JPS6123384A - Multi-wavelength semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a multi-wavelength semiconductor laser which has excellent coupling efficiency and can be controlled independently, by forming resonator mirrors by diffraction lattices having periods corresponding to the respective oscillation wavelengths of a plurality of active layers and a common cleavage surface, respectively. CONSTITUTION:Active layers 14a, 14b which serve as light-emitting areas have respective compositions and energy band gaps, which correspond to their respective oscillation wavelengths. Diffraction lattices 23a, 23b having periods which respectively correspond to the oscillation wavelengths are provided on a waveguide layer 13. A multi-wavelength semiconductor laser having a combination of various kinds of wavelength can be formed by appropriately selecting a composition for each of the active layers 14a, 14b of the first and second semiconductor lasers and a period for each of the diffraction lattices 23a, 23b. An etched surface 26 is formed by chemical etching or the like in such a manner that the surface 26 slants with respect to the end face of the waveguide layer 13 so as not to constitute a reflecting surface. A reflection preventing film may be provided on a cleavage surface 25 which serves as a resonator mirror.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a multi-wavelength semiconductor laser that oscillates at multiple wavelengths.

[Prior art]

The structure of a conventional multi-wavelength semiconductor laser is shown in FIG.

゛Figure 1 shows W, T, T sang (Appl.
, Phys., Lett.

to 1.3B, pp, 441-443, 1980
) is a perspective view of a semiconductor laser emitting multiple wavelengths shown in FIG. In FIG. 1, 1 is an n-type GaAs substrate, 2
-1゜2-2.2-3.2-4 are each n-type cr+A
lx rGaz-x(A s , Aug
2 Gat-x2'As.

A, llx 3 Gat-13As, klx 4 G
at-14AS (7) active layer, 3 is n-type A11y 1
Gat-y As (however, '!> l++ +
X2 + 13 + X4) (1) Cladding layer,
4 is a Zn diffusion region, 5 is a p-type region, 6 is an n-side electrode, 7 is a p-side electrode, and 8 is a 5i02 insulating layer.

Next, the operation will be explained.

When a voltage is applied with the p-side electrode 7 being positive and the n-side electrode 6 being negative, a current flows from the p wall region 5 of the Zn diffusion region 4 to the four active layers 2-1.2-2.2-3°2- It flows horizontally through the pn junction of 4. The cladding layer 3 is the active layer 2-
Since the energy band gap is larger than that of active layers 2-1 to 2-4, carriers are confined in active layers 2-1 to 2-4. The current is divided almost equally into the four active layers 2-1 to 2-4, but the AM component ratio of the four active layers 2-1 to 2-4 is 11.
Since +l12+I+3+×4 are different,
Laser oscillation with wavelengths λ1 to λ4 occurs at the pn junction of each active layer 2-1 to 2-4, and multi-wavelength laser oscillation light is obtained.

Conventional multi-wavelength lasers are configured as shown below, so it is difficult to independently control the optical output of laser light of any wavelength (active layer), and the light emitting part has a laminated structure. Therefore, it has the disadvantage that it is difficult to obtain the same coupling effect for light of any wavelength when coupling it to an optical fiber.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by arranging active layers with different oscillation wavelengths on two waveguide layers on the same optical axis, each The present invention provides a multi-wavelength semiconductor laser that can independently control the optical output of laser light.

An embodiment of the present invention will be described below with reference to the drawings.

[Embodiments of the invention]

FIGS. 2 and 3 are a side sectional view and a sectional view taken along the line A-A of the embodiment of the present invention.

In these figures, 11 is an n-type InP substrate.

12 is n-type InPn chip 9, 13 is n-type InGa
AsP waveguide layer, 14a, 14b InGaAsP active layer, 15 InGaAsP buffer layer, 16 p-type I
nPn chiku 9fu, 17 is p type c7) InGaAsP key? -/p layer, 18 is p-type InP block layer, 19 is n
type InP block layer, 20 is an n-side electrode, 21a, 21
b is a p-side electrode, 22 is a 5in2 insulating layer, 23a, 23b
is a diffraction grating, 24a and 24b are lead wires, 25 is a cleavage plane, and 26 is an etched plane.

An active layer 14a serves as a light emitting part of a semiconductor laser.

14b is provided on the waveguide layer 13 with diffraction gratings 23a and 23b each having a composition and an energy band gap corresponding to the wavelength of the oscillated light, and a period length corresponding to the oscillating wavelength.

Next, the operation of this invention will be explained.

When a voltage is applied to the p-side electrode 21a and the n-side electrode 20 of the first semiconductor laser and a current is injected, the active layer 14a emits light, and this light is coupled and propagated to the waveguide layer 13. Since a laser resonator is constituted by the diffraction grating 23a of the waveguide layer 13 and the cleavage plane 25, the oscillation wavelength of the semiconductor laser is determined by the period length of the diffraction grating 23a.

Similarly, in the second semiconductor laser, when a voltage is applied to the p-type electrode 21b and the n-type electrode 20 and a current is injected, the active layer 14b
The emitted light oscillates at a wavelength determined by the diffraction grating 23b. The cleavage plane 25 as a resonator mirror has a first
It is shared with the semiconductor laser of 1st. The oscillation light of the second semiconductor laser is extracted from the waveguide layer 13 at the cleavage plane 25 to the outside.

Therefore, the first. By applying separate modulation signal currents to the second semiconductor laser, it can be used as a light source for optical wavelength multiplex communication. Since these two wavelengths of light are emitted from the same point, they can be easily coupled to an optical fiber.

Furthermore, since the diffraction gratings 23a and 23b are used in the resonators, monochromaticity and temperature characteristics are excellent.

By making the energy O bandgap of the waveguide layer 13 larger than the energy Φ bandgap of any of the active layers 14a and 14b, it can be made transparent to laser oscillation light. As the oscillation wavelength becomes shorter,
Since the light energy hν becomes close to the energy bandgap of the waveguide fi13 and the waveguide loss increases,
Diffraction grating 2 of the shorter wavelength of the two semiconductor lasers
3a is preferably placed near the output end (cleavage plane 25).

1st. Active layer 14a of the second semiconductor laser.

By selecting the composition of grating 14b and the period of diffraction gratings 23a and 23b, multi-wavelength semiconductor lasers with various wavelength combinations can be constructed. Furthermore, the etched surface 26 is processed to be oblique to the end surface of the waveguide layer 13 by chemical etching or the like so that it does not become a reflective surface. In this case, cleavage plane 2
5 may be provided with an antireflection film.

FIG. 4 shows another embodiment of the present invention, in which a diffraction grating 23b may be provided above the waveguide layer 13. With this configuration as well, FIG.

There is an effect similar to that of the embodiment shown in FIG.

FIG. 5 shows still another embodiment of the present invention (7)-
t', active layers 14a, 14b and diffraction grating 23a.

This is a case where the positional relationship of 23b is changed, and in this case as well, the same effects as in the embodiments shown in FIGS. 2 and 3 can be obtained.

In addition, in the second embodiment, the case of two wavelengths has been described, but the present invention is also effective in the case of two or more wavelengths.
This can be achieved by increasing the number of 3b.

Furthermore, in the above example, a semiconductor laser made of an InP-based material with an oscillation wavelength of 1.2 to 1.6 gm is shown, but the same applies to a GaAs-based material with an oscillation wavelength of 0.7 to 0.9 pm. configuration can be realized.

〔Effect of the invention〕

As described in detail above, the multi-wavelength semiconductor laser of the present invention has a plurality of active layers having different compositions and oscillation wavelengths disposed close to a waveguide layer on the same substrate, each of which is independently In a multi-wavelength semiconductor laser that includes an electrode that enables current injection and that allows light of a plurality of different oscillation wavelengths to be extracted from the waveguide layer, a period length corresponding to each oscillation wavelength of the plurality of active layers is set. Since the diffraction gratings with the same optical axis were formed above or below the waveguide layer, and each diffraction grating and the common cleavage plane constituted a resonant mirror, multiple active It has the advantage that layers can be placed close to each other, a multi-wavelength semiconductor laser with good coupling efficiency and independently controllable can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional side view showing a conventional multi-wavelength semiconductor laser, FIG. 2 is a side cross-sectional view showing a multi-wavelength semiconductor laser according to an embodiment of the present invention, and FIG. 3 is a cross-sectional side view taken along line A-A in FIG. The sectional view, FIG. 4, and FIG. 5 are side sectional views showing other embodiments of the present invention. In the figure, 11 is an InP substrate, 12 is a cladding layer, 13 is a waveguide layer, 14a, 14b are active layers, 15 is a buffer layer,
16 is a cladding layer, 17 is a cap layer, 18.19 is a block layer, 20 is an n-side electrode, 21a, 21b are p-side electrodes, 22 is an insulating layer, 23a, 23b is a diffraction grating, 24a,
24b is a lead wire, 25 is a cleavage surface, and 26 is an etched surface. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa (2 others) Figure 1 Figure 2 C Figure 3 Figure 4 Figure 5 Procedural amendment (voluntary) 3. Relationship with the case of the person making the amendment Patent applicant address Tokyo 2-2-3 Marunouchi, Chiyoda-ku Name (601) Mitsubishi Electric Co., Ltd. Representative Hitoshi Katayama 4, Agent 5, Drawing subject to amendment 6, Details of amendment Drawing Nakaon 2, Figure 3 attached. Correct it as follows. Figure 2 Figure 3

Claims (4)

[Claims] (1) It has a plurality of active layers arranged close to the waveguide layer on the same substrate and have compositions different from each other in oscillation wavelength, each of which has an electrode capable of independently injecting a current, and In the multi-wavelength semiconductor laser, in which light having different oscillation wavelengths can be extracted from the waveguide layer, a diffraction grating having a period length corresponding to each oscillation wavelength of the plurality of active layers is provided above or below the waveguide layer. A multi-wavelength semiconductor laser, characterized in that each of the diffraction gratings and a common cleavage plane constitute a resonant mirror. (2) The multi-wavelength semiconductor laser according to claim (1), wherein the energy bandgap of the waveguide layer is larger than the energy bandgaps of the plurality of active layers. (3) The multi-wavelength semiconductor laser according to claim (1), wherein the plurality of diffraction gratings are of a distributed reflection type. (4) Any one of claims (1) to (3), characterized in that the diffraction grating on the shorter wavelength side among different oscillation wavelengths has a shorter resonator length. The described multi-wavelength semiconductor laser.