JPH04116507A - Array laser module - Google Patents

Abstract

PURPOSE:To obtain the inexpensive array laser module by arranging a lens array, optical isolator and condenser lens in this order from the side of a semiconductor array laser. CONSTITUTION:A lens array 20, optical isolator 30 and condenser lens 40 are arranged in this order from the side of a semiconductor array laser 10. In this case, for beams generated by all the laser elements 101-10n and transmitted through the lens array 20, the diameter is almost equal to the integration range of the laser elements. Therefore, a size almost equal to the integration range of the laser elements is enough for the opening diameter of the optical isolator 30 as well, and even when the integration range is enlarged, the limit of the integration range due to the opening diameter of the optical isolator 30 is relaxed. Next, the real image of the optical output of the laser element 101 by the lens 201 is transformed with power by the lens 40 and condensed on the end face of an optical fiber 50n. Thus, the inexpensive array laser module can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an array laser module that couples the optical output of a semiconductor array laser to a fiber array.

<Prior art> As an array laser module, for example, the Institute of Electronics, Information and Communication Engineers Optical Communication System Study Group Material No. 0SC89-67
(Kaita, Sa0; Optical FDM using r'y ray laser
"Study of Transmission Circuits for Transmission", Materials of the Optical Communication System Study Group,
1990. A configuration as described in pp. 35-40) has been proposed.

FIG. 2 is a diagram showing a 7-ray laser module having a conventional configuration according to the above-mentioned document. In FIG. 2, 10 is a semiconductor array laser, which has a configuration in which 101 to 10n laser elements are integrated at equal intervals, and each laser element 101 to Ion
each outputs light independently. 401 is the first lens (
With a focal length fiF1), the optical outputs of the laser elements 101 to Ion are collectively converted into parallel light beams. Reference numeral 30 denotes an optical isolator, which is arranged so as to transmit only the light incident from the first lens 401 side, and prevents characteristic deterioration of the laser element due to reflected return light. 402 is the second lens (focal length gllF2
), the optical outputs of the laser elements 101 to 10n are individually focused. 50 is a fiber array, and optical fibers 501 to 5
0n are arranged at equal intervals, and the semiconductor array laser 10
The independent laser elements 101 to 10n (correspondingly, the individual optical fibers 50n to 501 are connected to each other in a positional relationship such that the distance between each optical fiber 501 to 50n of the fiber array 50 is 1. The distance between the laser elements 101 to Ion is multiplied by the magnification of the optical system determined by the second lenses 401 and 402.

In addition, each component is arranged in a confocal system in order to increase the tolerance due to positional deviation of each component, for example, the position M error of the lenses 401 and 402 with respect to the array laser 10.
The distance between the semiconductor array laser 10 and the first lens 401 is Fl, and the distance between the two lenses 401 and 402 is F1+
F2, the distance between the second lens 402 and the fiber array 50 is F2.

The path by which the optical output of the laser element is coupled to the optical fiber in such a configuration will be explained by taking the laser element 101 as an example. First, the optical output of the laser element 101 is converted into parallel light by the lens 401. This parallel ray is the central axis of the optical system (
(hereinafter referred to as the optical axis).

This is because the laser element 101 is placed away from the optical axis, which is also the center of the first lens 401, as shown in FIG.
The angle θ of the optical path according to 1 is expressed as θ=arctan (L/F1), where L is the distance from the optical axis of the laser element. Next, this parallel light beam enters and passes through the optical isolator 30, and is focused by the lens 402 only on the end face of the optical fiber 50n, and is coupled therewith. Good optical coupling can be obtained by converting the focused beam diameter at this time to match the beam diameter of the optical fiber.

As an example, as the beam diameter conversion magnification (F2/Fl),
For example, if the oscillation wavelength of the laser element is in the 1.55 μm band,
Since the beam diameter of the laser element is about 2 to 2.5 μm and the beam diameter of the optical fiber is about 10 μm, it is preferable to increase the diameter by 4 to 5 times.

In this conventional example, when the laser element is arranged at a position of ±200 μm from the optical axis, the first lens 401 has a focal length aF1 of about 611Iff1, and the second lens 402 has a focal length of about 24 mm.

Furthermore, in order to efficiently convert the optical output of a laser element placed away from the optical axis, a lens with a long focal length and large diameter is used, which is less affected by lens aberration. In this way, the optical output of the laser element 101 placed at the upper end of the semiconductor array laser 10 is coupled to the optical fiber 50n placed at the lower end of the fiber array 50 and output. Similarly, the optical output of the laser element 102 is coupled to the optical fiber 50n-1, and the optical output of the laser element 10n is coupled to the optical fiber 501.
is combined with and output. At this time, the optical fiber 501~
The interval of 50n is about 4 to 5 times the interval between laser elements.

In this way, the array laser module of this conventional example uses a large-diameter lens with little lens aberration, long focal length, and converts the optical output of all laser elements at once to a beam diameter of 4. It was coupled with low loss to optical fibers arranged at ~5 times the spacing. Furthermore, an optical isolator having a size comparable to the lens aperture is placed between the lenses to prevent variations in the characteristics of the laser element due to reflected return light.

FIG. 3 is a diagram showing another conventional example of an array laser module. Components that are the same as those in FIG. 2 are designated by the same reference numerals. That is, 10 is a semiconductor array laser, 101 to Io
n is a laser element, 50 is a fiber array, 501A+5
On is an optical fiber. Differences from the conventional example shown in FIG. 2 include the optical isolator 30 and lens 401 shown in FIG.
, 402, the spacing between the optical fibers is the same as the spacing between the laser elements, and a lens array 20 is provided, in which microlenses 201 to 2 (ln) are integrated at the same spacing as the laser elements.

With such a configuration, in this conventional example, each laser element 101 to 1
The optical output of 0n is obtained from the microlenses 201 to 201 of the lens array 20.
The beam diameter is converted by passing through each of the optical fibers 501 to 50n and directly coupled to each of the optical fibers 501 to 50n. The conversion magnification at this time is (b/a), where a is the distance between the laser element and the lens, and b is the distance between the lens and the optical fiber.

In this way, in this conventional example, the beam diameter is converted using small lenses lined up at the same spacing as the laser element, so each optical fiber can also be placed at the same spacing as the laser element, making it possible to construct a compact modular. reactor. Furthermore, since the laser elements and optical fibers are individually coupled, the structure can be adapted even when the number of laser elements increases.

<Problems to be Solved by the Invention> However, in the conventional example shown in Fig. 2, the optical output of multiple laser elements is converted at once by a lens, which increases the number of laser elements to be integrated, making it difficult to integrate them. As the field of view becomes larger, a lens with a wider field of view and larger aperture is required. For example, when laser elements are integrated in a range of about 400 μm, a lens with an aperture of 8 mm is used, which is several tens of times larger than the integrated range of laser elements. Therefore, as the integration increases, the lenses become larger and the entire module becomes larger and more expensive.

Furthermore, as the lenses become larger, the beam diameter between the lenses also becomes as large as the lens aperture, so it is necessary to increase the diameter of the optical isolator as well. However, large-diameter optical isolators are expensive, and due to limitations in their component parts, currently only optical isolators with a diameter of about 10m+n can be produced.
The integration range of laser devices will be limited.

As a result, in the conventional example shown in Fig. 2, as the number of laser elements increases, the optical system and the entire module become larger and more expensive, and even if this increase in size is allowed to some extent, the integration of laser elements is limited by the optical isolator. There was a problem that the range was limited.

Further, in the conventional example shown in FIG. 3, the laser elements 101 to 10.
Since the optical output of the laser element is individually coupled to the optical fiber arranged at the same interval by the small lenses 201 to 2On arranged at the same interval as n, each component can be integrated within the same range as the laser element's integration range. The size is sufficient, and the module can be made smaller.

However, when laser elements are integrated at high density,
The aperture of the lens decreases with the distance between the laser elements. In this case, in order to capture the necessary amount of laser light into the lens, the distance between the laser array 10 and the fiber array 50 must be made small, and good optical coupling cannot be obtained. For example, when laser elements are integrated at intervals of 100 μm, the distance between the laser array 10 and the fiber array 50 is approximately 600 μm to obtain optimal coupling. For this reason, there was a problem in that a sufficient length was not available to insert the optical isolator, and the optical isolator could not actually be inserted. Furthermore, since the laser element and the optical fiber are coupled using only one lens with a small focal length, there is also a drawback that the tolerance for misalignment of each component is small and manufacturing is difficult.

Means for Solving the Problems> The present invention achieves the above-mentioned object by using a fiber array configured by optical fibers mounted on the same as the laser elements to transmit the optical output of a semiconductor array laser in which a plurality of laser elements are integrated. An array laser module that couples and outputs a laser beam, wherein between the semiconductor array laser and the fiber array, there is provided a lens array consisting of a plurality of lenses arranged at the same distance as the laser element, and a lens array from the lens array side. an optical isolator arranged to transmit only incident light; and 1 for condensing the optical output of the laser element transmitted through the optical eye router onto the end face of each optical fiber of the fiber array.
and a condensing lens constituted by one or more lenses, and the lens array, the optical isolator, and the condensing lens are arranged in this order from the semiconductor array laser side.

According to the present invention, each optical output of each laser element integrated into a semiconductor array laser is converted to an arbitrary size by the lens array, while keeping the distance between the beams the same. and passes through the optical isolator. This transmitted light is condensed by one or more lenses, and the beam diameter is converted to minimize the coupling loss with the optical fibers, and the light is condensed into each corresponding optical fiber. Be combined.

Example of implementation The present invention will now be described in detail with reference to FIG.

FIG. 1 is a configuration diagram showing an embodiment of an array laser module. Note that the same components as in FIGS. 2 and 3 are represented by the same reference numerals. That is, 10 is a semiconductor array laser, in which laser elements 101 to 10n are integrated at equal intervals, and each can be independently controlled by changing the injection current. As an example of such a semiconductor array laser,
An example of integrating 20 distributed feedback (DFB) lasers at 125 μm intervals has been reported (M, Nakao e.
tal; “1.55μmDFB La5er
array with ^/4-5hifted fi
rstorder grating fabric
ed by X-Ray lithography
”Electron, Lett,, 1989, vol.
25. pp. 148-149).

Reference numeral 20 denotes a lens array, in which lenses 20] to 20n are integrated at the same spacing as the laser elements, and individually converts the beam diameter of the optical output of the laser elements. As such a lens array 20, there is a distributed refractive index type planar microphone lens (M, Oikawa and K, Iga;
lied 0ptics, vo121, Pp, 1
052-1056.1982). This lens array 2
0 uses LSI's batten forming technology to manufacture lenses, making it possible to manufacture small lenses with high precision. Reference numeral 30 denotes an optical isolator, which is arranged so as to transmit only the light incident from the lens array 20 side, and allows the light that has passed through the lens array 20 to pass all at once. 40 is a condensing lens, for example, a first lens 401 that converts the real images of the laser elements 101 to Ions formed by the lens array 20 into parallel rays, and a second lens 4 that individually condenses the parallel rays.
Consists of 02. 50 is a fiber array, 50
It has 1 to 50 nm of optical fibers, and the spacing between them is equal to the magnification of the condenser lens 40 multiplied by the laser element spacing.

Based on the configuration in which the lens array 20, the optical isolator 30, and the condensing lens 40 are arranged in this order, the path by which the optical output of the laser element is coupled to the optical fiber will be explained using the laser element 101 as an example.

The optical output of the laser element 101 is received by the lens 201 of the lens array 20, subjected to beam diameter conversion, and sent to the lens 2.
A real image is formed on the output side of 01. The distance b (image point) between the real image and the lens 201 at this time is expressed as follows.

1/b=1/F, -1/a where a is the semiconductor array laser 10 and the lens array 2
The interval (object point) of 0, F, 1 is the focal length of the lens 201. Also, the conversion magnification of the beam diameter at this time is (b/a
). For example, in the case of the above-mentioned planar microlens, if the lens aperture is 100 μm, the focal length is 230 μm.
m, and if the conversion magnification is 2x, a=350 pm1b
=700 μm.

The output of lens 201 then passes through optical isolator 30 . The aperture of the optical isolator 30 at this time is determined by the beam diameter of the optical output of all the laser elements output from the lens array 20. In this configuration, the optical output is converted individually using lenses arranged at the same distance as the laser element.
The beam spacing remains the same as that of the laser elements, and the beam diameter of all the laser elements transmitted through the lens array 20 becomes approximately the same size as the integrated range of the laser elements.

Therefore, the aperture of the optical isolator 30 only needs to be about the same size as the integration range of the laser elements, and even if the integration range is increased, the restriction on the integration range by the aperture of the optical isolator 30 is eased.

Next, the real image of the optical output of the laser element 101 by the lens 201 is magnified by the lens 40 and focused on the end face of the optical fiber 50n.

At this time, by appropriately adjusting the focal length of the first lens 401 of the lens 40 (m1EI), the distance between the lens array 20 and the first lens 401 is adjusted appropriately, and the length for arranging the optical isolator 30 is secured. I'll come. In addition, a real image of the laser element, two lenses 401 and 402, and a phino
The array 50 is placed in a confocal arrangement, that is, the distance between the real image of the laser element and the collimating lens 401 is Fl, the distance between the two lenses is (F1 + F2), and the focal length of the condensing lens 402 is F1.
If it is set to 2, the tolerance for positional deviation of each component will be relaxed (Here, Fl and F2i are the focal lengths of the collimating lens 401 and the condensing lens 402, respectively). The conversion magnification of the beam diameter at this time is (F2/Fl)
Therefore, the entire beam diameter conversion magnification ζ including the lens array 20 is (b/a)X (F 2 /F 1). Therefore, compared to the conventional magnification F 2 / F 1 shown in FIG. 2, the magnification is b / a @, so it is t! In this way, the beam diameter has been converted by the lens 201 of the lens array 20, and the beam is converted again to the optimum magnification by the two lenses, and then the optical fiber 50n can be made smaller. Output to. As shown below, the output of the laser element 102 is coupled to the optical fiber 50n-1, and the optical output of the laser element 10n is coupled to the optical fiber 501 for output.

In this embodiment, the laser element 101 is
Although a case has been described in which a real image of ~Ion is formed, a similar array laser module can be constructed by arranging the lens array 20 so as to form a virtual image of a laser element.

<Effects of the Invention> As explained above, there is an array laser module that couples and outputs the optical output of a semiconductor array laser in which a plurality of laser elements are integrated to a fiber array composed of the same number of optical fibers as the laser elements. a lens array in which lenses are arranged between the semiconductor array laser and the fiber array at the same intervals as the laser elements, and an optical isolator arranged to transmit only light incident from the lens array side. , a condenser lens constituted by one or more lenses for condensing the optical output of the laser element transmitted through the optical isolator onto the end face of each optical fiber of the fiber array, from the semiconductor array laser side. , the lens array, the optical isolator, and the condensing lens are arranged in this order, and each lens of the lens array converts only the beam diameter of each optical output of the laser element, and converts a real image or a light beam at the same interval as the laser element. forming a virtual image; the optical isolator passes the output of the lens array all at once;
Since the optical isolators are individually coupled to each optical fiber, the aperture of the optical isolator can be made to be approximately the same size as the integration range of the laser elements, thereby eliminating the limitation of the integration range of the laser elements due to the size of the optical isolator. This has the advantage of being able to provide an inexpensive play laser module because it can be relaxed and a small-diameter optical isolator can be used.

Furthermore, since the output of the laser element is condensed by the lens, there is an advantage that the tolerance for misalignment of each component can be relaxed, and a module that is easy to manufacture can be provided.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the array laser module according to the present invention, FIG. 2 is a diagram showing a conventional example of the array laser module ζ, and FIG. 3 is a diagram showing another conventional example of the array laser module. It is. In the figure, 10 is a semiconductor array laser, 101 to 10n are integrated laser elements, 20 is a lens array, and 201 to 10n are integrated laser elements.
20n is a lens integrated into a lens array, 30 is an optical isolator, 401 is a condenser lens, 401 is a first lens, 402 is a second lens, 50 is a fiber array,
501 to 50n are optical fibers. First Example 50 On the fiber array

Claims (1)

[Scope of Claims] An array laser module that couples and outputs the optical output of a semiconductor array laser in which a plurality of laser elements are integrated to a fiber array composed of the same number of optical fibers as the laser elements, Between the semiconductor array laser and the fiber array, a lens array consisting of a plurality of lenses arranged at the same intervals as the laser element, and an optical isolator arranged so as to transmit only the light incident from the lens array side. , condensing the optical output of the laser element transmitted through the optical isolator onto the end face of each optical fiber of the fiber array;
What is claimed is: 1. An array laser module comprising: a condensing lens constituted by one or more lenses, and the lens array, the optical isolator, and the condensing lens are arranged in this order from the semiconductor array laser side.