Optical amplifiers and light source

An amplifying optical device comprising:

• a first waveguiding structure comprising a first core and cladding and configured to guide optical radiation;
• at least one pump source configured to supply optical pump power;
• an amplifying region situated in the cladding;
• and
• wherein the pump source is optically coupled to the amplifying region;
• and
• wherein in use the optical radiation guided in the first waveguiding structure overlaps the amplifying region;
• and
• further comprising an optical feedback device, and wherein the optical feedback device is configured to ensure that a portion of the optical radiation guided by the first waveguiding structure is amplified more than once by any one section of the amplifying region.

A method of pumping at least one optical fiber amplifier with a fiber laser, the method comprising:

• providing a first waveguiding structure fabricated from at least one glass system and comprising a first core and cladding;
• providing a second waveguiding structure comprising a second core at least partly formed by the cladding and an amplifying region comprising Ytterbium;
• providing a source of optical pump power in optical communication with the second waveguiding structure and having a wavelength in the band from about 870 nm to about 950 nm;
• providing an optical feedback device;
• guiding optical radiation using the first waveguiding structure;
• guiding the optical pump power using the second waveguiding structure such that the amplifying region interacts with the optical radiation guided in the first waveguiding structure and the optical pump power guided in the second waveguiding structure to amplify the optical radiation guided by the first waveguiding structure;
• using the optical feedback device to ensure that a plurality of times a portion of the optical radiation guided by the first waveguiding structure is amplified more than once by the amplifying region;
• providing an amplifying region characterized by a dopant concentration, a disposition and a length, and wherein the dopant concentration, the disposition and the length of the amplifying region are arranged such that the fiber laser emits optical radiation at an emission wavelength in the region of about 970 nm to about 990 nm;
• and
• coupling the optical radiation at the emission wavelength in the region of about 970 nm to 990 nm into the at least one optical amplifier.

A method of amplifying optical pulses to energies exceeding the intrinsic saturation energy of an amplifying optical device, comprising:

• providing a first waveguiding structure comprising a first core and cladding;
• providing a source of optical pump power;
• providing a second waveguiding structure comprising a second core at least partly formed by at least part of the cladding, and an amplifying region;
• guiding optical radiation using the first waveguiding structure;
• and
• guiding the optical pump power using the second waveguiding structure such that the amplifying region interacts with the optical radiation guided in the first waveguiding structure and the optical pump power guided in the second waveguiding structure.

An amplifying optical device comprising:

• a first waveguiding structure configured to guide optical radiation which can propagate in a fundamental mode;
• a pump source configured to supply optical pump power;
• a second waveguiding structure configured to guide the optical pump power, and
• wherein:
• the pump source is optically coupled to the second waveguiding structure;
• in use the optical radiation is characterized by an optical power distribution of the fundamental mode having a contour of equal intensity perpendicular to the local longitudinal axis of the first waveguiding structure the contour enclosing about 75% of the optical power of the fundamental mode;
• the second waveguiding structure contains an amplifying region situated to interact with the optical pump power guided in the second waveguiding structure when the amplifying optical device is in use;
• the amplifying region is situated to lie outside the contour of equal intensity;
• and
• during use at least 0.1% of the optical radiation guided by the first waveguiding structure overlaps the amplifying region.