JP2001021446A - Apparatus and method for measuring semiconductor laser characteristics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and accurately measure characteristics of a semiconductor laser element by displacing a test stage to receive a laser beam emitted from the element by photodetectors of an optical output measuring unit and a polarization measuring unit. SOLUTION: A main emitting surface s1 of a semiconductor laser element s of a chip state is placed on a stage body 11 toward a photodetector 31 for measuring an optical output. This is sandwiched between a test collet 21 and the body 11, and is brought into contact with front and rear surface electrodes of the element S. A current is supplied to the element in this state, and the photodetector 31 obtains an optical output measured value from a main emitted light amount. Then, the collet 21 is raised, the body 11 is rotated at 180 degree then lowered, brought into contact with new semiconductor laser element S to drive the element S. When the laser beam of the main emitting surface s1 is incident through a lens 41 and a polarizer 42, the polarizer 42 is rotated to find an output value in which the output of a photodetector 43 becomes a maximum value (TE component) or a minimum value (TM component), and a polarization ration is obtained from a ratio of both.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an MD for recording and reproducing.
The present invention relates to an apparatus and method for measuring characteristics of a semiconductor laser device used for an optical pickup such as a magneto-optical disk or the like, and in particular, magnetizes magneto-optical effect (Kerr effect and Faraday effect), that is, linearly polarized light. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for measuring characteristics such as light output and polarization ratio of a semiconductor laser element used in an optical pickup for reading out a signal by utilizing the phenomenon that the polarization of reflected light rotates when applied to an object.

[0002]

2. Description of the Related Art FIG. 7 shows an example of a conventional device for measuring characteristics of a semiconductor laser device. Semiconductor laser element characteristic measuring device 1
At 00, the semiconductor laser device S in a chip state is mounted on the test stage 101, and the semiconductor laser device S is sandwiched between the test stage 101 and the anode formed on the front and back surfaces of the semiconductor laser device S by the test collet 102. After contact with each electrode of the cathode and the cathode, the semiconductor laser element S is energized, and the light output at that time is detected by the light receiving element 103.

However, in this light output measurement, only the light output characteristics are measured, and the polarization ratio of the semiconductor laser element S cannot be measured. Usually, the measurement of the polarization ratio of the semiconductor laser element S is performed by
The light on the main emission surface of the semiconductor laser element S is guided to a polarizing element (not shown) such as a polarizing beam splitter to be separated into TE and TM components, and the TE / TM ratio obtained by measuring the light amount of each component. Is evaluated as a polarization ratio. At this time, a lens is provided between the main emission surface of the semiconductor laser element S and the polarizing element in order to effectively guide the laser light to the polarizing element. For this reason, it is necessary to arrange a light receiving element for measuring the optical output and a light receiving element for measuring the polarization ratio on the main emission surface side of the semiconductor laser element S. A moving mechanism that makes the surface and the light receiving element face each other is required.

[0004]

On the other hand, the semiconductor laser element S has a very small side of several hundred μm on one side.
The test collet 102 is the electrode 10 of the semiconductor laser device S
In order to make contact with 4, highly accurate positioning is required, and this positioning is required in both the optical output measurement unit and the polarization ratio measurement unit. In addition, a moving function for moving the semiconductor laser element S from the light output measuring section to the polarization ratio measuring section is required, which results in an expensive and complicated measuring apparatus. In addition, when moving on the light receiving element side, the optical system provided in the polarization ratio measuring unit generates an optical axis shift or the like due to vibration during the movement, which causes a measurement error.

[0005] Therefore, in the conventional polarization ratio measurement, the semiconductor laser element S in a chip state is incorporated in a package that can be easily moved and fixed, and then the package is moved and fixed. However, when the semiconductor laser element S becomes defective in the polarization ratio measurement, the material of the package incorporated and the work of the assembly are wasted. Therefore, the semiconductor laser element S as the subject is
Is the chip state or the laser chip is Si or SiC
It is desirable that the measurement be performed in a state close to the chip, such as when it is adhered on a submount such as the above.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a measuring apparatus and a measuring method of semiconductor laser characteristics capable of measuring the characteristics of a semiconductor laser device efficiently and with high accuracy. And

[0007]

According to the present invention, a test stage on which a semiconductor laser device is mounted, a power supply unit for supplying power to the semiconductor laser device mounted on the test stage, and a power supply unit are provided. A light output measuring unit for measuring the output of the laser light emitted from the semiconductor laser element based on the power, and a polarization measuring unit for measuring the polarization of the laser light, each of which receives the laser light. Measuring a semiconductor laser characteristic, wherein the test stage has stage displacement means for displacing the test stage so that laser light emitted from the semiconductor laser element is received by each light receiving element. An apparatus is provided.

That is, the semiconductor laser device on the test stage which has been directed to the light receiving device of the light output measuring unit for measuring the output of the laser beam measures the polarization of the laser beam by displacing the test stage. Since it is directed to the light receiving element of the polarization measurement unit, once the semiconductor laser element is positioned on the test stage, there is no need to move or fix the semiconductor laser element itself afterwards. It is not necessary to incorporate the semiconductor laser element S into the package. In addition, simply by displacing the test stage, the main light-emitting surface of the semiconductor laser device and the light-receiving device can be opposed on a preset optical axis, so that highly accurate positioning is possible. Further, since the light receiving element of the polarization measuring unit and the light receiving element of the light output measuring unit are released from the restriction of being arranged on the main emission surface side of the semiconductor laser element as in the related art, the degree of freedom in the layout design of each part is increased. In addition, the size of the device can be reduced.

The test stage displacement means in the present invention means that the main emission surface of the semiconductor laser device mounted on the test stage has at least a light receiving surface of the light receiving element of the light output measuring section and a light receiving element of the light receiving element of the polarization measuring section. A mechanism that reversibly changes the posture or position of the test stage so that the test stage is alternately directed to the surface. The form of displacement of the test stage includes rotation and reciprocation on a straight line or curve in any direction.

As a configuration of the test stage displacing means according to the former embodiment, there is a configuration in which the test stage is rotated on one plane. As an apparatus configuration utilizing the displacement of the test stage due to such rotation, the light receiving surface of the light receiving element of the light output measuring unit and the light receiving surface of the light receiving element of the polarization measuring unit are arranged at two different angular positions on one plane. In addition, there is a configuration in which the test stage is alternately turned to the two angular positions by a stepping motor. These two light receiving surfaces are
By arranging them at opposing positions on one axis including the test stage, a linear and small semiconductor laser characteristic measuring device can be configured.

As the configuration of the test stage displacing means in the latter form, there is a configuration in which the test stage is reciprocated in the horizontal or vertical direction. As an apparatus configuration utilizing the displacement of the test stage due to such reciprocation, the light output surface of each light receiving element is arranged such that the light output measurement unit and the polarization measurement unit form an optical axis parallel to each other, and the test stage is configured as described above. So that they are alternately located on each optical axis of
A configuration in which the test stage is reciprocated in a direction having a predetermined angle with both optical axes, for example, in a direction orthogonal to both optical axes is given. By arranging the respective light receiving surfaces so that these two optical axes approach on one plane, it is possible to configure a compact semiconductor laser characteristic measuring device having a short overall length.

Each of the test stage and the power supply unit has an electrical connection with the semiconductor laser element, and at least one of the connections is plated with gold or a platinum group metal to provide a contact resistance. In the contact portion with the semiconductor laser element of a small order of μm,
Stable electrical contact can be obtained, and the characteristics of the semiconductor laser element can be measured with high accuracy. Examples of the platinum group metal include platinum and rhodium. The connection portion of the power supply unit is composed of a plurality of conductors, and these conductors are configured to be attached to and detached from a plurality of electrodes on one main surface of the semiconductor laser device mounted on the test stage, thereby forming electrodes. It is possible to correspond to the semiconductor laser element having different portions.

According to the present invention, the polarization measuring section has a polarization element disposed between the semiconductor laser element and the light receiving element,
An example in which the polarizing element is constituted by a polarizing beam splitter or a Glan-Thompson prism is exemplified. If the polarizing element has a Glan-Thomson prism and a rotation mechanism for rotating the prism, a more accurate polarization ratio measurement can be performed by utilizing the high extinction ratio (> 10 ³ ) of the Glan-Thomson prism. It becomes possible.

According to another aspect of the present invention, a semiconductor laser device is mounted on a test stage, power is supplied to the semiconductor laser device, and the output of laser light emitted from the semiconductor laser device is measured. A method for measuring the polarization of laser light emitted from a semiconductor laser device by rotating a test stage and supplying power to the semiconductor laser device.

In this measuring method, after measuring the output of the laser beam, the semiconductor laser device is determined based on the measurement result, and the polarization of the laser beam is measured only for the semiconductor laser device determined to be non-defective. It is possible to perform efficient measurement without waste. Further, when measuring the output of the laser light, a drive current value to be a predetermined light output at the time of the polarization measurement of the laser light is obtained in advance, and when measuring the polarization of the laser light,
By supplying power to the semiconductor laser element based on the obtained drive current value, an operation for obtaining the drive current value again in polarization measurement is omitted, so that efficient measurement can be performed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
An embodiment of an apparatus and method for measuring semiconductor laser characteristics according to the present invention will be described.

[0017] Based on FIG. 5 from Example 1 Fig 1, a first embodiment will be described. As shown in FIG. 1, a semiconductor laser characteristic measuring device 10 includes a test stage 1 that supports a semiconductor laser element S, and a power supply unit 2 that supplies power to the semiconductor laser element S mounted on the test stage 1. And an optical output measuring unit 3 for measuring the output of the laser light emitted from the semiconductor laser element S based on the supplied power, and a polarization measuring unit 4 for measuring the polarization of the laser light. .

The test stage 1 has a disk-shaped stage main body 11 having a diameter capable of mounting the semiconductor laser element S in a chip state, and stage rotating means (not shown) for rotating the stage main body 11 to a predetermined angular position. Consists of
The stage main body 11 has, on its upper surface, a connecting portion 12 made of a conductive surface and electrically connected to the back electrode of the semiconductor laser element S. Further, the semiconductor laser element S cannot swing on the conductive surface. Further, it has a fixing means (not shown) for detachably fixing.

The stage rotating means comprises a stepping motor having a rotating shaft connected to the back surface of the stage main body 11 and a stepping motor control circuit. The stage rotating means rotates the stage main body 11 to two preset angular positions. At this position, the stage main body 11 can be held so as not to swing. In this example, the two angular positions are 180 °.

The power supply unit 2 has one end of the stage main body 11.
The power supply 22 includes a power supply 22 connected to the test collet 21 at the other end, and an ammeter 23 connected in series with the power supply 22. The test collet 21 has a sharp end 21a as a connection part electrically connected to the surface electrode of the semiconductor laser element S, and is supported by an elevating mechanism (not shown) and mounted on the stage body 11. The element S can be sandwiched between the stage body 11 and the end 21a. As shown in FIG. 2, the semiconductor laser device S
Test collet 21 connected to the front and back electrodes
The surface of the test stage 1 is coated with gold plating 5.

The light output measuring section 3 comprises a light receiving element 31 for receiving laser light emitted from the main emission surface s1 of the semiconductor laser element S and an optical power meter 32 for measuring the light output received by the light receiving element 31. Become. The polarization measurement unit 4 includes a lens 41,
The polarizing element 42 and the light receiving element 43 are arranged on one optical axis,
Further, on the extension of the optical axis, the rotation axis of the test stage 1 and the light receiving element 31 of the optical output measuring unit 3 are located. The lens 41 is arranged so as to be movable on the optical axis so that the numerical aperture (Numerical Aperture, hereinafter referred to as NA) can be adjusted according to the characteristics of the semiconductor laser element S such as the optical output.
In this example, the semiconductor laser element S side has a high NA (> 0.
1), and in order to secure a distance from the light receiving element 43,
The polarizing element 42 has a lens configuration with a low NA (<0.05).

The polarizing element 42 is composed of a known Glan-Thompson prism having a rotating mechanism (not shown). The light receiving element 43 receives the laser beam passing through the polarizing element 42, and an arithmetic circuit (not shown) separates the detected optical output into an output value having a maximum value (TE component) and a minimum value (TM component), Further, the TE / TM ratio is calculated from these as the polarization ratio.

An example of a method for measuring semiconductor laser characteristics using the semiconductor laser characteristic measuring apparatus 10 of the present invention will be described below. First, as shown in FIG.
The semiconductor laser element S in a chip state, with its main emission surface s
1 is placed so as to face the light receiving element 31 for light output measurement. Next, the semiconductor laser device S is sandwiched between the test collet 21 and the stage main body 11 to obtain contacts with the front surface electrode and the back surface electrode of the semiconductor laser device S. While maintaining this connection state, the semiconductor laser element S is energized, and the main output light quantity is measured via the light receiving element 31 to obtain a light output measurement value. At this time, the drive current value Iop of the optical output for measuring the polarization ratio is simultaneously obtained. The semiconductor laser device S determined as a defective product in the optical output measurement is:
Before shifting to the polarization ratio measurement, the semiconductor laser device S is removed from the stage main body 11 and a new semiconductor laser element S is placed in the stage main body 11.
Placed on

Next, as shown in FIG. 3, the test collet 21 is raised, and then the light-receiving element 31 for measuring the light output.
Of the stage body 11 facing in the direction of the arrow 18 in the figure.
Rotate 0 °. Next, the test collet 21 is lowered to obtain a new contact with the semiconductor laser element S.
Note that, while the semiconductor laser element S is sandwiched between the test collet 21 and the stage main body 11, the stage main body 1
It is also possible to rotate the test collet 1 and the test collet 21 at the same time.

Next, the semiconductor laser device S is driven with the drive current value Iop obtained at the time of measuring the optical output. The laser light emitted from the main emission surface s1 of the semiconductor laser element S is
The light enters the light receiving element 43 through the lens 41 and the polarizing element 42. At this time, the polarization element 42 is rotated to separate the TE and TM components. As shown in FIG. 5, the separation of the TE and TM components using the Glan-Thomson prism is performed by rotating the polarizing element 42 so that the output of the light receiving element 43 becomes the maximum value (TE component) and the minimum value (TM component). Is found, and a ratio between the maximum value and the minimum value is calculated to obtain a polarization ratio. Next, based on the result of the polarization ratio measurement, the semiconductor laser element S determined to be defective is selected and eliminated.

As described above, in the above embodiment, the optical output measurement and the polarization ratio measurement of the semiconductor laser element S can be performed while the semiconductor laser element S is in a chip state, so that the quality can be efficiently determined. it can. Further, the connection portions of the test stage 1 and the test collet 21 with the electrodes of the semiconductor laser element S are plated with metal having a low contact resistance.
Even if the area is small on the order of m, stable electrical contact can be obtained, so that more accurate measurement is possible.

Embodiment 2 Embodiment 2 will be described with reference to FIG. In the first embodiment,
The semiconductor laser element S having electrodes on both front and back surfaces of the element is treated as a measurement target. In this example, a semiconductor laser element S having a connection portion having two electrodes formed on the surface of the element is measured. An apparatus and method for measuring laser characteristics will be described.

When the anode 8 and the cathode 9 of the semiconductor laser device S are both on the upper surface of the semiconductor laser device S, the measuring device 20 for semiconductor laser characteristics
And two test collets 25 corresponding to the cathode 9 and
21 is different from the semiconductor laser characteristic measuring device 10 described above. Therefore, description of the other components will be omitted.

The test collets 21 and 25 have sharp ends 21a and 25a, each of which is plated with gold. The test collets 21 and 25 are supported by an elevating mechanism (not shown) so that they do not contact each other, and are mounted on the stage body 11. The semiconductor laser element S can be sandwiched between the stage main body 11 and the two ends 21a and 25a. In addition, the power supply unit 2
A circuit including a power supply 22 and an ammeter 23 is connected to each end of the test collets 21 and 25.

When measuring the optical output of the semiconductor laser element S, the test collets 21 and 25 are lowered by the above-mentioned elevating mechanism, and the semiconductor laser element S is moved between the respective ends 21 a and 25 a and the stage body 11. The measurement is performed by obtaining contact with the cathode 9 and the anode 8. Next, when the polarization ratio is measured, the test collets 21 and 25 are rotated together with the stage main body 11 while the test collets 21 and 25 are kept in contact with the semiconductor laser element S, and the polarization ratio is measured in this state. Alternatively, after measuring the light output, the test collets 21 and 25 are once lifted to release the contact with the semiconductor laser element S, the stage main body 11 is rotated by 180 °, and then the test collet is again measured before the polarization ratio measurement. 2
The semiconductor laser device S is brought into contact with the first and second semiconductor laser elements S, and then the polarization ratio is measured while the polarities of the test collets 21 and 25 are exchanged.

[0031]

According to the present invention, the semiconductor laser device on the test stage, which has been directed to the light receiving device of the optical output measuring section for measuring the output of the laser beam, displaces the test stage to thereby generate the laser beam. Since it is directed to the light receiving element of the polarization measuring unit that measures polarization, once the semiconductor laser element is positioned on the test stage, there is no need to subsequently move or fix the semiconductor laser element itself, It becomes unnecessary to incorporate the semiconductor laser element S into a package for polarization measurement. In addition, simply by displacing the test stage, the main light-emitting surface of the semiconductor laser device and the light-receiving device can be made to face each other on a preset optical axis, so that highly accurate positioning can be performed. Further, since the light receiving element of the light output measuring section and the light receiving element of the polarization measuring section are released from the restriction of being arranged on the main emission surface side of the semiconductor laser element, the degree of freedom in the layout design of each section is increased. In addition, the size of the device can be reduced.

Further, the polarization ratio can be measured on a laser chip or a semiconductor laser device in a state where the laser chip is adhered on a submount such as Si or SiC according to the present invention. There is no need to incorporate it. For this reason, the package used for mounting the semiconductor laser element and the work required for mounting are not required, and the number of people, objects, and time required for measurement can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a plan view schematically illustrating a semiconductor laser characteristic measuring device at the time of optical output measurement according to a first embodiment of the present invention.

FIG. 2 is a plan view illustrating an electrical connection portion of the semiconductor laser device according to the first embodiment of the present invention.

FIG. 3 is a plan view schematically illustrating a semiconductor laser characteristic measuring device when the test stage is rotated according to the first embodiment of the present invention.

FIG. 4 is a plan view for explaining an outline of a semiconductor laser characteristic measuring device at the time of polarization measurement according to the first embodiment of the present invention.

FIG. 5 is a graph for explaining the procedure of polarization ratio measurement.

FIG. 6 is a plan view schematically illustrating a semiconductor laser characteristic measuring device at the time of optical output measurement according to a second embodiment of the present invention.

FIG. 7 is a plan view for explaining an outline of a semiconductor laser characteristic measuring device at the time of optical output measurement in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Test stage 2 Power supply part 3 Optical output measurement part 4 Polarization measurement part 5 Gold plating 8 Anode electrode 9 Cathode electrode 11 Stage body 21 Test collet 25 Test collet 31 Light output measuring light receiving element 42 Polarizing element 43 Polarizing ratio measuring light receiving element S semiconductor laser device s1 main emission surface

Claims (9)

[Claims] 1. A test stage on which a semiconductor laser device is mounted, a power supply unit for supplying power to the semiconductor laser device mounted on the test stage, and emission from the semiconductor laser device based on the supplied power. A light output measuring unit for measuring the output of the laser light to be measured, and a polarization measuring unit for measuring the polarization of the laser light. Each of these measuring units has a light receiving element for receiving the laser light. And a stage displacement means for displacing the test stage so that laser light emitted from the semiconductor laser element is received by each light receiving element. 2. The test stage and the power supply unit each have an electrical connection with the semiconductor laser element, and at least one of the connection is plated with gold or a platinum group metal. 2. The measuring device for semiconductor laser characteristics according to claim 1. 3. The power supply unit according to claim 2, wherein the connection unit includes a plurality of conductors, and the conductors are attached to and detached from a plurality of electrodes on one main surface of the semiconductor laser device mounted on the test stage. An apparatus for measuring the characteristics of a semiconductor laser according to the above. 4. The polarization measuring section has a polarizing element disposed between the semiconductor laser element and the light receiving element, wherein the polarizing element is:
4. The apparatus for measuring semiconductor laser characteristics according to claim 1, comprising a polarization beam splitter or a Glan-Thomson prism. 5. The semiconductor laser characteristic measuring apparatus according to claim 4, wherein the polarizing element has a Glan-Thompson prism and a rotation mechanism for rotating the prism. 6. The semiconductor laser characteristic measuring apparatus according to claim 1, wherein the stage displacement means rotates the test stage on one plane. 7. A semiconductor laser device is mounted on a test stage, power is supplied to the semiconductor laser device, the output of laser light emitted from the semiconductor laser device is measured, and then the test stage is rotated. A method for measuring the polarization of a laser beam emitted from a semiconductor laser device by supplying power to the semiconductor laser device. 8. The method according to claim 7, wherein after measuring the output of the laser beam, the semiconductor laser device is determined based on the measurement result, and the polarization of the laser beam is measured only for the semiconductor laser device determined to be non-defective. Method for measuring semiconductor laser characteristics. 9. When measuring the output of the laser light, a driving current value which is a predetermined light output at the time of measuring the polarization of the laser light is obtained in advance, and when the polarization of the laser light is measured, the obtained driving current value is obtained. 9. The method for measuring semiconductor laser characteristics according to claim 7, wherein power is supplied to the semiconductor laser element based on the value.