The invention relates to fibers, such as fiber lasers and fiber amplifiers, and systems containing such fibers.
Fibers, such as fiber lasers and fiber amplifiers, can be used to enhance absorption of pump energy. One type of fiber, commonly referred to as a double clad fiber, includes a core containing an active material, a first cladding around the core, and a second cladding around the first cladding.
The invention relates to fibers, such as fiber lasers and fiber amplifiers, and systems containing such fibers.
In one aspect, the invention generally features a fiber having a core, a first cladding around the core, and a second cladding around the first cladding. The outer perimeter of the first cladding has at least two substantially flat sides, and the outer perimeter of the second cladding is nonoval-shaped.
In another aspect, the invention generally features a fiber having a core, a first cladding around the core, and a second cladding around the first cladding. The core is formed of an active material. The first cladding has a lower index of refraction than the core. The outer perimeter of the first cladding has at least two substantially flat sides, and the outer perimeter of the second cladding is nonoval-shaped.
In a further aspect, the invention generally features a fiber having a core and a cladding around the core. The cladding has an outer perimeter including two substantially flat sides that are substantially nonperpendicular to each other. The lengths of the two substantially flat sides are different.
In yet a further aspect, the invention generally features a fiber having a core, a first cladding around the core, and a second cladding around the first cladding. The core is formed of an active material. The first cladding has a lower refractive index than the active material. The outer perimeter of the first cladding has two substantially flat sides that substantially nonperpendicular to each other. The lengths of the two substantially flat sides are different side.
In still a further aspect, the invention generally features a fiber having a core, a first cladding around the core, and a second cladding around the first cladding. The first cladding has an outer perimeter with at least two substantially flat sides. The core is substantially centrally disposed with respect to the geometric center of the outer perimeter of the second cladding, and the core is substantially eccentrically disposed with respect to the geometric center of the outer perimeter of the first cladding.
In another aspect, the invention features a fiber having a core, a first cladding around the core, and a second cladding around the first cladding. The core is formed of an active material, and the first cladding has a lower index of refraction than the core. The first cladding has an outer perimeter with at least two substantially flat sides. The core is substantially centrally disposed with respect to the geometric center the outer perimeter of the second cladding, and the core is substantially eccentrically disposed with respect to the geometric center outer perimeter of the first cladding.
In additional aspects, the invention generally features a system containing an energy source and one or more of the foregoing fibers. The energy source can be, for example, a laser. In certain embodiments, the energy source and fiber are arranged in an end pump configuration. In some embodiments, the energy source and fiber are arranged in a side pump configuration.
Embodiments of the above aspects of the invention can include one or more of the following features.
The core can be formed of an active material. The core can be formed of a rare earth ion doped material. The core can be formed of a silica material and at least one rare earth ion. The core can be a single mode core. The core can be a multi-mode core. The fiber can further include an additional material around which the core is disposed. The core can be ring-shaped.
The first cladding can be formed of a silica material.
The second cladding can be formed of a polymeric material.
The core can have a greater index of refraction than the first cladding. The first can have a greater index of refraction than the second cladding.
The outer perimeter of the second cladding can be nonoval shaped (e.g., substantially circular).
The two substantially flat sides can be substantially parallel. The angle between the first and second substantially flat sides can be, for example, from about 2xc2x0 to about 88xc2x0.
The two substantially flat sides can have the same lengths. The two substantially flat sides can have different lengths.
The core can be substantially centrally disposed with respect to the geometric center of the outer perimeter of the second cladding. The core can be substantially eccentrically disposed with respect to the geometric center of the outer perimeter of the first cladding. The core can be closer to a substantially flat side of the outer perimeter of the first cladding that is longer than at least one other (e.g., all other) substantially flat side(s) of the outer perimeter of the first cladding.
The fibers can be, for example, in the form of a fiber laser or a fiber amplifier. Generally, a fiber laser has a lasing cavity (e.g., a resonator) that is used to provide gain for energy at a desired wavelength. Typically, the gain in the cavity for energy at the wavelength of interest exceeds the loss from the cavity for energy at the wavelength of interest. Generally, a fiber amplifier provides gain for energy at a wavelength of interest without the use of a lasing cavity (e.g., without a resonator).
Features, objects and advantages of the invention are in the description, drawings and claims.