JP3876467B2 - Semiconductor laser module and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor laser module. More specifically, the present invention relates to a novel configuration of a semiconductor laser module in which an optical fiber having a diffraction grating near its end and a semiconductor laser are combined, and a method for manufacturing the same.
[0002]
[Prior art]
FIG. 7 is a longitudinal sectional view showing a typical configuration of the semiconductor laser module.
[0003]
As shown in the figure, the semiconductor laser module is generally configured by combining a semiconductor laser 2 mounted in a package 1 and an optical fiber 4 having a connector 3 attached to an end thereof.
[0004]
Here, the semiconductor laser 2 is fixed to the bottom of the package 1 via some heat radiating means such as a Peltier effect element 5 and a chip carrier 6. On the other hand, the end of the optical fiber 4 is inserted into the ferrule 7 and is held inside the connector 3. Further, the package 1 and the connector 3 are configured to be mechanically coupled to each other. Further, a window made of hermetic glass 8 is formed in a part of the package 1 in order to optically couple them. Further, in order to improve the optical coupling efficiency between the semiconductor laser 2 and the optical fiber 4, an optical system for converging the propagation light is often provided between them, and in the example shown in FIG. A lens 9 is mounted on the end of the carrier 6.
[0005]
FIG. 8 is an enlarged view showing the configuration of the optical system from the semiconductor laser 2 to the optical fiber 4 in the semiconductor laser module shown in FIG.
[0006]
As already described with reference to FIG. 7, the semiconductor laser 2 and the optical fiber 4 are optically coupled via the lens 9. Further, in this semiconductor laser module, a diffraction grating 10 is provided near the end of the optical fiber 4 to control the light emission mode Na.
[0007]
As for the diffraction grating formed in such an optical fiber, a method of forming a refractive index distribution in an optical fiber by utilizing interference or diffraction of laser light is known in addition to a method of physically processing the optical fiber. Yes. Furthermore, the present patent applicant has already filed a patent application for a method of forming a refractive index profile in an optical fiber using photolithography technology and X-ray irradiation.
[0008]
That is, in the method according to the above patent application, a mask of a photoresist or a metal thin film is formed on the surface of an optical transmission line such as an optical fiber, and the optical transmission line is exposed to X-rays in a specific pattern using this mask. This is a method of forming a refractive index distribution inside the optical transmission line itself. Here, in particular, when exposure is performed with long-wavelength X-rays (wavelengths of about several hundred to thousands of kilometres), a higher light source intensity can be obtained than methods using an excimer laser or an ultraviolet spectrum of mercury, and the X-ray itself It is considered advantageous in that the wavelength is short. According to such a method, a desired refractive index distribution can be formed in a short time under good controllability.
[0009]
[Problems to be solved by the invention]
However, when a semiconductor laser module is actually manufactured using an optical fiber in which a diffraction grating is formed by X-ray irradiation, there may be a large individual difference in the outgoing light from the outgoing end of the optical fiber. For this reason, it cannot be said that the method of forming a diffraction grating by X-ray irradiation has been sufficiently put into practical use, contrary to its high productivity.
[0010]
Accordingly, the present invention solves the above-described problems of the prior art, and uses a new optical fiber having a diffraction grating formed by using X-rays, and a novel semiconductor laser module capable of obtaining output light according to design specifications and its Its main purpose is to provide a manufacturing method.
[0011]
[Means for Solving the Problems]
According to the present invention, a semiconductor laser and an optical fiber that propagates light emitted from the semiconductor laser are provided, and a refractive index distribution formed by X-ray irradiation is formed in the core near the incident end of the optical fiber. A semiconductor laser module including a diffraction grating, wherein a polarization direction of light emitted from the semiconductor laser coincides with an irradiation direction of X-rays irradiated to form a diffraction grating on the optical fiber. A laser module is provided.
[0012]
In addition, as a method of manufacturing the semiconductor laser module according to the present invention, a semiconductor laser and an optical fiber that propagates light emitted from the semiconductor laser are provided, and further, X in the core near the incident end of the optical fiber is provided. In a method of manufacturing a semiconductor laser module having a diffraction grating having a refractive index profile formed by irradiation of radiation, the optical fiber is moved to the optical fiber while operating the semiconductor laser and monitoring the intensity of light emitted from the optical fiber. A method is provided comprising the step of rotating with respect to the propagation optical axis of the fiber and adjusting the polarization direction of the emitted light of the semiconductor laser to coincide with the direction giving the maximum reflectivity of the diffraction grating. .
[0013]
Furthermore, according to another aspect of the present invention, a semiconductor laser and an optical fiber for propagating light emitted from the semiconductor laser are provided, and further formed in the core near the incident end of the optical fiber by X-ray irradiation. In the semiconductor laser module having a diffraction grating having a refractive index distribution, the optical fiber is an optical fiber having at least two diffraction gratings formed by X-ray irradiation from irradiation directions orthogonal to each other. A semiconductor laser module is provided.
[0014]
Furthermore, according to another aspect of the present invention, a semiconductor laser and an optical fiber for propagating light emitted from the semiconductor laser are provided, and further formed in the core near the incident end of the optical fiber by X-ray irradiation. Also provided is a semiconductor laser module having a diffraction grating having a refractive index distribution, wherein the optical fiber is configured to be rotatable with respect to a propagation optical axis of the optical fiber. .
[0015]
Further, a diffraction grating comprising a semiconductor laser and an optical fiber for propagating the emitted light of the semiconductor laser, and further having a refractive index profile formed by X-ray irradiation in the core near the incident end of the optical fiber. The diffraction grating is formed so as to have a reflectance higher than the finally required reflectance, and the optical fiber is connected to the propagation optical axis of the optical fiber. A method is provided that includes the step of rotating to adjust the emitted light to a desired characteristic.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The present invention has been completed by paying attention to the fact that, when a refractive index distribution is formed in an optical fiber by X-rays, a refractive index distribution also occurs in the X-ray irradiation direction. That is, when a refractive index distribution is formed in an optical fiber by X-ray irradiation, the X-ray is absorbed by the optical fiber itself, so that the reflectivity changes from the X-ray source side toward the opposite side, and thus propagates. It was found that polarization dependence of light occurs. The polarization dependency of the diffraction grating depending on the X-ray irradiation direction is extremely remarkable. In a severe case, a predetermined reflectivity as the design value is obtained in the direction in which the diffraction occurs, but the direction orthogonal thereto is obtained. Then, the reflectance may be zero. Accordingly, it has been found that in the semiconductor laser module using such an optical fiber, the output characteristics change remarkably depending on how the optical fiber is mounted.
[0017]
Therefore, in the semiconductor laser module according to the present invention, by mounting the optical fiber so that the polarization direction of the emitted light of the semiconductor laser and the direction in which the diffraction grating formed in the optical fiber gives the maximum reflectance, The polarization dependence is substantially eliminated.
[0018]
According to another aspect of the present invention, when a diffraction grating is formed by irradiating an optical fiber with X-rays, the diffraction grating is formed by forming two diffraction gratings whose X-ray irradiation directions are orthogonal to each other. The polarization dependency of the provided optical fiber can be substantially eliminated. Since the optical fiber having such a plurality of diffraction gratings does not require adjustment with respect to the polarization direction, the manufacturing efficiency of the semiconductor module is improved.
[0019]
Further, according to another aspect of the present invention, an optical fiber in which a diffraction grating having a reflectance slightly higher than a desired reflectance is formed in advance using the polarization dependence of the diffraction grating as described above, By rotating with respect to the propagation optical axis when coupling with the semiconductor laser, it becomes possible to change the output characteristics of the semiconductor laser module within a predetermined range including a desired reflectance. This means that changes in output characteristics due to variations in other conditions can be eliminated by the rotation of the optical fiber, and at the same time, the manufacture of semiconductor laser modules of various specifications using a single specification optical fiber with a diffraction grating is possible. It means that it is possible.
[0020]
Hereinafter, the semiconductor laser module according to the present invention will be described more specifically with reference to the drawings. However, the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention. .
[0021]
【Example】
FIG. 1 is a diagram schematically showing a refractive index distribution formed in an optical fiber by X-ray irradiation.
[0022]
That is, FIG. 1 shows a cross section perpendicular to the propagation optical axis of the optical fiber 4 on which the diffraction grating 10 is formed. As shown by the arrows in the figure, X-rays are irradiated from above to form a refractive index distribution. Has been. However, when the optical fiber is irradiated with X-rays, the X-rays are absorbed by the optical fiber itself, so that the region where the refractive index has changed due to the X-rays is directly irradiated with X-rays as shown by the oblique lines in the figure. It is thicker on the upper side and thinner on the lower side. For this reason, the reflectance distribution corresponding to the change in the refractive index is distributed in the cross-sectional direction of the optical fiber, and the propagation characteristics of the optical fiber inevitably have polarization dependency.
[0023]
FIG. 2 is a graph showing the relationship between the emitted light intensity when a semiconductor laser is injected into an optical fiber having a diffraction grating using the refractive index distribution as described above and the rotation angle with respect to the propagation optical axis of the optical fiber. It is. As shown in the figure, with this optical fiber, the emitted light intensity decreases significantly at 90 ° and 270 °, but the emitted light at this time is in a single mode as shown in FIG. 3 (a). . On the other hand, when the rotation angle of the optical fiber is other than this, the emitted light is in the FP mode as shown in FIG. Therefore, when the semiconductor laser module is manufactured, it is possible to set effective outgoing light characteristics by operating the semiconductor laser and rotating the optical fiber while monitoring the wavelength spectrum of the outgoing light emitted from the optical fiber. .
[0024]
Also, when manufacturing a semiconductor laser module using an optical fiber having such characteristics, the rotation angle of the optical fiber with respect to the polarization of the emitted light of the semiconductor laser is appropriately adjusted in consideration of the polarization dependency as described above. Thus, desired output characteristics can be obtained. In addition, when there are other fluctuation factors regarding the characteristics of the output light, a desired value can be obtained by increasing the design value of the diffraction grating in advance and rotating the optical fiber. That is, as shown as a range V in FIG. 2, when the optical fiber is rotated in an angular region where the characteristics of the optical fiber are changed, the characteristics of the output light can be continuously changed.
[0025]
That is, a semiconductor laser module having an optical fiber with a diffraction grating can perform single mode oscillation if the reflectance of the diffraction grating is about several percent. On the other hand, it is not always preferable to increase the reflectivity because it means that the intensity of light that can be extracted outside decreases. Therefore, in practice, a reflectance of about 5 to 6% is preferable. Therefore, when forming the diffraction grating in the optical fiber, for example, the processing conditions are set so that the reflectivity is about 10%, and when the optical fiber is attached to the semiconductor laser module, the optical fiber is rotated to 5 to 5. The reflectance can be adjusted to 6%. According to such a manufacturing method, a change in characteristics of the semiconductor laser module due to other manufacturing conditions can be eliminated by adjustment, and a semiconductor laser module that exactly matches the design specifications can be manufactured.
[0026]
FIG. 4 is a diagram showing a specific configuration example of an optical fiber that can be used to realize another aspect of the semiconductor laser module according to the present invention.
[0027]
As shown in FIG. 4A, two diffraction gratings 10a and 10b are formed in this optical fiber. The diffraction gratings 10a and 10b are formed by irradiating X-rays from directions orthogonal to each other as shown in FIG. 4 (b). Therefore, this optical fiber has a polarization dependency shifted by 90 degrees from each other, and can be handled as an optical fiber having no polarization dependency in practical use.
[0028]
As a method for forming a plurality of diffraction gratings as described above, the step of forming a diffraction grating for one optical fiber may be repeated, but a plurality of optical fibers each having a diffraction grating formed therein are fused. It can also be made to wear.
[0029]
Further, the diffraction grating 10 may be formed on the optical fiber in a region where the ferrule is inserted in the optical fiber connector as shown in FIG. 7, or as shown in FIG. It may be formed outside. Further, as shown in FIG. 6, diffraction gratings 10 may be formed respectively inside and outside the ferrule. Furthermore, in the X-ray irradiation for forming the diffraction grating, the X-ray irradiation can be performed while rotating the X fiber around the propagation optical axis, thereby forming a diffraction grating having no angle dependency.
[0030]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to prevent variation in characteristics due to polarization dependence by using an optical fiber in which a diffraction grating is formed by X-ray irradiation. It is also possible to manufacture a semiconductor laser module having no characteristics.
[0031]
In addition, according to another aspect of the present invention, it is possible to manufacture a semiconductor laser module having desired characteristics using a ready-made member.
[0032]
Furthermore, according to the present invention, it is possible to manufacture a semiconductor laser module having different output light characteristics using an optical fiber having a diffraction grating of a single specification.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of a refractive index distribution formed in an optical fiber by X-ray irradiation.
FIG. 2 is a graph showing a relationship between an emitted light intensity when a semiconductor laser is injected into an optical fiber including a diffraction grating and a rotation angle with respect to a propagation optical axis of the optical fiber.
FIG. 3 is a graph showing a mode of outgoing light of an optical fiber including a diffraction grating.
FIG. 4 is a diagram showing a configuration example of an optical fiber that can be used in the semiconductor laser module according to the present invention.
FIG. 5 is a diagram showing another configuration example of the semiconductor laser module according to the present invention.
FIG. 6 is a diagram showing still another configuration example of the semiconductor laser module according to the present invention.
FIG. 7 is a diagram showing a typical configuration of a semiconductor laser module.
8 is an enlarged view showing a configuration of an optical system in the semiconductor laser module shown in FIG.
[Explanation of symbols]
1 ... Package,
2 ... semiconductor laser,
3 ... Connector,
4 ... Optical fiber,
5 ... Peltier expensive element,
6 ... chip carrier,
7 ... Ferrule,
8 ... Hermetic glass,
9 ... Lens,
10, 10a, 10b ... Diffraction grating

Claims (4)

A semiconductor laser and an optical fiber that propagates the light emitted from the semiconductor laser are provided, and a diffraction grating having a refractive index distribution formed by X-ray irradiation is provided in the core near the incident end of the optical fiber. in the semiconductor laser module, also it has a refractive index distribution in the irradiation direction of the X-ray irradiated to form a diffraction grating in the optical fiber, the polarization direction of the outgoing light of the semiconductor laser, consistent with the irradiation direction A semiconductor laser module characterized by comprising: A semiconductor laser and an optical fiber that propagates the light emitted from the semiconductor laser are provided, and a diffraction grating having a refractive index distribution formed by X-ray irradiation is provided in the core near the incident end of the optical fiber. In a semiconductor laser module, the optical fiber includes at least two diffraction gratings formed at different positions by X-ray irradiation from irradiation directions orthogonal to each other, and the X-rays irradiated to form the diffraction grating on the optical fiber A semiconductor laser module characterized by being an optical fiber having a refractive index distribution in the irradiation direction . 3. The semiconductor laser module according to claim 2, wherein the optical fiber having at least two diffraction gratings is formed by combining a plurality of optical fibers each having a single diffraction grating formed by X-ray irradiation. A semiconductor laser module characterized by being an optical fiber. A semiconductor laser and an optical fiber that propagates the light emitted from the semiconductor laser are provided, and a diffraction grating having a refractive index distribution formed by X-ray irradiation is provided in the core near the incident end of the optical fiber. The semiconductor laser module has a refractive index distribution in the irradiation direction of X-rays irradiated to form a diffraction grating on the optical fiber, and the optical fiber can be rotated with respect to the propagation optical axis of the optical fiber. A semiconductor laser module.

Images