JPH04154182A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To make it possible to separate the optical output of each laser device easily and make detectable by forming a plurality of semiconductor laser devices whose active layer comprising two quantum wells with different band gaps on the same substrate and electrically separating them. CONSTITUTION:An active layer 1 comprises two layers of a GaAs well 10 and an AlGaAs well 11. The wavelength of light equivalent to the energy gap of the well quantum 10 is 0.83mum while the wavelength of light equivalent to the energy gap of the quantum well 11 is 0.78mum. Two semiconductor laser devices 2 and 3 are formed on a GaAs substrate 5 at a 100mum span of light emitting position. Between these two laser devices is installed a groove 6 which completely separates the semiconductor layers which include the active layer in order to drive electrically each laser device independently. Optical output can be independently detected by separating the wavelength of both by means of a filter. This construction makes it possible to prepare laser array devices whose oscillation wavelength is different from each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser device that is a light source useful for increasing the speed of optical discs.

[Conventional technology]

A semiconductor laser device that integrates semiconductor laser elements that can be driven independently at intervals of about 100 μm is expected to be a light source that enables parallel processing of data on optical discs. As shown in FIG. 5, a semiconductor laser device equipped with a semiconductor laser element and a detector for monitoring optical output is equipped with one photodiode 203 on the rear emitting end face side of the semiconductor laser elements 201 and 202, and a time-resolved photodiode 203. A configuration for detecting optical output is generally known.

In addition, as a semiconductor laser device with a structure that always detects the optical output of each element independently, there is a structure shown in Figure 6 (SANYOTECI-1sICA).
L REVIEW Vol. 20 No. 1 pp. 7
1988)) known. In this figure, three semiconductor laser elements 211, 212, 21:3 have three laser beams 215, 216, .
A light guide 220 with 217 is arranged in close proximity, and an independent photodetector 221.22 is placed behind each groove of the light guide.
2.223 is placed. Since the light from each semiconductor laser element is guided to a separate photodetector by the 1215, 216, and 217 provided in the light guide 220, each element can output light independently.

Furthermore, the conventional semiconductor laser device as shown in FIG.
Proceedings of the 5th Applied Physics Association Lecture Conference (30p-Z
Q-3p8981988). In this case, two individual semiconductor laser elements 301 and 302 with oscillation wavelengths of 780 nm and 830 nm are mounted on opposite surfaces of a stem 310 and 311, so since the wavelengths of the two beams are different, a filter can be used to separate the beams. It is possible. However, it was not equipped with a photodetector.

[Problem to be solved by the invention]

However, with conventional technology, the output of each semiconductor laser element can be detected independently only by time resolution.
When used in a manner that cannot be resolved in time, for example, when a plurality of semiconductor laser elements are continuously oscillated at the same time, it is not possible to independently detect and control the optical output of each semiconductor laser element. Furthermore, in the conventional example shown in FIG. 6, it is difficult to align the semiconductor laser element and the light guide, or the light guide and the photodetector, and there is a concern that crosstalk may increase due to positional deviation. Furthermore, it was impossible to avoid increasing the size of the semiconductor laser device itself.

In addition, in the conventional example shown in Fig. 7, since the wavelengths of the two beams are different, each laser beam can be separated by using a filter, etc. However, the spacing between the semiconductor laser elements and the light emission position are the same on the semiconductor substrate. Compared to an electrically isolated structure that can be formed and driven independently, it is difficult to determine it accurately, making it difficult to use in practice.

An object of the present invention is to provide a semiconductor laser device in which the optical outputs of each laser element can be easily separated and detected.

[Means to solve the problem]

There are three types of semiconductor laser devices according to the present invention, one of which has a plurality of semiconductor laser elements formed on the same semiconductor substrate, each consisting of two quantum wells in which the active layer is a bandgap dormer, and in which they are electrically connected. It is characterized by being separated.

A second semiconductor laser device according to the present invention includes two independent photodetectors in the light output direction behind the semiconductor laser device, and has a light-receiving surface of at least one of the photodetectors.
It is characterized by providing a filter that attenuates the wavelength of light corresponding to one of the band gaps forming the active layer of the semiconductor laser element.

Further, a third semiconductor laser device according to the present invention includes the second semiconductor laser device described above.
In a semiconductor laser device, the light-receiving surface of a photodetector equipped with a filter operates at a wavelength that is attenuated from the light emitting point at the rear output end face of the laser element, which operates at a wavelength that is not attenuated by the filter. It is characterized by being located at a short distance from the light emitting point of the rear emitting end face of the laser element.

[Effect]

In a semiconductor laser device whose active layer consists of two quantum wells with different band gaps, the oscillation wavelength is switched depending on the optical output between the wavelengths corresponding to the energy gaps of the two quantum wells. Proceedings of the Joint Lecture Conference (28aSa-13p9801990)
Described in the tail. That is, during high-output operation with a high level of current injected, oscillation occurs at a wavelength nearly 50 nm shorter than during low-output operation.

These laser structures are integrated on the same semiconductor substrate, electrically separated so that they can be driven independently, and an array laser element is formed to form a semiconductor laser device. When driving one semiconductor laser element at high output for recording on an optical disk and the other semiconductor laser element at low output for reproduction immediately after recording, two semiconductor laser elements that are adjacent to each other even though they have the same laser structure operate at different oscillation wavelengths. Moreover, since they are formed on the same substrate, the spacing between the semiconductor laser elements and the position of the light emitting point can be precisely determined.

Therefore, if two photodetectors are used and one of the photodetectors is equipped with a filter that can separate these two wavelengths, the output of the detector equipped with the filter will be higher than that of the semiconductor operating at a wavelength that is not attenuated by the filter. The optical output of the laser element can be detected. Since the other photodetector detects the sum of the optical outputs of both elements, by subtracting the optical output mentioned earlier, the output of the semiconductor laser element operating at the wavelength attenuated by the filter can be detected. Light output can be detected.

Furthermore, in a two-element semiconductor laser device, when one semiconductor laser element is always operated at low output and the other at high output, the light-receiving surface of the detector equipped with a filter is located at the rear emitting end facet of a semiconductor laser element operating at a wavelength of , and at a shorter distance than the light emitting point at the rear emitting end facet of a semiconductor laser element operating at a wavelength attenuated by the other filter. This reduces the amount of light at wavelengths that are attenuated by the filter relative to the amount of light that is not attenuated by the filter that is incident on the detector having the filter, making it easier to separate the two light outputs.

〔Example〕

As a first embodiment of the present invention, FIG. 1 shows a semiconductor laser device in which two semiconductor laser elements are arranged side by side to form a laser array. As shown in FIG. 2, the semiconductor laser device used here has an active layer 1 in a GaAs well 10 and an Al
It consists of two layers of quantum wells including a GaAs well 11. G
The wavelength of light corresponding to the energy gap of the aAs quantum well 10 is 0.83 μm, and the wavelength of light corresponding to the energy gap of the AlGaAs quantum well 11 is 0.78 μm.
It has become. Two semiconductor laser elements 2.3 are formed on a GaAs substrate 5 with an interval of 100 μm between their light emitting positions. A layer 7116 is provided between the two semiconductor laser elements to completely separate the semiconductor layers including the active layer in order to electrically drive each semiconductor laser element independently. In the semiconductor laser device, the GaAs substrate 5 side is mounted on a Cu8 stem using In7. This semiconductor laser device has an oscillation wavelength of 830 nm and 78 nm with an output of 10 mW.
Switching between 0 nm and 0 nm. Write 30 on one side
mW and the other side is operated at 3 mW for reading, the laser oscillation wavelength on the write side is 830 nm and the laser oscillation wavelength on the read side is 780 nm, even though they are the same laser structure formed on the same semiconductor substrate. , their respective oscillation wavelengths differ by 50 nm. Therefore, if both wavelengths are separated using a filter, the optical output can be detected independently.

A second embodiment of the invention is shown in FIG. Of the two semiconductor laser elements 101 and 102, one semiconductor laser element has a low output of 3 mW, and the other semiconductor laser element has a low output of 30 mW.
It is driven with a high output of mW. Two Si photodiodes 105 and 106 are arranged on a plane perpendicular to the emitted light behind the rear light emitting end face of the laser array so that their light receiving surfaces are both equidistant from the rear emitting point of the laser.

And one of them, the upper photodiode 1 in the figure
The light-receiving surface of the lower photodiode 106 is equipped with a filter that attenuates light with a wavelength of 800 nm or less, and the light-receiving surface of the lower photodiode 106 is equipped with a filter that attenuates light with a wavelength of 800 nm or more. As a result, the output of the semiconductor laser device operating at a low output of 3 mW has an oscillation wavelength of 830 nm, so it is detected by the upper photodiode 105, but the light is attenuated by the filter and detected by the lower photodiode 106. On the other hand, the oscillation wavelength of the semiconductor laser device operating at a high output of 30 nW is 7.
Since the wavelength is 80 nm, it is not detected by the upper photodiode 105, but is detected by the lower photodiode 106. That is, the optical output of each semiconductor laser element can be detected individually. Furthermore, it is possible to separately detect which of the two semiconductor elements 101 and 102 has a low output and which has a high output.

FIG. 4 shows a third embodiment of the invention. Among the two semiconductor laser elements 111 and 112, the semiconductor laser element 11
1 always has a low output of 3 mW, and the semiconductor laser element 11
2 is always driven at a high output of 30 mW. A filter for attenuating wavelengths of 800 nm or less is provided at the intersection of the waveguide of the semiconductor laser element 111 extended in the rear emission direction on the plane 100 perpendicular to the emitted light in the direction of the rear emission end face of the semiconductor laser element 111. Si photodiode 10
The light-receiving surface of the Si photodiode 106 is arranged so that the light-receiving surface of the Si photodiode 106 is placed so that the light-receiving surface of the Si photodiode 106 is located at the intersection of the waveguide of the other semiconductor laser element 112 extending in the backward emission direction. Arrange it so that Since the oscillation wavelength of the semiconductor laser device 111 operating at 3 mW is 830 nm, it is detected by the photodiode 105 behind it, but it is attenuated by a filter and not detected by the photodiode 106 behind the semiconductor laser device. Furthermore, at that time, the amount of light from the semiconductor laser element 111 originally incident on the photodiode 106 is also
Since it has an angle of 107 with respect to the light emission direction of the semiconductor laser element (extension direction of the waveguide), the amount of light incident on the rear photodiode is approximately 1/10 to 1/100. Semiconductor laser element 112 operating at 30mW
The exact opposite configuration holds true for . In this way, by configuring the positions so that there is a difference not only in the attenuation by the filter but also in the amount of light incident on the photodiode, the light detection of the two semiconductor laser elements can be performed with lower Talostalk and the detection accuracy can be increased. did it.

〔Effect of the invention〕

According to the present invention, laser array elements with different oscillation wavelengths that can easily separate and independently detect each laser output can be fabricated with high accuracy on the same substrate, and it is possible to provide a semiconductor laser device that is an effective light source for increasing the speed of optical discs. did it.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention, and FIG. 2 is a diagram showing the structure of an active layer of the semiconductor laser device of FIG. 1. FIGS. 3 and 4 show the second and third embodiments according to the present invention.
5, 6, and 7 are diagrams showing conventional examples. DESCRIPTION OF SYMBOLS 1... Active layer, 2.3, 101.102... Semiconductor laser element, 5... GaAs substrate, 7... In, 8
...Cu stem, 10...GaAs quantum well, 11
...A I GaAs quantum well, 105-800 n
Si photodiode equipped with a filter with attenuation of m or less, 106...Si photodiode equipped with a filter with attenuation of 800 nm or more, 107... Angle, 111
...Semiconductor laser element driven at 3 mW, 112
...Semiconductor laser element driven at 30 mW, 20
1,202,211,212,213...Conventional semiconductor laser element, 203,211,222,223...
・Si photodiode, 215°216.217...
・Wave (waveguide), 220... light guide, 301...
Semiconductor laser element with an oscillation wavelength of 780 nm, 302...Semiconductor laser element with an oscillation wavelength of 830 nm, 10°1...Cu stem.

Claims (1)

[Claims] 1. A plurality of semiconductor laser devices whose active layers are composed of two quantum wells with different band gaps are arranged and formed on the same semiconductor substrate, and are electrically isolated. Semiconductor laser device. 2. A device comprising two independent photodetectors in the light emission direction behind the semiconductor laser device according to claim 1, and an active layer of the semiconductor laser device is formed on the light receiving surface of at least one of the photodetectors. A semiconductor laser device characterized by being provided with a filter that attenuates a wavelength of light corresponding to one of the band gaps. 3. In the semiconductor laser device according to claim 2, the light-receiving surface of the photodetector provided with a filter has a wavelength that is attenuated from a light-emitting point on the rear emitting end face of the laser element operating at a wavelength that is not attenuated by the filter. 1. A semiconductor laser device that is located in a region at a short distance from a light emitting point of a rear emitting end face of a laser element operating in the semiconductor laser device.