JPH0829653A - Arranging structure of spherical lens and formation of v-grooved substrate - Google Patents

Abstract

PURPOSE:TO provide a spherical lens arranging structure which is arranged with spherical lenses with good accuracy, has excellent stability of fixing strength and is capable of averting degradation in optical coupling efficiency by eclipsing loss. CONSTITUTION:The diameter D of the spherical lenses 102 is 200mum and a substrate (1) 103 consists of an Si material and is formed with V-grooves varying in width. The V-groove width on the left side is 160mum and the V-groove width on the right side is 230pm. the V-groove depth on the right side is 100mum and a difference H in level in the direction perpendicular to the lenses of the stepped parts of the V-grooves is 28.5mum. A substrate (2) 104 is constituted in a similar manner as the substrate (1) 103. The V-groove width on the left side in the state of Fig. is 230p and the V-groove width on the right side is 1607mum and is made shorter than the length in the V-groove direction of the substrate (1) 103 in an embodiment. The substrates 103, 104 are fixed in theplane part adjacent to the groove parts across the aspherical lenses 102. The aspherical lenses 102 are fixed by the upper and lower V-grooves and the right and left stepped parts of the V-grooves. The effective diameter of the lenses, defined as DELTA' is so set as to satisfy H<=(D-D')/2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element module for optically coupling an optical device and an optical fiber via a spherical lens, and more particularly to a structure in which spherical lenses are preferably arranged.

[0002]

2. Description of the Related Art In recent years, there has been active development of an optical interconnect technology for connecting devices such as a large-scale computer and a broadband switch and between boards in place of an electric coaxial cable. In optical interconnect technology, it is important to efficiently optically couple parallel optical devices and optical fiber arrays. Therefore, a method of coupling with an optical fiber through a lens is used. Further, the lenses need to be regularly arranged in a number equal to or larger than the number of parallel optical devices. The lens includes a gradient index flat plate microlens, a convex microlens formed by glass press molding, and a spherical lens.
The flat and convex microlenses have poorer optical coupling efficiency than spherical lenses. The spherical lenses need to be arranged in an array for coupling with parallel optical devices. As a conventional lens array structure, one described in JP-A-5-333246 is known. The spherical lens is arranged in a plurality of cylindrical holes formed in a metal plate shape at regular intervals, and is fixed with a low melting point glass. Further, in the structure in which the spherical lens is fixed with solder, Au / Pt / Ti is attached to the lens fixing surface.
Forming a sputtering film. Lens diameter is 200 μm
The lens arrangement interval is 250 μm. The hole shape has an outer diameter of 50 to 100 μm and a depth of 50 to 100 μm. The holes on the metal plate are formed by photo-etching to ensure the alignment accuracy.

[0003]

However, in the conventional spherical lens array structure described above, the lens fixing strength is not sufficiently taken into consideration. Generally, the fixing strength is proportional to the connection area. Therefore,
The connection area is 2 because the hole shape is 50-100 μm
It is very small, about 8 × 10 ³ mm ^2, and since the tensile strength of glass is about 3 kgf / mm ² , the fixing strength is also small, about 20 gf. Further, in the lens single-sided connection structure, a moment force acts on the connection part by an external force applied to the upper part of the lens, and the lens is broken by a force smaller than the tensile or shear strength. That is, as in the principle of leverage, the fixing strength is reduced depending on the ratio of the distance from the fulcrum to the point to which the external force is applied and the distance from the fulcrum to the point of action. From the above, the above spherical lens array structure has a problem that the lens fixing strength is small.

In the conventional spherical lens array structure described above, attention was not paid to the lens fixing accuracy. Generally, when the light from the optical device passes through the lens, the variation of the lens array is magnified and enters the fiber. Since the holes of the metal substrate are formed by photoetching, the variations in the optical axis direction and the accuracy of the arrangement interval are good. However, the lens height direction is
It is unstable because there is nothing to press from above. When the low-melting glass is solidified after melting, bubbles are generated to push the lens upward. From the above, in the spherical lens array structure,
There was a problem that the fixing accuracy in the height direction of the lens was poor.

In the conventional ball lens array structure described above, consideration for metallization and patterning on the ball lens has not been sufficient. Generally, a vapor deposition or sputtering method is known as a method for metallizing a substrate. For patterning, milling using a photolitho mask is known. However, it is not easy to metallize a spherical lens having a diameter of 200 μm on one surface only, because of the method of holding the lens and the wraparound of metal. Patterning into spherical lenses is even more difficult. First, apply photolitho to the ball lens. Generally, in the application of photolithography, after applying the photoresist on the substrate, the substrate is rotated to make the photoresist have a uniform film thickness. Next, pattern the photolitho on the ball lens. And to mill it. Generally, the milling is perpendicular to the patterned surface in the milling direction. However, with a spherical lens, the lens cannot be held so that spin coating cannot be performed, and it is difficult to align the patterned lens surfaces in the milling direction. From the above, in the spherical lens array structure,
Metallization to the spherical lens and patterning are not possible,
There was a problem that the lens could not be fixed with solder.

In the above-mentioned conventional spherical lens array structure, attention has not been paid to the reduction of coupling efficiency due to eclipse loss. When the spherical lens is fixed in the hole of the metal plate, the angle between the lens surface and the fixed substrate surface is small, so that the connecting material rises to the lens surface due to the capillary phenomenon and surface tension. Therefore, the light emitted from the optical device is blocked (shaded) by the connecting material on the lens surface, and the dimmed light is incident on the optical fiber, and the optical coupling efficiency is reduced. As described above, the above spherical lens array structure has a problem in that the reduction of the optical coupling efficiency due to the eclipse loss cannot be avoided.

An object of the present invention is to provide a ball lens array structure in which ball lenses are arrayed with high precision and stability of fixed strength is excellent. Another object of the present invention is to provide a spherical lens array structure capable of avoiding a decrease in optical coupling efficiency due to eclipse loss.

[0008]

In order to achieve the above object, the present invention comprises at least one spherical lens, and a substrate 1 and a substrate 2 having V grooves equal to or more than the number of spherical lenses,
A ball lens array structure in which the ball lenses are sandwiched and held by the V grooves of the substrate 1 and the substrate 2, and two kinds of V grooves having different widths are set in the groove direction of each substrate. A stepped portion is provided in the groove, and the ball lens is held by the V groove of the substrate 1 and the substrate 2, and the ball lens is held by the stepped portion of the groove of the substrate 1 and the substrate 2 to hold the ball lens. I am configuring. Further, the size of the V groove width in each of the substrates is reversed between the substrate 1 and the substrate 2 while the ball lens is sandwiched between the substrate 1 and the substrate 2.
Further, assuming that the lens outer diameter is D and the lens effective diameter is D ′, the vertical direction V groove step H between the V groove surfaces of the substrate 1 and the substrate 2 and the spherical lens is H ≦ (DD ′). It is set to satisfy the condition of / 2. Further, the substrate 1 and the substrate 2 are fixed by a flat surface portion adjacent to the V groove. A method of forming a V-groove substrate for the substrate 1 and the substrate 2 in an array structure of spherical lenses, in which a step of forming a narrow V-groove in advance on the substrate 1 and the substrate 2 and a SiO ₂ film on the substrate again. The stepped V-groove is formed on the substrate by the step of forming the V-groove and the step of anisotropically etching a wide V-groove again on a predetermined region on the narrow V-groove of the substrate.

[0009]

According to the above means, a step is provided by setting the V groove widths of the substrate 1 and the substrate 2 to two types in one row, and the spherical lens is sandwiched between the substrate 1 and the substrate 2, and the step edge portion is used. The substrate 1 processed by etching by holding the substrate 1 accurately
The spherical lens arranged in the V groove is held in the V groove of the substrate 2 and contacts the V groove at four points. Therefore, there is no extra space in the vertical direction, and variation in the lens height direction can be suppressed. In addition, by reversing the direction of the V-groove width in the substrate between the substrate 1 and the substrate 2, the spherical lens arranged in the wide V-groove of the substrate 1 has the narrow V-groove and the wide V-groove. Since the edge portion formed by the narrow V groove and the wide V groove of the substrate 2 is suppressed in the optical axis direction, the variation in the lens optical axis direction can be suppressed. Furthermore, since the connection area can be set large by fixing the substrate 1 and the substrate 2 at the plane portion adjacent to the V groove, the fixing strength can be improved. Further, since the central portion of the ball lens array can also be fixed by the flat portion adjacent to the V groove, it is possible to prevent the warp of the substrate, and to mount the ball lens in the height direction on the substrate 1.
Since it can be constrained to, it is possible to suppress variations in the lens height direction. Further, V of the substrate 1 and the substrate 2
The vertical direction V groove step H between the groove surface and the spherical lens is H ≦ (D−
By setting D ′) / 2, the V-groove step can hold the lens without hindering the lens effective diameter, and the light from the optical device is incident on the lens effective diameter at a light blocking rate of 0%, resulting in eclipse loss. It is possible to avoid a decrease in optical coupling efficiency. Further, the V-grooves of the substrate 1 and the substrate 2 are formed by anisotropic etching of Si, so that the photolithography processing accuracy is high and the S
Since the etching rate of the i crystal (111) plane is slow, overetching can be controlled, so that the array interval can be processed with high accuracy. In addition, a step of forming a narrow V groove in advance on the substrate 1 and the substrate 2, a step of forming SiO ₂ again on this substrate, and a step of forming a wide V groove on the narrow V groove of this substrate again. By forming the stepped V-groove on the substrate from the anisotropic etching step, the processing accuracy is deteriorated due to over-etching of the stepped portion which occurs when the V-groove is formed in the convex pattern by one-time anisotropic etching. Can be reduced. In other words, the convex step is
Since a crystal plane with a high etching rate appears on the Si crystal (100) plane, the etching controllability is poor, overetching occurs, and the processing accuracy decreases. In the etching of the rectangular pattern, a surface having a high etching rate does not appear on the Si crystal surface unlike the convex pattern. Therefore, it is necessary to separately etch the narrow rectangular pattern and the wide rectangular pattern to overlap the V groove. It is possible to avoid a reduction in processing accuracy due to over-etching of the V groove step portion.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a structural view of a spherical lens array according to a first embodiment of the present invention. FIG. 2 is a detailed view of the spherical lens array structure of the first embodiment according to the present invention. (A) is an exploded view of a spherical lens array structure, (b) is a plan view of the substrate of (a) seen from the direction of the arrow. 1 and 2, a spherical lens array structure 1
01 includes a spherical lens 102, a substrate (1) 103, and a substrate (2) 104. The spherical lens 102 is arranged by the substrate (1) 103 and the substrate (2) 104. The board (1) 103 and the board (2) 104 are connected by solder.

The spherical lens 102 is made of sapphire glass. The diameter is 200 μm and the refractive index n is 1.77778.
(Wavelength λ = 1.3 μm). Substrate (1) 103 is
It is made of Si material. V-grooves having different widths are formed in the substrate (1) 103 in the groove direction. That is, the left V groove and the right V groove in the figure have different widths. V groove width on the left side is 160μ
m, and the V groove width on the right side is 230 μm. The left V-groove depth is 113 μm, and the right V-groove depth is 1 μm.
62.4 μm, the step in the direction perpendicular to the lens in the V-groove step portion (the contact point between the V-groove and the ball lens 102,
The step difference between the V-grooves on the line passing through the center of is 28.5 μm. After the Au / Ni / Ti vapor deposition film is formed on the flat surface portion of the substrate (1) 103, a Pb95-5Sn solder layer of 10 μm is formed.

The substrate (2) 104 is made of Si material. V-grooves having different widths are formed in the substrate (2) 104 in the groove direction. The V-grooves on the substrate (2) 104 are arranged as shown in the figure.
It has an opposite relationship to the arrangement on the substrate (1) 103. That is, the V groove width on the left side of the figure is 230 μm and the V groove width on the right side is 160 μm. The V groove depth on the left side is 162.4 μm, and the V groove depth on the right side is 113 μm. The step of the V-groove step portion in the direction perpendicular to the lens is 28.5 μm. Further, the length of the substrate (2) 104 in the V groove direction is the same as that of the substrate (1).
The length is such that the spherical lens can be held at the step edge portions of 103 and (2) 104, and is shorter than the length of the substrate (1) 103 in the V groove direction in the embodiment. An Au / Ni / Ti vapor deposition film is formed on the flat surface of the substrate (2) 104.

FIG. 3 shows a method for forming V-grooves on the substrates (1) 103 and (2) 104 in the spherical lens array structure of the first embodiment.
Will be explained. First, the Si substrate (100 surface) is thermally oxidized to form a SiO ₂ film. Next, after forming a narrow Si etching mask pattern by photolithography and etching of the SiO ₂ film, Si is etched with a KOH aqueous solution using it as a mask. And again Si
An O ₂ thermal oxide film is formed. Then, a wide Si etching mask pattern is formed in a predetermined region on the narrow V groove. Finally, using it as a mask, Si is etched with a KOH aqueous solution to form a step in the V groove.

According to the first embodiment, the substrate (1) 103
And (2) 104, the V-groove width is set to two kinds of 160 μm and 230 μm in one groove as shown in FIG. 2 to form a step, and the spherical lens is provided on the substrates (1) 103 and (2) 10
By being sandwiched by 4 and held by the step edge portion, the spherical lens contacts the V groove at four points. The sphericity of the spherical lens is ± 2 μm. Therefore, there is no extra space in the vertical direction, and the variation in the lens height direction can be suppressed to ± 2 μm. In addition, the V-groove widths of 160 μm and 230 μm in the substrate correspond to the substrate (1) 103.
And (2) 104 are reversed, so that the substrate (1) 10
By holding the optical axis direction of the lens at the step edge portions of 3 and (2) 104, the spherical lens has 4 points in the V groove optical axis direction (2 points on the substrate (1) and 2 points on the substrate (2)). ). Therefore, there is no extra space in the optical axis direction, and the variation in the lens height direction can be suppressed to ± 2 μm.

Further, substrates (1) 103 and (2) 104
Is 10 μm thick Pb95-5S on the flat surface adjacent to the V groove.
The n solder 105 layer provided by fixing, soldering tensile strength for the connection area can be set large as 0.116Mm ² can be improved fixing strength to 230gf because it is 2 kgf / mm ^2. Further, since the central portion of the spherical lens array can also be fixed by the flat portion adjacent to the V groove, substrate warpage can be prevented and the spherical lens can be restrained in the height direction in the lens height direction. The variation of can be suppressed.

A step of previously forming a V groove having a width of 160 μm on the substrates (1) 103 and (2) 104, a step of forming SiO ₂ again on this substrate, and a step of 160 μm of this substrate
Since the V-groove having a width of 230 μm is again overlapped with the V-groove having the width and the anisotropic etching is performed, the substrate has a step difference of 35.
V-shaped groove of μm (the step in the direction perpendicular to the lens is 28.5μ
By forming m), it is possible to etch the 35 μm stepped V-groove without exposing the (100) plane, which is a crystal plane having a high etching rate, so that the etching controllability is good and the processing can be performed with an accuracy of ± 2 μm. According to the first embodiment, there is an effect that the spherical lenses can be arranged with a high accuracy of ± 2 μm and can be fixed with a high strength of 230 gf.

FIG. 4 is a sectional view of an optical element module using the spherical lens array structure of the second embodiment according to the present invention. In FIG. 4, the optical element module 201 includes a spherical lens 20.
3, a spherical lens array structure including a substrate (1) 204 and a substrate (2) 205, an optical element array 206, a submount 207, an IC substrate 208, a wiring substrate 209, a package 210, and a cap 211. The optical fiber array 212, the receptacle 213, the leads 215, the electrode substrate 216, and the window glass 217 are provided. Electrodes of optical element array 206 and electrodes of submount 207, electrodes of submount 207, electrodes of wiring board 209, and IC
The electrodes of the substrate 208 are connected by Au wire lines 214. The optical element array 206, the spherical lens 203, and the optical fiber array 212 are optically coupled.

The spherical lens array structure consisting of the spherical lens 203, the substrate (1) 204 and the substrate (2) 205 is almost the same as the spherical lens array structure of the first embodiment.

Substrate (1) 204 and substrate (2) 205 are S
It consists of i material. V-grooves having different widths are formed on the substrate (1) 204 and the substrate (2) 205 by the method shown in FIG. V-groove width is 160 μm and 230 μm, V-groove depth is 1
13 μm and 162.4 μm. The step of the V-groove step portion in the direction perpendicular to the lens is 28.5 μm. The distance between the lens surface and the optical element when the lens is mounted is 40-140μ
An optical element mounting positioning guide is provided at a distance from the V groove step portion in the optical axis direction so as to be set to m. Board (1)
After forming the Au / Ni / Ti vapor deposition film on the flat surface of 103, 1
A 0 μm Pb95-5Sn solder layer is formed.

Each optical element of the optical element array 206 is composed of an InP-based laser diode or an InGaAs-based pin-type photodiode having an oscillation wavelength of 1.3 μm. The emission angle of the laser diode is approximately 40 ° in the horizontal and vertical directions.
The array spacing is 250 μm. Submount 207
Is made of AlN having a thermal expansion coefficient close to that of the optical element array 206. Au / Ni / Ti on the surface of the submount 207
After vapor deposition, dry etching is performed to form a wiring pattern. On the back surface of the submount 207, a vapor deposition film made of Au / Ni / Ti is formed for solder fixing to the package 210. The IC substrate 208 is Ga
Composed of As. The wiring board 209 is made of Al ₂ O ₃ .
The package 210 includes a base portion at the bottom of the figure and a frame portion at the top of the figure. The base part has high thermal conductivity Cu-
The W alloy and the frame part are made of Kovar alloy. Au / Ni plating was applied to the surfaces of the base portion and the frame portion. The cap 211 is made of Kovar alloy having the same thermal expansion coefficient as the frame portion of the package 210. The fiber arrays 212 are arranged at an array interval of 250 μm.

The mounting process of the optical element module of the second embodiment will be described with reference to FIG. FIG. 5 is a mounting process diagram of the second embodiment. Hereinafter, the steps will be described in order.
The optical element module 201 includes a spherical lens 203, a spherical lens array structure including a substrate (1) 204 and a substrate (2) 205, an optical element array 206, and a submount 207.
An IC substrate 208, a wiring substrate 209, a package 210, a cap 211, and an optical fiber array 212.
A receptacle 213, leads 215, an electrode substrate 216, and a window glass 217. (1) Optical Element-Spherical Lens Optical Coupling Step First, the optical element array 206 is fixed to the substrate (1) 204 optical element mounting portion of the spherical lens array structure by soldering without adjustment. (2) Ball Lens Array Structure Mounting Step Next, the ball lens array structure on which the optical element array 206 is mounted is arranged and fixed at a predetermined position inside the package 210. When placed, the window glass 217 in the package 210
Hit it. In addition, the IC mounted on the wiring board 209
The substrate 208 is fixed to the package 210, and the Au wire 2
Wire 14 (3) Airtight sealing step After that, the cap 211 is fixed to the package 210 by seam welding in the N ₂ gas chamber, and hermetically sealed. (4) Fiber Alignment Step Then, the optical element in the package 210 is driven so that the light passing through the spherical lens 203 is incident on the optical fiber array 212 inserted in the receptacle 213. After making it incident,
The optical fiber array 212 is scanned in the direction perpendicular to the optical axis and moved to the peak position from the light intensity distribution. (5) Receptacle Fixing Step Finally, the package 210 and the receptacle 213 in which the optical fiber array 212 is inserted are YAG-welded at a position where the optical coupling between the optical element array 206, the spherical lens 203 and the optical fiber array 212 is at a peak.

According to the second embodiment, in addition to the first embodiment, the diameter D of the spherical lens 203 is 200 μm, and the V groove surface of the substrates (1) and (2) and the vertical V groove of the spherical lens are formed. The step H is 28.5 μm, the distance between the lens surface and the optical element is 40 to 140 μm, and the emission angle of the laser diode is about 40 °, so the lens effective diameter D ′ can be said to be 100 μm.

In order that the V-groove step does not hinder the effective diameter of the lens, the relationship of H ≦ (DD ′) / 2 must be satisfied, but in the case of the above numerical conditions, this relationship is satisfied, The V-groove step can hold the lens without hindering the lens effective diameter, and allows light from the optical device to enter the lens effective diameter at a light blocking rate of 0%, thereby avoiding reduction in optical coupling efficiency due to loss. it can. Since a positioning guide is provided in the optical element mounting portion of the substrate (1) 204, the positions of the spherical lens optical axis direction and the arrangement direction can be adjusted without adjustment. Further, in the height direction perpendicular to the optical axis, the positioning guide is etched in consideration of the thicknesses of the optical element array and the submount in advance, so that the alignment can be performed without adjustment. According to the second embodiment described above, in addition to the first embodiment, there is an effect that the reduction of the optical coupling efficiency due to the eclipse loss can be avoided.

[0024]

According to the present invention, the vertical alignment accuracy of the spherical lenses can be improved. In addition, the accuracy of arrangement of the spherical lenses in the optical axis direction can be improved. Further, it is possible to eliminate the decrease in optical coupling efficiency in the optical device. Further, the lens array fixing strength can be improved. In addition, the etching processing accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a ball lens array structure of a first embodiment.

FIG. 2 is a diagram showing details of a spherical lens array structure of the first example.

FIG. 3 is a diagram illustrating a method of manufacturing a V-groove substrate according to the first embodiment.

FIG. 4 is a diagram showing a cross section of an optical element module according to a second embodiment.

FIG. 5 is a diagram showing a mounting process of the optical element module of the second embodiment.

[Explanation of symbols]

 101 ball lens array structure 102, 203 ball lens 103, 204 substrate (1) 104, 205 substrate (2) 201 optical element module 206 optical element array 207 submount 208 IC substrate 209 wiring board 210 package 211 cap 212 optical fiber array 213 Receptacle 214 Au wire 215 Lead 216 Electrode substrate 217 Window glass

Claims (5)

[Claims] 1. At least one ball lens, and a substrate 1 and a substrate 2 having the same number or more V-grooves as the ball lens,
An arrangement structure of ball lenses is provided such that the ball lenses are sandwiched and held by the V grooves of the substrate 1 and the substrate 2, and two kinds of V grooves having different widths are set in the groove direction of each substrate. A step portion is provided in the groove, and V of the substrate 1 and the substrate 2 is
An array structure of spherical lenses, wherein the spherical lenses are held by the grooves and the spherical lenses are held by the stepped portions of the grooves of the substrate 1 and the substrate 2 so as to hold the spherical lenses. 2. The ball lens array structure according to claim 1, wherein the V groove widths of the substrates 1 and 2 are arranged in a large and small manner in a state where the ball lenses are sandwiched between the substrates 1 and 2.
An array structure of spherical lenses characterized by being inverted by. 3. The spherical lens array structure according to claim 1, wherein the lens outer diameter is D and the lens effective diameter is D ′.
A spherical lens, characterized in that a vertical V-groove step H between the V-groove surfaces of the substrate 1 and the substrate 2 and the spherical lens is set so as to satisfy the condition of H ≦ (DD ′) / 2. Array structure. 4. The ball lens array structure according to claim 1, wherein the substrate 1 and the substrate 2 are fixed by a flat portion adjacent to the V groove. 5. A method for forming a V-groove on the substrate 1 and the substrate 2 in the array structure of spherical lenses according to claim 1, wherein a step of forming a narrow V-groove on the substrate 1 and the substrate 2 in advance. A stepped V groove is formed on the substrate by a step of forming a SiO ₂ film again on this substrate and a step of overlapping a wide V groove again on a predetermined region on the narrow V groove of this substrate and anisotropically etching it. A method for forming a V-groove substrate, which comprises: