JPS61255085A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To make the oscillation wavelength of laser variable widely and continuously by providing a charping diffraction grating on the overall surface of a waveguide and injecting a current from plural electrodes on the surface of a clad layer. CONSTITUTION:When a current is injected to electrodes 9, 10...13, according to that, the wavelength dependence of valid reflectance of the regions under the electrodes 9...13 of a charping diffraction grating 32 is determined. Laser oscillation is done by the wavelength near the maximum value of the product of those reflectance characteristics. Accordingly, a laser oscillator can be tuned continuously by changing a quantity of the current injected into the electrodes 9...13. Also as the charping diffraction grating 32 is arranged on the surface of a waveguide layer 3 and the electrodes 9...13 are formed on the surface of a clad layer 5, the tuning range of laser oscillation wavelengths can be enlarged. Furthermore, there is no need of cleaving the edge planes in this laser device, so that the manufacture process becomes simple and the yeild can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser device, and particularly to a semiconductor laser device whose laser oscillation wavelength can be controlled by injection current.

[Prior Art] Fig. 3 shows, for example, the conventional technology shown in the document ``DFB-DC-PBHLD with Phase Control Mechanism,'' ``DFB-DC-PBHLD with Phase Control Mechanism'' 1 is a cross-sectional view showing a wavelength tunable semiconductor laser device. First, the configuration of this device will be explained. In the figure, an active layer 2 for laser oscillation is formed on the upper surface of a substrate 1.
is formed. A waveguide layer 3 is formed on the upper surface of the active layer 2 for propagating light generated in the active layer. On the left side of the upper surface of the waveguide layer 3, a diffraction grating 31 consisting of unevenness with an equal pitch is built along the waveguide layer.The diffraction grating 31 reflects the light propagating through the waveguide layer 3. A cladding layer 5 is formed on the upper surface of the waveguide layer 3 to confine light generated in the active layer 2 to the waveguide H3 and the active layer 2. 11. Active layer 2. The right end faces of the waveguide W3 and the cladding layer 5 form a cleavage plane 8,
This cleavage plane reflects the light propagating through the waveguide [13 and active layer 2]. The diffraction grating 31 and the cleavage plane 8 serve as a so-called optical resonator for laser oscillation.

A phase control electrode 6 and a light output control lNi 17 are formed on the upper surface of the cladding layer 5. A current is injected into the phase control electrode 6, thereby controlling the phase of the light propagating through the waveguide layer 3. A current is injected into the light output control electrode 7, thereby controlling the laser oscillation.

Next, the operation of this device will be explained. The light generated in the active layer 2 propagates through the waveguide layer 3 and the active layer 2, and passes through the diffraction grating 3.
1 and is reflected by the open face 8 and oscillates as a laser. At this time, if the current injected into the phase control electrode 6 is changed, the phase of the light propagating through the waveguide layer 3 changes, the laser oscillation conditions change, and the laser oscillation wavelength changes. Further, at this time, if the current injected into the optical output control electrode 7 is changed, the optical output of the laser oscillation is changed.

[Problems to be solved by the invention] In the conventional wavelength tunable semiconductor laser device, it is necessary to separate the end facets, which complicates the manufacturing process and lowers the yield. Since the laser oscillation wavelength is changed by controlling the phase of the light, there is a problem in that the wavelength tuning range is narrow. moreover,
There is also the problem that semiconductor laser devices having such a cleavage plane are unsuitable for optoelectronic integrated circuits.

This invention was made to solve the above-mentioned problems, and it has a simple manufacturing process, high yield, and can continuously change the laser oscillation wavelength over a wide range, and uses a cleavage plane. The purpose of this invention is to obtain a semiconductor laser device suitable for optoelectronic integrated circuits that are difficult to manufacture.

[Means for Solving the Problems] In the semiconductor laser device according to the present invention, a diffraction grating consisting of unevenness with a varying pitch is built into the active layer or the waveguide layer, and a plurality of electrodes are arranged at intervals on the upper surface of the cladding layer. By injecting current into each of these electrodes, the effective reflectance of the diffraction grating is controlled and the laser oscillation wavelength is changed.

[Function] In this invention, by changing the injection current ratio between the respective electrodes, the effective reflectance of the region below each electrode of the diffraction grating changes, thereby changing the laser oscillation conditions. Laser oscillation wavelength changes.

〔Example] Embodiments of the present invention will be described below with reference to the drawings.

In the description of this embodiment, the description of parts that overlap with the description of the conventional technology will be omitted as appropriate.

FIG. 1 shows a distributed feedback type (DFB) which is an embodiment of this invention.
) is a cross-sectional view showing a laser type semiconductor laser device. First, the configuration of this device will be explained. In the figure, an active layer 2 is formed on the upper surface of a substrate 1, and a waveguide layer 3 is formed on the upper surface of an active layer 112. On the upper surface of the waveguide layer 3, a Chirb diffraction grating 32, that is, a diffraction grating consisting of concavities and convexities whose pitch changes continuously along the waveguide layer 3, is built over the entire area. The Chirb diffraction grating 32 reflects the light propagating through the waveguide layer 3 and serves as an optical resonator for laser oscillation. A cladding layer 5 is formed on the upper surface of the waveguide layer 3, and electrodes 9, 10, 11, 12.degree. 13 are formed on the upper surface of the cladding layer 5 and are spaced apart from each other.

A current is injected into each electrode 9.10.11.12.13,
This changes the effective reflectance of the Chirb diffraction grating 32.

Next, the operation of this device will be explained. First, before explaining the operation of this device, for convenience of explanation, only two electrodes, namely electrode 9 and electrode 10, are formed on the upper surface of the cladding layer 5, and the electrode The pitch of the unevenness is △ at the bottom of the electrode 10.
The operation of a semiconductor laser device modeled as "C" will be explained, in which a diffraction grating with a concavo-convex pitch of Δ2 is built on the top surface of the waveguide layer 3. Current It (11≠■2)
Injected with
as shown by the solid line.

The region between the region of pitch Δ and the region of pitch A2, that is, both ends of the lower region between electrode 9 and electrode 10 are two regions having reflectance characteristics shown in FIG. 2(a). You will be caught. Therefore, the wavelength dependence of the effective reflectance in the li region is the product of these two reflectance characteristics, as shown by the broken line in Figure 2 (a), and the laser oscillates at a wavelength near its maximum value. I will do it. In addition, the electrode 9
For example, if we inject 21 I z into the electrode 9 and 111 into the electrode 10, then if we change the current 1fCu injected into the electrode 10, the effective area of the area below the electrode 9 and the area below the electrode 10 of this diffraction grating will be The wavelength dependence of the reflectance is shown by the solid line in FIG. 2(b).

Therefore, electrode 9 and electrode 101 of this diffraction grating! The wavelength dependence of the effective reflectance in the region below l is shown in Figure 2 (
It becomes the product of these two reflectance characteristics as shown by the broken line in b), and the laser oscillates at a wavelength near its maximum value, and the laser oscillation wavelength is the same as in the case of FIG. 2(a). As described above, by changing the amount of current injected into the electrodes 9 and 10, the laser oscillation wavelength can be continuously tuned.

Next, the operation of the semiconductor laser device shown in FIG. 1 will be explained based on the same concept as above.

When a current is injected into each electrode 9, 10.11.12.13, each electrode 9.10 of the chirped diffraction grating 32 responds accordingly.
, 11, 12, 13 is determined, and the laser oscillates at a wavelength near the maximum value of the product of these reflectance characteristics. Therefore, each electrode 9.1
By changing the amount of current injected at 0.11.12°13, the laser oscillation wavelength can be continuously tuned. Furthermore, in this embodiment, a chirped diffraction grating 32 is built on the top surface of the waveguide layer 3, and a plurality of electrodes 9, 10, 11, 12 degrees 13 are formed on the top surface of the cladding layer 5, so that the conventional semiconductor Compared to laser devices, the tuning range of laser oscillation wavelength can be expanded.

Further, since this semiconductor laser device does not require separation of the end facets, the manufacturing process is simplified and the yield is increased, so that the cost of this semiconductor laser device can be reduced.

Furthermore, since this semiconductor laser device uses a chirped diffraction grating to reflect light and does not use a cleavage plane, it is possible to integrate a large number of this semiconductor laser device on the same substrate, making it suitable for optoelectronic integrated circuits. Become.

In addition, although the above embodiment shows the case where a chirp diffraction grating is built into the waveguide layer, the chirp diffraction grating may be built into the active layer, or the chirp diffraction grating may be built into the substrate close to the active layer. In these cases as well, the same effects as in the above embodiment can be achieved.

Furthermore, in the above embodiment, a chirped diffraction grating is shown as the diffraction grating built on the top surface of the waveguide 1, but a diffraction grating in which the pitch of the concavities and convexities changes step by step may also be built; A diffraction grating that changes irregularly may be fabricated, and the same effects as in the above embodiment can be achieved in these cases as well.

Further, in the above embodiment, the normal vertical direction 1! Although the DFB laser with a current injection structure has been shown, a lateral current injection structure,
and Eva Ref. R J, Appl, Phys.

The present invention is also applicable to the TJS type DFB laser shown in 45.2785 (1974) J.

[Effects of the Invention] As described above, according to the present invention, a diffraction grating consisting of unevenness with a varying pitch is built into the active layer or the waveguide layer, and a plurality of electrodes are formed at intervals on the upper surface of the cladding layer. However, by injecting current into each of these electrodes, the effective reflectance of the diffraction grating is changed and the laser oscillation wavelength is changed, making the jaw construction process simple, high yield, and applicable over a wide range. It is possible to obtain a semiconductor laser device that can continuously change the laser oscillation wavelength and is suitable for optoelectronic integrated circuits in which it is difficult to use cleavage planes.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a semiconductor laser device according to an embodiment of the invention. FIGS. 2(a) and 2(b) are diagrams showing the wavelength dependence of the effective reflectance of a diffraction grating in a modeled semiconductor laser device. FIG. 3 is a sectional view showing a conventional wavelength tunable semiconductor laser device. In the figure, 1 is a substrate, 2 is an active layer, 3 is a waveguide layer, and 5
is a cladding layer, 6 is a phase control electrode, 7 is a light output control electrode, 8 is a cleavage plane, 9, 10° 11, 12, 13 are electrodes, 31 is a diffraction grating, and 32 is a Chilb diffraction grating. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claim] A distributed feedback laser comprising: a substrate; an active layer formed on the upper surface of the substrate for laser oscillation; and an active layer formed on the upper surface of the active layer for laser oscillation; a waveguide layer for propagating light transmitted through the active layer or the waveguide layer; A diffraction grating made of unevenness whose pitch changes along the waveguide layer is formed on the upper surface of the waveguide layer to confine the light generated in the active layer in the waveguide layer and the active layer. a cladding layer formed on the upper surface of the cladding layer at intervals from each other,
A semiconductor laser device comprising: a plurality of electrodes into which current is injected so as to control an effective reflectance of the diffraction grating for the light propagating through the active layer or the waveguide layer and change the laser oscillation wavelength.