JPH09288226A - Optical element module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relax assembling precision of a first lens for a semiconductor element and to make possible using the lens with excellent workability by making a gap between a second lens and a third lens adjustable. SOLUTION: The second lens 6a constituted of a pillar surface and a plane converging a beam in the vertical direction and the third lens 8a constituted of the pillar surface and the plane converging the beam in the horizontal direction are arranged shifting by nearly 90 deg. around an optical axis, and by adjusting the gap between these two pieces of lenses, an image point in the vertical direction is made to coincide with the image point in the horizontal direction. Further, by that a lens attaching surface of at least either one side between a second holder 7 or a third holder 9 is worked obliquely, and at least either one side between the second lens 6a or the third lens 8a is attached obliquely to the surface vertical to the optical axis, the light is made incident efficiently on an obliquely ground optical fiber end surface.

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 in which an optical element having a waveguide and an optical fiber are coupled via a lens.

[0002]

2. Description of the Related Art FIGS. 3 and 4 are a vertical sectional view and a horizontal sectional view of a beam shaping lens used in a conventional optical device module shown in, for example, the 1993 Autumn Meeting of the Institute of Electronics, Information and Communication Engineers C-116. 1 is a first lens for collimating light emitted from a semiconductor laser diode, 2 is a first holder for fixing the first lens 1, and 3 is a first surface for collecting a vertical beam, A second lens for converging a horizontal beam on the second surface, 4 is a second holder for fixing the second lens, and 5 is a ray trajectory. Here, the optical element is a semiconductor laser diode that emits light with a wavelength of 0.98 μm at a vertical and horizontal beam emission angles of 3: 1, and the radius of curvature of the first surface of the second lens 3 is 2 of 2.
5 times, the distance between the first surface and the second surface is set so that the focal positions are the same, the end face of the optical fiber is polished to 8 degrees, and then an antireflection film is applied to the semiconductor laser. Preventing reflected light from returning to the diode,
As a result, it is described that a coupling loss of 2.5 dB between the semiconductor laser diode and the optical fiber was obtained. In order to make the light incident on the end face of the optical fiber efficiently, the surface of the first surface or the second surface having no power is arranged obliquely with respect to the surface perpendicular to the optical axis, or another wedge-shaped surface is used. Bending the optical path using a prism, allowing some loss due to mode mismatch between the propagation mode of the optical fiber and the obliquely incident light, or offsetting the semiconductor laser diode from the central axis of the first lens is there. In the conventional example, there is no description about the means for tilting the optical path, but the second
It is difficult to mold the lens by the method of processing the lens 3, the method of adding the wedge-shaped prism increases the number of parts and becomes expensive, and the method of allowing the loss at the end face of the optical fiber and the semiconductor laser The method of offsetting the diode from the central axis of the first lens 1 has an effect such as an increase in coupling loss. Further, in the conventional example, the astigmatic difference occurs due to the change in the distance between the semiconductor laser diode and the first lens 1, the thickness of the second lens 3, and the image point position shift between the first surface and the second surface. For example, if the semiconductor laser diode and the first lens 1 deviate from the optimum position by 5 μm, the coupling loss increases by 0.5 dB, so that precise position adjustment and fixing are required. Although not described in the conventional example, when a commercially available aspherical lens having an NA of about 0.6 is used as the first lens 1, in order to reduce the coupling loss due to the wavefront aberration, a semiconductor laser diode is used. The deviation between the light emitting point and the central axis of the first lens 1 must be about 5 μm. Further, in the case where the first lens 1 and the second lens 3 are fixed in advance, it is necessary to adjust the rotation direction around the optical axis when adjusting the positions of the semiconductor laser diode and the lens group. Therefore, it is necessary to fix the semiconductor laser diode and the first lens 1 with high precision while simultaneously adjusting the optical axis direction, the direction perpendicular to the optical axis, and the rotation direction around the optical axis at the fixing portion. .

[0003]

Since the conventional optical element module is constructed as described above, the first lens 1
The positional deviation between the main surface of the semiconductor laser diode and the semiconductor laser diode in the optical axis direction must be fixed within about ± 5 μm, and if the fixing accuracy is poor, there is a problem such as excessive loss due to astigmatic difference. Further, in the case where the first lens 1 and the second lens 3 are fixed in advance, highly accurate position fixing is required for adjusting the rotation directions of the semiconductor laser diode and the second lens 3. There is a problem that it has to be performed when fixing the semiconductor laser diode and the first lens 1. In addition, the shape of the second lens does not have a rotation target axis, which makes it difficult to process the mold. Further, in order to efficiently enter light into the obliquely polished optical fiber, at least one end surface of the second lens 3 must be inclined with respect to a surface perpendicular to the optical axis, which is processed during molding. However, it is difficult to manufacture the lens. Further, since the first surface and the second surface of the second lens are integrally formed, there is a problem in that variations in the beam shape of the semiconductor laser diode cannot be individually corrected.

The present invention has been made in order to solve the above-mentioned problems, and the accuracy of assembling the first lens with respect to the half element is low, and the cost is low, and the optical element module uses a lens having good workability. The purpose is to provide.

[0005]

An optical element module according to a first aspect of the invention comprises a second lens having a cylindrical surface and a plane for collecting a vertical beam, and a horizontal beam. By arranging a third lens composed of a cylindrical surface and a flat surface with a shift of about 90 degrees around the optical axis and adjusting the distance between these two lenses, an image point in the vertical direction and an image in the horizontal direction can be obtained. It is designed so that points can be matched. Further, at least one lens mounting surface of the second holder or the third holder is processed to be oblique, and at least one of the second lens or the third lens is obliquely mounted to a surface perpendicular to the optical axis. Thus, the light can be efficiently incident on the obliquely polished end surface of the optical fiber.

The optical element module according to the second aspect of the present invention further includes a second lens having a spherical surface and a flat surface for converging the vertical beam and the horizontal beam, and the horizontal beam. A third lens including a light-emitting cylindrical surface and a flat surface is provided, and the vertical image point and the horizontal image point can be matched by adjusting the distance between the two lenses. It was done like this. further,
By processing at least one lens mounting surface of the second holder or the third holder at an angle and mounting at least one of the second lens or the third lens at an angle, it is possible to improve efficiency on the end surface of the optical fiber that is obliquely polished. It is designed so that light can be incident well.

In the optical element module according to the third aspect of the invention, by rotating at least one of the second lens or the third lens and the optical element about the optical axis,
The lateral magnification in the vertical direction and the lateral magnification in the horizontal direction can be set for each individual semiconductor laser diode.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. Embodiment 1 of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a focal length of 0.7 mm for collimating the emitted light of the semiconductor laser diode, N
A0.6, wavefront aberration is about 0.03 wavelength RMS, a first lens formed by aspherical molding of extra-weight flint glass having a refractive index of 1.89, and 2 is a first holder for fixing the first lens 1. , 6a has a vertical focal length of 2.6 mm and is composed of a semi-cylindrical surface and a flat surface having no power in the horizontal direction, and is manufactured by polishing tantalum flint glass having a refractive index of 1.78, First with the cylindrical surface as the first lens 1 side
Second lens disposed at a substantially confocal position with the lens 1 of the above, 7 is a second holder for fixing the second lens 6a, 8
a is a shape having a semi-cylindrical surface and a flat surface with a horizontal focal length of 1 mm and no power in the vertical direction, and is manufactured by polishing tantalum flint glass having a refractive index of 1.78, A third lens arranged as the optical fiber side, 9 is a third holder for fixing the third lens 8a, 1
Reference numeral 0 is a fourth holder into which the third holder 9 is press fitted.
The second lens 6a and the third lens 8a are first manufactured by polishing a cylindrical rod shape, then by polishing a flat surface, and then dicing with a required length, and are manufactured by a simple process.
Here, the reason why the direction of the cylindrical surface of the second lens 6a is set to the first lens 1 side is that the wavefront aberration is made small, and an optical isolator or 1. 5
This is because it is possible to dispose an optical filter that selectively reflects light of 5 μm. The reason why the cylindrical surface of the third lens 8a is on the optical fiber side is to widen the position adjustment range of the optical fiber.

Next, the optical coupling between the semiconductor laser diode and the optical fiber will be described in detail. Since the semiconductor laser diode arranged on the object surface has a spot size diameter of about 1.4 μm in the vertical direction and about 5.2 μm in the horizontal direction and a mode field diameter of the optical fiber of 6 μm, the lateral magnification in the vertical direction is 4. It is sufficient to design a lens system having a magnification of 3 times and a horizontal magnification of 1.2 times. Actually, the spot size of the semiconductor laser diode varies considerably, so the lateral magnification is a design guide. First, since the focal length of the first lens 1 is 0.7 mm, it is clear that the focal length of the second lens 6a should be 3 mm and the focal length of the third lens 8a should be 0.8 mm. However, since the diameter of the cylinder that can be processed by the polishing apparatus is about 1.6 mm, and the refractive index of tantalum flint glass that is relatively easily available is 1.78, the horizontal focal length was set to 1 mm. Further, the first lens 1 has NA 0.6, wavefront aberration 0.03 wavelength R
Since the MS aspherical molded lens is used and the second lens 6a and the third lens 8a are both made of glass having a high refractive index, the wavefront aberration of the entire lens system is sufficiently small, and the kick loss in the lens is lost. Is also small enough. Moreover, since the astigmatic difference of the semiconductor laser diode itself is as small as 1 μm or less, the amount of deviation of the distance between the semiconductor laser diode and the main surface of the first lens 1 from the focal length of the first lens 1 is the main astigmatic difference. Cause Here, the semiconductor laser diode is fixed to the mechanical component by soldering, and the positional accuracy with respect to the mechanical component is about ± 50 μm. Therefore, a holder for inserting the outside of the first holder 2 is provided, and the insertion allowance is adjusted to adjust the positions of the semiconductor laser diode and the first lens 1. It becomes ± 20 μm. Therefore, the deviation between the image point in the vertical direction and the image point in the horizontal direction is ± 400 μm, but the third holder 9 for fixing the third lens 8a is moved to the fourth position.
It suffices if the image point positions are aligned by sliding and adjusting in the holder 10, and the assembling accuracy is about 4 times lower than that of the conventional semiconductor element module, and the assembling is easy. Further, the average coupling efficiency of 1.5 dB is obtained as an experimental value. However, in this lens system, the image points when the first lens 6 and the second lens 8 are assembled form an elliptical image that is long in the horizontal direction, and an optical fiber is used to form the second lens. It is difficult to adjust the position of, and it is necessary to assemble while observing the beam using a TV camera.

Embodiment 2 Hereinafter, a second embodiment of the present invention will be described. In FIG. 2, 6b has a focal length of 2.6 mm, is composed of a spherical surface and a flat surface, and has a refractive index of 1.78.
The second lens 8b, which is manufactured by polishing tantalum flint glass of No. 1 and has a spherical surface on the side of the first lens 1 and at a substantially confocal position with the first lens 1, 8b has a horizontal focal length of 1. It is a third lens which is made of a tantalum flint glass having a refractive index of 1.78 and having a cylindrical surface and a flat surface with a power of 3 mm and having no power in the vertical direction, and the cylindrical surface is arranged on the optical fiber side. The others are the same as or similar to those in the first embodiment. Here, since the second lens 6b is a convex flat lens, the beam is converged in both the vertical direction and the horizontal direction in the assembly of the second lens 6b, and an optical fiber is used although the astigmatic difference is large. Both the alignment method and the alignment method using a TV camera will be in an extremely easy-to-adjust state. In addition, the horizontal power is the second lens 6b and the third lens 8b.
Since the third lens 8b is divided into and, the radius of curvature of the third lens 8b can be increased, and lens processing is simplified.

Embodiment 3 Hereinafter, a method of changing the lateral magnification according to the variation in the spot system of the semiconductor laser diode element in the first or second embodiment of the present invention will be described. For example, in FIG. 1, if the second lens 6a is rotated around the optical axis after fixing the semiconductor laser diode and the first lens 1, the power in the vertical direction decreases corresponding to the cosine of the rotation angle.
On the other hand, in the horizontal direction, the power obtained by multiplying the power of the second lens 6a by the sine of the rotation angle and the power of the third lens 8a is used. Therefore, the horizontal magnification in the vertical direction decreases and the horizontal magnification in the horizontal direction increases. Similarly, the third lens 8
When a is rotated around the optical axis, the horizontal power decreases in accordance with the cosine of the rotation angle. On the other hand, in the vertical direction, the combined power of the power of the second lens 6a and the power of the third lens 8a is multiplied by the sine of the rotation angle. Therefore, the horizontal magnification in the vertical direction increases and the horizontal magnification in the horizontal direction decreases. That is, if the second lens 6a and the third lens 8a are rotated around the optical axis, the vertical lateral magnification and the horizontal lateral magnification can be changed.

Embodiment 4 Hereinafter, in the first or second embodiment of the present invention, the optical fiber prevents reflected return light from the end face from returning to the semiconductor laser diode, and has a wavelength of 1.55 μm incident from the optical fiber side.
A method of preventing the signal light of m from being reflected back to the optical fiber side will be described. For example, in FIG. 1, the end face of an optical fiber having an NA of 0.14 is often polished to about 12 degrees. Therefore, in order to prevent the light of the semiconductor laser diode from being efficiently incident on the optical fiber terminal and prevent the reflected return light from returning to the semiconductor laser diode from the planes of the second lens 6a and the third lens 8a. Means that the second lens 6a is tilted vertically by 5 degrees with respect to the plane perpendicular to the optical axis, the third lens 8a is tilted horizontally by 5 degrees with respect to the plane perpendicular to the optical axis, and the optical fiber terminal is The polishing direction may be rotated 45 degrees around the optical axis. Since the semiconductor laser diode is arranged on the optical axis in FIG. 1, the chief ray of the first lens 1 is refracted according to Snell's law on each surface, and as a result, is finally refracted at the end of the optical fiber. It may be arranged so as to coincide with the central axis of.

Embodiment 5 Further, in the first embodiment, the example in which the cylindrical surface of the second lens 6a is directed to the first lens 1 side is shown, but it is better to set the cylindrical surface of the second lens 6a to the third lens 8a side. Second lens 6a and third lens 8
It is possible to widen the distance from a and allow a margin to the mechanical design of the holder, and it is possible to expect the same effect as that of the above embodiment.

Embodiment 6 FIG. Further, in the second embodiment, an example in which the spherical surface of the second lens 6b is directed to the first lens 1 side is shown, but the spherical surface of the second lens 6b is changed to the third lens 8b.
On the side, the space between the second lens 6b and the third lens 8b can be widened, and the mechanical design of the holder can be afforded, and the same effect as that of the above embodiment can be expected.

Embodiment 7 Further, in the first and second embodiments, the example in which the cylindrical surface of the third lens 8a, 8b is directed to the optical fiber side is shown, but the third lens 8a,
The cylindrical surface of 8b can be expected to have smaller wavefront aberration and spherical aberration and slightly improved coupling efficiency when it is directed toward the second lenses 6a and 6b, and the same effect as that of the above-described embodiment can be expected.

Embodiment 8 Further, although the semiconductor laser diode having a wavelength of 0.98 μm is mounted in the first and second embodiments, any optical element having a waveguide may be used, and it is manufactured by diffusing titanium into lithium niopate. The same effect can be expected by coupling the external modulator with the optical fiber, or coupling the end-face incident type photodiode with the optical fiber.

[0017]

According to the first aspect of the invention, since the distance between the second lens and the third lens can be adjusted, the astigmatic difference of the element having the waveguide and the element and the first lens can be adjusted. By adjusting the distance between the second lens and the third lens, the astigmatic difference due to the axis shift in the direction of the optical axis is adjusted so that the image point in the vertical direction and the image point in the horizontal direction coincide with each other to achieve high optical coupling. Since the second lens and the third lens can be obtained, and the shapes of the second lens and the third lens are easy to manufacture, there is an effect that an inexpensive lens can be obtained.

According to the second aspect of the invention, the distance between the second lens and the third lens can be adjusted.
By adjusting the distance between the second lens and the third lens in the vertical direction, the astigmatic difference of the element having the waveguide and the astigmatic difference due to the axial deviation of the element and the first lens in the optical axis direction can be adjusted. A high optical coupling can be obtained by matching the image point and the image point in the horizontal direction, and the second lens and the third lens have shapes that are easy to manufacture, so that an inexpensive one can be obtained. In addition, since the light emitted from the second lens is converged,
The lens position adjustment is simple, and since the horizontal power is divided into the second lens and the third lens, the radius of curvature of the third lens can be increased, and the lens can be easily manufactured. There is an effect.

According to the third aspect of the invention, since at least one of the second lens and the third lens is rotated around the optical axis with respect to the optical element, the optical waveguide of each optical element is rotated. There is an effect that the lateral magnification in the vertical direction or in the horizontal direction can be adjusted against the variation of 1 to reduce the mode matching loss between the focused beam and the optical fiber at the image point.

According to the fourth invention, at least one of the second lens and the third lens is arranged obliquely with respect to a plane perpendicular to the optical axis, and the end face of the optical fiber is oblique. Therefore, there is an effect that light can be efficiently incident on the optical fiber.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of an optical element module according to a first embodiment of the present invention.

FIG. 2 is a horizontal sectional side view of the optical element module according to the first embodiment of the present invention.

FIG. 3 is a vertical sectional side view of an optical element module according to a second embodiment of the present invention.

FIG. 4 is a horizontal sectional side view of an optical element module according to a second embodiment of the present invention.

FIG. 5 is a vertical sectional side view of a conventional optical element module.

FIG. 6 is a horizontal sectional side view of a conventional optical element module.

[Explanation of symbols]

1 first lens, 2 first holder, 5 ray trajectory,
6a 2nd lens, 6b 2nd lens, 7 2nd holder, 8a 3rd lens, 8b 3rd lens, 9
Third holder, 10th fourth holder.

Claims (4)

[Claims] 1. An optical element having a waveguide, a first lens arranged to face the optical element, and a second lens arranged to face the first lens and having a cylindrical surface and a flat surface. A lens, a third lens formed by rotating the optical axis about the optical axis by about 90 degrees and formed of a cylindrical surface and a plane, and an optical fiber arranged opposite to the third lens. Optical element module. 2. An optical element having a waveguide, a first lens arranged to face the optical element, and a second lens arranged to face the first lens and having a spherical surface and a flat surface. An optical element module comprising: a third lens, which is arranged so as to face the second lens and has a cylindrical surface and a flat surface, and an optical fiber, which is arranged so as to face the third lens. 3. The optical element according to claim 1, wherein the lens having a cylindrical surface is rotated around the optical axis with respect to the waveguide of the optical element so that the lateral magnification can be adjusted. module. 4. The plane of the second lens or the plane of the third lens is arranged so as to be inclined from the plane perpendicular to the optical axis, and the end face of the optical fiber is obliquely polished. The optical element module according to claim 1.