JPS63195538A - Measuring instrument for semiconductor laser characteristics - Google Patents

Abstract

PURPOSE:To accurately and easily measure the far field pattern characteristics of a semiconductor laser by positioning the semiconductor laser and a photodetector optically. CONSTITUTION:A measuring instrument capable of measuring the far field pattern characteristics of the laser detects position shifts between semiconductor lasers 1-3 and a photodetector (photosensor) 4. Then the semiconductor lasers 1-3 are positioned by being moved in a 1st or 2nd direction in hetero-junction surfaces of the semiconductor lasers 1-3 relatively to the photosensor 4. Then, while the photosensor 4 rotated around 1st and 2nd directions relatively to the semiconductor lasers 1-3, a rotational angle-light quantity distribution is measured. Data regarding respective measured characteristics are processed properly and statistically together with temperature conditions and outputted on a CRT. Consequently, the far field pattern characteristics of the semiconductor lasers can be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for measuring the characteristics of a semiconductor laser, and particularly to an apparatus suitable for measuring far-field image characteristics.

[Conventional technology]

In recent years, semiconductor lasers have come to be widely used as light sources in various optical devices. Since semiconductor lasers can emit information signal light through direct modulation, they are particularly suitable as light sources for information-related equipment.

Incidentally, there are many types of semiconductor lasers, each with different characteristics and used for appropriate purposes. Further, even if semiconductor lasers are of the same type, the characteristics may vary slightly due to minute differences in manufacturing conditions. Therefore, when using a semiconductor laser, it is preferable to configure an optical system taking the characteristics of the laser into consideration, and when manufacturing a semiconductor laser, it is necessary to measure the characteristics of the laser for quality control. .

The characteristics of the semiconductor laser described above include the far-field pattern characteristic, which is the light intensity distribution at a distance of several micrometers or more from the light emitting end face of the chip, the optical output-current characteristic, which is the change in the output light amount with respect to the change in the input current, and the oscillation. Spectral characteristics are exemplified as the main ones.

[Problem that the invention seeks to solve]

Among the above-mentioned semiconductor laser characteristics, far-field image characteristics have been conventionally measured by (1) a method of measuring by two-dimensionally scanning and moving a photodetector on a plane parallel to the light-emitting end surface of the chip; (2) After mechanically aligning the center of the chip and the photodetector, the photodetector is aligned with the semiconductor radar in two directions, one within the heterojunction plane and the other perpendicular to the heterojunction plane.
A method of measuring by moving in two directions is used.

However, in method (1) above, the distance between the light output end face of the chip and the photodetector changes considerably as the photodetector is moved, so it is difficult to measure far-field image characteristics in a strict sense. There was a problem that it was not possible. In addition, in method (2) above, the light intensity distribution in two directions is measured after simply mechanical alignment, so these distributions are often not symmetrical with respect to the alignment position, and the far-field image characteristics are There was a problem that the measurement was not accurate.

SUMMARY OF THE INVENTION Therefore, the present invention solves the above-mentioned problems in conventional measurements of far-field pattern characteristics of a semiconductor laser, and provides a semiconductor laser characteristic measuring device that can accurately and easily measure far-field pattern characteristics of a semiconductor laser. The purpose is to

[Means for solving problems]

According to the present invention, in order to achieve the above objects, in a semiconductor laser characteristic measuring device capable of measuring far-field image characteristics of a semiconductor laser, a positional deviation between a semiconductor laser and a photodetector is detected, Based on the detection result, the semiconductor laser is moved and aligned relative to the photodetector in the first direction and/or second direction within the heterojunction plane of the semiconductor laser, and then the first Characteristics of a semiconductor radar, characterized in that the rotation angle-light area distribution is measured while rotating a photodetector relative to the semiconductor laser around the direction and around the second direction, respectively. A measuring device is provided.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of a semiconductor laser characteristic measuring device according to the present invention.

In FIG. 1, 21 is a base, a stage pace 18 is fixed on the base, and a rotation stage 17 that can rotate in two directions is mounted on the stage base. . On the side of Stage Pace 18, p4
A rotation shaft of the motor is connected to a drive force conversion mechanism 19 using gears such as a rack and pinion for converting the rotation and drive force into the rotation force of the rotation stage 17. By driving the motor 20, the rotary stage 17 can be rotated by a desired angle around an axis extending in two directions (the δ axis in the figure).

An xy moving stage is arranged on the rotation stage 17. That is, a Y stage 15 is provided on the transfer stage 17 and can be moved a desired distance in the Y direction by a laser motor 16, and a Y stage 15 is provided on the Y stage 15 and can be moved a desired distance in the An X stage 13 that can be moved a distance of is provided.

Furthermore, the moving direction of the X stage 13 and the Y stage 15
The moving direction is the moving direction in the illustrated reference state, and it goes without saying that the moving direction can be changed by rotating the rotary stage 17.

A mounting plate 12 is fixed on the base 21, and the upper part of the mounting plate is a surface along the X-Y plane.
It extends above the stage.

One end of an optical fiber 10 is fixed to the distal end of the mounting plate 12 by passing through it from above along two directions. The optical fiber 1
0 is connected to an optical spectrum analyzer 22 for measuring the oscillation spectrum of the semiconductor laser.

Furthermore, a photocell 11 is fixed to the tip of the mounting plate 12. The photocell is for measuring the optical output-current characteristics of the semiconductor radar.

Further, a mounting plate 7 is fixed on the base 21,
The mounting plate has a surface along the Y-Z plane. A mounting arm 5 is coupled to the mounting plate so as to be rotatable around the direction along the X direction.

A photosensor 4 for measuring far-field image characteristics is fixed to the upper tip of the arm 5. The photosensor 4 is arranged on the δ axis. A mounting plate 9 is integrally fixed to the mounting plate 7. A pulse motor 8 is attached to the mounting plate 9. The drive rotation shaft of the pulse motor is connected to the mounting arm 5, which allows the mounting arm 5 to be rotated at a desired angle around an axis along the X direction (referred to as the θ axis in the figure). can be done.

An angle detector 6, such as a rotary encoder or a magnescale, is attached to the mounting plate 7 and is connected to the rotation shaft of the rotational motor 8 to detect the rotation angle of the shaft.

50 is a temperature sensor for measuring the temperature near the measurement position.

FIGS. 2(a) and 2(b) show examples of masks attached to the light-receiving surface of the photosensor f4, and FIG.
) has a pinhole-shaped light passage part 41 with a diameter of about 0.2 m, and FIG. 2(b) has a slit-shaped light passage part 43 with a width of about 0.2 vm. Figure 2 (
In case b), the slits are arranged so that the direction is along the X direction.

FIG. 3 is a block diagram showing the configuration of the apparatus of this embodiment.

As shown in the figure, output signals from the photosensor 4 and the photocell 11 are input to the controller 23 via VD converters 24 and 25, respectively. Also.

The output signal from the optical spectrum analyzer 22 is sent to the controller 231'l! : Input. The output signal of the angle detector 6 is input to the controller 23.

Although not shown in FIG. 1, limit switches are provided in this embodiment for setting predetermined movable ranges of the rotation stage 17, Y stage 15, X stage 13, and mounting arm 5. Furthermore, these limit switches are shown as 27 in FIG.
The output signals from the limit switch group are input to the controller 23 via the amplifier 28.

The output signal from the temperature sensor 50 is inputted to the controller 23 via the converter 51 .

On the other hand, from the controller 23, the laser driver 29
, 30, 31. Arms motor trinok 32.33,
Control signals are output to 34, 35, CRT 36, printer 37 and block 38.

The above J? The motor drivers 32 to 35 are each
Noyals motor 14.16 for driving stage 13, Y stage 15, rotation stage 1f, and mounting arm 5
, 20.8, thereby each stage 13, 1
5.17 and the mounting arm 5 are adapted to move or rotate in a predetermined direction.

Next, the operation of the apparatus of this embodiment as described above will be explained.

In the measurement, first, the semiconductor radar 1.2.3, which is the treasure to be measured, is placed and fixed on the X stage 13. The three semiconductor radars are arranged in a line along the Y direction. Further, each semiconductor laser is arranged such that its heterojunction surface is along the X-2 plane and its light emitting end face is at the same height as the θ axis. As shown in FIG. 3, laser drivers 29-31 are connected to each semiconductor radar 1-3.

In FIG. 1, a semiconductor laser 1 is located at a position facing a photocell 11, and a semiconductor laser 2 is located at a position facing an optical fiber 10.
The semiconductor laser 3 is located at a position opposite to the lower end of the photo sensor 4 .

The optical output-current characteristics of the semiconductor radar 1 are measured as follows.

A signal is sent from the controller 23 to the laser driver 31 to drive the semiconductor laser 1. This drive is performed by flowing current in a linear manner, and as the current is gradually increased, the voltage emitted from the semiconductor radar 1 and the photocell 11V is increased.
c) Detect changes in the amount of light received and measure the light output-current characteristics. The measurement results are stored in the controller 23. The threshold current value Ith is determined from this measurement result. Ith
In the following, light emission similar to that of a normal LED is shown, but when the head direction current exceeds Ith, laser light is emitted. Then, the forward current value at a constant optical output (for example, 5 mW) is determined.

The oscillation spectrum characteristics of the semiconductor radar 2 are measured as follows.

A signal is sent from the controller 23 to the radar driver 30 to drive the semiconductor radar 2. This driving is also performed by passing current in pulses.

This current value is, for example, a forward current value (■) such that the optical output is 5 mW, and a part of the output light from the semiconductor radar 2 at this time is transmitted to the optical spectrum analyzer 22 via the optical fiber 0. Here, the oscillation spectrum is measured. The measurement results are stored in the controller 23.

The far-field image characteristics of the semiconductor radar 3 are measured as follows.

A signal is sent from the controller 23 to the laser driver 29 to drive the semiconductor laser 3. This drive also uses a pulsed current (for example, a forward current value such that the optical output is 5 mW)
This is done by flowing the water.

Here, the far-field image characteristics will be explained.

FIG. 4 is a graph showing a far-field pattern of a semiconductor laser.

In the figure, X indicates an angle from the optical axis within the heterojunction plane of the semiconductor radar, and y indicates an angle from the optical axis within a plane perpendicular to the heterojunction plane and including the optical axis. As shown in the figure, the distribution of the light intensity is slightly different between the X direction and the Y direction, but it has a substantially Gaussian distribution. If the spread angle is expressed in full width at half maximum, it is, for example, 10 to 30 degrees in the X direction and 30 to 60 degrees in the Y direction. Therefore, when measuring the far-field image characteristics, it is understood that the distribution in the X direction and Y direction passing through the peak position tRP (that is, the curves A and B in FIG. 4) may be determined.

While driving the semiconductor laser 3 arranged as shown in FIG. 1 to emit light, the pulse smoke driver 3 is
5 to drive the pulse motor 8 to rotate the mounting arm 5 around the θ axis within a range of ±50 degrees, for example. At this time, the rotation angle of the arm 50 is detected by the angle detector 6, and data on the amount of light received by the 7-point sensor 4 at each angle (for example, every 0.1 degree) is stored in the controller 23. Next, a signal is sent from the controller 23 to the nollus motor driver 34 to drive the nozzle motor 20t and rotate the rotary stage 17 by 90 degrees around the δ axis. Then, in the same manner, the mounting arm 5 is rotated around the θ axis υ, and while the rotation angle of the arm 5 is detected by the angle detector 6, the amount of light received by the photosensor 4 is detected, and the data is sent to the controller 23. Remember.

The data of the light amount distribution detected and stored through the above measurements corresponds to A' and B' in FIG. That is, semiconductor radar 3
Q in FIG.
An asymmetric distribution centered at is obtained. Therefore, in the controller 23, the angular deviation amount ΔX between the peak position Qx of the distribution A' and the distribution center Q, and the peak position Q of the distribution B'
The amount of positional deviation between the semiconductor radar 3 and the 7-point sensor 4 is calculated from the angular deviation Δy between y and the distribution center Q, and the X stage 13 and Y stage 15 are moved by an amount corresponding to the deviation fItr/c. The controller 23 sends signals to the motor drivers 32 and 33 to move them in the X and Y directions, respectively. After such a positioning operation, the mounting arm 5 is again rotated around the θ axis, and the photosensor 4 measures the light amount distribution in the X direction and the X direction. After alignment, both Q and Qx*Qy in Fig. 4 have moved to P, and in the end, in this measurement, distribution A,
B is measured.

In the above embodiment, in order to detect positional deviation, V (the entire light intensity distribution in the X direction and the
Other methods can also be used for misalignment detection and alignment in the present invention.

For example, first find the light amount distribution in the X direction, drive the X stage to correct the positional deviation in the X direction from this distribution, then find the light amount distribution in the X direction, and correct the positional deviation in the Y direction from this distribution. The Y stage may be driven as shown in FIG.

Furthermore, it is not necessarily necessary to measure the entire light amount distribution in the X direction and in the X direction for positional deviation detection and alignment. That is, as shown in Fig. 5, in the X direction, measurements are sequentially made at appropriate angles, and at this time, two adjacent measurement values are compared and the measurement point is moved to the one with the higher measurement value. For example, first, angles x1 and X! Measurement is performed at angle x3 to obtain the measured value R1 + R, and since R1 is larger than R1, next measurement is performed at angle x3 to obtain the measured value R3, and since R3 is larger than 82, the linear Measurement is performed at angle x4, and the measurement is repeated in the same manner until a measurement value that is larger than the previous measurement value is reached. When a measured value that is not larger than the previous measured value is obtained, the angle X corresponding to the peak position P can be estimated by calculation from the most recent three measured values including this measured value. Therefore, the amount of angular deviation in the X direction is determined, and based on this, the amount of positional deviation between the semiconductor laser 3 and the 7-point sensor 4 can be calculated. The same applies to the X direction.

Instead of the collective positioning based on this convenient overall positional deviation calculation, it is also possible to correct the positional deviation amount sequentially. That is, the angle to be measured is set to two predetermined positive and negative angles that are symmetrical about the δ axis, and if the two measured values obtained in the measurement are different, the X stage or Y stage is moved to a predetermined position in the direction that reduces the amount of positional deviation. Then, the same measurement is performed, and the measurement and positional deviation correction are repeated in the same manner to achieve alignment.

Although the peak position of the light amount distribution is determined when measuring the amount of positional deviation and aligning as described above, other methods are also possible. That is, as shown in FIG. 6, after measuring the entire distribution in the X direction, the angular shift amount can be determined by calculating the angle X at which the left and right areas of the distribution are equal through arithmetic processing. The same applies to the X direction.

This method has the advantage that the amount of positional deviation can be accurately measured even when the distribution has two peak values as shown in FIG.

Calculation of the amount of angular deviation and positional deviation as described above is performed using Control a-
The process is executed at La 23.

When measuring far-field image characteristics, a more accurate distribution can be obtained by using a mask like the one shown in Figure 2 (,), while a mask like the one shown in Figure 2 (b) is relatively effective as a photosensor. It becomes possible to use a material with low sensitivity and good stability.

The data regarding each characteristic measured in the manner described above is subjected to statistical processing as necessary, as well as temperature conditions.
RT 36 , printer 37 and/or plotter 38
It can be output by

In the apparatus of the above embodiment, when a signal is input from the amplifier 28 to the controller "23 indicating that any one of the movable parts has overrun beyond the allowable setting range, the vortex movable parts (X stage 13, Y stage 13, The drive signal to the pulse motor driver that drives the movement or rotation of the stage 15, rotation stage 17, and mounting arm 5 is cut off.

In the above embodiment, by appropriately moving the Y stage 15, it is possible to sequentially measure the optical output-current characteristics, oscillation spectrum characteristics, and far-field image characteristics of each of the semiconductor lasers 1 to 3.

In the above embodiment, the semiconductor laser 3 is fixed and the photosensor 4 is rotated around the θ axis in order to measure the light intensity distribution when measuring the far-field pattern characteristics, but in the present invention, the photosensor 4 is rotated around the θ axis. 4 may be fixed and the semiconductor laser 3 may be rotated around the θ axis.

〔Effect of the invention〕

According to the present invention as described above, in addition to measuring the far-field image characteristics of a semiconductor laser, it is possible to measure the far-field image extremely accurately and easily by optically aligning the semiconductor laser and the photodetector. Characteristics can be measured.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the apparatus of the present invention. FIGS. 2(a) and 2(b) are diagrams showing a mask for a photosensor. FIG. 3 is a block diagram showing the configuration of the apparatus of the present invention. FIG. 4 is a graph showing a far-field image. FIGS. 5 and 6 are graphs showing the light amount distribution. L, 2.3...Semiconductor radar, 4...Photo sensor, 6...Angle detector, 8, 14, 16.20...Pulse motor, 10...Original fiber, 11... Photocell, 13...X stage, 15...Y stage,
17... Rotating stage. Agent Patent Attorney Minoru Yamashita Child 1 Figure 2 (a) (b) Figure 4 Figure 5 Figure 6

Claims (2)

[Claims] (1) In a semiconductor laser characteristic measurement device that can measure the far-field pattern characteristics of a semiconductor laser, a positional shift between the semiconductor laser and a photodetector is detected, and based on the detection result, the semiconductor laser is connected to the photodetector. The semiconductor laser is moved and aligned in a first direction and/or a second direction within the heterojunction plane of the semiconductor laser, and then light is emitted around the first direction and around the second direction, respectively. A characteristic measuring device for a semiconductor laser, characterized in that the rotation angle-light intensity distribution is measured while rotating a detector relative to the semiconductor laser. (2) Detecting a positional shift between the semiconductor laser and the photodetector by rotating the photodetector relative to the semiconductor laser around the first direction, and then rotating the photodetector in the second direction. A photodetector is rotated relative to the semiconductor laser around a direction along the axis, and at least a part of the rotation angle-light amount distribution is measured by the photodetector during the two types of rotation.
A semiconductor laser characteristic measuring device according to claim 1.