JP2003188479A - Semiconductor light amplifier module and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gain clamp type semiconductor light amplifier module capable of reducing a set error or dispersion in gain and a method for manufacturing the module. <P>SOLUTION: A module is constituted by arranging reflectors on respective prescribed positions of input and output optical waveguides to be quartz group plane optical waveguides formed on a substrate and arranging a semiconductor light amplifier between the reflectors. The semiconductor light amplifier module is manufactured by arranging at least one of the reflectors to be arranged on the optical waveguides of the input and output sides is arranged on the prescribed position of the optical waveguide after connecting the amplifier to the I/O optical waveguides. Even when combined loss is changed, the gain variation of the module can be suppressed to a low value and roughly set up to a required value. Since the dispersion of the combined loss between an SOA element and the optical waveguide is small, an array module of which the module gain between channels is extremely uniform can be manufactured. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical amplifier module used for optical communication and optical signal processing, and a method for manufacturing the same, and more particularly, to a gain clamp type semiconductor optical amplifier module with less gain setting error and variation. And a method for manufacturing the same.

[0002]

2. Description of the Related Art A semiconductor optical amplifier (SOA) is being studied for various applications such as a small optical amplifier, a high-speed optical gate switch, and a wavelength conversion element, and is expected as a key device for the sophistication of optical networks. There is.

However, in the conventional SOA, the gain fluctuates depending on the input power and the response speed is higher than that of the fiber type optical amplifier. Therefore, when a plurality of signal lights are input at the same time, the signal lights are different. There are known problems that crosstalk occurs and that the transmission waveform deteriorates due to the modulation pattern of the signal light.

In order to solve these problems, a method called gain clamp has been proposed. This method
A linear amplification operation is obtained by providing reflectors on both sides of the SOA, oscillating at a wavelength different from that of the signal light, and keeping the carrier density constant.

FIG. 4 is a diagram for explaining a configuration example of a gain clamp type SOA element which has been conventionally studied.
The OA element 40 realizes a gain clamp operation by monolithically integrating the regions where the Bragg gratings 42a and 42b are formed on both sides of the SOA active region 41 and coupling them to the optical fibers 43a and 43b.
A desired device gain can be obtained by appropriately designing the reflectances of the Bragg gratings 42a and 42b in advance.

[0006]

However, the structure in which the reflector is integrally integrated with the SOA element as shown in FIG. 4 is not always preferable. This is because there is variation in the coupling loss between the SOA element and the optical fiber, and with such a configuration, the gain of the entire module after mounting the SOA element and the input / output fiber cannot be obtained accurately.

When the SOA element and the optical fiber are connected to each other, a coupling loss occurs, and the coupling loss generally has a variation of about 1 to 2 dB due to the fluctuation of the mode field and a slight mounting position shift. is there. In the conventional structure in which the reflector is monolithically integrated with the SOA element, the SOA is
Although the gain of the element itself can be accurately determined, the variation of the coupling loss at the time of mounting cannot be corrected, and as a result, a gain error of 2 to 4 dB occurs at both ends in the module as a whole.

In an SOA that does not perform a normal gain clamp, such an error can be corrected by adjusting the injection current, but in the gain clamp type SOA, the gain is kept constant even if the injection current is changed. It is difficult to correct the variation in module gain caused by.
This problem becomes particularly serious when a large number of SOAs are arranged and used as an amplifier array or a gate array, when the inter-channel transmission gain uniformity is required.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a gain clamp type semiconductor optical amplifier module having less gain setting error and variation, and a method of manufacturing the same. It is in.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a semiconductor optical amplifier module according to a first aspect of the present invention, which comprises an input section and an output section of the semiconductor optical amplifier. A planar optical waveguide provided on the substrate is connected to each of the semiconductor optical amplifiers, and a reflector is provided at a predetermined position of each of the planar optical waveguides connected to the input side and the output side of the semiconductor optical amplifier. Characterize.

The invention described in claim 2 is the same as claim 1.
In the semiconductor optical amplifier module described in (1), the planar optical waveguide is a silica optical waveguide, and the reflector is a UV grating.

Furthermore, a third aspect of the present invention is a method of manufacturing a semiconductor optical amplifier module, wherein a step of forming a planar optical waveguide on a substrate, and the input section and the output section of the semiconductor optical amplifier are each provided with An input of the semiconductor optical amplifier; and a step of connecting a planar optical waveguide, and a step of providing a reflector at a predetermined position of each of the planar optical waveguides connected to the input side and the output side of the semiconductor optical amplifier. At least one of the reflectors provided on the section side or the output section side is provided on the planar optical waveguide after connecting the semiconductor optical amplifier and the planar optical waveguide.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a view for explaining a first embodiment of a semiconductor optical amplifier module of the present invention, in which each of an input portion and an output portion of the semiconductor optical amplifier is provided on a substrate. The provided planar optical waveguides are connected, and a reflector is provided at each predetermined position of the planar optical waveguides connected to the input section side and the output section side of the semiconductor optical amplifier. The planar optical waveguide is a quartz optical waveguide, and the reflector is a UV grating.

That is, a 4-channel SOA array element
Each of the channels on both sides of 11 has a silica optical waveguide 12a.
_1-4, 12b_1-4Connected, and further quartz
System optical waveguide 12a_1-4, 12b_1-4Is the corresponding light
Fiber 13a_1-4, 13b _1-4It is connected to the.
Here, four silica-based optical waveguides 12a are provided on each of the left and right sides._1-4,
12b_1-4Are the refractive index changes due to UV light irradiation.
UV grating 14a_1-4, 14b
_1-4Is drawn.

Such a mounting structure can be easily realized by using a hybrid integration technique. For example, the SOA array element 11 may be flip-chip mounted on the element mounting portion provided by etching in the middle portion of the silica-based optical waveguide array formed on the Si substrate.

The difference of this embodiment from the conventional configuration is that U
The reflectors composed of the V gratings 14a _{1 to 4} and 14b ₁ to ₄ are not integrated with the SOA array element 11, but are made of silica optical waveguides 12a _{1 to 4} and 12b _{1 to 4}
It is provided at a predetermined position of, and this makes it possible to obtain a desired gain as a whole module.

The reason why such a gain is possible is that, in the module of the present configuration, a path including the SOA array element 11 between the UV gratings 14a _{1 to 4} and 14b _{1 to 4} provided on the input side and the output side is provided. A resonator is formed of the UV gratings 14a _{1 to 4} 1
Light having a wavelength determined by 4b1 to _4b4 oscillates. At this time, the oscillation condition is that the gain of the SOA exceeds the sum of the coupling loss between the SOA array element and the silica-based optical waveguide and the reflection loss of the UV grating. Is started and the gain of the SOA is clamped.

When the reflectance of the UV grating is constant, the sum of the coupling loss and the SOA gain is clamped so as to be a constant value. Therefore, even if the coupling loss varies, the module gain hardly varies, It is possible to set it to a desired value.

As described above, according to the semiconductor optical amplifier module of the present invention, by providing the reflector in the optical waveguide and including the coupling portion of the SOA and the optical waveguide which causes the gain error in the resonator, Even if the coupling loss fluctuates, it is possible to keep the fluctuation of the gain of the module small and set it to a desired value. In the case of a planar optical waveguide, it is easy to write UV gratings collectively on a plurality of arrayed optical waveguides, and a reflector with high uniformity between channels can be provided. This is particularly remarkable in the case of a multi-channel SOA array module using a planar optical waveguide as an input / output waveguide as in this embodiment.

Further, since the variation in the coupling loss between the SOA array element and the optical waveguide is small, it is possible to fabricate an array module in which the module gain is extremely uniform between the channels. Further, by using the semiconductor optical amplifier module of the present invention, variation in coupling loss does not lead to a large gain variation. Therefore, mounting is performed using so-called passive alignment in which the SOA and the optical waveguide are aligned without monitoring the optical output. It is possible to simplify the process,
Further, the hybrid integrated structure as shown in the present embodiment can realize downsizing and multiple channels.

(Second Embodiment) FIG. 2 is a diagram for explaining a module according to a second embodiment of the present invention.
FIG. 2A is a configuration diagram of the module, and FIG. 2B is a production process diagram of the module.

As shown in FIG. 2A, in the module having this structure, the silica-based optical waveguides 22a _{1 to 4} and 22b are provided in the channels on both sides of the four single SOA elements 21, respectively.
₁ to ₄ are connected, and further, the silica-based optical waveguide 22
a _{1 to 4} and 22b _{1 to 4} are the corresponding optical fibers 23a.
_{1 to 4} and 23b ₁ to ₄ are connected. Here, four left and right quartz optical waveguides 22a _{1 to 4} and 22b _{1 to 4 are provided.}
In the drawing, UV gratings 24a _{1 to 4} and 24b ₁ to ₄ are drawn, which respectively utilize the change in the refractive index due to the irradiation of ultraviolet light.

The present embodiment differs from the first embodiment is not a SOA array element, and in that the four single SOA element 21 is set to be mounted on the substrate, UV grating _24a 1 to 4, 24b one of the input side of the _{1 to 4 (24a 1 to 4)} or the output side _{(24b 1 to 4),} a point that is to be drawn after fixing the SOA element 21 on the substrate.

In the first embodiment, a UV grating was previously drawn on the optical waveguide, and then the SOA array element was mounted and fixed on the substrate. Also in that case, as described above, when the variation of the coupling loss is small to some extent,
The gain is automatically clamped at the operating point where the module gain is substantially constant, and a module with high channel-to-channel uniformity can be realized.

However, even if the coupling loss varies greatly, it is difficult to obtain exactly the desired module gain if the characteristics of each SOA element differ greatly. This is because the fluctuation of the coupling loss is compensated by the gain of the SOA, so that the SOA is operated at a different SOA injection current value, and as a result, the gain spectrum of the SOA element changes. Therefore, even if the gain is clamped at the operating point where the total sum of the coupling loss and the SOA gain is constant at the wavelength to be oscillated, the gain at the signal light wavelength changes with the change of the SOA gain spectrum.

[0027] In the semiconductor optical amplifier module of the present embodiment other hand, UV grating _{24a 1 to 4,} 2
To resolve this problem by setting appropriately in accordance with the reflectance of 4b _{1 to 4} the SOA element 21 and binding properties.
That is, in this embodiment, as shown in FIG. 2 (b), first, UV grating _24a 1 to 4, 24b ₁
Only one of the input side or the output side of _{4 to 4} is drawn in advance (S201) and the SOA element 21 is mounted.
It is fixed (S202). After that, the characteristics such as the coupling characteristics with the SOA element 21 and the silica-based optical waveguides 22a _{1 to 4} and 22b ₁ to ₄ and the gain spectrum are measured. The reflectance of the grating (24a _{1 to 4} or 24b _{1 to 4} ) is determined and drawn (S203). Alternatively, UV light may be irradiated to draw a UV grating while actually inputting signal light and monitoring the gain.

Through these steps, an SOA module having a high channel-to-channel uniformity and a desired module gain can be manufactured by using four single SOA elements even when there is variation in coupling loss between channels. it can.

Such a process is difficult in a structure in which a grating is monolithically integrated in a conventional SOA element, and is an effect which is made possible only by providing a grating in an input / output optical waveguide.

(Third Embodiment) FIG. 3 is a diagram for explaining a module according to a third embodiment of the present invention.
FIG. 3A is a configuration diagram of a module, and FIG. 3B is a manufacturing process diagram of the module.

As shown in FIG. 3 (a), this configuration of modules, four single SOA element 31 silica-based optical waveguide _32a 1 to 4 on both sides of each of the channels, 32b
₁ to ₄ are connected, and further, a silica-based optical waveguide 32
a _1-4 , 32b _1-4 are the corresponding optical fibers 33a
_{1 to 4} and 33b ₁ to ₄ are connected. Here, silica-based optical waveguide _32a 1 to 4 of the right and left four at a _{time, 32 b 1 to 4}
In the drawing, UV gratings 34a _{1 to 4} and 34b ₁ to ₄ respectively utilizing the change in refractive index due to irradiation with ultraviolet light are drawn.

This embodiment is different from the second embodiment in that not only the reflectance of the UV grating but also the reflection wavelength is adjusted for each channel for drawing, and this module is shown in FIG. ), First, a silica optical waveguide is formed on the substrate (S301), and the SOA element 31
Is mounted and fixed (S302). After that, the UV gratings (34a _1-4 and 34b _1-4 ) are drawn (S3
It is produced in the process of 03).

As described in the second embodiment, the SOA operating current changes when there are variations in the characteristics of each channel of the SOA element and variations in the optical coupling loss.
Changes in the SOA gain spectrum occur. Therefore, the second
In the semiconductor optical amplifier module of the above embodiment, the reflectance of the UV grating on one side is adjusted and drawn in order to obtain a desired gain at the signal light wavelength.

On the other hand, the gain at the signal light wavelength can be similarly adjusted by finely adjusting the reflection wavelength of the UV grating. This method is
This is an effective method for clamping in a large gain region close to the saturation gain of the device itself, and for equalizing the gain spectrum between channels. Of these, when clamping in a large gain area, the gain and gain spectrum change less depending on the current value in that area, so it is necessary to greatly adjust the grating reflectance, and in some cases, it may exceed the adjustable range. There is a problem that it will end up.

For example, if the coupling loss is large beyond the expected design range, it may not be possible to oscillate even if the reflectance is 100%. In such a case, a desired signal gain can be obtained by changing the reflection wavelength of the grating to a wavelength having a higher gain on the SOA gain spectrum. When it is desired to equalize the gain spectrum between channels, for example, the signal light wavelength may cover a wide wavelength range.

Normally, when the gain is clamped, a flat gain characteristic is obtained in a fixed wavelength range, but it is often difficult to cover the wavelength range of several tens of nm depending on the operating conditions for clamping. In that case, there is a problem that the wavelength dependence of the gain is generated in accordance with the gain spectrum of the SOA particularly in the wavelength region deviated from the center, which is not preferable because it causes channel-to-channel variation in a multi-channel array module. . Even in this case,
By adjusting the reflection wavelength and the reflectance of the grating, it is possible to clamp the gain with a desired gain spectrum.

In this embodiment, a desired module gain is obtained by adjusting the reflection wavelength and the reflectance of the UV grating for drawing, and equalization of the gain spectrum between the channels is also realized. In order to manufacture such a module, first, an optical waveguide in which a grating is not drawn is manufactured, an SOA element is mounted and fixed, and then an SOA is manufactured.
It suffices to measure the gain spectrum of and to draw the gratings of the reflection wavelength and the reflectance required for both the left and right optical waveguides according to the result.

[0038]

As described above, according to the semiconductor optical amplifier module of the present invention, the reflector is provided at a predetermined position on the optical waveguide, and the coupling portion between the SOA and the optical waveguide that causes the gain error is provided. By including it in the resonator, even if the coupling loss fluctuates, it is possible to suppress the gain fluctuation as a module and set it to a substantially desired value.

Further, in the semiconductor optical amplifier module of the present invention, since the variation in the coupling loss between the SOA element and the optical waveguide is small, it is possible to manufacture the array module in which the module gain is extremely uniform between the channels.

Further, by using the semiconductor optical amplifier module of the present invention, the variation of the coupling loss does not lead to a large gain variation, so that the optical output is not monitored and the S
It becomes possible to simplify the mounting process by using so-called passive alignment for aligning the OA and the optical waveguide, and it is possible to realize a compact and multi-channel configuration by the hybrid integrated configuration.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a first embodiment of a semiconductor optical amplifier module of the present invention.

2A and 2B are views for explaining a second embodiment of the semiconductor optical amplifier module of the present invention, FIG. 2A is a block diagram of the module, and FIG. 2B is a block diagram of a manufacturing process of the module.

3A and 3B are views for explaining a third embodiment of the semiconductor optical amplifier module of the present invention, FIG. 3A is a block diagram of the module, and FIG. 3B is a block diagram of a manufacturing process of the module.

FIG. 4 is a diagram for explaining a configuration example of a conventional gain clamp type SOA module.

[Explanation of symbols]

11, 21, 31 SOA array elements _12a1-4 , _12b1-4 , _22a1-4 , 22b
_{1~4, 32a 1~4, 32b 1~4} silica-based optical waveguide _{13a 1~4, 13b 1~4, 23a 1~4} , 23b
_1-4 , 33a _1-4 , 33b _1-4 , 43a, 43b
Optical fiber _{14a 1~4, 14b 1~4, 24a 1~4} , 24b
_1-4 , 34a _1-4 , 34b _1-4 UV grating 40 SOA element 41 SOA active regions 42a, 42b Bragg grating

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takuya Tanaka             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation F term (reference) 2H047 KA03 LA02 MA05 NA08 RA08                       TA31                 5F073 AA67 AA89 AB01 AB04 AB21                       AB25 AB28 BA03 EA29 FA30                       HA05 HA08 HA11

Claims (3)

[Claims] 1. A flat optical waveguide provided on a substrate is connected to each of an input section and an output section of a semiconductor optical amplifier, and the planar optical waveguide is connected to an input section side and an output section side of the semiconductor optical amplifier. A semiconductor optical amplifier module comprising a reflector at a predetermined position of each of the planar optical waveguides. 2. The semiconductor optical amplifier module according to claim 1, wherein the planar optical waveguide is a silica optical waveguide, and the reflector is a UV grating. 3. A method for manufacturing a semiconductor optical amplifier module, comprising the steps of forming a planar optical waveguide on a substrate, and connecting the planar optical waveguide to each of an input section and an output section of the semiconductor optical amplifier. A step of providing a reflector at a predetermined position of each of the planar optical waveguides connected to the input section side and the output section side of the semiconductor optical amplifier, and the reflector is provided on the input section side or the output section side of the semiconductor optical amplifier. At least one of the reflectors is provided on the planar optical waveguide after connecting the semiconductor optical amplifier and the planar optical waveguide to each other.