JP2532650B2 - Method for manufacturing laminated polarizer - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a laminated polarizer used in optical isolators, optical switches and various optical sensors.

2. Description of the Related Art Polarizers are important elements in the construction of optical circuits. Due to the recent demand for miniaturization and high performance of optical elements, multilayer polarizers in which dielectrics and metals are alternately laminated in multiple layers have been proposed for polarizers (eg, S. KawaKami, Applied Optics (Appl.Opt). ) Vol22. (1983) 2426]. FIG. 3 shows the configuration diagram.

Normally, the dielectric layer 21 is formed by alternately laminating several thousand Å of SiO ₂ , and the metal layer 22 is formed by alternately laminating several tens of Å Al or Au. The element length is several tens of μm.

Next, the principle of this laminated polarizer will be briefly described. When passing through this element, TE mode light having an electric field component parallel to the laminated film is rapidly canceled because it is easily canceled by free electrons in the metal layer 22. On the other hand, TM-mode light that strikes an electric field component in the direction perpendicular to the laminated film can pass through the element without being canceled because free electrons cannot move in the dielectric layer 21 between the metal layers 22. Therefore, it is possible to obtain a polarizer that transmits only light having one polarization direction.

The characteristic of this polarizer is that the thickness L of the element is about several tens of μm, and the thickness can be reduced by about double digits as compared with other calcite prisms, polarizing beam splitters and the like.

Next, the manufacturing process of this element is shown in FIG. A glass substrate is used as the substrate, and as shown in FIG. 2a, a multi-source sputtering apparatus is used on the glass substrate 25 to alternately deposit several tens of liters of Al as a metal layer and several tens of liters of SiO ₂ as a dielectric layer to obtain a total film thickness. Ten
A multilayer film 20 of about 0 μm is produced. Next, as shown in FIG. 2B, the wafer is cut into an appropriate thickness (about 2 mm).
Further, as shown in FIG. 2c, the substrate 25 and the multilayer film 20 are cut out and fixed with a resin or the like to a reinforced glass block having a groove of about 2 mm in the central portion (to the extent that the part cut out in FIG. 2b fits) is formed. . This block requires the required element thickness (tens of μ
m) and a thickness suitable for optical polishing of both sides is cut out to a thickness of about 0.3 mm to 0.5 mm. Further, as shown in FIG. 2d, both sides are optically polished to have an optimum thickness (about 20 to 80 μm) as a polarizer. Finally, as shown in FIG. 2e, the laminated glass is completed by removing the reinforcing glass and optionally the substrate.

Problems to be Solved by the Invention Problems of the laminated polarizer are as follows. Since the substrate and the formed multilayer film have different coefficients of thermal expansion, the film thickness of the laminated film can be formed only up to about 200 μm, and if the film is formed thicker than that, the wafer is warped or the film is cracked and the yield is remarkably reduced. As a result, there is a problem that only a polarizer having a small effective beam diameter of about 200 μm or less can be obtained.

Means for Solving the Problems In order to solve the above problems, in the production of a laminated polarizer composed of a multilayer film of a metal layer and a dielectric layer, a groove line is provided on one main surface of the substrate, The main surface forming the film is divided into a large number of regions.

Action The reason why a thick film laminated polarizer having a high yield and a large effective beam diameter can be obtained by using the present invention will be described below.

When the total film thickness of the multilayer film is 200 μm or more, the substrate warps or film cracks occur because stress is generated when the temperature of the substrate after film formation is lowered to room temperature due to the difference in thermal expansion coefficient between the substrate and the laminated film. Is.

Therefore, to prevent cracks that occur in the multilayer film,
When the magnitude of stress is constant, it is effective to reduce the area where stress acts. That is, it is effective to reduce the area of each substrate, but handling a large number of small substrates makes the handling complicated and significantly increases the number of manufacturing steps of the element. Therefore, it is effective to use a substrate in which a groove-shaped line is provided on one main surface and divided into a large number of regions, and a multilayer film is formed on the main surface.

Example An example of the present invention will be described with reference to FIG. As the substrate, the quartz glass 101 shown in a having a thickness of 3 mm × 20 mm × 18 mm was used.

Next, using a dicing saw, 1 side 5 mm, depth 2 mm, width 0.2 mm
The grooves 102 were formed in a grid pattern. Next, in order to reduce processing strain and chipping due to the dicing saw, after an electric furnace anneal at 800 ° C. for 1 hour, etching was performed with a HF (10%) solution for 3 minutes.

Next, using the above substrate, a multi-source sputtering apparatus having an Al target and a SiO ₂ target was used. The substrate temperature is
At 400 ℃, the sputtering condition is that the SiO ₂ film formation rate is 2000Å /
min, RF power 1000 W, Al film formation rate 100 Å / min, RF power 100 W, gas flow rate was O ₂ (5%)-Ar (95%), and total flow rate was 120 SCCM. The cycle of the multilayer film 103 is Al90Å, SiO
To obtain a multilayer film having a thickness of 2mm was prepared from about 3900 cycles at ₂ 5000 Å.
Warpage of about 10 μm at the maximum was measured in the entire obtained sample (20 mm × 18 mm square), but no crack was generated in the substrate 101 and the multilayer film 103. This is a groove on a quartz glass substrate
This is because the stress is relaxed by providing 102.
Further, in the lattice-shaped area of 5 mm square, the warp was as small as about 1 μm.

A laminated polarizer was prepared from this sample by the procedure shown in FIG. 2, and the excellent results were obtained with its extinction ratio of 45 dB and insertion loss of 0.3 dB. Since this laminated polarizer has a length of several tens of μm in the light transmission direction shown by L in FIG. 3, an effective beam diameter of about 2 m is obtained when a substrate of 20 mm × 18 mm is used.
It was possible to cut out about 200 laminated polarizers.

In addition, the effective beam diameter was about 2 mm, and it was possible to replace it with a 2 mm square polarization beam splitter for a module that integrates a semiconductor laser and an optical isolator that have been used for optical communication.

In the present embodiment, the case where Al is used as the metal layer has been described, but the present invention can be applied to the case where another metal (for example, gold) is used.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to produce a thick film laminated polarizer by a method excellent in mass productivity, and it has been difficult to obtain an effective beam diameter of a laminated polarizer. Can be made larger.

Furthermore, a laminated polarizer with an effective beam diameter of about 2 mm is used as a polarizer for a module that integrates a semiconductor laser and an optical isolator currently used for optical communication and optical measurement, and is also used for an optical fiber sensor. It can be replaced with a conventional polarizing beam splitter or a prism using calcite, and its industrial value is extremely high.

[Brief description of drawings]

FIG. 1 is a perspective view of a laminated polarizer substrate manufacturing process according to an embodiment of the present invention, FIG. 2 is a diagram showing a chip processing process, and FIG. 3 is a principle diagram of the laminated polarizer. 101 …… quartz glass substrate, 103 …… metal / dielectric multilayer film,
102 …… groove, 20 …… dielectric, metal multilayer film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-55-117108 (JP, A) JP-A-50-92751 (JP, A) JP-B-44-27075 (JP, B1)

Claims (1)

(57) [Claims] 1. A substrate in which a groove line is provided on one main surface and is divided into a large number of regions is used, and a multilayer film of a metal layer and a dielectric layer is formed on the main surface of the substrate, which is required thereafter. A method for producing a laminated polarizer, which comprises cutting the substrate and the multilayer film into various element sizes and optically polishing both main surfaces of the element.