Coherent light generators – Particular active media – Semiconductor
Reexamination Certificate
2001-04-02
2003-04-29
Paladini, Albert W. (Department: 2827)
Coherent light generators
Particular active media
Semiconductor
C372S018000, C372S029010, C372S050121, C257S081000
Reexamination Certificate
active
06556606
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a high-powered semiconductor laser array apparatus used for optical recording, optical communications, making a hole, welding and the like. The present invention also relates to a manufacturing method for such a semiconductor laser array apparatus, and to a multi-wavelength laser emitting apparatus using such semiconductor laser array apparatuses.
(2) Description of the Related Art
Recently, high-power semiconductor lasers are required for optical recording, optical communications, making an hole, and welding.
In order to meet such a requirement, there is a well-known semiconductor laser apparatus in which a plurality of laser oscillation units are formed in an array structure on the same substrate.
In this apparatus, a high-power light output is obtained by condensing a plurality of laser beams emitted from a plurality of laser oscillation units provided on the same substrate into a spot. Note that in this specification, a laser oscillation unit refers to a portion emitting laser beams and a portion guiding the laser beams.
However, laser beams emitted from those laser oscillation units are different from each other in the wavelength and phase. Therefore, when these laser beams are condensed into a spot, they interfere with each other. As a result, a high-power laser output according to the number of laser oscillation units cannot be obtained.
To cope with the problem, Japanese Laid-Open Patent Application No. H5-226765 discloses a semiconductor laser apparatus. In this apparatus, a plurality of laser oscillation units are placed close to each other on the same substrate so that laser beams from the laser oscillation units interfere with each other at the region of a current blocking layer where laser beams are leaked, whereby the wavelengths and phases of the laser beams can be matched with each other. The laser beams emitted from laser oscillation units are focused into one spot, whereby a high-power semiconductor laser apparatus can be realized.
Meanwhile, when a plurality of array structures are combined, much higher light output power can be expected as compared with only one array structure. However, in the above-stated apparatus, laser beams emitted from the laser oscillation units in the same array structure can be matched with each other in wavelength and phase, but laser oscillation units across different array structures cannot be matched.
Next, some laser emitting apparatuses are applicable for industrial uses such as welding and punching. In these apparatuses, a higher optical power is required. Therefore, gas lasers (such as CO
2
lasers and excimer lasers), and solid-state lasers (such as YAG lasers) are currently dominant in this field.
However, a laser emitting apparatus using a gas laser or a solid-state laser inevitably increases in size owing to the structural limitations. Particularly, a laser emitting apparatus using a gas laser needs a gas container within them. Hence, even if a target to be machined is small, an apparatus has to be in a large-scale structure. As a result, a large space is necessary for installing the apparatus, and an expensive apparatus cost is inevitable. In addition, since luminous efficiencies of the gas lasers and solid-state lasers are bad, the apparatus consumes a large amount of electric power. Moreover, in case of gas lasers, their maintenance cost is increased for refilling the gas.
Meanwhile, various workpieces have been developed in accordance with developments of materials. Especially, in case that a workpiece fabricated by mixing two kinds of materials whose laser absorption coefficients are different from each other is processed by the above-stated laser emitting apparatuses, the following problems occur.
The wavelength of laser beam emitted from the above-stated apparatus is fixed at a specific single wavelength, so the wavelength is difficult to be changed. For instance, assuming the workpiece is made of materials A and B, and the material A has a high absorption coefficient for a laser beam with a wavelength &agr;, while the material B has a low absorption coefficient for the laser beam, then the laser power has to be increased in order to melt the material B as well. As a result, the temperature of the material A excessively increases, which causes inappropriate parts to be melted. Consequently, in case of making a hole in the above workpiece with these laser apparatuses, a diameter of the hole is larger than the intended dimension and the machining precision deteriorates greatly.
In the above case, it is preferable to also use a laser beam with a wavelength &bgr;. However, it is difficult to change the wavelength of the laser beam in the gas or solid-state multi-wavelength laser emitting apparatus as stated above.
Also in various other fields, there is a demand for a small-sized and high-power laser application equipment with multi-wavelength.
SUMMARY OF THE INVENTION
The first object of the present invention is to provide a semiconductor laser array apparatus in which the above-stated plurality of array structures are combined so that laser beams emitted from the plurality of array structures are matched in wavelength and phase (hereafter called “phase locking”), and a manufacturing method for the same.
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 beams having different wavelengths.
The first object is achieved by a semiconductor laser array apparatus made up of: a first laser array structure which includes, a plurality of first laser oscillation units which are arranged side by side at an interval, and a first current blocking material which fills a space between each pair of adjacent first laser oscillation units; and, a second laser array structure which includes, a plurality of second laser oscillation units which are arranged side by side at an interval, and a second current blocking material which fills a space between each pair of adjacent second laser oscillation units, wherein, when the semiconductor laser array apparatus is activated, laser beams generated by the first laser array structure and the second laser array structure leak to the outside of the first and second laser array structures so as to form first and second distribution regions of the laser beams, and the first and second laser array structures are closely disposed so that the first and second distribution regions contact or overlap with each other.
This construction enables phase locking between the first and second laser array structures. Consequently, in case of condensing laser beams emitted from the laser array structures into one spot, a high light output power can be obtained.
The above construction may include a construction in which a semiconductor layer is formed between the first and second laser array structures, a thickness of the semiconductor layer is adjusted so that the first and second distribution regions contact or overlap with each other.
The above constructions may also include a construction in which an optical waveguide layer which is interposed between the first and second laser array structures, and introduces laser beams oscillated by each of the first and second laser oscillation units, wherein the first and second distribution regions contact or overlap with each other within the optical waveguide layer. The optical waveguide layer is made of a material whose refractive index is larger than that of the clad layer or the like but smaller than that of the active layer. Here, the refractive indexes can be easily controlled by appropriately adjusting a composition of semiconductor materials (the amount of Al or the like).
Here, in the above constructions, at least adjacent two laser oscillation units among the first laser oscillation units are optically coupled with each other, and at least adjacent two laser oscillation units among the second laser oscillation units are optical
Ito Kunio
Kazumura Masaru
Takayama Toru
Tamai Seiichiro
Yuri Masaaki
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