JPS6215879A - Semiconductor laser arrays device - Google Patents

Abstract

PURPOSE:To enable realization of high-output and stable oscillation in the single 0 deg. phase mode, by providing a plurality of first active waveguides optically coupled together and a second wave guide intersecting them at a predetermined angle and optically coupling the first and second waveguides by means of a periodic structure having a period substantially equal to the wavelength. CONSTITUTION:A plurality of first active waveguides 28 optically coupled together and a single or plurality of second active or inactive waveguides 29 intersecing the first active waveguides 28 are provided. The first and second waveguides 28 and 29 are optically coupled together by means of a periodic structure having a period substantially equal to or less than the wavelength. For example, an N-AlGaAs clad layer 22 is formed on the (001) face of an N-GaAs substrate 21, and a grating 23 is formed on the surface of the clad layer 22 in parallel to the <010> direction of the crystal. Then, an N-AlGaAs optical waveguide 24, a P-AlGaAs active layer 25, a P-AlGaAs clad layer 26 and an N<+>-GaAs contact layer 27 are grown. An electrode material is deposited on both surfaces by evaporation and alloyed. Thereafter, mesa stripe active waveguides 28 and 29 extending in two different directions so as to intersect each other are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to semiconductor laser array devices, particularly those capable of stably oscillating up to high output in a mode in which light waves in all active waveguides are coupled in the same phase (0° phase mode). The present invention relates to a semiconductor laser array device.

BACKGROUND ART Semiconductor lasers are used as light sources for optical discs, laser printers, local measurement systems, etc., and there is currently a strong desire for higher output.

However, current semiconductor lasers have a single active waveguide structure, and are useful for applications such as window effects and edge reflectance control.
The limit is about 70 μW.

There is active research and development into semiconductor laser arrays having a plurality of active waveguides. This semiconductor laser array can emit high-output light in a single thin beam by selectively oscillating a super mode (0° phase mode) in which charging different phases in all waveguides are synchronized.

However, in conventional semiconductor laser arrays, as mentioned above, complete optical phase matching in all waveguides is not achieved. Specifically, for example, the optical phase between adjacent waveguides is shifted by 180°. Super mode with (180
A first phenomenon occurs in which the output light is emitted in the form of two beams with a certain angle of divergence. The structure of a semiconductor laser array in which this first phenomenon is observed will be described with reference to FIGS. 5 and 6. First, on the (001) plane of the P-GaAs substrate 1, a 0.7μ thick n” Af o, +Gao, sA
The s current narrowing N2 and the nGaAs surface protection N3 having a thickness of 0.1 #l+o are grown in this order. A liquid phase epitaxial growth method is used as a growth method. Next, three linear grooves 4 are formed in parallel to reach the P-GuAs substrate 1 by penetrating each of these layers 2.3. The valley width D1 of the grooves 4 is 4 μm, the depth D2 is approximately 1 μm, and the distance D3 between the centers of each groove 4 is 5 μm. Further, this groove 4 was perpendicular to the (110) plane which is the end face of the laser resonator. On this wafer 1, 0.0.
2μ thick P-Af. ,42Ga,.

S, AS clad N5 and 0.08 μm thick P or n
A, I: o, :4Gao, 56As active layer 6 and 0.8#m n A A' O+42G so+s
sA s cladding layer 7 and 1.5 μmW n+-GaA
The s-contact layer 8 is grown continuously in this order.

Since the groove 4 is completely filled with the P-type cladding layer 5, the top surface of the P-type cladding layer 5 is flat. Thereafter, resistive electrodes were formed on both sides of Ueno 1 by vapor deposition, alloyed, and then cleaved at the (011) plane to form a semiconductor laser array. The optical electric field distribution and far-field image of the oscillation beam of the semiconductor laser array 9 fabricated in this way are shown by lines L1 and L2 in FIG. It is clear that the temporal phase difference of light between them is 180°.

The 180° phase mode selectively oscillates when the semiconductor laser array 9 has a multiple parallel loss waveguide structure as in the conventional example.
This is because the threshold gain of the 180° phase mode is the lowest because light absorption exists in the optical coupling region between each active waveguide. This can also be understood from theoretical calculations.

From the waveguide analysis, the center-to-center distance of the waveguide is set to 5μI,
A graph showing the dependence of the threshold gain of the three supermodes on the lateral refractive index difference of the semiconductor laser array 9 with the three-element parallel loss waveguide structure is shown as line L3 in FIG.
, L 4 , and L 51 respectively, and the above 1
Although it is known both theoretically and experimentally that it is possible to selectively and stably oscillate the 80° phase mode, the Pt51 phenomenon described above appears in the laser probe application. In addition to the first phenomenon, 0° phase or 1
The phenomenon @2 occurs in which oscillation occurs in a supermode other than the 80° phase mode and the output light is emitted as multiple beams, or two or more supermodes overlap in a state of non-interference and the beam becomes thicker. Phenomenon 3 may occur.

Each of these first to third phenomena is inconvenient from the standpoint of using the semiconductor laser 7-ray. ...-It is necessary for super mode oscillation and for the output light to be a single beam.

Further, in order to improve such drawbacks, a semiconductor laser array 10 having a real refractive index waveguide structure that eliminates loss in the coupling region has been prototyped, and an example thereof is shown in FIG. n
- On the (001) plane of the GaAs substrate 11, a 0.8 μm thick n-A, l'xGa, -xA s graph,
layer 12 and 0.1μ thick n or P-AJ! yGa
, -yAs active layer 13 and 0.8μ-thick P -A J
xG a 1-X A 3 cladding layer 14; 1.
A P"-GaAs contact layer 15 with a thickness of 0 μm is continuously grown in this order. The growth method is MOCVD.
In addition to the method, molecular beam epitaxial method (MBE), liquid phase epitaxy (LPE), etc. can be applied. Thereafter, resistive electrodes were formed on both sides of the sea urchin. Using conventional photolithography technology and reactive ion beam etching (RIBE) technology on the thus prepared substrate,
Three parallel mesa stripe waveguides 16 were formed.

The width D11 of this waveguide 16 is 3μI, and the distance between centers D12
is 4 μm, and the height Dis is 1.5 μm.
110> parallel to the direction. In other words, the thickness D14 of the P-cladding layer 14 in the mesa stripe except for the waveguide 16 was etched to a thickness of 0.3 .mu.all. The laser resonator 17 faces the (110) plane of the crystal! Formed by opening. Further, the length Dis of the semiconductor laser array 10 is approximately 250 μm.

When the oscillation transverse modes of the four-body laser array 10 having a real refractive index waveguide structure fabricated in this manner were observed, it was found that a plurality of supermodes coexisted. This current situation is thought to be due to the following reasons. In the lossy waveguide structure described above, the light absorption in the coupling region is large, so the 180°
Whereas the phase mode was selected, in the semiconductor laser array 10 made of 4V real refractive index waveguide, there is no light absorption in the coupling region, so the threshold straightness of all supermodes allowed by the element structure is selected. The gain becomes equal to Banmage. Therefore, all supermodes oscillate simultaneously. In this way, the output beam of the semiconductor laser array 10 that oscillates in a mixture of a plurality of supermodes has a thickness several times the diffraction limit, which poses a serious problem in practice.

Problems to be Solved by the Invention The purpose of the present invention is to solve the above-mentioned technical problems and provide a semiconductor laser array device that can achieve high output and stable oscillation with a single 0° phase modulus V. It is to be.

! Means for Solving the Problem The present invention provides a plurality of first active waveguides that are optically coupled to each other;
a single or a plurality of second active or inactive waveguides intersecting the first active waveguide, the first and second waveguides having a period on the order of a wavelength or less; This is a semiconductor laser array device characterized by optical coupling due to its structure.

According to the present invention, the first plurality of active waveguides are optically coupled to each other, the second waveguide intersects the first waveguide at a certain angle, and the first and second waveguides are optically coupled to each other. Since the second waveguide is optically coupled with a periodic structure having a period comparable to the wavelength, it is possible to achieve high output and stable oscillation in a single 20° phase mode.

Embodiment FIGS. 1 and 2 are diagrams for explaining a semiconductor laser array device 19 according to the present invention.

First, on the (001) plane of the n-GaAs substrate 21, MO'
CVD method! 0°8μ using MBE method, LPE method, etc.
A thick n-A7xGa+-xAs cladding layer 22 is grown. Next, I FfB l of this cladding layer 22:
A grating 23 is formed parallel to the <010> direction of the N product. This grating 23 has a width of 11 μI and 11 mm, as shown by the notches in FIG. Vertical width 7μ
Form only within the rectangular area of the octopus. Furthermore, the period of the grating 23 is 1/1 of the wavelength within the element of the laser oscillation light.
Up to 2 will be selected. Next, using the wafer with such a grating as a substrate, 0,3
N-AJ of μ-yong thickness! a zGa1-zAs waveguide layer 24;
0.1 μml + 7 of 11 or P-Anoy-Gal-
yAs activity I25 and 0.8 μf thick P-A, f
i'XGa1-xAs cladding layer 26 and 1°0μ+6
A layer of n''-GaAs: l tact/1 m27 is grown continuously in this order. A resistive electrode material is deposited on the growth surface and the back surface of the substrate 21, and the layer is grown at 450°C for 2
Alloying is carried out in vacuum for ~3 minutes. Thereafter, using photolithography technology and RIBE technology, mesa stripe active waveguides 28 and 29 that intersect with each other in two directions are formed with a width d1 = 3 μm, a center distance d2 = 4 μm, and a height d3.
= 1.5 μm. Here, active waveguide 2
8 is parallel to the <110> direction of the crystal, and the active waveguide 29 is parallel to the <110> direction of the crystal. Then, rectangular portions 30 of the waveguides in these two directions are perpendicular to each other.
was controlled to match the portion where the grating 23 was previously formed. Finally (110) plane 31 and (iio)
By cleaving the surfaces 32, the four mutually orthogonal surfaces were made into laser resonator end surfaces. Also (110
) A dielectric multilayer film is deposited on the surface 32, and its reflectance is set to 96.
%.

In the semiconductor laser array device 19 having such a structure, the active waveguide 28 as the main element and the active waveguide 29 as the sub-element are optically coupled by the grating 23.

Here, since the grating 23 was formed under the above-mentioned conditions, the light wave changes in the 90° direction and the equiphase front becomes flat. That is, the equiphase front when the light wave in the active waveguide 29, which is the sub-element, enters the active waveguide 28, which is the main element, is flat, and the three active waveguides 28
It can be seen that the light wave phase relationship in the 0° phase mode is the same as in the 0° phase mode.

In the normal real refractive index waveguide type semiconductor laser 7-ray 10 that does not have sub-elements as shown in the conventional example, there is almost no difference in the threshold gain of each super mode, and several modes coexist. Oscillation is observed in the state. However, according to the present invention, by injecting the optical wave of the O゛ phase mode from the active waveguide 29, which is a sub-element, through the grating 23, into the real refractive index parallel waveguide 28, which is a main element, only the 0° phase mode can be used. It becomes possible to lower the threshold gain of . That is, grating 23
By optimizing the coupling efficiency and the end face reflectance of the laser resonator, it is possible to selectively oscillate only the 0° phase mode.

According to the experimental results of the present inventor, the characteristics of the semiconductor laser array device 19 manufactured in this way using Cr are as follows:
It was found that the single 0° phase mode oscillates up to 100 IIW at an oscillation wavelength of 890 μW. The near-field image at this time is shown in FIG. 4, and the far-field image is shown in FIG.

The semiconductor laser array device 19 according to the present invention can also be implemented with respect to a laser element constructed using a material other than the materials described in the above embodiments, that is, A-GaAs/GaAs-based materials. Further, the present invention may also be applied to a laser element having an active waveguide structure other than that of the above embodiment, or a laser element in which all the conduction types are opposite to those of the above embodiment.

Effects As described above, according to the present invention, there are a plurality of first active waveguides (main elements) that are optically coupled to each other, and a second waveguide (sub-element) that intersects with these first waveguides. ), and the first and second waveguides have a periodic structure with a period of about the wavelength or less, so that in the optically coupled element, only the 0° phase can be selectively transmitted to the high output region. It becomes possible to oscillate.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the structure of a semiconductor laser array device 19 according to the present invention, FIGS. 3 and 4 are diagrams showing a near-field image and a far-field image of the semiconductor laser array device 19, and FIG. 6 is a diagram showing the structure of a conventional semiconductor laser array, FIGS. 7 and 8 are diagrams showing the near-field pattern and far-field pattern of the semiconductor laser array, and FIG. 9 is a diagram showing the supermode threshold of the semiconductor laser 7 lake. FIG. 10, which is a diagram showing the results of theoretical analysis of the value DIN, is a structural diagram of another conventional semiconductor laser array 10. 19... 21... Group [, 22, 26... Cladding layer, 23... Grating, 24... Optical waveguide layer,
25... Active layer, 27... Contact layer, 28.2
9...Active waveguide agent Patent attorney Shikyo Upper part 31 Figure 1 Figure 2 Figure 3 Light angle Associate Figure 4 → Figure 5 g6 Figure 7 Light. Figure 8 0.5 1 5 10 Figure 9

Claims (1)

[Claims] A plurality of first active waveguides optically coupled to each other, and a single or plural second active waveguides intersecting the first active waveguides.
an active or inactive waveguide, and the first and second waveguides are optically coupled by a periodic structure having a period approximately equal to or less than a wavelength. .