Optical waveguides – Optical fiber waveguide with cladding – Utilizing multiple core or cladding
Reexamination Certificate
1999-05-27
2001-10-09
Lee, John D. (Department: 2874)
Optical waveguides
Optical fiber waveguide with cladding
Utilizing multiple core or cladding
C385S142000, C372S006000, C372S066000, C372S070000, C359S341430
Reexamination Certificate
active
06301421
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention generally relates to laser and amplifier systems and, more particularly, to laser and amplifier systems employing fiber optics.
2. Discussion
Lasers and amplifiers employing fiber optics are known to be very efficient. However, such systems are currently limited to low-output powers since conventional single mode fibers can only tolerate very small mode field diameters. As such, any attempt to increase the power through the fiber causes high intensity at the fiber output facet. This results in catastrophic damage.
Further, if an appropriate fiber was developed for tolerating such increased power, a high level of pump power would be required. To maintain the efficiency intrinsic with a fiber geometry, the pumped radiation must propagate along the fiber axis. However, conventional multi-mode high power pumps are difficult to focus on the small cross-section at the end facet of a fiber.
In view of the foregoing, it would be desirable to provide an efficient laser/amplifier fiber system capable of providing large mode field diameters, as well as a mechanism to couple the required pump power to the fiber.
SUMMARY OF THE INVENTION
The above and other objects are provided by a photonic crystal fiber for a laser/amplifier system including a guiding structure comprising a regular geometric (e.g. hexagonal) array of axial passages formed along the length of the fiber. More particularly, the guiding structure includes a central silica rod which is doped with a rare earth element for providing optical gain to the laser/amplifier. A plurality of second silica rods are disposed circumferentially about the central rod. Each of the second rods includes an axial passage formed therethrough along the length of the fiber. The first and second rods are then drawn down to a pre-selected diameter. This process transforms the first and second rods into a sintered cluster in the form of a geometric array. A reflective coating is deposited on an outboard surface of the array to confine pumped light therein. The pumped light may be injected into the fiber from the side by focusing it through small holes in the reflective coating or by reflecting it off transverse Bragg gratings written into a fiber pigtail coupled to the fiber. The mode field diameter of the fiber is controlled by properly selecting the diameter and spacing of the passages in the second rods.
REFERENCES:
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patent: 6058127 (2000-05-01), Joannopoulos et al.
patent: 6075915 (2000-06-01), Koops et al.
patent: 6097870 (2000-08-01), Ranka et al.
Properties of Photonic Crystal Fiber and the Effective Index Model; Knight, Birks, and Russell; University of Bath, Bath, UK and University of Southampton, Southampton, UK; Optical Society of America; vol. 15, No. 3, Mar. 1998, pp. 748-752.
Endlessly Single-Mode Photonic Crystal Fiber; Birks, Knight, and Russell; University of Bath, Bath, UK and University of Southampton , Southampton, UK, Optical Society of America; vol. 22, No. 13, Jul. 1, 1997, pp. 961-963,Optics Letters.
Brosnan Stephen J.
Holleman Gerald W.
Wickham Michael G.
Lee John D.
TRW Inc.
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