JPH04315488A - Laser array module - Google Patents

Abstract

PURPOSE:To realize a laser array module which can be inexpensively and easily manufactured and has high yield of a product. CONSTITUTION:At least one of a light transmission part 6 formed of a material which transmits light outputs laser elements 11-1n, is disposed between a semiconductor laser array 1 and an optical transmission line array 5. The angle of the part 6 to the optical axis of the light transmitting surface is varied to correct a positional deviation of a focal position of the light outputs of the elements 11-1n from the central positions of the array 5, thereby so regulating an optical coupling efficiency as to become maximum.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a laser array module using a semiconductor laser array, and relates to a structure of a laser array module that is easy to manufacture and can obtain highly efficient optical coupling. .

0002

[Prior Art] Conventionally, as a laser array module,
For example, IEICE Optical Communication System Study Group Material No.
．． The configuration described in OSC89-67 (Sekine, Sato; "Study of transmitter circuit for optical FDM transmission using array laser", Optical Communication System Study Group Materials, 1990, pp. 35-40) was proposed. There is.

FIG. 2 shows this conventional laser array module.
FIG. 2 is a diagram showing an example of the configuration of a file. In FIG. 2, 1 is a semiconductor laser array chip (hereinafter abbreviated as laser array).
Four laser elements 11, 12, 13, and 14 are integrated at equal intervals, and each outputs light independently. 2 is the first
A lens that transmits the optical output of the laser elements 11 to 14 all at once.Although it may be composed of a single lens, it is a combination lens that uses multiple lenses to eliminate aberrations. It may also be configured.

Reference numeral 3 denotes an optical isolator, which is arranged so as to transmit only the light incident from the first lens 2 side, and prevents characteristic deterioration of the laser element due to reflected return light. Note that some modules with a simpler configuration are not equipped with the optical isolator 3. 4 is the second lens, which is an optical isolator.
The optical outputs of the laser elements 11 to 14 that have passed through the laser sensor 3 are individually focused. As with the first lens 2, this second lens 4 may be composed of a single lens or may be composed of a combination of lenses. 5 is an optical transmission line array, which includes optical fibers 5 as optical transmission lines.
1, 52, 53, and 54 are arranged at equal intervals, and the interval is the distance between the laser elements multiplied by the magnification of the optical system determined by the configuration of the two first and second lenses 2 and 4. It is.

In such a configuration, the light emitting source, that is, the laser array 1 is usually placed at the focal position of the first lens 2, and the optical transmission line array 5 is placed at the focal position of the second lens 4. The tolerance for positional deviation between the first lens 2 and the second lens 4 is increased by making the light beam passing through the first lens 2 parallel.

Next, the path by which the optical output of the laser device is coupled to the optical fiber will be explained using the laser device 11 as an example.

First, the optical output of the laser element 11 is converted into parallel light by the first lens 2. This parallel light ray travels obliquely with respect to the central axis OA of the optical system (a line connecting the centers of the first lens 2 and the second lens 4, hereinafter referred to as the optical axis). This means that the laser element 11 has an optical axis O as shown in FIG.
This is because it is placed away from A. Next, this parallel light beam enters and passes through the optical isolator 3, and is focused and coupled to the center of the core of the optical fiber 54 by the second lens 4.

At this time, in order to obtain good optical coupling, the beam diameter is adjusted to match the beam diameter of the optical fiber.
The diameter is being converted. For example, when the oscillation wavelength of the laser device is in the 1.55 μm band, the beam diameter of the laser device is approximately 2 to 2.5 μm, and the beam diameter of the optical fiber is approximately 2 to 2.5 μm. Since it is about 10 μm, it is better to increase it by 4 to 5 times. Also, the center position of the focused beam (hereinafter referred to as the focused position)
and the center position of the optical fiber core using an optical fine movement table.

In this manner, the optical output of the laser elements 11 of the laser array 1 is transmitted through the optical fibers 5 of the optical transmission line array 5.
4 and output. Hereinafter, the laser element 12
The optical output of the laser element 13 is coupled to the optical fiber 53, the optical output of the laser element 13 is coupled to the optical fiber 52, and the optical output of the laser element 14 is coupled to the optical fiber 51 and output.

0010

[Problems to be Solved by the Invention] As described above, in the conventional laser array module, the beam of the optical output of the laser element is
By matching the beam diameter of the optical fiber with the beam diameter of the optical fiber using a lens system, and by precisely matching the focusing position and the center position of the optical fiber core, the optical coupling between the laser element and the optical fiber is achieved with high efficiency. I was about to go there.

However, in order to obtain highly efficient optical coupling, the misalignment between the light condensing position and the core center of the optical fiber must be
It is necessary to match on the order of m. For example, as shown in FIG. 3, the reduction in coupling efficiency due to this positional shift is reduced to 0.
To achieve within 5dB, adjust the two center positions by ±1.8
It is necessary to match with an accuracy of μm.

[0012] For this reason, when manufacturing conventional modules, accurate positioning of each component is essential, requiring precisely manufactured jigs and expensive positioning equipment, which increases manufacturing costs. As the cost increases, the time required to align each component becomes longer, which has the disadvantage of causing a decrease in productivity.

[0013] Also, due to stress when the optical adhesive used to fix each part dries, the mounting position of the parts may shift,
This method has the drawbacks of lowering the coupling efficiency and lowering the yield and reliability of the product.

The present invention has been made in view of the above circumstances, and its purpose is to provide a laser array module that can be manufactured at low cost and easily, and that can improve product yield. .

[0015]

Means for Solving the Problems In order to achieve the above object, the present invention provides a semiconductor laser array in which a plurality of laser elements are integrated; at least one lens; In the laser array module, the laser element is disposed between the semiconductor laser array and the optical transmission line array, and the laser element is arranged between the semiconductor laser array and the optical transmission line array. at least one light transmitting portion formed of a material that transmits a light output of
The light transmitting portion was arranged such that the light transmitting surface was at a predetermined angle with respect to the optical axis so that the light converging position of the laser element was at a predetermined position.

Further, in a second aspect of the present invention, means is provided for varying the angle of the light transmitting surface of the light transmitting portion with respect to the optical axis.

[0017]

According to claim 1, when the light transmitting portion is fixed, the positional deviation between the condensing position of the laser element and the center position of each of the optical transmission line arrays is corrected, and the optical coupling efficiency is improved. adjusted to the maximum.

Further, in claim 2, by rotating the light transmitting surface of the light transmitting part by an arbitrary angle, the light converging position of the laser element is changed, and the positional deviation from the center position of the optical transmission line array is prevented. is corrected as needed and adjusted so that the optical coupling efficiency is maximized.

[0019]

[Example] Figure 1 shows a laser array module according to the present invention.
FIG. 2 is a configuration diagram showing a first embodiment of the system, and the same components as those in FIG. 2 showing the conventional example are denoted by the same reference numerals.

That is, 1 is a laser array in which n laser elements 11 to 1n are integrated at equal intervals. 2 and 4 are first and second lenses, respectively. These two lenses 2
, 4, as explained in the conventional example section, a single lens may be used, but in order to remove aberrations, a combination lens consisting of multiple lenses may be used. . These first and second lenses 2 and 4
The optical output of each laser element 11 to 1n of the laser array 1 is focused.

Reference numeral 5 denotes an optical transmission line array, in which optical fibers 51 to 5n as optical transmission lines are arranged at equal intervals, and the intervals are determined by the laser element interval and the magnification of the optical system determined by the configuration of the lens system. It is multiplied by As described above, the magnification of the optical system at this time is such that highly efficient optical coupling can be obtained by making the beam diameter of the laser element match the beam diameter of the optical fiber. In the case of a wavelength band of 1.55 μm used in optical communications, 4 to 5 times is appropriate.

Reference numeral 6 denotes a light transmitting plate made of a material that transmits the light output of the laser elements 51 to 5n, and is made of, for example, optical glass, and when this optical glass is used, it can handle light of a wide range of wavelengths. . Also, 1.5 used in optical communication
As the material that transmits light in the 5 μm band, silicon, zirconia oxide, etc. can be used. This light transmitting plate 6 is arranged between the second lens 4 and the optical transmission line array 5, and has a light transmitting surface at a predetermined angle with respect to the optical axis OA. The condensing position of the output light 1n is shifted and fixed so as to accurately match the core center of each optical fiber 51 to 5n for optical coupling.

In such a configuration, the laser array 1 is usually located at the focal length (F1) of the first lens 2, and the optical transmission line array 5 is located at the focal length (F2) of the second lens 4. The lenses are arranged so that the distance between the lenses is the sum of the focal lengths of the first lens 2 and the second lens 4 (F1+F2).

Next, in the above configuration, the path by which the optical output of the laser element is coupled to the optical fiber will be explained using the laser element 11 as an example.

The optical output of the laser element 11 is converted into a parallel beam by the first lens 2 and condensed by the second lens 4. The light focused by the second lens 4 then enters the light transmitting plate 6, where the light focusing position is shifted in parallel.

FIG. 4 is an explanatory diagram of this shift of the focusing position. In FIG. 4, the optical output of the laser element 11 output from the second lens 4 is a light beam RL1, and the optical axis OA
The direction is the Z-axis, and the direction perpendicular to it is the X-axis.

The light ray RL1 is outputted from the second lens 4 in a direction parallel to the Z-axis and inputted into the light transmitting plate 6. At this time, since the light transmitting surface of the light transmitting plate 6 is inclined by θ with respect to the optical axis (Z axis) OA, the traveling direction of the light ray RL1 changes according to Snell's law of refraction. The angle at this time, as shown in FIG. 4, is expressed by the following equation, where δ is the angle of the light ray RL1 with respect to the perpendicular to the surface of the light transmitting plate 6.

[0028] sin δ=n0・sin
θ/n1
...(1) However, n0 is the refractive index of air, and n1 is the refractive index of the light transmitting plate 6, which is 1.5 when optical glass is used.

In this way, the light ray RL1 passes through the light transmitting plate 6.
The light travels inside the glass diagonally at an angle of (θ - δ) with respect to the Z axis, and a similar refraction occurs on the back surface of the glass plate, causing the light to travel in the same direction as when it entered, that is, in a direction parallel to the Z axis. It emits light. Therefore, the focusing position of the light beam RL1 is shifted by ΔX on the X-axis. This shift amount ΔX is expressed by the following equation (2).

ΔX={T・sin (θ−
δ)}/cos δ…(
2) However, T is the thickness of the light transmitting plate 6, and δ is the value shown in equation (1).

FIG. 5 is a diagram showing the relationship between the inclination of the light transmitting plate 6 and the shift amount of the light condensing position, which was determined from the above equation (2). FIG. 5 shows a case where optical glass is used as the light transmitting plate 6, where the horizontal axis represents the inclination of the optical glass plate, and the vertical axis represents the shift amount of the light condensing position.

As can be seen from FIG. 5, by changing the inclination of the light transmitting plate 6, the light condensing position can be adjusted in the μm order in the direction parallel to the X axis. Further, by changing the thickness T of the light transmitting plate 6, the adjustment range can be arbitrarily selected. Here, we have explained the case where the light transmitting plate 6 is tilted on the X-Z plane, but if it is tilted within the Y-Z plane (the Y-axis is an axis perpendicular to the plane of paper in FIG. 4), it can be tilted in a direction parallel to the Y-axis. It is also possible to adjust the focusing position of the laser element, and the focusing position of the laser element can be freely adjusted within the X-Y plane.

By adjusting and fixing the inclination of the light transmitting plate 6 in this manner, the focusing position of the laser element 11 can be shifted to accurately align with the core center of the optical fiber 5n to perform optical coupling. be able to. Other laser elements 12 to 1n
Also, as shown in FIG. 4, the focusing position is shifted by the same amount as the light ray RL1 (here, the light ray n output from the laser element 1n is illustrated as an example).

Note that since the laser elements 11 to 1n and the optical fibers 51 to 5n are arranged on a straight line, the focusing position of the output of the laser element 11 (light ray RL1) and the output of the laser element 1n (light ray RLn) is If the light transmitting plate 6 is fixed so as to match the core center of each optical fiber 5n and 51, the focusing position of the output from the other laser elements 12 to 1 (n-1) will also be automatically adjusted to each optical fiber. 5(n-1)~5
It coincides with the core center of 2.

As explained above, according to the first embodiment, the second lens 4 for condensing the output light of each laser element 11 to 1n of the laser array 1 and the optical transmission line array 5 are A light transmitting plate 6 made of a material that transmits the light output of the laser element is placed between the two, and the light transmitting plate 6 is aligned with the optical axis OA so that the light output of the laser element is focused at a predetermined position. Since the light transmitting plate 6 is fixed at a predetermined inclination, the shift between the focusing position of the optical output of the laser element and the center position of the optical transmission line due to the positional shift of the optical components during module manufacturing can be avoided on the order of μm when the light transmitting plate 6 is fixed and bonded. can be corrected and matched, easily obtains highly efficient optical coupling, eliminates the need for expensive alignment equipment during manufacturing, and reduces the time required to align each optical component. This has the advantage of providing a laser array module that is inexpensive and easy to manufacture.

Furthermore, positional deviations of components due to stress during drying of the adhesive used for bonding optical components can be corrected when fixing the light transmitting plate, and product yield can be improved.

FIG. 6 is a block diagram showing a second embodiment of the laser array module according to the present invention.

The difference between the second embodiment and the first embodiment is that between the second lens 4 and the optical transmission line array 5,
First and second light transmitting plates 6 made of optical glass, for example.
, 7 are arranged in tandem, and each light transmitting plate 6, 7 is provided with a rotating shaft 61, 71, respectively.
1 around the Y axis, the first light transmitting plate 6 is tilted in the X-Z plane, and by rotating the rotating shaft 71 around the X axis, the second light transmitting plate 7 is tilted. Y-
It is configured to be tilted within the Z plane so that the amount of shift of the condensing position can be adjusted arbitrarily.

Next, the laser elements 11 to 1n and the optical fibers 5n to 51 of the optical transmission line array 5 in such a configuration
Let us explain the optical coupling with.

As described above, the optical outputs of the laser elements 11 to 1n pass through the first and second lenses 2 and 4. The light output that has passed through the second lens 4 has its condensing position shifted by the first light transmitting plate 6 in the X-axis direction shown in FIG. 6, as described above. At this time, the tilt is adjusted by the rotating shaft 61. The shift amount at this time becomes the value shown by the above-mentioned equation (2). Similarly, the light passing through the first light transmitting plate 6 is transmitted through the second light transmitting plate 6.
The light-converging position is shifted in the Y-axis direction by the light transmitting plate 7 . At this time, the inclination is adjusted by the rotating shaft 71, and the shift amount is arbitrarily adjusted.

In this way, by adjusting the inclinations of the light transmitting plates 6 and 7 at any time, the condensing positions of the optical outputs of the laser elements 11 to 1n are made to coincide with the core centers of the optical fibers 5n to 51, respectively, thereby achieving high efficiency. can perform optical coupling.

As explained above, according to the second embodiment, in addition to the effects of the first embodiment, long-term positional deviations of optical components can be corrected at any time, and long-term reliability is improved. It is possible to realize a laser array module with high performance.

[0043] In the above first and second embodiments,
Although the light transmitting plates 6 and 7 for adjusting the focusing position are arranged between the second lens 4 and the optical transmission line array 5, they may also be arranged between the laser array 1 and the first lens 2. Needless to say. Furthermore, although this embodiment has been described with reference to a module that does not have a built-in optical isolator, as shown in FIG. Of course, a similar configuration can be made.

[0044]

As explained above, according to claim 1, the light transmitting plate prevents the deviation between the focusing position of the optical output of the laser element and the center position of the optical transmission line due to the positional deviation of the optical components during module manufacturing. It is possible to correct and match on the μm order when fixing and bonding, and it is possible to easily obtain highly efficient optical coupling.
This eliminates the need for an expensive alignment device during manufacturing, and also reduces the time required to align each optical component, which has the advantage of providing a laser array module that is inexpensive and easy to manufacture.

[0045] Moreover, positional deviations of components due to stress during drying of the adhesive used for bonding optical components can be corrected when fixing the light transmitting plate, and product yield can be improved.

Furthermore, according to the second aspect of the present invention, long-term positional deviations of optical components can be corrected at any time, and a laser array module with high long-term reliability can be realized.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a laser array module according to the present invention.

FIG. 2 is a configuration diagram showing a conventional laser array module.

FIG. 3 is a diagram showing the relationship between positional shift amount and coupling efficiency.

FIG. 4 is an explanatory diagram of a shift of a light condensing position by a light transmitting plate.

FIG. 5 is a diagram showing the relationship between the inclination of the optical glass plate and the shift amount of the condensing position.

FIG. 6 is a configuration diagram showing a second embodiment of the laser array module according to the present invention.

[Explanation of symbols]

1...Semiconductor laser array 11-1n... integrated laser element 2...First lens 4...Second lens 5...Optical transmission line array 51~5n...Optical fiber (optical transmission line) 6, 7...Light transmission plate 61, 71...Rotation axis of light transmitting plates 6, 7

Claims (2)

[Claims] 1. An optical transmission system comprising a semiconductor laser array in which a plurality of laser elements are integrated, at least one lens, and an optical transmission line each optically coupled to the laser element by the lens. In the laser array module, at least one light transmitting part formed of a material that transmits the optical output of the laser element is provided between the semiconductor laser array and the optical transmission line array. and
A laser array module characterized in that the light transmitting section is arranged with the light transmitting surface at a predetermined angle with respect to the optical axis so that the light converging position of the laser element is at a predetermined position. 2. The laser array module according to claim 1, further comprising means for varying the angle of the light transmitting surface of the light transmitting section with respect to the optical axis.