JPS6343101A - Transmission type diffraction grating - Google Patents

Abstract

PURPOSE:To simplify a production process by forming a grating of an inorg. dielectric material on a surface of a transparent substrate having the characteristic that the etching rate for specific etching is considerably lower than the rate for the prescribed inorg. dielectric material. CONSTITUTION:The desired grating consisting of SiO2 is formed on one surface of a quartz crystal 5 which is the substrate by depositing the SiO23 over the entire surface thereof and applying a reflection preventive coating 4 on the rear surface thereof, then etching the surface with a hydrofluoric acid etching soln. The quartz crystal substrate 5 is much lower in the etching rate by the hydrofluoric acid etching soln. than the SiO23; viz., said rate is about 1/10 lower; therefore, the substrate is not substantially attacked by the etching soln. before the grating formation of the SiO2 is completed. The good diffraction grating is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a diffraction grating, especially a transmission type 1-ul diffraction grating used for pickup of various optical devices or optical disk devices (prior art). With the development of microfabrication technology, the standard method for manufacturing diffraction gratings used in various optical devices has become to form a grating by etching a metal or dielectric material adhered to a substrate.

However, diffraction gratings based on the above-mentioned method, especially transmission type ones, generally use inexpensive general-purpose glass as a substrate and form the grating on its surface with a dielectric material such as KsiOz. Since the etching speed is almost the same as that of the etching method, there is a drawback that it requires a complicated manufacturing process such as a lift-off etching method and is expensive.

(Object of the Invention) The present invention has been made in order to eliminate the defects of the conventional diffraction grating as described above. The purpose is to provide a type diffraction grating.

(v1 essential point of the invention) In order to achieve the above-mentioned object, the diffraction grating of the present invention is characterized in that the etching rate of the dielectric material such as 5i02, which is the material forming the grating, is significantly higher than that of quartz or the like. This can be achieved using a simple etching process by combining these materials.

(Example) The present invention will be described in detail below based on illustrated embodiments.

Prior to describing embodiments, a conventional manufacturing process for a diffraction grating will be briefly described to aid understanding of the present invention.

FIG. 2 is a diagram illustrating the manufacturing process of a conventional transmission type diffraction grating, in which an inexpensive general-purpose glass is used as a substrate 1, and on one surface thereof, for example, Ag2 is evaporated over the entire surface, and then this is etched to form a predetermined pattern. The back surface of the metal grating is etched with an etching solution containing an anti-reflection coating. This is because if a hydrofluoric acid-based etching solution is used, the substrate will be attacked at the same time.

Therefore, as mentioned above, a simple etching process cannot be used and is expensive.

In order to solve this problem, the diffraction grating of the present invention is manufactured using materials and processes as shown in FIG.

First, a crystal 5 is used as a substrate (5iO
z3 is deposited on the entire surface, and then an anti-reflection coating 4 is applied to the back surface.tc) This is etched using a hydrofluoric acid-based etching solution to form a desired grating 8102.

Since the etching speed of the crystal substrate 5 with a hydrofluoric acid etching solution is much slower (about 1/10) than that of 5i023, the etching solution is substantially removed by the time the grating formation is completed at 8:02 K.

A good diffraction grating can be obtained without being affected by

Although only a diffraction grating made of a combination of quartz crystal and 8i02 has been described above, the present invention is not limited thereto, and is a combination in which the etching rate of the substrate material is much slower than that of the grating material. Various materials can be used for the grating as long as they allow light to pass through. For example, the substrate may be quartz, synthetic quartz, or artificial sapphire, and the grating material may be Sio*, TiOz, or A.
I203 and the like are suitable, and these may be combined as appropriate depending on the design conditions.

(Effects of the Invention) Since the present invention is constructed as described above, the manufacturing process is extremely simple and the cost is therefore low, so that it exhibits a remarkable effect in reducing the number of S optical devices, especially optical disks.

[Brief explanation of the drawing]

Figures 1 (al to d) are diagrams explaining the manufacturing process of the diffraction grating of the present invention, and Figure 2 (al to tel are diagrams explaining the manufacturing process of the conventional diffraction grating. 1 and 5...・・・・・・Transparent substrate. ３・・・・・・・・・Grating.

Claims (3)

[Claims] (1) A transmission diffraction grating characterized in that a grating is formed of the inorganic dielectric material on the surface of a transparent substrate whose etching rate for a specific etching is significantly slower than that for a predetermined inorganic dielectric material. . (2) The transmission diffraction grating according to claim (1), wherein the transparent substrate is quartz, synthetic quartz, or artificial sapphire. (3) The transmission diffraction grating according to claim (1), wherein the inorganic dielectric material is SiO_2, TiO_2 or Al_2O_3.