JP2005311185A - Semiconductor laser equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize the semiconductor laser equipment by employing a compact wavelength monitor. <P>SOLUTION: This equipment is provided with a collimate lens 20 positioned at the backward outgoing beam track of a laser diode 10, a reflecting mirror 60 for receiving some of the beams paralleled via the collimate lens 20 and separating incoming beams from the parallel beams, a first photo diode 30 positioned at the track of beams separated via the reflecting mirror 60 and receiving the beams, an etalon 50 positioned at any location on the track of parallel beams which is more distant from the collimate lens 20 than that of the reflecting mirror 60 to ensure that parallel beams not received by the reflecting mirror 60 can be received, and a second photo diode 40 for receiving beams passing through the etalon 50. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor laser device having a wavelength monitoring function.

  In an optical communication system using wavelength division multiplexing (WDM), light having different wavelengths oscillated from a plurality of semiconductor lasers is multiplexed and transmitted on a single optical fiber. However, in a communication system using Dense Wavelength Division Multiplexing (DWDM; Dense WDM), which multiplexes light at a higher density, the wavelength interval of the multiplexed light is narrow, so that there is a shift to the oscillation wavelength of each semiconductor laser. When this occurs, there is a problem in that crosstalk occurs between multiplexed light and signal degradation occurs.

  In order to solve this problem, the wavelength monitoring function is built in the semiconductor laser device, and the wavelength information of the backward emitted light emitted simultaneously with the forward emitted light guided to the optical fiber out of the light emitted from the semiconductor laser is monitored. A semiconductor laser device that stabilizes the oscillation wavelength by returning to the operating temperature of the semiconductor laser has been proposed.

  For example, in the conventional optical transmission device disclosed in Patent Document 1, light from a laser light source is converted into parallel light by a lens, and a half mirror is arranged in the parallel light to branch a part of the parallel light. The light branched by the mirror is received by the first photodetector, the light transmitted through the half mirror is passed through the etalon, and the transmitted light from the etalon is received by the second photodetector. By comparing each signal light received by the first light detector and the second light detector, a signal for making the oscillation wavelength of the laser light source become a desired value is obtained, and the signal of the laser light source is obtained by the signal. Wavelength control is performed.

JP 2001-284711 A

  However, as in the conventional optical transmission device disclosed in Patent Document 1, in the method of dividing the signal light by the half mirror, there is a problem that the area occupied by the half mirror portion is large and affects the miniaturization of the semiconductor laser device. there were. In addition, since the branching ratio between the first photodetector and the second photodetector can be determined only by the reflectance and transmittance of the half mirror, when changing this ratio, the reflectance and transmittance are different. It was necessary to prepare a half mirror.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to reduce the size of the wavelength monitor portion and to reduce the size of the entire semiconductor laser device.

  The semiconductor laser device according to the present invention includes a semiconductor laser, a lens that is installed on the path of the backward emitted light of the semiconductor laser, converts the backward emitted light into parallel light, and the parallel light is a first portion corresponding to a part of the cross section. A light separation unit that separates the partial light and the second partial light corresponding to a portion excluding the first partial light, a first photodetector that receives the first partial light, and a second partial light A wavelength filter that transmits light, and a second photodetector that receives the second partial light that has passed through the wavelength filter. The wavelength information of the light received by the first photodetector and the second photodetector. Based on the wavelength information of the received light, the wavelength of the light emitted from the semiconductor laser is controlled.

  According to the present invention, the light separation unit for separating the semiconductor laser light into the first partial light and the second partial light is provided, the first partial light is received by the first photodetector, and is transmitted through the wavelength filter. The second partial light is received by the second photodetector, and the wavelength of the light emitted from the semiconductor laser is controlled based on the detected wavelength information. Since a small component such as a reflecting mirror can be used instead of the mirror, the entire semiconductor laser device can be miniaturized.

Hereinafter, various embodiments of the present invention will be described.
Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a semiconductor laser apparatus 100 according to the first embodiment of the present invention. As shown in the drawing, a semiconductor laser device 100 includes a laser diode (semiconductor laser) 10, a collimating lens (lens) 20, a first photodiode (first photodetector) 30, and a second photodiode (second photodiode). A light detector 40, an etalon (wavelength filter) 50, and a reflecting mirror (light separator) 60 are provided.

The collimating lens 20 is installed on the path of backward emission light emitted from the laser diode 10.
About half of the rearward emitted light collimated by the collimating lens 20 is incident on the reflecting mirror 60 at a position farther from the laser diode 10 than the collimating lens 20 on the path of the rearward emitted light emitted from the laser diode 10. Are arranged as follows. The reflecting mirror 60 is installed so as to change the path of incident light by 90 degrees.
On the path of the light totally reflected by the reflecting mirror 60, the first photodiode 30 is installed.

  Further, the etalon 50 is installed at a position farther from the collimating lens 20 than the reflecting mirror 60 on the path of light collimated by the collimating lens 20. Further, the second photodiode 40 is installed at a position farther from the collimating lens 20 than the etalon 50 on the path of the collimated light.

Next, the operation will be described.
The light emitted backward from the laser diode 10 is collimated by the collimator lens 20. About half of the parallel rays are incident on the reflecting mirror 60 and totally reflected, and the path changes by 90 degrees. The totally reflected light beam enters the first photodiode 30.

  Of the light collimated by the collimating lens 20, the remaining light rays that have not entered the reflecting mirror 60 enter the etalon 50. The light that has passed through the etalon 50 enters the second photodiode 40.

  The output from the first photodiode 30 is used to monitor the intensity of the laser diode 10. Further, since the light transmitted through the etalon 50 has a characteristic of periodically increasing / decreasing depending on the wavelength, the output from the second photodiode 40 is used to monitor the wavelength of the laser diode 10.

  By returning the wavelength error monitored by the outputs from the first photodiode 30 and the second photodiode 40 to the operating temperature of the laser diode 10, the oscillation wavelength can be stabilized.

  As a filter whose transmitted light depends on the wavelength, a Fabry-Perot etalon is often used. However, if the transmitted light depends on the wavelength, it may be replaced with another filter.

  As described above, according to the first embodiment, the reflecting mirror 60 is used as a means for branching the light beam toward the first photodiode 30 and the second photodiode 40, so that it has been described in relation to the prior art. Compared to the case of using a half mirror, the volume can be halved. As a result, the semiconductor laser device 100 can be reduced in size.

  Further, by shifting the position of the reflecting mirror 60 in a direction perpendicular to the axis line connecting the light emitting surface of the laser diode 10 and the light receiving surface of the second photodiode 40, the first photodiode 30 and the second photodiode 40. It is possible to easily change the intensity ratio of the light beam going to.

  In addition, the areas of the light receiving portions of the first photodiode 30 and the second photodiode 40 are usually smaller than that of light rays. In this case, the point that the first embodiment is superior to the method using the half mirror for the beam branching described in relation to the prior art will be described below using a specific example.

FIG. 2 shows the light reception of the second photodiode 40 when the light beam traveling toward the first photodiode 30 and the second photodiode 40 is divided using a half mirror instead of the reflecting mirror 60 of the first embodiment. It is a figure which shows the positional relationship of a surface and a light ray.
Here, it is assumed that the second photodiode 40 has a light receiving portion having a width of 0.4 mm and a height of 0.4 mm. Also, consider a case where the ray radius within the range where the ray intensity is 1 / e ² of the ray center intensity is 0.5 mm.

  In the half mirror, the following problems occur because the entire light beam is branched. As shown in FIG. 2, the light intensity distribution and the photo when the light beam incident on the second photodiode 40 is mounted so that the center of the second photodiode 40 is aligned with the center in the height direction and the center in the horizontal direction. The relationship of the light receiving range of the diode is shown in FIG. In this case, the intensity of light received by the second photodiode 40 is 16.6% of the intensity of the entire light beam.

On the other hand, FIG. 4 is a diagram showing the positional relationship between the light receiving surface of the second photodiode 40 and the light beam according to the first embodiment. The area and light ray radius of the light receiving surface of the second photodiode 40 are the same as those in FIG.
When a half mirror is used for beam splitting, the entire speed of light is separated at a constant ratio, so that the incident surface of the beam on the second photodiode 40 is as shown in FIG. When the reflecting mirror 60 is used as in the apparatus 100, the light beam incident on the reflecting mirror 60 is completely branched, so that the light beam reaching the second photodiode 40 is as shown in FIG. Become.

  The light intensity distribution and the photodiode when the horizontal end of the light receiving portion of the second photodiode 40 is aligned with the center of the light beam when the reflecting mirror 60 is not provided and the center in the height direction is aligned with the center of the light beam. FIG. 5 shows the relationship between the light receiving ranges. In this case, the intensity of the light received by the second photodiode 40 is 25.7% of the intensity of the entire light beam.

When the first photodiode 30 is the same as the second photodiode 40 and mounted in the same manner as described above with respect to the light incident on the first photodiode 30, the first photodiode Similar results are obtained for the intensity received by 30.
Thus, by using the reflecting mirror 60 for branching the light beam, it is possible to receive light more efficiently with the photodiode having the same light receiving area.

FIG. 6 is a diagram illustrating a more preferable installation method of the reflecting mirror 60 according to the first embodiment. The figure is a cross-sectional view of the mounting portion of the reflecting mirror 60 as viewed from the same direction as in FIG. 1. As shown in FIG. Move in a direction perpendicular to. Thereby, the reflecting mirror 60 can be easily moved to a position where the light beam is branched at an arbitrary ratio.
The metal member is desirably installed so that the optical axis of the light reflected by the reflecting mirror 60 coincides with the central axis of the light receiving surface of the first photodiode 30. Furthermore, if the metal member is installed so as to be movable only in the direction perpendicular to the optical axis of the laser diode 10, it is possible to prevent the position of the optical axis of the reflected light from deviating from the first photodiode 30. For this reason, for example, the metal member may be moved by placing the end surface of the metal member against the slide surface of the protrusion as shown in the drawing.

Embodiment 2. FIG.
FIG. 7 is a diagram showing a configuration of a semiconductor laser apparatus 200 according to the second embodiment of the present invention. The same reference numerals as those in FIG. 1 represent the same components. In the second embodiment, a total reflection mirror is deposited on a part of the incident surface of the etalon 51 to form a mirror part (reflecting mirror part) 61. Other configurations are the same as those in the first embodiment.

Next, the operation will be described.
The light emitted backward from the laser diode 10 is collimated by the collimating lens 20. The parallel rays are incident on the etalon 51. A part of the incident light is totally reflected by the mirror unit 61, and the path changes by 90 degrees. The totally reflected light beam enters the first photodiode 30.

  Of the light incident on the etalon 51, the remaining light rays that have not been totally reflected by the mirror unit 61 are transmitted through the etalon 51. The light transmitted through the etalon 51 is incident on the second photodiode 40.

The output from the first photodiode 30 is used to monitor the intensity of the laser diode 10 as in the first embodiment, and the output from the second photodiode 40 is used to monitor the wavelength of the laser diode 10. Used for
By returning the wavelength error monitored by the outputs from the first photodiode 30 and the second photodiode 40 to the operating temperature of the laser diode 10, the oscillation wavelength can be stabilized.

  As described above, according to the second embodiment, since a part of the etalon 51 is a reflecting mirror, there is no need to install a reflecting mirror as a separate component, and the semiconductor laser device can be further downsized.

  Further, by using the total reflection mirror for branching the light beam, it is possible to receive light more efficiently by the photodiode having the same light receiving area as in the first embodiment.

  Further, by moving the etalon 51 in a direction perpendicular to the optical axis of the laser diode 10, the mirror unit 61 can be easily moved to a position where the light beam is branched at a desired ratio.

Embodiment 3 FIG.
FIG. 8 shows a configuration of a semiconductor laser apparatus 300 according to the third embodiment of the present invention. The same reference numerals as those in FIG. 1 represent the same components. The semiconductor laser device 300 includes a planar substrate (transmission plate) 70 instead of the reflecting mirror 60.

The flat substrate 70 is a glass substrate having opposing surfaces formed in parallel. The flat substrate 70 is arranged so that about half of the backward emitted light collimated by the collimating lens 20 is incident, and the light is branched by translating the path of the incident light.
A first photodiode 30 is installed on the path of light transmitted through the planar substrate 70.

Next, the operation will be described.
The light emitted backward from the laser diode 10 is collimated by the collimator lens 20. About half of the parallel rays are incident on the flat substrate 70, and the path is separated from the original rays by translation. The light beam that has been transmitted through the planar substrate 70 and separated is incident on the first photodiode 30.

  Of the light collimated by the collimating lens 20, the remaining light rays that have not entered the flat substrate 70 enter the etalon 50. The light that has passed through the etalon 50 enters the second photodiode 40.

  Outputs from the first photodiode 30 and the second photodiode 40 are used in the same manner as in the first embodiment, and are used to stabilize the oscillation wavelength of the laser diode 10.

  Even if the planar substrate 70 is used as the light branching means as in the third embodiment, the semiconductor laser device can be downsized as in the first embodiment.

  Further, by moving the planar substrate 70 in a direction perpendicular to the optical axis of the laser diode 10, the light beam branching ratio can be easily changed.

  Further, since the light beam separated by the flat substrate 70 is parallel to the original light beam collimated by the collimating lens 20, the first photodiode 30 and the second photodiode 40 may be mounted side by side on the same carrier. This is possible, and the number of parts can be reduced and the cost can be reduced as compared with the first embodiment. Further, a wavelength control device or the like may be housed inside a carrier on which the first photodiode 30 and the second photodiode 40 are mounted. Thereby, further miniaturization of the apparatus can be achieved.

Embodiment 4 FIG.
FIG. 9 is a diagram showing a configuration of a semiconductor laser apparatus 400 according to the fourth embodiment of the present invention. The same reference numerals as those in FIG. 1 represent the same components. The semiconductor laser device 400 does not have a beam splitter.

  In the semiconductor laser device 400, the first photodiode 30 is rearward parallelized by the collimator lens 20 at a position closer to the collimator lens 20 than the etalon 50 on the path of the backward emitted light emitted from the laser diode 10. It arrange | positions so that about half of the emitted light may enter. That is, in the fourth embodiment, the etalon 50 is disposed between the first photodiode 30 and the second photodiode 40.

Next, the operation will be described.
The light emitted backward from the laser diode 10 is collimated by the collimator lens 20. About half of the parallel rays are incident on the first photodiode 30.

  Of the light collimated by the collimating lens 20, the remaining light rays that have not entered the first photodiode 30 enter the etalon 50. The light that has passed through the etalon 50 enters the second photodiode 40.

  Outputs from the first photodiode 30 and the second photodiode 40 are used in the same manner as in the first embodiment, and are used to stabilize the oscillation wavelength of the laser diode 10.

  As in the fourth embodiment, the configuration in which the etalon 50 is sandwiched between the first photodiode 30 and the second photodiode 40 can be carried out without installing a beam branching means. The same effect as in the first form can be obtained. Further, the cost can be reduced by the amount of parts that can be reduced.

  Further, as in the fourth embodiment, by arranging the first photodiode 30 closer to the light source than the etalon 50, the intensity monitoring light and the wavelength monitoring light can be completely separated. . That is, when the first photodiode 30 is disposed farther from the collimating lens 20 than the etalon 50, when the mounting position of the etalon 50 is shifted, a small part of the light transmitted through the etalon 50 is the first. This is because the light enters the photodiode 30 and the wavelength monitoring light enters the first photodiode 30.

  Further, by moving the first photodiode 30 in the direction perpendicular to the optical axis of the laser diode 10, the branching ratio of the light beam can be easily changed.

Embodiment 5 FIG.
The transmittance of the Fabry-Perot etalon used for the etalons 50 and 51 in the first to fourth embodiments has a characteristic of periodically increasing and decreasing depending on the frequency. The frequency difference between the maximum value of the frequency and the next maximum value is called FSR (free spectral range), and the frequency interval between adjacent channels in the wavelength division multiplexing system is often matched with this FSR.

  However, in recent years, the multiplexing in the wavelength division multiplexing system has become high density. For example, when the frequency interval between adjacent channels is 25 GHz, a Fabry-Perot etalon of a commonly used material is a resonator formed of an etalon. The length must be increased, and it is difficult to fit in the hermetic package of the semiconductor laser device. This is illustrated in FIG. 10 using the configuration of the first embodiment.

  In the fifth embodiment, the resonator length of the etalon is not increased in one direction, and it can cope with high-density wavelength multiplexing.

FIG. 11 is a block diagram showing a configuration of a semiconductor laser apparatus 500 according to the fifth embodiment of the present invention. The same reference numerals as those in FIG. 1 represent the same components.
As shown in the drawing, the etalon 53 has a rectangular parallelepiped shape, and one corner on the opposite side to the light incident surface is cut obliquely. The etalon 53 is formed so that incident light is reflected by the cut surface and is incident on the second photodiode 40.
By configuring the etalon 53 in this way, it is possible to lengthen the light passage path in the etalon 53 without increasing the length of the etalon 53 itself.

  The operation of the semiconductor laser apparatus 500 is the same as that of the semiconductor laser apparatus 100. In addition to the same effects as those of the first embodiment, the apparatus can be downsized for higher-density wavelength multiplexing.

  In the semiconductor laser device 500, the first photodiode 30 and the second photodiode 40 are bonded to one member and can be mounted on the same surface, so that the number of components can be reduced. . Moreover, you may comprise so that a wavelength control apparatus etc. may be accommodated in the inside of the member which joins the 1st photodiode 30 and the 2nd photodiode 40. FIG. Thereby, further miniaturization of the apparatus can be achieved.

FIG. 12 is a block diagram showing a configuration of a semiconductor laser apparatus 600 according to a modification of the fifth embodiment.
As shown in the figure, the etalon 54 has a rectangular parallelepiped shape, and is formed by obliquely cutting two corners on the side opposite to the light incident surface. The etalon 54 is formed such that the incident light is reflected twice on the cut surface and is incident on the second photodiode 40.
By configuring the etalon 54 in this way, the light passage path in the etalon 54 can be made longer than that of the semiconductor laser device 500 shown in FIG. 11 without increasing the length of the etalon 54 itself.
The operation of the semiconductor laser device 600 is the same as that of the semiconductor laser device 100. In addition to the same effects as those of the first embodiment, the device can be downsized for higher-density wavelength multiplexing.

  Further, in the semiconductor laser device 600, the first photodiode 30 and the second photodiode 40 can be mounted on a small member as shown in the figure, so that the number of parts can be reduced.

  Note that the etalon 53 or the etalon 54 may be applied to the semiconductor laser devices of the second to fourth embodiments.

Embodiment 6 FIG.
FIG. 13 is a block diagram showing a configuration of a semiconductor laser apparatus 700 according to the sixth embodiment. The same reference numerals as those in FIG. 11 represent the same components.
FIG. 14 is a block diagram showing a configuration of a semiconductor laser apparatus 800 according to the sixth embodiment. The same reference numerals as those in FIG. 12 represent the same components.

  In the sixth embodiment, a beam splitter 80 is used instead of the reflecting mirror 60 as the light separation unit. The other points are the same as in the fifth embodiment.

  Also in the sixth embodiment, the same effect as in the fifth embodiment can be obtained with respect to the mounting area of the etalon.

It is a figure which shows the structure of the semiconductor laser apparatus by Embodiment 1 of this invention. It is a figure which shows the positional relationship of the light-receiving surface of a photodiode, and a light ray. It is a figure which shows the relationship between light intensity distribution and the light-receiving range of a photodiode. It is a figure which shows the positional relationship of the light-receiving surface of a photodiode, and a light ray. It is a figure which shows the relationship between light intensity distribution and the light-receiving range of a photodiode. It is sectional drawing of the reflective mirror installed in the metal member by Embodiment 1. FIG. It is a figure which shows the structure of the semiconductor laser apparatus by Embodiment 2 of this invention. It is a figure which shows the structure of the semiconductor laser apparatus by Embodiment 3 of this invention. It is a figure which shows the structure of the semiconductor laser apparatus by Embodiment 4 of this invention. It is a figure which shows a semiconductor laser apparatus when wavelength multiplexing becomes high density. It is a figure which shows the structure of the semiconductor laser apparatus by Embodiment 5 of this invention. It is a figure which shows the structure of the modification of the semiconductor laser apparatus by Embodiment 5 of this invention. It is a figure which shows the structure of the semiconductor laser apparatus by Embodiment 6 of this invention. It is a figure which shows the structure of the modification of the semiconductor laser apparatus by Embodiment 6 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Laser diode (semiconductor laser), 20 Collimate lens (lens), 30 1st photodiode (1st photodetector), 40 2nd photodiode (2nd photodetector), 50, 51, 52 , 53, 54 Etalon (wavelength filter), 60 reflector, 61 mirror part (reflector part), 70 plane substrate (transmission plate), 80 beam splitter, 100, 200, 300, 400, 500, 600, 700, 800 Semiconductor laser device.

Claims (9)

A semiconductor laser;
A lens that is installed on the path of the backward emitted light of the semiconductor laser and converts the backward emitted light into parallel light;
A light separating unit that separates the parallel light into a first partial light corresponding to a part of a cross section thereof and a second partial light corresponding to a portion excluding the first partial light;
A first photodetector for receiving the first partial light;
A wavelength filter that transmits the second partial light;
A second photodetector for receiving the second partial light transmitted through the wavelength filter;
The wavelength of light emitted from the semiconductor laser is controlled based on wavelength information of light received by the first photodetector and wavelength information of light received by the second photodetector. Semiconductor laser device. The light separation part is a reflector,
2. The semiconductor laser device according to claim 1, wherein the parallel light is separated by changing a course of the first partial light reflected by the reflecting mirror. The light separation unit is a transmission plate having opposing surfaces formed in parallel.
2. The semiconductor laser device according to claim 1, wherein the parallel light is separated by the first partial light being transmitted through the transmission plate and translated in a path. The light separation part is a reflecting mirror part provided in a part of the wavelength filter,
2. The semiconductor laser device according to claim 1, wherein the parallel light is separated by changing the path of the first partial light reflected by the reflecting mirror portion. The first photodetector also serves as a light separation unit,
2. The semiconductor laser device according to claim 1, wherein the parallel light is separated when the first partial light transmitted through the lens is directly received by the first photodetector.   6. The semiconductor laser device according to claim 1, wherein the wavelength filter includes at least one reflection surface therein, and reflects incident light on the reflection surface. A semiconductor laser;
A lens that is installed on the path of the backward emitted light of the semiconductor laser and converts the backward emitted light into parallel light;
A light separating unit that separates the parallel light into a first partial light and a second partial light;
A first photodetector for receiving the first partial light;
A wavelength filter that transmits the second partial light;
A second photodetector for receiving the second partial light transmitted through the wavelength filter;
The wavelength filter includes at least one reflection surface therein, and reflects incident light on the reflection surface.
The wavelength of light emitted from the semiconductor laser is controlled based on wavelength information of light received by the first photodetector and wavelength information of light received by the second photodetector. Semiconductor laser device.   8. The semiconductor laser device according to claim 3, wherein the first photodetector and the second photodetector are joined to one member.   9. The semiconductor laser device according to claim 8, wherein a device for controlling the wavelength of the semiconductor laser is housed in a member for joining the first photodetector or the second photodetector.

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