JPS6211796B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor laser device, and an object of the present invention is to provide a semiconductor laser device having a function of detecting changes in oscillation output more easily and with high sensitivity.

Semiconductor lasers are widely used in optical application equipment such as optical communication and video disks, but in order to stabilize the operating state of semiconductor lasers, the oscillation output must be constantly monitored and the return from the disk board, such as with video disks, must be controlled. It is necessary to detect a signal from the oscillation output generated by the interaction between light and a semiconductor laser.

Conventionally, in such a monitor, a fiber 3 is embedded in the stem 2 of a semiconductor laser 1 as shown in FIG.
The signal from the photodetector 5 was detected.

However, in such a configuration, the structure of the stem is complicated, the optical output of the semiconductor laser is inefficiently utilized because the fiber passes through it, alignment is required, and the spread of the light emitted from the semiconductor laser is difficult. Consideration must be taken to reduce the

The present invention aims to eliminate the above-mentioned drawbacks by integrating a semiconductor laser and a photodetector.

In the present invention, in a semiconductor laser device, an output detection P-N or a
-I-N junction is formed, and its output is used as p-n or p-i-n for output detection while causing stimulated radiation.
It is characterized by making it possible to monitor electrical signals from the junction.

In order to efficiently cause stimulated emission in a semiconductor laser, a light guide with an appropriately selected refractive index distribution is constructed, or a structure is adopted in which the injection carrier is locally confined. In other words, the injection carrier density and spontaneous emission energy density are increased to facilitate stimulated emission. However, even if the radiant energy density is increased locally, it will inevitably spread, so even if stimulated emission occurs, this stimulated emission will also spread. For this reason, the diameter of the laser beam can be determined by using the region where stimulated emission is attenuated to 1/e as a guide, but the attenuated portion below 1/e gradually expands. . If a pn junction or a pin junction that effectively absorbs the laser beam is formed in this widening portion, a change in the electrical signal will occur in this junction due to a change in the output of the laser beam. By effectively extracting this, the optical output of the semiconductor laser can be monitored.

Here, the wavelength of laser oscillation is determined by the energy gap and impurities of the semiconductor in the active layer, but for photodetection of this laser light, the energy of the laser light is It is desirable that the energy gap be equal to or greater than the energy gap of the semiconductor constituting the junction. Therefore,
In the present invention, it is necessary that the energy gap of the semiconductor constituting the active layer is equal to or larger than the energy gap of the semiconductor constituting the semiconductor substrate crystal. An embodiment of the present invention will be described in detail below.

<Embodiment 1> FIG. 2 shows the configuration of an embodiment of the present invention, in which a p-type semiconductor crystal substrate 22 is placed on an n-type semiconductor crystal substrate 21 (energy gap E _g1 , refractive index n ₁ ).
(Energy gap E _g2 , refractive index n ₂ ) As shown in the figure, a semiconductor crystal having a p-n junction is bonded with the part B cut out in a stripe shape and a groove. There is a substrate 11, and a part of the crystal substrate 11 has an n-type semiconductor layer 23 (energy gap E) that covers the groove and becomes a first gradient layer.
_g3 , refractive index n ₃ ), n-type or p-type semiconductor layer 24 serving as the active layer (energy gap E _g4 , refractive index
n ₄ ), p-type semiconductor layer 25 which becomes the second cladding layer
(energy gap E _g5 , refractive index n ₅ ) and an insulating thin film 26 are formed as shown in FIG. sexual electrodes, i.e. third electrode 28, second electrode 29, first electrode 27
The configuration is as follows. However, each layer is selected so that E _g1 , E _g2 ≦ E _g4 < E _g3 , E _g5 , n ₄ > n ₃ , n ₅ .

When an appropriate forward voltage is applied between the first electrode 27 and the third electrode 28, stimulated radiation (hereinafter referred to as laser oscillation) occurs, and a laser spot as shown by 10 in the figure is observed.

The oscillated laser light is inside the semiconductor crystal,
Rather than being confined only in the active layer, a portion of the laser light seeps into the groove. This light is intended to be detected at the pn junction of the semiconductor crystal substrate 11. In this case, laser light can be detected by applying a voltage between the second electrode 29 and the third electrode 28 so that a reverse bias is applied to the junction 12 of the semiconductor crystal substrate. Of course, detection is possible even with 0 bias. Here p
The role of the type semiconductor crystal substrate 22 is to concentrate the current by the first electrode 27 and further narrow the outlet by the groove B.
It plays two roles: reducing the spread of current and detecting laser light. In this case, each of the semiconductor layers 21, 22, 23,
It is also possible to have the conductivity type of 25 completely reversed.

FIG. 3 shows another embodiment of the present invention, and shows a semiconductor crystal substrate in which an i-type layer 31 and a p-type layer 32 with a low impurity concentration are stacked in place of the p-type semiconductor substrate layer 22 in the embodiment of FIG. 30 was used. In this case, the junction to be photodetected is p-
The N junction was used, but in this embodiment it is a pin junction, which improves response speed, increases reverse breakdown voltage, and makes laser current concentration more efficient.

FIG. 4 shows a third embodiment of the present invention.
A semiconductor laser array is constructed by arranging a plurality of structures of the embodiment shown in FIG. 2 in rows of cells.

Two sets of devices A and B corresponding to the embodiment of FIG. 2 are constructed using the n-type semiconductor substrate 21 of the embodiment of FIG. 2 as a common substrate. The symbols A and B in the figure only indicate that they belong to the devices A and B, respectively, and the meanings of each symbol are the same as those in the embodiment of FIG. 2. If a voltage is applied between the electrodes 27A and 28, the semiconductor laser A oscillates, and its optical output can be extracted between the electrodes 29A and 28 as an electrical signal. If a voltage is applied between the other electrodes 27B and 28, the optical output of the semiconductor laser B will be
This means that it can be detected from between 9B28.

FIG. 5 shows yet another embodiment, in which the method of taking out the photodetecting electrode is improved from the embodiment of FIG. That is, in semiconductor lasers, the electrode close to the active layer is usually attached to the mounting stem, so the configuration shown in FIG. 2 may be inconvenient in some cases. Therefore, it is necessary to take out the photodetecting electrode on the same side of the n-type crystal substrate 21 as the ohmic electrode, as shown in FIG. 5a.
Now, if a p-type layer 51 is formed in the n-type semiconductor substrate 21 that reaches the p-type semiconductor substrate crystal 22 of the p-n junction necessary for photodetection, and an ohmic electrode 52 is formed thereon, the electrode shown in FIG. 2 is formed. The electrode corresponds to No. 29. Furthermore, in the figure b, an n-type semiconductor substrate crystal 21
When a part of the p-type semiconductor substrate crystal 22 is removed and an ohmic electrode 54 is formed thereon, this becomes an electrode corresponding to the electrode 29 in FIG. 2. The principle is the same as the embodiment shown in FIG. 2, except that the electrodes for obtaining the photodetection signal are located between the electrodes 28 and 52 and between the electrodes 28 and 54, respectively. With this configuration, even if the electrode 27 side is face-down bonded, each of the electrodes 28, 52, or 54 can be taken out with a wire by wire bonding.

As described above, the present invention provides a semiconductor laser device having at least a first cladding layer, an active layer, and a second cladding layer. Alternatively, a pin junction is formed, and the output can be detected while stimulating radiation, and it has the advantage that changes in oscillation output can be easily detected with high sensitivity.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional semiconductor laser;
3, 4, and 5a and 5b are cross-sectional views of a semiconductor laser device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 10... Stimulated radiation region, 21... N-type semiconductor crystal substrate, 22... P-type semiconductor crystal substrate, 23... First cladding layer, 24... Active layer, 25... Second cladding layer, 26... Insulation Body thin film, 27...first electrode, 28...third electrode, 29...second electrode.

Claims (1)

[Scope of Claims] 1. In a semiconductor laser device that includes at least a first cladding layer, an active layer, and a second cladding layer on a semiconductor substrate crystal and performs stimulated emission, the semiconductor laser device includes at least a first cladding layer, an active layer, and a second cladding layer on a semiconductor substrate crystal. The semiconductor region has a semiconductor region which is omitted at least immediately below the region where stimulated radiation occurs, and is provided so that a part of the semiconductor region extends into the region where stimulated radiation occurs. 1. A semiconductor laser device that detects stimulated radiation light as an electrical signal by using a semiconductor substrate crystal and a semiconductor substrate crystal. 2 Claim 1 characterized in that a pn junction is formed between the semiconductor region and the semiconductor substrate crystal
The semiconductor laser device described in . 3 P-i-n between the semiconductor region and the semiconductor substrate crystal
The semiconductor laser device according to claim 1, characterized in that a junction is formed. 4 Claims characterized in that the energy gap of the semiconductor constituting the active layer is equal to or larger than the energy gap of the semiconductor constituting the p-n junction or pin junction. The semiconductor laser device according to item 2 or 3.