Abstract: A mode converter includes first and second optical waveguides and a GRIN fiber lens. The GRIN fiber lens is attached to both the first and the second waveguides.

Abstract: A GRIN fiber lens has a silica-glass core whose refractive index has a radial profile. The profile has a radial second derivative whose average magnitude in the core is less than about 1.7×10−6 microns−2 times the value of the refractive index on the axis of the GRIN fiber lens.

Abstract: A system monitors or images a portion of a sample. The system includes an optical interferometer with a measurement arm, a reference arm, and an optical splitter. The arms are coupled to receive light from the optical splitter. One of the arms includes an acousto-optical modulator. The interferometer is configured to interfere light output from the two arms. The system also includes a detector that receives the interfered light and uses the received light to determine a depth-dependent quantity characterizing a portion of the interior of the sample.

Abstract: An optical system for monitoring or imaging a sample includes a probe, an optical splitter or circulator, and an optical detector. The probe includes an optical fiber and a GRIN fiber-size lens fused to one end of the fiber. The optical splitter or circulator receives light from a source and directs a portion of the received light to the fiber. The optical detector is coupled to receive a portion of light collected from the sample by the GRIN fiber-size lens and is configured determine a characteristic of the sample from the received light.