface film 51, 53 First and second thin layers

Claims (1)

[Claims] 1. A polarization conversion device characterized in that linearly polarized light is obliquely incident on the reflection plate so that reflected light becomes circularly polarized light by utilizing the polarization characteristics of the reflection plate having a thin layer formed on a substrate. apparatus.