Characterization of coated optical fibers by Fourier-domain optical coherence tomography.

Fourier-domain optical coherence tomography is used to image the cross sections of coated optical fibers. A standard single-mode fiber with a dual coating and a hard-clad silica fiber with a single thin low-index coating are studied. The individual coating dimensions, coated and uncoated fiber diameters, and the fiber coating's concentricity are retrieved from a single measurement.

Tilted superstructure fiber grating used as a Fourier-transform spectrometer.

We propose and demonstrate a new method for fabricating a compact all-fiber spectrometer by using a tilted superstructure fiber grating to couple light out of a fiber core and produce an interference pattern in the near field. The Fourier transform of the interference pattern serves as a direct measurement of the optical input spectrum, and the superstructure grating design offers several degrees of freedom that permit control over the resolution and bandwidth of the spectrometer. For single-wavelength operation, the proposed scheme offers the possibility of making wavelength measurements with picometer-level precision over a broad 80-nm wavelength range while simultaneously providing coarser precision over a 160-nm range.

Infrared photosensitivity in silica glasses exposed to femtosecond laser pulses.

We investigate the use of infrared femtosecond laser pulses to induce highly localized refractive-index changes in fused-silica glasses. We characterize the magnitude of the change as a function of exposure and measure index changes as large as 3x10(-3) and 5x10(-3) in pure fused silica and boron-doped silica, respectively. The potential of this technique for writing three-dimensional photonic structures in bulk glasses is demonstrated by the fabrication of a Y coupler within a sample of pure fused silica.

High-repetition-rate femtosecond optical parametric oscillator based on KNbO(3).

A Ti:sapphire-pumped, high-repetition-rate, femtosecond optical parametric oscillator based on potassium niobate is described. Signal pulses as short as 90 fs have been recorded, and idler pulses as short as 105 fs have been measured. Tuning from 1.2 to 1.4 microm in the signal branch and from 1.76 to 2.2 microm in the idler branch has been achieved. Output powers as high as 300 mW have been measured at the signal wavelength.