JPS6058689A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To enable high output action by displacement of the position of an active layer in the undermentioned part by a method wherein the cross-sectional area of a stripe groove is varied in the neighborhood of one of two crystal planes forming the resonator of an internal stripe laser. CONSTITUTION:A current block layer 2 of the second conductivity type, a clad layer 3 and the active layer 4 of the first conductivity type, and a clad layer 5 of the second conductivity type are successively formed on a substrate 1 of the first conductivity type. The groove 6 is formed through this layer 2, and thus the resonator of the internal stripe laser is formed. Groove sections 8 with the sectional area varied are formed in the groove 6 in the neighborhood of the crystal end planes 7 of this resonator, and the position of the active layer 4 is varied in the recess part 9 of the layer in the neighborhood of the surfaces 7. A light guided to the surfaces 7 due to this rapid positional displacement of the active layer 4 is made to go straight into the layer 5. Then, high output action is enabled with a simple construction by the prevention of the breakdown of the surfaces 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] This invention is a book related to semiconductor lasers, particularly injection type semiconductor lasers called internal stripe lasers.

[Prior art]

Figures 1 (a) and (b) show conventional semiconductor lasers of the type.
). Each of these figures is a schematic plan view and a front view, and in the figures, symbol (1) represents a P-GaAi substrate, (2)
(3), (4) and (5) were laminated on the substrate (1). -G, A, current blocking layer e P-AtyGal
-yAsR2TsudsrP-A'zGal-1As active layer (x<y), and n-"zGal-zAs cladding layer (x<z), and (6) shows the current blocking N(2)
A V-shaped groove passing through the ('t) #i crystal end face, for simplicity, the bottom surface of the substrate (1) and the n-shaped rough layer (5)
The electrode provided on the top surface of is omitted. However, (2) above.

Typical thicknesses for each layer of (3), (4), and (5) are 'I Jim, 0.44 m, respectively.
0.1 fim, and 34 m.

The operation of this conventional melting process is as follows: first, when a voltage is applied with the substrate (11 side positive and the n-type rough layer (5) side negative), the current flowing from the substrate (1) and the current blocking layer ( 2) and the p-shaped rough layer (3), the reverse biased p
The -n junction narrows the groove (6). Since the p-shaped rough layer (3) is thin and the distance between the active layer (4) and the current blocking layer (2) is small, the current passing through the Ksv groove (6) can be spread greatly by one active layer (4). It passes through the n-shaped rough layer (5) and enters the V-groove (6) of the active layer (4).
) For the upper part, an n-shaped rough layer (5)
Electrons injected from the active layer (4) are radiatively recombined and emit light. Since this light is absorbed by the current blocking layer (2) and undergoes loss, the loss is small in the central part of the groove (6) where the p-type rough layer (3) is thickened, resulting in Vi(6 The effective refractive index of the part located above ) is larger than that of the periphery, and the light is guided by this refractive index distribution within the resonator formed by the two crystal end faces (force, (7)). This is amplified and leads to laser oscillation.

However, in conventional internal stripe lasers with this configuration, because the light-emitting part with high optical density is located on the active layer (4) at the crystal end face (in terms of power), it is easy to cause end face breakage and operate at high output. The disadvantage was that it was difficult to

This is based on the fact that the optical density is higher near the end face than inside, and the absorption within the active layer is large.

[Summary of the invention]

In view of these conventional drawbacks, this invention shifts the position of the active layer near the end face, and creates a structure in which light passes through a cladding layer with low light absorption and is emitted. This prevents end face destruction and, in turn, increases output power. It made the operation possible.

[Embodiments of the invention]

Examples of the internal stripe laser according to the present invention will be described below with reference to FIGS. 2 (IL) to (d) and FIGS.
, ) for a detailed explanation.

FIGS. 2(&), (b), (c), and (d) are schematic diagrams of the plane, front, [c-[e, and nd-irdvfr planes] according to the first embodiment, and the third Figure (a
), (b), (e), (d), and (e) are plane, front, and me-IHc cross sections according to the second embodiment.

These are schematic diagrams of a TIId-md cross section and a IIIe-ms cross section, and in each of these diagrams, the above-mentioned FIG. 1(a)
, The same reference numerals as in (b) indicate the same or corresponding parts.

First, in the first embodiment, the code (8) indicates the V groove (6).
A series of wide grooves (9) are formed in the vicinity of the crystal end face (7), and are recessed portions of the active layer (4) corresponding to the grooves (8) near the end face.

The structure of the first embodiment is formed in the same way as in the conventional example, with wide grooves (8) in the current blocking layer (2) of the substrate (1).
), and then the p-type rough layer (3) and the depression (
9), and an n-shaped rough layer (5).
should be allowed to grow continuously. In other words, in general, when performing the LPE method on a grooved crystal, when the thickness of the grown layer on the flat part exceeds a certain value, the grown layer on the groove aligns with the flat part and completely fills the groove. It is sufficient to utilize the fact that the time for filling the groove is approximately determined by the volume of the groove.

In this first embodiment as well, the V groove (6) is
They are similar in that light is emitted within the active layer (4) located above the waveguide, and the guided light propagates within the active layer (4) along the grooves.
In the first embodiment, a recess (9) is formed in the active layer (4) near the crystal end face (force), and in order to rapidly shift the active layer position, the K waveguide is guided from the inside of the crystal end face (7). The guided light reaches the vicinity of the end face and travels straight through the n-shaped rough layer (5).Then, the guided light is amplified by stimulated emission, as described earlier in the conventional example. Since the light intensity is highest at the edge of the crystal, when light absorption is large, this light tends to destroy the edge of the crystal.
The light generated by radiative recombination in the zXcal-XAll active layer (4) has a wavelength corresponding to the bandgap of this active layer (4), and
-AtzGal-zAs cladding layer (there is almost no absorption within 5 nm, so in the case of this first example structure, the crystal edge face with high light intensity (light absorption is poor near the force)
Therefore, breakage of the end face can be prevented, and high-output operation can be made possible.

Furthermore, in the structure of the first embodiment, the current passing through the wide groove (8) does not contribute to oscillation but increases the oscillation threshold current. As can be seen, a thick current blocking region DI is formed over a wide area of the wide groove part (8).
It is sufficient if the structure is not connected to the substrate (1).

In addition, the above-mentioned No. 1. In each of the second embodiments, a wide groove is formed, but a deep groove may be formed to change the cross-sectional area of the groove.
Although the case of G, A, /G, LA, and crystals has been described, it goes without saying that similar effects can be obtained with internal stripe lasers made of other semiconductor crystals.

〔Effect of the invention〕

As detailed above, according to the present invention, in an internal stripe laser, the cross-sectional area of the stripe groove is changed in the vicinity of at least one of the two crystal end faces forming the resonator, and the active layer in the same portion is changed. VC to displace the position of
, @ is formed, it has features such as prevention of end face destruction, thus enabling high output operation, and no need to separately form an end face protective film or an end face buried portion.

[Brief explanation of the drawing]

Figures 1 (Ik) and (b) are plane and front schematic diagrams showing internal stripe lasers according to the conventional example, and Figures 2 (a) and (
b), (e). (d) is a plan view, front view, He-Hc cross section, and nd-nd cross-sectional schematic diagram showing the internal stripe laser according to the first embodiment of the present invention;
), (e) is a plane showing the second embodiment, front view, ■e
-Ill e cross section, ■d-1d cross section, me-IrIe
It is a cross-sectional schematic diagram. (1)...First conductivity type substrate, (2)...Second conductivity type substrate
Current blocking layer of conductivity type, (3)... cladding layer of first conductivity type, (4)... active layer, (5)... cladding layer of second conductivity type, (6)... ...Groove penetrating the current blocking layer, (7)...Crystal end face, (8)...Groove portion with a changed cross-sectional area, (9)...Recessed portion of the active layer ( positionally displaced active layer). Patent applicant: Director of the Agency of Industrial Science and Technology Kawa 1) Hirobe Figure 1 Figure 2 (C) Figure 3 7 (b) (C) (d)

Claims (1)

[Claims] A semiconductor crystal substrate of a first conductivity type, a current blocking layer of a second conductivity type formed on the substrate, a groove penetrating the current blocking layer, and a groove formed on the current blocking layer filling the groove. a cladding layer of a first conductivity type, an active layer formed on the cladding layer and having a bandgap smaller than the bandgap, and a cladding layer formed on the active layer and having a bandgap larger than the bandgap. In a semiconductor laser equipped with a cladding layer of a second conductivity type having a gap, in the vicinity of at least one of two crystal end faces forming a resonator,
A semiconductor laser characterized in that the cross-sectional area of the groove is changed and the position of the active layer in the same portion is displaced.