JPH0232581A - Integrated semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a far field pattern which is superior in unimodal properties by mounting optical system instruments so that a part of outgoing beams returns selectively every other light emitting point to positions of light emitting points at the end plane of a laser chip. CONSTITUTION:Outgoing beams emitted from an integrated laser chip 20 are condensed as real images of light emitting points 21 on slit positions 23 by a convex lens 22. Light points of light emitting points 21 hold positions in such a way that they are out of phase by 180 deg. every other point. All the outgoing beams passing through the slit positions 23 have the same phases. After that, the real images are focused on the slit positions 23 by a convex lens 24, a reflection mirror 25 and a lens 24. In such a case, the outgoing beams which are returned by the reflection mirror 25 may return by the lens 22 every other light emitting point to the positions of the light emitting points at the end plane of the laser chip 20. Oscillation gains thus increase every other laser stripe and all the outgoing beams emitted from the stripes where the oscillation gains increase are of the same phase. An effect which is equivalent one where the same phase oscillation is obtained surely is secured in this way and a far field pattern which is superior in unimodal properties is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an integrated semiconductor laser device (hereinafter simply referred to as an integrated laser device), and particularly to an integrated laser device that can obtain a unimodal far-field pattern. It is related to.

[Prior Art] Conventionally, a device related to this type of integrated laser has a 0PTO
ELECTRONIC3-Devices and T
technologies Vol, 2. NO, 1 L99
~114. June, 1987 (Reference 1) and Communication Society Technical Research Report 0QE-86-64pp, 25-30
(Reference 2).

The integrated laser was developed in response to the need to manufacture a high-output semiconductor laser that exceeds the upper limit of the maximum optical output of a semiconductor laser composed of a single waveguide.

However, since multiple waveguides are integrated, it is much more difficult to obtain a unimodal far-field pattern, which is required in many application fields, than with a semiconductor laser consisting of a single waveguide.

To solve this problem, it is necessary to cause each waveguide to oscillate in a fundamental mode and in a super fundamental mode that is in phase with each other.

As one method for this, structures have been devised that allow a large gain difference between the super fundamental mode and the super higher order mode.

As this type of structure, there is one disclosed in the above-mentioned document.

FIG. 3 is an explanatory diagram showing an example of a cross section of a conventional integrated laser device.

In FIG. 3, 31 is a p-type GaAs substrate, 32 is an n-type GaAs current blocking layer, 33 is an n-type AlGaAs cladding layer, 34 is a p-type AlGaAs active layer, and 35 is an n-type AlG
aAs cladding layer, 36 is an n-type GaAs cap layer, 3
7° 39 are n+p side electrodes, and 38 is a V groove.

The structure of these conventional integrated lasers has three integrated lasers.
It has a structure in which five internal current confinement type refractive index guide type lasers are lined up.

In this way, the integrated laser is generally one in which a plurality of lasers are uniformly arranged in parallel, even if the number of integrated lasers is not the above-mentioned inverted arrangement, and even if the structure of each stripe is slightly different.

When a current is applied in the forward direction to the integrated laser device having the structure shown in FIG. 3, the current flows through the portion of the groove 38 where there is no current blocking layer, and the active layer in this vicinity emits light, eventually resulting in laser oscillation.

In this way, the light forms a homogeneous and parallel leading wave path in the p-type AlGaAs active layer 34 on the groove 38.

In an integrated laser formed in this way, if the stripe spacing etc. are set appropriately, the light propagating through each stripe can be
They are guided while interacting with each other, and become a phase-locked laser that oscillates at the same wavelength and at a constant wavelength while maintaining a constant phase relationship.

However, in this phase-locked laser, as explained in Figure 3, five stripes are equivalently configured, so which of the eigenmodes (hereinafter referred to as supermodes) of the five integrated lasers as a whole Also, transverse fundamental mode oscillation (all outgoing lights have the same phase), which is a necessary condition for obtaining a unimodal far-field image, is not necessarily achieved.

This will be explained with reference to FIG.

FIG. 4 is a graph showing the relationship between the supermode order ν and the relative mode gain.

That is, the oscillation mode gain for the transverse mode in which the integrated laser can oscillate when the number of stripes is 10 (the fundamental mode is C1°, the highest mode is C10, and the letters ν are used to indicate the order). The relative value of (assumed to be 1) is shown.

However, FIG. 4 shows the case where the stripe width W = 2 q and the stripe interval is d-2-.

, 1m M4 diagram, compared to the gain of Sea 1, Sea 2~9
can only obtain a gain of about 70%, whereas the highest order mode of the sea 10 (a mode in which the phases of light emitted from adjacent stripes are shifted by 180') has a gain of about 10%.
% is high.

That is, it shows that the highest order mode is most likely to oscillate.

As a result, the light emitted from this integrated laser has a multimodal far-field pattern.

Therefore, in order to obtain a unimodal far-field image, it is necessary to block the mode of the sea 10.

Such a method is disclosed in the above-mentioned document 2,
The goal is to narrow W and d shown in FIG.

By doing this, the highest order mode can be blocked. However, narrowing W and d requires advanced microfabrication, which is difficult in reality.

Therefore, Reference 1, p. 111-114. There is a method as shown in the figure.

That is, FIGS. 5(a) and 5(b) are explanatory diagrams of a method using a conventional integrated laser.

This means that the integrated laser is designed to oscillate in the highest order mode (design dimensions are much looser than the requirement for highest mode cutoff), and that every other stripe is 1/4 wavelength thick. This is a method of providing a phase shifter having the following characteristics.

By doing this, all the emitted light will basically be emitted in the same phase, and the appearance will be the same as that of the fundamental mode oscillation of the upper sea 1, and a unimodal far-field pattern will be obtained. It will be done.

FIG. 5(a) is a diagram explaining this.

First, the output end face is coated with anti-reflection coating. By doing this, when looking at the phase of the emitted light on the plane of AA, there is a phase difference of 180@ between adjacent stripes.

On top of this coating film, every other stripe is
A phase shifter corresponding to four wavelengths is formed.

That is, the refractive index of the material of the phase shifter is n, and the wavelength of the emitted light is λ.
Then, a phase shifter with a thickness of -λ/4n is fabricated for every other stripe.

When this is done, the phases at BB are all the same.

In other words, it can be made substantially the same as the fundamental mode oscillation of Sea 1.

FIG. 5 shows an example in which the above-described phase shifter is actually provided on the end face of an integrated laser.

An A D 20a film is formed on every other stripe to have a thickness of λ/2, that is, non-reflective, and on the stripes in between, it is formed to have a thickness of (λ/2)+t.

By doing this, as explained above, the integrated laser which was oscillating in the highest order mode before the coating process becomes equivalent to oscillating in the fundamental mode of the sea 1.

This method is an excellent method when a unimodal far-field pattern is desired because it is easiest to create an integrated laser with the highest oscillation mode.

[Problems to be Solved by the Invention] However, the above-described conventional method of providing a phase shifter has many difficulties in producing an actual device.

First, when providing a phase shifter, the light emitting position of each stripe cannot be determined very accurately, so the position of the phase shifter cannot be determined accurately.

Further, it is also difficult to accurately set the thickness t of the phase shifter to λ/4n because the oscillation wavelength cannot be determined with sufficient accuracy at the time of forming the phase shifter.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an integrated laser device that can obtain an excellent unimodal far-field pattern.

[Means for Solving the Problems] The present invention provides an integrated laser chip that performs phase synchronized oscillation in an integrated semiconductor laser device, and a selective laser beam that selectively moves every other light emitting point to the light emitting point position on the emission end face of the laser chip. This is an integrated semiconductor laser device in which optical equipment such as a convex lens, multiple slits, and a reflector are provided in front of the emitted light so that a part of the emitted light returns.

[Function] The light emitted from the integrated laser device according to the present invention is emitted by a convex lens provided in front of the emitting end surface.

Of the light emitted from the integrated laser chip, only the emitted light components from every other laser stripe are extracted and emitted by an optical system device such as a multi-slit reflector.

Therefore, as will be described later, the light emitted from the integrated laser device according to the present invention is made to be equivalent to the light emitted from the integrated laser device that is all emitted in the same phase, and has a single peak. It is possible to obtain a far-field image of

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2.
Explain in detail.

FIG. 1 is an explanatory diagram of the structure and operation of an integrated laser device according to the present invention, and FIG. 2 is an explanatory cross-sectional diagram of an integrated laser element used in an embodiment of the present invention.

In FIG. 1, 20 is an integrated laser element.

21 is a light emitting point, 22 and 24 are convex lenses, 23 is a double slit, and 25 is a reflecting mirror or a semi-transparent mirror.

Further, in FIG. 2, 1 is a p-type GaAs substrate, 2 is an n-type GaAs current blocking layer, and 3 is a p-type AlGaAs cladding layer.

4 is a p-type AlGaAs active layer, 5 is an n-type AlGaAs cladding layer, 6 is an n-type GaAs cap layer, and 7.8 is an n-side electrode and a p-side electrode, respectively.

In the structure of the device shown in Fig. 2, ■p-type AlG outside the groove
If the thickness D of the aAs cladding layer 3 is set to about 0.3 -, oscillation will occur in the p-type AlGaAs active layer 4 above each V-groove, and if the stripe spacing d is appropriately designed, each of these stripes will The light from oscillates in a phase-locked manner.

In this case, the supermode of oscillation is likely to be the highest order (in this case, C3).

Depending on the dimensions of W and d, fundamental mode oscillation of sea 1 is possible, but as already explained in the prior art section, it is generally difficult to form in this way.

Next, the structure and operation of the integrated laser device of the present invention will be described based on FIG. 1.As shown in FIG. The light is focused as a real image of the point 21.

Further, the light points of the light emitting point 21 are five light points as shown in the figure, and every other light point is shifted by 180 degrees.

This multiple slit 23 is made so as to block every other light spot in a row of light spots (5 spots) of the real image of the light emitting spot 21 .

Even if the emitted light from the integrated laser chip 20 oscillates in the highest order mode, all of the light passing through this multiple slit 23 has the same phase.

After this, the reflecting mirror (or semi-transparent mirror) 2 is
5, the light returns to the convex lens 24 and forms a real image (light spot) on the multiple slit 23.

The convex lens 24 is arranged so that all of this real image (light spot) can pass through the multiple slit 23.

In this way, the light returned from the reflecting mirror 25 is returned to the light emitting point position of the end face of the integrated laser chip 20 at every other light emitting point by the convex lens 22.

Generally, the oscillation threshold gain of a semiconductor laser is reduced by the return light. That is, the oscillation gain increases accordingly, making it easier to oscillate.

Therefore, in the case of this embodiment, the oscillation gain is increased for every other laser stripe, and all the lights emitted from the stripes with increased oscillation gain are in the same phase.

By doing this, the oscillation from the stripe with no return light is suppressed, and the oscillation from the stripe with return light is enhanced, and the light emitted from the integrated laser device according to the present invention is This is essentially equivalent to an integrated laser that is phase-locked in the same phase.

On the other hand, as shown in FIG. 1, the emitted light can be taken out in both the A direction and the B direction, and it goes without saying that when taking out the light from the B direction, the reflecting mirror 25 should be a semi-transparent mirror. .

As is clear from the above embodiments, the present invention includes a convex lens in front of the emitted light so that a part of the emitted light selectively returns to the light emitting point position of the emitting end face of the laser chip at every other light emitting point. This requirement requires that optical equipment such as multiple slits and a reflecting mirror be provided.

It goes without saying that the integrated laser chip shown in the above embodiments is not limited to this embodiment, and may have other shapes as long as it is a phase integrated laser chip.

[Effects of the Invention] As described in detail above, according to the integrated semiconductor laser device of the present invention, in a phase-locked integrated laser, -
In-phase oscillation (basic transverse mode oscillation sea 1), which is difficult for boat fishing
It is possible to obtain the same effect as that obtained with certainty.

This makes it possible to obtain a unimodal far-field image, which is very convenient in applied fields such as information processing.

Further, according to the present invention, there is an advantage that advanced techniques such as providing a phase shifter on the output end face are not required.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the structure and operation of an integrated laser device of the present invention, FIG. 2 is a cross-sectional explanatory diagram of an integrated laser device used in an embodiment of the present invention, and FIG. 3 is a conventional integrated laser device. An explanatory diagram showing an example of a cross section. FIG. 4 is a graph of the relationship between supermode order ν and relative mode gain, and FIGS. 5(a) and 5(b) are explanatory diagrams of a conventional method using an integrated laser. In the figure, 1: p-type GaAs substrate, 2: n-type GaAs
Current blocking layer, 3: p-type AlGaAs cladding layer, 4: p
type AlGaAs active layer, 5: n-type AlGaAs cladding layer, 6: n-type GaAs cap layer, 7 and 8: each n+
p-side electrode. 20: Integrated laser chip, 21: Light emitting point, 22°24
= convex lens, 23: multiple slits, 25: reflecting mirror or semi-transparent mirror. 〔Vermilion lacquer n-shaped - A glimpse of the irritable mystic spider'' 17-hour offensive moon concavity Fig. 3 Super mode 2-z toughness Fig.

Claims (1)

[Claims] (1) In an integrated semiconductor laser device, a part of the emitted light is selectively returned to the light emitting point position of the emitting end face of the integrated semiconductor laser chip that performs phase synchronized oscillation and the emission end face of the laser chip at every other light emitting point. An integrated semiconductor laser device is characterized in that an optical system device is provided in front of emission.