Coherent light generators – Particular resonant cavity – Specified output coupling device
Reexamination Certificate
2001-03-27
2004-11-30
Leung, Quyen (Department: 2828)
Coherent light generators
Particular resonant cavity
Specified output coupling device
C359S204200
Reexamination Certificate
active
06826224
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-power semiconductor laser array apparatus that is applicable to various fields, such as optical recording, optical communications, punching, and welding. The present invention also relates to a multi-wavelength laser emitting apparatus using a plurality of such semiconductor laser array apparatuses.
2. Description of the Related Art
In recent years, attempts have been made to apply semiconductor laser array apparatuses to various fields, such as optical recording, optical communications, punching, and welding. This creates demand for high-power semiconductor layer array apparatuses because currently available semiconductor laser array apparatuses are basically low-powered and are not applicable to these fields.
A high-power semiconductor laser array apparatus is disclosed by Japanese Laid-Open Patent Application No. H5-226765. The semiconductor laser array apparatus has an array structure where a plurality of semiconductor laser elements are formed on the same substrate. Note that in this specification, a semiconductor laser element refers to a laser oscillation unit including a current blocking layer.
In the semiconductor laser array apparatus, the semiconductor laser elements are arranged close to each other in the width direction thereof. This arrangement causes interference between laser lights emitted from the semiconductor laser elements, so that the laser lights are matched in wavelength and phase (so-called “phase locking” is achieved). As a result, the laser lights emitted from the plurality of semiconductor laser elements are condensed to form a spot and the output power of the semiconductor laser array apparatus is increased.
To increase the flexibility in designing a semiconductor laser apparatus, it is required to develop a new structure where the phase locking is achieved without arranging the semiconductor laser elements close to each other in the width direction.
Gas lasers (such as CO
2
lasers and excimer lasers) and solid lasers (such as YAG lasers) are mainly used for industrial laser emitting apparatuses that are applied, for instance, to welding and punching because these lasers have high output powers.
A laser emitting apparatus using a gas laser or a solid laser, however, inevitably increases in size due to its structure. In particular, a laser emitting apparatus using a gas laser needs to be equipped with a gas cylinder, so that the hardware scale of the laser emitting apparatus becomes large even if it is designed to process small materials. This increases the price of the laser emitting apparatus and creates a necessity for a large installation space. Also, the laser emitting apparatus consumes a large amount of electricity due to its low luminous efficiency. Further, because the gas cylinder of the laser emitting apparatus needs to be refilled, the maintenance cost is increased.
Also, the recent development in the material industry has realized various new types of works (materials to be processed using lasers). This causes a problem that the laser emitting apparatus using a gas laser or a solid laser cannot process a work produced by mixing two types of materials having different absorption coefficients for a laser of a wavelength.
The laser light emitted from a gas laser or a solid laser has a specific wavelength and it is difficult to change the wavelength. Suppose that a work has been produced from materials A and B, the material A has a high absorption coefficient for a laser light of a wavelength &agr;, and the material B has a low absorption coefficient for the laser light. In this case, it is necessary to increase a laser power to melt the material B as well. This excessively raises the temperature of the material A and thus melts unnecessary parts of the material A. Therefore, if a hole is formed in the work, the diameter of the hole becomes larger than an intended size. This results in a problem that the processing accuracy is significantly impaired.
To cope with this problem, it is preferred to also use a laser light of a wavelength &bgr;, for which the material B has a high absorption coefficient. However, this is not a feasible solution because, as described above, it is difficult to change the wavelength of the laser light emitted from a multi-wavelength laser emitting apparatus using a gas laser or a solid laser.
Also in various other fields, there is demand for a multi-wavelength laser emitting apparatus of a reduced size but a high output power.
SUMMARY OF THE INVENTION
The first object of the present invention is therefore to provide a semiconductor laser array apparatus where laser lights emitted from a plurality of elements provided on the same substrate are matched in wavelength and phase (that is, the laser lights are phase locked).
The second object of the present invention is to provide a multi-wavelength laser emitting apparatus that realizes a small-sized but relatively high-power laser appliance which emits various laser lights having different wavelengths.
The first object is achieved by a semiconductor laser array apparatus including: a substrate; a plurality of current blocking elements that are stripe shaped and are formed on the substrate; and a plurality of light waveguides that are formed between the plurality of current blocking elements, where at least two adjacent light waveguides are optically connected by removing a part of each current blocking element therebetween.
This construction allows the semiconductor laser array apparatus to match emitted laser lights in wavelength and phase (that is, the laser lights are phase locked) without arranging semiconductor laser elements close to each other in the width direction thereof on the same substrate.
With the conventional technique described above, laser elements need to be arranged close to each other in an arrangement direction of light waveguides to cause interference between laser lights emitted from the laser elements. This limits the width of a current blocking layer and decreases design flexibility. Also, because the laser elements are arranged close to each other, heat is confined in a narrow space and the amount of generated heat is increased. Temperature is increased particularly in a center area and the reliability of an apparatus is reduced.
On the other hand, with the technique of the present invention, semiconductor laser elements are not arranged close to each other in the width direction thereof on the same substrate. This increases design flexibility and reduces the amount of heat generated at each laser element. As a result, the reliability of the apparatus is increased.
Also, because semiconductor laser elements are not arranged close to each other on the same substrate with the technique of the present invention, phase locking is achieved with reliability, in comparison with the conventional technique. That is, with the conventional technique where phase locking is achieved by arranging semiconductor laser elements close to each other, the phase locking cannot be achieved with reliability. However, with the technique of the present invention where light waveguides are optically connected to each other by discontinuous areas of the current blocking layer, light distribution areas are formed also in the discontiguous areas. These light distribution areas cause the interference between lights traveling through adjacent light waveguides, and thus amplify the lights. This makes it possible that phase locking is achieved with stability and reliability.
Here, the discontiguous areas of the current blocking layer may be long grooves and arranged close to the light waveguides. In this case, phase locking can be achieved without problems. This is because even if the discontiguous areas are not connected to the light waveguides, waveguide areas through which lights seep overlap the light distribution areas. Therefore, interference is caused between lights traveling through adjacent light waveguides (that is “a light interference function” is achieved) and phase l
Ito Kunio
Kazumura Masaru
Tamai Seiichiro
Yuri Masaaki
Leung Quyen
Matsushita Electric - Industrial Co., Ltd.
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