JPS61275710A - Distributed index anamorphic plane microlens and its manufacture - Google Patents

Abstract

PURPOSE:To collimate an elliptic beam emitted by a semiconductor laser and to facilitate the manufacture of a lens by forming a semi-elliptic distributed index area which has a long and a short axis on the surface of a transparent substrate in the transparent substrate. CONSTITUTION:The semi-elliptic distributed index area 8 formed in the plate type transparent substrate 7 has its refractive index distribution formed so that the refractive index is highest in the center of the semi-elliptic body and decreases with the radius. The optical axis 9 is on a straight line running in the center of the elliptic hemisphere at right angles to the substrate and the focal length of the distributed index area is longer in the long-axis direction (X than in the short-axis direction (Y). This microlens has the semi-elliptic distributed index area formed by fitting a mask which has an elliptic aperture part in a predetermined shape on the surface of a plate glass body and then performing an ion exchange between ions which provides a high refractive index and alkali ions in the glass body through the aperture part.

Description

Detailed Description of the Invention [Field of Industrial Application] This invention relates to a microlens that can be used in micro-optical systems such as optical communication, and in particular, it relates to a microlens that is semi-ellipsoidal and has a major axis and a minor axis on the surface of a substrate. The present invention relates to a gradient index type anamorphic flat plate microlens in which a gradient index region is formed in a transparent substrate, and a method for manufacturing the same.

[Prior Art] As shown in FIG. 4, a refractive index distribution type flat plate microlens has several refractive index distribution regions 2 having a lens effect in a transparent plate-like substrate 1. It focuses light like this. Because both sides of this lens are flat, it is easier to process than general spherical or aspherical lenses, and it is also possible to create regions with multiple lens effects on one substrate at the same time. There are advantages. As such a gradient index flat plate microlens, one in which the refractive index distribution region is hemispherical or semi-cylindrical has been devised.

On the other hand, although a semiconductor laser is often used as a light source in an optical system in optical communication, the beam 6 emitted from the semiconductor laser 4 has an astigmatic difference l as shown in the plan and side views of FIGS. 5A and 5B. Since the radiation angle is different between the direction perpendicular to the active layer 5 and the direction parallel to it, the beam becomes an elliptical beam. As an optical lens system for collimating such a beam, a flat plate microlens having a hemispherical refractive index distribution region is not optimal.

[Problems to be Solved by the Invention] As a method of collimating light with an elliptical spread into circular parallel light, an optical system in which Kamabok shaped lenses are orthogonally combined is considered. This becomes complicated due to the curvature and wall thickness of the lens used to obtain parallel light, making the lens extremely difficult to manufacture. For example, when using a flat plate microlens having a semi-cylindrical refractive index distribution region,
As described in Publication No. 503, the numerical apertures N, A,
It is necessary to superimpose different lenses so that they are orthogonal to each other.

An object of the present invention is to provide a gradient index anamorphic flat plate microlens that can be used for collimating an elliptical beam emitted from a semiconductor laser, and a method for manufacturing the same.

[Means for Solving the Problems] In order to collimate light with astigmatism such as a semiconductor laser, a lens having a different focal length in each direction perpendicular to the optical axis is required.

The present invention relates to a flat plate microlens having such properties, that is, a refraction device characterized in that a semi-ellipsoidal refractive index distribution region having a major axis and a minor axis is formed within a transparent substrate on the substrate surface. This invention relates to a rate distribution type anamorphic flat microlens.

As shown in FIGS. 1A to 1C, this lens has a semiellipsoidal refractive index distribution region 8 in a plate-shaped transparent substrate 7, and the refractive index distribution is semiellipsoidal as shown in FIG. It is highest in the center of the body and decreases as the diameter increases. In FIG. 2, reference numeral 10 indicates a refractive index distribution curve in the y and two directions, and reference numeral 11
indicates a refractive index distribution curve in the X direction. The optical axis lies on a straight line passing through the center of the elliptical hemisphere in a direction perpendicular to the substrate, but the refractive index distribution is not rotationally symmetrical with respect to this optical axis, so the focal length varies depending on the direction in the plane perpendicular to the optical axis. is a tribute. That is, the focal length of the refractive index distribution region in the major axis direction (X direction) is longer than that in the minor axis direction (y direction).

As a method for manufacturing the gradient index type anamorphic flat microlens according to the present invention, there is a method using ion exchange of glass. That is, after attaching a mask having an elliptical opening with a predetermined shape to the surface of a plate glass body, ion exchange between ions that produce a high refractive index and alkali ions in the glass body is performed through the opening. This forms a semi-ellipsoidal refractive index distribution region within the glass body.

First, as shown in FIG. 3, a mask 13 which has an elliptical opening 14 on the surface of a glass substrate 12 and is impermeable to ions can be seen. As the mask material, a titanium film or the like formed by sputtering or vacuum evaporation can be used. Further, the major axis and minor axis of the opening must be selected depending on the characteristics of the intended lens and the ion exchange conditions.

Next, the glass substrate is immersed in a molten salt containing ions such as silver and thallium that produce a high refractive index, so that alkali ions such as Ni+ and Na+ in the glass substrate and ions that produce a high refractive index in the molten salt are removed. The ion exchange takes place through an elliptical mask opening. By this ion exchange, a semi-ellipsoidal refractive index distribution region 8 as shown in FIGS. 1A to 1C is formed in the glass substrate.

After ion exchange, by removing the mask 13 and polishing the glass surface, a gradient index type anamorphic flat plate microlens can be manufactured.

[Example 1 Optical glass called TiF6 polished into a plate shape with a thickness of 5n+m (P206 47.9%, N820 in weight%)
19.8%, K20 7.7%, Af203
3.7%, T i Q215.11%, other 1.6%
) was coated with a titanium film with a thickness of 1.3 μm as a mask material, and then the major diameter was 20 μm using photolithography.
An elliptical frontage portion with a width of 0 μm and a short axis of 100 μm was formed. This was immersed in a molten salt of 40% heavy R% t'AgNO3 and 60% KNO3 at 350°C for 70 hours to perform ion exchange. By removing the ion exchange attack, removing the titanium mask, and polishing the substrate surface again, the major diameter of the substrate surface at 4° was reduced to 1.2.
9111, minor axis 1.17aug and depth 0.57
A refractive index gradient type anamorphic flat plate microlens having a semi-ellipsoidal refractive index distribution region of mm was obtained. The focal lengths of this lens were different in the major axis direction and the minor axis direction, and were 2.47 am and 2.04+ am, respectively.

[Effects of the Invention] As described above, the present invention is an anamorphic flat plate microlens having a semi-ellipsoidal refractive index distribution region, so it can be used for collimating an elliptical beam emitted from a semiconductor laser, etc. can do. In addition, in the microlens of the present invention, a mask having an elliptical opening with a predetermined shape is attached to the surface of a plate-like glass body, and then ions having the opening that produce a high refractive index and ions inside the glass body are attached. Since it is obtained by ion exchange with alkali ions, a flat microlens having a semi-ellipsoidal refractive index distribution region as described above can be easily manufactured.

[Brief explanation of the drawing]

1A to 1C are a plan view, a front view, and a side view of a gradient index type anamorphic flat plate microlens according to the present invention, FIG. 2 is a refractive index distribution curve of the lens, and FIG. FIG. 4 is a perspective view showing an example of a glass substrate with a mask applied to the manufacturing method of a rate distribution type anamorphic flat plate microlens, FIG. 4 is a perspective view illustrating a general flat plate microlens, FIGS. Figure 5B is a plan view and a side view of the semiconductor laser. 7...Glass substrate, 8...Refractive index distribution area, 9...
- Optical axis, 10... refractive index distribution curve in y and two directions,
11... Refractive index distribution curve in the X direction, 12... Glass substrate, 13... Mask, 14... Mask opening. Applicant Hoya Co., Ltd. Agent Masayuki Asakura Figure 1A
Figure 1C Old figure Figure 2 yeZ

Claims (1)

[Claims] 1. A flat plate having a refractive index distribution region in a transparent substrate, which has an optical axis in a direction perpendicular to the substrate surface, and whose refractive index decreases radially around the point where the optical axis intersects with the substrate surface. 1. A gradient index anamorphic flat plate microlens, characterized in that the shape of the gradient index region inside the transparent substrate is a semi-ellipsoid having a major axis and a minor axis on the surface of the substrate. 2. After attaching a mask having an elliptical opening of a predetermined shape to the surface of a plate glass body, this is immersed in a molten salt containing ions such as thallium and silver that produce a high refractive index,
A refractive index distribution type analyzer characterized in that an elliptical hemispherical refractive index distribution region is formed in the glass body due to the concentration distribution of ions that produce the high refractive index by performing ion exchange through the opening. Manufacturing method of morphic flat plate microlens.