Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1998-11-30
2001-05-08
Bovernick, Rodney (Department: 2874)
Optical waveguides
With optical coupler
Input/output coupler
C385S031000, C372S006000, C257S098000
Reexamination Certificate
active
06229940
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to laser systems and, more particularly, to incoherent fiber optic laser systems.
BACKGROUND OF THE INVENTION
Lasers are presently employed for a wide variety of applications. For example, lasers are employed to process materials, such as by cutting, welding, heat treating, drilling, trimming and coating materials. Lasers are also employed to strip paint, remove coatings, clean surfaces and provide laser markings. Lasers can also be directly applied, such as via single mode optical fibers, for a variety of medical and other applications. Lasers are also increasingly employed in military applications, including laser weapon and laser ranging systems and sensor countermeasure systems. Laser communication systems have also been developed.
However, along with the ever-increasing number of applications in which lasers are used, the demands on the laser systems are also ever increasing. For example, a number of applications, including military and materials processing applications, are demanding lasers which emit increasingly higher power levels. In addition, a number of applications demand that the laser system produce an output beam which is of high quality, e.g., exhibiting predominantly or entirely fundamental or TEM
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mode characteristics. By being of high quality, the output beam can be more definitely focused to achieve higher brightness. As a result of the wide variety of applications in which lasers are used, the output beam may be required to be focused relatively near, such as within a few inches or a few feet as typically required by industrial applications such as cutting, machining, welding, drilling, paint stripping, or relatively far, such as at a distance of several kilometers as typically required in military applications such as laser weapon and sensor countermeasure systems.
Many laser systems have been developed to service one or more of the foregoing applications. For example, some conventional laser systems are scalable to produce an output beam having different power levels. Typically, these conventional laser systems rely upon the combination of various coherent laser beams in order to produce a coherent output beam with a high power level. Since these conventional laser systems produce a coherent output beam, these laser systems typically require sophisticated optical elements in order to properly combine and/or focus the coherent laser beams. See, for example, U.S. Pat. No. 5,694,408 to Eric H. Bott, et al, which issued on Dec. 2, 1997 and is assigned to McDonnell Douglas Corporation, the contents of which are incorporated in their entirety herein. As will be apparent, the cost of these laser systems is therefore disadvantageously large, at least for some applications, as a result of the costly optical elements. In addition, other conventional laser systems fail to produce an output beam that is of high quality and, as a result, may have difficulty focusing or otherwise shaping the output beam. Still further, other conventional laser systems which do not produce a coherent output beam suffer from other disadvantages, such as being incapable of being readily scaled to produce a wide range of output power levels or requiring the laser sources to be immediately adjacent to one another which limits the options available to the system designer.
While a variety of laser systems have been developed to service specific ones of the foregoing and other applications, a need still exists for a laser system which can service a wide variety of applications, such as by providing an output beam that is scalable to different power levels and that can be focused to a target location that is either relatively near or relatively far. In addition, a need also exists for a laser system that produces an output beam having high quality that can be focused or otherwise controlled without requiring sophisticated optical elements that would significantly increase the cost of the laser system.
SUMMARY OF THE INVENTION
According to the present invention, an incoherent fiber optic laser system is provided which provides a high quality output beam which is readily scalable and which can be focused to a target location located relatively near or relatively far without requiring sophisticated optical elements. The incoherent fiber optic laser system includes a plurality of single mode laser sources, such as a plurality of fiber optic amplifiers, for providing single mode laser signals. According to the present invention, the laser sources, such as the fiber optic amplifiers, operate incoherently with respect to one another such that the resulting laser signals are also incoherent. The incoherent fiber optic laser system also generally includes a plurality of single mode optical fibers for routing the incoherent laser signals as desired. In addition, the incoherent fiber optic laser system can include a plurality of lenses for collimating the incoherent laser signals provided by respective ones of the single mode optical fibers. In one advantageous embodiment, the incoherent fiber optic laser system also includes means for combining and focusing the collimated, incoherent laser signals to a target location at a predetermined distance. According to the present invention, the focusing means can focus the incoherent laser signals to a target location that is relatively near, such as within several inches, or to a target location that is relatively far, such as five or ten kilometers. Since the laser signals are incoherent, however, the fiber optic system need not include sophisticated optical elements, but can still produce a high quality output beam that is scalable to the wide range of power levels suitable for various applications.
Typically, the focusing means includes a focusing lens. However, the focusing means can include means for laterally positioning the single mode optical fibers with respect to the lens axis of the respective collimating lens. By appropriately positioning the optical fibers with respect to the respective lenses, the incoherent laser signals can be effectively steered, and, as a result, can be controllably focused at the target location, either with or without the assistance of a focusing lens.
In one advantageous embodiment, the plurality of single mode laser sources are a plurality of fiber optic amplifiers that are pumped by the pump signals emitted by respective ones of a plurality of pump sources. Alternatively, the plurality of single mode laser sources can include a plurality of single mode diode lasers. In other instances, the incoherent fiber optic laser system can operate in a pulsed mode, if so desired, in which the plurality of single mode laser sources are a plurality of pulsed laser sources which emit single mode laser pulses. Advantageously, the pulsed laser sources are synchronized such that the resulting laser pulses can deliver high power at the high pulse rates that are believed to be required of the laser sources for the next generation of x-ray lithography equipment.
In order to increase the power of the laser signals, the plurality of single mode laser sources can include a plurality of pairs of single mode laser sources with each pair of laser sources including first and second single mode laser sources. In this embodiment, the incoherent fiber optic laser system can also include a plurality of couplers. As such, each coupler can combine the single mode laser signals provided by the first and second laser sources of a respective pair of single mode laser sources in order to produce a laser signal having more power than the laser signals provided by either the first or second single mode laser sources taken individually.
By utilizing incoherent laser signals, the fiber optic laser system of the present invention can generate a scalable output beam having relatively high power levels that can be focused to a target location at a predetermined distance without requiring sophisticated and therefore expensive optical elements. In particular, the collimated, incoherent laser signals
Hollister Jack Herbert
Rice Robert Rex
Zediker Mark Steven
Alston & Bird LLP
Bovernick Rodney
Kang Juliana K.
McDonnell Douglas Corporation
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