Abstract: A transverse closed-loop fiber resonator (10) includes an inner cladding (102) having a surface (300) peripherally forming a closed-loop shape for confining light to the surface (300). The inner cladding has a first diameter thickness (104) and a first index of refraction profile in a cross-sectional portion of the transverse closed-loop fiber resonator (10). A ringed-core (120) corresponding to the closed-loop shape is disposed on the corresponding surface of the inner cladding (102). The ringed-core (120) has a second thickness (124) of material thinner than the first diameter thickness (104), and a second index of refraction profile greater than the first index of the inner cladding by an index delta in the cross-sectional portion of the transverse closed-loop fiber resonator such that the ringed-core can guide light within the ringed-core traversely around the closed-loop shape.

Abstract: A fiber lens includes a multimode fiber and a refractive lens disposed at an end of the multimode fiber. The refractive lens focuses a beam from the multimode fiber into a diffraction-limited spot. In one embodiment, a graded-index is interposed between the multimode fiber and the refractive lens. In one embodiment, the combination of the graded-index and the refractive lens enables extreme anamorphic lens characteristics.

Abstract: Apparatus and methods for passively aligning optical elements are disclosed. In certain embodiments, the apparatus and methods include optical elements aligned on bases which are passively aligned and secured on a substrate by alignment features adapted to secure and passively align the bases.