Optical waveguides – With optical coupler – Particular coupling function
Reexamination Certificate
2001-11-06
2004-04-06
Hooly, Brian (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling function
C385S033000, C385S049000, C398S043000, C398S048000, C372S006000
Reexamination Certificate
active
06718088
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multiplex laser light source, and more particularly to a multiplex laser light source that multiplexes laser beams emitted from a plurality of semiconductor lasers by making use of optical fibers. The invention also relates to an exposure apparatus which employs the multiplex laser light source as the exposure light source.
2. Description of the Related Art
As conventional devices that can emit a laser beam in an ultraviolet region, a wavelength conversion laser (which converts infrared light, emitted from a solid-state excitation laser, to a third harmonic in an ultraviolet region), an excimer laser, and an argon-ion (Ar) laser have been put to practical use.
Furthermore, a GaN semiconductor laser has recently been provided as a device that can emit a laser beam having a wavelength near 400 nm (see Jpn. Appl. Phys. Lett., vol. 37, 1998, p. L1020).
It is also conceivable that the light source to emit a laser beam of such wavelengths can be applied as an exposure light source for an exposure apparatus that exposes a photosensitive material which has sensitivity in a predetermined wavelength region including an ultraviolet region of 350 to 420 nm (hereinafter referred to as an ultraviolet region). The exposure light source in that case is required to have enough output to expose the photosensitive material.
The aforementioned excimer laser, however, has the problem that it is bulky and costly and has a high maintenance cost.
In addition, the aforementioned wavelength conversion laser, which converts infrared light to a third harmonic in an ultraviolet region, is very low in wavelength conversion efficiency, so it is extremely difficult to obtain high output. At present, a solid-state medium is excited with a semiconductor laser of 30 W to emit a 10-W fundamental wave of wavelength 1064 nm; the fundamental wave is converted to a 3-W second harmonic of wavelength 532 nm; and a 1-W third harmonic of wavelength 355 nm, which is the sum frequency between them, is obtained. The electro-optic efficiency of the semiconductor laser in that case is on the order of 50%, and the efficiency of converting infrared light to ultraviolet light is very low, typically on the order of 1.7%. Such a wavelength conversion laser is considerably costly because it employs an expensive wavelength conversion element.
Furthermore, the aforementioned Ar laser has the problem that the electro-optic efficiency is very low (0.005%) and the lifetime is very short (on the order of 1000 hours).
On the other hand, for the aforementioned GaN semiconductor laser, a GaN crystal substrate in a low dislocation region is not obtained. Because of this, a low dislocation region on the order of 5 &mgr;m is formed by a growth method (ELOG), and a laser region is formed on the low dislocation region to achieve high output and high reliability. However, even in the GaN semiconductor laser fabricated in this manner, it is difficult to obtain a low-dislocation substrate over a large area, and consequently, GaN semiconductor lasers with a high output of 500 mW to 1 W have not been put to practical use yet.
As another method for obtaining high-output semiconductor lasers, it is conceivable to obtain an output of 10W by forming 100 cavities which each have a light output of 100 mW. However, it is extremely difficult to produce such a great number of cavities in high throughput. Particularly, for GaN semiconductor lasers, in which a throughput of 99% or greater is difficult even in the case of a single cavity, it is still more difficult to produce a great number of cavities in high throughput.
SUMMARY OF THE INVENTION
The present invention has been made in view of the aforementioned circumstances. Accordingly, it is an object of the present invention to provide an inexpensive multiplex laser light source in which high output is obtained. Another object of the invention is to provide an exposure apparatus that is capable of exposing photosensitive materials with high-intensity laser light by employing the multiplex laser light source mentioned above.
To achieve the aforementioned objects of the present invention, there is provided a multiplex laser light source comprising:
a plurality of semiconductor lasers;
a single multi-mode optical fiber; and
a light-collecting optics system for collecting laser beams emitted from the plurality of semiconductor lasers and then coupling the collected laser beams to the multi-mode optical fiber.
In a preferred form of the present invention, the aforementioned plurality of semiconductor lasers are disposed so that their light-emitting points are arranged in a row in a first direction parallel to their active layers. The aforementioned light-collecting optics system comprises a plurality of collimator lenses, each having a first aperture diameter in the first direction and a second aperture diameter larger than the first aperture diameter in a second direction perpendicular to the first direction, and provided so that they correspond to the plurality of the semiconductor lasers. The light-collecting optics system further comprises a collective lens for collecting the plurality of laser beams collimated by the plurality of collimator lenses and then converging the collimated laser beams on an end face of the multi-mode optical fiber.
In another preferred form of the present invention, the aforementioned plurality of collimator lenses are formed integrally with one another and are constructed as a lens array. In addition, a block on which the aforementioned plurality of semiconductor lasers are mounted is divided into a plurality of subblocks, and the subblocks are bonded with one another.
In still another preferred form of the present invention, the aforementioned plurality of semiconductor lasers comprise 3 to 10 semiconductor lasers arranged in a row. It is further preferable that the plurality of semiconductor lasers comprise 6 or 7 semiconductor lasers arranged in a row. Each semiconductor laser has a light-emitting width of 1.5 to 5 &mgr;m, preferably 2 to 3 &mgr;m. It is desirable that the semiconductor lasers be GaN semiconductor lasers.
In the multiplex laser light source of the present invention, it is desirable that the aforementioned multi-mode optical fiber have a core diameter of 50 &mgr;m or less and a numerical aperture of 0.3 or less. It is further desirable that the value of (core diameter×numerical aperture) of the multi-mode optical fiber be 7.5 &mgr;m or less.
In the multiplex laser light source of the present invention, it is desirable that a plurality of semiconductor lasers be arrayed and fixed two-dimensionally when viewed from a side where the laser beams are received.
The multiplex laser light source of the present invention may employ only a single multi-mode optical fiber. However, it is desirable that the multiplex laser light source employ a plurality of multi-mode optical fibers. In this case, each of the plurality of multi-mode optical fibers may be combined with a plurality of semiconductor lasers and a light-collecting optics system so that a high-output laser beam is emitted from each multi-mode optical fiber. In such a case, it is desirable that at least the exit end portions of the multi-mode optical fibers be disposed in one-dimensional array form or bundle form.
In accordance with the present invention, there is provided an exposure apparatus having a light source. The light source comprises the aforementioned multiplexer laser light source in which a plurality of multi-mode optical fibers are disposed in one-dimensional array form or bundle form.
According to the multiplex laser light source of the present invention, laser beams emitted from a plurality of semiconductor lasers are collected and are then coupled to the multi-mode optical fiber. Thus, the multiplex laser light source of the present invention is extremely simple in construction. Particularly, since the multiplex laser light source does not require elements difficult to fabricate, it can be formed at low
Nagano Kazuhiko
Okazaki Yoji
Fuji Photo Film Co. , Ltd.
Hooly Brian
Wood Kevin S.
LandOfFree
Multiplex laser light source and exposure apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multiplex laser light source and exposure apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multiplex laser light source and exposure apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3258941