JPS6390877A - Composite optical semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To obtain a high-output and multi-functional device by monolithically integrating a plurality of semiconductor lasers and a plurality of optical detectors, placing the semiconductor lasers so that the optical axes join at one point in front of them, and placing the optical detectors along the optical axes of the lasers and backward of the lasers, thereby providing a plurality of semiconductor lasers. CONSTITUTION:In a composite semiconductor light emitting device constructed by monolithically integrating a plurality of semiconductor lasers 1-5 and a plurality of optical detectors 11-15, the semiconductor lasers 1-5 are placed so that the optical axes join at one point in front of them, and the optical detectors 11-15 are placed along the optical axes of the semiconductor lasers 1-5 and backward of those semiconductor lasers 1-5. For instance, on a GaAs substrate 101, five lasers 1-5 and the same number of optical detectors 11-15 are monolithically integrated, the end face of which is consisting of an etched mirror. And, the lasers 1-5 are placed so that they are close to each other with a 10mum spacing at the emitting surface side (the center distance of light emitting regions is 10mum) and they are apart with a 50mum spacing at the optical detectors 11-15 side, whereby the optical axes of the respective lasers 1-5 join at one point in front of them.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor laser suitable for optical information processing, particularly as a light source for a read/write optical disk file system.

(Prior Art) Consumer semiconductor lasers are desired to have higher output and multifunctionality. One example of achieving high output power is phase-locked lasers, which are used in fields where watt-level optical output is required. On the other hand, as an example of multifunctionality, there is an independently driven laser in which a plurality of lasers and photodetectors are monolithically integrated in close proximity. A typical example is the 46th Academic Conference of the Japan Society of Applied Physics (paper number 3p-N-14).
A 1 z G a by rRIBE by Uchimaki et al.
The report is titled ``Fabrication of I-X As2-Beam LD PD array''. Since the present invention is an evolution of this LD-PD play, it will be briefly explained. FIG. 3 is a structural diagram of a two-beam LD-PD play. The manufacturing process first uses the liquid phase epitaxial method on an n-type GaA3 substrate 300, and then
Gao, st As cladding layer (thickness 1.0 μm)
301, n-type A 1 o, s G a o, y A
s light guide layer (thickness 0.3 μm) 302, Andor A 10. ! 5Ga6. @@ As active layer (thickness 0.
08μm) 303, p-type Alo, s Gao, s As
Intermediate layer (thickness 0.3 μm) 304, p-type Alo, s
i Gao, st As cladding layer (thickness 2.0 μm)
305, p-type GaAs contact layer (thickness 0.8μ
m) form 306; Next, two 8-μm-wide stripe-shaped etching masks spaced apart by 50 μm in the (011) direction are formed using normal photolithography technology, and then etched with a height of approximately 5 μm using a phosphoric acid-based etching solution.
A mesa of m is formed, and only the intermediate layer is selectively etched by about 0.2 μm using a hydrofluoric acid-based etching solution to create a constriction in the mesa. Next, by second liquid phase growth, p-type Al
A GaAs block layer 307 and an n-type AlGaAg buried layer 308 are formed. After Zn is diffused only in the mesa area using the film as a mask (diffusion front 309 is indicated by a dotted line), a positive electrode 310 and 311 for the laser and a positive electrode for the photodetector, which are divided into four parts, are placed on the surface as electrodes. Electrode 31
2.313 is formed. Next, resist/Ti (titanium)
The resonator surface of the laser and the end face of the photodetector are formed by using reactive ion beam etching using a three-layer resist consisting of /resist as an etching mask. After this, a negative electrode is formed on the back surface of the crystal to create a two-beam LD-PD.
The array is complete. The feature of this two-beam LD-PD play is that one of the two closely spaced lasers is used for writing and the other is used for reading, and the optical output of each can be monitored by a photodetector placed monolithically at the rear. be. As a result, the conventional optical system can be made much simpler.

(Problems to be Solved by the Invention) However, in the future, it is expected that independently driven semiconductor lasers with not only two beams but also multiple beams will be required as light sources for optical information processing systems. In this case, if the optical system for focusing the laser beam can be simplified by reducing the beam interval, it will be advantageous in terms of high-speed access, reliability, and cost.

From this point of view, the conventional example is not necessarily suitable as a multi-beam light source. The first reason for this is that it has a buried structure formed by liquid phase growth.

Liquid phase growth has a strong plane orientation dependence (in a conventional structure, it is difficult to select a direction other than the (011) direction). Furthermore, in order to manufacture a plurality of lasers with good reproducibility with this structure, it is difficult to reduce the beam spacing to 50 μm or less. For this reason, for example, when five beams are integrated, the optical system must condense beams of 200 μm or more, and a collimating lens with a large NA (numerical aperture) is required.

This is undesirable because it places a burden on the servo system of the lens and increases the astigmatism difference of the beam. @
Second, even if the laser spacing could be reduced by some method, the arrangement would be limited by the crystal growth method, and there would be no degree of freedom other than mutually parallel layouts. Furthermore, in consideration of heat dissipation in mounting, the beam spacing cannot be made extremely small.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a high-output, multifunctional composite semiconductor light-emitting device that includes a plurality of semiconductor lasers.

(Means for Solving the Problems) The present invention is characterized in that a plurality of semiconductor lasers and a plurality of photodetectors are monolithically integrated, and the semiconductor lasers are arranged so that their optical axes intersect at one point in front. The array type semiconductor laser device is characterized in that the photodetector is arranged behind the semiconductor lasers along the optical axis of the laser.

(Function) Forming laser waveguides and resonators in arbitrary crystal orientations is extremely effective in creating optimal groove structures for optical integrated circuits, especially array-type lasers.

For example, if it is possible to make the optical axes of multiple monolithically integrated lasers intersect at a single point, this point can be set near the focal position of the collimating lens to create a multifunctional light beam without complicating the optical system. Heads can be made. Furthermore, if a photodetector for monitoring laser light is integrated, the optical system will become even simpler. On the other hand, properly controlled dry etching can form an etched surface with excellent crystal anisotropy and specularity. Among them, reactive ion beam etching (hereinafter abbreviated as RIBE) is used for etching AlzGa, -
Etching progresses at a constant speed with respect to zAsK, making it possible to form a perpendicular and smooth surface.

Therefore, using the etched surface by RIBE as the resonator end face of a laser can be an effective means for increasing the integration and mass productivity of semiconductor lasers. Furthermore, unlike chemical etching, RIBE allows the resonator direction to be selected in any desired crystal orientation, thereby increasing the degree of freedom in arrangement in the case of an array type laser.

However, the laser waveguide cannot necessarily be selected to have an arbitrary crystal orientation. This is primarily constrained by crystal growth techniques. For example, in the case of a conventional buried laser, a buried waveguide can be formed with good reproducibility only in the (011:> direction on a (100) GaAs substrate using liquid phase growth. Therefore, even if an etched mirror is used for integration, the direction of the resonator is determined conventionally.

Further, in growth methods such as metal organic pyrolysis growth method (hereinafter referred to as MOCVD method) or molecular beam epitaxy method (hereinafter referred to as MBE method) in which the growth conditions deviate from a perfect thermal equilibrium state, the dependence on crystal orientation is small.

Therefore, a buried refractive index optical waveguide can be formed in any crystal orientation.

Examples of the present invention will be described below.

(Embodiment) FIG. 1 is a perspective view showing a schematic structure of an embodiment of the present invention. Five lasers 1 to 5 and the same number of photodetectors 11 to 15 are monolithically integrated on a GaAs substrate 101, the end faces of which are constructed of etched mirrors. Lasers 1 to 5 and photodetectors 11 to 15 are shown as representatives of their respective optical waveguides. The lasers are arranged so that they are close to each other at 10 μm intervals on the emission surface side (the center spacing of the light emitting regions 111 is 10 μm), and are spaced apart by 50 μm on the photodetector side, with the optical axis of each laser facing forward. They are arranged so that they intersect at one point. FIG. 2 is an enlarged view of the exit surface side of the embodiment shown in FIG. The laser structure is a transverse mode control type called a self-line structure. The manufacturing method includes, for example, forming an n-type A 1 o, 45 Gao, 1sA3 cladding layer (thickness 2 μm) 201, n-type Alo, ss Gaa, ss A on an nfiGaAs substrate 200.
s active layer (thickness 0.1 μm) 202, p-type Alo, 4s
Goo, is As cladding layer (thickness 0.5μm)
203, n-type GaAs light absorption layer (thickness 10 μm) 2
04 are sequentially stacked using the MOCVD method. Next, a stripe mask with a width of 3 μm is formed along the cavity direction VC using photolithography, and etching is performed using dry etching or the like until the n-type cladding layer 203 is reached. Subsequently, a p-type AlGmAg cladding layer (thickness 2 μm) 205 and a p-type G
An aAs contact layer (2 μm thick) 206 is epitaxially grown. The subsequent steps of forming electrodes and forming end faces by RIBE are the same as in the conventional example. Finally, each laser and photodetector is coated with the necessary coatings to complete the embodiment of the present invention.

In the case of this embodiment, a transverse mode control type laser was used for the self-line, but the composite optical semiconductor light emitting device of the present invention can also be constructed with other structures and an arbitrary number of elements.

(Effects of the Invention) An advantage of the present invention is that a plurality of lasers and a plurality of photodetectors can be used in a simple optical system. For example, in the above embodiment, an example was shown in which five lasers and the same number of photodetectors were integrated, but if the reading and writing of a disk, which was conventionally done with two lasers, is done with five lasers, the access time will be longer than K. It can be significantly shortened. Furthermore, it has the effect of increasing heat dissipation due to the laser drive current compared to arranging the array type lasers in a fan shape.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a schematic structure of an embodiment of the present invention, FIG. 2 is an enlarged view of its output end face, and FIG. 3 is a perspective view showing a schematic structure of a conventional example. 1-5... Laser, 11-15... Photodetector, 10
1... n-type GaAs substrate, 111... light emitting region, 2
00...nm GaAs substrate, 201...n-type Al
o4sGaossAs cladding layer, 202...Undoped A 1G 1 lG! LoasAs active layer, 203
．． 205=-p-type A 1 o 4s Gaoss A8 cladding layer, 204-n-type GaAs light absorption layer, 206...
p-type GaAs contact layer, 207...positive electrode, 300...n-type GaAs substrate, 301"・n-A
le1@GJLO,I! As cladding layer, 302”
n-type Alo, go Gae, yo As light guide layer,
303...Undoped AlO, 1s Gas, as
As active layer, 304 = p-type Alo, go Gao, s
o As middle layer, 305''' p-type Alo, sa Gao
, ay As cladding layer, 306-...p-type GaAs
Contact layer, 307...p-type Alo, 1sGao,
,,t As block layer, 308...n type A 16,
36Gao, a*As buried layer, 309...diffusion front, 310.311...positive electrode for laser, 312
．． 313...Positive electrode for laser photodetector, 314...
・Negative electrode. Agent Patent Attorney Shinsuke Honjo Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] In a composite optical semiconductor light emitting device formed by monolithically integrating a plurality of semiconductor lasers and a plurality of photodetectors, the semiconductor lasers are arranged so that their optical axes intersect at one point in front, and the photodetector is arranged such that their optical axes intersect at one point. A composite optical semiconductor light emitting device characterized in that the semiconductor laser is disposed behind the semiconductor lasers along the optical axis thereof.