JPS63148692A - Multiple wave length distribution bragg reflection type semiconductor laser array - Google Patents

Abstract

PURPOSE:To contrive the enlargement of the scale and improve the yield rate by causing a wave length variable distribution bragg reflection type (DBR) laser to be divided into a plurality of blocks so that each block may be equipped with a diffraction grating having the same period within the same block and further may be equipped with the diffraction grating having a different period within the different block respectively. CONSTITUTION:In connection with a multiple wave length DBR laser array where a large number of wave length variable DBR lasers are integrated on the same substrate, wave length variable DBR lasers are divided into (n) pcs. of blocks and periods of a diffraction grating 504 of a DBR region are established by moving their periods slightly by degrees at every block. Thus, wave lengths can be set up extensively by combining such blocks. The number of blocks (n) is restricted by a gain bandwidth of an active region 501 but, if a period difference of the diffraction grating 504 between blocks is set up so that 5 nm of a wave length interval may be obtained, a maximum of around 10 blocks is available and, for example, if the wave lengths are spaced 0.5 nm apart, a large scale of the multiple wave length laser array of a maximum of around 100 wave lengths can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a multi-wavelength distributed Bragg reflection type semiconductor laser array.

[Conventional technology]

A multi-wavelength semiconductor laser array, in which a plurality of semiconductor lasers with different oscillation wavelengths are integrated on the same substrate, is a very important element in wavelength division multiplexing optical transmission systems. In order to perform large-scale multiplexing using this method, it is necessary to precisely control the oscillation wavelength of the laser serving as the light source. Conventionally,
Multi-wavelength DFB is a laser developed for this purpose.
There is a (distributed feedback type) laser array. Since the oscillation wavelength of a DFB laser is almost determined by the period of the diffraction grating formed inside the laser, the controllability of the wavelength is much better than that of a normal Fapley-Perot laser. Multi-wavelength D
In order to construct an FB laser array, it is sufficient to form diffraction gratings with slightly different periods on the same semiconductor substrate, and form a DFB laser on each grating. An example of such a multi-wavelength DFB laser array is the one reported in the Technical Research Report of the Institute of Electronics and Communication Engineers (Okuda et al. 0QE84-76). In this example, a 5-wavelength DFB laser array in the 1.3 μm band with a wavelength interval of about 5 nm is realized.

[Problem that the invention seeks to solve]

The multi-wavelength DFB laser array described above has the following problems. That is, since a DFB laser is used as a basic element, the wavelength accuracy is at most about ±0.5 nm, and it cannot be used for large-scale multiplexing.

The wavelength accuracy is mainly determined by the accuracy of the layer thickness of the active layer of the laser, but it is difficult to significantly reduce the value of ±0.5 nm. Therefore, if the wavelength interval of the laser array is set to about 10 times the wavelength accuracy, multi-wavelength DFB
In a laser array, the practical minimum wavelength interval is about 5 nm. Since the gain band of a laser is approximately 50 nm at most, the maximum number of wavelengths that can be multiplexed with such a multi-wavelength DFB laser array is approximately 10 wavelengths. Furthermore, these are cases where an ideal manufacturing process can be realized; in reality, wavelength variations occur from loft to loft or from laser array to laser array due to various causes, making it difficult to obtain a high manufacturing yield.

An object of the present invention is to improve the above-mentioned problems and provide a large-scale multi-wavelength laser array with good yield.

[Means for solving problems]

The present invention provides a multi-wavelength distributed Bragg reflection type semiconductor laser array in which a plurality of wavelength tunable distributed Bragg reflection type semiconductor lasers are integrated on the same substrate, wherein the plurality of distributed Bragg reflection type semiconductor lasers are integrated into a plurality of blocks. The plurality of distributed Bragg reflection type semiconductor lasers are divided into:
It is characterized in that the same block has diffraction gratings with the same period, and different blocks have circuit gratings with different periods.

[Effect]

The present invention is a multi-wavelength DBR laser array in which a large number of wavelength tunable distributed Bragg reflection (DBR) lasers are integrated on the same substrate, as shown in FIG. 1(a). The characteristics of individual wavelength tunable DBR lasers have already been reported in the Technical Report of the Institute of Electronics and Communication Engineers (Tomori et al. OQ E 84-81), but will be briefly explained here. FIG. 1(b) is a schematic diagram of a wavelength tunable DBR laser which is the basic element of the present invention. This laser has an active region 5019 a phase control region 502, a distributed Bragg reflection region (DBR region)
It consists of three regions 503, each of which can be independently injected with current. By biasing the active region 501 to a certain current value and controlling the currents injected into the phase control region 502 and the DBR region 503, the effective refractive index of these regions can be changed and the oscillation wavelength can be controlled. The approximate oscillation wavelength of this laser is mainly determined by the period of the diffraction grating 504 in the DBR61 region 503, but as described above, by controlling the injection current to the two regions, the period of the diffraction grating 504 can be adjusted.
Continuous wavelength control of 5 nm or more is possible near the oscillation wavelength determined by the period of 4.

Therefore, by forming a plurality of lasers into an array, even if each laser has a diffraction grating 504 with the same period, a multi-wavelength laser array having arbitrary wavelength intervals within a certain range can be realized. For example, if the wavelength interval is 0.5 nm, 1
It is possible to integrate approximately 0 wavelengths.

Therefore, in the present invention, a larger scale multi-wavelength laser array is realized using this wavelength tunable DBR laser. That is, as shown in FIG. 1(a), the above-mentioned wavelength variable D
The oscillation wavelength range can be expanded by dividing the BR laser into n blocks and making the diffraction grating period of the DBR region slightly different for each block. In Fig. 1(a), the number of lasers in each block is m
Individually. DBR laser 11-1 of the first block
m has a diffraction grating with a period Δ1, and the DB of the second block
The R lasers 21 to 2m have a diffraction grating with a period of Δ2,...
・The DBR laser n1 to nm of the n-th block has a period of A
This shows that it has one diffraction grating.

Such laser arrays allow large-scale multi-wavelength laser arrays to be realized within the laser gain band.

That is, within each block, an arbitrary wavelength can be selected within a wavelength range of about 5 nm even with diffraction gratings having the same period due to the wavelength variable function of each DBR laser. If the period of the diffraction grating is set to be slightly shifted between each block so as to obtain a wavelength interval of about 5 nm, wavelengths can be set over a very wide range by combining such blocks. The number n of blocks is limited by the gain band of the active region 501, but if the difference in period of the diffraction grating between blocks is set so as to obtain a wavelength interval of 5 nm, a maximum of about 10 blocks is possible.

Therefore, for example, if the wavelength interval is 0.5 nm, a multi-wavelength laser array with a maximum of about 100 wavelengths can be realized.

Note that in the case of a conventional DFB laser array, the wavelength fluctuates due to thermal interference between elements, but the DBR of the present invention
In the case of laser arrays, the effects of thermal interference can be compensated for by wavelength tunability.

〔Example〕

As an embodiment of the present invention, a multi-wavelength DBR laser array that integrates 25 wavelengths in the 1.5 μm band will be described.

The number of blocks is 5, and each block has 5 DBRs.
The laser was placed. Basically, the configuration is as shown in FIG. 1(a). The size of the chip is 3mm in width and 0.0mm in length.
6mm, and 25 DBR lasers are mounted on a 100mm InP substrate. The elements are arranged at intervals of cam. Each DBR
The laser wavelength interval was 1 nm.

The structure of an individual DBR laser is shown in FIG. The device consists of an active region 5011, a phase control region 502. DBR area 5
Consists of 03. The specific manufacturing method is as follows.

First, the D B Rpi area 50 on the n-InP substrate 101
A diffraction grating 504 is formed in the portion 3 by interference exposure method. The period of the diffraction grating 504 for each five blocks is 240.0.240.7.241.4.24, respectively.
2.1.242.8 nm. There are several methods for forming diffraction gratings with different periods on the same substrate, but here we used a method using a metal mask. That is, a process of exposing one period of the diffraction grating in one interference exposure using a metal mask that matches the width of each block, then shifting the mask to the next block and performing a second interference exposure. repeated. An n-TnGaAsP optical guide layer 102 is formed on the InP substrate 101 thus manufactured by the first LPE growth. n-InP buffer layer 103+
InGaAsP active layer 104. Five p-InPn chips 105 are sequentially grown. The light guide layer 102 is transparent to the wavelength of the laser.

Next, using the S i Oz mask, the phase control region 50 is
2 and the cladding layer 105 of the DBR region 503 and the active layer 10
4 and selectively removed. Next, a p-1nP cladding layer 106 is grown over the entire structure by second LPE growth.

Next, mesa etching is performed to form a buried structure, and buried growth is performed by a third LPE growth. That is, a pnpn structure for current confinement is formed. Here, a dual channel planar embedded structure was used. At this time, mesa etching and buried growth can be performed simultaneously for all elements. After finally forming the electrodes, the electrodes in the three regions and between the lasers are separated by etching. Active region 5019 Phase control region 502. The lengths of the DBR regions 503 were 150 μm, 100 μm, and 350 μm, respectively.

The chip was cut out by cleaving and mounted with the joint surface facing up.

2 of the DBR laser array manufactured as above
The characteristics of the five DBR lasers are as follows. Threshold is 20-30mA, external differential quantum momentum is 15-20%
It is. Control current, i.e. phase control region 502 and DB
The oscillation wavelength when no current is injected into the R region 503 is:
Approximately 1.545.1.550 each for each block
．． It was 1.555.1.560.1.565 μm.

Each DBR laser has a control current that allows approximately 6
Continuous wavelength tuning of r+m was possible.

Therefore, by appropriately controlling the control current, 25
DBR laser wavelength from 1.545 to 1.569 p
It was possible to set the interval to lnm within the range of m.

In the above-described embodiment, the number of blocks is 5 and the wavelength interval is 1 nm, but as described above, the number of blocks is determined by the gain band of the laser, so it can be expanded to this extent.

An embodiment of the present invention has been described above, but in the present invention, since the wavelength of each DBR laser can be arbitrarily set within a certain range, it is easy to set the wavelength interval between lasers to Inm or less. . Further, the present invention can be applied to structures other than the buried structure used here, such as Fuji waveguide type lasers, and the manufacturing method is not limited to LPE growth, but other vapor phase growth methods may be used. Further, the wavelength band is not limited to the 1.5 μm band, but may be, for example, the 1.3 μm band. Also, Ajl! GaA
Needless to say, this method is also effective for laser arrays using other materials such as s-based materials.

〔Effect of the invention〕

As described above, according to the present invention, a large-scale multi-wavelength laser
array can be realized. In one embodiment of the invention, 1.5μ
In the m-band, we demonstrated a 25-wavelength DBR laser array with a wavelength spacing of 1 nm, which is five times more integrated than a conventional multi-wavelength DBR laser array with a wavelength spacing of 5 nm and five elements. be. In addition, since each DBR laser of the present invention has a wavelength tunable function, it is possible to electrically correct variations in oscillation wavelength due to variations in layer thickness, etc., and even when a large number of elements are arrayed. A high yield rate can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the basic configuration of the present invention.
) is an overall diagram of a multi-wavelength DBR laser array, (b) is a structural diagram of an individual DBR laser, and FIG. 2 is a structural diagram of an individual DBR laser in one embodiment. 11~nm ---Individual DBR laser 101...
... Substrate 102 ... Light guide layer 103 ... Buffer layer 104 ... Active layers 105, 106 ... Cladding layer 501 ... Active region 502 ... Phase control region 503 ... ...DBRM area 504 ... Diffraction grating agent Patent attorney Yoshiyuki Iwasa Figure 1 Figure 2

Claims (1)

[Claims] (1) A multi-wavelength distributed Bragg reflection type semiconductor laser array in which a plurality of wavelength tunable distributed Bragg reflection type semiconductor lasers are integrated on the same substrate, wherein the plurality of distributed Bragg reflection type semiconductor lasers are arranged in a plurality of blocks. The plurality of distributed Bragg reflection semiconductor lasers have diffraction gratings with the same period in the same block, and diffraction gratings with different periods in different blocks. type semiconductor laser・
Array.