JP3402778B2 - Manufacturing method of distributed feedback semiconductor laser device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor laser device, and more particularly to a method for manufacturing a semiconductor laser device used as a light source for optical communication.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional distributed feedback type (hereinafter DFB:
A sectional view of a semiconductor laser device is abbreviated as Dirtributed feed back. 6, a DFB semiconductor laser device 1 having a cavity length L has a P-type InP substrate 2, a P-type buffer layer 3, an active layer 4, a diffraction grating 5 having a lattice period S, and an N-type buffer layer 6 in that order. AR (Auti Ref which is a low reflection film formed
(lection) coat 9 is applied to the front end face, and an HR (High Reflection) coat 10, which is a high reflection film, is applied to the rear end face. Here, the anode electrode and the cathode electrode are omitted in the figure.

FIG. 7 shows an AR coat 9 and an HR coat 10.
FIG. 3 is a cross-sectional view of the DFB semiconductor laser device 1 before the treatment. Both end surfaces of the stacked semiconductor layers in FIG. 7 are cleaved surfaces, which are referred to as cleaved end surfaces 11 and 12, respectively.

Next, the operation will be described with reference to FIGS. In the conventional DFB semiconductor laser device 1, the surface coated with the AR coat 9 is the front end surface, the surface coated with the HR coat 10 is the rear end surface, and the laser light emitted from the front end surface is used as various light sources. The laser light emitted from the end face is applied to a photodiode for monitoring, etc.
It is used as monitor light for C (Automatic Power Control) driving.

In FIG. 8, the end face phase of the diffraction grating 5 is defined. In FIG. 8, the end face phase when the inter-lattice of the diffraction grating 5 is the end face (here, the rear end face is shown by a broken line in the figure) is θr = π, and the end face phase when the end of the grating is the end face is θr. = Π / 2, and the end face phase when the center of the grating is the end face is θr = 0. Further, the end face phase θf of the front end face is similarly defined.

In FIG. 9, the horizontal axis represents the resonator direction of the DFB semiconductor laser device 1, and the vertical axis represents the electric field strength, showing the electric field strength in the resonator direction. Here, the left side in FIG. 9 corresponds to the cleaved end face 12 (rear end face), and the right side corresponds to the cleaved end face 11 (front end face).

As shown in FIG. 9, the electric field strength in the resonator direction differs depending on the end face phase θr of the rear end face. When the end face phase θf of the front end face is 0, the electric field strength on the side of the cleaved facet 12 is relatively weak when θr = 0, and the cleaved facet 11
The electric field strength becomes stronger as it approaches. Also, θ
When r = π, the electric field strength on the cleaved end face 12 side is relatively strong,
The electric field strength becomes weaker as it approaches the cleaved end face 11. When θr = π / 2, there is no significant difference in the electric field strength between the cleaved end faces 11 and 12.

As described above, the cleaved end face 1 is obtained by the combination of the end face phases of the diffraction grating 5 on the cleaved end faces 11 and 12.
Since the electric field strengths at 1 and 12 are different,
The light output characteristics of the laser light emitted from the cleaved end faces 11 and 12 also differ.

Therefore, FIG. 10 shows the relationship between the end face phase of the diffraction grating 5 and the light output characteristics in the DFB semiconductor laser device 1 as (a) to (c) for each end face phase θr of the rear end face. 10A to 10C, the horizontal axis represents the drive current I and the vertical axis represents the output Pw of the emitted laser light.

FIG. 10 (a) shows the output characteristics when θf = 0 and θr = 0. The characteristic F is the output characteristic of the laser light emitted from the cleaved end face 11, and the characteristic R is the emitted light from the cleaved end face 12. The output characteristics of the laser light are shown. In FIG. 10A, the characteristic F is shown to be better than the characteristic R. That is, the cleaved end face 11 has a larger output of the emitted laser light than the cleaved end face 12.

FIG. 10B shows the output characteristic when θf = 0 and θr = π / 2, and it is shown that the characteristic F and the characteristic R are almost the same. That is, the cleaved end face 11
The output of the laser light emitted from the cleaved end face 12 is the same.

FIG. 10C shows the output characteristic when θf = 0 and θr = π, and the characteristic R is shown to be better than the characteristic F. That is, the cleaved end face 12 has a larger output of the emitted laser light than the cleaved end face 11.

However, in the conventional method for manufacturing the DFB semiconductor laser device 1, the cleaved end faces 11 and 12 are used.
AR coat 9 and HR coat 10 were applied randomly without distinction.

This is due to the simplification of the manufacturing process. FIG. 11 shows a laser device array 100 in which the DFB semiconductor laser devices 1 obtained in almost the final process of manufacture are arranged in one horizontal row. The continuous direction is the direction in which the diffraction grating 5 (shown by the broken line in the figure) extends, and the end faces in the lateral direction become the cleaved end face 11 and the cleaved end face 12.

For example, a DFB having a resonator length L of 300 μm
When about 50 semiconductor laser devices 1 are arranged in a horizontal row, the position where the diffraction grating 5 is formed in each device varies by about 0 to 2 μm. On the other hand, the diffraction grating 5
Has a grating period 7 of about 0.2 μm, and it is unknown which part of the diffraction grating 5 is located on the cleaved end face due to variations in the formation position, and the end face phases of all 50 DFB semiconductor laser devices 1 may be different. .

As described above, the AR coat 9 and the HR coat 10 are provided for the laser device array 100 which is formed by arranging the end faces of the diffraction grating 5 in a row and in a row.
From the viewpoint that it is more efficient to work in a continuous state, the AR coat 9 or the HR coat 10 is continuously applied to one of the end faces in the lateral direction.

[0017]

As described above,
The output characteristic of the DFB semiconductor laser device 1 differs depending on the combination of the end face phases of the diffraction grating 5 on the cleaved end face, and further, the output characteristic of the cleaved end faces 11 and 12 may differ in each combination.

However, in the conventional method of manufacturing a semiconductor laser device, the AR coating 9 and the HR coating 10 are applied without distinguishing the cleaved end surfaces 11 and 12, and the surface on which the AR coating 9 is uniquely applied is the front end surface and the HR. The surface provided with the coat 10 was used as the rear end surface.

Therefore, in addition to the fact that the optical output characteristics are different for each DFB semiconductor laser device 1, the AR coat 9 and the HR coat 10 are randomly applied, so that the same AR coat 9 or HR coat 10 is obtained. There is a problem in that the output of the laser light varies even on the end face subjected to the treatment.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a method of manufacturing a semiconductor laser device in which variations in the output of laser light are prevented.

[0021]

According to a first aspect of the present invention, there is provided a distributed feedback semiconductor laser device manufacturing method, wherein one end face of two output end faces from which laser light is emitted reflects the laser light. One of a high reflection film having a relatively high reflectance and a low reflection film having a relatively low reflectance is formed, and a high reflection film and a relatively low reflectance film having a relatively high reflectance of the laser light are formed on the other end face. Of the other reflective film of
In the method for manufacturing a distributed feedback semiconductor laser device having (a), before the step (a), the output of the laser light emitted from each of the one end face and the other end face under the same conditions is measured. Then, there is a step (b) of determining the magnitude relationship between the output values of the laser light from the one end face and the other end face.

A method of manufacturing a distributed feedback type semiconductor laser device according to a second aspect of the present invention is the distributed feedback according to the first aspect.
In the step (b) of the method for manufacturing the semiconductor laser device, it is determined that the output of the laser light emitted from the one end face is larger than the output of the laser light emitted from the other end face. In this case, in the step (a), the low reflection film is formed on the one end surface, and the high reflection film is formed on the other end surface.

The method for producing a distributed feedback semi <br/> conductor laser device according to claim 3, wherein according to the present invention, a distributed feedback of claim 1, wherein
In the step (b) of the method for manufacturing the semiconductor laser device, it is determined that the output of the laser light emitted from the one end face is smaller than the output of the laser light emitted from the other end face. In this case, in the step (a), the low reflection film is formed on the one end surface, and the high reflection film is formed on the other end surface.

[0024]

According to the method of manufacturing the distributed feedback semiconductor laser device according to the first aspect of the present invention, the output of the laser light emitted from each of the one end face and the other end face under the same condition in step (b). Since it has a step of determining the magnitude relationship of the output value of the laser light from one end face and the other end face, in step (a), the output of the laser light from one end face and the other end face In consideration of the characteristics, the high-reflection film and the low-reflection film can be formed so that the output does not vary on the end surface on which the reflection film having the same reflectance is formed.

According to the method of manufacturing a distributed feedback semiconductor laser device according to a second aspect of the present invention, in step (c), the output of the laser light emitted from one end face is the other. When it is determined that the output power of the laser light emitted from the end face of the, in step (a), by forming a low-reflection film on one end face, by forming a high-reflection film on the other end face, In the finally obtained distributed feedback semiconductor laser device, the output from one end face after forming the reflective film is higher,
The output from the other end can be unified so as to be lower.

According to the method of manufacturing a distributed feedback semiconductor laser device according to a third aspect of the present invention, in step (c), the output of the laser beam emitted from one end face is the other. When it is determined that the output power of the laser light emitted from the end face of the, in step (a), by forming a low reflection film on one end face, by forming a high reflection film on the other end face, Since the output from one end face after forming the reflective film is relatively large and the output from the other end face is relatively small, the finally obtained distributed feedback semiconductor laser device is Can be unified so that the difference in the output of the laser light from the end face of is reduced.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a semiconductor laser device according to the present invention will be described in order of steps with reference to FIGS. In the step shown in FIG. 1A, the P-type InP substrate 2 is used as a common substrate, and the P-type buffer layer 3, the active layer 4, the diffraction grating 5 having the lattice period S, and the N-type buffer layer 6 are sequentially formed. A plurality of DFB semiconductor laser devices 1 separated into two are formed. The cross-sectional structure thereof is the same as that of the DFB semiconductor laser device 1 shown in FIG. 6, and a duplicate description will be omitted. Next, the plurality of DFB semiconductor laser devices 1 are divided into columns to obtain a laser device array 100.

Next, in the step shown in FIG. 2, an output test is conducted by passing a drive current to each semiconductor laser device 1. FIG. 2 shows a partial cross section of the laser device array 100. Here, the common electrode G is formed on the surface of the P-type InP substrate 2, and the electrically separated separation electrode I is formed on the surface of the N-type buffer layer 6, and these are anodes after the final step. It becomes an electrode or a cathode electrode.

In FIG. 2, a test pin P for applying a drive current is in contact with the separation electrode I, and the test pin P is connected to a driving device W for driving a laser.
The common electrode G is also connected to the laser driving device W.
D that the test pin P came into contact with by applying a drive current
Since the laser light is emitted from both the cleaved end faces of the FB semiconductor laser device 1, the optical output of each cleaved end face is measured. When the optical output is measured, the test pin P is moved to the next D
The same output test is carried out by moving to the separation electrode I of the FB semiconductor laser device 1. This is performed for all DFB semiconductor laser devices 1 of the laser device array 100.

The emitted laser light may be measured first on the cleaved end face on one side over the entire DFB semiconductor laser device 1 and then on the cleaved end face on the opposite side, or on both cleaved end faces. A method of measuring at the same time may be used. In the former case, the device for measuring the output characteristics of the laser light need only be provided on one side, which is economical, and in the latter case, the measuring time can be shortened.

Next, FIG. 3 (FIG. 3 shows a laser device array 10).
0 is a plan view seen from the N-type buffer layer 6 side), the laser device array 100 is divided, and the AR coat 9 and the HR coat 10 are applied to each DFB semiconductor laser device 1. Which cleaved end face the AR coat 9 and the HR coat 10 are applied to is determined in consideration of the output characteristics of the laser light measured in the previous step. Two typical reflection film formation patterns will be described below with reference to FIGS. 4 and 5.

<First Formation Pattern> First, the first formation pattern will be described with reference to FIG. In the DFB semiconductor laser device 1 when the end face phases of the diffraction grating 5 as shown in FIG. 4A are θf = π and θr = π, the output characteristics are as follows: injection current I on the horizontal axis and vertical axis on the vertical axis. When the output Pw of the laser light emitted to is taken as shown in FIG. 4B, the characteristic F of the laser light from the cleaved end face 11 is greater than the characteristic R of the laser light from the cleaved end face 12 as shown in the output characteristic diagram. Is also good. That is, the cleaved end face 11 has a larger output of the emitted laser light than the cleaved end face 12. Therefore, as shown in FIG. 4C, an AR coat 9 which is a low reflection film is applied to the cleaved end face 11 and an H coat which is a high reflection film is applied to the cleaved end face 12.
When the R coat 10 is applied, the output characteristics of the laser beam emitted from the cleavage end face 11 on which the AR coat 9 is applied become the characteristic FA as shown in FIG. The output characteristic of the laser light emitted from the cleaved end face 12 provided with the coat 10 becomes the characteristic RH, and the difference between the characteristics becomes larger.

Similarly, in the DFB semiconductor laser device 1 in which the end face phase of the diffraction grating 5 is θf = 0 and θr = 0 as shown in FIG.
As shown in the output characteristic diagram of (f), the characteristic R is better than the characteristic F. That is, the cleaved end face 12 has a larger output of the emitted laser light than the cleaved end face 11. Therefore, as shown in FIG. 4G, the cleaved end face 12 is coated with an AR coat 9 which is a low reflection film, and the cleaved end face 1 is formed.
When HR coat 10 which is a high reflection film is applied to No. 1 as shown in FIG. 4 (h), the output characteristics of the laser beam emitted from the cleavage end face 12 provided with the AR coat 9 are as shown in FIG. The characteristic becomes the characteristic RA, and the output characteristic of the laser light emitted from the cleaved end face 11 provided with the HR coat 10 becomes the characteristic FH, and the characteristic difference becomes larger.

<Second Forming Pattern> Next, the second forming pattern will be described with reference to FIG. In the DFB semiconductor laser device 1 in the case where the end face phases of the diffraction grating 5 are θf = π and θr = π as shown in FIG. 5A, the output characteristic is shown in the output characteristic diagram of FIG. 5B. As shown, the characteristic F is better than the characteristic R. That is, the cleaved end face 11 has a larger output of the emitted laser light than the cleaved end face 12. Therefore, as shown in FIG. 5C, when the HR coat 10 which is a high reflection film is applied to the cleavage end face 11 and the AR coat 9 which is a low reflection film is applied to the cleavage end face 12, the output characteristics after the reflection film coating are obtained. Is A as shown in FIG.
The output characteristic of the laser light emitted from the cleaved end face 12 provided with the R coat 9 is the characteristic RA, and the output characteristic of the laser light emitted from the cleaved end face 11 provided with the HR coat 10 is the characteristic FH, and the reflection film. The output characteristics after coating will be reversed.

Similarly, the output characteristics of the DFB semiconductor laser device 1 in the case where the end face phases of the diffraction grating 5 are θf = 0 and θr = 0 as shown in FIG.
As shown in the output characteristic diagram of (f), the characteristic R is better than the characteristic F. That is, the cleaved end face 12 has a larger output of the emitted laser light than the cleaved end face 11. Therefore, as shown in FIG. 5G, if the HR coat 10 which is a highly reflective film is applied to the cleaved end face 12 and the AR coat P which is a low reflective film is applied to the cleaved end face 11, the output characteristics after the reflective film coating are obtained. As shown in FIG. 5 (h), the output characteristic of the laser light emitted from the cleaved end face 11 provided with the AR coat 9 becomes the characteristic FA, and the laser emitted from the cleaved end face 12 provided with the HR coat 10. The output characteristic of light becomes the characteristic RH, and the output characteristic after the reflection film coating is reversed.

As described above, according to the method for manufacturing a semiconductor laser device of the present invention, the light output characteristics may vary individually by applying the AR coat to the end face having the larger light output to form the front end face. It is possible to obtain an NFB semiconductor laser device which is unified and has a large optical output of the laser light emitted from the front end face with a high yield.

The end face with the smaller light output is AR-coated to form the front end face, and the end face with the larger light output is HR.
By applying a coat to the rear end face, the light output characteristics are unified without individual variation, not only the optical output of the laser light emitted from the front end face increases, but also the light output from the rear end face. Since it becomes relatively large, in a monitor photodiode or the like that receives the optical output of the rear end face, the monitor current obtained by photo-electric conversion becomes large, and the S / N ratio becomes high, thereby controlling the APC drive. It is possible to obtain an NFB semiconductor laser device capable of improving the property with high yield.

[0038]

According to the method of manufacturing a distributed feedback semiconductor laser device according to the first aspect of the present invention, the steps (b) are emitted from one end face and the other end face under the same condition. The output of the laser light is measured, since it has a step of determining the magnitude of the output value of the laser light from one end face and the other end face, in step (a), from one end face and the other end face In consideration of the output characteristics of the laser light, the high reflection film and the low reflection film can be formed so that the output does not vary on the end face where the reflection film having the same reflectance is formed. minute which prevents the variation of
A cloth feedback type semiconductor laser device can be obtained.

According to the method of manufacturing a distributed feedback semiconductor laser device according to a second aspect of the present invention, in the step (c), the output of the laser beam emitted from one end face is the other. When it is determined that the output power of the laser light emitted from the end face of the, in step (a), by forming a low-reflection film on one end face, by forming a high-reflection film on the other end face, In the finally obtained distributed feedback semiconductor laser device, the output from one end face after forming the reflective film is higher,
Since it is possible to unify the output from the other end face to be lower, it is possible to obtain a distributed feedback semiconductor laser device in which the output of the laser light is prevented from being varied and the output from the one end face is large. .

According to the method of manufacturing a distributed feedback semiconductor laser device according to a third aspect of the present invention, in the step (c), the output of the laser beam emitted from one end face is the other. When it is determined that the output power of the laser light emitted from the end face of the, in step (a), by forming a low reflection film on one end face, by forming a high reflection film on the other end face, Since the output from one end face after forming the reflective film is relatively large and the output from the other end face is relatively small, the finally obtained distributed feedback semiconductor laser device is since it unified from the end face of the as output difference of the laser beam is reduced, along with variations in the output of the laser light is prevented, the output difference between the laser light from one end face and another end face is small distributed feedback form half <br/> Conductor laser device You can get a good yield.

[Brief description of drawings]

FIG. 1 is a diagram showing steps of an embodiment of a method for manufacturing a semiconductor laser device according to the present invention.

FIG. 2 is a diagram showing steps of an embodiment of a method for manufacturing a semiconductor laser device according to the present invention.

FIG. 3 is a diagram showing steps of an embodiment of a method for manufacturing a semiconductor laser device according to the present invention.

FIG. 4 is a diagram showing a first pattern for forming a reflective film in an example of a method for manufacturing a semiconductor laser device according to the present invention.

FIG. 5 is a diagram showing a first pattern for forming a reflective film in an example of a method for manufacturing a semiconductor laser device according to the present invention.

FIG. 6 is a sectional view of a DFB semiconductor laser device.

FIG. 7 is a cross-sectional view of a DFB semiconductor laser device before forming a reflective film.

FIG. 8 is a diagram showing an end face phase of a diffraction grating 5.

FIG. 9 is a diagram showing an electric field intensity in a cavity longitudinal direction of a DFB semiconductor laser device.

FIG. 10 is a diagram showing a light output characteristic of a DFB semiconductor laser device.

FIG. 11 is a diagram showing a laser device array.

[Explanation of symbols]

100 laser device array, P test pin, W laser drive device, I separation electrode, G common electrode, F laser beam characteristics from cleaved end face 11, laser beam characteristic from R cleaved facet 12, FA AR coating Characteristics of laser light from the cleaved end surface 11 that has been subjected to laser irradiation, characteristics of laser light from the cleaved end surface 12 that has been subjected to RH HR coating, characteristics of laser light that has been emitted from the cleaved end surface 11 that has been subjected to FH HR coating, RA
Characteristics of laser light from the cleaved end face 12 on which the AR coating is applied.

Claims (3)

(57) [Claims] 1. A reflective film of one of a high reflective film having a relatively high reflectance of the laser beam and a low reflective film having a relatively low reflectance of the laser beam is formed on one end face of two output end faces from which laser light is emitted. Then, a distributed feedback semiconductor laser device having a step (a) of forming the other reflection film of the high reflection film having a relatively high reflectance of the laser light and the low reflection film having a relatively low reflectance on the other end face. In the method, before the step (a), the outputs of the laser beams emitted from the one end face and the other end face under the same conditions are measured, and the one end face and the other end face are measured. Step of determining the magnitude relationship of the output value of the laser light
A method of manufacturing a distributed feedback semiconductor laser device, comprising: (b). 2. In the step (b), when it is determined that the output of the laser light emitted from the one end face is larger than the output of the laser light emitted from the other end face, 2. The distributed feedback semiconductor laser device according to claim 1, wherein, in the step (a), the low reflection film is formed on the one end face and the high reflection film is formed on the other end face. Production method. 3. In the step (b), when it is determined that the output of the laser light emitted from the one end face is smaller than the output of the laser light emitted from the other end face, 2. The distributed feedback semiconductor laser device according to claim 1, wherein, in the step (a), the low reflection film is formed on the one end face and the high reflection film is formed on the other end face. Production method.