UV laser fabrication and modification of fiber Bragg gratings by stitching sub-gratings with in situ fluorescence monitoring.

We present a method for synthesizing complex fiber Bragg gratings using femtosecond UV laser pulses and image projection from a small phase mask. Fiber gratings with arbitrary spectral reflectivity can be achieved by stitching short grating segments with proper phases. The relative phase between neighboring sub-gratings is controlled using in situ UV-excited fluorescence monitoring. During the fabrication, we are able to monitor the amplitude and phase of each segment right after it was written. This is accomplished by scanning the phase mask with attenuated UV laser pulses and observing modulation in fluorescence. This information allows us to precisely set the position of fiber for the next segment. A fabricated grating segment can also be effectively erased with additional out-of-phase UV exposure. Bragg gratings over both telecom C-band and L-band can be conveniently achieved with this simple setup and a single phase mask.

Phase-sensitive amplification using gain saturation in a nonlinear Sagnac interferometer.

Phase-sensitive amplification of picosecond optical pulses was demonstrated using an SOA as the nonlinear medium inside a Sagnac interferometer. Ratios of maximum to minimum gain of more than 3:1 were experimentally measured. Numerical simulations using a semiconductor amplifier model are consistent with experiments.

Dispensed polymer waveguides and laser-fabricated couplers for optical interconnects on printed circuit boards.

Optical interconnects can provide chip-to-chip data communication with much needed bandwidth as processor speed and density keep growing. Optical waveguides and couplers are essential components for implementing optical interconnections. Techniques for directly dispensing polymer waveguides in laser-ablated trenches on printed circuit boards and for fabricating optical couplers are presented for quick prototype of optical interconnects. High-quality UV curable polymer waveguides were routinely fabricated. High-efficiency couplers, blazed grating couplers on sloped waveguides, sloped facet metal film couplers, and reflective-undercut facet couplers can be fabricated by using excimer laser ablation.