JP3535002B2 - Pass / fail judgment method of semiconductor laser - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser pass / fail determination method for determining pass / fail of a semiconductor laser.

[0002]

2. Description of the Related Art The quality of a semiconductor laser depends on its quality.
The drive current can be applied to the laser so that the optical output from the semiconductor laser can be obtained at a constant value, and the drive current can be discriminated based on a discrimination criterion as to whether or not the change over time of the drive current exceeds a predetermined value. . From this point of view, conventionally, (1) the maximum temperature (usually 180 ° C.) at which the semiconductor laser can oscillate from a temperature sufficiently higher than room temperature, for example, 70 ° C.
Drive current at a temperature within the range of up to about 1), and the current-optical output characteristics of the semiconductor laser are measured separately before and after the drive current is applied to the semiconductor laser. , The rate of change of the threshold current of the semiconductor laser is obtained from the measurement result of the current-optical output characteristics of the semiconductor laser before the drive current is applied to the semiconductor laser, and the drive current for the semiconductor laser is calculated. Current after energizing
The change rate of the threshold current of the semiconductor laser is obtained from the measurement result of the optical output characteristics, and the current-optical output characteristic of the semiconductor laser before the drive current is applied to the semiconductor laser is obtained from the measurement result of the semiconductor laser. The difference between the rate of change of the threshold current and the rate of change of the threshold current of the semiconductor laser obtained from the measurement result of the current-optical output characteristics after the drive current is applied to the semiconductor laser is defined as the difference of the threshold current change rate. At this time, when the difference in the threshold current change rate does not exceed a predetermined value such as 10%, it is determined that the semiconductor laser is good according to the above-mentioned criteria for determining whether the semiconductor laser is good or bad. When the value exceeds the predetermined value, the semiconductor laser is defective (defective) according to the above-mentioned criteria for judging whether the semiconductor laser is good or bad. (2) The semiconductor laser is sufficiently higher than room temperature, for example, Semiconductor laser from 70 ℃ The current of the semiconductor laser is supplied before and after the drive current is supplied to the semiconductor laser at a temperature within the range up to the maximum temperature at which laser oscillation is possible (for example, about 180 ° C.). -The optical output characteristics are measured separately and the current of the semiconductor laser before the drive current is applied to the semiconductor laser-The rate of change of the threshold current of the semiconductor laser is calculated from the results of the measurement of the optical output characteristics. In addition to obtaining the change rate of the threshold current of the semiconductor laser from the measurement result of the current-optical output characteristics after the drive current was applied to the semiconductor laser, the change rate before the drive current was applied to the semiconductor laser was calculated. Change rate of threshold current of semiconductor laser obtained from measurement result of current-optical output characteristics and semiconductor laser obtained from measurement result of current-optical output characteristic after drive current is applied to the semiconductor laser Threshold of The difference between the current change rate and the threshold current change rate is defined as the difference, and if the threshold current change rate difference exceeds a planned value such as 10%, the semiconductor laser is good if it does not exceed, and the semiconductor laser is good if it does. Is a semiconductor laser that determines that the semiconductor laser is defective.
The quality judgment method of The has been proposed.

[0003]

SUMMARY OF THE INVENTION The above-mentioned conventional method for determining the acceptability of a semiconductor laser is based on the premise that a drive current is applied to the semiconductor laser, and separate current-light before and after the application of the drive current. The output characteristics are measured, and the quality of the semiconductor laser is judged from the difference in the rate of change in the threshold current of the semiconductor laser, which is obtained from the results, respectively. Measurement of current-light output characteristics, determination of the quality of the semiconductor laser using the measurement result, other than measurement and determination, it is necessary to supply a drive current to the semiconductor laser, and it takes a long time to supply the drive current. It had the drawback that it required.

Further, in the case of the conventional semiconductor laser quality determination method, the measurement of the current-optical output characteristics before and after the drive current is applied to the semiconductor laser involves optical detection. It had the drawback that it could not be done easily and quickly. Therefore, the present invention proposes a new semiconductor laser pass / fail determination method without the above-mentioned drawbacks.

[0005]

A semiconductor laser according to the present invention.
The quality determination method of the laser is as follows: (1) The current-voltage characteristics of the semiconductor laser are measured separately under a first temperature and a second temperature higher than the first temperature, The resistance value at or near the threshold current of the semiconductor laser is obtained from the measurement result of the current-voltage characteristics under the first temperature, and the second value
From the measurement results of the current-voltage characteristics under the temperature of
Of the semiconductor laser threshold current or its vicinity and the resistance value at or near the threshold current of the semiconductor laser obtained from the measurement result of the current-voltage characteristics at the first temperature. When the difference between the threshold current of the semiconductor laser obtained from the measurement result of the current-voltage characteristics at or in the vicinity and the resistance value in the vicinity is taken as the resistance value difference, if the resistance value difference does not exceed the planned value, the semiconductor The laser is good according to the above-mentioned criteria for judging whether the semiconductor laser is good or bad,
If the resistance difference exceeds the expected value, the semiconductor laser is judged to be defective (defective) according to the above-mentioned criteria for judging whether the semiconductor laser is good or bad.
Since it has been confirmed that (2) the current-voltage characteristics of the semiconductor laser are measured under the first temperature and the second temperature higher than the first temperature. And each separately,
The resistance value at or near the threshold current of the semiconductor laser is obtained from the measurement result of the current-voltage characteristic under the first temperature, and the semiconductor laser is calculated from the measurement result of the current-voltage characteristic under the second temperature. -The resistance value at or near the threshold current of the semiconductor laser obtained by measuring the resistance value at or near the threshold current of the laser and from the measurement result of the current-voltage characteristics under the first temperature Current under −
The difference between the threshold current of the semiconductor laser obtained from the measurement result of the voltage characteristics or the resistance value in the vicinity of the semiconductor laser is taken as the resistance difference, and whether the semiconductor laser is good or bad depends on whether the difference exceeds the planned value. To determine.

In this case, the first temperature at the time of measuring the current-voltage characteristics of the semiconductor laser can be room temperature (25 ° C.), and the second temperature can be measured by the semiconductor laser. It is less than the maximum temperature at which laser oscillation is possible,
It is acceptable that the temperature has a difference of 50 ° C to 50 ° C or more.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of a pass / fail judgment method for a semiconductor laser according to the present invention will be described with reference to FIGS.

The present inventors (1) generally
The current-voltage characteristic of the laser exhibits a diode characteristic, and the current-resistance characteristic of the semiconductor laser is obtained by the first-order differential characteristic of the current-voltage characteristic of the semiconductor laser. When the current-voltage characteristics and the current-resistance characteristics of the semiconductor laser are obtained as shown by the solid line in FIG. 1, the semiconductor laser is good according to the criteria for judging the quality of the semiconductor laser. A semiconductor laser having the same configuration as that of the laser but having a defect according to the above-mentioned criteria for determining the quality of the semiconductor laser is a semiconductor laser having good current-voltage characteristics of the semiconductor laser. Based on the current-voltage characteristics of the Z, the voltage is reduced as the current increases as shown by the dotted line in FIG. 1, and the current-resistance characteristic is as shown by the dotted line in FIG. At a current above the threshold current Resistance with increasing the current,
Compared to the current-resistance characteristics of a good semiconductor laser,
(2) For a semiconductor laser that is judged to be good according to the criteria for judging whether the semiconductor laser is good or bad, the temperature of the semiconductor laser is, for example, 25 ° C. which is room temperature. When the current-voltage characteristic measured at the first temperature is obtained as shown by the solid line in FIG. 2, at the second temperature higher than the first temperature of 85 ° C. of the semiconductor laser, for example. The measured current-voltage characteristics are obtained on the basis of the current-voltage characteristics measured at the first temperature, as the voltage decreases as the current decreases, as shown by the dotted line in FIG. As for the current-resistance characteristic, as shown by the dotted line in FIG. 2, the resistance value at the threshold current or a current in the vicinity thereof is the resistance at the threshold current or its vicinity in the case of the current-resistance characteristic measured at the first temperature. Almost no change from the value (3) The semiconductor laser has the same configuration as that of the semiconductor laser of (2) described above, which is judged to be good according to the criteria for judging the quality of the semiconductor laser described above. Regarding a semiconductor laser that is defective according to the quality determination criteria of (a), the current-voltage characteristics measured at the above-mentioned first temperature of the semiconductor laser are (a) the above-mentioned determination of the quality of the semiconductor laser. Based on the current-voltage characteristic measured at the first temperature of the semiconductor laser of (2) which is considered good according to the reference, the voltage increases as the current increases as shown by the solid line in FIG. In addition, the current-resistance characteristics are determined to be good according to the criteria for determining the quality of the semiconductor laser, as shown by the solid line in FIG. The current measured at the first temperature of the Substantially the same obtained with resistive properties and, (b) semiconductor laser - first mentioned above for The
The current-voltage characteristic measured at the second temperature, which is sufficiently higher than the temperature of, is based on the current-voltage characteristic measured at the first temperature, as shown by the dotted line in FIG. It is obtained as the voltage increases, and then the voltage decreases as the current increases.
As shown by the dotted line in FIG. 3, the resistance value at or near the threshold current is significantly lower than the resistance value at or near the threshold current in the case of the current-resistance characteristic measured at the first temperature. It came to confirm that it can be obtained as a thing.

Further, from the above, (1) (i)
The current-voltage characteristics of the semiconductor laser are measured under the first temperature of 25 ° C., which is room temperature, and under the second temperature higher than the first temperature of 85 ° C., for example. And (ii) obtaining the resistance value at or near the threshold current of the semiconductor laser from the measurement result of the current-voltage characteristics at the first temperature, and (ii) the current at the second temperature. -The resistance value at or near the threshold current of the semiconductor laser is obtained from the measurement result of the voltage characteristics, and (iii)
A semiconductor obtained from the measurement result of the current-voltage characteristic at the first temperature and the resistance value at or near the threshold current of the semiconductor laser obtained from the measurement result of the current-voltage characteristic at the second temperature. When the difference between the threshold current of the laser and the resistance value in the vicinity thereof is taken as the resistance value difference, (2) if the resistance value difference does not exceed the predetermined value, the semiconductor laser is the semiconductor laser described above. If the resistance difference exceeds the expected value, it is confirmed that the semiconductor laser is a failure (defective) according to the above-mentioned semiconductor laser quality determination criteria. Came to do.

Based on the above, the embodiment of the method for determining the quality of the semiconductor laser according to the present invention is: (i) The measurement of the current-voltage characteristics of the semiconductor laser is performed at the above-mentioned first temperature of 25 ° C., for example. Under a temperature and a second temperature higher than the first temperature, which is, for example, 85 ° C. described above, each is performed separately by various methods known per se, and (ii) under the first temperature From the measurement result of the current-voltage characteristics, the resistance value at or near the threshold current of the semiconductor laser is obtained by various methods known per se, and from the measurement result of the current-voltage characteristics at the second temperature. The resistance value at or near the threshold current of the semiconductor laser is the current at the first temperature
The semiconductor laser is obtained by the same method as the method for obtaining the resistance value at or near the threshold current of the semiconductor laser from the measurement result of the voltage characteristic, and is obtained from the measurement result of the current-voltage characteristic at the first temperature. -The difference between the resistance value at or near the threshold current of the laser and the resistance value at or near the threshold current of the semiconductor laser obtained from the measurement results of the current-voltage characteristics under the second temperature is defined as the resistance value difference. Typically, such a resistance difference is obtained, and if the resistance difference does not exceed a predetermined value, if it does not exceed the predetermined value, the semiconductor laser is judged to be good according to the above-mentioned criteria for judging whether the semiconductor laser is good or bad. If it exceeds, it is determined that the semiconductor laser is defective according to the above-mentioned criterion for determining the quality of the semiconductor laser, and the quality of the semiconductor laser is determined.

The above is the embodiment of the pass / fail judgment method of the semiconductor laser according to the present invention. According to the embodiment of the method for determining the acceptability of the semiconductor laser according to the present invention, the five semiconductor lasers determined to be good according to the above-described criteria for determining the semiconductor laser and For each of the five semiconductor lasers judged to be defective (defective) according to the above-mentioned semiconductor laser discrimination criteria, the semiconductor laser can oscillate from a temperature of 70 ° C. which is sufficiently higher than room temperature. At a temperature of 85 ° C, which is within the maximum temperature (usually about 180 ° C), the optical output from each semiconductor laser is 1 for a long time such as 10,000 hours.
When current was applied so that a constant value of 0 mW was obtained and the change over time of the drive current was measured, for the semiconductor laser that was determined to be good by the above-mentioned semiconductor laser determination criteria, the drive current of As shown by the solid line in FIG. 4, the change with time hardly occurs after 5000 hours or more,
Therefore, with respect to the semiconductor laser which is estimated to have a life time of 100,000 hours or more and is judged to be non-defective (defective) according to the above-mentioned semiconductor laser judgment criteria, the change over time of the driving current is shown in FIG. As shown by the middle dotted line, the result is that the large occurrence occurs up to 5000 hours and the life time is estimated to be about 20,000 hours at most.

Also from this, the semiconductor laser according to the present invention is
According to the embodiment of the quality judgment method for the laser, it is clear that the quality of the semiconductor laser can be judged by the judgment standard of the semiconductor laser described in the section [Prior Art].

Further, in the embodiment of the method for determining the quality of the semiconductor laser according to the present invention, the respective measurements of the current-voltage characteristics of the semiconductor laser under the first temperature and the second temperature are
Whether under the first temperature or the second temperature, it can be easily carried out by a method known per se, and
It does not require a long time for the measurement, and the resistance value at or near the threshold current of the semiconductor laser can be obtained from the measurement result of the current-voltage characteristics under the first temperature. It is easy and long time is not required to obtain the resistance value at or near the threshold current of the semiconductor laser from the measurement result of the current-voltage characteristic under temperature, and it is easy and does not require a long time. Current under the first temperature −
The resistance value at or near the threshold current of the semiconductor laser obtained from the measurement result of the voltage characteristic and the threshold current at or near the threshold current of the semiconductor laser obtained from the measurement result of the current-voltage characteristic at the second temperature It is easy to obtain a resistance value difference as a difference from the resistance value without requiring a long time, and further, the resistance value difference can be seen from the current-resistance value characteristics shown in FIGS. 2 and 3. Since it can be obtained with a large value, the quality of the semiconductor laser can be easily and quickly determined from the difference in resistance value.

Therefore, according to the embodiment of the semiconductor laser pass / fail judgment method according to the present invention, the current-voltage characteristic of the semiconductor laser is measured, and the pass / fail judgment of the semiconductor laser is made by using the measurement result. In addition to measurement and discrimination, the conventional semiconductor laser
It is possible to easily determine the quality of the semiconductor laser in a short time without the need of supplying the drive current to the semiconductor laser as in the case of the quality determination method of the laser.

In the above description, the first and second temperatures at the time of measuring the current-voltage characteristics of the semiconductor laser are set to room temperature (2
5 ° C.) and 85 ° C., the first temperature is preferably room temperature (25 ° C.) because it can be easily obtained without any temperature control. Is the maximum temperature (usually 180 ° C.) at which the semiconductor laser can oscillate and is a temperature having a difference of 40 ° C. to 50 ° C. or more from the first temperature, the above-mentioned resistance difference. Can be obtained with a relatively large value,
It is not necessary to limit the temperature to 85 ° C., and even if the first and second temperatures are such temperatures, the semiconductor laser according to the present invention described above is used.
It will be apparent that the characteristics of the embodiment of the quality determination method of Z can be obtained. Besides, various modifications and changes may be made without departing from the spirit of the present invention.

[0016]

According to the method for determining the quality of a semiconductor laser according to the present invention, the current-voltage characteristics of the semiconductor laser are measured, and the quality of the semiconductor laser is determined using the measurement results. In addition to the determination, it is possible to determine whether the semiconductor laser is good or bad without the need to energize the semiconductor laser with a drive current as in the case of the conventional semiconductor laser quality determination method.
It can be done simply and quickly.

[Brief description of drawings]

FIG. 1 is a view for explaining an embodiment of a method for determining pass / fail of a semiconductor laser according to the present invention, and a current of a semiconductor laser determined to be good and a current of a semiconductor laser determined to be defective.
It is a figure which generally shows a voltage characteristic and a current-resistance characteristic.

FIG. 2 is a current-voltage characteristic at 25 ° C. and 85 ° C. of a semiconductor laser that is determined to be good, which is used for explaining an embodiment of a method for determining whether the semiconductor laser is good or bad according to the present invention. It is a figure which shows and a current-resistance characteristic.

FIG. 3 is a current-voltage characteristic at temperatures of 25 ° C. and 85 ° C. of a semiconductor laser that is determined to be defective, which is used for explaining an embodiment of a method for determining pass / fail of a semiconductor laser according to the present invention. It is a figure which shows and current-resistance characteristic.

FIG. 4 is a diagram for explaining an embodiment of a method for determining pass / fail of a semiconductor laser according to the present invention, which is a diagram showing a change with time of a drive current represented by a relationship between a drive current and an energization time with respect to the semiconductor laser.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-113359 (JP, A) JP-A-61-84888 (JP, A) JP-A-64-9682 (JP, A) JP-A-3- 131737 (JP, A) JP 50-128978 (JP, A) JP 52-156589 (JP, A) JP 62-8583 (JP, A) JP 60-186078 (JP, A) JP-A 61-290372 (JP, A) JP-A 9-186402 (JP, A) JP-A 57-48665 (JP, A) JP-A 10-160785 (JP, A) JP-A 7-115251 (JP, A) JP-A-4-184175 (JP, A) Actual development Sho 61-203575 (JP, U) Special table Sho 63-500279 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ , DB name) H01S 5/00

Claims (2)

(57) [Claims] 1. A method for measuring current-voltage characteristics of a semiconductor laser,
The measurement is performed separately under the first temperature and the second temperature higher than the first temperature, and from the measurement result of the current-voltage characteristics under the first temperature,
The resistance value at or near the threshold current of the semiconductor laser is obtained, and the resistance value at or near the threshold current of the semiconductor laser is calculated from the measurement result of the current-voltage characteristics under the second temperature. The threshold value obtained from the measurement result of the current-voltage characteristic under the first temperature and the threshold value obtained from the measurement result of the current-voltage characteristic under the second temperature and the resistance value at or near the threshold current. A semiconductor laser, characterized in that a difference between a current and a resistance value in the vicinity thereof is defined as a resistance value difference, and whether the semiconductor laser is good or bad is determined by whether or not the resistance value difference exceeds a predetermined value. How to judge pass / fail. 2. The method for determining the acceptability of a semiconductor laser according to claim 1, wherein the first temperature is room temperature (25 ° C.), and the second temperature is the maximum laser oscillation temperature of the semiconductor laser. 40 ° C to 5 ° C between the first temperature and the following.
A method for determining the quality of a semiconductor laser, which is characterized in that the temperatures have a difference of 0 ° C. or more.