A polarization controller comprising: (i) an optical fiber, and (ii) a carrier surrounding the optical fiber, the carrier comprising an off-center through hole with at least one collapsed region, such that the optical fiber is situated within the through hole and contacts the at least one collapsed region of the through hole, and the collapsed region exerts pressure on the optical fiber.

Rare earth doped fiber lasers can be robust and efficient sources of high quality light, but are usually limited to the highest gain transitions of the active species. But rare earths typically possess a multitude of potentially useful transitions that might be accessed if the dominant transition can be suppressed. In fiber lasers this suppression is complicated by the very high net gain the dominant transitions exhibit; effective suppression requires some mechanism distributed along the length of the fiber. We have developed a novel waveguide with resonant leakage elements that frustrate guidance at well-defined and selectable wavelengths. Based on this waveguide, we have fabricated a Large Mode Area Neodymium doped fiber with suppression of the four-level transition around 1060 nm, and demonstrated lasing on the three-level transition at 930 nm with good efficiency.

An Nd.sup.3+ optical fiber laser and amplifier operating in the wavelength range from 1300 to 1450 nm is described. The fiber includes a rare earth doped optical amplifier or laser operating within this wavelength band is based upon an optical fiber that guides light in this wavelength band. The waveguide structure attenuates light in the wavelength range from 850 nm to 950 nm and from 1050 nm to 1150 nm.

An all solid hybrid waveguiding structure provides large mode area, acceptable losses of the desired core mode and very high losses of the undesired next higher order mode in the core. Embodiments of the waveguide include a hybrid of low index barriers providing confinement by total internal reflection, and further include high index rings that support guided modes only at effective indices different from that of the desired core mode.

A polarization controller comprising: (i) an optical fiber, and (ii) a carrier surrounding the optical fiber, the carrier comprising an off-center through hole with at least one collapsed region, such that the optical fiber is situated within the through hole and contacts the at least one collapsed region of the through hole, and the collapsed region exerts pressure on the optical fiber.

A polarization controller comprising: (i) an optical fiber, and (ii) a carrier surrounding the optical fiber, the carrier comprising an off-center through hole with at least one collapsed region, such that the optical fiber is situated within the through hole and contacts the at least one collapsed region of the through hole, and the collapsed region exerts pressure on the optical fiber.

An all solid hybrid waveguiding structure provides large mode area, acceptable losses of the desired core mode and very high losses of the undesired next higher order mode in the core. Embodiments of the waveguide include a hybrid of low index barriers providing confinement by total internal reflection, and further include high index rings that support guided modes only at effective indices different from that of the desired core mode.

Optical coupling techniques between an optical fiber and another optical device, such as a planar optical waveguide, or a probed region are disclosed. An optical fiber for lateral optical coupling includes a cladding, a core disposed in the cladding, a reflecting structure inclined relative to the fiber axis, and a light-converging structure embedded in the cladding. The reflecting structure is configured to reflect light between the core and a lateral coupling path extending and providing lateral optical coupling between the core and an exterior of the fiber. The cladding-embedded light-converging structure is configured to intercept and converge light traveling along the lateral coupling path. In some implementations, the optical fiber is a fiber-optic transition coupled between a main optical fiber and another optical device or a probed region. A coupled optical system including an optical fiber coupled to another optical device is also disclosed.

In a multicore optical fiber sensor, an absorptive material integrated into the cladding, or into a waveguide core not used for sensing, may facilitate sensing. The absorptive material is absorptive to light in a wavelength band in which the fiber sensor is configured to operate. Coating such a fiber sensor with a material whose refractive index is smaller than that of the cladding may be done with reduced signal mixing.

Optical coupling techniques between an optical fiber and another optical device, such as a planar optical waveguide, or a probed region are disclosed. An optical fiber for lateral optical coupling includes a cladding, a core disposed in the cladding, a reflecting structure inclined relative to the fiber axis, and a light-converging structure embedded in the cladding. The reflecting structure is configured to reflect light between the core and a lateral coupling path extending and providing lateral optical coupling between the core and an exterior of the fiber. The cladding-embedded light-converging structure is configured to intercept and converge light traveling along the lateral coupling path. In some implementations, the optical fiber is a fiber-optic transition coupled between a main optical fiber and another optical device or a probed region. A coupled optical system including an optical fiber coupled to another optical device is also disclosed.